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Simply, because they are the hottest and thus the most luminous.

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14y ago
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13y ago

They are only rare at some luminosity levels. The sun is luminosity 1. In the range of luminosity 10 to 100, O and B class stars are quite common.

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Q: Why are o and b main sequence stars rare?
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Most of the stars in the main sequence are to the lower right of the sun what can you conclude about the brightness of these stars and their temperatures?

Main Sequence stars can be any spectral class of star. Something that might help you in the future is when you look up a star and see its spectral class, its always followed by a roman numeral to define where the star is in its life and size and they go as follows. I-a= A hyper Giant Star I-b= A very bright Super Giant star I= A normal Super Giant star II= Bright Giant star III= Giant star IV= Sub Giant star V= Dwarf Star(which this is where most main sequence stars fall into, While a main sequence star could also be one of the classifications listed above. it just depends on its spectral class. for example the star Deneb is in its main sequence still and its classified as a hyper giant) VI= Sub Dwarfs (this is a very rare classification and are mostly used for brown dwarfs. I hope this helps mate.


What spectral class in the sun?

The Sun is a as a G2V type star, a yellow dwarf and a main sequence star. Stars are classified by their spectra(the elements that they absorb) and their temperature. There are seven main types of stars. In order of decreasing temperature, O, B, A, F, G, K, and M


Do dwarf stars emit light?

Brown Dwarfs (maybe not true stars)Red Dwarfs (on the main sequence)Orange Dwarf (on the main sequence)Yellow Dwarfs (stars smaller than our sun but on the main sequence)White Dwarfs (old stars that have run out of hydrogen and are now off the main sequence)Neutron Stars (old large stars who's cores have collapsed during a supernova)---------------------------------------------------------------------------------Red dwarf - Like Proxima Centauri.White dwarf - A degenerate star. The remains of a Sun like star.Yellow dwarf - A G type main sequence star, like our own SunBlue dwarf - A hypothetical star formed from a red dwarf.Brown dwarf - A star that did not have enough mass to initiate nuclear fusion.Black dwarf - A hypothetical star formed when a white dwarf has cooled to absolute zero.Orange dwarf. A K type main sequence star, like Alpha Centauri B


What is the star on the main sequence?

The Main Sequence refers to the H-R diagram of stellar evolution (the Hertzsprung-Russell diagram). If a star is on the Main Sequence, then it is burning with the rate and temperature expected of its spectral class. Stars are divided into the following spectral classes on the H-R diagram: O, B, A, F, G, K, M O, B and A stars burn very hot because they are very large, and they are usually white/blue-white in color F and G stars (our sun is a G star) burn moderately, are moderate in size and give off yellow light K and M stars are red dwarfs. They burn slowly with red color, representing the coolest, least energetic spectrum of light. Stars which are off the Main Sequence but which are on the H-R diagram include Red Giants (like Betelgueuse and Antares), and white dwarfs, stages at the end of a star's life cycle which our sun will eventually pass through. More massive stars have different endings, including supernovae and black holes or neutron stars. These are not on the H-R diagram.


What are B class stars?

B Class stars have the following characteristics.Temperature: 10,000 -> 30,000 KelvinColour: Blue -> Blue-whiteMass: 2.1 -> 16 Solar massesRadius: 1.8 -> 6.6 Solar radiusLuminosity: 25 -> 30,000 Solar luminosities.Rarity: 0.13% of all main sequence stars.Examples: RigelSee related link for more information.

Related questions

How do clusters of O and B stars compare to clusters of T Tauri stars?

T Tauri stars are pre-Main Sequence stars which are large but not as hot as O and B Main Sequence stars. They mainly fall in the categories of F, G, K or M, and they are not yet on the Main Sequence because they are still accreting mass and are still very young and unstable.


Why do o and b stars have a short life on the main sequence?

See related question


What are the seven types of main sequence stars in the universe?

The seven types of main sequence stars in the universe are O (blue and hot), B (white-blue and hot), A (white and hot), F (yellow-white and medium), G (yellow and medium), K (orange and cool), and M (red and cool).


Is the milky way a main sequence star?

All stars that are in hydrostatic equilibrium are on the main sequence, where outward thermal pressure from the hot core is balanced by the inward gravitational pressure from the overlying layers.See related questions


Most of the stars in the main sequence are to the lower right of the sun what can you conclude about the brightness of these stars and their temperatures?

Main Sequence stars can be any spectral class of star. Something that might help you in the future is when you look up a star and see its spectral class, its always followed by a roman numeral to define where the star is in its life and size and they go as follows. I-a= A hyper Giant Star I-b= A very bright Super Giant star I= A normal Super Giant star II= Bright Giant star III= Giant star IV= Sub Giant star V= Dwarf Star(which this is where most main sequence stars fall into, While a main sequence star could also be one of the classifications listed above. it just depends on its spectral class. for example the star Deneb is in its main sequence still and its classified as a hyper giant) VI= Sub Dwarfs (this is a very rare classification and are mostly used for brown dwarfs. I hope this helps mate.


What spectral class in the sun?

The Sun is a as a G2V type star, a yellow dwarf and a main sequence star. Stars are classified by their spectra(the elements that they absorb) and their temperature. There are seven main types of stars. In order of decreasing temperature, O, B, A, F, G, K, and M


What is the color of the procycon?

Procyon is actually a binary Star System in the Canis Minor constellation. Both Procyon A and Procyon B are white stars. A is a Main sequence (still converting Hydrogen to Helium) Star and B is a white dwarf.


Do dwarf stars emit light?

Brown Dwarfs (maybe not true stars)Red Dwarfs (on the main sequence)Orange Dwarf (on the main sequence)Yellow Dwarfs (stars smaller than our sun but on the main sequence)White Dwarfs (old stars that have run out of hydrogen and are now off the main sequence)Neutron Stars (old large stars who's cores have collapsed during a supernova)---------------------------------------------------------------------------------Red dwarf - Like Proxima Centauri.White dwarf - A degenerate star. The remains of a Sun like star.Yellow dwarf - A G type main sequence star, like our own SunBlue dwarf - A hypothetical star formed from a red dwarf.Brown dwarf - A star that did not have enough mass to initiate nuclear fusion.Black dwarf - A hypothetical star formed when a white dwarf has cooled to absolute zero.Orange dwarf. A K type main sequence star, like Alpha Centauri B


What is the star on the main sequence?

The Main Sequence refers to the H-R diagram of stellar evolution (the Hertzsprung-Russell diagram). If a star is on the Main Sequence, then it is burning with the rate and temperature expected of its spectral class. Stars are divided into the following spectral classes on the H-R diagram: O, B, A, F, G, K, M O, B and A stars burn very hot because they are very large, and they are usually white/blue-white in color F and G stars (our sun is a G star) burn moderately, are moderate in size and give off yellow light K and M stars are red dwarfs. They burn slowly with red color, representing the coolest, least energetic spectrum of light. Stars which are off the Main Sequence but which are on the H-R diagram include Red Giants (like Betelgueuse and Antares), and white dwarfs, stages at the end of a star's life cycle which our sun will eventually pass through. More massive stars have different endings, including supernovae and black holes or neutron stars. These are not on the H-R diagram.


What is some information on blue stars?

Blue stars exhibit a moderate increase in size and luminosity compared to main sequence stars of the same mass or temperature, and are hot enough to be called blue, meaning spectral class O, B, and sometimes early A. They have temperatures from around 10,000K upwards.


What are B class stars?

B Class stars have the following characteristics.Temperature: 10,000 -> 30,000 KelvinColour: Blue -> Blue-whiteMass: 2.1 -> 16 Solar massesRadius: 1.8 -> 6.6 Solar radiusLuminosity: 25 -> 30,000 Solar luminosities.Rarity: 0.13% of all main sequence stars.Examples: RigelSee related link for more information.


What color is rigel b?

Rigel B is also a blue-white star but, unlike Rigel A, it is a main sequence star.