All Questions
1,007 questions
13
votes
2
answers
3k
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 ...
- 813
9
votes
1
answer
3k
views
How can such a high exponent arise in this physics equation?
This site http://what-if.xkcd.com/14/ states that during a helium flash, "the reaction rate is proportional to the 40th power of the temperature".
Taking for granted that this is true, how can ...
- 540
17
votes
7
answers
3k
views
What is the easiest way to stop a star?
On long enough cosmological time scales, hydrogen and helium nucleii will become scarce in the Universe. It seems to me that any advanced civilisations that might exist in that epoch would have the ...
- 34.9k
6
votes
1
answer
380
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 ...
- 869
-1
votes
2
answers
2k
views
Quantum Mechanics and nuclear fusion
I've been told that, according to QM, when Hydrogen atoms are left together there is a non-zero probability that they spontaneously fuse (I accept this bit). I've been told further that, because of ...
- 1,657
0
votes
3
answers
1k
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 ...
- 1,526
2
votes
2
answers
107
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?
- 31
15
votes
3
answers
12k
views
What would be the characteristics of Jupiter if it shrank?
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 ...
- 3,759
4
votes
3
answers
338
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.
- 13.4k
7
votes
1
answer
782
views
Are "typical" black holes rotating or static?
From my (somewhat limited) understanding of GR I know that there are two different kinds of solutions that produce a black hole, some that rotate and some that do not. What I can't figure out from my ...
- 1,569
0
votes
1
answer
182
views
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 ...
- 163
2
votes
1
answer
160
views
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 ...
- 21
16
votes
2
answers
59k
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?
- 263
0
votes
2
answers
227
views
Regarding binary systems (with pulsars)
Are binary systems (in case of stars and other celestial bodies) more favorable than independent existence? I've been going through an article regarding pulsars, where it was stated that 'many pulsars ...
- 397
3
votes
1
answer
305
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 ...
- 397
3
votes
2
answers
2k
views
How were the heavy elements from iron to uranium made? [duplicate]
Possible Duplicate:
Age of the Earth and the star that preceded the Sun
How were the heavy elements from iron to uranium made?
References: http://www.phy.anl.gov/accelerator_rd/index.html
...
- 1,251
4
votes
2
answers
789
views
How many stars within 5 parsecs?
I've ran some scripts on some star catalogs, which counted the number of stars with a parallax greater than 200 mas, which should mean everything closer than 5 pc. The results are as follows:
...
- 163
4
votes
1
answer
619
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 ...
- 3,911
14
votes
1
answer
2k
views
Do any naked-eye stars have planets
Are there any known exoplanets around naked-eye stars? I know that Fomalhaut has a planet, and Vega has a dust belt that may be a protoplanetary disk or even analogous to our Kuiper belt. What else is ...
- 4,543
0
votes
1
answer
3k
views
Triangulation for astronomical distances
How can triangulation be used to calculate the approximate distance to very distant celestial bodies like stars, globular clusters, etc.? And can it be used to measure the distance to a black hole?
- 833
0
votes
1
answer
142
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 ...
- 833
3
votes
2
answers
2k
views
Why will the increase in the sun's luminosity accelerate with respect to time?
From http://en.wikipedia.org/wiki/Future_of_the_Earth#Solar_evolution
At present, nearly half the hydrogen at the core has been consumed,
with the remainder of the atoms consisting primarily of ...
- 3,662
2
votes
1
answer
2k
views
Calculating semi-major axis of binary stars from velocity, position and mass [closed]
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 ...
- 87
0
votes
1
answer
261
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 (light-...
- 103
3
votes
1
answer
181
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 ...
5
votes
2
answers
624
views
Population I and II stars
I have been thinking about the formation of the galaxy. I can easily understand that old, low-metallicity stars are in the halo, but I'm missing something when it comes to the disk.
If slowly-...
Gigi Giles
3
votes
1
answer
3k
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 ...
- 4,637
8
votes
2
answers
18k
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 ...
- 4,543
3
votes
1
answer
2k
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 ...
user1260968
11
votes
3
answers
4k
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 ...
- 3,461
7
votes
1
answer
1k
views
Stability of moons around tidally locked exoplanets
Can someone send me pointers to work (either theoretical or simulations)
showing (in)stability of satellite orbits around tidally locked exoplanets?
I want to know firstly if satellite orbits can ...
Kamal Ali
15
votes
5
answers
2k
views
Could a Dyson sphere destroy a star?
Freeman Dyson proposed that the power needs of an advanced civilisation would eventually require the entire energy output of a star to be collected, so that the star would end up surrounded by a ...
- 34.9k
4
votes
5
answers
825
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?
- 508
7
votes
4
answers
4k
views
The Sun Can Make Stuff Hotter Than Itself
How is it possible that the area around the sun is about 200 times hotter than its surface?
This question is #6 from http://www.cracked.com/article_19668_6-scientific-discoveries-that-laugh-in-face-...
- 564
14
votes
1
answer
2k
views
What proportion of a star's hydrogen is consumed in its life?
I've heard in a lecture that a star like the sun would burn 3% of its Hydrogen before expiring.
I would have thought it would be much more.
- 376
3
votes
1
answer
312
views
If a hot Jupiter was not tidally locked, then are there any specific cases where its wind speeds would be milder than those found on Jupiter?
If a hot Jupiter was not tidally locked, are there any specific cases where its wind speeds would be milder than those found on Jupiter?
After controlling for the age of the hot Jupiter, of course. ...
- 3,662
1
vote
1
answer
87
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 timekeeping....
- 4,543
7
votes
3
answers
4k
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 intuitive....
deft_code
3
votes
1
answer
163
views
Looking for a resource that explains all colors and shapes of stars and galaxies
I've been looking at some of the astronomy pictures of the day from NASA. They all have content that is indicative of certain situations or events. Supernovas have the scattered lines look, new stars ...
6
votes
3
answers
8k
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) ...
Gigi Giles
5
votes
1
answer
135
views
Is there an established standard for naming exoplanets?
I understand that exoplanets are named by adding a lowercase letter to the a designation of the planet's parent star or stellar system, beginning with 'b' (the star itself is 'a') in order of ...
- 5,169
4
votes
1
answer
368
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 ...
- 766
1
vote
2
answers
234
views
Could a viable solar system work with a cluster of dwarf stars in center? And would it last longer than a single stellar mass star?
So, I was watching various sci channel shows, and they touch on how extremely massive stars live only 100k years, vs the sun which lives ~10 billion years, and dwarf stars live some unspecified time ...
- 367
7
votes
1
answer
332
views
How are exoplanets confirmed?
In reference to the Kepler 22b news:
The Kepler team had to wait for three passes of the planet before
upping its status from "candidate" to "confirmed".
This is possible because the planet has ...
- 6,987
14
votes
2
answers
691
views
Why did population III stars lack planets?
Jay Wacker1 (professor of physics at the SLAC National Accelerator Laboratory) stated:
The first stars (known as Pop III) were made out of hydrogen and helium. They had no planets.
Why couldn't ...
- 2,350
8
votes
1
answer
231
views
What's the most accepted theory for Blue Stragglers These Days?
I'm working on a post against a recent creationism article about blue stragglers. From when I was in undergrad, the general explanation was that they were likely second generation stars within ...
- 4,447
3
votes
2
answers
418
views
Why do clusters of stars eventually dissipate?
Why don't the stars in a star cluster attract each other gravitationally, forming one big star? What causes a cluster to disperse the stars in it?
james
3
votes
1
answer
98
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 ...
- 9,785
2
votes
2
answers
8k
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 ...
forestplay
3
votes
1
answer
103
views
What could this very dark planet be made of?
I was reading about the planet TrES-2b which is less reflective than charcoal. What could possibly be its composition?
- 6,082