The application of physical theory to celestial systems such as stars, planets, galaxies, supernovae, and black holes. Astrophysics proper is concerned with explaining phenomena more so than making observations, the latter falling under the purview of astronomy.

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What is the strongest evidence that anti-matter exists?

Every space show I watch mentions that anti-matter used to exist, or still does and we just can't detect it. I think some shows even say we can create a small amount of anti-matter. It is not ...
9
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2answers
793 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.
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1answer
2k views

Why it is said that Universe is an isolated system?

I have read in many places "Entropy of an isolated systems never decreases" And as a corollary: "As Universe is an isolated system(I) then its entropy is constantly increasing(II)" I) ...
7
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2answers
422 views

What elements can be created in the fusion process of different types of stars?

As I understand it fusion inside a sun can produce heavier and heavier elements until some sort of "nucleus size limit" is reached. As far as I understand, the limit is thought to be reached with the ...
1
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1answer
245 views

Mass of a galaxy via Luminosity [closed]

Is there a way of calculating the mass of a galaxy, or even a nebula from the luminosity? EDIT I'm deleting this, and moving the question to Astronomy Stack Exchange - thanks david
6
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1answer
29 views

Lack of exoplanet missions in the decadal survey

In recent exoplanet meeting "The Next 40 Years of Exoplanets", there was much discussion of the inablity of the community to agree on whether to support coronagraph missions or interferometer ...
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4answers
234 views

Could dark energy be the effect of gravity at great distances?

This may be a silly question, but is it possible that dark energy and gravity are related to each other? Space-time is deformed everywhere in space by objects with mass. The more massive the object, ...
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4answers
209 views

What could cause a planet to have apparently random season lengths?

The world A Song of Fire and Ice series is set on is characterized by seasons that last several years (how years are measured on this planet is not specified to my knowledge). However, they are of ...
2
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2answers
2k views

Do we know exactly how fast we are going relative to the center of the galaxy

I mean total inertial on my body siting here at my computer "California US." Ok so the earth is rotating on its axis and in turn around the sun and the sun around the galaxy. The object the question ...
2
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1answer
166 views

Will the sun cool and produce a disrupting EMP?

Scientists say rare drop in sunspot activity could cause global cooling http://www.globalpost.com/dispatch/news/business-tech/science/110615/science-news-solar-flares-sunspots-global-warming ...
9
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4answers
665 views

Can a moon have another large body as a satellite, and are there any examples of such?

In my mind, I'm comparing it to the Sun-Earth-Moon system. After all, the Earth is primarily a satellite of the Sun, but the Moon is still gravitationally bound to the Earth. Could something like this ...
16
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2answers
270 views

Recommend good book(s) about the “scientific method” as it relates to astronomy/astrophysics?

I am interested in astronomy/astrophysics, but I am not science major (I am a computer science graduate). Facts and results of the field are presented to the public without showing how these ...
7
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3answers
125 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 ...
4
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1answer
47 views

Why do astronomers say that there is not enough matter in Universe?

I was reading today about the birth of the Universe and the conjectures about the matter that was supposed to exist at the moment of the Big Bang and what can be measured now. There seems to be some ...
8
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3answers
124 views

What's dark matter and who discovered it?

I have heard about dark matter that's called the Master Of The Universe. What's this and is the dark matter the reason galaxies exist?
17
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2answers
395 views

How can a spiral galaxy exist?

A spiral arm orbiting a central mass should be dispersed quite quickly as the outer elements would move more slowly than the inner ones. The Milky Way, is about 59 Galactic Years old, which, one would ...
15
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1answer
1k views

When will the Moon reach escape velocity?

From what I know, the Moon is accelerating away from the Earth. Do we know when it will reach escape velocity? How do we calculate this?
10
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0answers
43 views

What allows the modified Urca process to work at lower density than direct Urca in neutron star cooling? [duplicate]

Possible Duplicate: What allows the modified Urca process to work at lower density than direct Urca in neutron star cooling? This comes from an unanswered question over at physics.se: The ...
13
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3answers
2k views

Why does each celestial object spin on its own axis?

AFAIK all the celestial objects have a spin motion around its axis. What is the reason for this? If it must rotate by some theory, what decides it's direction and speed of rotation? Is there any ...
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3answers
1k views

What nonlinear deformations will a fast rotating planet exhibit?

It is common knowledge among the educated that the Earth is not exactly spherical, and some of this comes from tidal forces and inhomogeneities but some of it comes from the rotation of the planet ...
3
votes
1answer
603 views

Universe Expansion as an absolute time reference

Why we call "constant" to the Hubble constant?, if the universe were really expanding then the Hubble "constant" should change, being variable, smaller and smaller..with "time". Other example/view ...
1
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1answer
607 views

Has Cosmological Natural Selection been disproved?

I've been reading Lee Smolin's Life of the Cosmos. Great book and it makes a lot of sense that the conditions in black holes are the same as conditions at the big bang. Question is, has his theory ...
1
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1answer
540 views

Neutron star material

I've read on NASA's page on neutron star that one teaspoonful of that star would weigh over 20 billion ton on Earth. If it was somehow possible to bring it to earth would it: A) Burn and disappear ...
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1answer
1k views

What is the ram-facing side of spacecraft?

what is the ram-facing side of a satellite? What does it mean and why is it called "ram"-facing? Thanks.
27
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3answers
992 views

The Pioneer anomaly finally explained?

Pioneer 10 & 11 are robotic space probes launched by the NASA in the early 1970's. After leaving our solar system, an unusual deceleration of both spacecrafts has been measured to be approximately ...
2
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1answer
133 views

Black Holes and String states

We seem to know that black hole energy, and apparently event horizon geometry and topology, are functions of Mass, Charge and Angular Momentum. Area is a function of geometry and topology as well, ...
4
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3answers
250 views

stability of hypothetical lunar atmosphere

Assume that by some means, the moon could be given an atmosphere, of the same density and pressure at the surface as the earth's. Obviously in a stable atmosphere there are temperature variations from ...
13
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1answer
682 views

Would a submarine float in the atmosphere of Jupiter?

Would a submarine float in the atmosphere of Jupiter, or would it get crushed?
2
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1answer
250 views

How does inflation drive Ω close to 1?

I'll keep it simple. How does inflation drive Ω close to 1?
3
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2answers
259 views

Is it possible to orbit the sun next to Earth?

With Geostationary orbit your limited to the equator and ~36000km. Would it be possible to orbit the sun at the same speed as Earth, and then in basically the same place so that the distance to the ...
-3
votes
1answer
131 views

Half-massive sphere in space

A sphere contains all the mass on one side while the other side is empty of matter. Both sides are separated by a strong material, you name it, that will keep the sphere together. Given that the mass ...
8
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5answers
875 views

Two orbiting planets in perpendicular planes

Inspired by this question. Can a 3 body problem, starting with two planets orbiting a larger one (so massive it may be taken to stand still) in perpendicular planes, be stable? Is there known an ...
11
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4answers
4k views

Why does Venus rotate the opposite direction as other planets?

Given: Law of Conservation of Angular Momentum. Reverse spinning with dense atmosphere (92 times > Earth & CO2 dominant sulphur based). Surface same degree of aging all over. Hypothetical large ...
6
votes
4answers
730 views

Where's earths death bulge, destroying everything in it's path?

I was watching a BBC documentary on space last night. It was talking about gravity, and it said that the reason we only ever see one side of the moon, is because the earths gravity is strong enough ...
5
votes
2answers
2k views

Origin of elements heavier than Iron (Fe)

In all the discussions about how the heavy elements in the universe are forged in the guts of stars and especially during a stars death, I usually hear that once the star begins fusing lighter atoms ...
2
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2answers
311 views

is the sun itself moving

I just thought of an interesting question.Is the sun actually moving? I have learnt that the way the lunar landers and the space ships of the Mercury and Apallo missions moved and controlled their ...
3
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1answer
427 views

Does the long axis of Earth's orbit precess? Does it nutate?

Get up off the plane of the ecliptic by a couple of million miles. Look back at the Sun and watch the Earth's orbit in time-lapse for a few centuries. The orbit is an ellipse tilted at 23.5 degrees ...
5
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1answer
1k views

Star Surface Temperature Vs. Mass

I am hoping that someone can clarify this for me. With these equations. (Boltzmann Law) and radius of Radius of star how does surface temp scale with mass $R _x \approx R_\bigodot ...
3
votes
1answer
486 views

Hydrostatic equilibrium of a star - simplification math error

I am trying to do this question and getting stuck at interpreting what the question is asking for. $$dP/dR = -g(R)\rho(R) = -[GM(<R)/R^2]\rho(R).$$ Thus when we descend a distance $\Delta R$ ...
1
vote
3answers
299 views

Effect of expansion of space on CMB

Is it true that the expansion of space time cause the CMB to become microwaves from a shorter wavelength. If it is has the amplitude been increased? Seeing as the amplitude has decreased; why hasn't ...
0
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2answers
142 views

Star trace in the sky

If the space of universe is expanding at fast rates..(even faster than light) Why we do not see the trace of the stars? A possible answer could be that the stars are only moving away but mantaining ...
1
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2answers
294 views

What happens to internal energy in high-density materials?

Normal-density materials have internal energy, which is the sum of the average energies associated to each of the degrees of freedom. Degrees of freedom can be described as vibrational, translational, ...
3
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1answer
188 views

Gamma Ray Bubble at the center of our galaxy seen by Fermi Telescope

How could we measure high energy photons, whithout measuring them ? I can't understand how we can "see" those Gamma Ray Bubbles if they are not reaching here In this graph from Nasa you can see ...
4
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1answer
138 views

What are wimpy particles?

Can anyone give a brief overview of what a wimpy particle is?
1
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3answers
244 views

Expansion of space and gravity

In my previous question I asked how gravity can be represented as dents in space. It seems that it's a metaphor. But I wondered with spac expanding does the effect of gravity get bigger as well, I ...
0
votes
3answers
364 views

How does solar activity affect the ISS?

Currently the sun is launching some intense solar flares. http://www.guardian.co.uk/science/2011/feb/17/solar-flares-northern-lights-uk Th article I've linked also mentions how a "coronal mass ...
4
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1answer
1k views

If Betelgeuse were to go supernova

If Betelgeuse were to go supernova would the sky be twice as bright, or day time extended, depending on what time of year it happened in. Basically when it does supernova how bright and large will it ...
-3
votes
1answer
481 views

History of Man Acquired knowledge of solar system [closed]

I know the basics of solar system like how earth moves around sun, and that we have so many planets, elliptical orbit of earth, and how far is sun from earth etc etc. I want to take a step back and ...
1
vote
3answers
445 views

Space as “flat” plane

I was watching the documentary Carl Sagan did about gravity (I believe it's quite old though) and wondered about space being "flat" and that mass creates dents in this plane as shown at about 3 ...
6
votes
3answers
463 views

Black holes in a head-on collision

Assume two uncharged non-rotating black holes traveling straight at each other with no outside forces acting on the system. What is thought to happen to the kinetic energy of these two masses when ...