Questions tagged [star]

Questions regarding large spheres of plasma undergoing fusion.

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16
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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
65 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
53 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
49 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
44 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
44 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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1answer
125 views

Relation between absolute magnitude of UV and star formation rate

I surfed the internet and searched a lot of sites, so far I got this but unable to find the formula which relates only Muv and the Ψ as I don't know the value of parameters Auv and μ(z). If there ...
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1answer
38 views

How were the distances to stars measure before parallax?

A comment under When was the distance to a star measured for the first time without using parallax? mentions that the distance to stars was measured before parallax was possible. How was this done?
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1answer
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Can red dwarf stars have a spectral type of L?

We have the "normal" main sequence stars, OBAFGKM. Below K and M are the brown dwarfs, L,T, and Y. Zooming into the area at the edges of M and L, we have spectral types M9, M9.5, L0, and L1. ...
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2answers
86 views

When was the distance to a star measured for the first time without using parallax?

This is somewhat of a follow-up to When was the parallax of a star first measured? Once the distance to the nearest stars was determined, it was possible to discover physical properties of stars (such ...
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0answers
41 views

Dependence of shape of stars and gas in galaxies on dark matter halo

I have studied about galaxies having different shapes. But do the stars and gas in galaxy have different geometrical shape separate from each other. What factors decide this? I think that the mass of ...
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0answers
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From what distances do the atoms in you come from?

If the atoms of a human come from stars, comets, nebulas and magnetrons, then what is the greatest distance that two atoms of a human can possibly have been away from each other previously? Perhaps ...
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4answers
907 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 ...
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1answer
38 views

Calculate the absolute magnitude for a multi-star system

We know that the absolute magnitude of a single star can be calculated with the formulae: $$M_{\rm bol} = 4.75 -2.5 \log_{10} \left(\frac{L_*}{L_{\odot}}\right)\ ,$$ $$M = -2.5 \log_{10}(L_* / L_0),$$...
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2answers
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Is there an O1 or O0 star?

Okay, we've seen the super hot Wolf-Rayet stars, especially WR 102 and 142, and the "slash stars," many of which are early O (O2-4.5/WN). We know the temperatures of these Wolf Rayet stars. ...
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1answer
149 views

Evolution of galaxies with time

I am doing an Introductory course in astrophysics UG level. I have studied that mass of the gases ($M_{gas}$) decreases with time as new stars are formed but mass of stars ($M_{star}$) doesn't ...
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0answers
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Plotting Histograms of stellar mass and gas mass given a halo mass

I am an undergrad doing a first course in astronomy. I am working on a small project. In it I have been assigned a halo mass (1.444e12 $M_{sun}$). I want to plot histograms of possible stellar masses ...
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2answers
252 views

Is there a formula for absolute magnitude that does not contain an apparent magnitude term?

I have a star that I need to calculate the absolute magnitude of. I am given the temperature, luminosity, radius, mass, and distance in light-years. So I am wondering, what is the formula to compute ...
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1answer
111 views

What is the distance from Alpha Centauri to Barnard's Star?

Alpha Centauri AB is the closest star system to Earth (4.366 ly), followed closely by Barnard's star (5.988 ly). The closest star system to Alpha Centauri is Luhman 16 (3.8 ly from α Cen). So I am ...
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1answer
444 views

Increase in Luminosity of the star

The Luminosity of a star is proportional to the 4 th power of its temperature and square of its radius. Also the mass-luminosity relationship says that the luminosity of star is proportional to ...
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1answer
961 views

Why do stars rotate slower than they're expected to?

Due to conservation of angular momentum, I thought most stars would be spinning extremely fast because they have a relatively small diameter. However, it turns out that this is not true and most stars ...
2
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1answer
90 views

Where can I find thousands of actual images of stars in the galaxy?

I'm trying to write a program to differentiate between images of stars and nebulae. However, I'm not able to find a large enough dataset of actual images of stars that I can use to train my deep ...
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0answers
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What was the train of lights (30+ in a row) that went south toward north then disappeared tonight in Turnersville Texas? [duplicate]

The lights were bright and looked like stars that moved together in unison in the formation of a Double forward slash Ex: // but nearer together made up of (I’m guessing from what I saw)at least 30+ ...
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2answers
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Can lightning occur in stars like the Sun?

In the Wikipedia article about lightining, the following explanation is given about the electrification process in clouds: The details of the charging process are still being studied by scientists, ...
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Do apparent magnitude (V) and photometric magnitude (specifically in optical V band between 500-600 nm) have a similar scale to stellar magnitude?

I'm graphing a table and I used the magnitude values from this database https://vizier.u-strasbg.fr/viz-bin/VizieR-4 (It's the V/19/data catalog for "Masses and Ages of stars in 68 open clusters&...
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1answer
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What is a UBV source for stars or stellar objects?

I was using the V19(VizieR) catalog and the main identifier of the stars was in terms of an 'ID' number which they mentioned as being 'Star number in UBV source' I have no idea what that means. How ...
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1answer
82 views

Will the Sagittarius A* Black Hole eventually swallow the entire Galaxy?

In one of his interviews, Sir Roger Penrose mentioned that when the Milky Way and the Andromeda galaxies eventually "collide" and merge into one, their super-massive black holes will also ...
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1answer
50 views

Star designation

There are several designations for most of the stars (left column in the picture). What is the name of designation for names like Alnilam, Sirius, Alhara ... How to call these names? Thanks
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0answers
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How do you create a continuum mask in Python or IDL for a star? [closed]

I'm learning how to model stellar spectra using the IDL code, Spectroscopy Made Easy (SME), and its Python counterpart, PySME. Has anyone used these programs before? As you can see from the first ...
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1answer
105 views

Is there a website out there where I can find/compare data on stellar parameters for the brightest stars?

I'm looking for some kind of catalog/repository which lists stellar parameters (e.g. mass, radius, temperature) in a similar vein to NASA's Exoplanet Catalog (but except for stars), for the brightest ...
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1answer
90 views

Is there a possibility of finding a system where a star is orbiting a planet?

Is it possible for a star to orbit a planet IF the planet is bigger than the said star? Or is it possible even if the star is bigger than the planet and still the star is orbiting the planet? I have ...
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1answer
143 views

What is this planet or satellite in this picture?

I took this photo in Shijiazhuang, Hebei Province, China, 38°13'N 115°18'E (+38.23, +115.31) on the night of February 8, 2020. Here you can see a round object above the moon, and it was moving fast,...
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1answer
41 views

Relation between age and spectral type of star

Does the spectral type of a star change as it ages? Since its temperature changes, I suppose the spectral type should also change, but I'm a bit confused about this. Also, is the spectral type ...
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1answer
56 views

Is most hydrogen in the universe in the form of plasma, atomic neutral hydrogen, ionized hydrogen, or molecular?

I have had trouble finding an answer somewhere.... Some places say most hydrogen is plasma, such as the stuff stars are made of (mostly) and the 'warm-hot intergalactic plasma'. Other places say ...
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1answer
42 views

Alfven Radius of mainsequence stars

Is there any average value for the Alfven radius of main-sequence stars? if there are no such values, then how may I calculate it??
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0answers
48 views

How to find the temperature of a planet accounting for the atmosphere?

Recently, I started writing a program to generate star systems, and I need a formula to find the approximate surface temperature of a planet. I know of several formulas for this, for example this one ...
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2answers
1k views

Are there stars with an average density greater than the central density?

Are there likely to be stars for which the average density is greater than the density at the centre? Intuitively, I would say not, as density tends to decrease outwards, but ideally I would ...
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0answers
164 views

Which star has the lowest absolute magnitude?

I have seen many lists of stars with the most luminosity, mass, and temperature, but I have never seen one that is about absolute magnitude. So I'm wondering, which star has the lowest absolute ...
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0answers
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What does the Sun “look like” below 100 MHz?

Radio2space.com's The Radio Sun says: At very low frequencies (below 0.1 GHz) and therefore at very long wavelengths (> 3m) the solar disk appears much bigger and brighter in the center, and its ...
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3answers
165 views

Determine spectral type of star from its properties

How can I determine spectral type of star, if I know all its another properties? For Example, Rigel A has spectral type B8Ia. Rigel has temperature 12 500 K. ...
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2answers
1k views

What color is a red dwarf star?

I read recently that a red dwarf star might actually look white. I realize there's a wide range in red dwarf surface temperature, 2,500 to 3,500 degrees K, compared to 5,778 for our Sun. Metal at ...
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1answer
78 views

How to approximate the distance at which the thin disk peaks along a given LOS from Earth for a given galactic coordinate per 1 sq deg?

The density of stars drops off exponentially from the center of the galaxy and can be approximated as follows using a cylindrical coordinate system: $$ \rho(R, z) = \rho_0 \exp \frac{-R}{h_R} \ \exp \...
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0answers
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Is the magnetic field strength of a star predictable from mass, composition, age and angular momentum alone?

This answer to Which stellar properties can we describe as “first principles” in which we can derive the rest? contains an intriguing bit: That states that composition and mass are the two key ...
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0answers
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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
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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?
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2answers
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Which stellar properties can we describe as “first principles” in which we can derive the rest?

Mass, size, temperature, luminosity, chemical composition, the initial abundance of the molecular cloud, distance, brightness, age, and evolutionary cycle can all be used to characterize a star. A ...
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1answer
71 views

Calculate object apparent diameter by distance and radius [duplicate]

I'm trying to create a dynamic starfield for game using the HYG database. Because there are no data about the apparent size of the stars from earth, I will need to get it myself. I found a formula ...
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1answer
88 views

Are there ways to determine a star's spectral type without the spectrum itself?

Because of the lack of available data online, I am trying to find other ways to determine an exoplanet's host star's spectral type.
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1answer
57 views

What can a star's spectrum tell us? [closed]

Stellar spectra contain both emission and absorption lines. What can these lines from a star's spectrum tell us?
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1answer
40 views

Difference in stellar abundance numbers

What is the correlation between stellar abundance by mass and by number? Let’s take the Sun and Helium for example. This paper mentions an abundance by mass for helium as Y=0.275 and by number as A=10....

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