All Questions
Tagged with star main-sequence
26
questions
7
votes
3
answers
1k
views
When a star enters a red giant phase, does the pressure in its core increase or decrease?
When a star becomes a red giant, does the pressure in its core increase or decrease?
From one side, the only source of pressure in a star is gravity. A red giant is much larger than an ordinary star, ...
- 800
3
votes
1
answer
200
views
Mimimum stellar mass and minimum temperature that triggers hydrogen burning
We can derive the minimum mass of a star in the main sequence using the minimum temperature $T_C$ that triggers hydrogen burning in the core. Then using the stellar structure equations we can derive ...
5
votes
3
answers
995
views
Is it possible for a star cluster to be composed of main sequence stars?
From what I hear about globular clusters, they are primarily composed of very hot giant stars, which are not the most conducive for life as we know it.
Main sequence stars like our own, due to their ...
- 469
2
votes
1
answer
320
views
Does the mass-luminosity relation work for brown dwarfs?
There is a mass-luminosity relationship of the form $L \propto M^a$, where $a = 3.5$, that is is applicable to main-sequence stars. Is there a similar relationship that holds for brown dwarfs?
user47732
9
votes
1
answer
344
views
What does the surface of a star with a radiative envelope look like?
This image from Wikipedia shows that main sequence stars above 1.5 solar masses have a convective core and a radiative envelope. The surface of our sun grainy because of convection cells right below ...
- 1,758
3
votes
0
answers
48
views
Strength of core-envelope coupling in stars (again)
I asked this on the physics SE but it received little attention:
Consider a high-mass zero-age main-sequence (ZAMS) (e.g., $m_{\rm ZAMS} \gtrsim 30\,$M$_{\odot}$) star.
I understand that the core-...
- 4,533
3
votes
1
answer
200
views
How can I estimate how long will a main sequence star stay on the main sequence given its temperature?
I have a generic zero-age main sequence star. The only thing I know about it is its temperature. How can I estimate time time it spends on the main sequence (in millions of years)? I've seen equations ...
2
votes
1
answer
191
views
Is it possible for a star to return in the main sequence?
Is it possible for a star to return to the main sequence after entered in the post-main sequence phase? I have no clue if there's a mechanism such as acquiring hydrogen from from the environment or ...
- 316
3
votes
1
answer
325
views
What would happen to the Sun's evolution if it collided with another yellow dwarf?
How would the Sun evolve if it collided with another G-type main sequence star, perhaps a more massive one like Alpha Cen A? Since its mass would then be above the Chandrasekhar limit, could it ...
- 293
9
votes
1
answer
1k
views
Increase in Luminosity of the star
The Luminosity of a star is proportional to the 4 th power of its temperature and square of its radius. Also the mass-luminosity relationship says that the luminosity of star is proportional to ...
- 157
4
votes
1
answer
117
views
Catalogs for type K stars and their planetary systems?
I am doing data collection on all type K stars, and their planetary system so I may develop an algorithm for a planetary formation simulation with the Unity game engine.
Where could such a catalog of ...
- 203
12
votes
1
answer
434
views
Is there a relation between mass, radius, and luminosity in deuterium-burning brown dwarfs?
I'm a worldbuilder and my setting has a lot of brown dwarfs.
While I'm trying to keep my setting as science-compliant as possible, I can't seem to find any resources for brown dwarfs like there are ...
- 163
2
votes
0
answers
90
views
The mass of Subdwarf B progenitors in the main sequence
Note: By "progenitor", I mean "the star as it was when it was still main sequence". Please correct me if I've got the terminology wrong.
Most B-type subdwarfs have mass roughly half that of the Sun. ...
- 495
8
votes
1
answer
552
views
Why does the convective core in an intermediate- to high-mass star shrink?
The image below shows the evolution of the hydrogen mass fraction profile for a 5 solar mass star in the main sequence. I would expect that the size of the convective core stays roughly constant as ...
- 199
3
votes
1
answer
1k
views
Is the turn-off point of the main sequence the same as the terminal-age main sequence?
The turn-off (TO) point is one tipping point on the Hertzsprung-Russell diagram (HRD) where low-mass stars start to evolve from the main sequence (MS) toward lower temperatures. If I understand it ...
- 199
4
votes
2
answers
234
views
Does the density in the core of a "higher mass" star stay generally constant while it evolves on the MS?
We know the CNO cycle produces the majority of energy production in a "higher mass star" of approx. over 2 solar masses and the core is convective due to the large temperature gradient. My professor ...
- 1,111
6
votes
1
answer
585
views
On a Hertzsprung-Russell diagram, why is the main-sequence line squiggly?
When I look at a Hertzsprung-Russell diagram, I'm able to see a main-sequence line from the most luminous main-sequence stars at the top left to the dimmest main-sequence stars at the bottom right. ...
- 263
3
votes
1
answer
3k
views
How long does it take a star to transition from main sequence to red giant?
I have read that it takes billions of years for stars of approximately the size of the Sun to get through the main sequence, after which it will enter the red giant phase. When that happens, how long ...
- 133
11
votes
1
answer
551
views
How does a star's rotation affect a star on the main sequence?
I searched and have found that the questions mainly focus on neutron stars, white dwarfs and black holes. This was not what I want.
Basically, the bigger the star's mass is, the more intense its ...
- 263
15
votes
2
answers
5k
views
Does a star fuse helium to beryllium on the main sequence?
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 ...
- 1,311
1
vote
0
answers
63
views
Are there simplified M-L, M-R, and lifetime equations for non main sequence stars?
To give some context - I am trying to create a simple program that outputs the stellar properties of a star when given its initial mass and current age.
e.g.
Input
Initial Mass = 2e30kg
Age = 4.6 ...
- 11
4
votes
4
answers
4k
views
Why is the main sequence often called 'zero age' main sequence?
The main sequence stage for a star begins after it stars burning hydrogen into helium. This is often referred to as the zero age main sequence.
This is confusing since stars have already lived ...
- 822
4
votes
2
answers
659
views
Why do post main sequence stars enter the red giants branch?
I am an early graduate student in astronomy and have hard time understanding why do post-MS stars move up the RGB.
Here is what I understand about post main sequence evolution of stars. As their ...
- 41
4
votes
1
answer
2k
views
What is the largest hydrogen-burning star?
I am wondering what is the largest known core hydrogen-burning star? A look at the list of largest known stars on Wikipedia seems to indicate VV Cephei B (at the bottom of the list), but I would like ...
- 2,673
4
votes
1
answer
292
views
What's an order-of-magnitude main sequence star look like?
I'm looking for a very rough, order-of-magnitude approach to the main sequence.
What I mean is, I have a spherically-symmetric hydrogen distribution. I'm looking to get a rough approximation for ...
- 173
3
votes
2
answers
600
views
How can pre-main sequence stars radiate more energy than main-sequence stars?
How can a pre-main sequence star radiate more energy by gravitational contraction than a main-sequence star can by hydrogen fusion?
- 133