Tagged Questions
0
votes
2answers
49 views
Has anyone studied a statistical scaling law for the universe? [closed]
How do named objects in the universe scale? Is there a predictable curve for an ordered list, say {atom, animal, planet, solar system, galaxy, etc}? Can you then use the analysis to predict when the ...
6
votes
1answer
113 views
What is the frequency of occurrence of stellar classifications off the HR main-sequence?
An alternative version of this question would be: "if was to pick a star from the $10^{11}$ or so in our galaxy at random, what are the probabilities of it being various kinds of star?" (and I do mean ...
0
votes
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 ...
2
votes
1answer
96 views
What are we all falling towards?
One meteorite fell on the ground in Russia, last week. In different circumstances, it could have orbited the earth, or perhaps pass close to the earth and then disappear into the space.
It seems that ...
3
votes
1answer
71 views
What is the furthest object from which fermion rays were detected?
What is the furthest object from which non-electromagnetic cosmic rays were detected?
0
votes
0answers
133 views
A book for IOAA [closed]
Hello I am preparing for the International Olympiad on Astronomy and Astrophysics. However my knowledge of constellations and practical astronomy is very poor. I was looking for a book which would ...
0
votes
0answers
90 views
Theoretical early-universe cosmology [closed]
I wanted to know what are the cutting edge/recent papers to read w.r.t theoretical early universe cosmology.
I would like to know of recent review papers
I would like to know of areas which use ...
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 ...
5
votes
5answers
226 views
How is distance measured to far away stars and galaxies?
What I need is an accurate description of the methods used to determine the distance to Andromeda. The Parallax method is for nearby objects as I presume. The red shift method applies, but how do you ...
2
votes
2answers
782 views
What are good books for graduates/undergraduates in Astrophysics?
There are no book recommendations for Astrophysics here. I will write my own answer, but I am also interested in what are others' views on the question (I will NOT mark my own answer as the best one).
...
3
votes
1answer
85 views
If the observable universe keeps expanding would we eventualy see light 24/7… clouds permiting?
If we can see more observable universe could there be a time when day and night looked the same?
0
votes
2answers
66 views
A thought about Quasars
If Quasars are "beams" of energy exiting a super-massive black hole, in order for them to get through the black-hole's event horizon, they'd have to be traveling faster than the speed of light. My ...
4
votes
1answer
132 views
What day/night cycles, climate and seasons would experience Alpha Centauri Bb inhabitants?
Alpha Centauri Bb is an exoplanet orbiting Alpha Centauri B. It is asserted that given the close distance to the star the planet should be tidally locked.
The orbiting period of the planet is about ...
2
votes
1answer
333 views
Why are the orbits of the planets in our solar system along the same basic plane? [duplicate]
Possible Duplicate:
Why are our planets in the solar system all on the same disc/plane/layer?
After watching this video I realized that the orbits of the planets in our solar system ...
3
votes
1answer
93 views
What would happen in the final days of the universe?
I would like to know the stages of how the universe would end and what would happen and what the possible scenarios are.
I understand that eventually all the stars would burn out and that would ...
3
votes
1answer
70 views
Does the spectrum of Sol's emission change as it ages?
A follow-up to my earlier question How would one navigate interstellar space? that just occurred to me; albeit on a different tack.
Sol is probably in a state of continuous flux. The change of state ...
1
vote
1answer
84 views
How is retrograde motion explained in Tycho's model?
Tycho proposed a model of the solar system where all planets but Earth move around the sun while the sun and the moon move around the earth.
I wonder how this model could explain the retrograde ...
0
votes
1answer
39 views
The radius of the swept up shell of the observed planetary nebula [closed]
The emission from this shell produces the observed planetary nebula.
Assume that the fast wind switches on instantaneously at the end of the red giant phase at $t = 0$. The mass of swept up material ...
1
vote
2answers
69 views
What is the Schechter luminosity function's domain of support?
I'm trying to fit a Schechter luminosity function to some data points, but it's not clear from this definition what the domain of support of the PDF should be. I'm familiar with the standard Pareto ...
3
votes
1answer
104 views
Official definition of astronomical units
As it is relatively easy to find an official value for a large number of physical constants, (thanks to CODATA), it is not so easy for some units widely used in astronomy (Wikipedia, Google and IAU ...
0
votes
0answers
81 views
Mass loss rate of planetary nebulae
The “interacting wind” model of planetary nebulae is based on the idea that the white dwarf phase of stellar evolution is preceded by a red giant phase. A fast wind from the hot white dwarf overtakes ...
10
votes
2answers
348 views
Can $10^{23}$ stars be treated with methods of statistical mechanics?
Statistical mechanics is used to describe systems with large number of particles ~$10^{23}$.
The observable universe contains between $10^{22}$ to $10^{24}$ stars. Can we treat those many stars as a ...
6
votes
1answer
71 views
Does a celestial system exhibit a collective magnetic field?
Sol exhibits a magnetic field, most of the planets in orbit around Sol exhibit a magnetic field - strong and weak both.
Does the solar system as a whole exhibit a magnetic field?
Does the paradigm ...
1
vote
1answer
74 views
Why are galactic centers always brighter than the edges?
As you can see this image http://i.stack.imgur.com/YOt8C.jpg and other galaxy images, the centers generally much brighter.
Why is that?
Is there a very big star? A very big gravitational field?
0
votes
0answers
49 views
How is the universe expanding? [duplicate]
Possible Duplicate:
spacetime expansion and universe expansion?
Is the space between planets is growing or the space between stars is growing or the space between galaxies is growing?
0
votes
1answer
114 views
Does diffraction contribute to the Black Drop effect?
Two reasons are given to explain the black drop effect here, but I think I came up with a third.
Consider a two-dimensional cross section of the situation just after second contact and just before ...
0
votes
2answers
216 views
speed of light,breaking the barrier
when the sound barrier is broken,a series of concentric waves of sound is produced.Does it mean when the speed of light barrier is broken,a ripple of photons are created in the space-time fabric?
1
vote
1answer
256 views
Analogy between magnetic bottle and Van Allen's radiation belt
A magnetic bottle is an arrangement that permits to confine charged particles. Here you can find a review for charged particle rotating in a magnetic field and at the bottom of the page a description ...
2
votes
1answer
152 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:
...
4
votes
5answers
6k views
Gravity on the International Space Station
We created a table in my physics class which contained the strength of gravity on different planet and objects in space. At altitude 0(earth), the gravitational strength is 100%. On the moon at ...
0
votes
0answers
22 views
Expansion of Universe [duplicate]
Possible Duplicate:
Why space expansion affects matter?
If the Expansion is prevalent, i.e. it is observable and true then shouldn't that result in the expansion of the Milky Way galaxy, ...
2
votes
1answer
88 views
When would the proposed black hole at the centre of Milky Way gulp in our solar system?
I've heard and read that our solar system lies near to the peripheral region of the Galaxy. Then accordingly we would have a greater probability of sustaining to eventual gulping down by the ...
2
votes
1answer
287 views
Combined Gravitational Force Vectors in a Spherical Coordinate System
Asking a question here is quite intimidating for me -- while I love Physics, my high-school understanding only allows me to go so far... I've been trying to solve this problem for the last couple of ...
2
votes
1answer
177 views
How early can scientists detect that a deadly asteroid will hit planet earth?
With the advancements in science and technology, how early can scientists of the world detect that a certain asteroid will hit planet earth and cause damage? Are there any impact avoidance strategies ...
5
votes
1answer
60 views
What prevents stars in globular clusters from merging over time to form a black hole?
Globular clusters are apparently very very old, and the density of these clusters appears to increase as one approaches the center of a cluster. Orbits are bound to be chaotic, since there is no ...
5
votes
2answers
106 views
Io - Turned inside out
In a lot of the descriptions of the moon Io it frequently states that the moon, because of volcanic activity, has been literally "Turned inside out". What exactly is meant by "Turned inside out" and ...
6
votes
1answer
134 views
Frequency of nomad planets passing within 30 AU of the sun
A recent estimate by the Kavli Institute for
Particle Astrophysics and Cosmology (a joint
institute of Stanford and SLAC) is that there
are circa 100000 times as many 'nomad planets' as stars
I ...
8
votes
1answer
75 views
Biggest crater in the Solar System
It seems that the biggest crater in the Solar System is Borealis Basin on Mars. The Wikipedia entry and this piece of news say it has been formed by an impact with a body of around 1600 - ...
6
votes
1answer
82 views
What is the orbital path of Omega Centauri?
I was under the impression the only objects relatively close to our Milky Way but not yet a part of it were the Sagittarius Dwarf and Large and Small Magellanic Clouds and then much further out, but ...
12
votes
9answers
168 views
In astronomy what phenomena have theory predicted before observations?
As far as I know, astronomy is generally an observational science. We see something and then try to explain why it is happening. The one exception that I know of is black holes: first it was thought ...
4
votes
3answers
1k views
Use of advanced mathematics in astronomy, like topology, abstract algebra, or others
I know that topology, abstract algebra, K-theory, Riemannian geometry and others, can be used in physics. Are some of these areas used in astronomy, and are some astronomical theories based on them?
...
7
votes
1answer
54 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 ...
2
votes
0answers
135 views
Angular Diameter, Parallax - Perceived size of Objects
I'm currently in the process of writing a 2.5D Application that should display the perceived size of an Object. For example, When I have a ball that has a diameter of 1meter, how big would it appear ...
4
votes
1answer
40 views
How fast is the Cosmic Microwave Background Radiation (CMBR) changing?
I know that the Cosmic Microwave Background Radiation (CMBR) is the leftover radiation from the "surface of last scattering".
However, at every instant the surface is changing (at the rate of flow ...
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 ...
2
votes
2answers
19 views
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
...
6
votes
1answer
75 views
Axial Tilt and precession rate of exoplanets
The Earth's axis is 23.5 degrees away from othogonality to the ecliptic, and it takes about 26 000 years for it to precess fully. I have neither an intuitive sense nor the formula for precession ...
6
votes
1answer
54 views
What conditions should an asteroid or comet impact need to meet in order to start an impact winter?
Is there a way to calculate if an impact from a given asteroid (say 5 miles in diameter, solid rock to which we know the mass) would start an impact winter? If yes, I would like to see a real example ...
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?
3
votes
1answer
93 views
How do the day/night temperature variations of moons compare to those of their planets?
Does the planet's eclipse have a significant impact on the flux of light hitting the moon? Does tidal locking have any effect on the day-night difference of the planet?
