It's 0.08 solar masses. That's the smallest mass for a red dwarf star.
There are "brown dwarf "stars with lower masses, but they are not usually defined as "true stars" because they don't emit energy by nuclear fusion reactions.
They must have enough gravity to burn up their hydrogen to helium. Otherwise, the object doesn't shine as a star and so that it doesn't become a star. Gravity pulls the trigger to start fusion reaction. By the way, gravity means mass.
It is sometimes strange to find stars on the lower end of the main sequence which are no more luminous than white dwarfs for example.
However, the explanation is to be found in the definition of main sequence stars. All stars on the main sequence stars are said to be in hydrostatic equilibrium which essentially means that the outward pressure from the nuclear reaction in the core is balanced by the inward gravitational pressure from the outer layers. The inwards pressure is actually helping to keep the energy generation going through the heat and pressure. As long as this delicate balance exists, the star is said to be on the main sequence.
Stars leave the main sequence when the balance is no longer present or otherwise interrupted. Depending on the original size and type of star, non-main sequence stars will have various sizes and luminosities
The smallest known star is OGLE-TR-122b, a red dwarf star which has a radius of only around 12% of our suns mass, only about 20% bigger than the planet Jupiter (although it's mass is 100 times that of Jupiter). You could get smaller stars though in theory, nuclear fusion could be supported by stars of only 0.08 solar masses.
Below a certain mass limit, the star won't have enough gravity, to create the combination of density and pressure required for normal fusion. This limit seems to be about 0.08 solar masses. Below that, the "star" will still be able to fuse some deuterium, and it will be called a brown dwarf.
.08 M Anything less falls short of the main sequence.
Smaller objects cannot generate enough pressure to start hydrogen fusion
There are black holes that have millions of solar masses.
The largest luminous stars have maybe 100 or so times the mass of our Sun. (one source has a few stars at 175 solar masses)
The lower mass limit for a star is thought to be 0.075 solar masses.
This is about 156 times the mass of Jupiter or 1.49*1029 kg.
The general idea is that, if a star has a lot of mass, it will produce so much energy that it will drive matter away.
The main sequence is a map of star brightness against their temperature. Stars that lie on the main sequence in the top left are the high mass stars. Cooler, smaller stars lie near the line at the lower right.
e. there is a minimum temperature for hydrogen fusion.
Depending on how "low" on the chart it will either be a red dwarf or a PMS (Pre-main sequence) star.
If you are faced with multiple choice, it is NOT, "The Extreme Lower End of the Main Sequence." I got this answer wrong on a recent astronomy quiz.
When a star "goes off the main-sequence" it generally means the star has run out of hydrogen fuel and is beginning the post-main-sequence or its end of life phase. The main sequence of a star is the time where it is no longer just a proto-star but is burning hydrogen as a primary source of fuel.
The reason main sequence has a limit at the lower end is because of temperature and pressure. The lower limit exists in order to exclude stellar objects that are not able to sustain hydrogen fusion.
The main sequence is a map of star brightness against their temperature. Stars that lie on the main sequence in the top left are the high mass stars. Cooler, smaller stars lie near the line at the lower right.
e. there is a minimum temperature for hydrogen fusion.
Depending on how "low" on the chart it will either be a red dwarf or a PMS (Pre-main sequence) star.
If you are faced with multiple choice, it is NOT, "The Extreme Lower End of the Main Sequence." I got this answer wrong on a recent astronomy quiz.
red supergiant
When a star "goes off the main-sequence" it generally means the star has run out of hydrogen fuel and is beginning the post-main-sequence or its end of life phase. The main sequence of a star is the time where it is no longer just a proto-star but is burning hydrogen as a primary source of fuel.
The "main sequence" is the region (on the HR diagram) for stars which burn hydrogen-1. Once stars use up most of their hydrogen-1 (and have significant amounts of helium-4), they leave the main sequence.
No. A star's class on the main sequence is ultimately predetermined by its mass, so a star cannot change its position on the main sequence. Epsilon Eridani is about 82% the mass of the sun, which limits it to a lower rate of fusion and thus a lower temperature and luminosity than a G-type star like the sun. Epsilon Eridani's only change in class will come when it leaves the main sequence to become a red giant.
Main Sequence
white dwarf. unless you count black dwarf of which none have been observed, only theorized.
They are both hotter and cooler because the main sequence contains a lot of stars including the Sun. The main sequence is a region on a Hertzsprung-Russell diagram which plots stars on a graph of brightness against surface temperature. Each star is a point on the diagram because it has one value of brightness and one of temperature. All the main-sequence stars lie on or near a line drawn from top left to lower right. The Sun is about halfway along the main sequence.