2012 Astronomical Calendar

cov12.qxd

01/09/2011

07:08

Page 1

Astronom ical Calendar 2012

Zenith light

months.qxd

01/09/2011

07:49

Page 6

2012 Jan

Astronomical Calendar 2012

CA

NC E R i

sky

t gh

e

g

L

18

UCH

S NU

OR

IC CA

IU S AG I T T A R

US

P

R

Solar System Plan

S

t

t

in

g

aphelion perihelion node opposition greatest elongation conjunction with Sun conjunction of planets (in longitude)

se

++ 66 0

o o

t

DRA CO

i

s

no

o o

o o

+6 M0 i

Ca

ve

++4400 GEM

NC ER

9 eq

8

ua tor

6

h h

MONO

AN

TRI

s Pleiade

5

A h h

ES ARI

22

TAURUS

ORION

33

h h

ce l es t i a l

a

f

first r quarte Jan 1

th

e

C

c ir

n

o Mo

le

t

hh

2 33 7 Jan 2

hh

28

00

29

c e c l i p t i Uranus

30 31 first quarter Jupiter

44

oo

00 e g ++22 P

2

3

4

es Hyad

55 hh

S

CE

PIS

q

hh

11

hh

hh

o r equa t

Mira

S

CETU

Rigel Sirius

y

(movem e t of sk in 1 hn our) y

k

r i s i ng

l

CANIS MAJOR

-- 2200 oo LEPUS

so

M

i

y ent of sk (movem hour) 1 in g t i n s e t

ERIDANUS

FORNAX

u

th

ea s

so

t COLUMBA

open cluster

PUPPIS

CAELUM

-- 4400 oo

n

nebula

o

planetary nebula ma g n i t u d e s

s e t t i ng

r i s i ng

globular cluster

h 0

—1

1

2 3 4 5

galaxy

s ou t h

o

r

i

z

u

th

w

e

s

see map for: for: 5–6 p.m. November December 7–8

t (star background only— not solar-system bodies)

W

a

CEROS

66

M LU M33 GU

o o

aran ldeb

77

y

7

Betelgeuse

AS US

t A

Nath

++ 22 00

Proc yon 88 hh

PERSEUS

a

o

INI

CA MIN NIS OR

h h

ZE

s

ce l e s t i a l

G

re

s

a

CA

o o

AURIGA

full 9

10

NI

S t

u

RO

D

ol Alg

TH

st llu or x

PE G

oo

0 A

ED

M

s

NX

o o

+4

he

O

E

++ 66 00

a ed m xy o dr ala An G

IS

re

RDAL CAMELOPA

ua

le

Po

hh

no

EIA

Ga z el

11

s e t t i ng

LACE RTA

y

p ip

D

Li t

CEPHEUS

k

er

oo

t le

+80

l

we s t

++8800 W

o o

Capella

Beeh i

rt

b Dene

SA R UR O IN M

rt

O LE R O IN

M

s o f t he

hw

e

s

r

ap

a

OP SSI CA

L HY DR

HI

N A

12

S

OP

no r t h o o

Le

LY

13

AN

AQU A R I U S

Ma r

V I RG O

ES

++8800

e

++ 88 00

l i R p t egu i c lus

SE XT

.

Pluto

s

re

is lar Po

SA UR OR J MA

oo

Th

10

ury-Pluto 13 Merc

eor

o o

00

hh

11 11

eas t

c

nu s Ve

ds t i

ry

met o o

++4400

++22

e

S CO

pt un e

y

e r p p D i ++6600

CANES

ng s i r i

VENATICI

B i g

5h

2.0 Ne

A

rad i Quaant of dra ntid

in g

Sky Map about 10 p.m. at the 5th of the month or 9 p.m. at the 20th For latitude 40° north and sidereal time

Big Dipper now stands like a question mark.

Western end of Leo like a reverse question mark with Regulus the dot.

C

an

cu

El Nath (Arabic “the butting”), point of the upper horn, formerly belonged to Auriga as well.

Auriga is an irregular pentagon if El Nath is included.

Capella and Rigel are on a northsouth line. More loosely, so are the whole right and left sides of their two constellations.

Below Orion’s feet: the Hare (Lepus), then the Dove (Columba).

BR L I

Betelgeuse red, Rigel blue.

Taurus, the Bull, rushes down on Orion.

Orion raises shield and club to defend himself.

The Bull: triangular face (Hyades) and two long horns.

Aldebaran a red glaring eye.

Pleiades in the hump of the Bull’s shoulder.

S

y

dr

13 Uranus sca le o Ve f n 0.5 ast usron Ne pt 1.0 omica l un une i t 1.5 s

Sun

urn Sat

constellation clues

I

sk

ua Q

n ihelio 5 per

M42, Orion nebula σ Orionis, multiple star M35 cluster Rosette nebula Castor, double star Praesepe cluster M81 galaxy γ Leonis, double star Mizar, double star

Mer

22 35 21 52 54 41 04 51 55

y

—5 —2 +24 +4 +31 +19 +69 +19 +54

k

35.4 38.7 08.9 32.4 34.6 40.4 55.6 19.9 23.9

s

5 5 6 6 7 8 9 10 13

g

ψ Draconis, double star M31, Andromeda galaxy M33, Triangulum galaxy γ Andromedae, double star Perseus double cluster ι Cassiopeiae, triple star η Persei, double star Pleiades R Leporis, Crimson Star

10 16 39 20 08 24 53 06 47

th

in

+72 +41 +30 +42 +57 +67 +55 +24 —14

r Ea

rn

41.9 42.7 33.9 03.9 21.5 29.0 50.6 47.5 59.6

r te pi u J

s

mo

17 0 1 2 2 2 2 3 4

P

in

telescopic tour (coordinates of 2000) h m ° ´

ES

v

m

E

AR I

n

n id

T AU R U S

I

IN G EM

e

JANUARY

Januarius, month of the god Janus who faces both forward and backward through the door

O

6

11–12 1–2 a.m.

3–4 5–6

February March April May

Jan. map serves for Feb. 7–8 p.m.

Mar. 5–6 Sep. 5–6 a.m.

Oct. 3–4 Nov. 1–2 Dec. 11–12 p.m.

months.qxd

01/09/2011

07:49

Page 7

Astronomical Calendar 2012

January 1 SUN. ( 0:06 local time) Upper culmination of Sirius (it crosses the meridian). Jan. 1 is said to be the date when this happens at midnight. Actually it happens even nearer to Jan. 2 0h; and in later years will happen nearest to midnight on later dates, because of precession (see Sky & Telescope, 2008 Nov., p. 91). ( 6:15 UT= 1:15 EST) í ‘ Moon at first quarter. ° 2 Mon. (20 UT=15 EST) Moon at apogee. Distance 63.43 earth-radii.

(24 UT=19 EST) Moon 4.8° N.N.W. of Jupiter (about 108° from Sun in evening sky). ° 4 Wed. Quadrantids. See METEORS. Quite favorable year for this major shower. ° 5 Thu. ( 0 UT=19 est) Earth at perihelion—that is, nearest to the Sun. The date varies (because of the swinging of Earth and Moon around their barycenter) from about Jan. 1 22h near last-quarter Moon as in 1989, to Jan. 5 8h near first-quarter as in 2020. The Sun-Earth distance also varies; this year, it is about 0.98327 a.u. (147,096,000 km).

Perihelion and aphelion hardly affect our warmth, as they do for Mars. See aphelion, July 5; aphelion of Mars, Feb. 15; and Astronomical Companion, SEASONS. Latest sunrise (7:22 a.m.) at latitude 40° north. See more fully under earliest sunrise, June 14.

(10 UT= 5 EST) Moon 2.8° S. of Pleiades (about 135° from Sun in evening sky). ° 6 Fri. ( 6 UT= 1 EST) Moon 5.9° N. of Aldebaran (about 144° from Sun in evening sky). zenith (14:29 UT= 9:29 EST) Moon at descending node (longitude 74.1°).

7 SAT. Eastern Orthodox Christmas, at least as celebrated by “Old Calendarists� still using the Julian calendar, in which Dec. 25 is now 13 days after Gregorian Dec. 25 (see Jan. 14). In the 19th century it fell 12 days after Christmas, on Jan. 6, so there is some confusion with the Twelve Days of Christmas, ending on Epiphany, Jan. 6, the Adoration of the Magi.

80 o 80 o (21 UT=16 EST) Mercury at descending node through the ecliptic plane. _____________________________________________________weeks____________ 8 SUN. (24 UT=19 EST) Mars at greatest latitude north of the ecliptic plane (1.8°).

9 Mon. ( 7:31 UT= 2:31 EST) í ” Moon full. See SPECIAL MOONS. (16 UT=11 EST) Moon 10.0° S.S.W. of Pollux (175° and 172° from Sun in the o 70 70 o midnight sky). ° 10 Tue. (19 UT=14 EST) Moon 5.5° S. of Beehive Cluster (162° from Sun in morning sky). ° 12 Thu. ( 7 UT= 2 EST) P/2006 T1 Levy at perihelion, 1.0069 a.u. from the Sun. See COMETS. ( 9 UT= 4 EST) Moon 5.5° S.S.W. of Regulus (142° from Sun in morning sky). ° 13 Fri. Friday the 13th—supposed to be very unlucky because both the day and the 60 o 60 o number are unlucky. (In South America the unlucky day is Tuesday and in Italy the unlucky number is 17. In Iran women stay outdoors on the 13th day of the year to avoid bad luck.) This year has three Fridays-the-13th: see April and July. They occur every year, either once or twice (each in 42-44 years per century) or 3 times (14 or 15 years per century: common years beginning with Thursday, such as 1981, 1987, o 1998, 2009, and 2015, when, occurring in February, it must also occur in March; 50 o 5 0 or, most rarely of all, leap-years beginning with Sunday, such as 1984, 2012, 2040, 2068, 2096, 2108). Actually, Friday falls on the 13th more often than any other day does!

(Because Sunday most often falls on the 1st.) In every span of 400 years after 1582 (beginning of the Gregorian calendar) the numbers of Sundays-the-13th, Mondays-the13th etc. are: 687 685 685 687 684 688 684. o 40 o ( 3 UT=22 est) 78P Gehrels 2 at perihelion, 2.0082 a.u. from the Sun.4 0See COMETS. °

° 14

Âą 16

Âą 17 Âą 18 Âą 19 Âą 20

Âą 21

² 22 ² 23 ¹ 25 ¹ 26 ¹ 27 ¹ 28

° 30 ° 31

7

( 7 UT= 2 EST) Mercury 4.6° S. of Pluto (15° from Sun in morning sky).

Conjunction in r.a. is 1.4 hours later.

(16 UT=11 EST) Venus 1.1° S.S.E. of Neptune (36° from Sun in evening sky); magnitudes —4.0 and 8.0. Conjunction in r.a. is 9 hours earlier.

SAT. This day is Jan. 1 in the Julian calendar, which was superseded by the present Gregorian calendar from 1582 (later in many countries). It is the first day of the Roman year 2765 A.U.C. (ab urbe condita, “from the city foundedâ€?). Julian years won’t diverge by another day (starting on Jan. 15) until 2101. See Ast. Companion, CALENDARS. ( 1 UT=20 est) Moon 8.4° S.S.W. of Mars (121° from Sun in morning sky). ______________________________________________________________________ Mon. ( 5 UT=24 est) Moon 2.2° S.W. of Spica (about 91° from Sun in morning sky). ( 9:08 UT= 4:08 EST) í ? Moon at last quarter.

(17 UT=12 EST) Moon 6.1° S. of Saturn (about 86° from Sun in morning sky).

(21 UT=16 EST) 11 Parthenope 2.0° S. of Pluto (about 18° from Sun in morning sky).

Tue. (22 UT=17 EST) Moon at perigee. Distance 57.99 earth-radii.

Wed. ( 6 UT= 1 EST) Mercury at aphelion, 0.4667 a.u. from the Sun. Thu. (12 UT= 7 EST) Moon 4.2° N. of Antares (49° from Sun in morning sky).

(18:30 UT=13:30 EST) Moon at ascending node (longitude 253.5°).

(21 UT=16 EST) Saturn at west quadrature.

Fri. ( 7 UT= 2 EST) í “ Sun enters Capricornus, at longitude 299.62° on the ecliptic. (Because of precession these constellation-boundary-crossing-points shift eastward slightly along the ecliptic each year, i.e. their longitudes increase; so their dates become a few hours later.)

(16 UT=11 EST) Sun enters the astrological sign Aquarius, i.e. its longitude is 300°. But astronomically it has only just entered Capricornus. See Ast. Companion, PRECESSION. SAT. (13 UT= 8 EST) Moon 1.8° S.S.E. of Pluto (about 22° from Sun in morning sky).

(18 UT=13 EST) Moon 1.2° E.N.E. of 11 Parthenope (about 20° from Sun in morning sky). See ASTEROIDS. The Moon again passes close on Feb. 19. ______________________________________________________________________ SUN. ( 7 UT= 2 EST) Jupiter at east quadrature.

(11 UT= 6 EST) Moon 4.7° N.N.W. of Mercury (only about 10° from the Sun).

Mon. ( 7:41 UT= 2:41 EST) í ’ Moon new. Beginning of lunation 1102.

Wed. ( 0 UT=19 est) Mars stationary in right ascension; begins retrograde (westward) motion. The stationary moment in longitude is 24 hours earlier. ( 7 UT= 2 EST) Moon 5.5° N.N.W. of Neptune (25° from Sun in evening sky).

Thu. (14 UT= 9 EST) Moon 6.3° N.N.W. of Venus (39° from Sun in evening sky).

Fri. (23 UT=18 EST) Moon 5.5° N.N.W. of Uranus (about 54° from Sun in evening sky).

SAT. ( 4 UT=23 est) Uranus crosses equator northward. This is the last part of a triple event: Hranus entered the northern celestial hemisphere on 2011 Apr. 9, looped back southward on 2011 Oct. 16, now definitively moves to the north, where it will be till 2053 July 16. ______________________________________________________________________ Mon. (12 UT= 7 EST) Moon 4.4° N.N.W. of Jupiter (about 82° from Sun in evening sky).

(18 UT=13 EST) Moon at apogee. Distance 63.39 earth-radii.

Tue. ( 4:11 UT=23:11 est) í ‘ Moon at first quarter. ( 8 UT= 3 EST) Saturn at greatest latitude north of the ecliptic plane (2.5°). This heliocentric event occurs only once in the 29-year orbit of Saturn.

The Milky Way on January evenings crosses overhead diagonally from southeast to northwest.

30

o

30

o

20

o

us

o

mo 10

o

t

n io

of

sk

y

in

1h

ce

Mi

l

es

a ti

l

e

a qu

l k y

to

r

Wa

ry cu er

e

c

l

i

p

t

i

c

altitude

20

our

n Ve

es tar

An

10

o

M

y o ut Pl

horizon for latitude 40Ëš 40 north

E

SE 135Ëš 135

90Ëš 90 n Su

Jan. 9, 45 minutes before sunrise 6:37 a.m. EST (= Jan. 9, 11:37 UT)

Observers’ highlights for January by Fred Schaaf s you’re not where the parThe highlight of the monthar(if M tial solar eclipse is visible) could be Venus and Mercury superbly displayed before dawn or Jupiter and Uranus’s close final of three conjunctions.

Venus and Mercury Both at Fine Greatest Morning Elongations. For viewers around 40° N latitude, brilliant Venus rises about 3ž hours before the Sun and Mercury about 1ž hours—both amounts nearly the maximum ever possible—in the opening days of 2011. Venus is at greatest elongation from the Sun (47° in this case) on January 8 and Mercury is at greatest elongation from the Sun (23°) on January 9. At this time Mercury is a minimum of 24° lower left of Venus. On their respective dates of greatest elongation, Venus glows at magnitude —4.5 with telescopes showing its 25″- wide globe 50 per cent lit and Mercury shines at —0.3 with telescopes showing its 6.7″-wide globe 64 per cent lit. Both planets decline somewhat as the month advances but Mercury does so drastically, down to rising only 40 minutes before the Sun at month’s end. Venus is slding down to

the left of the vertical pattern of Scorpius during January, the planet’s closest approach to Antares taking it less than 8° to the star’s upper left on January 17th. (For this month’s fine conjunctions of the Moon with Venus, Mercury and Antares, see note below.)

Jupiter’s Close Third and Final Conjunction with Uranus. Jupiter is prominent and bright in the southwest at nightfall all month but it’s on January 3 and 4 that binoculars or telescope can show Uranus only about 1/2° to the big planet’s upper right. The globe of magnitude —2.3 yellowwhite Jupiter is 38.5″ wide, that of magnitude 5.9 blue (or blue-green) Uranus only 3.4″ (to see its tiny dot well will require a night of good “seeingâ€?—steady atmosphere).

These two planets were in conjunction back on June 6 and September 22, 2010.

Partial Eclipse of the Sun for Parts of Europe, Africa and Asia. For more details on this large partial eclipse, see ECLIPSES. Saturn, Fairly Near Spica, Enters the Evening Sky. Saturn starts the year rising about half an half an hour after midnight but by the end of January is coming up around

10:30 p.m. (for viewers at mid-northern latitudes). The magnitude 0.8 planet rises with slightly dimmer Spica as little as 8° below it—until late in the month, when Saturn starts moving with retrograde motion westward away from Spica.

Saturn is at west quadrature (90° from the Sun) on January 7th so the shadows cast to the side by its globe and rings make the system appear even more three-dimensional than usual. Telescopic observations will be best near dawn, when Saturn is highest, in the south.

Moon Meetings. The waning lunar crescent is lower right of Venus on December 31, closer above Antares on New Year’s Day, and lower right of Mercury on January 2.

The Moon is New on January 4 and therefore is not in the night for its light to hinder viewing the Quadrantid meteor shower (see METEORS for details). The waxing lunar crescent is fairly near Jupiter on the evenings of January 9 and 10.

The waning gibbous Moon forms a triangle with Saturn and Spica in the pre-dawn hours of January 25. At dawn on January 29 the lunar crescent is almost straight between Venus and Antares and on January 30 lower left of Venus.

Page 38

Astronomical Calendar 2012

full new

Feb .7

e as clip m c s id to endi e se wa ng as rd no on Su de n

21

Sun

de eclip mi sc se d towendi sea Moon ard ng n son Earth Su ode n

6

2 Apr. new

full Sep. 30 new Sep. 16 full Au g.

new

31

Aug . 17

ful lA ug .2

ly Ju

3 July full

19

lun II ar . Ju PA ne RT 4 IAL

15

where you live, it’s no great loss: penumbral eclipses are underwhelming, to say the least.

My usual thanks are in order to Mr. Raymond Brooks of Star Engineering in Arizona, for providing the precise times for the midpoints of the eclipse seasons, as well as reviewing my original manuscript and making helpful suggestions. My thanks go also to meteorologist Jay Anderson for the raw climatological data and narrative summaries available online at eclipser.ca . . . == a web page that is devoted to eclipses, transits, occultations and other astronomical events in which weather conditions play an important role. Go to: http://home.cc.umanitoba.ca/~jander/

For the solar eclipses go to page 42 →

The lunar eclipses

2012 June 4 Moon

8 hours

8 hours

Ea

1 degree

a

di ld h 's a v e a t Mo o n

st

an

c

a rth ' s p e n u mb r

1 degree

SCORPIUS

z si

a nc

e

ra

56 Tau

n

st

E

t h' s u ar

a

di

tic 1 degree

r

d hav e a t Mo o

's

ecli p

Ea

w oul th

mb

the

e

' s pe num rth br

1 degree

north

Ea

κ Tau 67 Tau

north

north

r

OPHIUCHUS

wou

t h ' s u mb r

north

E

ar

th

e

cliptic the e

Ea

VIEWS TOWARD THE MOON at successive stages of its encounter with the Earth’s shadow. This is what can be seen from almost everywhere on the night side of the Earth. The umbra and penumbra are represented by crosssections through them at the distance where the Moon is. They are visible only where they fall on the Moon. The umbra has a fairly abrupt edge; its darkness and color vary with atmospheric conditions around the Earth. The penumbra is imperceptible except in its inner part. The umbra gets narrower as it goes farther away; the penumbra, wider. A circle between them represents the size of the body casting the shadows: the Earth we are standing on.

Arrows show the motion of the shadow and the Moon over a span of 8 hours.

The Moon moves faster because it takes only a month to go around the sky, while the shadow (like the Sun opposite to it) takes a year. However, since the shadow does move along somewhat during the eclipse, the diagram, representing the relation of the Moon to the circular umbra and penumbra, cannot be exactly true in all respects: the Moons ought to be slightly wider apart.

Any star shown in the field is plotted in relation to the Moon and shadow at the middle moment of the eclipse—and as seen from the center of the Earth.

8:47

9:59

11:03

12:07

13:20

touches penumbra

touches umbra

mid eclipse

quits umbra

quits penumbra

ze

Penumbral lunar eclipse of November 28 All times U.T. Nov. 17, 21:00:57—Middle of eclipse season; Sun at same longitude as true ascending node.

Nov. 27, 17:05—Moon’s center reaches descending node through ecliptic.

Nov. 28, 12:15—Penumbral eclipse begins; first contact of Moon with Earth’s shadow.

14:33—Middle of eclipse: Moon nearest to center of Earth’s shadow. The penumbral magnitude of the eclipse is 0.9155; that is, the penumbra reaches across that fraction of the Moon’s diameter.

14:46—Full Moon (Moon at opposition to the Sun in ecliptic longitude). Moon’s center is exactly south of center of Earth’s shadow, as measured perpendicularly to ecliptic.

14:46—Moon at opposition to Sun in right ascension; its center is exactly south of center of Earth’s shadow, as measured perpendicularly to ecliptic.

16:51—Penumbral eclipse ends: last contact of Moon with Earth’s shadow.

20:09—Moon at apogee.

252,501 mi (406,362 km).

This is eclipse no. 11 of the 73 in lunar saros series 143 (1832 Aug. 11 to 3094 Sep. 16).

si

Partial lunar eclipse of June 4 All times U.T. May 26, 01:55:33—Middle of eclipse season; Sun at same longitude as descending node.

June 3, 12:56 —Moon at perigee.

222,752 mi (358,485 km).

20:38—Moon’s center reaches ascending node through ecliptic.

June 4, 08:48—penumbral eclipse begins; first contact of Moon with Earth’s shadow.

10:00—partial eclipse begins; first contact of Moon with Earth’s umbra.

11:03—middle of eclipse: Moon is nearest to center of Earth’s shadow.

The umbral magnitude of the eclipse is 0.3704; that is, the umbra reaches across that fraction of the Moon’s diameter.

11:12—Full Moon (Moon at opposition to the Sun in ecliptic longitude).

Moon’s center is exactly north of the center of the Earth’s shadow as measured perpendicularly to the ecliptic.

11:12—Moon at opposition to the Sun in right ascension; its center is exactly north of center of Earth’s shadow as measured perpendicularly to the equator.

12:06—partial eclipse ends; last contact of Moon with Earth’s umbra.

13:18—penumbral eclipse ends; last contact of Moon with Earth’s shadow.

This is eclipse number 25 of the 80 in lunar saros series 140 (1597 Sept. 25 to 2968 Jan. 6).

ct. new O

w ne

eclipse season, the lunar eclipse is pary6 Ma l l u f tial, the Moon pass20 r ing well to the north ay ula M of the center of the n I . an Earth’s shadow thus R A L only part-way SO through the dark umbra. At the second season, the Moon passes an even greater distance from the center of the Earth’s shadow, but now to the south. It fails to make contact with the umbra, interacting only with the much fainter penumbra.

Of this year’s two solar eclipses, one—the annular—is the first central solar eclipse to be visible from any part of the contiguous (48) United States in nearly two decades, while the total is the first visible from anywhere on Earth in nearly 28 months, though unfortunately not from America. Of the far less interesting lunar eclipses, the May event will be visible for most of the Americas in the pre-dawn hours; in November, the Far West may get a good glimpse before moonset. But if you miss that one because of weather or

fu

s ascouthe e r norndingly orb the no it rly de orb it

new Mar. 22

1

A 4-eclipse year with variety: One annular and one total solar and one partial lunar and one penumbral.

Widespread interest is likely in advance of the annular event in May, the first central solar eclipse to cross the contiguous U.S. in nearly two decades which will also result in a widely visible partial eclipse across North America. And in November, Australia gets an opportunity to host the first total solar eclipse since 2010.

In 2012, as in most years, there are two eclipse seasons, slightly less than six months apart. (For more clarity on this see the “Pattern of eclipses” diagram on page 39 of the latest reprinting of the Astronomical Companion, which shows eclipses through the year 2021.) Shifting ever backward through the year, our first eclipse season for this year (which in 2011 straddled June-July) now straddles May-June and the other comes in November. In each of these eclipse seasons—again as in most years—we have one eclipse of each kind, thus making 4 in all, the minimum and most frequent number.

In each pair this time, it is the solar eclipse which falls nearer to the middle of the eclipse season—the moment when the line of the nodes coincides with the Sun-MoonEarth line—so the solar eclipse is central, of the annular variety in May and the more spectacular total kind. At the first

23

full Mar. 8

full Apr.

by Joe Rao

Feb.

Jan .

9

ECLIPSES

ne w

n. l Ja ful

SCHEMATIC VIEW summarizing the year’s eclipses. At each date of new or full Moon, the Earth is shown with the Moon inward of it at new Moon, outward at full Moon. The plane of the Moon’s orbit at the time is shown in blue, paler for the half lying south of the ecliptic. This plane gradually rotates backward. There is an eclipse if the Moon is full or new when it is in the ecliptic plane, that is, close to the time it crosses the ascending node of its orbit or the opposite descending node. The black arrow is the moon’s course over 7 days. The view is from ecliptic longitude 270°, latitude 30°. Relative to the Earth’s orbit, the Sun’s size is exaggerated by 15, Earth and Moon by 600, and the Earth-Moon distance by 40; the inclination of the Moon’s orbit is exaggerated from 5° to 10°.

al br 8 . 2 um ov en 3 L .N rp .1 A ov TOT IV una N R . l III LA 9 ct. 2 SO ll O

new Dec. 13

07:44

ec. 28 full D

38

01/09/2011

new June 19

ei12-1.qxd

8 hours

TAURUS

53 Tau

8 hours

ω Tau

Moon 16:53 quits penumbra

14:33 mid eclipse

12:13

touches penumbra

2012 Nov. 28 43 Tau

ε Tau Ain

07:46

Page 44

Astronomical Calendar 2012

Rig el

Bet elg eus e

Capella

SKY from Cairns, Nov. 13 20:40 UT = Nov. 14 6:40 a.m. clock time. Moon and Sun are also shown over the preceding days (Sun at 2-day intervals) to suggest how the Moon, moving 13 times as fast, arrives at the ecliptic in time to tread on the Sun. Their sizes are exaggerated by 4.

west

south celestial pole

CRUX

sout h

Wa y

10

ha ri Alpntau Ce

11

ca

Spi 12

A 13

es tar

r cu

er

M

on another f o suggestion was r l east a t . 1 6 . 5 ˚ to call it Cooksland).

S Eclipse chasers will probably congregate in Cairns (population 147,100 in 2010, and rapidly growing), which is in the totality path, only 11 mi (18 km) south of the center line. Cairns is tourist-popular because of its tropical climate and access to the Great Barrier Reef (reachable by boat in less than an hour) and Daintree National Park and Cape Tribulation (about 81 mi or 130 km north).

For Cairns, sunrise is at 5:35 a.m. local time; just 10 minutes later, first contact, when the Moon begins to dent the Sun’s disk at the 11 o’clock positionk. Over the next 53 minutes that dent grows, till the solar disk is a narrow crescent.

At 6:38:34 a.m., the last bit of the Sun’s photosphere is extinguished, the glorious corona spreads into view, the sky dramatically drops to its darkness of 30 or 40 minutes before sunrise. Totality lasts 1 minute 58 seconds, but you can extend this by 7 seconds if you travel from Cairns north to the center line (roughly midway between Clifton Beach and Port Douglas). For totality’s onset at Cairns the Sun is 13.8° above the east-southeast horizon. The umbra is now an ellipse, its major axis measuring 88 mi (143 km).

As the solar crescent dwindles, some of the brightest stars and planets will appear. Discernible several minutes before totality will be Venus, at magnitude —4.0, 32° to the upper left of the fading Sun; later, Saturn (magnitude +0.6) almost midway between Venus and the Sun; on the opposite side of the sky, but only 6° above the west-northwest horizon, Jupiter, next in brightness to Venus at mag. —2.8.

The three brightest stars will be in the sky: Sirius (—1.4) about halfway up from the west-southwest horizon; Canopus (—0.8) one-third up in the south-southwest; Alpha Centauri (— 0.3) 24° high in the southeast. The stars of Orion and his retinue may appear low in the northwest.

The shadow travels out over the Pacific with no further landfall. The 2,141 inhabitants of tiny Norfolk Island (one of Australia’s external territories) will witness a tantalizing partial eclipse of magnitude .980 at 8:38 a.m. local time as the southern limit of totality passes a mere 60 mi (96 km) to the northeast.

A few minutes later, the shadow crosses the International Date Line and the date of the eclipse switches to Tuesday, November 13.

The instant of greatest eclipse occurs at 22:11:48 UT. Duration of totality reaches 4 minutes 2.2 seconds, the Sun standing 68° above the ocean.

The path of totality comes to an end 610 mi (980 km) west-northwest of Santiago, Chile, at 23:48 UT; the umbra leaves Earth’s surface along the sunset terminator, about mid-

An

3 11 91 v7 n No Su

LIBR

n tur

Sa

Arctur us

ZE

per

Dip

l k y Mi

NI

TH

Bi g

C

9

y

Story of the shadow. The umbra first touches Earth on the UT date of Nov. 13 at 20:35, in Arnhem Land at the northeastern corner of the Northern Territory; the path is 78 mi (126 km) wide and totality lasts 1 minute 40.9 seconds. The northern part of the umbra falls on the adjacent Arafura Sea, which overlies the continental shelf between Australia and New Guinea. The North and South Goulburn Islands, in Auray Bay off the northern Arnhem Land coast, are just inside the shadow’s northern edge and lie just to the east of the sunrise terminator. The islands are Aboriginal-owned, so permits from the Northern Land Council are needed for all visitors. The Goulburn Islands are not set up for tourism, but intrepid sailors and fishermen occasionally visit.

The Arnhem Region (population 16,230) was declared an Aboriginal Reserve in 1931, one of Australia’s largest, known for its isolation and its people’s strong traditions and art. The Yolngu people of the northeast are one of Australia’s largest indigenous groups. Malays and Macassans have raded with the Aboriginals of this region since before Europeans arrived.

Darwin, capital of the Northern Territory, is 155 mi (240 km) west of the umbra’s first contact. It has sunrise at 6:11 a.m. and maximum eclipse (with a magnitude of .982) 4 minutes earlier. Thus the dawn twilight may appear unusually subdued, and when the Sun appears above the east-southeast horizon Darwin’s 124,800 may see it as a narrow crescent with cusps pointing downward. I calculate the eclipse magnitude at that moment to be .920.

The umbra takes only two minutes to cut southeast across the Gulf of Carpentaria, a large shallow bay off the Arafura Sea. The shadow’s southern edge grazes the north shore of Bickerton Island, home to an Aboriginal community of 140, then crosses the northernmost part of Groote Eylandt, owned by, the Anindilyakwa people (who speak the isolated Anindilyakwa language).

At 20:38 UT the umbra begins a two-minute passage across northern Queensland (named for Queen Victoria when it separated from New South Wales in 1859, though

us Ven

The second solar eclipse of the year is central and occurs just 13 hours before the Moon reaches perigee. That is why this eclipse is total. It will be the first such eclipse since 2010 July 11 (which, like this one, was visible chiefly over the open South Pacific). The 2012 event is confined mainly to the southern hemisphere, where the partial phases will be visible from all of Australia, New Guinea and New Zealand, as well as a part of Antarctica and a far-southern slice of South America. But totality will be seen only from a narrow corridor running southeast across Australia’s Northern Territory and Queensland. The calendar date here is Wednesday, Nov. 14.

r i z

celes t i a l equa t or

III. November 13-14—Total Eclipse of the Sun (Australia, South Pacific)

o an

8

t i c e c l i p

t eas r th

no

ho

s pu

Moon 2012 Nov 7 21h

Regu lus

nort h

Sir ius

Pro c yo n

Cast or Pollu x

sou est thw

a pocket-mirror with a piece of paper that has a ¼-inch hole punched in it. Open a Sun-facing window and place the covered mirror on the sunlit sill so it reflects a disk of light onto the far wall inside. The disk of light is an image of the Sun’s face. Farther away from the wall is better; the image will be only one inch across for every 9 feet from the mirror. st we r th Modeling clay works well to hold the mirror in place. Experiment with difno ferent-sized holes in the paper. Again, a large hole makes the image bright, but fuzzy, and a small one makes it dim but sharp. Darken the room as much as possible. Be sure to try this out beforehand to make sure the mirror’s optical quality is good enough to project a clean, round image. Of course, don’t let anyone look at the Sun in the mirror.

If you’re around leafy trees, look at the shadow cast by them during the partial phases. What do you see? Is it worth a photograph? You will see scores of partially eclipsed Suns projected through pinhole gaps between the leaves. Notice that it gets cool as the eclipse deepens. Does the wind pick up?

Acceptable filters for unaided visual solar observations include aluminized Mylar. Some astronomy dealers carry Mylar filter material specially designed for solar observing. Also acceptable is shade 14 arc-welder’s glass, available for just a few dollars at welding supply shops. Of course, it is always a good idea to test your filters and/or observing techniques before eclipse day.

Unacceptable filters include sunglasses, old color film negatives, black-and-white film that contains no silver, photographic neutraldensity filters, and polarizing filters. Though these materials have low visible-light transmittance levels, they transmit near-infrared radiation that can burn the retina. That the Sun appears dim, or that you feel no discomfort when looking at it, does not mean your eyes are safe.

Magazines such as Sky & Telescope and Astronomy will have detailed information a month or two before May. Sometime during May, newspapers, especially along the path, will bring you up to date.

To all of you fortunate enough to be there, good luck and clear skies!

Ald eba ran

44

01/09/2011

Ju pit er

ei12-2.qxd

ast the

way between the San Felix and San Ambrosio Islands (to the north) and Juan Fernández Islands (to the south). sou

Weather prospects.

Over the North Territory and Queensland, June, July and August are the dry season, with plentiful sunshine and little or no rain. January, February and March are the wet season: monthly rain totals average 12 to 16 inches (300 to 400 mm) with much cloud and humid weather. The Intertropical Convergence Zone is a belt of heavy cloud and frequent tropical showers and thunderstorms, known in Australia as the “monsoon trough,” and as the southern hemisphere summer approaches this trough is moving south from Indonesia toward northern Australia.

Also, during the summertime, a “thermal” low pressure system usually develops over the Northern Territory, contributing to mid and high level cloudiness and scattered precipitation, often affecting northern Australia. Finally, summer brings steady east-southeast trade winds, which transport humid air from the Pacific, which in turn interacts with a steeply rising coastal mountain range to generate local clouds and precipitation.

“But wait,” you might say, “the eclipse comes in midNovember, which is not yet summer but more like mid to late spring.” Yes, but it’s still close enough to the onset of summer that many of those adverse elements are beginning to build up. The situation is not as dire as for China and Japan at May’s eclipse, but, depending on your location, things can be touch and go.

Across the path of totality in the North Territory and Queensland, cloud cover averages 55.2 percent; the percent frequency of a clear sky or few or scattered clouds averages 50.5. In November, Cairns averages 55 percent cloud cover and there’s a 47.4 percent frequency of clear, few, or scattered clouds. Cairns boasts the highest number of sunny days (7.9) anywhere in the eclipse zone. The most sanguine prospect for eclipse watchers is blue skies mixed with patchy low clouds over the ocean and along the immediate coast.

One must hope that a single cloud patch doesn’t block the Sun at the magic moment. That happened to me at the eclipse of 1977 Oct. 12, at El Rosal, Colombia (see http://tinyurl.com/3z9wtpu).

The worst scenario? A cloud-filled sky thanks to a passing trough of low pressure or perhaps a trade wind disturbance pushing a moisture-laden system onshore, bringing with it not only heavy clouds but drenching showers.

So it’s a coin toss whether the weather gods will be smiling on the appointed morning. Mobility and advance knowledge of the latest weather forecasts can be the difference between thrill and disappointment.

ei12-2.qxd

01/09/2011

07:51

Page 45

Astronomical Calendar 2012

45

sun overhead

umbra

˚W 150

e of surfac mbra nu the pe

But trying to be mobile may be problematic. A marathon, of all things, is to be run in Port Douglas on eclipse day! It too will draw crowds; it may bra in 1 hour cause key roads to be closed, lastflight of the um cemter) minute maneuvers blocked.

And (relative to Eartj because the eclipse comes early in the morning, any prospective hunt for clearer sites must begin in predawn darkr n c e Ca ness. Hundreds of others may be out 2012 Nov. 13 f o there searching. So do you go out wan22:00 UT i c Hawaii p dering unfamiliar roads in the dark or r o T stay put?

Notes Jay Anderson: “ . . . you are rotation gambling on the advantages of a little r in 1 hour o bit of mobility versus playing the probaa t u eclipse e q bilities on eclipse day by remaining north ern limit of partial fixed. If, on the sunrise, it turns out that 21 :00 the other side of Port Douglas looks 22 :0 23 better, you may encounter some diffi0 :0 20 0 : 00 culties in crossing through the town in n r o i c the marathon crowds. From Port r p ntact C a Douglas to Mount Molloy, the highway f last cuombra ---o --n is a twisting, climbing road surrounded ------------ of pe i c p by dense vegetation with few outlooks o flight of first conta 30˚ r t the Earth of penum ct S toward the sea. There are almost no T es t bra---------in 1 minute ea se -------opportunities to pull over and watch r --------------------g lip ----< -- ec the sky, and since the terrain faces into = = --the trade winds, there is a high proba---23:30 23:40 --------bility of cloudiness as the air flows 23 ----las 22:30 22 21:30 tc 21 through the gap in the mountains. All-inof uomntact bra all, coast observers might be better 20:40 advised to sit and take whatever nature t ac first contbr ------offers, but it will be a heartbreaker if the of um a------eclipse is visible at a site a few hundred 0: meters away while being obscured at 00 your chosen location.”

S ˚ 0 6 Better prospects might be found C i r c l e c west of the mountains that form the t i c Great Dividing Range. Moisture from r a 23 t :0 the easterly trade winds tends to collect n 0 A on the windward side and get “wrung ˚W 90 out” on the lee or downslope western 120 W ˚E side. This favors the west side of 150 60˚ ˚E Daintree National Park. Of course, because the Sun is lower than 15°, you 120˚E 120 must take care that it isn’t behind a ica tarc 90˚E mountain or other obstruction. But staAn tistics generally show less cloud over inland areas than on the coast.

A location that stands out in this regard is Palmerville, almost on the center line and with an average cloud cover of just 32 percent, crossed Australia. It was witnessed by astronomer Glenn campaign this time; that people will be properly instructed on and 77.1 percent frequency of clear, few, or scattered clouds. Schneider, with whom I grew up in The Bronx, New York. caution during the partial phases (see our suggestions for But the problem is getting to Palmerville! From Port Glenn’s chief memories of that 1976 eclipse are of those May 20) but also that the precious moments of totality should not be missed. With the Sun itself hidden, its glorious Douglas or Cairns it’s a long arduous trek, first south and who didn’t see it! In his own words: “The path of totality passed directly over Melbourne, a corona can, without any special filters, be viewed in comsouthwest right out of the totality path before turning to the city of no small size, and should have afforded the opportu- plete safety. northwest at Almaden and back up into the path.

Saros series 133 will produce 20 more total eclipses, then Before you decide this is where you want to be, heed Jay nity for millions to enjoy basking in the lunar shadow. I’m Anderson: “Inland areas are sparsely populated, poorly sup- very sad to say, however, it was not so. Not, as some may 7 partials, the last on 2499 September 5, over Antarctica’s plied by roads, subject to flooding and closure, and not capa- come to a premature conclusion, due to poor weather, but Victoria Land.

Next year, on November 3, the path of a hybrid solar ble of handling large groups of tourists. This is not a route for due to a reign of misinformed terror foisted upon the poputhe uninitiated; service stations are non-existent. It would be lace by television stations, newspapers, kiosks, and radios all eclipse will stretch southeast from off the coast of the sensible to go with local guides. All-in-all, a grand adventure, blaring with incredulous warnings. No effort was made to Carolinas and across the North Atlantic, making landfall at educate the masses who were to be blessed with totality as Gabon and then turning east-northeast across equatorial but not one to be taken by bus-loads of casual tourists.” to how to watch the eclipse safely, and no distinction was Africa before ending over southern Ethiopia. Extraordinarily, Saros series and coming attractions: This solar eclipse is the drawn between totality and partial phases. The theme of the this eclipse is annular for only 15 seconds at the beginning 45th in a series (number 133) that started with twelve partial bureaucratic agencies “in charge” was “instill fear” rather before becoming total for the rest of the path. The duration eclipses, the first over the Beaufort Sea on 1219 July 13. than “imbue with knowledge.” Continually echoed was the of totality will reach a maximum of about 100 seconds at a Then came 6 annular eclipses and one annular-total (hybrid) mantra ‘THE ONLY SAFE WAY TO SEE THE ECLIPSE IS ON TV.’ And this point in the Atlantic several hundred miles off the coast of Liberia. eclipse on 1544 Jan. 24. Since then, there have been 25 total from the heart of the path of totality!”

Let’s hope there won’t be another “Eyes Down on E-Day” eclipses in the series. In one, 1976 Oct. 23, the path also 0˚ 180

W 150˚

W

90˚

˚W

60

˚S

0 W 150˚

0˚ 18

0 :0 22

120

Aus trali a

30˚S

Date Lne

New Zealand

0˚E 15

Locations within the path of totality. *: ***: event is below horizon. time 1st zone contact Palmerville* UT+10h *** Pt. Douglas* UT+10h 5:44 am Cairns* UT+10h 5:45 am Total solar eclipse of November 13-14 All times U.T. Nov. 13, 19:38—Partial eclipse begins: first contact of Moon’s penumbral cone with Earth, at local sunrise.

20:36—Central Eclipse begins: first contact of axis of Moon’s shadow cone with Earth, at local sunrise. Total eclipse begins slightly earlier, when leading edge of Moon’s umbral cone meets Earth.

22:08—New Moon (conjunction of Moon with Sun in ecliptic longitude): Moon’s center is exactly south of Sun’s as measured perpendicularly to ecliptic.

22:11—Greatest eclipse: axis of umbra passes closest to the center of the Earth.

22:18—Conjunction of Moon and Sun in right ascension: Moon’s center and shadow passes exactly south of Sun as measured perpendicularly to Earth’s equator.

23:47—Central eclipse ends: last contact of axis of Moon’s shadow with Earth, at local sunset. Total eclipse ends slightly later, when trailing edge of Moon’s umbra leaves Earth.

Nov. 14, 00:46—Partial eclipse ends: last contact of penumbra with Earth, at local sunset.

04:41—Moon’s center reaches ascending node through ecliptic.

10:44—Moon at perigee. 222,047 mi (357,361 km).

Nov. 17, 21:00:57—Middle of eclipse season; Sun at same longitude as true ascending node.

This is eclipse no. 45 of the 72 in saros series 133 (1219 Jul. 13 to 2499 Sep. 5).

calendar date is Nov. 14, otherwise Nov. 13. totality begins dur.

6:37:28 am 2m02s 6:38:04 am 2m03s 6:38:34 am 1m58s

last alt. contact 11.7° 7:38 am 13.3° 7:40 am 13.8° 7:40 am

Local circumstances for Nov. 13-14. * means that the calendar date is Nov. 14, otherwise it is Nov. 13. ! means that local sunset happens before maximum eclipse. !! means that the magnitude is that at sunrise; !!! means that the magnitude is that at sunset. *** means the event happens below the horizon. time 1st max. last zone contact eclipse mag. alt. contact Perth* UT+8h *** 5:09 am! .401!! .0° 5:42 am Darwin* UT+9h30m *** 6:11 am! .920!! .0° 7:01 am Adelaide* UT+9h30m 5:43 am 6:31 am .522 16.5° 7:22 am Melbourne* UT+10h 6:16 am 7:06 am .524 23.1° 8:00 am Pt. Moresby* UT+10h 5:39 am 6:33 am .808 11.6° 7:32 am Hobart* UT+10h 6:26 am 7:15 am .449 26.8° 8:07 am Sydney* UT+10h 6:07 am 7:03 am .669 27.1° 8:04 am Brisbane* UT+10h 5:56 am 6:54 am .835 26.1° 7:59 am Norfolk Is.* UT+11h30m 7:31 am 8:38 am .980 42.2° 9:52 am Santiago AST 6:50 PM 7:22 PM! .585!!! .0° *** Stanley AST 6:41 PM 7:19 PM! .345!!! .0° ***

mars.qxd

01/09/2011

54

07:42

Page 54

Astronomical Calendar 2012 ecliptic longitude

315˚ 315 +15 +15˚

300˚ 300

285˚ 285

270˚ 270

255˚ 255

240˚ 240

225˚ 225

M i l

+10 +10˚ o

OPHIU CHUS

- 20

S RNU ICO R P CA

-5 -5˚

Pluto

SCORPIUS

-10˚ -10

- 30

o

21

20

h

h

19h

Coordinates of 2012

ecliptic north pole

ional rotat Earthorth pole n

GE

CA

AR I

northernmost latitude

Nov

Dec

20

Mar 5 e lstic er so m m su

A QU

Oct

Jan

Sun

Feb

IC T IP L EC

Mar

Ea

rth Apr

A PL

Apr

q ro t au

CA P

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

RI C ORN

Jun Nov

e

Jun

Mars

southernmost latitude Dec

201 Jul 287

Jul

6 201 22 May

May

IU S

N E Aug

May 14 8 20 pr A

AR

2003 Aug 28

US

r3 12 Ma

or

equa t

Sep

aphelion

Mar

S P I S CE

ES

2005 Nov 7

De 200 c2 7 4

n 29

Feb

Mars orbits 1½ times farther out from the Sun than Earth, taking 1.88 of our years to complete an orbit. On our inside track, we take 2.13 years to catch up with Mars at the next opposition. Thus the oppositions are spaced around the sky roughly 1/7 of the circle apart, in a roughly 15-year cycle. After the opposition of 2010 Jan. 29 in Cancer, Mars spent the rest of that year semicircling around to Sagittarius, then 2011 semicircling back and a little more.

This January, as we again overtake it, Mars slows its eastward progress across the starry background and appears to swirl backward toward us, curling into the 81-day retrograde loop that is its time of prominence. It is in the part of its tilted and eccentric orbit that is northernmost (maximum latitude Jan. 8) and outermost (aphelion Feb. 15), so the loop is a northward one, and at opposition on March 3 the planet is still almost as distant as it can be, less than 14″ wide and shining at magnitude —1.2 (whereas at the near

me a n di s t a nc e

N CE R

Jan

HELIOCENTRIC VIEW of the orbit of Mars. The view is as in the Mercury-Venus picture, but with the constellations removed from the front side of the sphere for clarity. A circle on the eclipOct eq autu tic plane shows the mean distance of Mars from the Sun (1.5237 uin m a.u.). The planets are exaggerated 700 times in size. Dashed lines ox n (each dash or gap 0.05 a.u. long) connect the positions of Earth and Mars at the dates of several successive oppositions. A dotted line connects them at the date when Mars is nearest, 2 days different from this year’s opposition. Before opposition Mars is in the morning sky, and after it in the evening sky, as shown by the resphctively gray and black 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 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.

Sep

Aug

Jul

c i tp i l ce

Mar 3 0h

eq nor uatori th al

ecliptic north

ptic

Jul 1

Jun 1

May 1

Apr 1

Mar 1

Mar 3 opposition

6h 5h

9h

18h

15h

12h

------

Aug 1

ecli

4h

----

Sep 1

0h Mar 3 21h

--

Oct 1

Phobos

6h

----

----

----

Nov 1

2h

3h Mar 4 0h

1h

3h

n io --ct ---re n di Su to

----

---------

n rstio u ta ho ro n 2 i

n polorth ar c ap

3h

equatorial

Deimos MARS AND SATELLITES at opposition. Equatorial north is at top, to suit observation in telescopes.

Scale is 1 mm to 1 second. The satellites go around Mars in almost circular orbits and in planes slightly varying from its equator. They are shown at hourly intervals, 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 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: at this time the magnitude of Mars is —1.2, whereas Phobos and Deimos are about 13 and 14 magnitudes fainter.

Dec 1

14 h

A year with an opposition, of the northerly but more distant kind. This climax comes in March, after which Mars spends the rest of the year sinking in the evening sky.

ec l i pt i c

I

2010 Ja

EO

15 h

MARS

R US T AU

N MI

16 h

17 h

18h

Ma r nors rotat th p ion ole al

-15˚ -15

Sep

Antares

the Teapot

S TARIU SAGIT

A

Oct

Nov

Dec

o

LIBR

y

i p t i c

2013

SCOR PIUS

a

e c l

0˚

Nov 27

W

ecliptic latitude

+5 5˚

eT ea sp oo n

y

th

k

- 10

Feb 1

Jan 1

THE DISK OF MARS at the beginning of each month. The scale is 1 millimeter to 1 second of arc. The diagrams are oriented so that 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 planetradius beyond the surface. An arrow along Mars’s equator represents its rotation in 2 hours.

mars.qxd

01/09/2011

07:43

Page 55

55

Astronomical Calendar 2012 240˚

225 225˚

210 210˚

195 195˚

180 180˚

+1

0

165 165˚

150 150˚

+2

o

0

140 140˚ +15 +15˚

o

+10˚ +10

LEO VIR

LIBR

opposition Mar 3

GO

A

Aug 15

+ 5˚ 5

Mar

Feb

Mars

Saturn

2011

Jan

May

Ap r

2011

Regulus 0˚ e c l i p t i c

Jun Jul

Aug

Sep

Oct

Spic a

e

q

u

a

-5˚ -5

t

o

r -10˚ -10 e s ma gn i t ud

15 h

13

14 h

12

h

11

h

MAP of Mars’s geocentric track against the starry background, eclipticbased like the Mercury and Venus maps. The scale is about 2.7 mm to 1°.

The track is drawn in gray when Mars is in the morning sky (before opposition). Parts of the tracks for the neighboring years are included (in blue).

Short blue lines connect Mars to other planets when they appear closest.

pt l i ec

9 p2

op

--2

--3

-15˚ -15

e

i qu

no

x

r di

an

ti ec

0 12 24 1 0 21 20 17 14 4 12 9 2 1 22 9 21 11 5 0

r.a.(2000)dec.

11 27 41 6 41 1- au from earth 11 31 33 6 25 max.lat.north 11 34 8 6 15 stat.in long>retr 11 39 43 6 7 stat.in r.a.>retr 11 39 45 6 9 aphelion 11 28 10 7 57 opposition 11 5 38 10 21 nearest to earth 11 2 49 10 37 max.declin.north 10 28 6 12 57 stat.in long>dir. 10 25 47 12 47 stat.in r.a.>dir. 10 25 45 12 43 1+ au from earth 10 36 40 10 43 east quadrature 11 15 37 5 46 on equat.,to sou. 12 2 51 0 4 ec l inode descending 12 42 59 -4 36 pt 2.9ºS of Saturni c13 35 23 -10 17 max.declin.south 18 1 52 -24 32 4.6ºS of Pluto 18 33 53 -24 20 max.lat.south 20 19 26 -20 45 20 28 32 -20 14

hedis 1.656 1.658 1.659 1.663 1.664 1.666 1.665 1.664 1.654 1.649 1.649 1.633 1.605 1.576 1.552 1.522 1.413 1.405 1.386 1.385

gedis elo mag 1.040-110 .2 1.000-113 .1 .970-116 .0 .848-130 -.3 .841-131 -.4 .713-157 -.9 .674-176 -1.2 .674 175 -1.2 .769 138 -.6 .822 129 -.4 .831 128 -.4 1.000 109 .1 1.244 90 .6 1.447 77 .9 1.582 69 1.0 1.725 61 1.1 2.109 35 1.2 2.137 32 1.2 2.218 25 1.2 2.225 e 24 q u a t1.2 or

e

us

c

l

i

on

p

t

i

g 24

opposition Au

tu

ne

1 C ere

--1

ep

H alle y 1982

l

h

N

Jupit er opp Dec 3

Mars Jan 1 Jan 5 Jan 8 Jan 24 Jan 25 Feb 15 Mar 3 Mar 5 Apr 5 Apr 14 Apr 15 pt i c 8 May Jun 8 Jul 5 Jul 24 Aug 17 Nov 17 Nov 27 Dec 29 Jan 1

Ur

e pS

s

M ars 1P

1987 l e y Hal

op p Aposit r 1 ion 5

1P

i

or a t qu

a rn ve

5 4 3 2 11 00

TABLE OF PHENOMENA. For explanation see the MERCURY and VENUS section.

opposition of 2003 it was —2.9, nearly 5 times brighter). Since it has begun to move inward, the moment when it is nearest to Earth comes two days after opposition (this is an effect that, because of the eccentricity of Mars’s orbit, is more pronounced than for other planets).

The loop takes it back through Leo, almost to Regulus which it passed last November.

April is when we definitively leave Mars behind; we are rounding our orbit as we look farther back at it, so the apparent eastward motion against the stars resumes (stationary moment April 14) and becomes rapid, out of Leo and across Virgo and four more constellations to end the year in Capricornus. i c e c l i pt ec l i pt i c When on Aug. 14 and 15 Mars passes between Spica and Saturn (an orange point i c e c l between a white point of the same brightness and a yellow point a little brighter), this group is still about 60° up-left from the setting Sun. And not much dimmer or lower when the slender Moon climbs past beneath them a week later.

e

h

Sa

tur

n

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 nearly 18 cm (7 inches) from the Sun, approach 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.

IP L C E

TI C

N PL A

E ta

ro

opp

osit ion Ju

u

q

e

n2

9

Plu

i

i

t

p

l

c

e

to

dia” 9.0 9.4 9.7 11.0 11.1 13.1 13.9 13.9 12.2 11.4 11.3 9.4 7.5 6.5 5.9 5.4 4.4 4.4 4.2 4.2

c

01/09/2011

62

07:28

Page 62

Ju pi te r

Astronomical Calendar 2012

l ec

t i c i p

tio

n

ast12.qxd

res 1 Ce

ap

4

he

Vesta

lio

op

po

sit

n op

ion

v

n er

i e qu

al

ec di r

n ox

all 2 P

as

po

sit

io

n

on

ositi

opp

Sun

r y

nope

u Merc V enus

on

ti osi

t

ro

q au l ec

el aph

-U A

ion

ASTEROIDS For a second year, all of the “First Four” are at opposition.

In addition we feature asteroid No. 11, Parthenope.

Asteroids (also called minor planets) continue to grow in numbers. In 2010, 74,082 objects were discovered or recovered, receiving provisional designations, and as of Aug. 2011 the total of these had reached 971,095; 283,317 had received numbers (recognizing that their orbits are determined and they are unlikely to be lost); and 16,660 had received names.

The “First Four” asteroids, discovered in the first years of the 19th century, have combinations of large size and moderate distance that make them reliably observable around each of their oppositions. They travel each year very roughly a quarter of the way around the celestial sphere (Vesta more, the others less); therefore each arrives about each 3rd or 4th year in the Taurus-Gemini direction, so that it is behind us in January and still ahead of us in December—in other words it misses an opposition. This year, however, the four are spread over an approximate hemisphere, and we overtake all of them, beginning in May with: 3 Juno. Though named for the queen of the Roman gods, this third asteroid to be discovered is smaller than the others of the First Four and often less bright than several lower down the list. This is one of the most distant and dimmest oppositions for Juno, because it is at aphelion at essentially the same time (it can be 1.33 a.u. nearer to us and 2.7 magnitudes brighter, as it will be in Nov. 2018). Algol It is at the southern end of Serpens (Caput) near the Ophiuchus-

--

Aug

0h

23h

Jul

Jun

May

20h

19h 18h30m

+30˚ +30

PISCES

May

Altair 4V Apr es ta

Apr

TAURUS

Feb

May

Feb Jan

p

CETUS

Jun

Se

Rigel

M Ce ar re

s

Mira

Jul Aug

1

0˚

-10 -10˚

2 Pa Apr llas

De ul Jun cJ A ug Jan

O ct

Mar

Feb

+20˚ +20

AQUARIUS Coordinates of 2000

Fomalhaut

+10˚ +10

0˚

Jan

1 May 1 Par t hen ope Sep Apr

Nov

Dec

-20˚ -20

21h

y

Betelgeuse

Sirius

22h

Wa

ORION

ec l ipt ic

Ju n

an ar eb

declination

1h

ARIES

d Al

+10 +10˚

2h

at opposition in December. Though only fourth to be discovered, Vesta is almost equal second in size with Pallas, has a high albedo (lightness of color), and is usually closer in. So it is, at its oppositions and at many other times, the brightest asteroid, the only one that can reach the extreme naked-eye magnitude threshold of about 6.5. And it just manages that this year despite being in the outer part of its orbit (aphelion on Nov. 24). At opposition on Dec. 9, 7.3° east of Aldebaran which it passed in August, it is more distant and dimmer than in surrounding years—a tough test of its supposed naked-eye findability! The 2014 Apr. 13 opposition will be nearer and nearly a magnitude brighter, though somewhat more southerly: in Virgo, 15° north of Spica and, this time, only 2 days before and 2.5° west of Ceres. Because Vesta’s perihelion is in the Ophiuchus direction (longitude 254°) its oppositions are nearest (though southerly) when they come in May-to-August.

On 2011 July 15, spacecraft Dawn went into orbit around Vesta. See our SPACEFLIGHT section.

When 1 Ceres was discovered by Piazzi on 1801 Jan. 1, it was thought to be the missing planet that, according to the pattern called Bode’s Law, should be in the gap between Mars and Jupiter; but as other discoveries followed, it was found to be the first and largest of a new class—asteroids. Its period of almost exactly 4.6 years means that 5 revolutions equal 23 Earth-years; so its performance of 2012 repeats that of 1989, differing by only 1½ days and 1½°. It is a high northern performance, between the horn-tips of Taurus—the discovery constellation—with Ceres relatively near and bright—the best till 2018.

Vega

Oct

Aug Nov Sep Vesta

c i tp i l ce

Pleiades

Ceres

Sep

position to that of the Earth at the date; each dash or gap is 0.1 a.u. long. Oppositions shown are in longitude (date of opposition in right ascension can be some days different). When an asteroid is in the morning sky (west of the Sun) as seen from the Earth, its course is drawn in gray.

ky i l

v No Oct

El Nath

Dec

1

-

Libra border and 3° south of the equator; but Juno’s oppositions are always within about 5° of the equator because its whole orbit is, owing to the place (170°) and angle (13°) of its slope across the ecliptic.

11 Parthenope. At least three minor figures in Greek mythology were called Parthenope (“virgin face”), one of them being a Siren, a singing creature of the coasts, who was regarded as the foundress of the colony of Neapolis (“new city,” Naples). So when in 1849 Annibale de Gasparis, of Naples, discovered his first asteroid, 10 Hygiea, Sir John Herschel commented that it might have been named Parthenope. De Gasparis followed the suggestion when he discovered asteroid 11 on 1850 May 11. (He went on to discover nine altogether, the last in 1865.) Parthenope is in an ordinary Main Belt orbit. This is the nearest and brightest opposition it will have till 2031 July, though 2008 Aug. was slightly better still.

2 Pallas has an orbit which ascends across the ecliptic near where Juno’s does (173°) but at a steeper angle (35°), so that it is a sort of counter-ecliptic, tipping north of the equator where the ecliptic tips south. This is the year of Pallas’s descent. In May and June it rather slowly crosses the path of the Moon, thus getting occulted twice, before dropping through the ecliptic in July and taking the backward turn which is the beginning of a southward slide of which the middle, in September, is opposition. This is one of the mediumsoutherly, medium-distance, and medium-bright oppositions of Pallas. Four days after it, the asteroid passes close to the star Iota Ceti that marks the western fin of the Whale.

4 Vesta this year, traveling on a track inside of that of Ceres, is gradually overhauling it, and we pass both of them

3h

c

M

+20 +20˚

right 5h ascension 4h

6h

30m +30 +30˚

i pt

pl

Juno

3

SPATIAL VIEW of a sphere 3.5 a.u. in radius, from a viewpoint 10.5 a.u. from the Sun. Grid-lines on the ecliptic plane are 1 a.u apart. The path of each body is drawn for the whole year (Venus, 6 months; Mercury, 2 months). Stalks to the ecliptic plane show the body’s position at the start of each month. Where it reaches opposition, a dashed line connects its

i

e e

p op

Mars

an

Ea rth

rthe

perihelion

Pa

at

11

u eq

ion

opposit

or

-10˚ -10

SAGITTARIUS Mar

CAPRICORNUS

Feb

ec l i p t i c

Jan

-20˚ -20

e 07:28

Page 63

y

01/09/2011

a

ast12.qxd

c

W

M37

y

k

y

w s

l i

6h

10m

50m

30m 5h25m

40m

TAURUS

SERPENS

+28˚ ˚ -2˚ -2

m

21

El Nath

i p t i c -6˚

ORION

Crab Nebula

Oct 1

11

21 c1

c2

Sep 1

z

11

+22˚

-8˚ -8

30m

5h 10m NGC1746

20m

IC2162

z

i p t i c

+22˚

+18˚

11

+16˚

y3

+20˚

n

1 Nov

Dec 11 1

21 21

11

-10˚ -10 e

21

11

+18˚

Ald

1 Sep

21

11 a ˚ Aug +16 2

o1

11

21

ma g n i t u d e s

nebula

4

planetary nebula

5 6 7 8

ORION

globular cluster J320 galaxy

-0 47 -7 53

3.309 2.954

4.278 -10 10.2 1.960-170 8.3

3 Juno May 8 17 aphelion May 19 19 opposition Dec 22 13 conjunc.with sun

16 10 57 -3 46 16 2 3 -3 0 18 3 51 -13 41

3.353 3.353 3.180

2.393-159 10.2 2.373-163 10.2 4.145 -10 11.2

3 12 17 29 17 40

2.473 2.570 2.570

3.469 5 1.616-161 1.587-175

18 32 38 -21 17 22 20 8 -10 26 23 9 33 -7 11 22 57 3 -12 1

2.286 2.216 2.210 2.223

3.199 -18 11.4 2.124 -82 11.1 1.608-113 10.5 1.216-175 9.0

4 Vesta Apr 9 19 conjunc.with sun Nov 24 20 aphelion Dec 9 2 opposition 11 Parthenope Jan 16 17 2.0ºS of Pluto May 15 9 .5ºN of Neptune Jun 29 23 perihelion Sep 3 4 opposition

0˚

17h

16h

Oct

Nov SAGITTARIUS

-20˚ -20 Jan

11 Parthenope

SCORPIUS

(CAUDA)

20m

30m

10m

AQUARIUS

-2˚ -2˚

-4˚

u -6˚

-6˚ -6˚

i ° 11 35 13 7 5

0h 5m 0˚

-8˚ -8˚

-8˚ -8

-10˚ -10˚

f2

i

-10˚ -10˚

CETUS

f1

f4 f3 -12˚ -12 NGC246

-12 -12˚˚

Jun

Antares

0˚

Arcturus

8.1 6.7 6.4

Not from the stars do I my judgment pluck; And yet methinks I have astronomy, But not to tell of good or evil luck, Of plagues, of dearths, or seasons’ quality; Nor can I fortune to brief minutes tell, Pointing to each his thunder, rain and wind, Or say with princes if it shall go well, By oft predict that I in heaven find: But from thine eyes my knowledge I derive . . .

Shakespeare, Sonnet XIV

Jul

no 3 Ju y Ma OPHIUCHUS pr A Sep

SERPENS

15h SERPENS (CAPUT)

g Au

ar M

-10 -10˚

18h

d

Co o r d i n a t e s o f 2 0 0 0

1 22 0 5 21 51 5 6 39

MAPS showing paths of the selected asteroids through the year. Ticks are at 1st of each month; arrowheads at end of year. Paths are thicker where asteroids are brighter; gray where they are less than 15° from the Sun. 30m

40m

11

22 5 43 0 22 49

-14˚ -14˚

ct

2 Pallas Feb 22 14 conjunc.with sun Sep 24 22 opposition

-10˚

O 1

mag 8.8 6.7

2 Ma1y

s

gedis elo 3.849 5 1.681 178

i c

Oc1 t

section).

hedis 2.849 2.665

e

21

MERCURY

P years .08 4.60 .23 4.61 .26 4.37 .09 3.63 .10 3.84

22h25m

-8˚ -8 t

N 1 ov

21

la

r.a.(2000)dec.

2 23 29 8 30 5 44 46 25 17

e

Jan 11 30m

op e

11

11

al P

PHENOMENA (for explanation see the 1 Ceres Apr 26 9 conjunc.with sun Dec 18 6 opposition

Q a.u.

2.98 3.41 3.35 2.57 2.70

-8˚ -8

-12˚ -12

t1

+14˚ +14

a a.u.

2.77 2.77 2.67 2.36 2.45

LIBRA

2

discov. diam. q km a.u.

1 Ceres 1801 952 2.55 2 Pallas 1802 524 2.13 3 Juno 1804 274 1.99 4 Vesta 1807 512 2.15 11 Parthenope 1850 150 2.21

˚ -6˚ -6

21

1 Se p

p 45m NGC7492 0˚

name

1 11 Jun Pa r th en

-14˚ -14

p2

Orbital and other facts. q: perihelion distance. a: mean distance.

Q: aphelion distance. e: eccentricity.

P: period, in years. i: inclination.

l i p

11

f2 f1

c

11

t2

FINDER CHARTS on larger scale (0.75 cm per degree) for asteroids around the times of their oppositions. Position at 0h UT of each day (7 p.m. Eastern Standard Time of the previous day) is shown by a dot sized for brightness. The t e s o f 2 0 0 0-2˚ d i n a white Co o r sky, dots are gray when the asteroid is in the morning in the evening sky (into which the asteroid passes at or near popposition).

Stars are plotted from the Hipparcos cat1 alogue. Projection is azimuthal-equidistant: angular direc-4˚ -4 tions and distances are true from the middle of the chart.

open cluster

40m

21

Sep 1

Coo r d i n a t e s o f 2 0 0 0

2

50m

e

De 1 c

AQUARIUS

o2

3

k

l

qq21 r

ORION

d2

-12˚ -12˚

eba ran 1s

+14˚ +14

1 21 cJul

y2 y1 NGC1647

4 Vesta

11

11 23hFeb 1

10my

c

-8˚ -8˚

+20˚

21

AQUARIUS

1 2O 1ct

f

2

TAURUS

Oct 1

OPHIUCHUS

1 120m

-4˚ -4

Coo kk1 r d i n a t e s o f 2 0 0 0

i

z

m

21

25m u

-2˚

21

Sep 1

1 g 1 Au1

+22˚

50m

e c l

Crab Nebula

4h40m

Ju 1 l

11

+20˚

Co o r d i n a t e s o f 2 0 0 0

15h30m 0˚

21

11

e

21

+24˚

40m

(CAPUT)

Jun

11

yd Ma1

-4˚ -4

e c l

21

42m

c1

+26˚

21

1

11

11

1 Nov

n +20 ˚

Dec 1

M35 b

+24˚

Tejat Prior +22˚

es

er 1C 11

GEMINI

o Jun

3

1 Apr

+26˚

16h e q u a 50mt o r

10m

20m

30m 0˚

b El Nath

+28˚

63

Astronomical Calendar 2012

Au 1 g

20m

M

25m

k

-10˚ -10

Jan

LIBRA

c pt i ec l i -20˚ -20

For more information about asteroids: The Minor Planet Bulletin of the Association of Lunar and Planetary Observers, www.minorplanet.info. And the Minor Planet Center, http://cfa-www.harvard.edu/iau/mpc.html.

r

q

Page 82

ets

Ur ses an us se ts

es

i

ris es ut o

sets

Pl

5 p.m. clock time

lminates

full Moon culmin

ates

full Moon rises

last-quart

er Moon

last-quarter Moo

n rises

Sun transits

rn tu a S

P

es ris

full Moon sets

culmina tes new Mo on rises

s et s s ar

April

2

R

C

U Q A

0 1

11

Saturn opposition

S

E

C

Lyrids

S

IE

21

IS

P

2

A

1

August

11

0

1

O

E

L

rs

1

September

f o

l a re e d si

se ts

ets

rn

rs s

sr ise s

e

n tu ep N

u Pl

Sun transits S U

21

6

21

8 1

Perseids

R E

to lu

es ris

P

u

h 2 1

C

21

A

0

1

Alpha Aurigids

1

Sep Epsilon Perseids 11

O

E

L

G

IR

V

21

Uranus opposition

2

1

1

Southern Taurids

4

1

Orionids

A

IB

L

14

15

16

17

18

19

20

21

22

0

1

2

3

4

5

ris es

8 a.m. clock time

se ts us Ur an

23

Pl ut o

ise s Sa tu rn r

se ts to Plu

ets

U

13

r te pi ts u J se

Ursids

6

7

8

9

21

1

A

IB

L

S IU P R O C S

10

11

11

R

21

1

s

12

Geminids

ise yr

1

ur erc

21

h 8

1

Leonids Leo nids

M

11

Alpha Monocerotids Jupiter opposition

ts Mercury se

December

u

o

f o

J

es

rs

1

Northern Taurids

Ne pt un

S

r ite p u

Mars sets

O C

21

l a re e d si

ses

P R

5 p.m. clock time

1

e m ti

s ri

S IU

6

ra nu Sa sr tur ise ns s ets

11

es ris

u Ven

November

1

O G R 4 I 1 V

6 1

Ne pt un er ise s

R

Mars rises

October

Draconids

Sun transits

1

21

11

C

N

Neptune opposition

O

11

1

I IN 11 M E G

Delta Aquarids

e m ti

o

21

4

R U A T

ts se

Jup Alpha Capricornids

21

11

ite

Ur

ts se

to

ts se

11

1

rr

an

ise s

us

r is es

Pluto opposition

Ve nu

N

Sa tu

Ma

Jup ite r se ts

5 p.m. clock time (summer)

ry cu er

M

21

11

June Bootids

S IE R A

Mars r ises

1

C

R E C N A

es ris

Venus sets

21

8

Sun transits

July

11

ne tu p e

8 a.m. clock time (summer)

ts se

ris es

Ur an us

Sa tu rn

May

1

n Ve

Eta Aquarids

es ris

21

s et

s us

ry cu er

11

l a U re R e U d A si T f o rs u o h 6 I IN M E G

e m ti

M

June

4 S

1

1

21

1

21

21

11

R

11

11

A

S IU R A

2

21

1

2

P

21

0

2

O IC

1

11

11

S U N R

M

Mars opposition

ts

S E C S I

21

first-quarter Moon

first-quarter Moon cu

s se

February

S IU e R m A 2 ti 2 U l a Q re A e d si f o rs u o h 0

new Moon sets

u Ven

March

19

ts se

11

18

ry cu er M

1

P A

se ts

C

21

17

Plu to

21

11

16

s rise

January

0

2

1

15

S U N R O IC R

ry rcu Me

11

14

Ne pt un

13

1

se ts

local mean time

12

Ne pt un er ise s Ur an us Sa ri s tu es rn

This hourglass shows times when the Sun, Moon, and planets rise and set, for latitude 40° north, longitude 0°. (They differ little for other longitudes, much more for other latitudes.)

These are local mean times; to adjust them to your clock time, see the “Personal Reminder” on the preceding page.

The lines representing days (actually drawn only for days 1, 6, 11, 16, 21, 26 of each month) begin at midnight, which is in the middle because we choose to show night rather than day undivided. Each day-line ends at the point where the next day starts, so there is really just one time-line, a cut and 2012 flattened helix.

Ju Ven pi ter us rises ris es

RISING AND SETTING

the times of sunset and sunrise would be if the diagram were plotted to apparent (true solar or sundial time, in which days vary slightly in length) instead of mean time. Again, the difference is the “equation of time.”

At a planet’s opposition it is up all night (roughly) and none of the day.

Meteor showes are marked at the local times when their radiants are highest.

Two thick vertical lines displaced to the left in summer represent 5 p.m. and 8 a.m. by the clock (for places on the meridian of their time zone). This shows how the purpose of setting clocks back from standard to “daylight-saving” time is to approximate to the earlier rising of the Sun. In summer we call the true 7 o’clock “8,” the true 12 “1,” etc.

3 4 5 6 7 8 9 10 11 12 1 Quadrantids

The dark zone down the middle is night, between the curves of sunset and sunrise. The three bordering gray bands are the times of civil, nautical, and astronomical twilight, which are defined as being when the Sun is less than 6°, 12°, and 18° below the horizon.

Slanting lines show the hours of sidereal time: that is, which hour of right ascension is on the meridian. Thus 0h-1h sidereal time is the “Andromeda Hour,” when that gore of the sky is highest. Sidereal hours are 10 seconds shorter than clock (solar) hours and thus fall 4 minutes earlier each day.

The times of the Sun’s transit across the meridian are shown by orange spots. This time differs from mean noon by the amount called the “equation of time” (see the GLOSSARY). Orange curves show where 2 1 0 20 21 22 23

8 a.m. clock time

Astronomical Calendar 2012

M ar sr

82

07:07

ite rs et s

01/09/2011

Jup

risset.qxd

11

1

11

21

8 1

12