Questions tagged [star]

Questions regarding large spheres of plasma undergoing fusion.

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Why haven’t we observed supernova events of the hypothetical population III stars?

It’s said that we haven’t observed any population III stars because these stars are too far away, which makes them too dim to observe via small diameter space telescopes. Their light is also extremely ...
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3 votes
0 answers
52 views

How are plage regions related to the density of medium and velocity FeII ions?

During a literature review (abstract), I found that the intensity of FeII (298.5 nm) ions in the last solar minimum was higher than the two previous solar minima 21 & 22. The velocity of FeII ions ...
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1 vote
2 answers
92 views

Where can I find a list of galactic Long/Lat for stars?

I can only seem to find right ascension and declination, which if I understand is position when looking upwards, where as galactic long/lat should be position if you imagine a sphere of the plane of ...
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  • 21
1 vote
0 answers
34 views

Why do we estimate the Minimum mass when we are dealing with exoplanets?

While solving astronomy problems dealing with exoplanets, I always see that the question asks for minimum mass instead of the mass. Why is that so and why is the calculated mass minimum mass? example ...
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2 votes
0 answers
35 views

Where can I find galaxy rotational data?

I want to do a small project of generating rotational curves for different galaxies, and need data for some prominent stars in other galaxies (data needed: distance from center, rotational velocity) ...
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8 votes
1 answer
1k views

Rotation direction of Pulsars

Pulsars are rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds. It has a very strong magnetic fields which funnel ...
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5 votes
1 answer
427 views

When was/will Polaris's declination be maximised?

When was/will Polaris's declination be maximised? In what year was/will Polaris be closest to the north celestial pole.
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15 votes
1 answer
735 views

Has a magnetic field flip of a distant star ever been measured?

The magnetic field of the Sun flips during each solar cycle, with the flip occurring when sunspot cycle is near its maximum. Levels of solar radiation and ejection of solar material, the number and ...
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0 votes
1 answer
65 views

Convert from spectral type to RGB color?

I'm writing a night sky simulator and I want to render stars using the correct color. Is there a formula that converts a two-character code (as seen in the Yale Star Catalog) to a RGB value?
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4 votes
2 answers
96 views

What stars am I seeing in the daytime?

I currently live in the United Kingdom, in an area where the overall elevation is high so while the hills are rolling rather than peaky, they are all well above sea-level. A few weeks ago I was on a ...
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  • 143
5 votes
1 answer
124 views

How far away from us was Earendel star when it emitted the light that is just now reaching us?

From what I've read, the look back time is about 12.9 billion light years, and the current distance to the Earendel star is approximately 28 billion light years... How close to us was it when it ...
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46 votes
1 answer
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Is there a better explanation of this picture showing the very distant star "Earendel"?

"Close-up of the tiny region where Earendel happened to fall right on top of the narrow line where the magnification increases by (tens of) thousands of times. A cluster of many stars is seen ...
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1 vote
1 answer
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Could Hawking radiation turn a black hole back into a star?

Would a black hole after eons of losing mass due to Hawking radiation, eventually turn into a burning star again? As it’s pressure will no longer be overwhelmed by the gravity it once had and through ...
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10 votes
1 answer
2k views

What is this, red, blue, white twinkling, star? [duplicate]

I am from Germany and at 11 PM I was outside and I saw a star, rapidly twinkling in blue, red and white. At first, I thought it was a plane, but it didn't move. I took a picture of it, but you can ...
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1 vote
1 answer
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Using Saha's equation knowing the overall pressure

Knowing the pressure, $P_g$, how can I calculate $\frac{N_{I+1}}{N_I}$ using Saha's equation? If I assume that $P_g=(n_e+n_{H^+}+n_H)K_B T$ and that $n_e=n_{H^+}$, I can find the electronic pressure, $...
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3 votes
2 answers
313 views

Deriving the apparent angular speed of a star

The angular speed of stars in the sky is constant but the apparent angular speed is not, due to the star moving faster on the celestial equator and slower near the celestial pole. The apparent angular ...
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1 vote
1 answer
32 views

I dont know how to properly search in SIMBAD [closed]

I've been trying to search in SIMBAD for a star in about 92 parsecs, there is a problem. I dont know how to properly search, I got confused with the query search with those bazillion codes, and every ...
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1 vote
1 answer
57 views

On finding the magnitude of Stars

I am wondering how I would be able to predict the Magnitude of fictional stars, given we know enough about them. As the formulae I can find online are mostly getting overly high values that don't seem ...
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  • 111
4 votes
2 answers
252 views

Is there a way to find polar star after identifying Orion's belt?

Usually the polar star is identified based on Pointing stars in Big dipper(saucepan) shape.. Compared to big dipper, it is easier to identify Orion's belt. Would that help me to identify Polar star?
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  • 143
1 vote
1 answer
93 views

What is Canopus in this picture?

Picture is taken from 34.2N 126.6E Bogil-do, South Korea. I suppose the dot at up-right side is Rigel and the bright white dot is Sirius, and bright reddish dot at the bottom is light from some ...
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7 votes
1 answer
112 views

How is observable matter distributed in the universe?

The observable matter in the universe is distributed and arranged into various structures, including black holes, stars, nebulae, and the much more diffuse regions of the inter-stellar and inter-...
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  • 538
42 votes
3 answers
6k views

How did Hubble know the red shift difference between "moving away" and "old"?

My 9yo daughter is very into space at the moment and asked a question that my physics knowledge (6th form college, 20 years ago) is way too poor to answer. Her space book tells us that as stars age, ...
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7 votes
3 answers
2k views

How is the star 'Spica' pronounced?

Pronunciation seems to vary depending on the source, usually either SPY-kuh or SPEE-kuh. Which is correct?
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  • 1,189
0 votes
1 answer
148 views

What would the temperature be on the surface of Sirius B [closed]

If Sirius B was a planet like Earth and not a white dwarf star what would the temperature be on the surface of Sirius B at its nearest and furthest distance? 8.2 AU to 31.5 AU EDIT: I want to know if ...
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3 votes
3 answers
147 views

Why does the gas cloud collapse in regions of high density?

Stars form when gas cloud collapse under gravity, becoming hot and subsequently initiating nuclear fusion. I have read that the collapse is triggered by density fluctuations, where regions of high ...
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  • 463
2 votes
2 answers
113 views

What is the relation between Kelvin-Helmholtz timescale and free-fall timescale?

What is the actual difference between these two timescales? Both of these timescales define the time for collapse when there is only gravity. Also, what does it mean by saying Kelvin-Helmholtz ...
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  • 463
3 votes
1 answer
273 views

What determines the temperature of a white dwarf?

Can someone please explain what determines the temperature of the white dwarf? Is more massive white dwarf hotter ? Also, is the density of a white dwarf always a constant?
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  • 463
-7 votes
1 answer
103 views

What would happen if we replaced our sun with a red dwarf? [closed]

What would happen to us on Earth, not how our orbit would change.
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-2 votes
1 answer
101 views

I believe I saw a UFO, what else could it be? [closed]

When looking at the night sky some time ago I noticed a white dot. The amount of light coming from or being bounced on that object made it the same size of a average star. But differently from a star, ...
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  • 1
3 votes
0 answers
49 views

Are Superluminous supernova and Hypernova the same thing?

Are Superluminous supernova and Hypernova the same thing? Is there any difference with their formation, luminosity etc?
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6 votes
0 answers
67 views

Using tail-fit Gaussian distribution to compensate for saturated sensors

Main Question I have a project goal, where I have an image of light sources (stars or lamps doesn't matter). The image is split up into channels for each expected band of 'color'. There are occasional ...
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20 votes
2 answers
5k views

Why will HD 84406 be chosen as the first target for testing JWST?

HD 84406, is a star approximately 241 light-years away in the constellation of Ursa Major. HD 84406 will be the first star to be imaged by the James Webb Space Telescope in order to test the focus of ...
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1 vote
0 answers
51 views

Child-friendly freely available web-based tool to generate skymap

I am intending to develop a free web-based tool where kids can plot a 2D skymap based on terrestrial coordinates and local time. I am aware of the fact that multiple sites provide already accurate sky ...
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0 votes
0 answers
85 views

Heaviest star in universe

Using the estimated age of the universe, can we calculate the heaviest star in the universe using normal fusion reaction rate of our sun? Assuming the star did not die.
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14 votes
1 answer
201 views

Is stellar ignition all-or-nothing?

The boundary between brown dwarfs and stars is around 80 Jupiter masses. Only stars generate a self-sustaining hydrogen fusion, although brown dwarfs sometimes fuse lithium and deuterium. Is hydrogen ...
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1 vote
0 answers
31 views

Power law of object mass in Milky way

Red dwarfs are more common than larger stars. Does this trend continue to smaller objects? If you take every "condensed object" from dust grains through asteroids, planets, and stars in the ...
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1 vote
0 answers
86 views

Why Stars usually stop fusion at Iron, Though Nickel-62 has the highest binding energy per nucleon? [duplicate]

We know that iron is often regarded as 'nuclear ash' because of its inability to fuse with other atoms, as it has a high binding energy. However I found that Nickel-62, grabs the title of having ...
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0 votes
1 answer
112 views

Are there any naked-eye visible stars in our Milky Way that are particularly rich in calcium? (I'm just curious)

There are Calcium-rich supernovae but here I'm asking about stars that one might see in the night sky. I'd like to ask if there are any naked-eye (or binocular-assisted) visible stars in our Milky Way ...
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  • 39
2 votes
2 answers
99 views

Horizontal and equatorial coordinate systems

What is the difference between horizontal and equatorial coordinate systems apart from the notations (azimuth, altitude) and (right ascension and declination angle)? Please provide some measurements ...
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  • 91
1 vote
0 answers
34 views

Mass-age stellar phase diagram

The HR diagram is a sort-of "phase diagram" (in a very rough sense) for stars, where a particular star's location on the diagram says something about what "kind" of star it is. ...
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6 votes
2 answers
111 views

color of stars and temperature

I recently got questioned on why stars are the color they are. I know the color of a star depends on its surface temperature where hotter stars produce more light towards the blue side of the spectrum ...
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  • 61
1 vote
1 answer
74 views

Angle of Declination and Culminations

Is it true that angle subtended by the Zenith Distance at Upper and Lower culminations is equal to the declination of the star ?If It's true then why? Is the motion of Earth make the solid angle of ...
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7 votes
2 answers
116 views

Could stars like S2 near the galaxy's center have planets in a stable orbit?

I read about one of the stars orbiting Sagittarius A* and according to Wikipedia, it reaches a maximum speed of 0.03c during its orbit. Would this (or any other factor) make it impossible for a planet ...
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2 votes
1 answer
240 views

What kind of opacity should I use when I simulate stellar structure?

I am tring to simulate the evolution of a star. As we know, opacity plays an important role and has many forms like: free-free, bound-free, bound-bound, electron scatter. But I am confused about their ...
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2 votes
0 answers
66 views

Formula for calculating if an object can cast a visible shadow on the ground or not

I know that we can see the shadow cast by the light of Venus on the ground. I also talk with one person who said they were able to see the shadow even from Jupiter. Recently I've read something like ...
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  • 216
2 votes
2 answers
103 views

What would be the product between the collision of a white dwarf and a main sequence star?

Would this ever happen? If it would, what kind of star/supernova would this create? Does it depend on the mass of the main sequence star?
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1 vote
2 answers
81 views

Star and Planet temperature relationship

Let's assume there is this planet with no atmosphere, no geothermal activity and an average temperature $\ T_p$. Now, if the distance between the planet and the star is $\ d$ and the radius of the ...
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1 vote
2 answers
200 views

What if hypothetically Ton 618 could have been a star

Assuming Ton 618, the largest ultra massive black hole wasn’t the result of feasting on near by matter but was hypothetically once a single star body. How large in terms of size would TON 618 have ...
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1 vote
2 answers
70 views

I need help identifying what stars these are

I took these photos in the early morning. I’m in North America for a general location. I’m just curious on what they are as I can’t tell.I edited one so only the stars show, if that’s any help
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  • 21
1 vote
1 answer
119 views

If Betelgeuse dimmed because of dust, what became of the dust?

This question started as a clarification request of a question from Glorfindel, answered at least in part by James K, and I realized it would probably be best as a stand-alone question. The most ...
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