Questions tagged [main-sequence]

Questions about the "adulthood" of stars. The main sequence is a distinctive band of stars that appears in a color-magnitude plot (known as Hertzsprung-Russell diagram). Stars appear in the main sequence when they are burning hydrogen in their core.

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4
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2answers
80 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 ...
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1answer
110 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. ...
2
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1answer
76 views

What will be the temperature on Earth when Sun finishes its main sequence?

We know that presently Sun is 4.5 billion years into its main sequence. It has another 5 billion years before it enters the Red Giant phase. We also know that Sun's luminosity increases by 10% every ...
3
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1answer
67 views

How to obtain distance modulus and Total extinction from Isochrone fitting to CMD?

This is my first post here. I am studying the following article: https://arxiv.org/abs/1901.03574. On Page 5, Sec 3.1, the authors are presenting their results they obtained via Isochrone fitting ...
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1answer
75 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 ...
8
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1answer
66 views

How a star's rotation affects a star in the main sequence?

I searched and have found that the questions mainly focus on neutron stars, white dwarves and black holes. This was not what I looked for. Basically, the bigger the star's mass is, the more intense ...
14
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2answers
3k 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 ...
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0answers
41 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 ...
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3answers
775 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 ...
2
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2answers
364 views

Which would be safer: removing hydrogen or adding hydrogen to our sun?

If we want to extend the lifespan of our habitable zone safely, would it be safer to institute a yearly 'tax' on our suns outer layer of hydrogen, or a yearly 'subsidy' to our suns outer layer of ...
2
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0answers
307 views

What characteristics or patterns do galaxies have on color-luminosity chart? [closed]

For the following graph, I have some confusions: How do galaxies rank by mass? We know that on main-sequence, more luminous stars are also more massive, so I guess it also applies to galaxies. Do red ...
2
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1answer
800 views

Why are main sequence stars more massive than the Sun less dense? e.g. Vega, Spica etc

Why do main sequence stars more massive than the Sun have lower densities? e.g. Vega, Spica etc.
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2answers
357 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 ...
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0answers
113 views

Why does spectral class and U-V colour correlate slightly differently for main sequence, giant and supergiant stars?

In this diagram the $x$-axis is spectral type for stars and the $y$-axis is B-V colour. Taking Series 1 as the Main Sequence, Series 2 as Giants and Series 3 as Super-giants. Why the spectral class ...
4
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1answer
1k 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 ...
12
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4answers
913 views

Is “Main Sequence” a temporal sequence?

Stars plotted by luminosity and surface temperature fit into patterns in a Hertzsprung–Russell diagram. A rough diagonal subset of this plot is called the main sequence. Is this in any sense a ...
4
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1answer
879 views

Is the conversion from proto-star to main sequence an event or a process?

When a proto-star becomes a main sequence star, is that something that happens in an instant when a certain threshold is met, or is it a process that takes a few thousand/million years?
1
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1answer
90 views

Accretion of in-falling material for a young main sequence star

I'm reading material that is seemingly contradictory. Some sources indicate that the evolution of a protostar to a main sequence star is characterised by a stellar wind that precludes the accretion ...
3
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1answer
182 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 ...
3
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1answer
240 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?
10
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1answer
705 views

Timescale of ignition of a protostar?

What is the timescale of start of nuclear fusion as T Tauri type star transforms into a Main Sequence star? Wikipedia article on T Tauri type stars mentions: Their central temperatures are too low ...