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Questions tagged [star]

Questions regarding large spheres of plasma undergoing fusion.

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82 views

Stars readjusting themselves in the sky [duplicate]

I had a meeting in the evening and thought of grabbing a snack before that. I stepped out of the office along with a colleague. He was on his phone and I was simply staring at the sky wishing it would ...
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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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0answers
25 views

Are horizontal branch stars fully convective?

I know that RR Lyrae stars are convective (this is suspected to be part of the cause of the Blazhko effect), but I would like to know more generally: Are RR Lyrae fully convective? Are all HB stars ...
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2answers
277 views

Hottest Possible Hydrogen-Fusing Stars

I guess this is more a question about stellar models than anything else. I was wondering what is predicted to be the hottest possible stars that would still be hydrogen-burning. What complicates ...
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Theoretical values of radius and mass of O9.5 II star

Where to find please theoretical values of radius and mass of O9.5 II star? I mean something like in this article. However, there are only O I, O III and O V stars in this article.
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3answers
134 views

How do we measure distance in space?

I know that you can calculate the distance to another star for example, by using the phenomenon redshift to determine how much it has redshifted because of the expansion of the universe. But how do ...
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3answers
151 views

Can a black hole “supernova”?

In layman terms: nothing ever escapes the pull of a black hole, not even light when a large star reaches the end of it's life you get a supernova sometimes the "remains" of these stars can turn turn ...
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really fast moving star-like light [duplicate]

I don't know ANYTHING about astronomy but I know what I saw and 2 of my siblings saw it too. I initially thought it was a shooting star, but a Google search quickly made it clear that it wasn't. it ...
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2answers
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Ludwig's star distance

Mizar and Alcor, each about 83 light-years away (in fact Mizar presents system of four stars and Alcor is binary system. It is not yet known if those 6 stars presents one or two star systems. In ...
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1answer
46 views

Given a star's mass, age, and composition, how do I calculate the rest of its properties?

If I'm given a star's starting mass, starting composition (metallicity), and its current age, How do I calculate the star's luminosity, current mass, and radius? I want to know how to do this for any ...
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1answer
44 views

How is stellar mass of a galaxy obtained?

I believe there is a difference between the mass calculated using the orbital speed and the stellar mass of the galaxy. So how is the stellar mass calculated? Thank you :)
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1answer
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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. ...
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1answer
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How do I find stars within milky way using galactic latitude and longitude

I have data that contains galactic latitude and longitude of stars. I have to determine all the stars that are within our milky way. How do I find it?
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3answers
218 views

Why doesn't it hurt to look at stars?

If I stare at the sun, it's bright and blinding. However, if I look at a star in the sky, it doesn't hurt. What causes this loss of energy that would otherwise damage one's eyes?
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49 views

What is the most mass that matter likely to form?

If we plot graph between accumulate of forming mass (y-axis) and mass (x-axis), where is the maximum ? There is a story how I get this question. It start when I think about question "Is our sun is ...
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1answer
36 views

What limits the use of the H-R diagram to measure distance (main sequence fitting), what distances is it useful for?

Is it only possible to measure objects that form around the same time? Is it possible to measure clusters from distant galaxies other than our own?
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1answer
67 views

How to differentiate elements that have same spectral lines in a star?

Suppose that iron and calcium have a spectral line with the same wavelength. How would you determine which element is present in the atmosphere of a star if you found this line in its spectrum?
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1answer
41 views

Eddington luminosity in various plasmas

So I know that the Eddington luminosity is given by: $L_{Eddington} = 4\pi GMc/\kappa$. I want to calculate this luminosity for a plasma of purely ionized helium, as well as for an electron-...
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2answers
228 views

Can a star fall in a super massive black hole without getting destroyed?

This is the first of many similar questions I have to build up to a specific question or scenario that I want to explore and find an answer to.
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2answers
97 views

Why does the sun have a convection layer and a radiation layer?

Why is the outer section of the sun convective but the inner section stable and only radiative? They are both made up of the same kind of matter, both heated by the core.
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Is there a database of all known star names/identifiers?

I am looking for a list of all known identifiers used for stars. I'm not sure on the terminology. While I do want the "proper names", I also want whatever identifier is used for each star detected, ...
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1answer
53 views

Is there a theoretical minimum mass main sequence star that can become a red giant?

Wikipedia's Red Giant page says they range in mass from 0.3 to 0.8 solar masses. Which corresponds to an initial mass of a bit less than 1 solar mass, about 0.8 or so, if I was to estimate and a few ...
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2answers
70 views

Are red giants stationary or do they move? [closed]

A friend and I are having a friendly chat about this. They are stars so I'm claiming they still move in orbit.
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2answers
134 views

Why does star formation cease?

The universe is expected to have a time when star formation slowly ceases. However, this seems bizarre as there is always an abundant amount of matter in the Universe. Massive amounts of hydrogen ...
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1answer
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Do astronomers have any idea what percentage of our galaxy’s stars move in retrograde orbits?

I recently noticed that none of the planets in our solar system orbit the Sun in a retrograde direction. This is likely because they formed moving in the same direction as the planetary disk did in ...
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3answers
56 views

Are white dwarfs the ones always absorbing mass from a companion?

It seems to me every time I see stellar remnant binary systems where there is a white dwarf and another star or something, it appears that the white dwarf always pulls mass from the star. What if the ...
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3answers
148 views

Can Earth be ejected out of the solar system this way?

I found this image of what maybe a model of our solar system. Without a credible source I'm not sure I am looking at a star or black hole that comes close to our solar system and how it could throw ...
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1answer
72 views

Is it possible that in the Local Interstellar Cloud there are undetected stars?

The Local Interstellar Cloud is supposed to be around 30 light years large. Is it possible that in this region there are stars which are undetected? I would have thought that it wasn't possible, but ...
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1answer
84 views

When a rogue brown dwarf star hits a white dwarf star, will the collision at most cause a nova? [closed]

When a rogue brown dwarf star hits a white dwarf star, will the collision at most cause a nova? Or can the explosion be heavier?
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52 views

Could you tell me this constellation name? [closed]

Hi Everyone please check this pictures could you tell me this constellation name ?
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3answers
115 views

Stars located outside of a galaxy

How common or rare is it to find stars outside of a galaxy? Can such a star still have planets that contain life? Recently, I think that I heard of a star with a planet that entered our Galaxy. Did ...
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3answers
1k views

Beta Andromedae (Mirach) and distances mentioned in original Cosmos series from 1980

In one of the episodes from Carl Sagan's show Cosmos he explains that Beta Andromedae is the second brightest star in the constellation Andromeda, and is 75 light years away. The link to the video is ...
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1answer
123 views

Are brown dwarfs which dont sustain any fusion considered stars?

I was reading about the coolest stars , and surprised to find about stars with a surface temperature lower than a candle, like 2MASS 0939-2448 A/B, of about 100 celsius like CFBDSIR 1458+10B and even ...
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1answer
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What's the white glow around this star?

A few days ago, I took a photo of the night sky in the mountains of Georgia with my DSLR. There, I noticed that one single star (in the center of the part of the photo that I added below) looks very ...
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1answer
50 views

If the axis of the Earth was through Greenland, what would the north celestial pole be? [closed]

If the axis of the Earth was through Greenland, what would the north celestial pole be?
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43 views

Regarding the VizierR catalogue

I want to build a Machine Learning model to approximate effective temperatures of stars based on their B-V index but there aren't that many catalogues that include that. I came across the Vizier ...
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1answer
52 views

How many horizontal branch stars are within 2 kpc of the sun?

For my research purposes, I am wondering how many horizontal branch (HB) stars are within 2 kpc of the sun? I tried to find some with the Gaia DR2 data with a magnitude cut that leaves HB stars out ...
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3answers
174 views

How do we know distant stars still exist

The Pleiades are 450 light years away. Thus when we see the twinkle in the night sky the light that hits our retina emanates from the year 1569 or so. On that proviso; how can we be sure that the star ...
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2answers
4k views

Could stars form outside of galaxies?

Is it possible for there to be a dense enough nebula to form stars outside of any galaxy? Does a galaxy have a minimum size to produce stars? Or could you have a few dozen stars clustered together by ...
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38 views

Geographical Substellar position calculation from RA/DEC

I was trying to help my son with a project and thought it shouldn't be hard but turned out I'm not as smart as I thought I was. His project is about celestial navigation. The first step is, given the ...
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1answer
126 views

Is it possible for stars not to rotate?

I'm just curious about that the existence of non-rotating stars. Is it physically possible for a star not to rotate at all? Does magnetic braking eventually stop the stellar rotation?
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1answer
54 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 ...
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1answer
60 views

Hubble Space Telescope (HST) observing modes

I have been reading some literature on using the HST to take spectra of exoplanet atmospheres when exoplanets transit in front of their stars. The literature mention two modes of observations, '...
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1answer
83 views

Why do most of the myths behind constellations originate from Greek? [closed]

Why do most of the myths regarding constellations happen to have begun from Greek civilization? Why not other civilizations? Most people who lived in the past era probably observed star patterns in ...
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1answer
39 views

Possibility of certain conditions on a planet [closed]

I want to know if there can be any planet that can fulfill the following conditions and if any planet has been observed with such characteristics: The planet must not be tidally locked. The day-night ...
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2answers
99 views

How to Distinguish between Temperature and Doppler effect using Black-body radiation?

I understand that the radiation of a body can be described using the curve for black-body radiation. In the sense that a hotter body will be blue shifted and a cooler body will be red shifted. The ...
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2answers
3k views

Are we really star-stuff from the interior of collapsing stars?

Carl Sagan has said several times that we are "star-stuff". One instance can be found in Good Reads' Carl Sagan > Quotes > Quotable Quote: The nitrogen in our DNA, the calcium in our teeth, the ...
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0answers
45 views

Can you go blind if you look at the sunrise and sunset? [duplicate]

Everyine knows its dangerous to look directly at the sun, but can you look safely at sunrises and sunsets without going blind? Because the uv radiaton and the light is much weaker. Or is it still very ...
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1answer
513 views

Why are blue stars the hottest? [duplicate]

I know that blue stars are the hottest and youngest (according to Universe Today). But what makes them blue, instead of other colors like purple?
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0answers
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Strength of core-envelope coupling in stars

For a star with a given Zero-Age Main Sequence (ZAMS) mass, as a function of metallicity how strongly is the star's core coupled to its envelope? I understand that the core-envelope boundary is only (...