2015 Astronomical Calendar

Astronomical Calendar 2015 Deneb

Vega

Capella Arcturus Altair Castor Aldebaran

Regulus

Pollux Sun

Rigilkent

Procyon

Fomalhaut

Spica

Antares

Sirius

Betelgeuse

Hadar Achernar

Canopus Mimosa

Acrux

Rigel

Adhara

Stellated stars

Deneb

CONTENTS 2

4

INTRODUCTION WHERE? HIGHLIGHTS OF THE TIME ZONES BLOCK CALENDAR ALL-YEAR CHART ALL-SKY CHART

YEAR?

6 8 10 12 14 16 18 20 22 24 26 28

JANUARY FEBRUARY MARCH APRIL MAY JUNE JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER

30 32 34 35 37 38 40 42 44 45 46 48 50 51 52 54 58 60 63 68 72 73 74

Stellated Stars. Before we discovered that stars are huge globes of hot matter, we saw them as points of light with spiky rays sticking out. All stars except the Sun are so far away that they would appear as points only, with essentially no radius, but the optics of the eye— and of cameras—spreads the light of the brighter points and adds these shimmering spikes. That is why stars are conventionally drawn as little shapes with radiating spikes.

And that is why geometric shapes with triangles sticking out of them are called stellated, “starred.” And if the symbol is merely made of radiating lines instead of triangles, it is an asterisk, “little star.”

(Merriam-Webster’s website, after briefly defining stellated, adds: “This word doesn’t usually appear in our free dictionary, but the definition from our premium Unabridged Dictionary is offered here on a limited basis. To access the complete Unabridged Dictionary, with an additional 300,000 words, start a free trial . . .” “What,” comments Larry Bohlayer, who told me about this, “they will take away our word? May we no longer use it once the free trial period is over?” Well, we will use it.)

Here is a row of polygons (many-sided two-dimensional figures—Greek polys, “much” or “many,” and gônia, “corner” or “angle”):

SCENES SUN, EARTH, AND SEASONS COVER PICTURE, CONTINUED MOON SPECIAL MOONS YOUNG MOON, OLD MOON MERCURY; VENUS MERCURY AND VENUS HORIZON MARS OUTER PLANETS JUPITER SATURN URANUS AND NEPTUNE PLUTO ASTEROIDS COMETS OCCULTATIONS METEORS ECLIPSES ZODIAC CHARTS MAGNITUDE GRAPH ELONGATION GRAPH GLOSSARY RISING AND SETTING

COVER PICTURE:

They are the triangle, quadrangle, pentagon, hexagon, heptagon, octagon (first two names Latin-derived, the others Greek). Actually these are just the special cases of them that have equal sides and angles, the first two being the equilateral triangle and the square. And here they are stellated:

The stellations, if that is what they are called—the triangles added to each face—can have any height, or they could even cut inward; I’ve just chosen a radius from the center to the tips that is twice that of the radius to the central polygons’ corners.

You can see what happens if, instead, this distance is chosen carefully so that the stellation’s sides are in line with the inner polygon’s sides. (This is impossible with,

SCENES

only, the triangle and square—the lines would run to infinity,) The stellated hexagon (“Star of David”) could be drawn as two triangles superimposed. The stellated pentagon (pentagram, a symbol of life, reminiscent of a human being, with head and four limbs), and the 7- and 8pointed shapes, could be drawn continuously with strokes that cross over each other in running to non-adjacent tips.

Polygons tend to become heavy with symbolism. I’ve noticed that some police badges are, for some reason, a nonagon (9-pointed, should be enneagon) with not-quitecontinuous short stellations.

And then, polyhedrons, or, if you prefer, polyhedra.

They are many-faced three-dimensional figures. When the Greeks came to talk about geometrical solids, the term they chose for what we call a “face” was hedra, “seat.” (In Continued on page 34

ASTRONOMICAL CALENDAR 2015 by Guy Ottewell

Universal Workshop

w w w.Un iversa lWorkshop.com Raynham, Mass., and Lyme Regis, England

Sponsored by The Department of Physics, Furman University, Greenville, South Carolina

The Astronomical League 9201 Ward Parkway, Suite 100, Kansas City, MO 64114 816-DEEP-SKY www.astroleague.org

2

Astronomical Calendar 2015 Preface Astronomical Calendar 2015 retains some of the added features of the 2014 issue, while returning to the general layout of previous years. Some readers enjoyed having the material for a month collected in one place, others were disconcerted at not finding things where they were accustomed to finding them. Astronomy is multi-dimensional.

I am again heartily grateful to John Goss, now President of the Astronomical League, for proofreading all parts of the book that I was able to send to him in time. He saved me from many typos and unclarities. And I am grateful to several readers who sent corrections and suggestions.

Alan Hale suggested the comets to be included, and answered my questions about them. The “Meteors” section is founded on the extensive information provided to me by Alastair McBeath.

I’ve been persuaded to start a weblog. I began it with an outburst about the “Multiverse,” and it continues in what may be a wayward manner, with pieces varied rather like the cover-picture essays of this Astronomical Calendar and not all about astronomy. You might consider visiting it, and if you sign up to it we will stay in touch even if the Astronomical Calendar at last ceases: www.universalworkshop.com/guysblog

Copyright © 2014 by Guy Ottewell. Printed in the United States of America. All rights reserved. Parts may be reproduced with prior permission and with acknowledgment.

ISBN 978-0-934546-70-6

ISSN 1051-6174

The first small issue of this annual book was for the year 1974.

h Eart

Oct

e m

y lle a tH

Co

May

The path of Halley’s Comet, with sightlines from Earth to Comet during the first four months of 1986

Some other publications by Guy Ottewell:

The Astronomical Companion General guide to astronomy (not annual), with many 3-D diagrams

Albedo to Zodiac Glossary of astronomical terms, with pronunciation, origin, meaning

To Know the Stars Young people’s introduction to astronomy. NEW EDITION 2014

The Thousand-Yard Model, or, The Earth as a Peppercorn Instructions for a walk making vivid the scale of the solar system

The Under-Standing of Eclipses The geometry, history, and beauty of eclipses

Berenice’s Hair Story of the stolen tress that became the constellation Coma Berenices.

More information at

www.UniversalWorkshop.com

Corrigenda to Astronomical Calendar 2014 Page 30, section “Earth and Sun in June”: what occurs on June 14 is the earliest sunrise, not earliest sunset. This is correct in the “June Events” table on the facing page.

72, middle column, paragraph 2: the Earth globes during occultations were oriented, this time, with celestial north at the top, not ecliptic north.

74, column 2, under the heading: delete “The Moon’s varying distance.”

85, in the glossary entry for “obliquity”: “98° for Saturn” should be “98° for Uranus.

The Troy Town Tale The whole legend of Troy, in the form of a novel

Portrait of a Million Poster conveying the concept of a million, with million-facts

American Indian Map, and Navajo Map The Arithmetic of Voting Language (poems) Plurry: a musical instrument The Spiral Library Stripe Latin: a grammar game Ten-Minute History of the World; and, Queen Guinevere’s Rules Think Like a Mother: a photo book of human rights Turkey, A Very Short History The Winged Velocipede; or, how to f ly overseas with your bicycle

Astronomical Calendar 20145

INTRODUCTION If you are a relative beginner, it may be best to use at first only the “Sky Dome” map for the current month (page 6, for instance, if it’s January).

The map is indeed of a dome: it’s center is the zenith (straight overhead), the outer circle is the horizon. It’s best as a general rule to have your face (or feet, if you’re lying on your back or on a long chair) to the south. This avoids confusion. If at times you want to face, say, east, rotate the map so that “East” is at the bottom.

If you locate and memorize a few constellations each month, in a year you’ll know the sky pretty well.

The table on the month’s right-hand page contains brief entries for many kinds of astronomical events.

The times given in parentheses are in Universal Time; TIME ZONES, below, explains how to translate this into your clock time.

If the event concerns, say, Jupiter, or a meteor

shower, there will be more information in the JUPITER or section later in the book.

Astronomical terms, such as opposition, ecliptic, latitude, retrograde, inferior conjunction, precession, are explained in the GLOSSARY. Events of the type of “Mars 4.6° N.N.E. of Spica” are conjunctions, or, more exactly, appulses: moments when two bodies appear closest to each other from our viewpoint.

For many events, such as the opposition of a planet or the conjunction of two bodies, the exact time may be when the bodies are below your horizon, but they will not have moved much a few hours earlier or later.

Events most affected by the more exact time and your position on Earth are the peaks of meteor showers, and, especially, eclipses and occultations.

The ELONGATION graph, when you get used to it, and even more richly the ZODIAC CHARTS, allow you to survey the movements of the solar-system bodies in relation to each other throughout the year.

BLOCK CALENDAR

METEORS

Julian Date at 1.0 UT of month 2457023.5

Jan

ry

ua

2457054.5

ar y

ru Feb

2457082.5

rch Ma 2457113.5

Ap

WHERE? What parts of the book are true for what parts of the Earth?

When it makes a difference, we refer usually to what can be seen from around latitude 40° north (the U.S.A. and Europe). “Around” means that for most purposes a few degrees north or south don’t make much difference.

The standard longitude is 0° (Greenwich), but often we refer to what can be seen from eastern North America (around 75° west). All this is “unless otherwise mentioned.”

Longitude (such as whether you’re in California or Europe) makes no difference to the positions of the stars at, say, 10 PM, very little to the planets; only the rapidly moving Moon is much affected. It will be about 2° farther along its course for each time zone you move westward.

Latitude makes more difference: as you go south, different stars come into view, and for the southern hemisphere the sky is considerably different. The large Sky Domes in the monthly pages are for mid-evening at latitude 40° north; smaller Domes show the difference at 50° north, the equator, and 35° south.

TIME ZONES Times are mostly given in Universal Time (UT), which is the time at longitude 0° (Greenwich Observatory in England).

To convert UT to the clock time of a time zone, use this map of the zones. For standard time, add the number (if it is negative, subtract it). Then for so-called daylight-saving (summer) time, where used, add 1. If the result is negative, add 24; the date is then in the previous calendar day. If the result is over 24, subtract 24; the date is in the next day.

For example, UT 0 is these times in America on the previous calendar day: Hawaii 14, Alaska 15, Pacific 16, Mountain 17, Central 18, Eastern 19 Standard Time Hawaii 15, Alaska 16, Pacific 17, Mountain 18, Central 19, Eastern 20 summer Time

ril

2457143.5

y Ma

2457174.5

Jun

e

2457204.5

y

Jul

HIGHLIGHTS OF THE YEAR (See the calendar pages at the dates, and the SECTIONS emphasized.)

• Jan: COMET C/2014 Q2 Lovejoy possibly almost at naked-eye brightness.

• Feb 8: JUPITER at opposition.

• Feb-Mar: clustering of Venus, Mars, Uranus, and the Moon in the evening sky; see SCENES. • Mar 20: total ECLIPSE of the Sun, visible from Faroe, Spitsbergen, and the North Pole!

• Apr 4: total ECLIPSE of the Moon, visible from the Pacific region.

• May 7: MERCURY highest in evening sky for north-hemisphere observers.

• May 23: SATURN at opposition.

• May-Jun: VENUS highest in the evening sky.

• Jul 6: COMET C/2014 Q1 PanSTARRS at perihelion, possibly at naked-eye brightness.

• Jul-Aug: clustering of Venus, Jupiter, Mercury, and Regulus, and the Moon in the evening sky; see SCENES. • Aug: COMET 141P Machholz 2 at perihelion, perhaps magnitude 11.

• Sep 13: partial ECLIPSE of the Sun, visible from southern Africa and Antarctica.

• Sep 28: total ECLIPSE of the Moon, visible from the Americas, Africa, Europe, much of Asia.

• Sep-Oct: clustering of Venus, Mars, Jupiter, Regulus and the Moon in the morning sky; see SCENES. • Oct: COMET 22P Kopff at perihelion, perhaps magnitude 10.

• Oct: VENUS highest in the morning sky.

• Dec: COMET C/2013 US10 Catalina possibly reaching naked-eye brightness.

3

2457235.5

ust

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2457266.5

er

mb pte

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2457296.5

to Oc

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2457327.5

er mb e v No 2457357.5

er mb e c De 2457388.5

2015 Sun Mon Tue Wed Thu 1 4 5 6 7 8 11 12 13 14 15 18 19 20 21 22 25 26 27 28 29 1 2 3 4 5 8 9 10 11 12 15 16 17 18 19 22 23 24 25 26 1 2 3 4 5 8 9 10 11 12 15 16 17 18 19 22 23 24 25 26 29 30 31 1 2 5 6 7 8 9 12 13 14 15 16 19 20 21 22 23 26 27 28 29 30 3 4 5 6 7 10 11 12 13 14 17 18 19 20 21 24 25 26 27 28 31 1 2 3 4 7 8 9 10 11 14 15 16 17 18 21 22 23 24 25 28 29 30 1 2 5 6 7 8 9 12 13 14 15 16 19 20 21 22 23 26 27 28 29 30 2 3 4 5 6 9 10 11 12 13 16 17 18 19 20 23 24 25 26 27 30 31 1 2 3 6 7 8 9 10 13 14 15 16 17 20 21 22 23 24 27 28 29 30 1 4 5 6 7 8 11 12 13 14 15 18 19 20 21 22 25 26 27 28 29 1 2 3 4 5 8 9 10 11 12 15 16 17 18 19 22 23 24 25 26 29 30 1 2 3 6 7 8 9 10 13 14 15 16 17 20 21 22 23 24 27 28 29 30 31

Fri 2 9 16 23 30 6 13 20 27 6 13 20 27 3 10 17 24 1 8 15 22 29 5 12 19 26 3 10 17 24 31 7 14 21 28 4 11 18 25 2 9 16 23 30 6 13 20 27 4 11 18 25 1

Sat 3 10 17 24 31 7 14 21 28 7 14 21 28 4 11 18 25 2 9 16 23 30 6 13 20 27 4 11 18 25 1 8 15 22 29 5 12 19 26 3 10 17 24 31 7 14 21 28 5 12 19 26

Darker blue means less moonlight in the following night.

4

Astronomical Calendar 2015

24h

23h

22h

21h

20h

18h

19h

17h

16h

15h

14h

12h

13h

+10˚

+10˚

Altair PISCES 0˚

VIRGO

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b

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-10˚

M Janars

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Feb

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Pluto

v No

-20˚

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Dec

Antares Fomalhaut -30˚

SCORPIUS

SAGITTARIUS

-30˚

Coordinates of 2000

OM ED A

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φ

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λ

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θ

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τ

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Coordinates of 2000

ε γ

α

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β -- 8

galaxy

G

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globular cluster

F

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κ

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planetary nebula

B

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nebula

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open cluster

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α β

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Saturn Nebula

τ

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ν

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18 18

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η M13

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α

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19 19 hh

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2200 η

θ

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ω

δ

ρ

α ++ 10 10 oo

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τ δ

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µ

h h

h h

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ζ

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γ

β

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α

h h

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π

α

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h h

β

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0

2233

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θ

β

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λ κ

o o

δ γ

ε

s pe c t r a l

0--0

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PISCES

l et t he C i r c h h

γ

ζ

ε Vega δ ζ α κ γ β Ring

η

β

Dumbbell

-6

ξ

θ

VULPECU LA

DELPHINUS

++ 1100 oo

θ

γ

Albireo

κ

β ab k

Ko

LYRA

β

o o

r

ι

δ

Sadr

-- 88 00 oo

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t S qua

ν

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++6600 oo ξ Kuma ν Arrakis µ β Eltanin γ ++5500 oo

ι

θ

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π

η

α

ι

Deneb α

ζ η

north ecliptic pole

κ

ξ

σ τ

Markab

ω

ρ

ε

o f

oon

ALL THE YEAR

B D i g i p

o o

++ 2 0 0

π

o o

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η θ

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φ ++7700 oo

δ

π

D

χ

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0

min

W

ea

µ

σ

ρ

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ν α

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ψ Gr

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ε ζ

τ

ε

i

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κ

0 40 ++4

LAC ERT C A oc

ο

Ald

δ

β

β

α

ι

HE U

CAM PARDEALLOIS

tt le

ε ++ 88 00 oo

κ S

ξ

IA PE SIO

S

CA

CE P

L

++8800 γ

δ

ε α

β

-3

0

oo

5

Astronomical Calendar 2015

12h

11h

10h

9h

6h

8h Castor 7h GEMINI Pollux

+30˚

5h

+20˚

Aug LEO

Apr

r

t Ocg Au

Oct

Aug

Mi l k y

Jul

Sep

Procyon

ARIES

May Jun

Wa

CANCER

s

0h

1h

Pleiades

May

Aldebaran

y

SepJu

2h

Jun

Jul

e pit

Regu lu +10˚

Jul

i c i p t ec l

3h

+30˚

May

Jun

4h

+20˚

Ap r

TAURUS

Ve M nu M A ar s e r pr cu ry

Betelgeuse

PISCES +10˚

Ur an M us a r Ma s r

0˚

0˚

Mira Rigel

ξ

SA JO R

λ

of

t he

23

++ 77 0

o o

US

α

Musc ida

ο

ε

δ LYNX

λ

++5500 oo

Capella α Maaz ε Menkalinan ζ o o η ++4400 ν τ θ A π β

α

η

γ

AURIG

µυ

ν

ε

β

φ

β

Algol

AN

µ

ak Alm

π ρ

γ

θ

++

ν

υ

γ

β

σ

π

β

oo

lta De ++3300 α ah δ ε Sirr

ach Mir

M GULU TRIAN α

ξ

California

da

me xy oo A ED ndro ala 00 M G 4 A O

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θ κ

EUS PERS

00 55 ++ ο

φ

ι

σ

ψ

oo

ζ

τ

k Mirfaα

δ

ed Sh

θ

ub Doster Clu

IS

β

αr i

η

ah kb Ru le

PARDAL CAMELO

++6600 oo

δ

γ Tsih

h

SS CA

Ca p

ι

θ

LEO MIN OR

IO

++7700 oo

τ

κ ι

PE

κ

γ

φ

e el l Ga z

IA

2

β

ο

HE

o o

o o

s

o o

0

Leap

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UR

M8 1

r

++ 88 00 oo

M8

υ

la

+3

ν

e

k

µ

p

he ub D α

oo

00 ++66

oo

0 40 ++4

ψ

p

β r a bu e e 8 M wl n O

d

MA

++8800

g

γ

10 M

a P h 09 M1 00oo ++55 χ

Maps of the whole celestial sphere. Stars are colored by spectral type.

i

CO

++7700 λ

i

D

RA

B

D

Maps of the planets’ movements throughout the year. All the major planets keep to the zodiacal band, not departing more than 8½° from the ecliptic.

Declination (vertical) scale is exaggerated by 1.5.

α aris l Po

++ 8800 oo

-10˚

Coordinates of 2000

CE P

-10˚

M33 τ

M

i

l

k

y

W

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β

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Coordinates of 2000

γ

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all Smlanic l ge oud Ma Cl

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galaxy

G

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S RU

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globular cluster

44

Astronomical Calendar 2015

A

VIR

GO

ecliptic latitude

+10˚ + 5˚

Dec

0˚ -5˚

+1

14

Spic

h

0

165˚ o

LEO

Nov -1

0

Venus

-15˚

11

Sep Reg ulus

10

h

105˚

Pollux

Aug

es

n

6h

ES ARI Mercury Apr 22

Ma Me y 2 rcu 7 ry

Apr

Hyades S TAURU

4h

5h

3

h

2 Mira

Coordinates of 2015

Proc yon Betelgeuse MAP of Mars’s geocentric track against the starry background, ecliptic-based like the Mercury and Venus maps. The scale for this year is 11 3 mm to 1°. The track is drawn in gray when Mars is in the morning sky (after conjunction with the Sun). Parts of the tracks for the neighboring years are included (in blue). Short blue lines connect Mars to other planets when they appear closest.

e s ma gn i t ud

¤

MARS

ER

NI

Jul

pt i c ecl i

May

Sep northernmost latitude Oct O

Nov aphelion

eq

ua

t

Jan

or

ar 3 2012 M

Mar

Ea

Apr

P

elo 41 38 36 29 29 24 17 14 5 -1 -1 -3 -9 -39 -40 -47 -52 -53 -71

mag dia” 1.1 4.8 1.1 4.6 1.2 4.6 1.3 4.2 1.3 4.2 1.3 4.1 1.4 3.9 1.4 3.8 1.5 3.7 1.5 3.6 1.5 3.6 1.6 3.6 1.6 3.6 1.8 4.0 1.7 4.1 1.7 4.3 1.6 4.5 1.6 4.6 1.3 5.6

mean dist. from sun 1.52 a.u. sidereal period 1.88 years = 687 days synodic period 2.13 years = 780 days eccentricity .093 inclination 1.9° diameter 6,790 km satellites 2

N LA

E

A QU

AR

IU S

Aug

20 Jul 1287 Jul

CA P

RI C ORN

Jun

May

q ro t au

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6 201 22 Ma y

n io 8 sit Apr o p 4 op 01 2

C TI P LI EC

rt h

section.

gedis 1.970 2.015 2.056 2.203 2.204 2.281 2.404 2.442 2.537 2.568 2.573 2.581 2.586 2.318 2.296 2.184 2.073 2.053 1.684

S P I S CE

ES

Sun

Feb

--3

US

Dec

2010 Ja n 29

VENUS

--2

telescope, you’ll see more of its southern hemisphere, its equator being lifted northward.

By contrast, if toward the year’s end you study Mars climbing and modestly swelling in the pre-dawn sky, you’ll glimpse its northern polar icecap.

But the icecaps do not mirror each other. Earth’s perihelion and aphelion each January and July have almost negligible climatic effect, but Mars’s much more widely varying distance from the Sun strongly affects its seasons—it receives 45% more solar energy when nearest than when farthest. Martian winter solstice (Jan. 11) is only a month after its perihelion (2014 Dec. 12). The south hemisphere, bulging toward the relatively near Sun, has, for Mars, a hot summer; the southern icecap may disappear altogether.

The north hemisphere, tipped away, has a relatively mild winter. In contrasting years of southern winter and northern summer, the southern icecap may become larger than the northern ever does. Thus the result of the asymmetric orbit is moderate seasons for the north hemisphere and extreme ones for the south.

Mar m e a n d i st 2005 Feb a n c e Nov 7 rn Jan northineter w stice l Oct so 03 20 Sep Aug 28

Nov

Dec

and

hedis 1.384 1.388 1.392 1.416 1.416 1.434 1.471 1.485 1.530 1.553 1.557 1.568 1.590 1.659 1.660 1.665 1.666 1.666 1.658

--1

al v er n di

Apr

Ma r s

De 200 c2 7 4

Aug

AR I

R US T AU

winter solstice .2ºS of Neptune on equat.,to nor. .5ºN of Venus .3ºN of Uranus ascending node 1.4ºS of Mercury 1.7ºN of Mercury conjunc.with sun spring equinox max.declin.north .1ºN of Mercury max.lat.north .4ºN of Jupiter .7ºN of Venus on equat.,to sou. aphelion

MERCURY

r.a.(2000)dec.

21 34 28 -15 36 22 4 39 -12 54 22 31 9 -10 18 0 5 0 0 -4 0 5 17 0 -2 0 55 31 5 33 2 23 44 14 16 2 55 24 16 50 4 36 4 22 30 5 29 47 23 53 5 39 47 24 0 6 5 44 24 9 7 2 12 23 32 10 53 42 8 29 11 2 13 7 37 11 40 60 3 34 12 13 38 0 5 12 19 14 0-30 13 47 28 -9 28

0

r e eq c t ui n i o ox n

al

ecliptic north pole

ion rotat Earthorth pole n

MI GE

Su n sp -co rin nj g e un qu ctio i no n x

0 23 21 17 20 20 6 7 15 16 1 19 4 21 14 16 10 23 0

Ma r nors rotat th p ion ole al

Mars alternates between “good” years (when it comes to opposition) and bad ones— approximately.

This fourth planet lies 1½ times farther out from the Sun than Earth, taking 1.88 of our years to complete an orbit. On our faster inside track, we take 2.13 years to catch up with Mars and pass it at the next opposition. The result of this is that the oppositions are spaced around the sky, slightly less than 1/7 of the circle apart, in a slightly-more-than15-year cycle.

In an opposition year, Mars makes an apparent retrograde loop as we overtake it; last year it did so in Virgo. In a non-opposition year like the present, it travels a semicircle that keeps it roughly on the other side of the Sun from us. Thus it appears to move almost in company with the Sun, only slowly overtaken by it, so on the map of the sky it traces a long straight inconspicuous track through eight of the twelve zodiacal constellations.

This semicircle is approximately the northern half of its orbit (it is in the northern celestial hemisphere from Feb. 21 till Nov. 18—and is slightly further north still because above the ecliptic from April 12 onward). But this northerliness is wasted, since Mars is behind the Sun almost exactly at the middle of the arching path (Sun-conjunction June 14, northernmost declination June 26). Even in years when oppositions fall in the northerly part of the orbit they are not the best, since it is also very roughly the outer part of the orbit (aphelion Nov. 20).

Earth and Mars are curiously similar in rotation: they spin in 24 and 24½ hours, respectively, around polar axes that are tilted 23.44° and 25° to the planes in which they travel. Moreover the four cardinal points caused by the tilting, which we call the equinoxes and solstices, are distributed in almost the same four directions around the orbits— but with a right-angle difference: the winter solstice of Mars is in the same direction from the Sun as the spring equinox of Earth. The two planets are like a man leaning north and a man leaning east as they walk around in circles (try it but don’t lose your balance!).

If in the low western sky of the early months you manage to get dwindling Mars in your

CA N C

5 4 3 2 1

TABLE OF PHENOMENA. For explanation see the Mars Jan 1 Jan 10 Jan 19 Feb 21 Feb 21 Mar 11 Apr 12 Apr 23 May 27 Jun 14 Jun 18 Jun 26 Jul 16 Oct 13 Oct 17 Nov 3 Nov 18 Nov 20 Jan 1

A non-opposition year, in which Mars is distant and small. It starts low in the sunset sky, disappears beyond the Sun from about April till August, climbs to quite high in the morning sky by December.

E

30˚

Mars

May

Aldebara

7h

45˚

Pleiad

GEMINI

8h

60˚

Sun-conjunction Jun 14

Mercury

p2 s Se nu

Ve

75˚

Jun

Jul 16

ive

9h

M35

Jul

Beeh

h

90˚

Castor

CER

eq ua tor h

120˚

+30 o CAN

Jupiter

o

12

h

135˚

o

Oct

-10˚

13

0

Oct 17

Nov 3

ec l ipt i c

a

150˚

+2

i l k Wa y y

ecliptic 195˚ longitude180˚

M

215˚ 210˚ +15˚ 0o

c i tp i l ce

HELIOCENTRIC VIEW of the orbit of Mars. The view is as in the Mercury-Venus picture, but with the constellations omitted from the front side of the sphere for clarity. A circle on the ecliptic plane shows the mean distance of Mars from the Sun (1.5237 a.u.). The planets are exaggerated 700 times in size. Dashed lines (each dash or gap 0.05 a.u. long) connect the positions of Earth and Mars at the dates of several successive oppositions, showing how the cycle of oppositions is spaced around the orbit. Before Sun-conjunction Mars is in the evening sky, and after it in the morning sky, as shown by the respectively black and gray curves. Mars’s summer solstice is (as for the Earth) when its north rotational pole is tilted most toward the Sun, and autumn equinox is when the pole is tilted most backward. The equatorial plane of Mars makes a circle around the sky perpendicular to this pole, cutting its orbital plane in the directions of Mars’s equinoxes, which happen to be roughly 90° from those of the Earth.

Astronomical Calendar 2015 0˚

345˚

CES PIS

e Mar 11

Feb 22

Uranus

Mar

Venus

2

U CET

S RIU UA Q A

or a t qu

1

h

Feb

0

315˚ +15˚ +10˚ + 5˚ 0˚

Jan -2

S

h

330˚

Neptune

15˚

Jan 20

30˚

h

23

0

RICAP US RN CO

o

-5˚ -10˚

h

22

h

-15˚

2018 Jul 27 opposition

lar c

ap----

Sep 1 Mar 1 Dec 31 Jan 1 Sep 1 2014 Apr 8 2012 Mar 3 2010 Jan 29 2016 Mar 1 2007 Dec 34 2016 May 12 opposition opposition opposition opposition 2015 opposition

THE DISK OF MARS at some dates in this year, also at oppositions from the record-breaking near one of 2003 through the distant one of 2012 to the next near one in 2018. The scale is 1 millimeter to 1 second of arc. The ecliptic plane (almost the same as the planet’s orbital plane) is horizontal. Short lines point to the north and south ecliptic poles; longer lines to the celestial poles. Direction to the Sun is shown by an imaginary stick, starting at the center of the planet (under the dot) and projecting one planet-radius beyond the surface. An arrow along Mars’s equator represents its rotation in 2 hours.

e

Ura nu

or a t qu

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2015 Dec 31

s e

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l

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n Sep 1

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u n

e

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on

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J up i ter

2015 Jan 1 0-6h UT

p

1987 l e y Ha l 1P

M

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Phobos

e

ve

al

Deimos

N

op

opposition Feb 6

2003 Aug 28 perihelic opposition

12

si

Ha l l e y 1982

2005 Nov 7 opposition

MARS AND SATELLITES at the beginning and end of this year. Equatorial north is at top, to suit observation in telescopes; lines point from the planet to equatorial north and south, shorter lines to ecliptic north and south. Scale is 1 mm to 1 second. The satellites go around Mars in almost circular orbits and in planes slightly varying from its equator. Their tracks are shown (in white) for 6 hours, starting at 0h UT, which is 7 p.m. Eastern Standard Time or 4 p.m. Pacific Standard Time ON THE PREVIOUS CALENDAR DATE. The rest of the orbit is in blue, with ticks at 1-day intervals. The orbits are drawn thicker where the satellites are nearer to us than the center of the planet. Phobos goes around in only 7.65 hours, Deimos in 30.3 hours. Since Mars rotates in 24½ hours, Phobos travels more than three times faster than the planet’s surface: seen by a Martian, Deimos goes over slowly from east to west (more than 2 days from rising to setting), but Phobos goes in the opposite direction, rising in the west and setting in the east, twice a day! (Compare the arrow on Mars’s equator, representing rotation in 2 hours, with Phobos’s larger movement in half that time.) The satellites are exaggerated 30 times in size. Both are elongated: dimensions of Phobos are 27x22x19 kilometers, and Deimos 15x12x11 (as against the 6800 km diameter of Mars).

Look closely and you will see that they are shown as ellipses. They rotate synchronously: that is, keep the same face to Mars. They are very faint: the magnitude of Mars is 1.1 on Jan, 1, 1.3 on Dec. 31, whereas Phobos and Deimos are about 13 and 14 magnitudes fainter.

OUTER PLANETS

1P

e noqr uato th ria

nort h po

2015 Jun 14 Sun-conjunction

ecliptic north

l

Mira

45

ars

es Cer

1

PL A C TI P I E CL

opposition May 23

Saturn

A

-

-

1

U

NE

-

opp osit

0

HELIOCENTRIC VIEW of all the planets from Earth (smallest ellipse) outward. The whole orbits are shown in blue (with stalks to the ecliptic plane at yearly intervals); paths for this year in black (stalks monthly). Besides the major planets, we show a few minor bodies (of which there could be thousands in the picture): dwarf planet Pluto; asteroid 1 Ceres (as an example of the Main Belt of asteroids between Mars and Jupiter); and Comet 1P Halley, which at its last visit was first observed in 1982, and now, on the scale of the picture, is 16 cm (6.3 inches) from the Sun, approaching its 2023 aphelion. The viewpoint has receded to a distance of 100 astronomical units. The equatorial and ecliptic planes are represented by circles around the sky at a distance from the Sun of 35 a.u. Each dash or gap in the opposition lines is 0.5 a.u. long.

ion

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ta

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Jul 6

o ut Pl

e

i i c

e

t

p

l

c

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60

Astronomical Calendar 2015

360˚ +25˚

ecliptic 345˚ longitude 330˚

315˚

Arct ur

ltair A300˚

285˚

270˚

255˚

+20˚

AQ

PIS

Jul 30 Alpha Capricornids

LIBR

180˚ +25˚ +20˚

VIR G

A

+15˚

O

+10˚ + 5˚

ec l ipt ic

Antihelion Jul 15

Antihelion Jul 1

S RNU RICO P A C o IS - 30 C S I P US RIN S U T

Antihelion Jun 15

Delta Aquarids Jul 30

-15˚

A

-20˚

0

h

aut h Fomalh 23

Coordinates of 2000

Piscis Austrinids Jul 28 h

22

- 40 h 21

Jan. 4: Quadrantids (peak 2h Universal Time; active Dec. 28–Jan. 12, mostly Jan. 1-5). Spoiled this year by Full Moon on Jan. 5. But this shower is worth describing as an introduction to the others. Its radiant is at right ascension 15h20m, declination +49°, about 15° east of Alkaid (h Ursae Majoris at the end of the Big Dipper’s handle). The radiant’s name is from a defunct constellation. Jérome de

Antihelion Apr 15

Antihelion Apr 1 Sp

ica

0˚

Antihelion Mar 15

SCORPIUS

IUS SAGIT TAR

-5˚ -10˚ -15˚

o

-20˚

20

h

19

h

18

17 h

h

15 h

16 h

Lalande, in his 1795 edition of Fortin’s celestial atlas, used a dozen faint stars just south of q and i Draconis to form Quadrans Muralis, the “wall quadrant”: a scale of degrees marked on a wall, for measuring the altitude of a star aligned with a telescope. A constellation isn’t needed in this star-poor area, and it dropped out of use—except in the name of these meteors.

They come to us from slightly behind of north (inclination 72° to the ecliptic), so their speed in the atmosphere is medium, about 41 km/s. The radiant is, for people north q

14

h

13

h

ove SUN rhe ad

12

h

-25˚

2015 Jan 4 2:00 UT

i

Edasich

zAMlc

DR ACO

URSAR MAJO 16 h

15

q

h

14

k

h

+50 o

u

Alkaid

o eB un

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BOOTES

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+40 o

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of 41° latitude, in the sky all the time. It is down by the northern horizon at the beginning of the night; swings slowly up in the northeast; is 45° high around 3 AM and nearly overhead toward dawn.

Quadrantids may be noticed visually over about 5 days. At the peak, rates may be from 60 to 200 per hour.

The ZHR is estimated at 120. Faint Quadrantids caused by small particles may peak half a day earlier, and there may sometimes be a second peak some hours later, detected partly by radio observations. The peak is fairly sharp. At its predicted time this year, the radiant is overhead in Asia. Watch the Quadrantids on the nights before and after peak.

Feb. 8: Alpha Centaurids (12h). The radiant, near a Centauri (Rigilkent, 3rd brightest star), is far south (declination —60°), so most of the meteors are below the horizon for northerners. Alastair McBeath notes that, if this stream is of long orbital period, “there could be a fresh outburst from it in 2015.” Moon between Full and Last Quarter.

On Feb. 1 and 13 our calendar page lists two showers, coming from the directions of Capricornus and Sagittarius. These constellations are where the Sun is in February; in other words, the meteors come at us in the daytime, cannot be observed visually, and have been detected by researchers using radio waves bounced off the meteoric particles. Other such ghostly showers are known in April, May, June, August, and September.

Mar. 25: Gamma Normids, earlier thought to peak around Mar. 15. A minor and scarcely-observed shower, whose radiant is around 16h —50° in the deep-southern Milky Way and so does not rise for those north of Florida. Only a brief low peak (ZHR 6) that seems to shift between March 8 and 18. Moon near First Quarter.

Apr. 23: Lyrids (0h; Apr. 16-25). Derived from Comet C/1861 G1 Thatcher, which was seen only in 1861, having a period of 415 years. Coming down at about 80° into Earth’s orbit, they are medium-swift (49 km/sec through the atmosphere); some are spectacularly bright; 20-25% leave persistent trains. The radiant, on the Lyra-Hercules border not far from Vega, is above the northeast horizon

N O d O ea M erh ov

Meteoroids are bits of solid matter out in space.

Encountering Earth’s atmosphere, and still moving at Earth-relative speeds from about 70 to 10 kilometers per second, they vaporize from friction, giving off light that is seen as meteors or “shooting stars”; sometimes leaving luminous trains for some minutes, or flaring bright enough to be called fireballs, or causing sounds. Remnants large enough to reach the ground are meteorites. Most meteoroids are small—pebbles or dust—and have separated from comets, typically centuries ago. Those that have not diffused too far apart orbit around the Sun as streams, appearing as showers when Earth passes through them at about the same dates each year.

Meteors of a shower can appear anywhere in the sky, but, because they are approaching almost in parallel, their paths if traced back appear to come from a radiant point or, rather, small area. From day to day, radiants move east because the direction from which the meteors appear to come changes as Earth proceeds around its orbit.

Because streams are vastly wider than the Earth, a shower may be active over days or weeks, though for part of this time shower meteors may have been detected only by means of camera or radar. A shower’s peak may be broad and indefinite or as sharp as hours or minutes.

There may be several peaks, implying sub-streams, perhaps of differently sized particles. The times we give are predictions by experts and may be best guesses. The calendar dates may vary by a day because of leap days (which is why scientists prefer to express them by longitudes of the Sun); and over centuries they drift later from month to month because of the precession of Earth’s axis.

Counts of meteors per hour are the raw data. A zenithal hourly rate (ZHR) is the average number that would be seen at the time if the radiant were at the zenith and conditions perfect. Observations help to define a stream’s radiant, peak, composition, and origin.

Meteors hitting Earth’s front—because they are traveling in retrograde orbits—are seen after midnight and enter the atmosphere at higher speeds. Meteor observing tends to be best before morning twilight!

Sporadic meteors are those untraceable to streams.

But also through most of the year (except when masked by other showers from near the ecliptic in October and November) there are meteors coming at low rates from a large area roughly opposite to the Sun (culminating about 1 AM local time). Formerly there were efforts to distinguish these into many minor showers, but since 2006 they have been treated as a general Antihelion Source.

A radiant at or even below the horizon can produce long bright trails across the upper atmosphere. However, the lower the radiant, the fewer meteors from it you will see, so the more favorable observations are made when the radiant is at least 25° to 30° above the horizon.

The other factors are atmospheric conditions and the Moon: if it is in the sky and bright, its light hides all but the brightest meteors. A First Quarter Moon sets around midnight, so does not hinder morning observation; Last Quarter rises around midnight. For the more prominent showers we mention this year’s Moon phase at the end of the entry in bold type, or in bold italic if it is markedly unfavorable.

Make yourself warmly wrapped and comfortable, as on a reclining chair; perhaps face east and gaze up at about 45° (easier than overhead, and you notice meteors anywhere between horizon and zenith). If the Moon is up, face away from it. Count the shower members you see in an hour. Don’t include those seen by anyone else.

Record sporadics separately.

Antihelion May 1

Antihelion AntaresMay 15

ds Quadranti overhead

METEORS

Antihelion Jun 1

theflight Ear of th

Antihelion Aug 1

Aug 15

-10˚

-25˚

195˚

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in ro on tat e h ion ou r

e c l i p t i c Antihelion Antihelion Sep 1

HERCU L ES

-5˚

+10

us

y

+ 5˚ 0˚

210˚

Wa

ecliptic latitude

CES Eta Aquarids

ky i l

+10˚

t or ua IUS eq UAR

May 6

225˚

equ a t o r

OPHIUCHU S

M

+15˚

240˚

by 10 PM and overhead by 4 AM. The ZHR is usually around 15-20, but there were outbursts in 1803, 1922 (96/hour), 1982 (250/hour for a few minutes). The shower has the longest history, beginning with a Chinese chronicle of 687 BC (when the peak was on March 25) and summarized in Gary Kronk’s invaluable book Meteor Showers. The shower has a narrow peak.

4 Rates +may be enhanced in 2015, even more so in 2016 and 2017. Moon just before First Quarter.

Apr. 24: Pi Puppids (5h; Apr. 15-28). By contrast with the Lyrids, they have a southerly radiant, at 7h20m —45° (now 8° farther south than the star p Puppis). They derive from Comet 26P Grigg-Skjellerup, which in its 5-year orbit (one of the shortest) has been seen many times since its discovery (by Pons) in 1808. Up to 38 meteors per hour have been seen from southern countries but only in years of the comet’s perihelion, and the comet’s orbit has now been deflected to outside the Earth’s by Jupiter.

May 6: Eta Aquarids (Apr. 19-May 28) are dust from the most famous comet, 1P Halley, which last came by in 1986 and will return in 2061. Its retrograde orbit crosses over the October part of Earth’s orbit and back out just under the May part; so we see sister showers, the Orionids of October (inward) and the Eta Aquarids (outward). In both, the meteors are very swift (head-on to Earth), often leaving trains; and there seem to be substreams spread over several days, with different average sizes of particles. The main radiant, near the Urn or Water-Jar or Y of Aquarius, is just below the celestial equator; for latitude 40° north it rises about 2 AM and is highest toward 8 AM. For the southern hemisphere, now in autumn, there are more hours of viewing before dawn twilight, and Australians have said this is the best shower of their year. Hourly rates can be as low as 10 for northerners, as high as 85 for southerners. There may be a 12year periodicity caused by Jupiter, with one of the low-rate times in 2014-2016. Yet the 2013 May 6 Eta Aquarids were exceptionally strong, up to 140 an hour; meteor scientists think this extra dust separated from the comet three or four thousand years ago. The enhancement is unlikely to continue this year. Moon 2 days past Full.

May 9: Eta Lyrids (May 3-27), from a radiant in Lyra that is (for the north hemisphere) high in the sky all night, may derive from Comet C/1983 H1 IRAS-Araki-Alcock of 1983. Only about 3 per hour, and the “peak” could be 2 days later.

June 16: June Lyrids (June 11-21). May or may not still exist. Discovered in 1966, confirmed in 1968 and especially 1969, later dwindled to nothing except for a possible showing in 1996. The radiant, 4° south of Vega, is up all night (for northern observers).

June 24: June Boötids (June 22–July 2), sometimes

Astronomical Calendar 2015

+15˚ +10˚

+1

0

0

+

OR

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1 2eh

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h

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Hydrids

called June Draconids, derive from Comet 7P PonsWinnecke, which in its roughly 6-year orbit has made many returns, some quite close to Earth, though now the comet’s orbit has moved outward. The peak date has varied between June 23 and 27. The radiant is given in northern Boötes but also varies; for 40° north it is overhead at 9 PM and in the sky all night. There were displays of up to 100 per hour in some past years near the comet’s perihelion; then after a dormancy of 70 years there was an unexpected outburst in 1998, another in 2004. These tantalizingly variable meteors can be recognized by their slowness (“only” 18 km/sec). Moon at First Quarter.

July 28: Piscis Austrinids (July 14–Aug. 10). ZHR may be as low as 5. The radiant, near Fomalhaut, is in view for northern observers only briefly and well after midnight, much longer and higher for the southern hemisphere.

July 30: Delta Aquarids (July 12–Aug. 23). A diffuse stream or group of streams. They are better for southerly observers, though for latitude 40° north the radiants are in the sky most of the night, highest around 2 AM. Two main sub-streams used to be distinguished, South and North, peaking around July 30 and Aug. 7. But the North Delta Aquarids have been found to be merely part of the Antihelion Source. Delta Aquarids appear sparse, because they are spread widely, but may add up to one of the most massive of streams. ZHR at maximum is around 20. The meteors are mostly faint, a few bright; 5-10% leave persistent trains; they move medium-slowly, about 41 km/sec, because coming in sideways across Earth’s orbit. Moon Full July 31.

July 30: Alpha Capricornids (July 3–Aug. 15).

Another diffuse complex, hard to distinguish—except by their slow speed of about 23 km/sec—from the Delta Aquarids and the Antihelion Source. They were once associated with Comet 72P Denning-Fujikawa, later with 45P Honda-Mrkos-Pajdusakova, but the orbits differ too much. For mid-northern latitudes the radiant is in the sky most of the night, highest at midnight. Though sparse (5 per hour, exceptionally 10), the Alpha Capricornids are photogenic, being often yellow, often bright, with many fireballs.

Aug. 13: Perseids (6h; July 17–Aug. 24). The morbid nickname “St. Lawrence’s Tears”—he was martyred on a hot gridiron 258 Aug. 10—may date back only to 1839.

Long regarded as our greatest and most reliable shower, later rivaled by the Geminids. Derived from Comet 109P Swift-Tuttle, which (with period around 120 years) appeared in 69 B.C., 188, 1737, 1862, and 1992. The radiant, in the region where Perseus meets Cassiopeia and Camelopardalis, is in the sky all night (for northern latitudes), at first low in the northeast, overhead toward 6 AM. The orbit is steeply inclined to Earth’s (113°, technically retrograde), hence passes near no other planet and is little perturbed. Historical records of the shower go back Eta L Ma yrids y6

Monocerotids Dec 9

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Sep. 1: Aurigids (14h; Aug. 25–Sep. 10). Discovered in 1935 by Cuno Hoffmeister (who later wrote a book on meteor streams); diminished since to ZHRs up to 5, with occasional outbursts, the last, in 2007, reaching 130. The peak has been on Aug. 31 or Sep. 1 depending on leap days. The meteors are swift (66 km/sec); many are very bright. They apparently follow the orbit of C/1911 Kiess, a long-period comet that will not come by again for more than a thousand years. The chief radiant is south of Menkalinan (b Aur); the shower was formerly called Alpha Aurigids when the radiant was thought to lie near Capella (a Aur). This area of the sky becomes high only after midnight and is highest after dawn. The predicted peak time is after dawn for most of America. Moon just past Full.

Sep. 9: September Epsilon Perseids (22h; Sep. 521). Not recognized as an annual shower until an outburst on 2008 Sep. 9. The ZHR is given as 5; twice as many or more may be seen in outburst years. They are swift (64 km/sec), often bright. The radiant is nearer to b Persei (Algol) than to e. It is in the sky all night, highest 4 AM local time. Waning Moon rises about 2 AM.

i M a W

0˚ +25˚ +20˚

Southern Taurids Oct 10

to China in AD 36 (when it was in July), Europe in 811; the 1866 occurrence was the first for which the link with a comet was made, by Schiaparelli. There were some amazing Perseid outbursts in 1980, the 1990s, and 2004.

Numbers seen rise slowly to the peak of 50 or more per hour, then drop faster. Sometimes two peaks have been distinguished, or more. The meteors are swift, 59 km/sec, which helps to distinguish them from the far less numerous Aquarids and Capricornids. Many are bright; white, yellow, green, red, orange; leave spectacular long-lasting trains; end in flares. There may be an earlier peak, Aug. 12 18h, of dust trails from the comet’s 1862 passage.

Moon New. Aug. 14: Kappa Cygnids (Aug. 6-10). The radiant is (for northern latitudes) much higher than that of the Perseids in the early night, near the zenith around 9 PM. There may be only 3 to 5 per hour, but they are characteristically bright, even fireballs, moving slowly (25 km/sec).

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Oct. 5/6: meteors from a radiant in Camelopardalis, possibly, but unconfirmed.

Oct. 9: Draconids (6h; Oct. 6-10) used also to be called Giacobinids because derived from Comet 21P Giacobini-Zinner, which in its 6.6-year orbit passes close to Earth’s, last doing so in 2012. The radiant is in the Lozenge or head of Draco, only 13° from the north ecliptic pole, so that unlike other radiants it scarcely shifts from day to day. Descending vertically onto the plane of the ecliptic, the meteors are slow-moving (20 km/sec). They

h h h 4h 1 2 3 -25˚ The radiants of most showers mentioned are shown in this ecliptic-based map, and/or the monthly sky maps. Short lines radiate from the radiants at the peak dates. (Most actual meteor paths are longer and farther from their radiant.) Marks at 1-day intervals show the radiants’ eastward drifts during their activity. The persistent Antihelion Source of meteors is represented by approximate positions of its moving radiant. The smaller charts are at a scale of 4 millimeters per degree.

typically are faint, and fragment easily. The radiant is high in the early night, low to the northern horizon 3-6 AM. In many years no Draconids are seen; but there have been strong showers or even storms near the comet’s perihelion, such as 1926 (a Draconid fireball “lit up the sky”), 1933, 1946 (15 days after the comet passed; up to 10,000 an hour seen in the southwestern US in full moonlight), 1985, 2005. Waning Moon rises about 3 AM. Oct. 10: Taurids (Sep. 10–Dec. 10). Complex of streams derived from 2P Encke, the comet with the shortest period (3.3 years) and most frequent visits. The meteors Space-trajectories of radiate from a large area that comet 109P Swift-Tuttle moves eastward along the eclip- and some of the Perseid tic from Pisces through Aries into meteors shed from it.

Taurus and is in view throughout these nights, highest about midnight. Spread over this time, they appear sparse on most nights. Because the general orbit lies in the inner solar system, with outer end near Jupiter, the stream has become perturbed into branches, which can scarcely be distinguished by the visual observer. The main ones are the Southern Taurids, the most abundant, with soft maximum in October (till recently it was thought to peak in early November), and the Northern, with peak Nov. 12. 2015 should see a return of the Taurid “swarm” of larger particles, in late Oct. and early Nov., producing higher rates and fireballs. Taurids appear slow, about 28 km/sec, because they are coming in across our orbit from behind.

As the stream goes back out, it encounters Earth’s daytime side and thus produces meteors detectable only as radio showers, the Zeta Perseids and Beta Taurids of June.

Oct. 11: Delta Aurigids (Oct. 10-18). There may or may not be a real shower, from a radiant at 5h36m +44°.

There were past indications, mostly unconfirmed, of several sparse streams coming from the Auriga-Perseus region.

Oct. 18: Epsilon Geminids (Oct. 14-27). Minor shower of very swift meteors (70 km/sec), perhaps derived from non-periodic Comet C/1987 B1 Nishikawa-TakamizawaTago, whose orbit passed 0.05 AU from Earth’s Oct. 7 position (and, on the way out, 0.12 AU from Earth’s July 12 position). Up to 3 per hour may be seen, but it is hard to separate these meteors, radiating from near Mebsuta (e Gem), from the more numerous Orionids coming from their nearby radiant. Moon 2 days before First Quarter.

Oct. 21: Orionids (Oct. 2–Nov. 7) are part of the stream coming inward along the approximate orbit of Halley’s Comet, to be seen on the way out as the Eta Aquarids of early May. But because the Orionids’ radiant, in the club of giant Orion near the feet of the Gemini twins, is up throughout a long autumn night for the northern hemisphere (highest at 4 AM), they are more familiar and have been more fully studied. Orionids are, like the Eta Aquarids, swift (66 km/sec); they are sometimes bright, and more than half leave persistent trains. The typical ZHR is 20; it can rise to 70, and sometimes there is more than one peak, presumably representing thicker clouds of particles coming along the orbit. There may also be a 12year cycle (caused by Jupiter), 2014-16 being a low part.

Moon at First Quarter.

Oct. 24: Leo Minorids (Oct. 9-27). Such a weak maximum (the ZHR is given as 2) that there is small chance of detecting them visually. The radiant at 10h48m +37° rises after midnight and is highest at dawn. Moon 3 days before Full.

Astronomical Calendar 2015

SU

62

N

Dec. 6: Phoenicids (22h; Nov. 28–Dec. 9). The radiant is 53° south, in Phoenix but just northwest of Achernar (a Eridani), so this is for south-hemisphere observers. The shower made its astonishing debut on 1956 Dec. 5: first R. Lynch in New Zealand, then others in Australia, the Indian Ocean, and South Africa, saw up to 100 per hour, many exploding as fireballs brighter than Venus. Since then they have been recorded only in scattered years, with peak rates from 2 to 5. They move slowly (18 km/sec). It was soon realized that they are debris from 289P Blanpain, which after its 1819 discovery was “the long-lost comet” (despite an only 5.1-year orbit), yet was rediscovered by stages from 2003 to 2013, and returned to perihelion in 2014. Moon 3 days past Last Quarter.

Dec. 7: Puppids (Dec. 1-15). A diffuse and vaguely known group of streams with as many as 10 radiants in a 20°-wide area of Puppis, Vela, and Carina. (So they might be called the “Argonauts.”) Up to 10 meteors per hour (some very bright) may be seen from the southern hemisphere.

Dec. 9: Monocerotids (Nov. 27–Dec. 17). Medium-

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Gemin ids

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Urs id

Qu adr

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1P

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For the Northern Taurids, see their Southern sisters in October.

Nov. 18: Leonids (4h; Nov. 6-30). The most dramatically variable of all. They follow the path of Comet 55P Tempel-Tuttle, strike Earth’s atmosphere slightly north of head-on (the inclination is 162°) and pierce it at 71 km/sec—almost the highest theoretical speed for meteors belonging to the solar system. This also means the shower is a morning one: the radiant, in the head of Leo (also called the “Sickle”), rises about 11 PM and is highest about 6 AM. Leonids are often bright, bluish; most leave persistent trains. Often only 5 to 20 per hour are seen at the maximum, but fantastic storms happen usually, but not always, near the times when the comet comes by in its 33year orbit, Many were vaguely recorded in early annals (such as 902, Arabic “Year of the Stars”), but it was 1833 (thousands per hour, woke people from their beds in eastern North America) that inspired Denison Olmsted to understand radiants and the periodic orbiting of the particles, thus founding meteor science. 1966 Nov. 17 (144,000/hour in Arizona, reaching 40 per second!) remains the most intense meteor storm known. The comet’s last visit was in 1998, the last storm in 2002. If this year’s peak is at 4h UT, it favors Europe; one expert puts the peak earlier, at Nov. 17 21h. Moon 1 day before First Quarter.

Nov. 22: Alpha Monocerotids (4h; Nov. 15-25).

Usually feeble, with up to 3 swift (65 km/sec) meteors an hour at maximum, but there were brief outbursts in 1925, 1935, 1985, and especially 1995: a 30-minute show with a 5-minute climax from which was calculated a ZHR of 420.

There may not be another outburst for a long time. The radiant, now in Canis Minor rather than Monoceros, is in the sky after 11 PM and highest at 4 AM. The peak time would put the radiant overhead for Europe. Moon 3 days past First Quarter.

s nid

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MOON

In these globe diagrams, “radiant overhead” is only one line, probably far from central, in the particle stream, which is vastly wider than the Earth. speed (42 km/sec) meteors derived from Comet C/1917 F1 Mellish (discovered 1917, not to return till 2062). Their radiant, 8° south of the celestial equator, is in view most of the night (highest 1 AM) for both hemispheres; but they are very sparse (maybe 2 per hour at most) and difficult to separate from the Geminids already starting. Moon 2 days before New. Dec. 12: Sigma Hydrids (Dec. 3-15). Sparse (up to 9 an hour but more typically 3), faint, swift (58 km/sec) meteors from a radiant, just north of the equator, near the head of Hydra, that rises not long before midnight and is highest at 3 AM. Various studies have given their peak as Dec. 6, 12, or 14.

Dec. 14: Geminids (Dec. 4-17) have since about 1960 surpassed the Perseids as most reliable among the annual showers. Instead of a sharp peak they have a “plateau,” this year from Dec. 14 1h to 23h, during which from 50 to 130 an hour may be seen. Their radiant, near Castor, is up for almost all of the long (northern) winter night, highest at 2 AM (so I once did a “star vigil,” logging Geminids and waiting for the constellations that first set to come back around into view). Geminids are medium-slow (35 km/sec) because coming sideways into Earth’s orbit.

Their long-sought parent body was discovered in 1983 by means of the IRAS satellite, and is not a comet but, uniquely, an asteroid: 3200 Phaethon, 5 km wide, with a 1.52-year orbit, shorter than any comet’s, passing over Earth’s orbit by less than 1/10 of the Moon’s distance (the asteroid’s next close approach will be in 2017) and then dipping 3 times nearer than Mercury to the Sun. This rocky origin explains the nature of the Geminids: mostly bright, very few leaving trains. Moon only 3 days past New.

Or

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2015 Dec 14 12:00 UT

The Perseid meteors and the comet from which they were shed, 109P Swift-Tuttle.

The comet was discovered in 1862 but Gary Kronk has found that it was seen by the Chinese in 69 B.C. and A.D. 188; it is in a 135-year orbit of high retrograde inclination le tt (114°), which comes close to u Earth’s and is locked in a -T 1:11 orbital resonance with Jupiter; it was last at perihelion (0.958 a.u. from the

ds Lyri

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2015 Nov 17 4:05 UT

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Dec. 16: Coma Berenicids and December Leo Minorids (Dec. 12-23). These may be one shower or two resulting from sub-streams of one stream—experts have changed their minds as to whether they can be separated.

If they can, the former may peak about Dec. 16, and the latter, slightly more abundant, about Dec. 20. Both yield only up to 3 meteors an hour, faint and swift (65 km/sec).

The radiant in Leo Minor, the obscure constellation above Leo’s back, rises about 10 PM and is up the rest of the night; Coma Berenices (which was once, according to story, the tuft on Leo’s tail) is 30° southeast, thus rises after midnight (for northern observers). Over this time the Moon is from 5 to 9 days old.

Dec. 23: Ursids (2h; Dec. 17-26) radiate from near Kokab, the b star of Ursa Minor, at the other end of the Little Dipper from Polaris. They were also called (before names were regulated by the International Astronomical Union) Ursa-Minorids or Umids. This radiant is (for latitude 40° north) in the sky all night, 26° above the north horizon in the early night, almost overhead by dawn.

These interesting meteors, filling the long cold winter-solstice night, are under-observed; it could be an even better candidate for a Star Vigil than the night of the Geminids!

The parent comet is 8P Tuttle, which at intervals of 13½ years drops steeply from the north through a perihelion close to Earth’s orbit; it last came by in January 2008.

(Comet and meteors revolve almost in the plane of the Milky Way, though in the opposite direction to that of the stars.) The meteors are of medium speed (33 km/sec), mostly faint but with a few fireballs; during the shower’s brief peak 9 or 10 per hour may be seen, up to 50 especially when the comet is near; in 1945 and 1986 the rate was over 100. If the peak is as predicted around 2h UT, it will be early night for America, past midnight for Europe.

Moon 2 days before Full.

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Sun) on 1992 Dec. 12.

The meteor stream, or rather the part of it that hits Earth, is suggested by particles traveling along five “strands,” in each of which one orbital element—the longitude of perihelion—is increased or reduced by one or two degrees, as if the particles separated from the comet somewhat before or after its perihelion. This results in the particles being increasingly (away from perihelion) spread out in the plane of the orbit, which is roughly what happens in an actual meteor stream. The stream is really far wider, but the Earth collides with only a tiny fraction of it. The meteors are shown blue where they are south of the ecliptic plane; the transition between gray and blue is where we see the meteors.

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Paths of some streams in space (blue when south of the ecliptic plane) and some of their parent comets.

Astronomical Calendar 2015

Altair

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PISCES 24

equa t o r

January

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VIRGO

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AQUARIUS

Central, Mountain, and Pacific zones, 6/24, 7/24, and 8/24 of the way. Its position is as seen from the center of the Earth, i.e. not adjusted for parallax. From a northern latitude it will be displaced slightly south. Its size is exaggerated 8 times; it appears slightly larger near perigee (such as Jan. 21) than apogee (such as Jan. 9). Gray areas are the dark maria (“seas”). We sometimes show stars and planets in front of the Moon, which, being exaggerated in size, would otherwise hideArcturus them much more often than it really does.

l k Mi ay W

These charts are of the zodiacal band—the zone around the sky within which the Sun, planets and Moon move. (The band shown is 40° wide, centered on the ecliptic.) Arrows show the planets’ courses during each month.

The Sun is shown at the 1st, 16th, and last day of the month; its disk is exaggerated 8 times in apparent size. At the middle of the month, its glare is indicated schematically.

The Moon is shown for each date at 0h Universal Time (Greenwich midnight). For local midnight at longitude 75° west (in America’s Eastern time zone) it will be 5/24 of the way east (left) toward the next date’s position; for the

ZODIAC CHARTS

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Astronomical Calendar 2015 Algol

Castor Pollux

CANCER

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p t i c ec l i

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Rigel Sirius

Libration is shown in these charts by red tabs on the Moon.

Each is at the place on the Moon’s limb (edge) most librated toward us, and its outward width is proportional to the amount of the libration. At and near this place you can see with your telescope a few degrees past the average horizon into the foreshortened features of the Luna Incognita (“unknown Moon”) on our

17

May 15

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21

22

an bar 19 e d ORION Al e q u aCapella tor

s nu Ve Beehive

s

y Pleiades

Mar s

Betelgeuse

Procyon

equa t or

nu

a Ur

19 New

Rigel r rcu e M

M i W lk a y

26 rter Qua

20

20

Mi Wa l k y y

First

21

PISCES

Algol

Venus

25

Mar 16

ARIES

erc ur Ma y rs

y

21

21

CETUS

TAURUS

equa t or

24

27

22

Betelgeuse

22

Mar

M

Sirius M35 t i c ec l i p

Beehive

oo n

ar s us

Rigel

ORION

Procyon

an

Ur

Algol

n

28

0 3 3

22

equa tor

ra ba

27

2

M

M

TAURUS

Venu Pleiades s

24

25

26 uarter First Q

1

PISCES

23

de Al

Regulus Apr

24

GEMINI M35 c i t p i Sirius l ec

Beehive

Ve nu s

25

y

Mi Wa l k y y

r ite Jup

Castor Pollux

CETUS

ARIES

equa t or

Mi Wa l k y y

CANCER

26

Betelgeuse

Procyon

oo n

Rigel

ORION

31

7

equa tor

M

22

Uranus

Algol

27 First Quarter

28

29

Feb

TAURUS

Pleiades Ald ec l i pt i c eb ara n

Sirius

PISCES

23

y

GEMINI

2

5

Full 6

Castor Pollux

Beehive

iter Jup 3

24

equa t or

Mi Wa l k y y

CANCER

ARIES

25

Betelgeuse

Procyon

7

CETUS

Pleiades

First Quarter 26

ORION

6

an Jan 25 us

Rigel

aran Aldeb

Feb 1

2

4 Full

5

Ur

Algol

27

M

3

26

equa tor

M35

M i W lk a y

Regulus

GEMINI

PISCES

Ja Mon 1 on

y

t i c Sirius ec l i p 28 ar 1

iter Jup

LEO

Mi Wa l k y y

Castor Pollux

First Q ua 27 rter

28

equa t or

M i W lk a y

10

11

LEO

Betelgeuse

ARIES

29 2

ORION

8

Pleiades

TAURUS 30

31

5 Full

6

7

Feb 1

es ad an Hyebar Ald

r ite Jup

LEO

M i W lk a y

y

neighbor small planet’s far side. But if the place is on the dark half of the limb, where you can’t see anything, the libration is of no advantage; this is indicated with a tab of paler color. The librationspot is always on the hemisphere nearer to the ecliptic, because when the Moon is south of the ecliptic plane we are looking slightly “down” on it—its north pole is in view—and vice versa.

11

M

oo

n

69

70

Astronomical Calendar 2015 The zodiacal charts are handy for surveying the state of the sky. “Night” is from the Sun leftward and all the way back around to the Sun. Starting at the Sun, you see to its left the stars and planets that are low in the evening sky and about to set after it; leftward from them, the bodies that are prominent in the early night; leftward again, those that are at or near opposition (including the Full Moon); leftward again, the morning sky, and finally to the Sun’s right are the bodies that rise in twilight just before it.

l k Mi ay W

Altair

PISCES

y

July

The Moon and planets pass through the twelve constellations of the traditional zodiac plus Ophiuchus, and some of them can also wander southward into Cetus, Orion, Hydra, Sextans, Corvus, and Crater, or northward into Auriga, Scutum and Pegasus. Pluto can enter Eridanus, Coma Berenices, Serpens (Caput), Serpens (Cauda), and Boötes, and other minor bodies with high inclinations Arcturus can be in any constellation.

(See Jean Meeus, More Mathematical Astronomy Morsels, p. 333.)

equa t or OPHIUCHUS

Ne

Aug 1

pt un 6 e

LIBRA

Jul 2

2

23

Firstter Quar 24

AQUARIUS 7

VIRGO

equa tor

25

Full 31

30

5

27

28

29

26

4

3 P luto

CAPRICORNUS

Saturn

2 Full

Spica

ic ipt ec l

Jul 1

Arcturus

Antares M lk i y a W

l k Mi ay W

Fomalhaut

SAGITTARIUS

y

Altair

PISCES

y

31 3

August

30 Full

SCORPIUS

equa t or

VIRGO

equa tor

AQUARIUS 2

Ne

29

ptu

1 Aug

19

OPHIUCHUS Aug 1

ne

28 27

26

24

25

21

22

Spica

rn tu Sa

Plut o

CAPRICORNUS

20

LIBRA

First Quarter 23

8

ec l ipt i c

Arcturus

Antares

M lk i y a W

l k Mi ay W

Fomalhaut

SAGITTARIUS

y

Altair

PISCES

y

27

September

26

SCORPIUS

equa t or

VIRGO

equa tor

OPHIUCHUS

ptu n

24

e

23

22

First Quarter 21

17 18

19

20

Spica

M

ry u c er

rn Satu

Pl

ut o

CAPRICORNUS

16

LIBRA

25

Ne

15

Sep

AQUARIUS

ec l ipt i c

Arcturus

Antares

M lk i y a W

l k Mi ay W

Fomalhaut

SAGITTARIUS

y

25

y

Altair

PISCES

October

24

Ne p

VIRGO

SCORPIUS

equa t or

equa tor

New 13

AQUARIUS OPHIUCHUS

23

Fir Quartster 21

22

tun e

14

Oct

15 20

16

17

18

19

12

Spica

rn

Pluto

CAPRICORNUS

LIBRA

ry rcu Me

Satu

ec l ipt i c

Arcturus

Antares

M

SAGITTARIUS

y

Altair

PISCES

y

F Quairrst ter 19

20

Nep

VIRGO

SCORPIUS

equa t or

21

November

lk i y a W

l k Mi ay W

Fomalhaut

equa tor

OPHIUCHUS 18

tune

17

16

10

LIBRA New 12

13

14

15

AQUARIUS

s

nu Ve

11

M

y ur erc

ar

s

M

8 Nov

9

Spica

n Satur

Pluto

CAPRICORNUS

ecl ipt ic

Arcturus

Antares

M y

y

December

PISCES Qua rter 18

l k Mi ay W

First

SAGITTARIUS

Altair

lk i y a W

Fomalhaut

SCORPIUS

equa t or

AQUARIUS 17

LIBRA 9

ptu

ne

15

ecl ipt i c CAPRICORNUS

14

13

New 12

Saturn

Pluto

Mer

10

11

cur y

Antares M

SAGITTARIUS

lk i y a W

Fomalhaut

y

SCORPIUS

us Ven

8

5 Dec

6

7

OPHIUCHUS 16

Ne

VIRGO

equa tor

M

ars

Spica

Astronomical Calendar 2015 Algol

GEMINI

Castor Pollux

CANCER

s 18

e V 19

Castor Pollux

CANCER

Regu lus iter Jup

y ur rc

w 15 Ne

e

M

13

14

s Venu

16

10

M i W lk a y ORION

equa tor

ARIES

M i W lk a y

30

8

29

Castor Pollux

Dec 1

Regulus Last r 4 Quarte

6 5

LEO

Beehive

Full 26

27

ARIES PISCES

2

3

Aldebaran ORION

23

TAURUS

Betelgeuse equa t or

Mi Wa l k y y

Castor Pollux

24

Algol

y

GEMINI

Ur an

equa tor

Nov 22

us

CETUS

Rigel

M35

Pleiades

TAURUS

t i c Sirius ec l i p

ARIES PISCES

26

24

ORION

29

Betelgeuse

Procyon Mi Wa l k y y

equa t or

23

22 21

equa tor

s u n ra

27

25

U

28

Full

an bar

6 201 1 Jan

30

31

Pleiades

e Ald

Ju

4 er pit

CETUS

25

Dec 1

Lasrtter Regulus 2 Qua 3

equa tor

Rigel

Nov 1

Procyon

CANCER

Oct Ur 26 an us

Algol

28

29

30

27

Oct 1

TAURUS

M35

c e c l i p t i Sirius

Beehive LEO

GEMINI

M i W lk a y

CANCER

2

y M i W lk a y

Oct 1

n ra a eb

d

Al

PISCES Full

28

equa t or

Mi Wa l k y y

11

3

ORION

Betelgeuse

Procyon

10

ter 7 pi Ju

4

Last Quarter

1 TO TA EClLunar L Sep IPSE 28

Pleiades 31

5

6

CETUS

Rigel

M35

7

Full 28

Sep

Algol

LEO

Regulus r ite ars p M Ju us 9 Ven

29

2

y

t i c Sirius ec l i p Nov 1

Beehive

3

equa t or

GEMINI

Castor Pollux

30 4

Betelgeuse

Procyon

CANCER

PISCES

Oct 1

6

Mi Wa l k y y

Sep 30

ARIES

n ara 5 eb d l A TAURUS

7

Venu s

tial parLAR SOLIPSE ECep 13 S

Pleiades Last Quarter

8

Aug 4

Rigel

M35

9

Sep 1

CETUS

s

us ul

12

14

11

Algol

t i c Sirius ec l i p

10

s

5

equa tor

y

rs

nu

6

u

g Re

New 13

TAURUS

equa t or

GEMINI

Ur a

Last Q7 uarter

n

r ite

Jup

PISCES

ra U

Ma

ARIES

A ld eb ara 8 n

9

Betelgeuse

Mi Wa l k y y

Castor Pollux

CETUS

Pleiades

ec l i p t i c

11

Procyon

Jul 8

Rigel

ORION

Beehive LEO

Algol

M35

17

CANCER

us

equa tor

Sirius

12

QuLaast rter 9

n Ura

TAURUS

y

GEMINI

s Mar

Beehive

10

equa t or

Mi Wa l k y y

21

LEO

Betelgeuse

M i W lk a y

20

ORION

Procyon

PISCES

11

14

15

16 New

17

ARIES

12

Jul 1

an ar eb

u n

ec l i p t i c 13

ur y

d Al

Regulus

r ite Jup

Pleiades

M35 Merc

Mars

Beeh ive LEO

M i W lk a y

y

20

CETUS

Rigel Sirius

Dec

19

71