Star Physics25 C

8/9/2019 Star Physics25 C

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Floravil M.Serna

BBA-Management III

Reference:

Star Facts: The Basics of Star Namesand Stellar EvolutionThe ealth! Eating Trends "f#$%& 'The (ail! )estern*+! ,harles . ,hoi S/ace.com ,ontri+utor 0 (ecem+er %1 #$%2 $3:2%/m ET

Credit: University of Leicester

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Stars are giant luminous s/heres of /lasma. There are +illions of them 4 including our

o5n sun 4 in the Mil6! )a! 7ala8!. And there are +illions of gala8ies in the universe.

So far 5e have learned that hundreds also have /lanets or+iting them.

istor! of o+servations

Since the da5n of recorded civili9ation stars /la!ed a 6e! role in religion and /roved

vital to navigation. Astronom! the stud! of the heavens ma! +e the most ancient of the

sciences. The invention of the telesco/e and the discover! of the la5s of motion and

http://thedailywestern.com/2015/01/the-healthy-eating-trends-of-2015http://thedailywestern.com/2015/01/the-healthy-eating-trends-of-2015http://thedailywestern.com/2015/01/the-healthy-eating-trends-of-2015http://www.space.com/16014-astronomy.htmlhttp://www.space.com/16014-astronomy.htmlhttp://thedailywestern.com/2015/01/the-healthy-eating-trends-of-2015http://thedailywestern.com/2015/01/the-healthy-eating-trends-of-2015


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A !oung glittering collection of stars loo6s li6e an aerial +urst. The cluster is surrounded +! clouds of

interstellar gas and dust4the ra5 material for ne5 star formation. The ne+ula located #$$$$ light-!ears a5a! in the

constellation ,arina contains a central cluster of huge hot stars called N7,


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amount of the mass of these atoms into e8traordinar! amounts of energ! 4 for

instance % gram of mass converted entirel! to energ! 5ould +e e@ual to an e8/losion of

roughl! ##$$$ tons of TNT.

Evolution of stars

The life c!cles of stars follo5 /atterns +ased mostl! on their initial mass. These include

intermediate-mass stars such as the sun 5ith half to eight times the mass of the sun

high-mass stars that are more than eight solar masses and lo5-mass stars a tenth to

half a solar mass in si9e. The greater a stars mass the shorter its lifes/an generall! is.

"+;ects smaller than a tenth of a solar mass do not have enough gravitational /ull to

ignite nuclear fusion 4 some might +ecome failed stars 6no5n as +ro5n d5arfs.

An intermediate-mass star +egins 5ith a cloud that ta6es a+out %$$$$$ !ears to

colla/se into a /rotostar 5ith a surface tem/erature of a+out 1&$ F '$$$$

degrees F '%$$$$$ degrees ,*. Since 5hite d5arves have no fuel left for fusion the!

gro5 cooler and cooler over +illions of !ears to +ecome +lac6 d5arves too faint todetect. '"ur sun should leave the main se@uence in a+out & +illion !ears.*

A high-mass star forms and dies @uic6l!. These stars form from /rotostars in ;ust %$$$$

to %$$$$$ !ears. )hile on the main se@uence the! are hot and +lue some %$$$ to %

million times as luminous as the sun and are roughl! %$ times 5ider. )hen the! leave

the main se@uence the! +ecome a +right red su/ergiant and eventuall! +ecome hot

http://starchild.gsfc.nasa.gov/docs/StarChild/universe_level2/stars_know.htmlhttp://www.space.com/23798-brown-dwarfs.htmlhttp://apod.nasa.gov/apod/ap090803.htmlhttp://www.space.com/22437-main-sequence-stars.htmlhttp://www.space.com/22471-red-giant-stars.htmlhttp://www.space.com/22471-red-giant-stars.htmlhttp://www.space.com/23756-white-dwarf-stars.htmlhttp://www.space.com/23799-black-dwarfs.htmlhttp://starchild.gsfc.nasa.gov/docs/StarChild/universe_level2/stars_know.htmlhttp://www.space.com/23798-brown-dwarfs.htmlhttp://apod.nasa.gov/apod/ap090803.htmlhttp://www.space.com/22437-main-sequence-stars.htmlhttp://www.space.com/22471-red-giant-stars.htmlhttp://www.space.com/23756-white-dwarf-stars.htmlhttp://www.space.com/23799-black-dwarfs.html


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enough to fuse car+on into heavier elements. After some %$$$$ !ears of such fusion

the result is an iron core roughl! $$ miles 5ide '1$$$ 6m* and since an! more

fusion 5ould consume energ! instead of li+erating it the star is doomed as its nuclear

radiation can no longer resist the force of gravit!.

)hen a star reaches a mass of more than %.2 solar masses electron /ressure cannot

su//ort the core against further colla/se according to NASA. The result is a su/ernova.

7ravit! causes the core to colla/se ma6ing the core tem/erature rise to nearl! %>

+illion degrees F '%$ +illion degrees ,* +rea6ing the iron do5n into neutrons and

neutrinos. In a+out one second the core shrin6s to a+out si8 miles '%$ 6m* 5ide and

re+ounds ;ust li6e a ru++er +all that has +een s@uee9ed sending a shoc6 5ave through

the star that causes fusion to occur in the outl!ing la!ers. The star then e8/lodes in a

so-called T!/e II su/ernova. If the remaining stellar core 5as less than roughl! three

solar masses large it +ecomes a neutron star made u/ nearl! entirel! of neutrons and

rotating neutron stars that +eam out detecta+le radio /ulses are 6no5n as /ulsars. If the

stellar core 5as larger than a+out three solar masses no 6no5n force can su//ort it

against its o5n gravitational /ull and it colla/ses to form a +lac6 hole.

A lo5-mass star uses h!drogen fuel so sluggishl! that the! can shine as main-se@uence

stars for %$$ +illion to % trillion !ears 4 since the universe is onl! a+out %


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matter in a /rocess called mass transfer. If one of the mem+ers is a giant star that

leaves +ehind a neutron star or a +lac6 hole an G-ra! +inar! can form 5here matter

/ulled from the stellar remnants com/anion can get e8tremel! hot 4 more than %

million F '&&&&$$ ,* and emit G-ra!s. If a +inar! includes a 5hite d5arf gas /ulled

from a com/anion onto the 5hite d5arfs surface can fuse violentl! in a flash calleda nova. At times enough gas +uilds u/ for the d5arf to colla/se leading its car+on to

fuse nearl! instantl! and the d5arf to e8/lode in a T!/e I su/ernova 5hich can outshine

a gala8! for a fe5 months.

,haracteristics of stars

Brightness

Astronomers descri+e star +rightness in terms of magnitude and luminosit!.

The magnitude of a star is +ased on a scale more than #$$$ !ears old devised

+! 7ree6 astronomer i//archus around %#& B,. e num+ered grou/s of stars +ased

on their +rightness as seen from Earth 4 the +rightest ones 5ere called first magnitude

stars the ne8t +rightest 5ere second magnitude and so on u/ to si8th magnitude the

faintest visi+le ones. No5ada!s astronomers refer to a stars +rightness as vie5ed from

Earth as its a//arent magnitude +ut since the distance +et5een Earth and the star can

affect the light one sees from it the! no5 also descri+e the actual +rightness of a star

using the term a+solute magnitude 5hich is defined +! 5hat its a//arent magnitude

5ould +e if it 5ere %$ /arsecs or


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Stars come in a range of colors from reddish to !ello5ish to +lue. The color of a star

de/ends on surface tem/erature.

A star might a//ear to have a single color +ut actuall! emits a +road s/ectrum of

colors /otentiall! including ever!thing from radio 5aves and infrared ra!s to ultraviolet

+eams and gamma ra!s. (ifferent elements or com/ounds a+sor+ and emit different

colors or 5avelengths of light and +! stud!ing a stars s/ectrum one can divine 5hat its

com/osition might +e.

Surface temperature

Astronomers measure star tem/eratures in a unit 6no5n as the 6elvin 5ith a

tem/erature of 9ero H '?a+solute 9ero?* e@ualing minus #


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Stars 5ith similar masses might not +e similar in si9e +ecause the! have different

densities. For instance Sirius B is roughl! the same mass as the sun +ut is 3$$$$

times as dense and so is onl! a fiftieth its diameter.

The mass of a star affects surface tem/erature.

Magnetic field

Stars are s/inning +alls of roiling electricall! charged gas and thus t!/icall! generate

magnetic fields. )hen it comes to the sun researchers have discovered its magnetic

field can +ecome highl! concentrated in small areas creating features ranging from

suns/ots to s/ectacular eru/tions 6no5n as flares and coronal mass e;ections. A

recent surve! at the arvard-Smithsonian ,enter for Astro/h!sics found that

the average stellar magnetic field increases 5ith the stars rate of rotation and

decreases as the star ages.

Metallicity

The metallicit! of a star measures the amount of ?metals? it has 4 that is an! element

heavier than helium.

Three generations of stars ma! e8ist +ased on metallicit!. Astronomers have not !et

discovered an! of 5hat should +e the oldest generation o/ulation III stars +orn in a

universe 5ithout ?metals.? )hen these stars died the! released heav! elements into

the cosmos 5hich o/ulation II stars incor/orated relativel! small amounts of. )hen a

num+er of these died the! released more heav! elements and the !oungest

o/ulation I stars li6e our sun contain the largest amounts of heav! elements.

Star classification

Stars are t!/icall! classified +! their s/ectrum in 5hat is 6no5n as the Morgan-Heenan

or MH s!stem. There are eight s/ectral classes each analogous to a range of surface

tem/eratures 4 from the hottest to the coldest these are " B A F 7 H M and .

Each s/ectral class also consists of %$ s/ectral t!/es ranging from the numeral $ for

the hottest to the numeral 3 for the coldest.

Stars are also classified +! their luminosit! under the Morgan-Heenan s!stem. The

largest and +rightest classes of stars have the lo5est num+ers given in Roman

numerals 4 Ia is a +right su/ergiant I+ a su/ergiant II a +right giant III a giant ID a

su+giant and D a main se@uence or d5arf.

http://www.cfa.harvard.edu/news/su201450http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/010125a.htmlhttp://nedwww.ipac.caltech.edu/level5/Glossary/Glossary_M.htmlhttp://www.cfa.harvard.edu/news/su201450http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/010125a.htmlhttp://nedwww.ipac.caltech.edu/level5/Glossary/Glossary_M.html


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A com/lete MH designation includes +oth s/ectral t!/e and luminosit! class 4 for

instance the sun is a 7#D.

Stellar structure

The structure of a star can often +e thought of as a series of thin nested shells

some5hat li6e an onion.

A star during most of its life is a main-se@uence star 5hich consists of acore radiative

and convective 9ones a /hotos/here a chromos/here and a corona. The core is 5here

all the nuclear fusion ta6es /laces to /o5er a star. In the radiative 9one energ! from

these reactions is trans/orted out5ard +! radiation li6e heat from a light +ul+ 5hile in

the convective 9one energ! is trans/orted +! the roiling hot gases li6e hot air from a

hairdr!er. Massive stars that are more than several times the mass of the sun

are convective in their cores and radiative in their outer la!ers 5hile stars com/ara+le

to the sun or less in mass are radiative in their cores and convective in their outer

la!ers. Intermediate-mass stars of s/ectral t!/e A ma! +e radiative throughout.

After those 9ones comes the /art of the star that radiates visi+le light the/hotos/here

5hich is often referred to as the surface of the star. After that is the chromos/here a

la!er that loo6s reddish +ecause of all the h!drogen found there. Finall! the outermost

/art of a stars atmos/here is the corona 5hich if su/er-hot might +e lin6ed 5ith

convection in the outer la!ers.

Additional reporting by Nola Taylor Redd, Space.com Contributor

Source:http://www.space.com/57-stars-formation-classication-and-

constellations.html

http://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l1/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l1/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l1/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l1/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.htmlhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.html


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CONSTELLATONS

AN! STA"S

T#ere are a$out %& old constellations' Today astronomers recognize && (%% in eac#

#emis)#ere* dividing all of t#e entire s+y'

THE GREAT BEAR AND THE SEVEN STARS

,ro$a$ly t#e most famous grou) of stars is t#e -ig !i))er' t is a )art of t#econstellation called Ursa .a/or' t resem$les a $ear in many civilizations' T#e #andle

of t#e !i))er is t#e tail of t#e $ear curving away from t#e $owl' t #as t#e seven

$rig#t stars in it namely0 Al+aid0 Alcor 1 .izar (a))ear as one*0 Aliot#0 .egrez0

,#ecda0 .era+ and !#u$e' Two of t#ese t#at form outer wall of t#e $owl are called

t#e ,ointers0 directed towards t#e ,olaris w#en /oined in a line from $ottom u)ward'

T2E LTTLE -EA" AN! ,OLA"S:

3ive ma/or constellations are always visi$le a$ove t#e #orizon from our latitudes:

Ursa .inor0 Ursa .a/or0 Cassio)eia0 Ce)#eus and !raco' T#ey all revolve once in 4%#ours around t#e Nort# Star and stars in t#ese are +nown as Circum)olar stars' Ursa

.inor or t#e Little -ear is well +nown for $eing t#e #ost of ,olaris0 )ositioned very

close to t#e celestial nort# )ole' Actually t#e ,olaris revolves in radius of 5 degree

a$out t#e Nort# celestial )ole'


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,olaris is t#e $rig#test star in t#e Ursa .inor' t is )art of 6 well +nown stars similar

to -ig !i))er' T#e #andle in it curves towards t#e $owl unli+e -ig !i))er'

CASSIOPEIA

Cassio)eia lies on t#e ot#er side of t#e )ole from Ursa .a/or0 almost directly o))osite

t#e -ig !i))er' One can sees t#e seven stars wit# na+ed eyes' Sometimes )eo)le

visualize it as )art of a Crown of t#e Egy)tian 7ueen Cassio)eia0 ot#er )eo)le see it as

an inclined c#air or t#rone'

CEPHEUS

NE8T TO CASSO,EA is #er #us$and t#e +ing Ce)#eus0 +nown for some of t#e

well9studied varia$le stars' Ce)#eus forms a s#a)e resem$ling t#e ca) of a clown' ts

wedge corner is very close to ,olaris and is one of t#e circum)olar stars' T#e $rig#test

star in t#is constellation is called Aldemarin0 meaning t#e arm' t stays close to #is

7ueen'


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Draco, the Dragon

Anot#er famous constellation near t#e Nort# ,ole is !raco meaning !ragon )laced

$eneat# t#e Ursa .inor' t is t#e dragon t#at t#e giant 2ercules faces u) to' Two

+nown stars in it are called Etamin (ti) of !ragons #ead* and T#u$an in t#e tail (;rd

last star* of t#e dragon' Etamin is &< ly away'

T2E !"A=ON

THE ORION AND ITS BRIGHT STARS

Ne>t to t#e -ig !i))er0 Orion is t#e most well +nown constellation of all' ts s#a)e

and grou) of $rig#t stars dominate t#e winter s+y' t contains more $rig#t stars

clustered toget#er t#an any ot#er single grou)' To t#e ancients0 t#e figure re)resented

t#e giant Orion0 )laced in t#e #eavens0 in a #eroic gesture #olding t#e s#ield against

Taurus t#e mig#ty -ull' T#e $ull on t#e ot#er #and0 wit# fire darting out from its eye(mar+ed $y Alde$aran*0 is a$out to c#arge wit# its s)lendid long #orns' Orion stands

wit# #is rig#t arm #olding a great clu$ u)lifted in t#e air0 ready to stri+e' Over #is left

arm #angs a lions s+in t#at #e #olds u) as a s#ield $efore #im to sto) t#e raging $ull'

?it# a $it of imagination0 it is not difficult to o$serve in t#is constellation0 a colossal

figure and a story $e#ind it'


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Orion contains two of t#e 5st magnitude $rig#t stars0 -etelgeuse and "igel'-etelgeuse mar+s t#e rig#t s#oulder or arm)it0 w#ile "igel forms t#e left foot' 3irst0

t#e -etelgeuse rises0 )us#ing its red face' -etelgeuse is a red giant0 dee) red in color'

t is also +nown as an irregular Varia$le star0 c#anging its $rig#tness $ut not regularly'

"igel a))ears a$out 5@ to 4< minutes after -etelgeuse' T#e Celestial e7uator lies

$etween t#e two so t#at "igel is a sout#ern #emis)#ere star and -etelgeuse is a

nort#ern #emis)#ere star' ?it# Alde$aran0 t#e two form a triangle0 called ?inter

triangle0 dominating t#e winter s+y' E>ce)t for !ene$0 "igel (5; outlining t#e Orions $ody0' ts location forms t#e rig#t +nee of t#e

mig#ty #unter' -ellatri> signifies a 3emale ?arrior' Sai)# means sword0 t#e s#a)e

of t#e o$/ect o$tained $y e>tending from !agger stars to it'

Orion is in t#e center of t#e gala>y t#at marc#es in $rilliant )rocession across t#e

winter s+y in all its $eauty and grandeur0 ins)iring innumera$le admirers t#roug#out


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t is t#e nearest to t#e nort# star among t#e 45 $rig#test' !raw a line t#roug# t#e

,olaris at rig#t angle to t#e )ointers0 you s#ould find Ca)ella at %@ degrees from t#e

)olaris on t#e o))osite side of t#e -ig !i))ers #andle' t can also $e found $y a line

drawn from $ottom corner of t#e -ig !i))ers -owl on t#e #andle side0 and )assing

t#e line t#roug# t#e mid )oint of t#e )ointers to a distance of @< degrees or to t#e first

$rig#t star' Ca)ella0 Vega and Arcturus are $rig#test stars in t#e nort#ern #emis)#ereof t#e s+y' Ca)ella is u) a$ove t#e #orizon 45 #ours' T#is ma+es it )ossi$le to o$serve

it sometime every nig#t' Ca)ella first a))ears in t#e evening in August at a$out 5<

Ocloc+ during first )art of t#e mont# and stays in t#e s+y until Bune0 always

a))earing $efore midnig#t' n Octo$er0 it rises almost e>actly in t#e nort#east /ust as

t#e sun is setting'

Ca)ella is a giant star yellow in color and 5


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T#e constellation =emini is t#e t#ird s)ring sign of t#e Hodiac and is re)uted to $ring

good weat#er in early Bune' T#e rainy 2yades0 including Alde$aran were first to

disa))ear0 followed $y stormy Orion and t#e ill9omened !og star wit# it' t is in a

com)aratively serene nig#t s+y0 t#e twin stars0 $eloved of t#e sailors0 s#ine side $yside li+e two eyes ever vigilant to )rotect t#e world under'

T#e twin stars may )roduce immense admiration for closeness of friends#i) $etween

t#e two' n reality0 t#e two are moving in different directions wit#out muc# connection

or fondness to eac# ot#er' Castor at %6 ly and ,ollu> at ;; ly0 are widely se)arated and

are different in s)ectral ty)es' ,ollu> is yellow li+e our sun w#ile Castor is w#ite li+e

Vega'

T#e $ond $etween t#e two is not real and yet Castor #as a com)anion star greenis#

yellow in color' T#e two are se)arated $y an arc of four seconds' t was a common )ractice of t#e ancients to swear $y Castor and ,ollu> (t#e =emini*'

CORONA BOREALIS

Also called Nort#ern Crown0 Corona -orealis is a semicircle of stars' ts c#ief star is

called Al)#ecca0 comes into view one and a 7uarter #ours after Arcturus' T#e grou) of

seven twin+ling $rig#t stars is a $eautiful sig#t for o$servation and en/oyment in t#e

nig#t s+y' T#e entire constellation is only 5@ degrees wide'


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SAGITTARIUS

T#e s#a)e of a tea )ot0 t#is is a remar+a$le s#a)e t#at a))ears in t#e nig#t s+y close to

.il+y way'

Constellation Sagittarius0 also called T#e .il+ !i))er (lies in t#e .il+y way*

HERCULES CONSTELLATION

2E"CULES

2ercules #olds a $ow in #is outstretc#ed arm' Bust s#ot an arrow to t#e !ragon or

)ossi$ly to t#e $ird near$y' 2ercules is located directly nort# of Scor)ius'

FOALHAUT !F"#h$ !P"#ce# A%#tr"n%#$

Still lower in t#e sout#ern s+y t#an Antares0 t#e lonely star 3omal#aut is seen s#ining

$rig#tly' A line /oining t#e ,ointers to t#e )ole and e>tended 54< degrees $eyond from


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t#e )ole0 it will reac# close to 3omal#aut' T#is star is at t#e end of a zigzag line of

small twin+ling stars t#at runs across t#e sout#ern s+y in t#e autumn' T#e small stars

re)resent t#e stream of water t#at A7uarius is )ouring from #is urn' T#e stream runs to

t#e sout#ern )art of t#e constellation ,iscis Austrinus (3is#*' And 3omal#aut means

t#e mout# of t#e 3is#' t rises in Autumn and sin+s in !ecem$er from t#e nig#t s+y'

3omal#aut and Ca)ella rise a$out t#e same time' 3omal#aut )at# is in a s#ort arc'Ca)ella ta+es more t#an two and a #alf #ours to rise at its meridian after 3omal#aut

sin+s' t is one of t#e four "oyal stars of Astrology' Ot#ers are "egulus0 Antares and

Alde$aran' 3omal#aut is never 7uite one fourt# way u) towards t#e zenit# from t#e

#orizon'

3omal#aut in ,iscis Austrinus

t is t#e fart#est sout# of all $rig#t stars from our latitudes' t is an autumn star

a))earing first in August' t gives out 5% times $rig#ter t#an sun' t is 44 ly away' t

does not #ave a com)anion star' t is a lone star'

ANDROEDA AND PEGASUS

!aug#ter of Iueen Cassio)eia and Ding Ce)#eus0 t#e $eautiful )rincess is c#ained to

t#e roc+0 a curse due to #er mot#er w#o $oasted too muc# of #er $eauty' T#e two

constellations Andromeda and ,egasus (t#e flying #orse* are /oined $y one star at t#e

corner of )egasus s7uare' T#e two are a$out 5act eastern )oint in t#e s+y' ?e can find S)ica $y e>tending t#e arc of t#e

!i))ers #andle t#roug# Arcturus and a$out ;< degrees $eyond t#e Arcturus' t can $e

located $y a straig#t line starting at t#e )ointer nearest ,olaris )assing diagonally


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t#roug# t#e $owl of t#e !i))er a$out @ degrees $eyond t#e $ottom of t#e !i))er' t

is visi$le to t#e na+ed eye in t#e middle of .arc# at & Ocloc+ in t#e evening'

S)ica does not ma+e a long arc li+e Arcturus or Ca)ella' t stays sout# of t#e celestial

e7uator' t ta+es 55 #ours for S)ica to com)lete its /ourney setting in t#e sout# western

#orizon' t ta+es five and a #alf #ours to reac# t#e #ig#est )oint in t#e s+y a$out %@degrees from t#e zenit# in t#e sout#ern s+y in .ay' t stays in nig#t s+y $etween

sunset and midnig#t during 3e$ruary t#roug# early Octo$er' n Novem$er0 !ecem$er

and Banuary0 it s#ows u) in t#e nig#t s+y during t#e time $etween midnig#t and dawn'

S)ica lies in Virgo constellation0 close to t#e ecli)tic0 w#ic# is t#e a))arent annual

)at# of t#e sun t#roug# t#e #eavens'

ts color is $luis# w#ite0 meaning its surface tem)erature is greater t#an sun0 Ca)ella

and Arcturus' t is


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t#e evening' t is a$ove t#e #orizon for 5& #ours and t#us rises in #ours after it #as

set'

Vega is @< times $rig#ter t#an sun and 46 ly away' One of t#e most interesting t#ing

a$out Vega0 is t#at our sun toget#er wit# all its )lanets seemed consistently /ourneying

towards it or nearly towards it in t#e constellation Lyra' Vega is a))roac#ing us at 5<miles )er second' Lyra a))ears as vulture in some old ma)s' Vega means t#e

swoo)ing vulture'

DENEB !IN CGNUS CONSTELLATION$

A little more t#an #our after Vega #as risen0 a $rig#t twin+ling star a))ears in t#e

nort# eastern #orizon at )oint %@ degrees from t#e )ole' t is called !ene$ t#at rises

a$out t#e same s)ot on t#e #orizon as Ca)ella' t stays for 4< #ours in t#e s+y only

o$scured $y day lig#t'

T#e #ig#est )oint a star ever reac#es in its

daily course is called its meridian' A line drawn from t#e ,olaris to !ene$ and to Vega

forms a rig#t angle triangle in w#ic# !ene$ lies at rig#t angle' !ene$ lies in t#e

constellation called Cygnus meaning t#e Swan0 an easily identifia$le figure of

stretc#ed wing flying swan in t#e s+y' !ene$ is t#e $rig#test star at t#e #ead of t#e

figure also called Nort#ern Cross' n t#e s)ring w#en it rises in t#e nort# east0 t#e

cross is u)side down' At setting in t#e nort# west0 it seems more nearly u)rig#t and

!ene$ at its #ead sets last of all in t#e cross' !ene$ means tail for its )osition $eing

in t#e tail section of t#e constellation' t is sometimes called $y its Ara$ic name

Arided meaning t#e #indmost'


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!ene$ is is in t#e sout#'


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SUER TRIANGLE

Altair is in A7uila or t#e eagle constellation' Altair means t#e flying eagle'

A $rilliantly w#ite (yellowis# w#ite* star located $y moving down t#e Cross from

!ene$ to its tail to Al$ireo and a$out 4< degrees more to t#e first $rig#t star isALTA"' A$out 5< degrees nort#east from Altair is t#e well +nown Constellation

!ol)#inus0 also called Bo$s coffin'

Altair rises a$out & degrees nort# of t#e e>act eastern )oint on t#e #orizon' Aninteresting figure near Altair is in t#e s#a)e of a diamond wit# a s#ort tail0 lying a$out

5< degrees nort#east of Altair' T#is grou) is called !ol)#inus' t #as a )o)ular name

called Bo$s coffin'

DELPHINUS

n t#e s#a)e of a !ol)#in0 t#is constellation also called Bo$s Coffin consists of @ stars'

t contains a varia$le star0 a dou$le star and a s)ectrosco)ic $inary star'

One seldom sees Altair during t#e first four mont#s of t#e year' t ta+es a$out 5; #ours

for Altair to ma+e its /ourney across t#e s+y' ts color is w#ite or yellowis# w#ite' ts


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surface tem)erature is less t#an Vega $ut greater t#an Ca)ella' Altair is actually 55

times more luminous t#an sun and 56 ly away from us' Altair is a))roac#ing t#e eart#

at a s)eed of 5 miles )er second'

SCORPIUS CONSTELLATION

Constellation Scor)ius meaning scor)ion t#at stung t#e Orion is w#ere Antares can $e

found' t is considered t#e #issing sna+e from w#ic# S)enser re)resents Orion as

flying fast' T#e mig#ty #unter Orion does not return to t#e s+y until scor)ion isgone' T#e two Orion and Scor)ion never a))ear toget#er in t#e s+y' T#e name Antares

signifies "ival of .ars' ?#en t#e .ars a))ears in t#e constellation Scor)ius0 t#e

two red colored o$/ects are s)lendid rivals' Antares is a red giant' t is %)lode on t#e outside0 $ecoming a

Nova or a new star' =ravitational forces t#en attract t#e fragments $ac+ into smallersize fee$ly s#ining star of t#e ty)e +nown as ?#ite !warfs0 e'g'0 com)anion of Sirius'

ANTARES

Antares is at its #ig#est )oint (meridian* in Bune 44nd at 5< Ocloc+ in t#e evening' At

its #ig#est )oint0 it is only one 7uarter way due sout# from t#e #orizon to t#e zenit#' t


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is one of t#e sout# stars w#ic# always lies sout# of t#e celestial e7uator' t a))ears

fart#er sout# from Altair'

Antares is one of a $inary system' ts com)anion #as a greenis# color0 not easily seen

$y small telesco)es'

ALDEBARAN

T#e stars descri$ed in C#a)ter 5 t#roug# C#a)ter 5< earlier0 #ave a )articular

connection wit# t#e s)ring0 summer and autumn mont#s' Ca)ella s#ines t#roug#out

t#e winter0 and in s)ring and fall as well'

T#ere are #owever $rig#t stars t#at are distinctly of t#e winter' T#ese stars are

Alde$aran0 -etelgeuse0 "egel0 ,ollu>0 ,rocyon and Sirius' Of t#ese stars0 Alde$aran

is t#e first to a))ear in Se)tem$er a $it nort# of t#e east )oint in t#e #orizon' t glowswit# rosy lig#t0 demanding attention )roclaiming as one of t#e most im)ortantly

#eavenly $odies'

t lies in t#e o)en end of a $rig#t V9s#a)ed cluster of stars +nown as 2yades' T#e

cluster is t#e #ead of t#e well +nown constellation Taurus t#e $ull0 named $y t#e

=ree+s' t is t#e fiery eye of t#e enraged $ull as #e lowers #is #ead c#arging Orion'

T#e s#immering lig#t of ,leiades can also $e s#own in t#e same constellation Taurus'

T#e meaning of t#e Ara$ic word Alde$aran is t#e #indmost or t#e follower of

,leiades0 as it a))ears directly $elow ,leiades' Alde$aran s#ines for a$out & mont#s int#e s+y every year' One #our after t#e dee) ru$y red Antares vanis#es $elow t#e

western #orizon0 anot#er red star Alde$aran rises in eastern #orizon' T#e two never

can $e seen in t#e nig#t s+y toget#er' T#e two are named "oyal stars in Astrology0 a

suggestion for royalty'


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t is +nown as a standard 5st magnitude star' t is 6< ly away' At t#e distance of t#e

sun0 it would send 5


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arrival of Sirius t#e c#ief' ,rocyon #as com)anion star revolving at a )eriod of %<

years'

REGULUS

"egulus is +nown $y t#e s#a)e of a sic+le it forms wit# five ot#er stars'

REGULUS !IN LEO CONSTELLATION$

"egulus a))ears a$ove t#e #orizon a $it nort# of t#e east a$out Ocloc+ in New

Gears day or a$out t#e C#ristmas time' t is t#e c#ief star of t#e eastern s+y until

Arcturus and Vega come into sig#t' t is a s)ar+ling w#ite star wit# a slig#t #int of $lue in its color' t ta+es a$out and t#ree 7uarter of an #our to reac# t#e meridian' t

s#ines in Banuary t#roug# A)ril in early )art of t#e nig#t s+y' t sin+s com)letely in

August $eing at t#e same )lace as t#e sun' t is 5%< times $rig#ter t#an sun and 66 ly

away' t is found in t#e constellation Leo or t#e Lion (one of Hodiac signs* ' T#e $lade

of t#e sic+le mar+s t#e s#oulder of t#e lion w#ile t#e "egulus lies at its #eart0

sometimes named as #eart of t#e lion' "egulus means C#ief' Sun stays in t#is

constellation a $it more t#an @ wee+s starting at 4nd wee+ of August' An interesting

star in Leo0 is t#e tail of t#e lion0 called !ene$ola' !ene$ola )oints in t#e direction of

anot#er star and t#us forms a dou$le star'

The P+e"ae#T#e ,leiades cluster (.%@* is

sometimes referred to as T#e Seven

Sisters and a))ears in numerous

ancient te>ts including t#e -oo+ of


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Bo$ Can you $ind t#e C#ains of t#e

,leiades Bo$ ;&:;5' T#e Ba)anese

call t#e ,leiades t#e Su$aru and

many )eo)le (incorrectly* call it t#e

little di))er $ecause it loo+s li+e a

tiny version of t#e !i))er'T#e ,leiades is a $eautiful e>am)le of

a young o)en cluster' ?e t#in+ t#at

t#e ,leiades formed from a #uge

T#e cluster of stars is in t#e interstellar dust cloud formed a$out < million years ago

and is situated a$out %5< lig#t years away in t#e direction of t#e constellation Taurus

t#e -ull' T#e $est time to view t#e ,leiades is from late Octo$er to early .arc#'

T#e following )icture is from ,rof' .artins ?e$ ,age at:

#tt):FFwww'+ingsu'a$'caFJ$rianFastroF)leiades'#tm

NUBER OF STARS IN THE UNIVERSE

Ordinary eye sig#t sees a$out @0ies is a$out one trillion0 eac# of w#ic# may #aveas muc# stars as our gala>y on t#e average'

t is t#en a tremendously enormous num$er of stars t#at are )resent in t#e +nown

universe'


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f we use a vacuum cleaner to collect t#e fine dust )articles over t#e volume of size of

t#e eart# in t#e interstellar s)ace0 t#en we will get a$out a cu) full of t#ese dust

)articles' Even suc# a dust can a))recia$ly $loc+ star lig#t $ecause of t#e intervening

vast distances' 3or e>am)le0 our .il+yway would $e muc# $rig#ter in t#e a$sence of

dust clouds o$scuring t#e star lig#t'

T#e num$er of stars catalogued $y astronomers is near &


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times #ig#er t#an )receding one for increase of one order(e>am)le from 5 to 4

magnitude*' Or eac# magnitude of star is four tent#s $rig#ter t#an t#e ne>t #ig#er

magnitude' T#is ma+es first magnitude stars 5 of sout#ern

$rig#t stars can $e seen from Cu$a'

NUBER NAE OF STAR

5 Sirius

4 Cano)us

; Al)#a Centauri

% Arcturus

@ Vega

Ca)ella

6 "egel


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& ,rocyon

Ac#ernar

5< -eta Centauri

55 Altair

54 -etelgeuse

5; Alde$aran

5% Al)#a Crucis

5@ S)ica

5 Antares

56 ,ollu>

5& 3omal#aut

5 !ene$

4< -eta Crucis


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45 "egulus

!istance $etween t#e two ,ointers is a$out @ degrees' t covers a$out ; inc#es of a

ruler w#en #eld fi>ed at arms lengt# and o$serving wit# one eye closed' 3our of t#e

)lanets(Venus0 Bu)iter0 Saturn and .ars* a))ear very $rig#t in t#e s+y and not to $e

confused wit# stars' ,lanets owe t#eir $rig#tness due to reflection of sunrays off t#eir

surfaces' ,lanets are not fi>ed in t#eir )ositions relative to ot#er stars' ,lanets do not

twin+le as stars do' ,lanets s#ine wit# steadier lig#t' ,lanets +ee) t#eir )at# wit#in a

s#ort distance (a few degrees* of moons )at#' ,lanets are not found very far nort# or

very far sout#' Venus stays wit#in %& degrees from sun' n t#e evening s+y0 Venus sets

no more t#an ; #ours after sunset' n t#e early #ours of dawn0 it never rises more t#an

; #ours a#ead of t#e sun' Venus is w#ite0 Bu)iter is a little tinged wit# yellow0 .ars is

fiery red and Saturn is decidedly yellow'

Ot#er 5 $rig#t stars can $e identified wit# reference to T#e -ig !i))er (Ursa .a/or*0

a )art of t#e =reat -ear constellation' t consists of $rig#t stars $ut not $rig#ter t#an

45 of t#e first magnitude stars' t consists of a $owl and a #andle and is always seen in

t#e clear nig#t s+y' Two stars on outer side of t#e $owl0 called t#e )ointers0 so

named $ecause a line /oining t#e two from t#e $ottom to t#e to) )oints toward t#e

Nort# star' T#e distance is a$out @ times t#at of t#e distance $etween t#e )ointers' T#e

Nort# star mar+s t#e center a$out w#ic# t#e Celestial s)#ere revolves' T#e )osition of

t#e stars relative to one anot#er is t#e same'

!OU-LE STA"S:

.any stars t#at seemed single to our na+ed eye are actually dou$le stars or grou) of

stars' =iven t#e enormous distance0 it seemed li+e one star' Also0 a $rig#t star may

actually $e a faint star t#at a))ears $rig#ter $ecause it is closer to t#e eart#' A single

star may #ave a close $y com)anion to ma+e t#em a))ear li+e a dou$le star0 n reality

t#e two may $e far a)art and seen as a dou$le star $ecause t#e two a))ear in t#e samedirection' Actual grou)ing of two stars is fairly common in t#e gala>y' T#ey are called

$inary star system'

Source: htt/:JJ555#./otsdam.eduJislammaJ/h!s


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Stars form inside relatively dense concentrations of interstellar gas and

dust known as molecular clouds. These regions are extremely cold

(temperature about 10 to 20K, just above absolute zero). At these

temperatures, gases become molecular meaning that atoms bind together.

CO and H2 are the most common molecules in interstellar gas clouds. The

deep cold also causes the gas to clump to high densities. When the density

reaches a certain point, stars form.

Since the regions are dense, they are opaque to visible light and are known

asdark nebula. Since they don't shine by optical light, we must use IR and

radio telescopes to investigate them.

Star formation begins when the denser parts of the cloud core collapse

under their own weight/gravity. These cores typically have masses around

104 solar masses in the form of gas and dust. The cores are denser than the

outer cloud, so they collapse first. As the cores collapse they fragment into

clumps around 0.1 parsecs in size and 10 to 50 solar masses in mass.

These clumps then form into protostars and the whole process takes about

10 millions years.

http://abyss.uoregon.edu/~js/glossary/dark_nebula.htmlhttp://abyss.uoregon.edu/~js/glossary/dark_nebula.html


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How do we know this is happening if it takes so long and is hidden from

view in dark clouds? Most of these cloud cores have IR sources, evidence of

energy from collapsing protostars (potential energy converted to kinetic

energy). Also, where we do find young stars (see below) we find them

surrounded by clouds of gas, the leftover dark molecular cloud. And they

occur in clusters, groups of stars that form from the same cloud core.


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Protostars:

Once a clump has broken free from the other parts of the cloud core, it has

its own unique gravity and identity and we call it a protostar. As the

protostar forms, loose gas falls into its center. The infalling gas releases

kinetic energy in the form of heat and the temperature and pressure in the

center of the protostar goes up. As its temperature approaches thousands

of degrees, it becomes a IR source.

Several candidate protostars have been found by the Hubble Space

Telescope in theOrion Nebula.

http://abyss.uoregon.edu/~js/images/orion_solar_systems.jpghttp://abyss.uoregon.edu/~js/images/orion_solar_systems.jpg


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During the initial collapse, the clump is transparent to radiation and the

collapse proceeds fairly quickly. As the clump becomes more dense, it

becomes opaque. Escaping IR radiation is trapped, and the temperature

and pressure in the center begin to increase. At some point, the pressure


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One consequence of this collapse is that young T Tauri stars are usually

surrounded by massive, opaque, circumstellar disks. These disks gradually

accrete onto the stellar surface, and thereby radiate energy both from thedisk (infrared wavelengths), and from the position where material falls

onto the star at (optical and ultraviolet wavelengths). Somehow a fraction

of the material accreted onto the star is ejected perpendicular to the disk

plane in a highly collimated stellar jet. The circumstellar disk eventually

dissipates, probably when planets begin to form. Young stars also have

dark spots on their surfaces which are analogous to sunspots but cover a

much larger fraction of the surface area of the star.

The T-Tauri phase is when a star has:

vigorous surface activity (flares0 eru)tions*

strong stellar winds

varia$le and irregular lig#t curves


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A star in t#e T9Tauri )#ase can lose u) to @


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T#e evolution of young stars is from a cluster of )rotostars dee) in a molecular clouds core0 to acluster of T9Tauri stars w#ose #ot surface and stellar winds #eat t#e surrounding gas to form an

2 region (20 )ronounced 29two0 means ionized #ydrogen*' Later t#e cluster $rea+s out0 t#e

gas is $lown away0 and t#e stars evolve as s#own $elow'


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Often in gala>ies we find clusters of young stars near ot#er young stars' T#is )#enomenon is

called su)ernova induced star formation' T#e very massive stars form first and e>)lode intosu)ernova' T#is ma+es s#oc+ waves into t#e molecular cloud0 causing near$y gas to com)ress

and form more stars' T#is allows a ty)e of stellar co#erence (young stars are found near ot#er

young stars* to $uild u)0 and is res)onsi$le for t#e )inw#eel )atterns we see in gala>ies'


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fre7uently )roduce smaller o$/ects' T#ese #y)ot#esized $odies were called $lac+ stars or infrared

stars $efore t#e name $rown dwarf was suggested in 56@' T#e name is a $it misleadingK a

$rown dwarf actually a))ears red0 not $rown'

n t#e mid95&


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Neit#er )lanets nor stars0 $rown dwarfs s#are )ro)erties wit# $ot# +inds of o$/ects: T#ey are

formed in molecular clouds muc# as stars are0 $ut t#eir atmos)#eres are reminiscent of t#e giantgaseous )lanets' Astronomers are $eginning to c#aracterize variations among $rown dwarfs wit#

t#e aim of determining t#eir significance among t#e =ala>ys constituents' n t#is )ainting ayoung $rown dwarf is ecli)sed $y one of its or$iting )lanets as seen from t#e surface of t#e

)lanets moon'

Source: htt/:JJa+!ss.uoregon.eduJK;sJast%##JlecturesJlec%:%%/m

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Fe+ruar! & #$%&

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