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Questions tagged [star]

Questions regarding large spheres of plasma undergoing fusion.

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2answers
185 views

When does a star rise with the sun?

Problem: Suppose an observer's latitude is 45 S and a star's RA/DEC is 3h15min/41S. On what date will the sun set with the star. I have been stuck on this problem for a while. I found out that the ...
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“Juxtapositions” of moon,stars and planets in the sky,

What are "Juxtapositions" of the Moon, stars and planets called? When the Moon, stars and planets take exactly the same position after few or many years, how to describe the positions and what is ...
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What limits the use of the H-R diagram to measure distance (main sequence fitting), what distances is it useful for?

Is it only possible to measure objects that form around the same time? Is it possible to measure clusters from distant galaxies other than our own?
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When exactly star Sirius shines into the queen's chamber of Great Pyramid?

I read that Great Pyramid was built to resonate with Sirius by aligning an airshaft that connected to queen's chamber. That is, the light of Sirius going through the shaft would be able to shine into ...
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Is there a histogram of how long ago the stars in our Galaxy formed?

There are several ways of determining the age of a star: its position in the HR diagram, the presence of a protoplanetary disk, it belonging to a cluster... When did the stars in our Galaxy form? Do ...
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Saw 8 stars moving in same direction one by one [duplicate]

I saw 8 stars moving in the same direction one by one and then at the same point they faded or you can say disappear. The speed was not too fast but not too slow either. I am more curious because ...
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1answer
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Several stars in line [duplicate]

I can see several stars in the sky they can make a line come from the West south and going to East north direction at the time between 6.50 to 7.00 pm Indian time on date 13.1.20. What might these ...
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What is this bright “glow” in the center of galaxies?

It was always my belief that at the center of many galaxies, there are supermassive black holes. If this is the case, then we should not see a "light" coming out from the center since light get's ...
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Stars moving in a row [duplicate]

Today I saw with my wife and neighbours stars are moving in a row almost 10 to 12, and after a few minutes 2-3 stars moving in different direction in a row. What could they have been?
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1answer
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Does the orbits of stars in a binary system have a common focus, which is the center of mass of the stars?

I know that when a planet orbits a star (and assume the star is stationary because its mass is >> the mass of the planet), the orbit is an ellipse, and the star sits at one of the foci of the ellipse. ...
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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 ...
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I also see the line of 30 stars @today(11/jan/2020)on5:35am [duplicate]

I can't take any pic because I don't know how many light are coming.
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more than 30 moving stars [duplicate]

I am Abdul Kadhir from Kochi, Kerala, India. I, my wife and my daughter have seen today (2020-01-11) morning 5.45 AM IST a line of stars. A pair of more than 30 stars moving in a line from south to ...
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Without using absolute magnitudes or isochrones, how might we tell a star's age and evolutionary status?

Usual methods of estimating stellar ages involve isochrone approximations. It can also help to estimate a star's radius by correlating its absolute magnitude with effective temperature and apparent ...
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What are these 2 colorful, flashing objects in my sky? [closed]

Today and yesterday (Jan 6th and 7th 2020) we've noticed two objects, about 1 thumb above the horizon and 3 thumbs apart, in the E/SE. We are in central Europe. They are both very bright and visible ...
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stars moving in the sky or something [duplicate]

I was out in the garden having a cigarette and was watching the shy looking at three stars for about 5 minutes. suddenly they moved in the sky and crossed paths.one has now stopped still and would ...
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Astronomical events and Celebrations

In the past people celebrated important astronomical events and some of those events are still celebrated in some cultures and traditions. For example: March/September equinox, New Moon, Winter/...
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A line of lights in sky [duplicate]

I just seen this in sky a line of stars probably satellites just wondering what they where and what they doing it was amazing never seen any like it
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1answer
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Correlation between stellar mass and galactocentric distance

As we move away from the centre of, say, a spiral galaxy, is there a relation between the stellar mass and distance? I know the how the stellar abundance and density varies with the distance but does ...
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1answer
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Data for spectrum of Wolf-Rayet stars

I'm looking for a way to access the data used to produce these plots for instance. These plots show the spectrum of various Wolf-Rayet stars. I found a few websites where you have some informations on ...
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1answer
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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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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} ...
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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 ...
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1answer
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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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1answer
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Is there a database of all known star names/identifiers?

I am looking for a list of all known identifiers used for stars. I'm not sure on the terminology. While I do want the "proper names", I also want whatever identifier is used for each star detected, ...
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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 ...
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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 ...
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2answers
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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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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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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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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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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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Could the earth become a star if more mass was added?

I've heard that the only difference between a star and a planet is mass, meaning that if planets accredited enough mass they would too become stars. Does this mean that the star started off as a ...
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1answer
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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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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 ...
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1answer
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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 (...
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1answer
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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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2answers
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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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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 ...
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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 ...
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1answer
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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 ...
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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 ...
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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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How loud would the Sun be?

Sound can't travel through outer space. But if it could, how loud would the Sun be? Would the sound be dangerous to life on Earth, or would we barely hear it from this distance?
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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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How much mass will the Sun have when it becomes a white dwarf?

In 4 billion years, when our Sun sheds all of its outer gas layers and turns into a white dwarf, how much mass will the white dwarf have compared to what the sun has today? Will the planets still ...
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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 ...
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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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1answer
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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 ...