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STARGAZING

YAMINIWA


 

STARGAZING BY MOHIT JOSHI

 

There are about 1 trillion galaxies in our universe. Each galaxy has about 1 billion stars on average. So our universe has about 1000000000000 * 1000000000 =

1021 stars. Out of these, only about 5000 stars are visible in the night sky. Out of these 5000 stars, only about 200 stars have got names each with particular meaning. I can identify more than 150 stars by their names.

 

During stargazing, I follow the following pattern.

To begin with, it is obvious that I look up at the night sky. Then I utter the name of a particular constellation in low or medium voice while gazing at that constellation. Then I gaze at some of the stars of that constellation in order of their decreasing brightness i.e. in order of increasing Apparent Magnitude. I gaze at each star for about a second and utter its name while gazing at it. Then I move on to the next star of that constellation and so on. Then I move on to the next constellation which, many times, is the neighbouring constellation of the previous one. Then I utter the name of that second constellation while gazing at it. Then I gaze at one or more of the stars of that constellation a la mentioned already. In this way, I gaze about 40 to 60 stars at a particular session of stargazing which requires only about two minutes. I usually do stargazing in this way during 8:00pm - 9:00pm and 4:00am - 5:00am. Sometimes, I do stargazing almost daily and sometimes after a gap of say a week. Below are 5 examples of my stargazing method. These examples include the names of 158 stars. Meanings of some constellations and some stars have been given inside the brackets. In uary 2021, 5:42am  – 5:44am, Star Gazing was donetrolling on the porch behind JR) b

Example 1

On 16 February 2021, 5:42am  – 5:44am, I had done Stargazing as given below.

Here blue colour implies, although those stars are part of my stargazing but on 16 February 2021, either they had not risen or had set or due to some haze, they were not visible during stargazing.

Cygnus (constellation: swan)      Deneb (tail of the hen)   Sadr (chest of the hen)   Geinah Cygni (wing)   Rukh   Albireo    (5 stars)

Lyra  (constellation: lyre)      Vega (falling eagle)   Sulaphat (turtle)   Sheliak (lyra)   (3 stars)

Aquilla (constellation: eagle)      Altair (flying eagle)   Tarazed (beam of the scale)   Deneb el okab Australis (south tail of the eagle)   Tseen Foo (heavenly rafter)   Alshain (falcon)   (3 stars)

Ursa Minor (constellation: little bear)      Polaris (pole star)   Kochab (star)   Pherkad (calf)   Akfha al Farkadein (dimmer calf)   Yil dun (star)  

Anwar al Farkadein (brighter calf)   (5 stars)

Ursa Major  (constellation:  great bear)      Alioth (black horse)   Dubhe (bear)   Alkaid (leader of the mourners)   Mizar (waist cloth)   Merak (loins) 

Phecda (thigh of the bear)   Megrez (base of the tail)   (7 stars)

Canes Venatici (constellation)      Cor Caroli   (1 star)

Leo (constellation: lion)      Regulus (heart of the lion)   Algieba (forehead of the lion)   Denebola (tail of the lion)   Zosma  (hip of the lion)  

Ras Elased Australis (head of the lion)   Chertan (rib)   Adhafera (curl of hair)   Subra (mane of the lion) 

Rasalas/Ras Elased Borealis   Alterf (glance of the lion)   (3 stars)

Virgo (constellation: maiden)      Spica (ear of wheat)   Porrima (goddess of childbirth)   Vindemiatrix (vine harvestress)   (3 stars)

Libra (constellation: scales)      Zuben Elschemali    Zuben Elgenubi   Brachium   Zuben Elakrab   (4 stars)

Scorpius (constellation)      Antares   Shaula   Sargas    Dschubba   Acrab   (3 stars)

Bootes (constellation: herdsman)      Arcturus (guardian of the bear)   Izar (veil)   Mufrid (solitary one)   Seginus   Nekkar (cattle driver)   (5 stars)

Corona Borealis (constellation: northern crown)      Alphecca (broken ring)  Nusaken (two series) (2 stars)

Hercules (constellation: strongman)      Kornephorus (club bearer)   Sarin   Rasalgethi (head of the kneeler)   Sophian (pure)   (4 stars)

Ophiuchus (constellation)      Rasalhegue   Sabik   Han   Yed Prior (western hand)  Yed Posterior (eastern hand)   (5 stars)

Crater (constellation: cup)      Labrum (tip)  Alkes (cup)  (0 star)      

Corvus (constellation: crow)      Geinah Corvi (wing of the crow)   Kraz   Algorab (crow)   Minkar (nose of the crow)  Alchiba (beak of the crow)  (4 stars)

Summer Triangle (Asterism)      Vega  Altair  Deneb

Great Diamond of Virgo (Asterism)      Arcturus  Spica   Denobola  Cor Caroli

 

Thus, during this stargazing, I had gazed at 57 different stars one by one while uttering their names simultaneously.

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Example 2

On 15 October 2021, around 4:20am, I had done Stargazing as given below.

 

Orion (constellation: great hunter)      Rigel (foot)   Betelgeuse (armpit)   Bellatrix (warrioress)   Alnilam (middle of the belt)

Alnitak (east end of the belt)   Saiph (hilt of the sword)   Mintaka (west end of the belt)   (7 stars)

Eridanus (constellation: river)      Achernar   Cursa (footstool of Orion)   Zaurak (boat)   (2 stars)

Cetus  (constellation: sea monster)      Menkar (nose)   Kaffaljidhma (cut-short hand)   Mira (wonderful)   (2 stars)

Lepus  (constellation: hare)      Arnub (hare)   Nihal (camels)   (2 stars)

Columba  (constellation: dove)      Phact (dove)   Wezn (weight)   (2 stars)

Perseus  (constellation: hero)      Mirphak (elbow)   Algol (ghoul)   Gorgonea Tertia (third gorgon sister)   (3 stars)

Auriga  (constellation: charioteer)      Capella (she-goat)   Menkalinun (shoulder of the charioteer)   Mahasim (wrist) 

Hasselah (east end of the belt)   (4 stars)

Taurus  (constellation: bull)      Aldebaran (follower of the pleiades)   Elnath (butting horn)   Alcyone (daughter of Atlas)  (3 stars)

Gemini (constellation: twins)      Pollux   Castor (beaver)   Alhena (shining)   Tejat Posteriori (back foot)   Mebsuta (outstretched paw)   Propus (forward foot)   Alzirr (button)   Wasat (middle of the sky)   mekbuda (pulled in paw)   (9 stars)

Canis Minor (constellation)      Procyon   Gomeisa (bleary eyed)   (2 stars)

Canis Major (constellation)      Sirius   Adhara (maidens)   Wezen (weight)   Mirzam (herald)   Aludra   Furud (solitary ones)   (5 stars)

Puppis (constellation: stern)      Naos (ship)   Tureis    (1 star)

Leo (constellation: lion)      Regulus (heart of the lion)   Algieba (forehead of the lion)   Denebola (tail of the lion)   Zosma  (hip of the lion)  

Ras Elased Australis (head of the lion)   Chertan (rib)   Adhafera (curl of hair)   Subra (mane of the lion) 

Rasalas/Ras Elased Borealis   Alterf (glance of the lion)   (8 stars)

Ursa Major  (constellation:  great bear)      Alioth (black horse)   Dubhe (bear)   Alkaid (leader of the mourners)   Mizar (waist cloth)   Merak (loins) 

Phecda (thigh of the bear)   Megrez (base of the tail)   (5 stars)

Cassiopeia (constellation: queen of Ethiopia)      Schedar   Caff (palm)   Navi   Ruchbah (knee)   Segin   (5 stars)

Winter Triangle  (Asterism)      Sirius Procyon  Betelgeuse

Winter Hexagon  (Asterism)     Rigel  Aldebaran  Capella  Pollux  Procyon  Sirius

Orion’s Belt  (Asterism)            Alnilam   Alnitak   Mintaka

 

Orion’s Sword

 

Thus, during this stargazing, I had gazed at 60 different stars one by one while uttering their names simultaneously.

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Example 3

On 16 October 2021, around 8:20pm, I had done Stargazing as given below.

 

Cygnus (constellation: swan)      Deneb (tail of the hen)   Sadr (chest of the hen)   Geinah Cygni (wing)   Rukh   Albireo    (5 stars)

Lyra  (constellation: lyre)      Vega (falling eagle)   Sulaphat (turtle)   Sheliak (lyra)   (3 stars)

Aquilla (constellation: eagle)      Altair (flying eagle)   Tarazed (beam of the scale)   Deneb el okab Australis (south tail of the eagle)  

Tseen Foo (heavenly rafter)   Alshain (falcon)   (5 stars)

Scutum (constellation: shield)      Ionnina  (1 star)

Andromeda  (constellation: princess of Ethiopia)      Alpheratz (navel of the horse)   Mirach (girdle)   Almach (desert lynx)   (3 stars)

Triangulum (constellation: triangle)      Mothalla (head of the triangle)   (1 star)

Aries (constellation: ram)      Hamal (head of the ram)   Sherathan (two signs)   Mezarthim (fat ram)   (3 stars)

Pisces (constellation: fishes)      Kallat Nunu (cord of the fish)   Alrisha (well rope)   (1 star)

Pegasus (constellation: winged horse)      Enif (nose)   Scheat (upper arm)   Markab (saddle of the horse)   Algenib (flank)   Mater (rain)   Homam (man of high spirit)  

 Sadalbari (splendid one)   Baham (livestock)  (8 stars)

Aquarius (constellation: water bearer)      Sadalsuud  (luck of lucks)    Sadalmelik (luck of the king)   (2 stars)

Capricornus (constellation: sea goat)      Deneb Algedi (tail of the goat)   Dabih (butcher)   Algedi Secunda (billy goat)   Nashira (field)   (4 stars)

Pisces Austrinus (constellation: southern fish)      Fomalhaut (mouth of the fish)   (1 star)

Grus (constellation: crane)      Alnair   Gruid   (0 star)

Summer Triangle (Asterism)   Vega  Altair  Deneb

 

Great Square of Pegasus (Astersim)   Alpheratz   Scheat   Markab  Algenib

 

Thus, during this stargazing, I had gazed at 37 different stars one by one while uttering their names simultaneously.n

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Example 4

On 22 July 2022, around 9:00pm, I had done Stargazing as given below.

 

Cygnus (constellation: swan)      Deneb (tail of the hen)   Sadr (chest of the hen)   Geinah Cygni (wing)   Rukh   Albireo    (5 stars)

Lyra  (constellation: lyre)      Vega (falling eagle)   Sulaphat (turtle)   Sheliak (lyra)   (3 stars)

Aquilla (constellation: eagle)      Altair (flying eagle)   Tarazed (beam of the scale)   Deneb el okab Australis (south tail of the eagle)  

Tseen Foo (heavenly rafter)   Alshain (falcon)   (5 stars)

Scutum (constellation: shield)      Ionnina  (1 star)

Ursa Minor (constellation: little bear)      Polaris (pole star)   Kochab (star)   Pherkad (calf)   Akfha al Farkadein (dimmer calf)   Yil dun (star)  

Anwar al Farkadein (brighter calf)   (6 stars)

Ursa Major  (constellation:  great bear)      Alioth (black horse)   Dubhe (bear)   Alkaid (leader of the mourners)   Mizar (waist cloth)   Merak (loins) 

Phecda (thigh of the bear)   Megrez (base of the tail)   (7 stars)

Hercules (constellation: strongman)      Kornephorus (club bearer)   Sarin   Rasalgethi (head of the kneeler)   Sophian (pure)   (4 stars)

Ophiuchus (constellation)      Rasalhegue   Sabik   Han   Yed Prior (western hand)  Yed Posterior (eastern hand)   (5 stars)

Scorpius (constellation)      Antares   Shaula   Sargas    Dschubba   Acrab   (5 stars)

Saggitarius (constellation: archer)      Kaus Australis (southern bow)  Nunki   Ascella (armpit)  Kaus Media (middle bow)  Kaus Borealis (northern bow)  

Alnasl (arrowhead)   Nanto   Hecetabolus    (8 stars)

Summer Triangle (Asterism)   Vega  Altair  Deneb

 

Thus, during this stargazing, I had gazed at 49 different stars one by one while uttering their names simultaneously.n

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Example 5

On 19 December 2023, around 5:14am, I had done Stargazing as given below.

 

Canes Venatici (constellation)      Cor Caroli   (1 star)

Leo (constellation: lion)      Regulus (heart of the lion)   Algieba (forehead of the lion)   Denebola (tail of the lion)   Zosma  (hip of the lion)  

Ras Elased Australis (head of the lion)   Chertan (rib)   Adhafera (curl of hair)   Subra (mane of the lion) 

Rasalas/Ras Elased Borealis   Alterf (glance of the lion)   (10 stars)

Virgo (constellation: maiden)      Spica (ear of wheat)   Porrima (goddess of childbirth)   Vindemiatrix (vine harvestress)   (3 stars)

Bootes (constellation: herdsman)      Arcturus (guardian of the bear)   Izar (veil)   Mufrid (solitary one)   Seginus   Nekkar (cattle driver)   (5 stars)

Corvus (constellation: crow)      Geinah Corvi (wing of the crow)   Kraz   Algorab (crow)   Minkar (nose of the crow)  Alchiba (beak of the crow)  (5 stars)

Ursa Minor (constellation: little bear)      Polaris (pole star)   Kochab (star)   Pherkad (calf)   Akfha al Farkadein (dimmer calf)   Yil dun (star)  

Anwar al Farkadein (brighter calf)   (3 stars)

Ursa Major  (constellation:  great bear)      Alioth (black horse)   Dubhe (bear)   Alkaid (leader of the mourners)   Mizar (waist cloth)   Merak (loins) 

Phecda (thigh of the bear)   Megrez (base of the tail)   (7 stars)

Gemini (constellation: twins)      Pollux   Castor (beaver)   Alhena (shining)   Tejat Posteriori (back foot)   Mebsuta (outstretched paw)   Propus (forward foot)   Alzirr (button)   Wasat (middle of the sky)   mekbuda (pulled in paw)   (9 stars)

Canis Minor (constellation)      Procyon   Gomeisa (bleary eyed)   (2 stars)

Great Diamond of Virgo (Asterism)      Arcturus  Spica   Denobola  Cor Caroli

Thus, during this stargazing, I had gazed at 45 different stars one by one while uttering their names simultaneously.n

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Some important facts about Astronomy

Constellations Constellations are group of stars that form shapes in the sky.

Astersim: An asterism is a recognized patttern of stars that is not one of the 88 Constellations.

Asterism could be a part of a constellation e.g. the Big Dipper and Orion’s belt asterisms are part of the constellations Ursa Major and Orion respectively Or an asterism could combine stars from several Constellations.

Apparent Magnitude of a star: The apparent magnitude of a star indicates the brightness of the star as we see it from Earth. The lower magnitude indicates brighter star, and higher magnitude indicates fainted star.

Vega, the fifth brightest star in our night sky has an apparent magnitue 0.3 i.e. about zero.

Stars brighter than Vega have a negative apparent magnitude. 

Sirius, the brightest star in our night sky has apparent magnitude – 1.46.

Canopus, the second brightest star in our night sky has apparent magnitude – 0.74.

Arcturus, the third brightest star in our night sky has apparent magnitude – 0.04.

Rigil Kentaurus, the fourh brightest star in our night sky has apparent magnitude – 0.01.

Vega, the fifth brightest star in our night sky has apparent magnitude 0.03.

Capella, the sixth brightest star in our night sky has apparent magnitude 0.08.

Rigel, the seventh brightest star in our night sky has apparent magnitude 0.13.

Procyon, the eighth brightest star in our night sky has apparent magnitude 0.38.

Achemar, the ninth brightest star in our night sky has apparent magnitude 0.46.

Betelgeuse, the tenth brightest star in our night sky has apparent magnitude 0.50.

Altair, the 13th brightest star in our night sky has apparent magnitude 0.77.

Deneb, the 19th brightest star in our night sky has apparent magnitude 1.25.

The sun has apparent magnitue  – 26.7. Thus the sun is about (2.51)26 times brighter than the Vega..

 

Absolute Magnitude of a star: Absolute Magnitude indicates the true intrinsic brightness of the star.

The absolute magnitue of a star is the apparent magnitue that the star would have it if it were placed 10 parsecs (32.6 ly) away from the observer.

If the sun were placed 10 parsecs away, its apparent magnitue would be 4.83 that is the sun has an absolute magnitude of 4.83.

The blue super giant Deneb has an absolute magnitude of – 7.2. Thus Deneb is about (2.51)12 or about 63000 times brighter/luminous than the sun as the difference of absolute magnitude of sun and Deneb is 4.83 + 7.2 = 12.03 ~12.

 

The faintest stars visible to the unaided eye are of apparent magnitude 6.

Through binoculars, stars of apparent magnitude up to 9 may be seen.

Through a backyard telescope, stars of apparent magnitude up to 12 may be seen.

The NASA/ESA Hubble Space Telescope could reach visible magnitude of 31.

A bright star like Vega having apparent magnitud about 0 is (2.51)6 = 100*2.51 = 251 times brighter than the faintest star having magnitude 6.

 ********************************

Classification of Stars

1. Stars are classified into seven classes based on their temperature. These seven classes, from hottest to coolest are: O, B, A, F, G, K, M.

The O and B stars are blue. The A stars are bluish and paler than O and B stars. F stars are white. G stars are white, or yellowish white. K stars are orange or reddish. M stars are quite red.

Three of the bluest bright stars in our night sky are found in Orion’s belt. They are all O and B class, so they are about as blue as stars get.

Blue stars are the hottest. Red stars are the coolest. White and Yellow srars are intermediate.

Blue stars have relatively short lives that end in violent supernova explosions, ultimately resulting in the creation of either black holes or neutron stars.

 

2. Each of the seven classes of stars is subdivided into ten categories from hot to cool, which is represented by a number after the letter.  So, B0 star is hotter than a B1 star and the coolest B-type star is clasified as B9, and then the next slightly cooler star is classified as A0.

The sun is classified as G2 (yellow). Vega is A0 (bluish white). Altair is A7 (white).

 

3. The stars are also classified based on their size within a given temperature class.

3a. The smallest type of stars are classified as main-sequence and are given the Roman numeral V. In main-sequence star, hydrogen fuses into helium in its core.

Sun is a yellow main-sequence, class G2V. 

Vega (in Lyra) is a bluish white main-sequence, class A0V. It is the bluest bright star in the summer sky.

Altair (in Aquilla) is a white main-sequence, class A7V.

Sirius A (in Canis Major) is bluish white main sequence in the winter sky, class A1V.

Procyon (in Canis Minor) is white main-sequence star, class F5V,

Formalhaut (in Piscis Austrinus) is a moderately blue white main-sequence in the autumn sky, class A3V.

Spica (in Virgo) is one of the bluest bright stars in the southeastern sky, early in the spribg evening, class B1V.

Alpha Centauri (in Centaurus) is yellow main-sequence visual (true) binary star. It is visible to the unaided eye as a single star.

The brighter star in Alpha Centauri is class G2V, just like the sun whereas the fainter component is class K0V, a bit redder than the Sun.

 3b. Stars significantly larger than the Sun are classified as ‘giant' and are given the Roman nemeral lll.  

Zaurak (in Eradinus) is a red giant, class M0III.

Arcturus (in Bootees) is a red giant, class K2III.

Aldebran (in Taurus) is a red giant, class K5ll.  It is not far from Betelgeuse. Since it is K-class, it is not as red as Betelgeuse, but it is still noticeably reddish.

Capella (in Auriga) is a double binary star system which includes a yellow giant binary star. Two stars of this binary pair are G0lll and G5lll respectively and are the brightest stars of the system.

3c. Stars intermediate between main-sequence and giant are classified as  the 'sub-giant' and are given the Roman numeral lV.

Alhena (in Gemini) is a blue subgiant, class A0IV.

3d. The largest type of stars within a given temperature class are classified as 'supergiant' and are assigned the Roman numeral l.

Supergiants are sometimes subdivided into a larger class la and a smaller class lb.

Sadalsuud (in Aquarius) is a yellow supergiant, class G0Ib.

Deneb (in Cygnus) is a bluish-white supergiant, class A2Ia.

Betelgeuse (in Orion) is a red supergiant in the winter sky, class M2lb.

Enif (in Pegasus) is an orange supergiant, class K2Ib.

Antares (in Scorpius) is a red supergiant, class M1lb.

Canopus (in Carina) is a white supergiant, class F0lb,

 

Orion’s belt consists of three bright stars: Alnitak, Alnilam, Mintaka, in a straight line, relatively close together at equal distances.

Alnitak is triple star sysyem. The primary star is a blue supergiant, class O9.5Iab (combined apparent magnitude of 3 stars of Alnitak sysyem is V: 1.77)

Alnilam is also blue supergiant, class B0Ia (V: 1.69).

Mintaka is a multiple star system. The primary star is blue giant, class O9.5II. (combined apparent magnitude of all 5 stars of Mintaka system is V: 2.23) 

M2 is redder than M1 in spectrum. M2 is cooler than M1. Betelgeuse is M2, Antares is M1. This means Betelgeuse usually appears a bit redder than Antares.

 

Red and Blue Supergiants:

After the hydrogen-fusing period of a main-sequence star of low or medium mass ends, helium burning begins and star expands into a red giant. However, high mass star more than ten times bigger than the sun becomes a red supergiant during its helium burning phase.

These giants and supergiants fuse helium to carbon and oxygen in their cores by the triple-alpha process.

High mass stars fuse helium into carbon and oxygen at a faster rate, but during periods of slow fusion (which means lesser outward radiation pressure), the star can contract in on itself and become a blue supergiant. They are blue because their temperature are spread over a smaller surface area making them hotter and blue in colour.

Red or blue supergiant may be massive enough to continue fusing heavier elements at its core until core consists of iron only. Then such a red or blue supergiant collapses and becomes a neutron star and eventually explodes as Type II supernova.

 

A red supergiant is much larger than a blue supergiant, but the blue supergiant is much brighter and much hotter

Since main-sequence stars are the smallest within their temperature class, they are sometimes referred to as dwarf stars. So the sun could be called a yellow dwarf.

However white main-sequence stars are not called white dwarf.

********************************

White Dwarf:

The hot center core of the less massive red giant consists of carbon and oxygen but is not sufficiently hot to fuse carbon and oxygen into heavier elements. Thus nuclear fusion in such a red giant ceases. Such a star no longer has any source to produce radiant energy. This means the outward radiation pressure decreases over the time and inward gravitational force becomes more than outward radiation pressure and such a star cools off and contracts as a carbon oxygen white dwarf. If the mass of the star is about 10 solar masses, the core temperature will be sufficient to fuse carbon into neon and magnesium. In this case an oxygen neon magnesium (ONeMg) white dwarf or oxygen neon (ONe) white dwarf is formed.

If the mass of a star is less than the mass of the sun, such a white dwarf is stable because the inward gravitational force is balanced by the outward pressure of electron degenerate gas, but if the mass of the non-roatating white dwarf a star is greater than 1.44 solar masses, the chandrashekar limit, the inward gravitational force becomes greater than the outward pressure of electron degenerate gas and the core of such a white dwarf collapses and undergoes thermonuclear fusion that is a large fraction of the carbon and oxygen in the white dwarf is fused into heavier elements within some seconds, and core temperature increases to billions of degrees. This thermonuclear fusion causes the white dwarf to explode violently and white dwarf becomes Type I supernova.

Type I Supernova occurs in a binary systems in which one of the stars is a white dwarf. Material flows to the white dwarf from its larger companion.

 

Neutron Star:

The source of radiant energy of stars is the nuclear binding energy released in the nuclear fusion of heavier elements from light elements. This fusion proceeds systematically through Periodic Table and heavier elements are found successively in onion like layers with the heaviest nuclei (iron) in the hot center core.

Over billions of years, all the lighter elements in the core of a massive star are converted into iron. Thus nuclear fusion in the star ceases. The inward gravitational force becomes more than the outward radiation pressure and such a star collapses.

During this collapse, most of the iron nuclei are fragmented into neutrons and protons and the Fermi energy of the electrons is enough (> 0.8 MeV) to initiate the conversion of proton into neutron: e + p → ve + n.

This process is called neutronisation. Due to this process, most of the protons in the core of the star are converted into neutrons and such a star is called neutron star. Neutron star does not produce heat but its surface temperature can be 60,000°C. Instead of emitting light, neutron star releases energy in the form of neutrinos and cools down over time by neutrino emission.

 

Type II Supernova:

Type II supernova results from the rapid collapse and violent explosion of a neutron star.

If the mass of the neutron star is less than 10 to 15 solar masses, the inward gravitational force is balanced by the neutron degeneracy pressure and the implosion is halted but if the mass of the neutron star is greater than 10 to 15 solar masses, then the inward gravitational force becomes greater than the outward pressure of neutron degenerate gas and such a neutron star implodes. The mass of the core of such a neutron star is about 1.5 times the mass of the sun and radius about 15 km and the gravitational energy release is about 1059 MeV.

During its initial stage of collapse, neutrinos (produced through the process: e + p → ve + n) of order 1057 in number and accounting for about 1058 MeV, i.e. about 10% of total gravitational energy released, burst out in a flash lasting few milliseconds, and the star is now a supernova.

However 90% of gravitational energy released during the formation of the neutron star is temporarily locked in the core. Even the most penetrating particles, the neutrinos, can only escape from within 100 meter or so of the surface. Now, there is a thermal phase of the stellar core, in which neutrino-antineutrino pairs, electron-positron pairs and gamma rays will be in equilibrium. The remaining, i.e. 90% gravitational energy is emitted in the form of ve , ve`, νμ, νμ`, ντ,  ντ` over several seconds as the core cools down, by neutrino emission.

After Supernova explosion, such a neutron star becomes a blackhole.

 

Pulsar: A pulsar (short for ‘pulsating star’) is a rapidly spinning neutron star.

 

Quasar: Quasar is the brightest type of active galactic nucleus (AGN). An AGN is an extremely luminous galactic core where gas and dust falling into a supermassive black hole emit electromagnetic radiation across the entire electromagnetic spectrum.  This causes the core of such galaxy to be brighter than the rest of the galaxy. Thus, these galaxies look much like stars: point-like, without the fuzzy halo normally associated with a galaxy.
Since these galaxies look much like stars, these are called Quasi-Stellar Objects or QSOs. A small fraction of QSOs also emit powerful radio waves that is they are radio loud. These radio loud QSOs are called Quasi-Stellar Radio Source or Quasars. However, the term 'quasar' is generally used for both radio-quiet and radio loud QSOs.
3C 273 was the first quasar to be discovered. It is located in the constellation Virgo. It is the brightest and closest quasar in the spring sky. It has apparent magnitude 12.9 and is 2.443 billion light years away.
Since it is radio-loud, 3C 273 is a true quasar.


Deep Sky Objects:
Faint objects beyond the solar system other than individual stars are referred to as 'deep sky objects'. They include open star clusters , globular star clusters, nebulae, and galaxies.

Messier objects are deep sky objects.

There are 110 Messier objects. These 110 Messier objects i.e. 110 deep sky objects are represented by M1, M2, M3 ...... M108, M109, M110.

The acronym NGC means New General Catalogue. It contains 7840 deep sky objects.

These 7840 deep sky objects are represented by NGC 1, NGC 2, NGC 3 ..... NGC 7839, NGC 7840. Below are some examples.

M1 and NGC 1952 means Crab Nebula (Constellation: Taurus).

M2 and NGC 7089 means Globular Cluster (Constellation: Aquarius)

M16 and NGC 6611 means Eagle Nebula (Constellation: Serpens)

M31 and NGC 224 means Andromeda galaxy (Constellation: Andromeda)

M42 and NGC 1976 means Orion Nebula (Constellation: Orion)

M43 and NGC 1982 means De Mairan's Nebula (Constellation: Orion)

M51 and NGC 5194 means Whirlpool Galaxy (Constellation: Canes Venatici)

M87 and NGC 4486 means Elliptical Galaxy (Constellation: Virgo)

M104 and NGC 4594 means Sombrero Galaxy (Constellation: Virgo)

NGC 7840 means Unbarred Spiral Galaxy (Constellation: Pisces) 

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Open cluster: Open cluster is a group of a few hundred or a few thousand stars in a relatively small region of space.

Open star clusters are found primarily in the disk of our galaxy Milky Way. Since we are within the disk of the Milky Way, we can see open clusters in virtually any direction. However they are particularly abundant near the central bulge of the Milky Way.

In the summer evening (Northern Hemisphere), the southern part of our sky is directed towards the galactic center. Thus, many open clusters are visible in the summer evening sky in that direction.

The Butterfly Cluster (M6) and Ptolemy Cluster (M7) in the constellation Scorpius are open clusters.

The Wild duck Cluster (M11) in the constellation Scutum is a fairly compact open cluster and just south of Aquila.

The Beehive Cluster (M44) in the constellation Cancer is a large open cluster.

The Coma Berenices Star Cluster in the constellation Coma Berenices is a stunning naked eye open cluster in the spring evening.

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Globular cluster: Globular cluster is a group of about 100000 stars, and is always spherical in shape with greater density near the core.

Globular Clusters orbit around the central bulge of our galaxy Milky Way.

In the summer evening (Northern Hemisphere), the southern part of our sky is directed towards the galactic center. Thus, virtually all globular clusters are found in the summer evening sky, or later spring / early fall in that direction.

M79 is the only one Messier globular cluster visible in our winter sky, and is rather faint.

M3 (in Canes Venatici) is a small but bright globular star cluster with a very dense core. It is northwest of Arcturus.

M13 (in Hercules) is one of the best globular clusters visible in the northern hemisphere. It has a less dense core than M3.

M15 (in Pegasus) like M3 is small but bright globular star cluster with a very dense core and visible in the autumn. It is just slightly northwest of Enif.

M56 (in Lyra) is a globular cluster located between Sulafat (Lyra) and Alberio (Cygnus).

The most spectacular globular cluster visible from Earth is Omega Centauri (in southern constellation Centaurs). This globular cluster is the largest and brightest associated with our galaxy. It contains more than a million stars.

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Nebulae: A nebula is a cloud of hydrogen and helium gas, which is tens to hundreds of light years across.

There are three types of Nebulae: diffuse nebulae, planetary nebulae, supernova remnants.

1. A diiffuse nebula is a nebula which is large and does not have a distinct boundary. There are two types of Diffuse nebulae: emission nebulae and reflection nebulae.

Emission nebulae produce their own light because they are heated by nearby stars.

Reflection nebulae do not produce light, but they reflect light from a nearby star.

Many small carbon grains in the nebula reflect the light. The blue colour typical of reflection nebula is due to the fact that the carbon grains reflect blue light more efficiently than red. M78 in the constellation Orion is a reflection nebula.

The Orion Nebula (M42) and De Mairan’s Nebula (M43) in the constellation Orion are emission-reflection nebulae. Small carbon grains in the nebulae reflect the light from the star Rigel. The blue colour is caused not only by Rigel’s blue colour but because the dust grains reflect blue light more efficiently than red.

Just below Orion’s belt lies Orion’s sword. It consists of three stars, fainter and closer together than the belt stars, and is oriented more vertically (in a roughly north-south fashion). The middle star of this sword is the combined light of the Trapezium and the Orion Nebula.

Orion Nebula (M42) includes four massive stars near the center called the Trapezium.These four stars are responsible fof heating the Orion Nebula and causing it to glow.

The Lagoon Nebula (M8) in the constellation Sagittarius is an emission nebula with clusters. It is the brightest summertime nebula and is  located very close to the (slightly fainter) Trifid Nebula (M20) along the Milky Way.

The Trifid Nebula (M20) in the constellation Sagittarius is an emission reflection and dark nebula with cluster.

The Omega or Swan Nebula  (M17) in the constellation Sagittarius is an emission nebula with clusters, along the Milky Way.

The Eagle Nebula (M16) in the constellation Serpens Cauda is an emission nebula with clusters along the Milky Way, to the north of M8 and M20.

 

2. A planetary nebula is a nebula which is produced by the ejected gas of a star. They are much smaller than diffuse nebulae and are either spherical or bipolar in shape.

The Ring Nebula (M57) in the constellation Lyra is one of the best examples of a planetary nebula. Vega is in the brightest star in the constellation Lyra. There are four faint stars below Vega that form an almost perfect parallelogram. The two stars on the end of the parallelogram and farthest from the Vega are Sheliak and Sulafat. The Ring Nebula is almost in between the stars Sheilak and Sulafat

The Dumbell Nebula (M27) in the constellation Vulpecula is another planetary nebula and close to Ring Nebula. It has two-lobed structure. M27 is 8 degrees east of Albireo, the bottom star in the onstellation Cygnus.

The Eskimo Nebula (NGC 2392) in the constellation Gemini is a planetary nebula.

 

3. A supernova remnant is a nebula which is produced by an exploding star.

The Crab Nebula (M1) in the constellation Taurus is a supernova remnant. The Crab Nebula was produced by a star that exploded in the year 1054.  

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Galaxies: A galaxy is a collection of around 1 billion stars.

There are four basic kinds of galaxies: spirals, ellipticals, lenticulars, and irregulars.

1. Spiral galaxies are disk-shaped, with a brighter bulge at the center of the disk and contain the spiral arms. The central bulge consists primarily of red stars, whereas the spiral arms contain a mixture of red and blue stars.

1a. Some spiral galaxies have a 'bar' going across their central bulge, and are referred to as 'barred spiral galaxies'. Barred spiral galaxy represented by SB and unbarrred spiral galaxy is represented by S.

 

1b. Spiral galaxies can also be classified based on the ratio of bulge size to disk size.

Type a spiral galaxies have a very large central bulge in comparison to their disk. Their spiral arms are tightly wound.

The Sombrero galaxy (M104) in the constellation Virgo is a Type a spiral galaxy (Sa).

Type c spiral galaxies have a very small central bulge in comparison to their disk. Their spiral arms are wide open.

The Whirlpool galaxy (M51) in the constellation Canes Venatici and the Pinwheel galaxy (M101) in the constellation Ursa Major are Type c spiral galaxies (Sc).

 Intermediate between these two is type b spiral galaxy (Sb).

The Bode’s Galaxy (M81) in  the constellation Ursa Major is a type b spiral galaxy (Sb).

M91 in Coma Berenicis is a barred type b spiral galaxy, so it is classified as SBb.

Millky Way is thought to be a barred type b spiral galaxy,

The Andromeda galaxy (M31) is also a type b spiral galaxy (Sb), similar to the Milky Way in overall shape.

M31 is the biggest, brightest and nearest galaxy visible in the Northern Hemisphere. M31 (NGC 224) is around 2.5 million ly away and 200000 ly across.

M31 is only one of the few extra-galactic objects that is blue-shifted that is it is approaching our galaxy. Virtually all other galaxies are red-shifted that is they are moving away from us and from each other due to the expansion of the universe. .

 

1c. Spiral galaxies can also be classified based on the structure of their spiral arms.

Those galaxies whose spiral arms can be traced continually from the core to the periphery are called ‘grand design spiral galaxy’. 

The Whirlpool galaxy (M51) in the constellation Canes Venatici and the Bode’s Galaxy (M81) in the constellation Ursa Major are grand design spiral galaxies.

M74, M83 are also grand design spiral galaxies. M51 is type c spiral galaxy and M81 is type b spiral galaxy.

Those galaxies whose spiral arms cannot be traced continually from the core to the periphery are called ‘flocculent’ spirals.

The Sunflower galaxy (M63) in the constellation Canes Venatici is a flocullent galaxy.

 

2. Elliptical galaxies are those whose basic shape as projected on the sky is an ellipse. They contain no spiral arms.

Elliptical galaxies are designated by “E” followed by a number from 0 to 7.

A perfectly rounded elliptical galaxy is classified as E0, whereas a highly 'stretched' elliptical galaxy is classified as E7.

At the center of the Virgo cluster, there is a giant elliptical galaxy M87 (E0 to E01) located on the line segment connecting Vindemiatrix (Virgo) and Denebola (Leo).

M87 (NGC 4486) is about 55 million ly away and 132000 ly across. It contains over one trillion stars and about 15000 globular clusters. M87 has a supermassive black hole at its core – Powehi, which is responsible for a large jet structure emanating from the nucleus of M87.

M32 and M110 are satellite galaxies of M31. M32 (class E2) and M110 (class E6) are both dwarf elliptical galaxies. M110 and M32 are found above and just below the bulge of M31 respectively.

M32 and M110 are ~2.57 million ly away and 6500 ly and 16000 ly across respectively.

Cygnus A in the constellation Cygnus is an elliptical galaxy. It is about 600 million light years away.  Cygnus A is a radio galaxy, one of the strongest radio sources in the sky.

 

3. Lenticular galaxies often appear much like an E7 elliptical, but they have a definite disk and a central bulge surrounded by a flattened disk. However, they contain no trace of spiral arms.

Lenticular galaxies are designated by S0. M84 in Virgo and M85 in Coma Berenices are lenticular galaxies.

 

4. Irregular galaxies don’t have a distinct regular shape, unlike a spiral or elliptical gakaxy. They generally have no central bulge.

Irregular galaxies are subdivided into (at least) two subclasses.

Irr-l galaxies are those which do have some trace of spiral structure, but not enough to be classified as a true spiral.

Irr-ll galaxies are those which do not have any trace of spiral structure. They are very rare.

Large Magellanic Cloud (LMC) crossing the border of constellations Dorado and Mensa, and Small Magellanic Cloud (SMC) in the constellation Hydrus are both dwarf irregular galaxies in the southern hemisphere. They are both Irr-l galaxies.

For Northern Hemisphere observers, M31 is the only easy naked-eye galaxy. For Southern Hemisphere observers, LMC and SMC are two naked-eye galaxies.

LMC and SMC are satellite galaxies to the Milky Way.

LMC is 163000 ly away and 14000 ly across. us

SMC is 206000 ly away and 7000 ly across. us.

Milky way is 100000 light years across.

LMC was the host galaxy to Supernova 1987 A.   

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There are many types of double stars or binary stars.

Optical double means the two stars only appear to be close together in the sky, but are in fact at different distances.

Visual or true binary means the two stars can be separated in a telescope.

Eclipsing binary shows a change in brightness as one star eclipses the other.

1. Albireo (in Cygnus) is the bright blue-yellow binary star. It is not known whether Albireo is a true binary star, or merely an optical double.

2. Epsilon Lyrae, the famous “double double” is a visual binary star.

3. Almaak (in Andromeda) is the bright blue-yellow visual binary star.

4. Cor Caroli (in Canes Venatici) is the blue-white binary star.

5. Capella (in Auriga) is a double binary star system which includes a yellow giant binary star.

 6. Mizar and Alcor, the middle stars in the handle of the Big Dipper is optical double. Mizar is the bright star and Alcor the faint one. Mizar itself is a true binary.

7. Regulus is a widely separated main sequence binary star.

8. Sirius, the brightest star in our night sky is a visual (true) binary star. Sirius A is a bluish white main-sequence star, class A1V – slightly hotter, larger, and brighter than the sun. Sirius B is a white dwarf, and is much, much fainter, so to resolve them, 12-inch or larger telescope is required

 9. Alpha Centauri (in Centaurus) is yellow main-sequence visual binary star.

10. Acrux (in Crux) is a visual binary star.

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Location of some constellations and stars

1. In winter evening sky (mid-January, 9:00pm), the constellation Orion is high in the south.

Orion’s belt asterism consists of three bright stars: Alnitak, Alnilam, Mintaka, in a straight line, relatively close together at equal distances. Mintaka is at the western end of the Orion’s Belt in winter sky when viewed facing south. Alnitak is at the eastern end of the Orion’s Belt in winter sky.  Alnilam is between them.

Four stars forming a rough rectangle surround Orion’s Belt. Upper east star is Betelgeuse (red supergiant, class M2Ib), upper West star is Bellatrix (blue giant), lower West star is Rigel (blue sub giant) and lower east star is Saiph (blue supergiant).

 

To the east, the line of the Orion’s Belt points towards Sirius, the brightest star. To the west, the line of Orion’ Belt point towards Aldebaran

 

The brightest star in Taurus is Aldebaran (red giant, class K5III).

Aldebaran is located amongst a cluster of much fainter stars forming a 'V' shape. The left end point of this 'V is Aldebaran. The 'V' is a true cluster of stars called the Hyades cluster. Aldebaran is not actually part of the Hyades cluster.

The Pleiades (M 45), one of the best naked eye open star clusters containing hot B-type stars is located in the Constellation Taurus. Pleiades is just west of the Hydaes. M45 consists of a few hundred stars but only six or seven are visible to the unaided eye. They form a shape resembling a tiny little dipper.

 

The constellation Auriga is directly north of Orion, and looks like an uneven Pentagon. The brightest star in Auriga is Capella. Capella (in Auriga) is a double binary star system which includes a yellow giant binary star. Two stars of binary pair are G0lll and G5lll respectively and are the brightest stars of the system.

 

The constellation Perseus is west of Auriga and north of the Pleiades  The second brightest star in Perseus is Algol.

Algol is an eclipsing binary. Every 2.87 days, the faint star passes in front of the bright one, blocking some of its light. Thus every 2.87 days, Algol drops in brightness down to magnitude 3.4 for a few hours, and then goes back to its normal brightness of magnitude 2.1.

 

The constellation Gemini is east of Auriga. Two brightest stars in Gemini are Pollux (orange giant) and Castor (multiple star system). Pollux is the one farther south.

 

The small constellation Canis Minor is in between Sirius and Pollux. The brightest star in Canis Minor is Procyon (white main sequence).

 

2. In spring evening sky (mid-april, 10:00pm), the constellation Leo is very high in the south.

The brightest star in  the constellation Leo is Regulus. East of Regulus is a group of three stars, which form a right triangle. The eastern vertex of this triangle is the star Denebola.

Regulus is a widely separated main sequence binary star. Two components are separated by 177 arc-seconds. Regulus A is class B7V. Regulus B is class K2V.

M65, M66, GC3628 are spiral galaxies and form a triangle called Leo Triplet. These three are near chort in the constellation Leo.

 

The faint constellation Cancer is west of Leo. It lies just about halfway in between Gemini and Leo. It has the shape of an upside down letter 'Y'.

 

The constellation Coma Berenices is east and slightly north of Leo. It consists of only faint stars.

Black Eye galaxy (M64) is located in Coma Berenices and is just north of the Virgo cluster.

Black Eye galaxy (M64) is famous because about half the spiral disk is obscured by dust giving the galaxy a very unusual appearance.

 

The constellation Bootes is just east of Coma Berenices.  It is shaped like a kite. The brightest star in Bootes is Arcturus (red giant,class K2III). It forms the base of the kite.

 

Some constellations are close enough to the celestial pole that they are visible all night, year-round, These are called ‘circumpolar’ constellations

The constellation Ursa Major is circumpolar for northeen latitudes. But it is highest in the north in late spring sky.

Cassiopeia and UrsaMinor are also circumpolar for northern latitude.

 

The astersim Big Dipper is part of Ursa Major. Alkaid and Mizar are the last and middle stars respectively in the handle of the Big Dipper. The two stars on the edge of the bowl of the Big Dipper (Dubhe and Merek) point directly to the North star Polaris which is about five times the distance between Dubhe and Merek away from Dubhe.

The astersim Little Dipper is actually the little constellation Ursa Minor containing 7 stars. Polaris is the last star in the handle of the Little Dipper. The two stars on the edge of the bowl of the Little Dipper (Kochab and Pherkad) are only slightly fainter than Polaris; the rest of the stars in this constellation are much fainter.

Bode’s galaxy (M81) and M82 are located just north of Ursa Major and they are circumpolar for mid-northern latitudes.

The constellation Draco winds up in between Ursa Major and Ursa Minor.

The constellation Canes Venatici is north of Coma Berenices. The brightest star in Canes Venatici is Cor Caroli.

Cor Caroli (in Canes Venatici) is the blue-white binary star. It is visible to the unaided eye as a single star.  A small telescope resolves this binary star into two components which are 19.6 arc-seconds apart. The brighter star in Cor Caroli is class A0 whereas the fainter star is class F0V.

Whirlpool galaxy (M51) is located in Canes Venatici, and is very close to the Big Dipper. M51 is just northwest of Alkaid at about half the distance betweem Alkaid and Mizar.

The Whirlpool galaxy (M51) is actually two galaxies in the process of collision. The larger galaxy M51A is the grand design spiral, and is the brighter of the two. M51 (NGC 5194) is around 23 million ly away and 600000 ly across.

 

The fairly large constellation Virgo is south east of Coma Berenices. The brightest star in Virgo is Spica.

Spica (in Virgo) is one of the bluest bright stars in the southeastern sky, early in the spring evening, class B1V.

 

The Virgo Cluster is east of Leo. The center of the Virgo cluster lies about halfway between Vindemiatrix and Denebola.

This cluster includes 15 Messier galaxies M49, M58, M59, M60, M61, M84, M86, M87, M89, M90 (in Virgo) and M85, M88, M91, M98, M99, and M100 (in coma berenices)

The Virgo cluster is an enormous cluster of galaxies.

 

Sombrero Galaxy (M104) is located in Virgo and is just to the left of the line segment connecting Algorab (Corvus) and Porrima (Virgo), about one-third of the way up. It is west of Spica (Virgo).

The Sombrero Galaxy (M104)  is famous because of the striking dust lane around the galaxy’s perimeter.

M104 (NGC 4594) is around 29 million ly away and 500000 ly across.

Arcturus (in Bootes), Spica (in Virgo), Denobola (in Leo) and Cor Caroli (in Canes Venatici) form the astersim called Great Diamond of Virgo.

 

3. In summer evening sky (mid-july, 11:00pm), Bootes is high in the west.

The small constellation Corona Borealis is just east of Bootes. This constellation forms an almost perfect little half-circle of stars.

The constellation Hercules is just east of Corono Borealis. The stars Eta, Pi, Epsilon, and Zeta Herculis form a trapezoid. This trapezoid contains Hercules Globular Cluster (M13).This globular cluster is located one-third of the way down from Eta to Zeta Herculus.

 

Summer evening is the best time of the year to observe the constellation Scorpius, which is low in the south. The brightest  star in Scorpius is Antares (red supergiant, class M1Ib). A number of star clusters are found in Scorpius. The Butterfly Cluster (M6) and the Ptolemy Cluster (M7) are two such examples.  

In the summer evening (Northern Hemisphere), the southern part of our sky is directed towards the galactic center. Thus, many open and virtually all globular clusters are visible in the summer evening sky in that direction.

The very large constellation Ophiuchus is north of Scorpius and south of Hercules. It consists of stars of magnitude 2 or more.

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4. In late summer evening sky (mid-august, around 11:00pm), the Milky Way shines brightly ovehead and passes through the astersim Summer Triangle consisting of Vega Deneb Altair.

Vega and Deneb are on the north side of the triangle. Vega is west of Deneb. Altair is located at a greater angular distance to the south.

 

The brightest star in the small constellation Lyra is Vega. Lyra consists of about 6 easily visible stars.

Epsilon Lyrae is just east and slightly north of Vega.

Epsilon Lyrae, the famous “double double” is a visual (true) binary star. It is faint but two components are visible to the unaided eye but each of these two components is also a binary atar. A telescope resolves this double double into four stars. The two main pairs appear widely separated. However, the stars within each pair are split by just over 2 arc-seconds. One pair is “horizontal” and the other is 'vertical'. 

 

The brightest star in the constellation Cygnus – the swan is Deneb. Deneb is the “tail of the swan.’  The wingtips of swan are represented by Geinnah Cygni and Rukh. Albireo the bottom star of Northern Cross is the ‘head of the swan.'

Albireo (in Cygnus) is the bright blue-yellow binary star. It is easily visible to the unaided eye as a single star.

A telescope resolves this binary star into two components which are 35 arc-seconds apart. The brighter star in Albireo is blue main sequence (B8V), whereas the fainter star is yellow giant (K3ll).

 

The brightest star in the constellation Aquilla – the Eagle is Altair. Alshain and Tarazed are on the opposite side of Altair. The wingtips of the Eagle are represented by Tseen Foo and Deneb el okab Australis. Lambda Aquilae (V: 3.43) and the nearby stars mark the tail.

 

The Constellation Sagittarius is low in south and slightly west of Aquila. It consists of medium brightness stars (around magnitude 2). The central bulge of our galaxy is within the boundary of this constellation, 26000ly away, so it contains a lot of deep sky objects. Many bright patches of the Milky Way are visible to naked eye in Sagittarius. These are all star clusters and nebulae.

A number of Messier Objects including star clusters and nebulae are found along the Milky Way in and around the Constellations Sagittarius and Scorpius.

Messier Objects in Scorpius (4 MO) are: M4 (globular cluster), M6 (open cluster), M7(open cluster) , M80 (globular cluster)

Messier Objects in Sagittarius (15 MO) are: M8, M17, M20 (nebulae); M18, M21, M23, M25 (open clusters); M22, M28, M54, M55, M69, M70, M75 (globular clusters); M24 (Milky Way star cloud)

 

5. In autumn evening sky (mid-october, around 10:00pm), the constellation Pegasus is very high in the south to southeast.

The most recognizable part of the constellation Pegasus is the asterism called the Great Square of Pegasus. Three out of four stars of this asterism are in Pegasus.

The star on the northwest corner of the Great Square of Pegasus is Alpheratz – the brightest star in the constellation Andromeda.

Andromeda is shaped like a curved bull horn extending northeast from Alpheratz and curving north. This bullhorn is comprised of an upper and lower arc, both of which begin at Alpheratz. The lower arc contains the stars Mirach and Almaak. 

 

Andromeda contains the brightest galaxy in the northern celestial hemisphere: M31.

To locate M31 hop over two stars northeast from Alpheratz to Mirach on the lower arc. Then hop up northwest to Mu Andromedae on the upper arc. Then hop up once more northwest to Nu Andromedae. M31 is located just over one degree west of Nu Andromedae. It is the farthest and largest object that can be (easily) seen with the unaided eye.

 

Cepheus and Cassiopea are both circumpolar constellations for mid-northern latitude. But they are highest in the sky during the autumn. Cassiopea is shaped like a 'W 'or 'M'.

 


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