Questions tagged [star]
Questions regarding large spheres of plasma undergoing fusion.
720
questions
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2answers
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Population density of stars within $13$ light-years of us
This item from Fox News refers to "over 600 stars that came within 13 light-years of the sun". Because of the past-tense "came", they could have meant stars that are not now within 13 light-years of ...
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Redshift and Velocity relation
Let us say that we have a stellar object so its total velocity is defined as
\begin{equation} v_{tot} = v_{pec} + V_{rec} \end{equation}
Where
\begin{equation} V_{rec} = H_0r \end{equation}
...
2
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0answers
72 views
Can “rock stars” form from interstellar dust?
Imagine a large and massive dust cloud made of solid phase micrometeoroids, asteroids and larger planetoids, all material in it is in solid phase, and contains no hydrogen or other volatiles in gas ...
4
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0answers
330 views
Why the space is so dark even there are billions of stars and many quasars emitting light [duplicate]
In our galaxy itself, there are millions of stars, and there are many more other galaxies in our local group and billions in the observable universes.
For sure they all emit a lot of light, still why ...
6
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1answer
76 views
Why does the convective core in an intermediate to high mass star shrink?
The image below shows the evolution of the hydrogen mass fraction profile for a 5 solar mass star in the main sequence. I would expect that the size of the convective core stays roughly constant as ...
7
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0answers
96 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 ...
3
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2answers
81 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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1answer
57 views
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 ...
2
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0answers
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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
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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,...
7
votes
2answers
258 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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vote
1answer
63 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
26 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 ...
1
vote
2answers
49 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
votes
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 ...
8
votes
2answers
173 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 ...
2
votes
2answers
134 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 ...
0
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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
votes
2answers
124 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
votes
1answer
34 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
votes
2answers
42 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
76 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
votes
1answer
122 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 ...
3
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0answers
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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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0answers
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)...
4
votes
1answer
56 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 ...
7
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0answers
134 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 ...
0
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1answer
58 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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votes
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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0answers
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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
142 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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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 ...
12
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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
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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 ...
1
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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 ...
2
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0answers
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
votes
1answer
101 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
52 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
votes
1answer
148 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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0answers
40 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, ...
1
vote
1answer
128 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
votes
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 ...
0
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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 ...
0
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0answers
32 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 ...
0
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2answers
62 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 ...
0
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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 ...
6
votes
2answers
212 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 ...
