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Star (Table)  Diamond ring       constellation        

SUN  Nebula  Black hole    Alpha Centauri    Back to Astronomy

 

 

  Star

 

 

An intrinsically luminous ball of gas generating energy in its hot core through nuclear fusion processes. The minimum mass required to form a star is about one-twentieth the mass of the Sun. Below this limit, the gravitational energy released when the mass condenses is insufficient to raise the temperature to the point at which the fusion of hydrogen to form helium can begin. The most massive stars known are about 100 solar masses. Mass is the prime factor determining the temperature and luminosity the star will have during its existence as a main-sequence star, when hydrogen in the core is its nuclear fuel.
Stars are predominantly hydrogen, with helium as the other major constituent. In the Sun, which is in many ways a typical star, 94 per cent of atoms are hydrogen, 5.9 per cent helium and less than 0.1 per cent other elements. By weight, 73 per cent is hydrogen, 25 per cent helium, 0.8 per cent carbon and 0.3 per cent oxygen, the remaining 0.9 per cent being all the other elements

        

                            

constellation

Originally, constellations were regarded simply as star patterns, but they gradually acquired usefulness as a way of specifying stars and their positions.  Records show that, from antiquity, civilizations have given names to conspicuous patterns of bright stars. Each culture had its own way of dividing the sky into pictorial elements. . there was international agreement among astronomers to define the boundaries of  constellations along lines of right ascension and declination. There are  88 designated areas in the sky or the pattern of stars for 88 constellation (Table).
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Some of the Important Constellations

The largest of the 88 constellations is Hydra, the Water Snake. The area of sky designated as Hydra is 1302.84 square degrees, which is 3.16% of the whole sky. The next largest constellation is Virgo, at 1294.43 square degrees.

Sun our nearest star

This magnetogram taken from  reveals bands of solar activity either side of the Sun's equator. Red and blue areas are regions of strong magnetic field of opposite polarity. Large sunspots often occur in pairs, one of each polarity (north and south).  

All stars are hot, gaseous bodies like the Sun . Of the 50 nearest stars ,10 per cent are brighter, larger, and more massive than the Sun. The nearest star, Alpha Centauri, is about 260,000 times farther from the Earth than is the Sun. It is 4.3 light years away. The entire Milky Way Galaxy is about 100,000 light years across, but only some 1,000 light years thick.The source of the vast quantities of energy radiated by the Sun was long a mystery. The Sun emits energy at the rate of 3.8 × 1026 watts. Life had existed on Earth for billions of years, indicating that solar energy must have been expended at about its present rate for that long. The temperature at the heart of the Sun, about 15 million degrees C. Energy generation process in the sun is the conversion of hydrogen into helium. Energy generation process of the sun is  the conversion of hydrogen into helium. over 4 million tonnes of mass are converted into pure energy at the heart of the Sun each second, in line with the equation, devised by Albert Einstein, E = mc2. This says that mass and energy are interchangeable, and that the energy E locked up in a mass m is equal to the mass multiplied by the square of c, the speed of light The source of the vast quantities of energy radiated by the Sun was long a mystery. The Sun emits energy at the rate of 3.8 × 1026 watts. Life had existed on Earth for billions of years, indicating that solar energy must have been expended at about its present rate for that long. The temperature at the heart of the Sun, about 15 million degrees C. Energy generation process in the sun is the conversion of hydrogen into helium. Energy generation process of the sun is  the conversion of hydrogen into helium. over 4 million tonnes of mass are converted into pure energy at the heart of the Sun each second, in line with the equation, devised by Albert Einstein, E = mc2. This says that mass and energy are interchangeable, and that the energy E locked up in a mass m is equal to the mass multiplied by the square of c, the speed of ligh

Diamond ring

 

annular eclipse
A solar eclipse in which a ring of the Sun's photosphere remains visible when the Sun, Moon and Earth are aligned. Since the orbits of the Earth around the Sun and of the Moon around the Earth are elliptical, the angular diameters of the Sun and Moon vary slightly as their distances from the Earth change. A solar eclipse that would otherwise have been total is seen as annular if the Moon's angular diameter at the time is less than the Sun's

The so-called "diamond ring" effect captured at the end of totality during the solar eclipse of 11 July 1991.

Black hole 

A region of space where the gravitational force is so strong that not even light can escape from it. Black holes are formed when matter collapses in on itself catastrophically so that more than a critical quantity of mass is concentrated into a particularly small region. t is believed that stellar black holes may form when massive stars explode. To create a black hole, several solar masses of material would have to be packed into a diameter of just a few kilometres Black holes are believed to exist at the centres of many galaxies. Black holes can never be observed directly: their existence can only be inferred from their gravitational effects and the radiation emitted by material falling into them.

 Alpha Centauri  

The brightest star in the constellation Centaurus and the nearest bright star to the Sun, at a distance of 4.34 light years. It is a visual binary star with an orbital period of 80 years See table

  Nebula  A cloud of interstellar gas and dust An emission nebula glows in presence of ultraviolet radiation; a reflection nebula shines by reflecting starlight. An absorption nebula is dark and is usually evident only in silhouette against the background of a luminous nebula or starfield.
Other objects consisting of luminous gas are also known as nebulae

right ascension (RA)

One of the coordinates used to define position on the celestial sphere in the equatorial coordinate system. It is the equivalent of longitude on the Earth but is measured in hours, minutes and seconds of time eastwards from the zero point, which is taken as the intersection of the celestial equator and the ecliptic, known as the First Point of Aries. One hour of right ascension is equivalent to 15 degrees of arc; it is the angle through which the celestial sphere appears to turn in one hour of sidereal time, as the Earth rotates.

declination (1) (Dec.)

Declination is the equivalent of latitude on the Earth. It is the angular distance, measured in degrees, north or south of the celestial equator. Northerly declinations are positive and southerly ones negative

                                                             

Table some important Constellation

 
Latin name Area (square degrees) Rank in size order
Andromeda 722 19
Aquarius 980 10
Aquila 652 22
Auriga 657 21
Boötes 907 13
Camelopardalis 757 18
Cancer 506 31
Cassiopeia 598 25
Centaurus 1,060 9
Cepheus 588 27
Cetus 1,231 4
Cygnus 804 16
Draco 1,083 8
Eridanus 1,138 6
Hercules 1,225 5
Horologium 249 58
Hydra 1,303 1
Leo 947 12
Libra 538 29
Lynx 545 28
Ophiuchus 948 11
Orion 594 26
Pegasus 1,121 7
Phoenix 469 37
Pisces 889 14
Puppis 673 20
Sagitta 80 86
Sagittarius 867 15
Scorpius 497 33
Sculptor 475 36
Serpens 637 23
Taurus 797 17
Ursa Major 1,280 3
Virgo 1,294 2

 

 

  Stars of apparent visual magnitude 2.0 and brighter.
Star Name RA Declination Visual magni-
tude*
Spectral classifi-
cation
Dis-
tance (l.y.)**
h m s ° ' ''
Alpha Canis Majoris Sirius 06 45 09 -16 42 58 -1.5 A1 V 8.6
Alpha Carinae Canopus 06 23 57 -52 41 44 -0.7 F0 I 313
Alpha1 Centauri
Alpha2 Centauri
  14
14
39
39
37
35
-60
-60
50
50
02
13
-0.3 G2 V
K1 V
4.4
Alpha Boötis Arcturus 14 15 40 +19 10 57 0.0 K0 III 36
Alpha Lyrae Vega 18 36 56 +38 47 01 0.0 A0 V 25
Alpha Aurigae Capella 05 16 41 +45 59 53 0.1 G8 III 42
Beta Orionis Rigel 05 14 32 -08 12 06 0.1 B8 I 773
Alpha Canis Minoris Procyon 07 39 18 +05 13 30 0.4 F5 IV 11
Alpha Eridani Achernar 01 37 43 -57 14 12 0.5 B5 IV 144
Alpha Orionis Betelgeuse 05 55 10 +07 24 26 0.5 M2 I 427
Beta Centauri Hadar 14 03 49 -60 22 22 0.6 B1 II 525
Alpha Aquilae Altair 19 50 47 +08 52 06 0.8 A7 IV 17
Alpha Tauri Aldebaran 04 35 55 +16 30 33 0.9 K5 III 65
Alpha1 Crucis
Alpha2 Crucis
Acrux 12
12
26
26
36
37
-63
-63
05
05
56
58
0.9 B1 IV
B3
321
Alpha Scorpii Antares 16 29 24 -26 25 55 1.0 M1 I 604
Alpha Virginis Spica 13 25 12 -11 09 41 1.0 B1 V 262
Beta Geminorum Pollux 07 45 19 +28 01 34 1.1 K0 III 34
Alpha Piscis Austrini Fomalhaut 22 57 39 -29 37 20 1.2 A3 V 25
Alpha Cygni Deneb 20 41 26 +45 16 49 1.3 A2 I 3,230
Beta Crucis Mimosa 12 47 43 -59 41 19 1.3 B0 III 352
Alpha Leonis Regulus 10 08 22 +11 58 02 1.4 B7 V 77
Epsilon Canis Majoris Adhara 06 58 38 -28 58 20 1.5 B2 II 431
Alpha Geminorum Castor 07 34 36 +31 53 18 1.6 A1 V 52
Gamma Crucis   12 31 10 -57 06 47 1.6 M3 III 88
Gamma Orionis Bellatrix 05 25 08 +06 20 59 1.6 B2 III 243
Lambda Scorpii Shaula 17 33 36 -37 06 14 1.6 B2 IV 703
Alpha Gruis   22 08 14 -46 57 40 1.7 B5 V 101
Epsilon Orionis Alnilam 05 36 13 -01 12 07 1.7 B0 I 1,342
Beta Tauri Elnath 05 26 18 +28 36 27 1.7 B7 III 130
Beta Carinae   09 13 12 -69 43 02 1.7 A0 III 111
Alpha Persei Mirfak 03 24 19 +49 51 40 1.8 F5 I 592
Zeta Orionis Alnitak 05 40 46 -01 56 34 1.8 O9 I 817
Gamma Velorum   08 09 32 -47 20 12 1.8 WC7 841
Alpha Ursae Majoris Dubhe 11 03 44 +61 45 03 1.8 K0 III 124
Epsilon Ursae Majoris Alioth 12 54 02 +55 57 35 1.8 A0p 81
Theta Scorpii   17 37 19 -42 59 52 1.9 F0 I 212
Alpha Trianguli Australe   16 48 40 -69 01 39 1.9 K2 III 415
Beta Aurigae   05 59 32 +44 56 51 1.9 A2 IV 82
Eta Ursae Majoris Alkaid 13 47 32 +49 18 48 1.9 B3 V 101
Gamma Geminorum   06 37 43 +16 23 57 1.9 A0 IV 105
Epsilon Sagittarii Kaus
Australis
18 24 10 -34 23 05 1.9 B9 IV 145
Delta Canis Majoris   07 08 23 -26 23 36 1.9 F8 I 1,712
Epsilon Carinae   08 22 31 -59 30 34 1.9 K0 II 632
Alpha Pavonis Peacock 20 25 39 -56 44 06 1.9 B3 IV 183
Gamma1 Leonis
Gamma2 Leonis
Algieba 10 19 58 +19 50 30 1.9 K0 III
G5 III
126
Beta Canis Majoris Mirzam 06 22 42 -17 57 22 2.0 B1 II 499
Alpha Hydrae Alphard 09 27 35 -08 39 31 2.0 K3 177
Alpha Ursae Minoris Polaris 02 31 50 +89 15 51 2.0 F8 I 431
Beta Ceti   00 43 35 -17 59 12 2.0 K0 III 96
Delta Velorum   08 44 42 -54 42 30 2.0 A0 V 80
Sigma Sagittarii Nunki 18 55 16 -26 17 48 2.0 B3 IV 224
Alpha Arietis Hamal 02 07 10 +23 27 45 2.0 K2 III 66