A Star in its simplest form are giant celestial bodies of gas that generate light, heat and energy through nuclear reaction. They can be many thousands and million times as big as the Earth. The nearest star to us is the Sun then the binary stars of Alpha and Proxima Centauri. They range in colour from red which is the coolest ( 3,500c ) to the very hot which is blue ( 45000c ). The stars are classified according to their temperature and the table below will list the different classes, colour, temperature and a sample star. Their class is no indication as to the size because Betelgeuse and Rigel are comparative in size. The difference is Betelgeuse is old whereas Rigel is relatively new. All the stars that are detailed on this site are in Milky Way, there is hardly any data out there for stars in the other galaxies or the rest of the universe. Each star has its own Solar System and in our solar system, there is only one star and that is The Sun.
Stars come in five distinct colours (Blue, White, Red, Orange, Yellow) and the colour is generally in proportion to its temperature and also its size. There are variations of the colours as you can see from the table below.
Blue stars are generally the hottest and largest of all the stars such as Rigel, a large blue star in Orion. The colours and their Stars are divided into two main groups, giants and dwarfs. Even though our Sun is generally bigger than a lot of other stars in the galaxy, it is still a dwarf star compared to other giants out there such as UY Scuti, a red hypergiant which is nearing the end of its life and will go out in a bang. The bigger a star is, the quicker it lives and dies. Red dwarf stars not Betelgeuse but Proxima Centarui will live a long life of many trillions of years perhaps compared to the ten-fifteen billion of our Sun.
There are no green coloured stars, at least not that have been discovered yet. Antares B star, the companion star of Antares appears green but that is due in part to to effect of the nearby larger star. Another example of a star that can appear green is Zubeneschamali that to some people have reported to be green. The question of whether these stars are green or an off-colour will be answered when advanced telescopes are made or we get to visit the star. Wiki
|Class||Colour||Temperature (Kelvin)||Sample star|
|O||Blue||30,000 or more||Zeta Ophiuchi|
|F||Yellowish White||6,000-7,500||Procyon A|
The image is courtesy of Nova Celestia which has free use image policy.
Stars are created when huge gas clouds begin to collapse and are pulled together by gravity. If during the process, the clouds are not strong enough, the process will fail and the star will become a brown dwarf. Successful collapse clouds will form protostars, broken parts of the cloud. The protostars will continue to collapse until nuclear reactions begin. Parts of the cloud that did not form into the star may become planets. The main ingredient of the star is Hydrogen which through nuclear reaction will turn into Helium and Plasma to be released out into space. The clouds start collapsing when an event has occurred, this could be caused by the explosion of an old star, the gravitational pull of a nearby star or some other event. These clouds are also known as nebulas. A example of a Nebula is the Cone Nebula. The actual cone is a small section of the nebula at the bottom. There are a number of different Nebula's, the Cone is known as a Dark Nebula, this is where light from stars behind are blocked out. Emission Nebulas are where stars are inside the nebulas. A example of a Emission Nebula is the Orion Nebula. The third type are nebulas that are lit up by nearby stars, they are called Reflection Nebulas. The M78. The Triffid Nebula is an example of a Emission/Reflection Nebula.
Pictures from below are taken from Hubble Site.
Throughout its life, a star could be normal like our Sun. A star that has a companion star is known as a Binary Star or a Multiple Star System. Binary refers to two whereas in space there are places where there are more than two stars in the same region of space affecting one another. A well known Binary Star is Polaris A binary star can be Equal ( Both star orbit a central point of gravity ), Unequal ( One star orbits another ) or Double Binary ( A pair of Equal or Unequal ) can be orbiting around a central point of gravity.
The final type is a Variable Star whose brightness could be caused by the internal physical changes. The brightness can change abruptly or in a pattern over a length of time. The reasons for the change in size is too much to go into here, you should check out the line earlier in this paragraph.
Withn a galaxy, a number of stars could be grouped together whether it is a few tens of stars or millions of stars. These Star Clusters fall into two main types, Open Clusters which have no real shape compared to the near spherical look of Globular Clusters. The two most famous star clusters are the Hyades and Pleiades, both found in Taurus. The Pleiades is below.
Like everything that begins, it must come to an end. When a star has finished processing its hydrogen, it dies. The Sun will do so one day but before then, the human race will have moved to another planet or has become extinct. Its end point is determined by its mass. Low mass stars come white dwarfs and high mass black holes. It had been once said that a star exploded near the Sun, the remnants of the star was captured by the Sun and became the planets we know today. The Sun is a medium mass planet which when it dies, it will grow bigger than it is today. The Sun will eventually explode and become a planetary nebula. Planetary Nebulas are stars that have a white dwarf at the centre and a gaseous ring round the out side. Large Mass stars will either become black holes if they are above 3 Solar Masses or a Neutron Star if they slightly less in weight. Neutron Star are stars consisting of Neutrons.
You might think that the Sun, our closest star is big but its tiny compared to other stars out there. The current largest stars in the the milky way that has so far been observed are the giants of VY Canis Majoris and UY Scuti and NML Cygni. These two giants of the cosmos are so vast and large, if they were placed at the centre of the solar system, their size will extend out past Jupiter.
There might be an even larger star out there waiting to be observed, one that would make those two look like peas. The largest unknown star in the universe might not be in our galaxy but somewhere else. The largest star in the universe might make UY Scuti nothing more than a spec compared to the largest in the universe but given there are so many galaxies in the universe and some so far away, we will never be able to determine the largest in the universe.
Stars with common names such as Sirius, Cursa, Regulus and Nunki are large stars that can be seen in the sky and have been known about since the early days of astronomy. They were given star names when astronomy was in its infancy. Stars aren't given common names any more because there are so many. The majority of those stars with common names will tend to be in the Northern Hemisphere as it was people in the Northern Hemisphere that tended to name them.
An example of a named southern hemisphere star is Rigil Kentaurus, another name for Alpha Centauri. Stars that are named HD followed by a number come from the Henry Daper Catalog which was created in the early part of the twentieth century. Stars with starting with HIP are stars that were observed by the Hipparcos satellite from 1989 to 1993. A star can have a common name, a HD and a HIP name as well other names too. Stars with names starting Kepler are those that were observed by the kepler space telescope. A lot of the Extrasolar Planets (Exoplanets) you hear about mainly will be known as a Kepler planet having been discovered by the satellite.
Greek lettered stars are named in order of brightness, so for example Regulus is the brightest star in Leo and therefore named Alpha Leonis, the next is Beta Leonis (Denebola) followed by Gamma Leonis (Algieba), Delta Leonis (Zosma) etc, etc. There are some exceptions to this rule for example, Pollux is Beta Geminorum but it is in fact brighter than Alpha Geminorum (Castor).
Gliese stars are named after German astronomer Wilheim Gliese who catalogued 1000 stars that are within 65 light years from Earth. The list has since been expanded and you will probably have seen these stars when astronomers have been talking about extrasolar planets.
You may have seen companies advertised in papers and on-line to enable you to buy a stars name. If you buy a star, it will have no legal basis, it will not be officially recognised by the International Astronomical Union (I.A.U.) If you want something fun and waste your money but it won't be recognised. If you buy one and then talk about it to a professional astronomer, they won't know which star you mean. 2 If you were to open the naming of stars to the public, you could expect to find stars 'McDonalds', 'Microsoft', 'James Bond'. asteroids have been named after people such as Anne Frank, James Bond and Patrick Moore.
Some stars such as NML Cyngi are named after the people who discovered the star. In this case, the NML stands for Neugebauer, Martz, and Leighton who discovered the star in 1965. Having your surname initial in a stars name is going to be the closest anyone is ever going to get to having a star named after them.
A star has to be big enough to start fusion reaction, turning hydrogen into helium etc. Its been said that the gas giant Jupiter is a failed star, its too small to start fusion reaction. It is possible to get a star started with a mass of 7.5% of the Sun. The smallest star would be a red dwarf star like Proxima Centauri which also happens to be our closest star after the Sun. Proxima Centauri is 12% the size of the Sun so it fits the bill of being a candidate of the smallest star. These red dwarf stars are so faint, they can't be seen from Earth without a telescope. The smallest star that can be seen with the naked eye is 1
Suprisingly, there are a couple of well know stars, Regulus in the constellation of Leo and Vega in the constellation of Lyra are both non-spherical. Regulus is a four star multiple star system and the largest, Regulus A is slightly oval in shape. It probably caused by the other stars that are orbiting around it pulling at the sides so creating the bulge at the middle. However Vega does not have any companion stars its cause.
The thing that makes these two out compared to our Sun is that they rotate faster than our local star, for example, our star roughly rotates at about 4,500 miles per hour whereas Regulus rotates at about 700,000 miles per hour and that clearly influences its shape as well. Its also known that the poles are hotter than the equator on Regulus and is brighter at the poles. ref:Universe Today
The closest star to the Earth is the Sun which is 149,600,000 km away from us. The next closest star to the Earth is Proxima Centauri which is small red dwarf which latest research seems to be that it has a planet in orbit round it. The bad news is that Proxima Centauri lashes the planet with deadly rays and therefore there is no change of life existing on the planet.
The next, non-Centauri and fourth nearest star is a small red dwarf star that is about 4.2 Light Years away from us, it is called Barnard's Star.
A star is too hot and too far away for us to just slice open the star and have a look inside. The way scientists look at a star and determines its composition is to look at the spectrum of the star. Light from a star can be shone through a spectrograph and it broken down into colours. From those colours, you can tell what chemicals are inside the star.
There is a very good example at Rochester Instituite of Technology that shows the wave lengths of various chemicals. You can then apply the rules of chemicals to determine what chemicals are inside the star. According to Utah State University, the composition of the Sun is as follows :-
|Element||Abundance (% of total number of atoms)||Abundance (% of total mass)|
Rogue star are stars that are not part of a galaxy, they are free standing. They are also known as Interstellar Stars because they inhabit the regions of intergalactic space. They have somehow escaped the gravitational pull of the galaxy that they used to orbit. They were only thought to have existed until 1997 when the first ones were discovered in the Virgo constellation. The ones that were discovered are 300,000 light years away from a galaxy. An example of a rogue star is He-0437-5439, a star that is currently on its way out of the Milky Way at three times the orbital speed of our Sun orbiting the galactic centre.
In 1603, German astronomer Johann Bayer came up with the Bayer Classification, a way of labelling stars. He used Greek letters to start with to generally indicate the brightest star in the constellation. When he ran out of Greek letters, he would use latin letters capitalised and then carry on all the way up to z, omitting J and V. Generally speaking the brightest star in the constellation is alpha and so on. This is generally the rule but there are some exceptions. Where there were no brightest stars, he would assign the stars according to the location in the constellation. Vela and Puppis have no alpha stars. A star can have a common name such as Regulus, a Bayer Classification of Alpha Leonis and a Hip ID and a Henry Daper name. A star will not always have a common name such as in the case of Delta Centauri. Hip ID is the ID that the Hipparcos satellite assigned to that star.
Star Luminosity refers to the amount of energy that the star releases in comparison to our Sun. The Sun always has a Solar Luminosity value of 1, a figure that is greater means it releases more energy than the Sun by a factor of how much it is. Generally speaking, a blue star will have a higher luminosity that a red star. There are exceptions to this but generally this is how things are. The Luminosity is also related to the size, a red giant such as UY Scuti will emit thousands more times of energy than a blue giant star because of its size.
The higher a stars luminosity is, the shorter its life. Proxima Centauri emits a low amount of luminosity and will live longer than a blue giant such as Regulus.
|Name||Greek Name||Constellation||Distance (Lt. Yrs.)|
|Al Thalimain||Iota Aquilae||Aquila||391.08|
|Deneb al Okab Borealis||Epsilon Aquilae||Aquila||154.95|
|Tseen Foo||Theta Aquilae||Aquila||286.36|
|Capella Ab||Alpha Aurigae Ab||Auriga|
|Asellus Primus||Theta Bootis||Bootes||47.39|
|Asellus Secundus||Iota Bootis||Bootes||94.81|
|Asellus Tertius||Kappa Bootis B||Bootes||151.49|
|Asellus Australis||Delta Cancri||Cancer||130.57|
|Asellus Borealis||Gamma Cancri||Cancer||181.2|
|Chara||Beta Canum Venaticorum||Canes Venatici||27.53|
|Cor Caroli||Alpha2 Canum Venaticorum||Canes Venatici||114.81|
|Adhara||Epsilon Canis Majoris||Canis Major||405.17|
|Aludra||Eta Canis Majoris||Canis Major||1988.8|
|Furud||Zeta Canis Majoris||Canis Major||362.4|
|Mirzam||Beta Canis Majoris||Canis Major||492.69|
|Muliphein||Gamma Canis Majoris||Canis Major||441.96|
|Sirius||Alpha Canis Majoris||Canis Major||8.6|
|Sirius B||Alpha Canis Majoris B||Canis Major||8.6|
|Wezen||Delta Canis Majoris||Canis Major||1606.72|
|Gomeisa||Beta Canis Minoris||Canis Minor||161.71|
|Procyon||Alpha Canis Minoris||Canis Minor||11.46|
|Procyon B||Alpha Canis Minoris B||Canis Minor||11.41|
|Algiedi Prima||Alpha Capricorni||Capricornus||569.22|
|Deneb Algedi||Delta Capricorni||Capricornus||38.7|
|Ke Kwan||Kappa Centauri||Centaurus||383.27|
|Proxima Centauri||Alpha Centauri C||Centaurus||4.243|
|Rigil Kentaurus||Alpha Centauri||Centaurus||4.32|
|Al Kalb al Rai||Rho-2 Cephei||Cepheus||245.05|
|Garnet Star||Mu Cephei||Cepheus||5930.24|
|Baten Kaitos||Zeta Ceti||Cetus||234.99|
|Deneb Algenub||Eta Ceti||Cetus||123.92|
|Deneb Kaitos Shemali||Iota Ceti||Cetus||274.55|
|Al Kurud||Theta Columbae||Columba||721.6|
|Diadem||Alpha Comae Berenices||Coma Berenices||58.14|
|Meridiana||Alpha Coronae Australis||Corona Australis||125.35|
|Alphecca||Alpha Coronae Borealis||Corona Borealis||75.05|
|Nusakan||Beta Coronae Borealis||Corona Borealis||111.81|
|Acrux B||Alpha Crucis B||Crux||320.71|
|Al Fawaris||Delta Cygni||Cygnus||164.98|
|Albireo||Beta Cygni A||Cygnus||434.31|
|Castor B||Alpha Geminorum B||Gemini|
|Castor C||Alpha Geminorum C||Gemini|
|Al Minliar al Asad||Kappa Leonis||Leo||201.34|
|Ras Elased Australis||Epsilon Leonis||Leo||246.72|
|Regulus B||Alpha Leonis B||Leo||77.49|
|Regulus C||Alpha Leonis C||Leo||77.49|
|Zuben Hakrabi||Eta Librae||Libra||149.21|
|Ke Kouan||Beta Lupi||Lupus||382.82|
|Polaris Australis||Sigma Octantis||Octans||280.93|
|Yed Posterior||Epsilon Ophiuchi||Ophiuchus||106.45|
|Yed Prior||Delta Ophiuchi||Ophiuchus||171.12|
|Gorgonea Tertia||Rho Persei||Perseus||307.7|
|Fum al Samakah||Beta Piscium||Pisces||408.21|
|Kullat Nunu||Eta Piscium||Pisces||349.59|
|Fomalhaut||Alpha Piscis Austrini||Piscis Austrinus||25.13|
|Arkab Posterior||Beta-2 Sagittarii||Sagittarius||134.17|
|Arkab Prior||Beta-1 Sagittarii||Sagittarius||313.62|
|Kaus Australis||Epsilon Sagittarii||Sagittarius||143.31|
|Kaus Borealis||Lambda Sagittarii||Sagittarius||78.18|
|Prima Hyadum||Gamma Tauri||Taurus||161.55|
|Secunda Hyadum||Delta-1 Tauri||Taurus||155.61|
|Atria||Alpha Trianguli Australis||Triangulum Australe||390.61|
|Betria||Beta Trianguli Australis||Triangulum Australe||40.37|
|Gatria||Gamma Trianguli Australis||Triangulum Australe||183.86|
|Alioth||Epsilon Ursae Majoris||Ursa Major||82.55|
|Alkaid||Eta Ursae Majoris||Ursa Major||103.94|
|Alkaphrah||Kappa Ursae Majoris||Ursa Major||358.42|
|Alula Australis||Xi Ursae Majoris||Ursa Major|
|Alula Borealis||Nu Ursae Majoris||Ursa Major||399.22|
|Dubhe||Alpha Ursae Majoris||Ursa Major||122.9|
|Megrez||Delta Ursae Majoris||Ursa Major||80.51|
|Merak||Beta Ursae Majoris||Ursa Major||79.75|
|Mizar||Zeta Ursae Majoris||Ursa Major||85.81|
|Muscida||Omicron Ursae Majoris||Ursa Major||179.11|
|Phecda||Gamma Ursae Majoris||Ursa Major||83.18|
|Sarir||Theta Ursae Majoris||Ursa Major||43.96|
|Taiyangshou||Chi Ursae Majoris||Ursa Major||183.65|
|Talitha||Iota Ursae Majoris||Ursa Major||47.32|
|Tania Australis||Mu Ursae Majoris||Ursa Major||230.34|
|Tania Borealis||Lambda Ursae Majoris||Ursa Major||137.51|
|Akhfa al Farkadain||Zeta Ursae Minoris||Ursa Minor||368.96|
|Anwar Al Farkadain||Eta Ursae Minoris||Ursa Minor||96.99|
|Kochab||Beta Ursae Minoris||Ursa Minor||130.94|
|Pherkad||Gamma Ursae Minoris||Ursa Minor||486.81|
|Polaris||Alpha Ursae Minoris||Ursa Minor||432.58|
|Polaris Ab||Alpha Ursae Minoris Ab||Ursa Minor||431.43|
|Polaris B||Alpha Ursae Minoris B||Ursa Minor||431.43|
|Yildun||Delta Ursae Minoris||Ursa MInor||172.12|
|Tseen Kee||Phi Velorum||Vela||1591.04|
|Rijl al Awwa||Mu Virginis||Virgo||59.59|
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