Exhausting its hydrogen supply. Main Sequence stars fuse hydrogen to make helium. Eventually, they run out of fuel and then start to fuse helium to make carbon, nitrogen and oxygen, with slightly higher atomic numbers than helium,
The nucleo-chemistry of these reactions involves the generation of more energy and greater loss of mass than hydrogen fusion did which is why after 100 million years or so stars then leave the red giant phase and cool. shrink and turn into white dwarfs.
A red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars.
THE SUN
The Sun is expected to become a red giant in about five billion years. It is calculated that the Sun will become sufficiently large to engulf the current orbits of some of the solar system's inner planets, including Earth.
However, the gravitational pull of the Sun will have weakened by then due to its loss of mass, and all planets but Mercury will escape to a wider orbit. That said, Earth's biosphere will be destroyed as the Sun gets brighter while its hydrogen supply becomes depleted.
The extra solar energy will cause the oceans to evaporate to space, causing Earth's atmosphere to become temporarily similar to that of Venus, before the atmosphere is also lost.
Exhausting its hydrogen supply. Main Sequence stars fuse hydrogen to make helium. Eventually, they run out of fuel and then start to fuse helium to make carbon, nitrogen and oxygen, with slightly higher atomic numbers than helium,
The nucleo-chemistry of these reactions involves the generation of more energy and greater loss of mass than hydrogen fusion did which is why after 100 million years or so stars then leave the red giant phase and cool. shrink and turn into white dwarfs.
A red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars.
THE SUN
The Sun is expected to become a red giant in about five billion years. It is calculated that the Sun will become sufficiently large to engulf the current orbits of some of the solar system's inner planets, including Earth.
However, the gravitational pull of the Sun will have weakened by then due to its loss of mass, and all planets but Mercury will escape to a wider orbit. That said, Earth's biosphere will be destroyed as the Sun gets brighter while its hydrogen supply becomes depleted.
The extra solar energy will cause the oceans to evaporate to space, causing Earth's atmosphere to become temporarily similar to that of Venus, before the atmosphere is also lost.
After a star burns up all it's hydrogen, it becomes a red giant.
A star that has exhausted the hydrogen in its core will become a red giant or supergiant.
I am pretty sure it becomes a giant if I'm not mistaken.
how can a red giant star become brighter if it now has a lower surface temp
A star that is in it's teenage years(medium star) isn't a red giant until it's last years.
That would mainly depend on the star's mass.
A giant star would experience a supernova explosion, in order to become a white dwarf.
After a star burns up all it's hydrogen, it becomes a red giant.
After a star burns up all it's hydrogen, it becomes a red giant.
A star that has exhausted the hydrogen in its core will become a red giant or supergiant.
it doesn't because the star may be already dead before its ready to become a giant.
A star's entire fate is tied into its initial mass. Nothing else matters.
When fusion stops in a star it will start to fuse helium and will become a red giant.
a super giant.
Just once.
red giant
I am pretty sure it becomes a giant if I'm not mistaken.