Questions tagged [star]

Questions regarding large spheres of plasma undergoing fusion.

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1answer
66 views

Why are accreting objects portrayed with a white flash at the point where the gas stream from the star enters the accretion disk?

When I see images of accreting objects, the gas from the donor has a white flash where it meets the accretion disk, like in the image below. Why does this happen if it is true, and why is it there?
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Is a star with 2/3 solar masses and 9/10 solar radii still in the main sequence?

As far as I know, K-type and G-type stars (among others) grow in radius as they age, eventually leading to red giant phases. My question is, would a star that is about 0.66 solar masses and 0.94 solar ...
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Is is possible for a main sequence star to have 0.77 solar masses yet only be 0.54 solar radii?

I know ordinarily a star's mass and radius tend to be proportional, so a 0.5 solar masses star tends to be about 0.5 solar radii and have a density of 4.82 g/cm³, 3.42 or about three and a half times ...
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46 views

Can a Thorne-Żytkow object be the progenitor of a modern quasi-star?

I was reading some Wikipedia articles about astronomy, and came across an interesting line: The neutron star may also accrete sufficient material to collapse into a black hole. Now, here is my ...
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Can mass loss via accretion occur on stellar remnants?

We know that normal stars can lose mass to a binary companion. But can this happen to neutron stars and white dwarfs? Let's say a stellar black hole is being orbited by a white dwarf or neutron star. ...
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1answer
67 views

Why do M dwarfs emit more X-ray radiation than larger, more luminous stars?

I have read that "The relative amount of harmful radiation (to life as we know it) that stars emit can be 80 to 500 times more intense for M dwarfs relative to our Sun". Source This seems ...
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What would happen if a neutron star merged with a white dwarf?

We've heard of neutron star mergers and white dwarf mergers. But what would result in a neutron star merging with a white dwarf? Would there be a similar super/kilonova, are there any examples of it, ...
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1answer
56 views

What increases or decreases the mass and density of a fixed radius star?

Assuming a relatively even proportion of mass and radius, a 0.25 solar masses and radii star would have a density of 22.5003 g/cm³, or about 16 times our Sun's density. Keeping the radius of 0.25 ...
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1answer
87 views

Fate of a planet orbiting a Lagrange point behind a star?

Let's say there is a planet orbiting at L5 behind a star, which is in turn orbiting a more massive star, like so: What is the ultimate fate of this planet? I'm predicting that it will spiral into the ...
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2answers
47 views

What factors influence a star's temperature and density?

Assuming a relatively even proportion of mass and radius, a 0.25 solar mass and radius star would have a density of 22.5003 g/cm³, or about 16 times our Sun's density. However, there is obviously a ...
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Are red dwarfs really 30-100 times our Sun's density?

This article by K. E. Edgeworth claims red dwarfs tend to be around 30-100 times our Sun's density. However, this seems a bit high. With smaller stars, mass tends to be proportional to radius but ...
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1answer
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What percent of all stars that have lived (up to now) are stellar remnants?

According to this post, I found that about 90% of all stars are main sequence stars. So I am assuming that the other 10% consists of protostars, older giant stars, and stellar remnants. So I'm ...
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1answer
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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 ...
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1answer
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The star that died and became the Crab Nebula and Crab Pulsar?

The supernova of this star was witnessed about 1 thousand years ago, and the star's remains are the Crab Nebula and Crab Pulsar. What is this no longer existent star called? How massive was this star? ...
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When a fast-moving star goes supernova, how will the resulting remnant evolve?

Let's take a massive star that has zero velocity. When this star goes supernova, the resulting supernova remnant will expand in a sphere. But, let's take a runaway star travelling at 200 km/s. I am ...
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2answers
101 views

Are any of the zodiac stars about to go supernova anytime soon?

I have read that Betelgeuse, known as Ardra in Hindu astrology, could go supernova. Are any of the zodiac stars or the stars of lunar mansions about to become a black hole or supernova?
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Galactic orbits and distance between stars

In the context of whether or not nearby stars were created from the same nebula, this answer states: imagine two stars with very similar orbits, one with a period of 200 million years and the other ...
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1answer
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Exoplanet dip in transit light curve when the planet passes behind the star

In the animation below, I don't understand why the brightness slightly decreases when the planet is behind the star. Where does this effect come from?
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What is the difference between 'Gravitational radius' (r_grav) and 'Schwarzchild radius' (r_Sch)?

From ResearchGate: https://www.researchgate.net/figure/Top-panel-Stellar-radius-as-a-function-of-stellar-mass-and-surface-temperature-given-by_fig3_313716289 I thought that 'Schwarzchild radius' ...
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2answers
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After a supernova, why don't new stars coalesce with higher heavier element content?

May be a beginner's question but I couldn't find the answer anywhere. Given a supernova event and the cloud left by it, why does a new star coalesce with a disproportionally higher hydrogen(and helium)...
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1answer
57 views

Blue, red, and white star? [duplicate]

At 6:30pm central time in the USA I saw a rapidly twinkling red blue and white star in the sky. It was about south east and I was really confused. I looked it up it might be Sirius but I'm not sure. I ...
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1answer
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Why is T-Tauri So Dim?

I'm looking at stellar objects and doing some math here and... Now, I can't find these values directly listed, but from it's relative magnitude and distance, (10.27, 471ly,) I calculate T-Tauri to ...
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New method for exoplanet detection?

Could it be possible to detect exoplanets that have an abundance of iridescent minerals by analyzing their star's spectra over time as the angle in observation would lead to changes in absorbed ...
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What if a planet or another star or ¨sun¨ collided with our sun? [duplicate]

Stellar collisions are a well-studied phenomenon in Astronomy, albeit mostly theoretically. In some cases the merger of two low-mass stars can result in a new star plus new planets around it. But what ...
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1answer
77 views

Could a star become a planet?

Could a star become a planet? I am asking this because the gas giants are ¨Failed Stars¨ and they are classified as planets in our solar system.
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1answer
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Would dropping a white dwarf or a “still-hot” stellar core into a large planet or brown dwarf create a star?

In the Wikipedia article about stellar engineering, I found this quote: In The Saga of the Seven Suns, by Kevin J. Anderson, humans are able to convert gas giant planets into stars through the use of ...
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1answer
57 views

Any known Triple Star Systems with this hierarchy?

I'm curious, are there any known STABLE triple systems in which a close inner binary pair is orbited by a more massive star, yet the total mass of the binary pair is greater than that single orbiting ...
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1answer
251 views

If two stars collide, what is the probability that they merge to form a single star?

After looking at What are the odds that the Sun hits another star? and answering it (crudely), now I'd like to ask the following: What is the probability that if two stars collide, their cores merge ...
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What are the odds that the Sun hits another star?

The Sun moves around the Milky Way disk in the same direction as most of the other stars in our galaxy (prograde). But there are a number of older stars in the galactic halo that move in retrograde ...
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1answer
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Modeling egg shaped stars

I am well aware of one-dimensional stellar models: The simplest commonly used model of stellar structure is the spherically symmetric quasi-static model, which assumes that a star is in a steady ...
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1answer
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Approximate spectral type and luminosity given apparent magnitude and distance

I am looking at the data acquired from the Gaia DR2 survey. I found that most of the stars had their distance and apparent magnitude catalogued, but not their spectral type and luminosity class. Is ...
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3answers
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If an orbit is shifting due to orbital precession, is it still a Keplerian orbit?

I was thinking about orbits a few days ago, and realized that orbits shift/precess naturally. Given that a two-body problem with a star and a planet, if the planet has an eccentric orbit that ...
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1answer
62 views

How do we differentiate between a star or planet and noise introduced due to equipment?

I understand that differentiating between celestial bodies and noise due to equipment is a fundamental problem in astronomy. I also understand that we solve this problem by looking at something called ...
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2answers
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Are there any stars that orbit perpendicular to the Milky Way's galactic plane?

Most stars orbit in the Milky Way's galactic disc. But is it possible for one to orbit perpendicular to it? Here on Earth since we're inside the galactic plane we can't get a good view of what the ...
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1answer
37 views

How does the stellar evolution for low and intermediate mass stars differ?

I'm trying to understand stellar evolutionary tracks for different masses. So far I have the general understanding from a cloud of gas and dust to a white dwarf, neutron star or black hole. What I don'...
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1answer
64 views

Exactly how long does it take for the exposed core of a star to cool from its starting temperature (several billion K) to ~50,000 K?

OK, I didn't know how I should word this question. But the basic point is that most white dwarfs that we have classified fall in temperature ranges from ~50,000 K to 6000 K. However, at the end of a ...
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1answer
132 views

Stellar life cycle flow chart with mass conditions and time scales

I remember that in my nuclear astrophysics lecture a decade ago, our lecturer drew a large flow chart like diagram of stellar evolution in dependence of the mass of the star (in solar units) on the ...
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2k views

What Constellation Is This? (Photo Included)

Observed on 9th of Jan 2021 in Newcastle Upon Tyne (UK) looking WSW at a little after Midnight.
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1answer
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How co-planar and co-rotatory are the Milky Way and its constituents?

All the planets in the solar system rotate roughly in a plane that intersects the sun. Stars in the Milky Way rotate around its centre forming a rough planar disk. Question Are these planes all ...
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2answers
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Eta Cassiopeiae star type; G0V? F9V? Both?

For a story I am looking into the star system of Eta Cassiopeiae, which is a binary with a main sequence star called Achird (very similar to the sun) and a K7V star. The issue I am running into is the ...
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1answer
49 views

Why doesn't star size distribution conform to space rock size distribution?

The number of space rocks is exponentially related to the size of the rocks. There are more small space rocks than big ones. Stars are most commonly the size of the sun, big and smaller stars are rare,...
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1answer
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Is there a retrograde star that passes closer to the galactic center than our Sun?

Our Sun is moving in a prograde orbit around the galactic center with a distance of about 8 kpc. This paper says there are many retrograde stars in the galactic halo 10-20 kpc from the galactic ...
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Relation between core mass and red giant mass?

Yes, the title might be confusing (I'd appreciate some more clarification on it :D ). I have an estimated mass of hydrogen in the core of a star, and how much hydrogen will be in the core when the ...
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1answer
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Why could Quasi-stars (“black hole stars”) have only existed when everything was hydrogen and helium? (no metal “contamination”)

This informative answer to What was the absolute limit to the possible sizes of the first stars formed from “primordial material with no metals”? led me to Wikipedia's Quasi-star; Formation and ...
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1answer
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Is HR 5171 a Spectroscopic Binary or a Symbiotic?

Is HR 5171, the largest yellow star in the galaxy a symbiotic star where one feeds off the other? Or is it a spectroscopic binary where its only possible to determine that there are two stars by ...
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1answer
59 views

Dataset for machine learning MK stellar classification

I would like to create program for automatic Morgan-Keenan stellar classification using machine learning. For that, I need dataset of stars with known absolute magnitude, temperature and luminosity ...
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0answers
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How to calculate the limb darkening $\mu$ value

I am reading about limb darkening and I am very confused how to find the value of $\mu$. It states it can be found by $\mu = \cos(\gamma)$, but I am lost how $\gamma$ is found, or what it represents. ...
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2answers
111 views

How much solid matter is in the observable Universe?

I want to know the volumetric ratio of empty space to planets, stars, and all other solid matter combined. Not considering any dark matter, dark energy, or black holes. For example, you can say X ...
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1answer
100 views

Do stars twinkle when seen from Mars' surface?

Mars' average atmospheric pressure is 0.006 atm (0.088 psi). Is that enough to make fixed stars on Mars' night sky twinkle? Do we know an air pressure or density limit for that?
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1answer
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Origin as binaries and multiple system

The majority of hot stars originate as binaries or multiple systems. How is it with the cooler spectral types? Are they usually born as single stars? Many thanks.

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