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Does a star fuse helium to beryllium on the main sequence?
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When a star has finished fusing all its hydrogen into helium, it will then start fusing helium into beryllium and so on and so forth up until iron.
When the star is fusing to beryllium, will the star still be in the main sequence phase and will it at that point start to grow into the red giant phase, or is there no given rule for when it will start growing?
star stellar-evolution nucleosynthesis main-sequence
edited 3 hours ago
HDE 226868♦
18.6k261116
asked 3 hours ago
MiscellaneousUser
435211
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up vote
1
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favorite
When a star has finished fusing all its hydrogen into helium, it will then start fusing helium into beryllium and so on and so forth up until iron.
When the star is fusing to beryllium, will the star still be in the main sequence phase and will it at that point start to grow into the red giant phase, or is there no given rule for when it will start growing?
star stellar-evolution nucleosynthesis main-sequence
edited 3 hours ago
HDE 226868♦
18.6k261116
asked 3 hours ago
MiscellaneousUser
435211
Stars don't fuse helium to beryllium, Be-8 has an extremely short half-life. Beryllium isotopes are produced by cosmic ray spallation.
– PM 2Ring
3 hours ago
Thx PM for highlighting my mistake, I did some more research and see Small ->H->He, Medium go up to Carbon. However massive stars go up Copper and more, I thought fusion stopped at Iron. enchantedlearning.com/subjects/astronomy/stars/fusion.shtml
– MiscellaneousUser
2 hours ago
You're right: stellar fusion does stop at iron / nickel. But in a hot star with sufficient neutron flux heavier species can be "cooked" by the s-process.
– PM 2Ring
2 hours ago
add a comment |Â
up vote
1
down vote
favorite
up vote
1
down vote
favorite
When a star has finished fusing all its hydrogen into helium, it will then start fusing helium into beryllium and so on and so forth up until iron.
When the star is fusing to beryllium, will the star still be in the main sequence phase and will it at that point start to grow into the red giant phase, or is there no given rule for when it will start growing?
star stellar-evolution nucleosynthesis main-sequence
edited 3 hours ago
HDE 226868♦
18.6k261116
asked 3 hours ago
MiscellaneousUser
435211
When a star has finished fusing all its hydrogen into helium, it will then start fusing helium into beryllium and so on and so forth up until iron.
When the star is fusing to beryllium, will the star still be in the main sequence phase and will it at that point start to grow into the red giant phase, or is there no given rule for when it will start growing?
star stellar-evolution nucleosynthesis main-sequence
star stellar-evolution nucleosynthesis main-sequence
edited 3 hours ago
HDE 226868♦
18.6k261116
asked 3 hours ago
MiscellaneousUser
435211
edited 3 hours ago
HDE 226868♦
18.6k261116
asked 3 hours ago
MiscellaneousUser
435211
edited 3 hours ago
HDE 226868♦
18.6k261116
edited 3 hours ago
HDE 226868♦
18.6k261116
edited 3 hours ago
HDE 226868♦
18.6k261116
18.6k261116
asked 3 hours ago
MiscellaneousUser
435211
asked 3 hours ago
MiscellaneousUser
435211
asked 3 hours ago
MiscellaneousUser
435211
435211
Stars don't fuse helium to beryllium, Be-8 has an extremely short half-life. Beryllium isotopes are produced by cosmic ray spallation.
– PM 2Ring
3 hours ago
Thx PM for highlighting my mistake, I did some more research and see Small ->H->He, Medium go up to Carbon. However massive stars go up Copper and more, I thought fusion stopped at Iron. enchantedlearning.com/subjects/astronomy/stars/fusion.shtml
– MiscellaneousUser
2 hours ago
You're right: stellar fusion does stop at iron / nickel. But in a hot star with sufficient neutron flux heavier species can be "cooked" by the s-process.
– PM 2Ring
2 hours ago
add a comment |Â
Stars don't fuse helium to beryllium, Be-8 has an extremely short half-life. Beryllium isotopes are produced by cosmic ray spallation.
– PM 2Ring
3 hours ago
Thx PM for highlighting my mistake, I did some more research and see Small ->H->He, Medium go up to Carbon. However massive stars go up Copper and more, I thought fusion stopped at Iron. enchantedlearning.com/subjects/astronomy/stars/fusion.shtml
– MiscellaneousUser
2 hours ago
You're right: stellar fusion does stop at iron / nickel. But in a hot star with sufficient neutron flux heavier species can be "cooked" by the s-process.
– PM 2Ring
2 hours ago
Stars don't fuse helium to beryllium, Be-8 has an extremely short half-life. Beryllium isotopes are produced by cosmic ray spallation.
– PM 2Ring
3 hours ago
Stars don't fuse helium to beryllium, Be-8 has an extremely short half-life. Beryllium isotopes are produced by cosmic ray spallation.
– PM 2Ring
3 hours ago
Thx PM for highlighting my mistake, I did some more research and see Small ->H->He, Medium go up to Carbon. However massive stars go up Copper and more, I thought fusion stopped at Iron. enchantedlearning.com/subjects/astronomy/stars/fusion.shtml
– MiscellaneousUser
2 hours ago
Thx PM for highlighting my mistake, I did some more research and see Small ->H->He, Medium go up to Carbon. However massive stars go up Copper and more, I thought fusion stopped at Iron. enchantedlearning.com/subjects/astronomy/stars/fusion.shtml
– MiscellaneousUser
2 hours ago
You're right: stellar fusion does stop at iron / nickel. But in a hot star with sufficient neutron flux heavier species can be "cooked" by the s-process.
– PM 2Ring
2 hours ago
You're right: stellar fusion does stop at iron / nickel. But in a hot star with sufficient neutron flux heavier species can be "cooked" by the s-process.
– PM 2Ring
2 hours ago
add a comment |Â
2 Answers
2
active
oldest
votes
up vote
1
down vote
accepted
Main sequence stars are characterized by hydrogen fusion in their cores, either through the proton-proton chain (for lower-mass stars) or the CNO cycle (for stars more than about 1.5 times the Sun's mass). Outside the core, no significant fusion takes place; the outer layers are involved in radiative or convective energy transport, but not energy generation. In general, if hydrogen fusion is occurring in the core, we say that a star is still on the main sequence.
This changes in stars that evolve off the main sequence. Some low-mass red giants may fuse hydrogen to helium via the CNO cycle in a layer outside a largely non-reactive helium core; this is referred to as shell burning. In more massive stars, heavier elements (e.g. helium, carbon, etc.) are fused inside the core, and shell burning continues in the outer layers. For instance, in a fairly high-mass star that is far into the post-main sequence phase of its life, you might see oxygen, neon, carbon, helium and hydrogen being fused in successive layers farther and farther from the core.
A common misconception is that a star uses up all its hydrogen before leaving the main sequence; this is not true. It merely uses up the majority of the hydrogen in its core; there is still plenty in the outer layers, which is what makes shell fusion possible.
answered 3 hours ago
HDE 226868♦
18.6k261116
At what point does a star begin to grow? At the end of hydrogen fusion in the core?
– MiscellaneousUser
3 hours ago
@MiscellaneousUser Stars grow throughout their life in the main sequence. For example, our Sun was only 0.75 R☉ just after its birth, and 3-4 billion years from now it will be around 1.5 R☉. Of course, I assume you are referring to the expansion into a red giant. In that case, it is when helium begins to fuse. Hydrogen still gets fused along the edges of the core, and this is referred to as the Hydrogen-fusion shell, but most of the core will be fusing helium (or heavier elements if later along) at the point. Now, technically, the shell is actually not part of the core, but that's semantics.
– KITTENDESTROYER-9000
2 hours ago
Thanks Kitten, you read my mind.
– MiscellaneousUser
1 hour ago
@KITTENDESTROYER-9000 "In that case, it is when helium begins to fuse. " This part of your comment is not right. A star shrinks when it begins to fuse helium and terminates the first ascent red giant branch.
– Rob Jeffries
19 mins ago
add a comment |Â
up vote
3
down vote
Does a star fuse helium to beryllium on the main sequence?
Star don't fuses helium to beryllium except as a very, very short intermediate step toward carbon. Helium-helium fusion to form beryllium is endothermic: It consumes energy. To make matters worse, the beryllium-8 that results has an extremely short half-life, less than $10^-16$ seconds. Helium would be the end of fusion in stars (and there would be no us) if not for a fluke: The beryllium-8 formed by helium-helium fusion has almost exactly the same energy as does an excited state of carbon-12.
This greatly increases the probability of a third helium-4 nucleus combining with a short-lived beryllium-8 nucleus to form carbon-12. This is stable. The next stage after hydrogen burning is thus triple helium burning (the triple alpha process), essentially bypassing beryllium except as an intermediary.
answered 39 mins ago
David Hammen
10.1k11544
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
1
down vote
accepted
Main sequence stars are characterized by hydrogen fusion in their cores, either through the proton-proton chain (for lower-mass stars) or the CNO cycle (for stars more than about 1.5 times the Sun's mass). Outside the core, no significant fusion takes place; the outer layers are involved in radiative or convective energy transport, but not energy generation. In general, if hydrogen fusion is occurring in the core, we say that a star is still on the main sequence.
This changes in stars that evolve off the main sequence. Some low-mass red giants may fuse hydrogen to helium via the CNO cycle in a layer outside a largely non-reactive helium core; this is referred to as shell burning. In more massive stars, heavier elements (e.g. helium, carbon, etc.) are fused inside the core, and shell burning continues in the outer layers. For instance, in a fairly high-mass star that is far into the post-main sequence phase of its life, you might see oxygen, neon, carbon, helium and hydrogen being fused in successive layers farther and farther from the core.
A common misconception is that a star uses up all its hydrogen before leaving the main sequence; this is not true. It merely uses up the majority of the hydrogen in its core; there is still plenty in the outer layers, which is what makes shell fusion possible.
answered 3 hours ago
HDE 226868♦
18.6k261116
At what point does a star begin to grow? At the end of hydrogen fusion in the core?
– MiscellaneousUser
3 hours ago
@MiscellaneousUser Stars grow throughout their life in the main sequence. For example, our Sun was only 0.75 R☉ just after its birth, and 3-4 billion years from now it will be around 1.5 R☉. Of course, I assume you are referring to the expansion into a red giant. In that case, it is when helium begins to fuse. Hydrogen still gets fused along the edges of the core, and this is referred to as the Hydrogen-fusion shell, but most of the core will be fusing helium (or heavier elements if later along) at the point. Now, technically, the shell is actually not part of the core, but that's semantics.
– KITTENDESTROYER-9000
2 hours ago
Thanks Kitten, you read my mind.
– MiscellaneousUser
1 hour ago
@KITTENDESTROYER-9000 "In that case, it is when helium begins to fuse. " This part of your comment is not right. A star shrinks when it begins to fuse helium and terminates the first ascent red giant branch.
– Rob Jeffries
19 mins ago
add a comment |Â
up vote
1
down vote
accepted
Main sequence stars are characterized by hydrogen fusion in their cores, either through the proton-proton chain (for lower-mass stars) or the CNO cycle (for stars more than about 1.5 times the Sun's mass). Outside the core, no significant fusion takes place; the outer layers are involved in radiative or convective energy transport, but not energy generation. In general, if hydrogen fusion is occurring in the core, we say that a star is still on the main sequence.
This changes in stars that evolve off the main sequence. Some low-mass red giants may fuse hydrogen to helium via the CNO cycle in a layer outside a largely non-reactive helium core; this is referred to as shell burning. In more massive stars, heavier elements (e.g. helium, carbon, etc.) are fused inside the core, and shell burning continues in the outer layers. For instance, in a fairly high-mass star that is far into the post-main sequence phase of its life, you might see oxygen, neon, carbon, helium and hydrogen being fused in successive layers farther and farther from the core.
A common misconception is that a star uses up all its hydrogen before leaving the main sequence; this is not true. It merely uses up the majority of the hydrogen in its core; there is still plenty in the outer layers, which is what makes shell fusion possible.
answered 3 hours ago
HDE 226868♦
18.6k261116
At what point does a star begin to grow? At the end of hydrogen fusion in the core?
– MiscellaneousUser
3 hours ago
@MiscellaneousUser Stars grow throughout their life in the main sequence. For example, our Sun was only 0.75 R☉ just after its birth, and 3-4 billion years from now it will be around 1.5 R☉. Of course, I assume you are referring to the expansion into a red giant. In that case, it is when helium begins to fuse. Hydrogen still gets fused along the edges of the core, and this is referred to as the Hydrogen-fusion shell, but most of the core will be fusing helium (or heavier elements if later along) at the point. Now, technically, the shell is actually not part of the core, but that's semantics.
– KITTENDESTROYER-9000
2 hours ago
Thanks Kitten, you read my mind.
– MiscellaneousUser
1 hour ago
@KITTENDESTROYER-9000 "In that case, it is when helium begins to fuse. " This part of your comment is not right. A star shrinks when it begins to fuse helium and terminates the first ascent red giant branch.
– Rob Jeffries
19 mins ago
add a comment |Â
up vote
1
down vote
accepted
up vote
1
down vote
accepted
Main sequence stars are characterized by hydrogen fusion in their cores, either through the proton-proton chain (for lower-mass stars) or the CNO cycle (for stars more than about 1.5 times the Sun's mass). Outside the core, no significant fusion takes place; the outer layers are involved in radiative or convective energy transport, but not energy generation. In general, if hydrogen fusion is occurring in the core, we say that a star is still on the main sequence.
This changes in stars that evolve off the main sequence. Some low-mass red giants may fuse hydrogen to helium via the CNO cycle in a layer outside a largely non-reactive helium core; this is referred to as shell burning. In more massive stars, heavier elements (e.g. helium, carbon, etc.) are fused inside the core, and shell burning continues in the outer layers. For instance, in a fairly high-mass star that is far into the post-main sequence phase of its life, you might see oxygen, neon, carbon, helium and hydrogen being fused in successive layers farther and farther from the core.
A common misconception is that a star uses up all its hydrogen before leaving the main sequence; this is not true. It merely uses up the majority of the hydrogen in its core; there is still plenty in the outer layers, which is what makes shell fusion possible.
answered 3 hours ago
HDE 226868♦
18.6k261116
Main sequence stars are characterized by hydrogen fusion in their cores, either through the proton-proton chain (for lower-mass stars) or the CNO cycle (for stars more than about 1.5 times the Sun's mass). Outside the core, no significant fusion takes place; the outer layers are involved in radiative or convective energy transport, but not energy generation. In general, if hydrogen fusion is occurring in the core, we say that a star is still on the main sequence.
This changes in stars that evolve off the main sequence. Some low-mass red giants may fuse hydrogen to helium via the CNO cycle in a layer outside a largely non-reactive helium core; this is referred to as shell burning. In more massive stars, heavier elements (e.g. helium, carbon, etc.) are fused inside the core, and shell burning continues in the outer layers. For instance, in a fairly high-mass star that is far into the post-main sequence phase of its life, you might see oxygen, neon, carbon, helium and hydrogen being fused in successive layers farther and farther from the core.
A common misconception is that a star uses up all its hydrogen before leaving the main sequence; this is not true. It merely uses up the majority of the hydrogen in its core; there is still plenty in the outer layers, which is what makes shell fusion possible.
answered 3 hours ago
HDE 226868♦
18.6k261116
answered 3 hours ago
HDE 226868♦
18.6k261116
answered 3 hours ago
HDE 226868♦
18.6k261116
answered 3 hours ago
HDE 226868♦
18.6k261116
18.6k261116
At what point does a star begin to grow? At the end of hydrogen fusion in the core?
– MiscellaneousUser
3 hours ago
@MiscellaneousUser Stars grow throughout their life in the main sequence. For example, our Sun was only 0.75 R☉ just after its birth, and 3-4 billion years from now it will be around 1.5 R☉. Of course, I assume you are referring to the expansion into a red giant. In that case, it is when helium begins to fuse. Hydrogen still gets fused along the edges of the core, and this is referred to as the Hydrogen-fusion shell, but most of the core will be fusing helium (or heavier elements if later along) at the point. Now, technically, the shell is actually not part of the core, but that's semantics.
– KITTENDESTROYER-9000
2 hours ago
Thanks Kitten, you read my mind.
– MiscellaneousUser
1 hour ago
@KITTENDESTROYER-9000 "In that case, it is when helium begins to fuse. " This part of your comment is not right. A star shrinks when it begins to fuse helium and terminates the first ascent red giant branch.
– Rob Jeffries
19 mins ago
add a comment |Â
At what point does a star begin to grow? At the end of hydrogen fusion in the core?
– MiscellaneousUser
3 hours ago
@MiscellaneousUser Stars grow throughout their life in the main sequence. For example, our Sun was only 0.75 R☉ just after its birth, and 3-4 billion years from now it will be around 1.5 R☉. Of course, I assume you are referring to the expansion into a red giant. In that case, it is when helium begins to fuse. Hydrogen still gets fused along the edges of the core, and this is referred to as the Hydrogen-fusion shell, but most of the core will be fusing helium (or heavier elements if later along) at the point. Now, technically, the shell is actually not part of the core, but that's semantics.
– KITTENDESTROYER-9000
2 hours ago
Thanks Kitten, you read my mind.
– MiscellaneousUser
1 hour ago
@KITTENDESTROYER-9000 "In that case, it is when helium begins to fuse. " This part of your comment is not right. A star shrinks when it begins to fuse helium and terminates the first ascent red giant branch.
– Rob Jeffries
19 mins ago
At what point does a star begin to grow? At the end of hydrogen fusion in the core?
– MiscellaneousUser
3 hours ago
At what point does a star begin to grow? At the end of hydrogen fusion in the core?
– MiscellaneousUser
3 hours ago
@MiscellaneousUser Stars grow throughout their life in the main sequence. For example, our Sun was only 0.75 R☉ just after its birth, and 3-4 billion years from now it will be around 1.5 R☉. Of course, I assume you are referring to the expansion into a red giant. In that case, it is when helium begins to fuse. Hydrogen still gets fused along the edges of the core, and this is referred to as the Hydrogen-fusion shell, but most of the core will be fusing helium (or heavier elements if later along) at the point. Now, technically, the shell is actually not part of the core, but that's semantics.
– KITTENDESTROYER-9000
2 hours ago
@MiscellaneousUser Stars grow throughout their life in the main sequence. For example, our Sun was only 0.75 R☉ just after its birth, and 3-4 billion years from now it will be around 1.5 R☉. Of course, I assume you are referring to the expansion into a red giant. In that case, it is when helium begins to fuse. Hydrogen still gets fused along the edges of the core, and this is referred to as the Hydrogen-fusion shell, but most of the core will be fusing helium (or heavier elements if later along) at the point. Now, technically, the shell is actually not part of the core, but that's semantics.
– KITTENDESTROYER-9000
2 hours ago
Thanks Kitten, you read my mind.
– MiscellaneousUser
1 hour ago
Thanks Kitten, you read my mind.
– MiscellaneousUser
1 hour ago
@KITTENDESTROYER-9000 "In that case, it is when helium begins to fuse. " This part of your comment is not right. A star shrinks when it begins to fuse helium and terminates the first ascent red giant branch.
– Rob Jeffries
19 mins ago
@KITTENDESTROYER-9000 "In that case, it is when helium begins to fuse. " This part of your comment is not right. A star shrinks when it begins to fuse helium and terminates the first ascent red giant branch.
– Rob Jeffries
19 mins ago
add a comment |Â
up vote
3
down vote
Does a star fuse helium to beryllium on the main sequence?
Star don't fuses helium to beryllium except as a very, very short intermediate step toward carbon. Helium-helium fusion to form beryllium is endothermic: It consumes energy. To make matters worse, the beryllium-8 that results has an extremely short half-life, less than $10^-16$ seconds. Helium would be the end of fusion in stars (and there would be no us) if not for a fluke: The beryllium-8 formed by helium-helium fusion has almost exactly the same energy as does an excited state of carbon-12.
This greatly increases the probability of a third helium-4 nucleus combining with a short-lived beryllium-8 nucleus to form carbon-12. This is stable. The next stage after hydrogen burning is thus triple helium burning (the triple alpha process), essentially bypassing beryllium except as an intermediary.
answered 39 mins ago
David Hammen
10.1k11544
add a comment |Â
up vote
3
down vote
Does a star fuse helium to beryllium on the main sequence?
Star don't fuses helium to beryllium except as a very, very short intermediate step toward carbon. Helium-helium fusion to form beryllium is endothermic: It consumes energy. To make matters worse, the beryllium-8 that results has an extremely short half-life, less than $10^-16$ seconds. Helium would be the end of fusion in stars (and there would be no us) if not for a fluke: The beryllium-8 formed by helium-helium fusion has almost exactly the same energy as does an excited state of carbon-12.
This greatly increases the probability of a third helium-4 nucleus combining with a short-lived beryllium-8 nucleus to form carbon-12. This is stable. The next stage after hydrogen burning is thus triple helium burning (the triple alpha process), essentially bypassing beryllium except as an intermediary.
answered 39 mins ago
David Hammen
10.1k11544
add a comment |Â
up vote
3
down vote
up vote
3
down vote
Does a star fuse helium to beryllium on the main sequence?
Star don't fuses helium to beryllium except as a very, very short intermediate step toward carbon. Helium-helium fusion to form beryllium is endothermic: It consumes energy. To make matters worse, the beryllium-8 that results has an extremely short half-life, less than $10^-16$ seconds. Helium would be the end of fusion in stars (and there would be no us) if not for a fluke: The beryllium-8 formed by helium-helium fusion has almost exactly the same energy as does an excited state of carbon-12.
This greatly increases the probability of a third helium-4 nucleus combining with a short-lived beryllium-8 nucleus to form carbon-12. This is stable. The next stage after hydrogen burning is thus triple helium burning (the triple alpha process), essentially bypassing beryllium except as an intermediary.
answered 39 mins ago
David Hammen
10.1k11544
Does a star fuse helium to beryllium on the main sequence?
Star don't fuses helium to beryllium except as a very, very short intermediate step toward carbon. Helium-helium fusion to form beryllium is endothermic: It consumes energy. To make matters worse, the beryllium-8 that results has an extremely short half-life, less than $10^-16$ seconds. Helium would be the end of fusion in stars (and there would be no us) if not for a fluke: The beryllium-8 formed by helium-helium fusion has almost exactly the same energy as does an excited state of carbon-12.
This greatly increases the probability of a third helium-4 nucleus combining with a short-lived beryllium-8 nucleus to form carbon-12. This is stable. The next stage after hydrogen burning is thus triple helium burning (the triple alpha process), essentially bypassing beryllium except as an intermediary.
answered 39 mins ago
David Hammen
10.1k11544
answered 39 mins ago
David Hammen
10.1k11544
answered 39 mins ago
David Hammen
10.1k11544
answered 39 mins ago
David Hammen
10.1k11544
10.1k11544
add a comment |Â
add a comment |Â
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Stars don't fuse helium to beryllium, Be-8 has an extremely short half-life. Beryllium isotopes are produced by cosmic ray spallation.
– PM 2Ring
3 hours ago
Thx PM for highlighting my mistake, I did some more research and see Small ->H->He, Medium go up to Carbon. However massive stars go up Copper and more, I thought fusion stopped at Iron. enchantedlearning.com/subjects/astronomy/stars/fusion.shtml
– MiscellaneousUser
2 hours ago
You're right: stellar fusion does stop at iron / nickel. But in a hot star with sufficient neutron flux heavier species can be "cooked" by the s-process.
– PM 2Ring
2 hours ago