The star tag has no wiki summary.
19
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6answers
2k views
Could there be a star orbiting around a planet?
I wonder if there ever could be a star (really small) which may orbit around a planet (really big)?
13
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1answer
3k views
Is Jupiter a failed star?
In my physics lessons, my teachers have always been keen to tell my class that Jupiter is considered a 'failed star' by scientists. Is this true?
In my own effort I wondered if maybe this could just ...
13
votes
3answers
133 views
What is the probability that a star of a given spectral type will have planets?
There is a lot of new data from the various extrasolar planet projects including NASA's Kepler mission on extra-solar planets. Based on our current data what is the probability that a star of each of ...
13
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3answers
111 views
How are newly discovered objects (stars, planets, galaxies…) named?
When a new astronomical object (star, planet, galaxy, comet, etc.) is discovered, what is the official procedure to name it? Who decides about the name of it? Can they be changed in time?
Extra ...
12
votes
1answer
2k views
How many stars are in the Milky Way galaxy, and how can we determine this?
I have heard multiple estimates on the quantity of stars within our galaxy, anything from 100 to 400 billion of them. The estimates seem to be increasing for the time being. What are the main methods ...
12
votes
1answer
88 views
Why don't stars in globular clusters all orbit in the same plane?
Globular clusters like Omega Centauri certainly don't seem to be very coplanar at all.
In other words, why doesn't the explanation at Why are our planets in the solar system all on the same ...
10
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4answers
10k views
Can the “Milky Way” galaxy be seen by the naked eye in a clear sky?
Is this photo "real"? Are the stars not super-imposed in the image?
10
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2answers
378 views
Is it possible to see satellites with the naked eye?
Every now and then I notice some very bright "stars" in the sky. They tend to be very few (one or two, usually), and are quite much brighter than any other star out there. Often they're perfectly ...
10
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3answers
1k views
Calculations of apparent magnitude
I was attempting to do some calculations of apparent magnitude to help solidify my understanding of the topic, but have been running into some confusion.
According to Wikipedia, the apparent ...
9
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2answers
307 views
How can a Population III star be so massive?
How can a Population III star have a mass of several hundred solar masses? Normally the limit is about 100 solar masses.
9
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1answer
28 views
“Blue Bumper” Stars
I was recently overviewing various massive compact halo object studies (the Anglo-Australian MACHO collaboration and the French I/II EROS collaboration), and they frequently reference "blue bumper ...
8
votes
3answers
182 views
Significance of letters in Hertzsprung-Russell (H-R) diagram
The Hertzsprung-Russell diagram that categorizes star types uses the letter codes O, B, A, F, G, K, and M to indicate a star's temperature/color. Hottest (blue) is O and coolest (red) is M.
What do ...
7
votes
3answers
81 views
How would two equally massed stars orbit?
In an empty universe, except for two equally massed stars, how would they orbit? Or, for another example, if the earth suddenly grew to be the mass of the sun, how would they orbit, or interact? Would ...
7
votes
3answers
481 views
Why doesn't helium start to fuse while there is still hydrogen fuel?
In all the descriptions of the stellar life cycle it seems as though helium doesn't start being fused until all (most?) of the hydrogen is gone.
Is this true? Why is this?
It seems counter ...
7
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3answers
43 views
Is a rogue 'exoplanet' classed as a exoplanet?
Given that the term planet strictly (according to the IAU) refers to a body around the sun, rogue planets can't be called that, so I assume they must be called rogue exoplanets?
But do they even ...
6
votes
3answers
221 views
Binary stars' apparent magnitude
If you plot the apparent magnitude of a binary system (so you are unable to see 2 distinct stars) against time, it gives a repeating 'M' effect.
(from http://accessscience.com/)
Assuming one star ...
6
votes
3answers
771 views
Solar system, visible stars and deep sky objects
Since I've seen that galaxies are often called "deep sky objects", as opposed to individual stars, does this mean that all visible stars in the night sky actually only belong to The Milky Way Galaxy?
...
6
votes
1answer
437 views
How do we know the masses of single stars?
I have recently read that we can only know the masses of stars in binary systems, because we use Kepler's third law to indirectly measure the mass. However, it is not hard to find measurements for the ...
5
votes
3answers
943 views
How to measure the diameter of a star?
I am thinking about something I read somewhere (if only I could find it again) in a textbook. It is about the size of a star and its ER peaks. It has to do with the waves coming off the edge (maybe) ...
5
votes
2answers
819 views
Turning Jupiter into a star
So, I've heard from various works of science fiction about the prospect of turning Jupiter into a star. From what I know about the physics of such a task, it would require somehow condensing Jupiter ...
5
votes
2answers
63 views
How do interstellar hydrogen atoms form stars?
I would like to learn the basics about how interstellar matter contracts into stars under the influence of gravity.
Some of my questions:
Let's assume an ideal and infinite large cloud of equally ...
5
votes
1answer
504 views
Most accurate ways to find the average distance between stars in Milky way galaxy
I've already posted here on quora. But, I'm not totally sure if it's the most reasonable method.
Would anyone care to elaborate on how to find the average distance between stars in a given galaxy ...
5
votes
1answer
125 views
How did enough material from other dying stars accumulate to start our sun and planets?
How far apart do scientists estimate was/were the dying star(s) that supplied the elements that comprise our sun, planet, and us? With stars so far apart and expansion of space (as I understand it) ...
4
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2answers
95 views
Where does a star's angular momentum go as its spin slows down?
So we know that stars slow down as they age. But total angular momentum must be conserved. Where does that angular momentum go?
The dissipation of Earth's tides somehow transfers Earth's angular ...
4
votes
4answers
264 views
Creating a Star Map
I have a set of data on all the stars (well, to a magnitude of 9 or so) with the values of the following properties:
magnitude,
right ascension and,
declination.
Now I'd like to create a planar ...
4
votes
2answers
81 views
Metal Dilemma: Only very few civilizations per galaxy
This is a question in the area of extraterrestrial life. While life may be possible without it, space travel is probably impossible without metal. Metal is created in stars and heavy metals (above ...
4
votes
4answers
260 views
Are galactic stars spiraling inwards?
Are the stars in our galaxy spiraling inwards towards the center, or are they in a permanent orbit?
And if we are heading towards the center then what is the rate of this process?
I started ...
4
votes
2answers
68 views
How can Y-dwarf stars have such a low temperature?
A recent article from NASA said they found some stars with temperatures "as cool as the human body." How is this possible? Does fusion still occur in these stars?
4
votes
2answers
423 views
How could scientists know how far a star or galaxy is from us?
How do astronomers measure how far a star (or galaxy) is away from the earth? How would they know that it has taken 13 million years for light to travel in space before it reaches us?
4
votes
1answer
846 views
What's the difference between a red giant and a red supergiant?
I've seen both theoretical and observational definitions of stars. For example, an AGB star is a star where two sets of nuclear reactions (helium to carbon and hydrogen to helium) are taking place in ...
4
votes
2answers
509 views
How do you measure distance to stars within the galaxy?
I know that for close by stars (<50 LY) we can use the parallax effect. And for distant galaxies we use red-shift (& hubble's constant). So how do we measure how far is a star lets say 50,000 ...
4
votes
1answer
159 views
Why Is a star a Pure state?
I am reading some papers about black hole complementarity (Samir D. Mathur. The information paradox: conflicts and resolutions. Proceedings for Lepton-Photon 2011 (expanded). arXiv:1201.2079 [hep-th].) ...
4
votes
5answers
451 views
What happens to angular momentum when matter is converted to energy?
Let's say a spinning star radiates mass-energy only from it's pole regions. How does the loss of mass-energy effect the angular momentum of the star?
4
votes
2answers
81 views
What reason(s) exist to suppose that all degeneracy pressures can be overcome in Black-Hole formation?
In models of stellar collapse to a black hole, it is a given that density increases without bound towards a singularity. Electron degeneracy I get. Neutron degeneracy I get. I assume there's some ...
4
votes
1answer
35 views
Predicting stellar evolution and life cycle of a star
Is there a way to model/predict the evolution and life cycle of a star based on certain initial conditions? That is, whether it will become a red giant, brown dwarf, etc. I'm basically looking for ...
3
votes
1answer
141 views
How does a star ignite?
I remember reading that X-Rays are generated by 'braking' electrons in a Coolidge tube.
Is it fundamentally a matter that the extreme gravity immediately before a star ignites is so strong that it ...
3
votes
2answers
26 views
Are our telescopes capable of taking actual images of brown dwarfs?
http://www.sciencedaily.com/releases/2011/08/110824102135.htm
And could we achieve a high enough resolution to actually be able to study the dynamics of brown dwarf atmospheres in the near-future?
...
3
votes
1answer
51 views
How are new nebulae being created?
The nebulae we see in the night sky are forming new stars.
The stars are eating up the nebulae and there is no obvious process in which those nebulae are being created to compensate for that.
...
3
votes
2answers
41 views
Color Variation in RR Lyrae
I've been doing some research on RR Lyrae stars and haven't been really able to find an answer to this question.
RR Lyrae are well known for their periodic magnitude, and also are usually found in ...
3
votes
1answer
145 views
Why can't a stable star have radius 1 < r < 9/8 its Schwarzschild radius?
From http://www.spacetimetravel.org/ssm/ssm.html :
A mass of 1.78 [in geometric units] corresponds to a ratio of radius to Schwarzschild radius of 9/8. Theory predicts that a smaller ratio is not ...
3
votes
1answer
160 views
Is Dyson Sphere a stable construction?
Suppose that a star is encompassed by a Dyson Sphere. Do we need a position control system for the Dyson Sphere to keep its origin always aligned with the center of the star? Will it stay aligned ...
3
votes
1answer
367 views
About binary stars and calculating velocity, period and radius of their orbit
I saw somewhere about being able to measure the velocity, period and radius of a binary star orbit by looking at red shift and blue shift.
I understand it but can someone give me an example of ...
3
votes
1answer
38 views
How do you transform between theoretical Hertzsprung-Russell Diagrams and Colour-Magnitude Diagrams?
When discussing stars, theorists tend to use effective temperature $T_\text{eff}$ and luminosity $L$ (on logarithmic scales). Observers, on the other hand, usually talk about observed colours and ...
3
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2answers
78 views
Balmer lines and their positions
I have two stars, both of which have Balmer lines at the same wavelength positions.
Why does this pattern exist?
3
votes
1answer
51 views
How accurate are our calculations about distant stars keeping in mind their enormous distances?
Since many stars are hundreds of light years away from the earth and therefore, what we observe of them today is really their distant past, how can we say anything with certainty about their ...
3
votes
1answer
129 views
Earth-Moon orbiting each other after being engulfed by Red Giant
Recently some exoplanets were discovered which are thought to be the leftover cores of giant planets that had survived a star becoming a Red Giant and then shrinking back to a subdwarf.
If giant ...
3
votes
2answers
44 views
Computing period, semi-major axis of binary
I have mass, $g$, and luminosity of each of the stars in a binary system, extracted from a model. I calculated the individual radii from $g$ and the mass. I am trying to compute $a$, but I seem to be ...
3
votes
1answer
415 views
How to draw a star chart?
How does one draw a star chart like this?
I have:
a star database with coordinates (right ascension - RA, declination - DEC),
observer coordinates (latitude, longitude) and
time of observation.
I ...
3
votes
1answer
118 views
What are some ways that humans could have influence over what sequence a star was in?
How would a society go about either preventing our sun in its primary sequence from going into a Red Giant a billion years from now? Or perhaps, accelerating the process of going from main sequence ...
2
votes
2answers
755 views
How much of sky can be seen on a typical night from a mid-latitude location?
I'm at about 40deg north so, assuming a clear southern horizon, I can't see things below about -30 or so (I actually don't know how far south). I also have a large portion that is circumpolar so it's ...
