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Questions tagged [star]

Questions regarding large spheres of plasma undergoing fusion.

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0answers
33 views

The colour of blue dwarf stars

The paper "M dwarfs: planet formation and long term evolution" describes blue dwarf stars, a hypothetical next-stage in the lifespan of red dwarf stars within a certain mass range, after which they ...
2
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1answer
23 views

Lifespan of B-type subdwarfs

According to the Extrasolar Planets Encyclopedia, the B-subdwarf Kepler-70 lost its helium envelope and became a blue-white subdwarf roughly 18.4 million years ago. (sources: archived encyclopedia ...
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Is the turn-off point of the main sequence the same as the terminal-age main sequence?

The turn-off (TO) point is one tipping point on the Hertzsprung-Russell diagram (HRD) where low-mass stars start to evolve from the main sequence (MS) toward lower temperatures. If I understand it ...
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Freefall timescale for a Jeans-unstable hydrogen cloud of mass M

I'm working on a project (personal, not academic) that involves calculating the collapse timescales for protostars which will end up becoming stars of varying given masses. I'm treating the pre-main ...
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5answers
2k views

What are the minimum element requirements for a star?

What elements would be essential for a star to exist? From what I understand our sun is made of mostly hydrogen and helium and most stars have small amounts of heavier elements like carbon, nitrogen,...
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2answers
228 views

If a star were travelling at 99% of the speed of light, directly at Earth would we see it?

Stars being flung from black holes in the news made me question if something were heading directly for us at the speed of light, would we even know? Update: Since it's impossible for a star to travel ...
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1answer
62 views

Could S5-HVS1 conceivably still hold on to any planets?

If the star (S5-HVS1) has been accelerated to 1,700 km/s by a close encounter with the super massive black hole at the centre of our galaxy (Sagittarius A*) what would happen to any planets orbiting ...
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1answer
24 views

How can I check if we can observe a certain star (given its equatorial coordinates) from a certain location on Earth (given its DMS coordinates)?

I am given the equatorial coordinates of a star (e.g. Sirius has RA: 6h45m8.9s and Dec = -16°42'52.1"). Now my question is: can we observe this star from a specific location on Earth (e.g. from ...
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2answers
47 views

Corresponding BV Value to a Hertzsprung–Russell

I have an example BV value from an astronomical catalog of 1.04 (33 Psc, HD Catalog 28). Given only the number 1.04, can that be charted on the HR, or do I need the individual components of the value ...
2
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1answer
48 views

How much does the stellar radius change if seen through different filters?

I know that the radius of a star should be different depending on the filter being used to do the observation. That is, the bluer the filter, the smaller the measured stellar radius. I know this ...
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164 views

Could a star closely orbit a black hole long enough for the star to have lost 0.5B+ years to time dilation?

I was wondering how stable a close star-black hole system could plausibly be, and thus how much time a star could plausibly miss out on (from an outside observer's perspective) due to being in an ...
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2answers
123 views

Can a dying, swelling, star be rejuvinated by enveloping orbiting gas giants?

Many hot jupiter type exoplanets have been found, orbiting near their parent stars. At the end of a stars life, they swell up and sometimes envelop closely orbiting bodies. Combine these effects and ...
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1answer
125 views

Proxima as Supernova [closed]

Follow this question. Let's say Proxima Centauri explodes as a Supernova (I know, it CANNOT explode as supernova, let's say it can. I know, it should had exploded more than 4 years ago, let's assume ...
2
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2answers
122 views

Will it be dangerous when close stars become Red Giants?

What will happen if close stars like Sirius A or Procyon_A become red giants? Is it dangerous for the Earth and life on it? If for Sirius A we still have 500-800 million years, but Procyon A might ...
5
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1answer
33 views

Are warm circumstellar debris disks still able to be detected at sub-millimeter wavelengths?

At these wavelengths a survey is more sensitive to detecting relatively cool disks (T<100k), but would a telescope operating in the sub-millimeter be less sensitive to warm debris disk than say, a ...
2
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2answers
41 views

What does the opacity of a molecular transition mean?

In particular, what does it mean when a line (e.g, emission line in stellar wind) is optically thick or thin. I know what an optically think/thick medium is, but how does this concept compare to ...
2
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0answers
50 views

Spectral Class Breakdown

Where can I get a more detailed breakdown of Spectral Classes. Wikipedia only has it at Letter level rather than sublevel. For example, https://en.wikipedia.org/wiki/Stellar_classification has B ...
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1answer
75 views

Estimating a star's radius, temperature, and luminosity based on its mass

(See updated figure and description below.) I've been trying to generate ballpark estimates for the radius, temperature and luminosity of stars in the main sequence based solely on their masses (...
5
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1answer
114 views

Why is a giant planet around a tiny star unusual when binary stars are normal?

Inspired by this BBC article and the corresponding journal article about the M dwarf star GJ 3512. The Jupiter-like world is unusually large compared with its host star, contradicting a widely held ...
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79 views

Can someone calculate the age of the KOI-4878 star?

The star’s low metallicity and fairly high space velocity suggest that KOI-4878 is older than the Sun. But I don't know how to calculate an estimation for the age. KOI-4878 data on Simbad
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36 views

Derivation of a formula for the mass of a tidal bulge and tidal torque

I've been looking into the tidal mechanism for a binary star system and seem to have hit a brick wall. In the literature (see below), little explanation is given to justify the equations (9.60), (9.61)...
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1answer
55 views

How does the number in stellar classification indicate properties within the range of that class?

I am doing some research for a video game and I wanted to store stellar data on a star, such as its Stellar Classification, and then from that derive a physical appearance in the game. These are ...
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129 views

What do the fusing 'onion layers' of a pre-supernova star look like to scale?

I'm sure we've all seen the diagrams of various layers of element fusion from hydrogen to silicon in a star that's just about to go supernova. (Picture from courses.lumenlearning.com) I suspect ...
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1answer
57 views

About Radius and Surface Area

I am researching about the radius of a star and a its surface area. One question I have is about the effect of changing radii in stars. If for example we have one star with radius $r$ and another one ...
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5answers
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Is there a star over my head?

Say I'm standing up straight, and I draw a straight line from my core through the top of my head (perpendicular to the ground). What is the probability that that line intersects with a star? EDIT: I'...
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79 views

What is the physical reason of the mirror principle in the stellar evolution?

I understand that stars transition into the red giant phase by obeying the mirror principle, as written here: Shell-burning stars obey something called the mirror principle, which is an observation ...
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1answer
138 views

What is this object in this photo? [closed]

i took it and i don't know what planet or star is this and also there's our moon
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33 views

Grammar of stellar classification

How to write G2V correctly (I mean space)? I saw in articles $ G\,2\,V$ and $G2\,V$, on the internet webside it is usually $ G2V$.
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23 views

Period of pulsation of a star and its relation to free fall and acoustic waves

In this paper, the period $\Pi$ of pulsation for a star can be obtained by means of the virial theorem: $$\Pi = 2\pi\sqrt{\frac{sR^3}{(3\gamma - 4)qGM}}$$ where $s$ and $q$ are constants relating to ...
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2answers
3k views

Can a system of three stars exist?

Just like binary stars can a system of three stars mutually equidistant from each other? What I mean is three stars at the vertices of a equilateral If yes than what will be the orbit of a planet out ...
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0answers
59 views

Are these stars in MASCOT image of Ryugu?

Are these stars in this MASCOT image of Ryugu? Larger image: https://www.sciencealert.com/images/2019-08/processed/RocksOfRyuguStranglyFamiliar_1024.jpg They seem too bright to be stars (if the ...
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1answer
84 views

Brightest most colorful star in eastern morning sky not near any constellations; rises about 4 or 5 am?

I have been believing this is Saturn, but perhaps Antares instead? It is so colorful it shines blue, red, green and white. It is largest in sky in the East before dawn rises about 4 or 5 AM, seen ...
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34 views

Is it a star or something else [duplicate]

I was lying down with my face up looking at the stars. Then I saw this star moving: it was moving at one direction (just like airplane) it's light was not blinking, just exactly as other stars both ...
6
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1answer
99 views

Is it possible to determine an observer's position on Earth from a photo of the night sky and the time of the shot?

To my knowledge, this question can be related to celestial navigation on one hand and to attitude (or orientation) determination from stars direction on the other hand. However the combination of this ...
2
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1answer
50 views

In System KIC 9246715, How Far Does One Star Orbit the Other?

I was going to ask if it's physically possible for one red giant to orbit another, but fortunately, I have just found such a thing--a red giant binary system known only as KIC 9246715. In this ...
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1answer
40 views

Maxwell stress contribution to $\nabla \cdot \mathbf{P}$ in the Navier-Stokes equation for fluid in stars

I was reading through the following extract outlining how the Maxwell stress contributes to the $\nabla \cdot \mathbf{P}$ term of the Navier-Stokes equation for fluids in a star. Here $\mathbf{P}$ is ...
3
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1answer
142 views

Why is our Sun hotter than UY Scuti?

As Wikipedia says the surface temperature of UY Scuti is 3,365 K and the sun is 5,778 K Why is the Sun hotter than a supergiant star like UY Scuti?
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38 views

Apparent Magnitude / Apparent Brightness relationship help

I'm a high-school student that is currently working on a project that describes, using mathematical notation and explanation, how scientists can find the values of each of the properties of stars, ...
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1answer
124 views

Could anything consume a small black hole?

Whenever I read about black holes, it is normally involving how they devour anything that comes too close... regardless of how big anything is. But what if it were a really small black hole vs ...
2
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1answer
28 views

How to interpret error of absolute magnitude of a star given data from wikipedia?

This Wikipedia page contains information about the star Spica in the rightmost table. A small snapshot of this table is below. In this table, the absolute magnitude is given as ...
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2answers
99 views

Black hole's gravity

Is gravity relative to volume, or size of an object? Since a black hole is a massive star that collapses on its weight, how comes the same sun's mass, when it becomes a black hole, provides gravity ...
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0answers
31 views

What Would Be the Maximum and Minimum Luminosities of a G-Type Main-Sequence Star?

So I just found the Habitable Zones in Multiple Star Systems interactive website, where I can create a habitable zone out of multiple stars using the temperature, luminosity, mass and position of each ...
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2answers
61 views

How to create unique 3d star maps?

I have been trying to create a calculator which finds the distance between two stars that the user chooses. But I'm having a hard time visualizing where these stars are in real space. Do you know of ...
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1answer
42 views

Turn celestial coordinates into light years

I have a question about celestial coordinates. I have been working on a calculator that takes in different stars and tells you how far apart they are, and their coordinates (x, y, z). But I didn't ...
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2answers
208 views

Is there a way to factor age into the mass-luminosity relationship for stars?

I'm wondering if there's a way to formulate the luminosity of a star not only as a function of mass, but of age, too, and if so, what the formula for luminosity would look like. In the case of the Sun ...
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0answers
103 views

Why do astronomers use the equatorial coordinate system that moves, instead of one based on fixed, distant stars?

As an outsider to the field, I am surprised to learn that astronomers commonly use the equatorial coordinate system, in which fixed stars are not actually fixed. Isn't that making life harder than it ...
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2answers
338 views

What would happen if a Sun-like star were to consume a Jupiter-like planet?

A substantial number of discovered exoplanet systems are likely contain more than one gas giant with distances far closer to the star than in our solar system. It is known that in solar system ...
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2answers
3k views

Which star / galaxy is moving away from us the fastest?

I know that we have measured the rate a lot of stars and galaxies move away from us using the doppler shift, and I know that the further a star / galaxy is the faster they accelerate away from us due ...
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0answers
75 views

Stars that don't fit $L=4\pi R^{2}\sigma T^{4}$?

When calculating luminosity/radius/temperature for several stars, I've noticed that while the majority of stars conform to the luminosity relationship $L=4\pi R^{2}\sigma T^{4}$, there are a few that ...
2
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1answer
79 views

What does cz mean?

Take DS Geminorum for example, it has a cz of -2.33 [2.96] My question is what does cz mean, what does is represent? and what does the value in the brackets mean? http://simbad.u-strasbg.fr/simbad/...