The star tag has no wiki summary.
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What's an equation for two astronomical entities both of 4000 tonnes in weight, colliding? [duplicate]
I have next to no knowledge of any physics, but would be happy if you could answer my question...
I want to know an equation for two astronomical entities such as the star Sirius (2.02 solar mass) ...
4
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1answer
37 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 ...
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2answers
65 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 ...
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1answer
143 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 ...
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1answer
62 views
What would be the effect of an excess of up quarks on stellar formation?
Suppose you had 80% up quarks, and only 20% down quarks. How would this affect stellar formation?
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1answer
38 views
Conversion of a star
I need to know what would happen to a star that has size 2 times the solar mass. I guess it would either be a neutron or red giant. Is that right?
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1answer
40 views
Initial separation of neutron star/black hole binaries?
How would I go about finding the distribution of initial separations (i.e. the lengths between the centres of mass) of stars that make up binary systems. I am interested in neutron stars and stellar ...
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1answer
160 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].) ...
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2answers
219 views
EM waves: How do they travel for billions of km without damping
If a star is 1 billion light years away, it means that the light we see from the star is emmitted billions of years ago.
How does this light not undergo a frequency change or get damped inspite of ...
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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 ...
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2answers
153 views
Dark Matter 'Stars'
I'm aware that the Milky Way has a dark matter 'halo' around it, presumably a spherically symmetric distribution.
But I'm completely ignorant regarding the theories explaining dark matter... Is there ...
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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)?
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28 views
How do stars look like from space? [duplicate]
Possible Duplicate:
Optical explanation of images of stars?
What are these rays that appear in photograph of sun?
I thought stars should look round shaped (similar to a sphere, or oblate ...
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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 ...
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0answers
24 views
Surface UV exposure with cooler star
If the sun's surface was ~ 4000K (and earth closer to compensate), the UV component of the radiation would be less. However, UV makes ozone via photolysis of oxygen. Also, the stratosphere would ...
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1answer
105 views
Do stars appear to move with uniform motion?
The Ancient Greek astronomers had quite an obsession over uniform circular motion; I was wondering if there was a logical reason for this. Did it develop through actual observations of the stars? Do ...
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1answer
131 views
When calculating the local apparent sidereal time, which time scale should I use?
UT1, UTC, TAI, TDB, or what?
I need to determine the time difference between a given observation and the epoch from which certain constants apply. I typically work with the J2000.0 epoch. This is to ...
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4answers
261 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 ...
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1answer
131 views
How to calculate gravity inside the star?
Gravity must decrease due to less effective mass when going inside the object but also must increase with depth inside the star due to its higher density. Is there a model or formula approximating ...
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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
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1answer
130 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 ...
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3answers
181 views
the sounds of an exploding star
We know that space cannot spread a sound wave as there is no "air" or a medium that would support the spread of a sound wave. However if we put ourselves in the vicinity of an exploding star, would it ...
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2answers
105 views
Elements of a Planet reveals nearby supernova remnant?
During a random reading through this site, I found this one: Origin of elements heavier than Iron (Fe)...
The answer was "The formation of many elements in earth was due to Supernova nucleosynthesis" ...
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1answer
46 views
Distinguishing Gamma-rays and stars from each other in nebulas
How do you tell the difference between a gamma-ray burst and a star just from a picture of a nebula, in which it cannot flash on and off here and there?
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2answers
835 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 ...
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3answers
78 views
When was the earliest understanding that the stars were similar to the Sun?
When did astronomers realise that the stars were similar to the Sun? I'm not asking for when this was established, but when also the hypothesis was first proposed.
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1answer
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questions about stars clusters
I recently watched the documentary miniseries "How the Universe Works" and few things can't stop bothering me. I am not an astronomer nor a physicist so those may be dummy questions.
what I get know ...
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0answers
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Could a Class A Stellar Engine Use A Brown Dwarf
Could a class A stellar engine (or maybe a class C one) be built using a brown dwarf (for argument's sake, a T-dwarf like Gliese 229B)? Would it be capable of enough thrust to move itself any ...
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2answers
428 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?
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2answers
141 views
Was Sun a part of a binary system?
I've read that many stars and other celestial bodies are found to constitute binary systems where the two bodies spin around each other. But our Sun is one of the exceptions. Could it be possible that ...
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1answer
120 views
The role of dark matter in black holes and star formation
In my understanding, there exists a critical mass for which a star needs to be in order for it to collapse into a black hole. This also applies to a certain critical density of gas in order for stars ...
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1answer
59 views
Gravity and Magnetism on Stars
I am familiar with the fact that Magnetars have a really strong magnetic field and an ordinary star such as the Sun has a very strong gravitational field. But what about the opposite? What is the ...
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0answers
367 views
Calculating semi-major axis of binary stars from velocity, position and mass
I'm trying to calculate the 'instantaneous' semi-major axis of a binary system with two equal (known) mass stars for an $N$-body simulation. I know their velocities and positions at a given time, but ...
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1answer
94 views
Understanding particle's space travel
Before the discovery of dark matter, the prevailing popular understanding of Space content is that of celestial bodies (planets, stars..etc) floating in 'void' and emitting particles and waves ...
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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 ...
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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 ...
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1answer
447 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 ...
3
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1answer
416 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 ...
10
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2answers
384 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 ...
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5answers
452 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?
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1answer
49 views
Confusing description of Orions belt, could someone clarify?
The Wikipedia article about Orion's belt contains this confusing sentence:
They also mark the northern night sky when the sun is at its lowest point, and were a clear marker for ancient ...
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3answers
487 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 ...
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3answers
960 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) ...
3
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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
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1answer
39 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 ...
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2answers
772 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 ...
12
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1answer
90 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 ...
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3answers
77 views
Why is it hard to write a computer program to detect patterns which planethunters is asking us to figure out? [closed]
I recently came across this site http://www.planethunters.org. It shows brightness observed for a star vs time. It asks questions like if star is exhibiting variable or fixed pattern. Later it asks if ...
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2answers
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What physical interactions actually make single stars leave their binary companions at formation?
From an interesting ScienceDaily article, I read this
Before the groups of stars disperse, binary stars move through their
birth sites and the group studied how they interact with other stars
...
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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 ...
