June 2012

JUNE 2012 ISSUE

Pa g e

8-9

THE NIGHT SKY Page 1

IN JUNE

0– 11

CASSIOPEIA AN OBSERVERS GUIDE 6-7 Page

4 Page

-5

EDITORIAL

So exam season is over for all those on the Observational Astronomy course, and what a good feeling it is.

This month is an exciting one with the historical transit of Venus Editor: Chloe Partridge

across the Sun on the 6th of June. The observing session for this

Copy Editor: Martin Griffiths

event we be being held on the 6th of June at 4.57 am—further

Contributors: Chloe Partridge, Chris O’ Morain Columnists: Phill Wallace, Martin Griffiths

details can be obtain from Martin Griffiths himself.

We also have an interesting article from Chris O’ Morain who has been working tirelessly this year with some of the top astronomers in the country to help uncover some of the mysteries about Wolf-Rayet stars. His article introduces some of the exciting new work he is undertaking in this field and highlights his hard work.

Enjoy the glorious weather this month, lets hope it stays….

If you would like to contribute in any way, either by sending us your Faulkes images, or perhaps even writing an article , then get in touch, we would love to hear from you.

Editorial Contacts : 10017607@glam.ac.uk mgriffi8@glam.ac.uk

IMAGE REFERENCES: PG 4-5. Solar System - www.scenicreflections.com, Colliding planets- www.gemini.edu, Planets accretion model - hartm242.wordpress.com PG 6-7. Cassiopeia - wiki common, The Queen of Ethiopia— www.constellationsofwords.com, Elk hide - tipi4u.com, M103 apod.nasa.gov, M52 - messier.seds.org PG 8-9. Venus, Lyra, M57 - Martin Griffiths, Night sky - Heavensabove.com PG 10-11. HD 192641, WR 136, HD 193793 - Chris O’ Morain PG 12. Archimedes - personal.maths.surrey.ac.uk

GLMAORGAN ASTRONOMY

JUNE 2012 ISSUE

CO SMO L O G ICA L

N EW S

4-5. SOLAR SYSTEM FORMATION

4-5

– THE TRUE STORY W E TA KE A L O O K A T TH E EA R L Y S O LA R S YS TE M A ND TH E D IFFE RE N T M ODE LS USE D TO DES C RIBE I TS FORMA TI ON.

6-7 6-7. CASSIOPIEA D ISC OVE R THE M Y TH OL OGY OF ONE OF THE M OS T FA M OUS C ON S TE L LA TI O N S A N D TH E S TA R S W H I C H MA KE I TS D I S TINC TIV E ‘W ’ S HA P E.

8-9 8-9. THE SKY IN JUNE W E TA KE A L O O K A T TH I S M O N THS N I G H T S KY W I TH TH E E XC I TI N G V E N US TRA NS IT.

10-11 10-11. WOLF-RAYET STARS TH I S M ON TH , W E TA KE A N I N TR O D U C TO R Y L O O K A T TH E R A RE W OL F - RA YE T S TA R .

COSMOLOGICAL NEWS

Page 4

SOLAR SYSTEM FORMATION – THE TRUE STORY

Humans have long wanted to know where we

caused shockwaves that made some areas of

can be addressed, we must first examine the

came from; it has been one of the most oft-

the cloud slightly denser than others. These

contents of the solar system.

asked questions in history. Inevitably, once we denser regions pulled in more and more matstopped thinking of the Heavens as eternal and ter over millions of years, getting smaller, unchangeable, we began to question where

denser and hotter. Eventually, a critical point

they had come from. The vague philosophical

was reached, and the pressures and tempera-

questions were refined into hard scientific

tures at the heart become high enough for

quandaries: “How did the Sun form? How did

hydrogen to fuse to helium. And so our sun

the planets form?” These and more questions was born. would be answered, with varying degrees of

Aside from the Sun, the largest and most influential objects are the eight major planets.

Four small, rocky worlds close to the star, three of them with atmospheres (Mercury’s gravity is too weak to hold one). Two of them have moons, and one of them has life. They are rich in metals and silicates. Two of them

This has been the dominant model for the

(Mercury and Earth) have intrinsic magnetic

formation of the Sun (and by extension, all

fields to shield them from the harsh solar

The first question, how the Sun formed, is

stars) for decades: during the 30’s Arthur

winds.

relatively well understood by astrophysicists.

Eddington suggested that perhaps heavier

To answer it, we need to go back in time: Five

elements were made in stars, and Fred Hoyle

success.

Out beyond the rocky planets are the mighty Gas Giants, with Jupiter being foremost billion years ago, the solar system did not took this idea to heart in the 50’s, when he amongst them. Jupiter is nearly a failed star exist. Its current position was occupied by a worked out with exacting detail how all the in its own right, making it almost a companion vast cloud of relatively cool gas and dust. The elements up to Iron could be formed in fusion for the Sun rather than a follower. Jupiter masses more than all other planets combined, cloud would have contained mostly Hydrogen, reactions. This model finally supplanted the dwarfs them all in size and influence. Further with some Helium and trace quantities of Lithi- 19th century ideas that the Sun was mostly a out is Saturn, famous for its beautiful rings. um and the heavier elements. ball of Iron surrounded by a layer of combustBeyond Saturn are Uranus and Neptune; faint, ing Hydrogen. And so the first of the great distant and hard to see. Uranus is best-known This enormous cloud was the grave of countquestions was answered. for its extreme axial tilt, so much so that it’s less older stars. As they burned through their The question of the planets forming is a much orbiting the sun on its side, rolling along in its fuel and died, they ejected vast amounts of orbit. Neptune is the most mysterious, with unused Hydrogen and lesser amounts of heav- more complex, and much more hotly debated little known beyond basic measurements. ier elements like Helium, Carbon, Oxygen and issue. There have been three main models Silicon. This cloud would have drifted for eter- proposed over the years: Capture, Collision nity if not for yet more supernovae, which

and Accretion. But before any of these models

JUNE 2012 ISSUE

Aside from the planets, we also have various

Page 5

The second model is the Collision model. It

plane (within a degree or two). All the planets

fragments and leftovers; the dwarf planets, the hypothesises that the planets formed from a

except Venus and Uranus rotate anticlockwise

asteroid belt, the Kuiper belt and the comets of series of collisions between smaller bodies. In

as well. Only if they all formed from a single

the Oort cloud. Most of these are cold dead

each case, the rocky fragments collide and

large disc can this regularity be explained.

snowballs (the comets) or rocky or metallic

combine, leaving a larger fragment. Over time,

fragments. The dwarf planets are larger than

this leads to larger and larger planetoids, until

most asteroids, and have pulled themselves

they become large enough to pull themselves

into spheres, but they remain in the hazy region into spheres under their own gravity. This modbetween planets and smaller bodies.

The first model, the Capture model, is the simplest. It posits that all the planet’s did not form in the Solar System, but formed elsewhere and were “captured” gravitationally by the Sun, pulling them into orbits around it. In essence,

el’s biggest failing is that it cannot explain how the gas giants formed. The gas giants, those great balls of hydrogen and methane, could not have formed from collisions. And so, a third model is needed to explain the planet’s for-

failed to escape and stayed for good. It’s a reasonable model, and does explain some of the curious anomalies that crop up, like Uranus’ axial tilt and Venus’ retrograde rotation.

But the Capture model falls down in two key areas: it does not explain the similarities shown by the other bodies, and it does not account for assuming they flew in from sources unknown, the capture model aptly describes the solar system’s formation but not the planet’s themselves.

formed further out than the rocky planets.

Closer to the Sun, the temperature would have been too hot complex molecules to exist, so it would have been solely metals and silicates, forming the rocky planets. Further out, it was cool enough that molecules such as ice and methane and ammonia could form, as well as gaseous hydrogen and helium.

mation.

this model says planets are giant comets that

how the planets formed in the first place. By

This model also explains why the gas giants

Artist's conception of planets forming by accretion

Of these three models, the Accretion model has the fewest flaws and offers the fullest explanation, and that is why it is currently the accepted model for planetary formation. This will likely change in future however, as new discoveries are made that force astronomers and geologist to challenge and discard their hardwon theories. Telescope images of dust rings around young stars in the Orion Nebula are sure to feature prominently in the future of this field, as they provide a chance to see today what happened all those years ago.

This third model is known as the Accretion or the Nebula theory. It states that when the sun formed, it left behind a vast disk of gas and dust. As with the nebula that spawned the Sun, this disc had density variations that led to small planetoids forming, that then scooped up more dust and gas until the planets existed as we know them today and the orbits where clear and empty. This model neatly explains why there is so much regularity in the solar system: viewed from above the Sun rotates anticlockwise. The planets orbit the Sun in an anticlock-

Artist's conception of two planetoids collid- wise direction. All the planets are in the same ing

BY PHIL WALLACE

COSMOLOGICAL NEWS

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CASSIOPIEA THE OBSERVERS GUIDE

The night sky as we know today it holds many of 5 stars, the distinctive ‘W’ shape of Cassiope- which it is named after, though the area is surcurious tales and answers, not only to the exist- ia sits opposite the Big Dipper in the sky, with rounded by many other stars that don’t make up ence of the constellations which are scattered Andromeda on its South side and Cepheus above the constellation itself. The region of sky dediacross it, but also to the formation of the stars it in the North.

cated to Cassiopeia comprises of the five main

that lie within those constellations. In total there

stars Epsilon (ε), Delta (δ), Gamma (γ), Alpha

are 88 constellations which make up the Northern and Southern hemispheres of the sky, but one of the most easily recognisable is the Northern constellation of Cassiopeia. Consisting

THE QUEEN OF ETHIOPIA

The western night sky today follows a grid like system where by the sky is divided into regions named according the constellation which lies within it. Each segment division acts like a

(α), Beta (β); and also Eta (η),Kappa (κ), and Lambda (λ), Iota (ι), Theta (θ), Omicron (o), and Zeta (ζ) - stars which surround the

boundary containing only that constellation constellation. of such divine beauty that she surpassed even

cently slain head of Medusa, Perseus killed

Poseidon’s daughters, the Nereids – the sea

Phineus, Cepheus and Cassiopeia leaving their

nymphs. The enraged Poseidon tied Cassiopeia’s bodies to be placed in the sky by Poseidon. In a

Like many constellations in the sky, Cassiopeia’s daughter, Andromeda, to a rock at sea awaiting final act of vengeance, Poseidon placed Cassioa monster. Perseus, the Hero famed for slaying peia in the sky next to her husband, where she name and shape is based upon ancient myths and tales. The most famous myth of all origi-

the Gorgon Medusa, is greeted by the sight of

would circle the celestial pole forever, some-

nates from the ancient Greeks, who claimed that Andromeda on the rock on his return home from times hanging upside down as punishment for his heroic killing of the Gorgon. Wanting to res- her vanity. There are many variations to the the ‘W’ shape of Cassiopeia represents the eponymous Queen of Ethiopia on her throne,

cue her he struck a deal with Cassiopeia and

story of Cassiopeia throughout history from

placed there by Poseidon (the Greek God of the

her husband, King Cepheus: he would be allowed storyteller to storyteller. Some Greek tales tell

Sea) as punishment for her vanity. The myth

to marry Andromeda if he could rescue her and of Cassiopeia being a consort to the God Zeus

describes how Cassiopeia claimed that she was kill the sea monster. Perseus triumphed in his and having a son named Atymnios, instead of a battle with the monster and as promised he was daughter. In this version of events there was allowed to marry Andromeda. However, as the

never the mention of a ferocious sea monster

wedding began, Phineus, who was previously

nor the slain head of Medusa, and there is never

engaged to Andromed, entered the proceedings an betrothed uncle. Although Roman and Greek and demanded that he rightfully be allowed to

Mythology are very similar of the story of Cassi-

marry her instead. Cepheus and Cassiopeia

opeia, in the Roman Mythology Poseidon is

immediately sided with Phineus, leaving Perseus known as Neptune, and is the God of both sea outnumbered and with only one option if he

and water, and in some cultures the tales are

wanted Andromeda for himself. Using the re-

told very different altogether.

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JUNE 2012 ISSUE

To the Quileute people of native America, this

the youngest brother came across the wise old in one mighty heave he tossed the hide into the

constellation represent the hide of a giant elk,

man, he was not fooled by his generous offer of sky, where it still remains— the W shape we see

which is based on the story of 5 brothers. In the better arrows. He declared that his were wor-

being the light from stars shining through the

story, four of the five brothers set out in

thy of his own hard work and having made them hide where it had been pinned.

search of some game, only to be fooled by a

he would use them to kill the elk and no other.

wise man beside the river who offered to help

The wise man pretended to go in search of the

the brothers if they traded their arrows for

elk to help the youngest brother, but no sooner

some better ones which the wise man had on

had his head turned but the wise old man trans-

him. Thinking this was a kind gesture the broth- formed back into the giant elk that had killed his er accepted. However, only moments later the

brothers, and charged the remaining one. How-

wise man turned into a giant elk and stampeded ever, as the youngest brother had not traded the brothers—his generous trade in arrows

his arrows, he was able to kill the giant elk. He

being useless as they merely bounced off the

took the carcass home and spent the entire

elk. Eventually when the brothers did not return night preparing the meat from it. As he began to the youngest of the 5 brothers, who had stayed stretch the hide, pinning holes around the edge, behind, went in search for them. However, when he realised how far the elks hide stretched and

DEEP SKY OBJECTS

ready used up the fuel in their core and explod- way to us from the cluster. The cluster spans a

ed into a supernova. 10,000 light-years from The most interesting of the objects contained in Earth and a staggering 14 light years in diameter the region of sky denoted as Cassiopeia is the light from this cluster is only visible with Messier 52 and Messier 103, as when resolved it can be seen that both are in fact open clusters. Binoculars as the light is so dim with an apparent magnitude of +7.4.

Messier 103 is a 25 million year old open clusMessier 52 is a young open cluster (of ter which was first discovered by Pierre MĂŠTrumpler type I2r) which was first discovered in chain in 1781 . The bright blue stars highlight the 1774 by Charles Messier. The 35 million year old open cluster, though the gas from which these cluster is 5000 light years from Earth, however stars condensed has long since dispersed. The there is uncertainty in this value mainly due to brightest, bluest stars in the cluster have althe high absorption of interstellar light on its

region of space some 19 light years in diameter.

Although it cannot be seen with the naked eye as it has a poor apparent magnitude of +7.3, it can be easily seen with binoculars. M52 can be found quite easily by following along the straight line of Cassiopeia Alpha through Cassiopeia Beta just off the end and upward, slightly to the North east. The bright, yellow-looking star a little right of centre in M52 does not belong to the cluster, it is the Bubble Nebula.

BY CHLOE PARTRIDGE

COSMOLOGICAL NEWS

Page 8

The Night Sky in June June is usually a bad time for astronomy in Britain as the darkness closes in after midnight and twilight arrives just a few short hours later. Nevertheless, Mars and Saturn put on a great display in the late evening and some wonderful double stars are on display for those who wish to hunt them down.

Moon In June This month there is a partial eclipse of the Moon – unfortunately it is not visible from the UK. The thin last crescent moon accompanies Venus in the early morning sky on the 18th June.

First quarter: 27th June Full: 4th June Last Quarter: 11th June New: 19th June

Planets in June: Mercury: Is an evening object briefly after Jupiter: Is in Taurus and is an early morning telescope. Look for the Cassini division in the rings and any satellites or shadows cast by the encountering the sun on the 27th May. It is in the object toward the end of the month. constellation of Gemini, very close to the NW rings. horizon.

Uranus: Is a morning object but due to the lighter mornings, it becomes very difficult to see unless its exact position is known or can be found by GOTO. It is magnitude 5.9

Venus: becomes a morning object later in the month but undergoes the last transit in its current 8-year pair on the morning of the 6th June.

The sun rises at 4:57am locally with the transit almost completed. 3rd and 4th contacts should be visible!

Neptune: is also a faint morning object in Aquarius shining at magnitude 7.9 but is not well placed in the bright morning sky

Mars: Is still visible in the evening sky in Leo and diminishing in brightness throughout the Saturn: Transits before midnight and is visible month as it nears the horizon. It should be mag- all month as a bright star to the NE of Spica in Virgo. The rings are plainly visible through a nitude 0.2 and glow with a dull red colour.

Constellation of the month: Lyra This outstanding Summer group is one of the most easily recognizable constellations in the sky, hanging like a jewel close to the Milky Way. Lyra, the "Lyre" apparently is a group that celebrates the invention of this musical instrument, or as legend would have it, represents the lyre of the famed musician Orpheus; his music was endowed with such power and beauty that he could enchant man and beast with his playing.

so much. Pluto relented, under the condition that Orpheus did not look behind him as he travelled up into the world of men again.

Orpheus disobeyed and turned and looked back just as he was about to step out of the cave leading to the underGood musician though he was, he was not much world, and lost Eurydice, who of a listener, as the tale of Orpheus and his wife was following him, forever Eurydice bears out. Briefly, Eurydice died, and due to his lack of trust.

Orpheus begged Pluto, the ruler of the underworld to release her from death, as he loved her

JUNE 2012 ISSUE

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The sky in June: The sky as it would appear at 22:00 on the 10th

Orpheus then threw away his lyre and vowed never to play again as penance for his sin. The lyre was taken up by the god Apollo and placed in the sky in honour of Orpheus' music.

In the late Summer nights it hangs right at the zenith, with the wonderful blue - white star Vega sparkling in the languid air. Vega is one of the closest stars to our solar system, lying 26 light years away. It is an A type star shining with 60 times the luminosity of our Sun and has twice the diameter of our star. This is one of few stars which has a circumstellar band of dust, which astronomers theorise may be collapsing to form some kind of solar system.

seus, except that in this instance, the components are almost touching one another and are surrounded by streamers of hot gas thrown out by perturbations in the system. The brightness range is not large however, and could be described as a good test of your visual discernment, as the system fluctuates between magnitude 3.8 and 4.1 in a period of 12.9 days. Beta Lyrae is a giant star lying just over 800 light years away.

Scan the field between the two bottommost stars of Lyra with binoculars, and halfway along a line drawn between the two you may just see a faint round reddish ring of light, looking like an out of focus star. This is revealed by a small telescope to be the outstanding planetary nebulae M 57, the Close to Vega is an exquisite double star, Epsilon "Ring Nebulae". This is one of the showpiece Lyrae, commonly called the "double, double". The objects of the Summer sky, the only other planetwo main components are easily separated in tary that can really compare with it is M 27 in binoculars, whilst a small telescope will resolve Vulpecula, but through a small telescope, M 57 is the two main stars into a further two binary a captivating sight. It appears as a reddish systems. This is an incredible sight in such an purple ring of seventh magnitude light almost like instrument; all the stars are a wonderful electric blue in colour, despite being catalogued as M57 The Ring Nebula A type white stars. The close companions look like little sparks of light in a system that will take high powers very well. Epsilon Lyrae is approximately 180 light years away.

The beautiful variable star Beta Lyrae is one that can be well observed with binoculars. Beta is an eclipsing variable, much like Algol in Per-

a discoloured polo mint, as the central "hole" is clearly visible as a dark inner ring within this disarming little object. The central star has a magnitude of 14, so is not visible in modest amateur equipment, but the ring of gas is unmistakeable, unlike any other planetary in the heavens.

This bubble of gas was formed when a Sun - like star puffed off its outer envelope as it reached a point of dying after the onset of Helium burning.

Exactly how the envelope is projected into space is a minor mystery, but this ejected shell is visible due to the huge amount of ultraviolet radiation pouring out of the white dwarf central star, causing the gas to fluoresce. M 27 lies at a distance of 1400 light years, making the planetary disc roughly half a light year across. This gaseous bubble is an ethereal object and will probably disperse in 20,000 years, which on an astronomical timescale is very short indeed. We are therefore privileged to witness this wonder of stellar nature.

BY MARTIN GRIFFITHS

COSMOLOGICAL NEWS

Page 10

Wolf-Rayets are an end stage massive star that spectra, while most stars present absorption

As a result of their hot temperatures, wind &

have evolved from O, B & Luminous Blue Varia- line spectra as a result of their overlying ele-

mass loss, they recycle their elements and

ble class stars, these stars are extremely rare ments absorbing energy at specific frequen-

metals back into the interstellar medium by

as we are currently aware of only around 350

cies, these stars presented Doppler broadening radiation pressure. This process of recycling is

in our galaxy and 50 in the Local Group. They

along the helium, carbon, oxygen and nitrogen

were first discovered by French astronomers

lines which indicated they were an unusual type tary development in the Universe, we theorise

Charles Wolf & Georges Rayet, for whom this

of star.

class of star is named after, who were using the 40 cm Foucault telescope at the Paris Observatory in 1867, for their observations. What made these type of stars stand out were that

that the greater development of Population I

Over time, we have come to understand more about these type of stars and what makes them uniquely interesting. They are rare stars that have primarily exhausted their hydrogen enve-

they presented broad emission lines along their

an important aspect of new stellar and plane-

lopes, with the few exceptions among the newer members of this class. Wolf-Rayet stars are very massive, with

type stars and planetary bodies we have seen in the vicinity of Wolf-Rayet stars are a direct result of the spread of these elements among the ISM, into star forming regions and contributing to protoplanetary disks. More so than any other class of star, outside of supernovae, these stars are the biggest contributor of core elements being recycled into these astronomical bodies.

masses ranging from 20 A secondary result of the wind & mass loss is to 250 M⊙, and very hot the creation of circumstellar shells and nebuwith temperatures rang- lae around most of the known Wolf-Rayet stars. ing from 25,000-100,000 We observe these to measure how much mass K. And they have fast

is shed from these stars and how fast, or in the

mass loss rates, they

case of binary systems the wind-wind interac-

lose their mass rapidly

tions of the Wolf-Rayet and its binary partner

by means of a strong

which are typically O class stars, though there

stellar wind at speeds of are a few known Wolf-Rayet-Neutron star bina-

HD 192641, one of the first Wolf-Rayet stars discovered by the French astronomers Charles Wolf & Georges Rayet. Not as visible in this optical image is the nebulosity which is common to Wolf-Rayet stars, this lays just inside the circumference of the white outline. (O'Morain. 2011.)

2000 km/s. While our

ry pairs, as a result of this we can see temper-

own Sun loses approxi-

ature change from ionization and excitation,

mately 10

−14

M⊙ every

year, Wolf–Rayet stars typically lose 10 year.

−5

M⊙ a

change in physical characteristics or what stage a Wolf-Rayet star is in its short life, by astronomical terms.

JUNE 2012 ISSUE

Page 11

WR 136 is a transitional staged Nitrogen rich Wolf-Rayet that also presents hydrogen emission lines (h) which is an unusual characteristic for a star that has exhausted its hydrogen. This star (centre image) presents a circumstellar shell and a large expanse of nebulosity, clearly seen in this negative Ha image. (O'Morain. 2012.)

HD 193793 is a late staged Carbon rich Wolf-Rayet that presents a peculiar spectra (p) which indicates it has an unusual metal abundance. This is a false colour image outlining temperature variation in the circumstellar shell & nebula around it due to excitation & ionization. This star has also presented a systematic broadening of its shell & nebula as a result of its strong winds and mass loss. (O'Morain. 2011.)

Physical Properties

than a WN7 coupled with a WCE spectrum.

Wolf-Rayets are identified by two main se-

The WN & WC classes are further classified by

quence types; WN in which helium & nitrogen

their stage of high or low ionisation, with high

lines dominate as well as displaying core hy-

ionisation types being designated as Early (E)

are the most dominant feature and the rarely

identified by low ionisation in the (He I & C II)

not typically show Fraunhofer lines (spectral absorption & emission lines discovered by physicist Joseph von Fraunhofer when observing the spectrum of our Sun.) of photospheric

origin. Because of this, they are typically clasdrogen burning properties & WC in which heli- and low ionisation designated as Late (L) types. sified by their emission lines, though their The WNE subclass (WN 2-5) are identified by um, carbon and oxygen lines dominate. They classification is not dirtectly coupled to the are absent of the core hydrogen presence of emission of high ionisation in the (He II, N v & O stellar parameters of temperature and lumithe WN types as the hydrogen has exhausted VI) range while the WNL subclass (WN 6-9) are nosity. There is much still to be discovered itself and have evolved into a primary helium identified by low ionisation in the (He I and N III) about W-R stars. The next few years should range. The WCE subclass (WC 4-6) are identiburning core. There are two less populous produce exciting new research that may fill fied by high ionisation in the (He II, C IV & O VI) sequence classes; the WO subtype which is current gaps in our knowledge range while the WCL subclass (WN 7-9) are similar to a WC but in which the oxygen lines seen WN+WC type which is a Wolf-Rayet transi- range. In this subclassification, the WN 5/WC 6 tioning from the WN class with the nitrogen & are the transitional phase star as they tend to helium lines into a WC class with the carbon,

present properties of both Early & Late sub-

helium & oxygen lines. This subclass displays

classes and have members in both groups.

properties of both H & He core burning emis-

As Wolf-Rayet stars lie inside optically thick sions and spectrally appears as being no later stellar winds and shells of gas & dust, they do

CHRIS O’ MORAIN

εὕρηκα [Eureka!] Archimedes

BSc (Hons) Observational Astronomy