Questions tagged [star]

Questions regarding large spheres of plasma undergoing fusion.

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3answers
228 views

Why can't this be the simple (and obvious) explanation for the dimming of KIC 8462852?

Couldn't it be just a relatively large object, anywhere in the interstellar space between the star and Earth? I mean, look out the window at a far away car or a tree, then stretch out your hand and ...
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3answers
3k views

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
104 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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1answer
218 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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1answer
44 views

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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2answers
61 views

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 ...
3
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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 ...
36
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2answers
4k views

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
33 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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2answers
81 views

Which star has the highest mass loss rate?

We have known lists of stars with high luminosity, temperature, mass, size, and much more. However, I have not seen a list that compares each star's mass loss rates. So, which star (or stars) have the ...
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1answer
61 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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3answers
692 views

Is it possible to predict a supernova with years or decades of advanced notice?

I know star phenomena like solar flares can (at some degree) be predicted: https://www.dailymail.co.uk/sciencetech/article-5371481/Scientists-predict-solar-flares.html Question: Is there any ...
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3answers
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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
53 views

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
47 views

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 ...
2
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1answer
47 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
179 views

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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24 views

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 ...
3
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1answer
48 views

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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2answers
41 views

Naming convention for multiple star systems

Okay, so I've seen different notations for the stars in β Capricorni. Some sources state that the stars are Aa, Ab1 and Ab2, Ba, and Bb, while others say that they are Aa, Aba and Abb, Ba, and Bb. So, ...
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2answers
417 views

What was the absolute limit to the possible sizes of the first stars formed from “primordial material with no metals”?

This answer to Why don't or (can't) stars be more than 325 or so times the mass of the sun? What limits their size? includes the following: ...The upper limit you refer to is for compositions similar ...
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1answer
22 views

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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2answers
104 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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0answers
47 views

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. ...
2
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1answer
67 views

Blackbody curve in RGB for objects less than 1500 K?

We know the colors of stars that have a temperature greater than 1000-1500 K, shown here. However, I am wondering about those stars/brown dwarfs with surface temperatures of less than 1500 K. Is there ...
27
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1answer
2k views

Why don't or (can't) stars be more than 325 or so times the mass of the sun? What limits their size?

Is there a particular reason(s) why stars cannot grow as massive as they want to? And why doesn't this limit apply to supermassive black holes?
2
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1answer
31 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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4answers
3k views

What spectral type of star has an absolute magnitude of exactly 0?

We know that Vega is the star that serves as the zero point for the UBV color scale, and has an apparent magnitude of nearly zero (+0.02). But its absolute magnitude is +0.58, making it rather far ...
7
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1answer
94 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
2k views

What does designation VY, NML, UU in star names stand for?

I've read the a IAU page on the subject but i am no closer to understanding how this works. Also did search the already asked question, but didn't see anything on the subject. What does bolded item ...
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0answers
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Yesterday I saw multiple moving objects in my telescope when I was looking for M31. Do you have any idea what it could be? [duplicate]

Yesterday, when I was looking at the Andromeda Galaxy in my telescope. I saw three star like objects, moving across the sky. I followed them to see what is was, though I still don't know. They where ...
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1answer
36 views

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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1answer
354 views

Why is the flux density and amplitude different for galaxies than stars?

This might be a simple question, but I'm having a hard time answering it myself - or at least answer it correctly, I think. I'm sitting with different spectrals; many for stars and one for a galaxy. ...
4
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1answer
144 views

Minimum distance between planets

In our solar system, MOIDs (minimum orbital intersection distance) of different planets reach a minimum of ~30 million miles (Mercury and Venus). However, other star systems have more compact planets. ...
6
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1answer
106 views

When was it first determined that the Sun is a star?

Just looking at the sky, it is not at all obvious that the Sun is a star: stars are fixed on the celestial sphere, they are point-like and not very bright, whereas the sun is a big (compared to a star)...
2
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1answer
40 views

Why are galactic nuclei yellow?

So we've seen millions of galaxies, and all of them have a bright, yellow nucleus. What is the cause of the yellowness? Is it because of aging stars, redshift from the SMBH, or something else?
3
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1answer
45 views

What is the length of time for each fusion process in a massive star?

In a massive star (i.e. an O5 star), first hydrogen is fused into helium, then helium is fused into carbon. This process continues to neon, oxygen, and finally silicon burning. So I am wondering, how ...
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0answers
39 views

What came first: Galaxies or Stars? [duplicate]

In Stephen Hawking's A Brief History Of Time, the book mentions that "in regions that were slightly denser than average...galaxies were born." (pg 123). However, according to many other ...
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2answers
20k views

How many stars and galaxies can be seen by the naked eye?

How many of the luminous dots that we see naked are galaxies and not stars from our galaxy? I imagine that the majority of the luminous points that we see naked eye during the night, are actually ...
4
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1answer
200 views

Are larger stars rounder?

The Earth is a very smooth sphere, and the Sun even more so, with only minor fluctuations. I am wondering: are larger stars even rounder? Intuitively, that seems self evident, but I am not so sure. ...
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1answer
4k views

What is the origin of the OBAFGKM classification system?

Once a body has been identified as a star it is classified into a subsection of either O,B,A,F,G,K or M (I think there are also 3 more letters recently added) What is the origin of this ...
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1answer
63 views

How is V1057 Cygni supposed to go from K type dwarf to F type giant?

FU Orionis variables are protostars that go through massive outbursts that drastically change the star's spectral type and magnitude. With the star V1057 Cygni, this star was known to go from a K type ...
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0answers
36 views

Mass required for a certain fusion process

Suppose we have a density model $$ρ = ρ_c (1-r/R)$$ where $ρ$ is density, ${}_c$ means central, and $R$ is the stellar radius. Let's call the temperature for that fusion process to begin, $T_f$. I ...
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1answer
68 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 ...
3
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1answer
81 views

What is the coolest white dwarf known?

Okay, so in this ArXiv report from 2014, scientists discovered the coolest white dwarf, with a temperature of below 3000 K. However, as this report was from over 6 years ago, I think this information ...
3
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4answers
127 views

How can I work out longitude and latitude through my telescope?

We purchased a Celestron Astromaster 90EQ Refractor Telescope and a Celestron Powerseeker Accessory Kit about four years ago but have not used it much for many reasons. As such my husband and I are ...
4
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1answer
39 views

Is a double quasi-binary system valid?

I was messing around with 4-body problems, and discovered a system where a close binary and a regular binary pair orbit each other. The regular binary gets disrupted every few orbits and one star ...
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1answer
76 views

What units are used for the Stefan-Boltzmann law?

I have a star with given temperature in Kelvin and radius in solar radii. I tried to calculate the luminosity of the star using Stefan Boltzmann's law, and got an absurd number (over 1 million). What ...
2
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1answer
85 views

How do we know what the biggest star is?

Kurzgesagt claims that the largest (observable) star in the universe would be Stephenson 2-18 which is in line with Wikipedia: It is among the largest known stars, if not the largest, and one of the ...
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1answer
59 views

Moving stars in the sky

Today at 7:24 pm, I saw to stars moving parallel to each other for a few seconds in the sky. Then, both suddenly vanished. What phenomenon is this?

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