Questions tagged [star]

Questions regarding large spheres of plasma undergoing fusion.

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3
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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
60 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 ...
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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
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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1answer
60 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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0answers
52 views
+50

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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3answers
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.
3
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1answer
52 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
46 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,...
3
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1answer
131 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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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
46 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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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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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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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. ...
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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 ...
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
34 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
353 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. ...
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)...
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1answer
138 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. ...
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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?
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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 ...
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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1answer
62 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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2answers
80 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 ...
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 ...
2
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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 ...
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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 ...
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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 ...
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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
38 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 ...
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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2answers
73 views

Do stars made by universe getting smaller or larger in mass? [closed]

Do stars made by universe getting smaller or larger in mass compared to stars made 180 million years after the Big Bang? If they are getting smaller, is this due to the fact that the universe is ...
5
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1answer
243 views

How do we know that 2MASS J0523-1403 is a red dwarf?

I was reading about red dwarfs, and stumbled upon this article about the least massive red dwarf, and noticed several peculiarities: The spectral type is L2.5 The luminosity class is V The mass is 67....
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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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1answer
53 views

How to improve the precision in a star's distance

When I use the Gaia star catalogue, the parallax values often have large uncertainties which, therefore, leads to a large uncertainty for the distances to the stars. If you were interested in the ...
3
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1answer
35 views

What does the “a” at the end of a spectral type mean?

Looking at the chart for spectral type peculiarities (here), I noticed that the letter a was missing from the chart. This seems to be an error, as the star Vega has spectral type A0Va, with the a ...
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 ...
3
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1answer
100 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 ...
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3answers
94 views

Is there any scientific correlation between cold nights and star-lit skies?

I've many times heard expressions such "cold, starry nights". It's apparently poetic to describe star-lit night skies as being "cold". Is this based on reality in some way? Is ...
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4answers
3k views

Can a star emit heat but no visible light?

Can a star emit enough heat to allow human life on its planets, however emit no visible light? If so, what problems would this pose?
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1answer
78 views

Is a trefoil orbit around a trinary star valid?

Recently, I have been experimenting with weirdly-shaped orbits with a program called "My Solar System 2.04." While looking for interesting orbits of a spacecraft in a trinary star, I found ...
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1answer
66 views

Why doesn't smashing larger and larger bodies incrementally into a rocky planet create a star?

Let's start with a stationary Earth. If we smash a few Mercury-sized objects into the Earth, the Earth begins to accrete mass. Repeat this step with larger and larger objects, until we start impacting ...
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1answer
58 views

what would the mass and density of Sirius A be if the mass of Sirius B is roughly the same as the Earth?

I am writing a blog post and while I am interested in astronomy I havent done any physics like this since high school. My question is: what would the mass and density of Sirius A be if the mass of ...
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1answer
47 views

Are the sub-spectral types (1,…9) based on temperature or spectral lines?

The spectral type of stars has an OBAFGKM class, along with a number, from 0 to 9. According to Wikipedia, (sample shown below), the lower the number, the hotter and more massive the star, but ...
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0answers
47 views

shape of gas and shape of stars

How does the shape of the gas and shape of stars change as the galaxy ages? Does there exists any such formula which relates the shape/volume with the time?

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