All Questions

4
votes
2answers
81 views

What is the relationship between the focal length and f number of a telescope compared to a guide scope?

How do you determine the optimal length of a guide scope for a given imaging telescope? I imagine it would have to take into consideration the pixel size of the guide scope, but would the aperture ...
7
votes
3answers
150 views

Why are planets spherical?

I am a complete novice when it comes to astronomy, but someone asked me the above question casually. It seems as though planets are all roughly spherical, whereas other celestial bodies aren't ...
5
votes
3answers
68 views

Heavy star and redshift

A heavy star should look redshifted, due to gravitational time dilation. How is that incorporated into the calculations of distances to the stars, or is it negligible? How about an entire region of ...
3
votes
2answers
68 views

Does gravity propagate?

Gravity is sometimes described as a curvature in space-time. Due to relativity, doesn't this imply that gravity doesn't propagate? A thought experiment. If you are moving toward a black hole, this ...
5
votes
2answers
40 views

Are nebulae only visible from a distance?

There's plenty of data about the density of nebulae, and obviously they're pretty thin. This is space, after all, and these things are really, really big. But I'm wondering about the practical ...
3
votes
1answer
79 views

Do galaxies have a preferred orientation?

This article: http://physicsworld.com/cws/article/news/2011/jul/25/was-the-universe-born-spinning asserts that the universe was "born spinning" and that there is a preferred rotation direction for ...
4
votes
2answers
205 views

How to plot orbit of binary star and calculate its orbital elements?

I have a set of dates, position angles ($\theta$) and angular separations ($\rho$) for visual binary star. For example: ...
5
votes
1answer
88 views

How can satellites be safe in the atmosphere when there are so many asteroids coming in?

How can artificial satellites be safe in the atmosphere when there are hundreds of tons of dust and asteroids coming into earth's atmosphere everyday? What is an orbit of an artificial satellite? ...
4
votes
2answers
90 views

Is the discovery of Alien or Extra Terrestrial Life a function of the science of Astronomy?

Is the discovery of Alien or Extra Terrestrial Life a function of the science of Astronomy? When i read astronomy articles on the search for new Planets or discussions on Mars a lot of the topic is on ...
0
votes
1answer
54 views

Martian Brother [closed]

According to some documentaries History and Discovery, fossils have been found in a meteorite that fell to earth. This meteorite came from Mars. It is possible that the Martians always try to be ...
4
votes
2answers
126 views

How does light affect the universe?

When light is emitted by for example a star, that star loses energy - which causes it to reduce its gravity. Then that energy begins a journey for potentially billions of years, until it reaches some ...
6
votes
1answer
96 views

How does gravity affect the wavelength of light?

If, hypothetically, me and my rocket powered flashlight were falling straight toward the center of a black hole. The flashlight is a few kilometers behind me in our travels toward the center of the ...
2
votes
1answer
79 views

Black Holes emitting Hawking radiation

I've read that even light cannot escape from black holes. The speed of light is theoretically predicted to be the escape velocity of a black hole. I've also read that the general notion that nothing ...
5
votes
2answers
91 views

How does a telescope measure parallax angle?

I know how stars' distances are measured by using parallax, but I want to know how the actual telescope measures the parallax angle. Any helpful links/ explanations are needed.
0
votes
1answer
45 views

(Sound) Echo from X takes 5-7 days, [closed]

Hey I want to describe an event A happening roughtly 5-7 after event B. I'd like to describe it as the 'A happened after the sound of B echo'd off X', where X is recognisable space thingy... (I'm ...
7
votes
1answer
131 views

Where is Voyager 1 (or 2) going? In which direction?

Knowing it has exited the solar system, is it traveling in the direction of the center of the galaxy, away from it, orbiting it, or maybe even going perpendicular from the disk-shaped galaxy?
7
votes
1answer
74 views

How do astronomers find interesting events?

I always wondered how those tiny dots representing moving stars or whatever forming an interesting event (supernova explosions, stars being sucked into black holes etc.) get caught in the huge solid ...
7
votes
2answers
375 views

Why don't we see the galaxy center?

When we look at the sky, and see the Milky Way, we mainly see a band, with no real center. On a more accurate picture we can guess the center of the galaxy (see this picture), but we still don't see ...
3
votes
2answers
276 views

What is the physical, geometric shape of the universe?

I'm not asking about theoretical ball, vs saddle, vs flat surface which is just a metaphor with 2D space. It's hard to say as we see very little of it, and we see them in the past because light ...
3
votes
1answer
64 views

What does it mean for a black hole to “evaporate”?

It says in this Wikipedia's article: Entropy, however, implies heat and therefore temperature. The loss of energy also suggests that black holes do not last forever, but rather "evaporate" slowly. ...
4
votes
1answer
72 views

Latest sunrise/earliest sunset out of phase with solstice?

Everybody knows that the shortest and longest days of the year occur on the solstices. However, examination of sunrise/sunset tables shows that the maxima and minima of sunrise/sunset times are ...
4
votes
1answer
110 views

Could something temporarily break the Moon's tidal lock?

Would it be possible for something to cause the Moon to start rotating at a different rate, breaking its tidal lock with Earth, without ripping it apart? If so, would the Moon's tidal lock eventually ...
4
votes
1answer
145 views

What is the fastest spinning rotation of a Neutron star?

What is the fastest spinning rotation of a Neutron star? I have heard that Neutron stars have a specially fast spinning rotation. What is the fastest?
5
votes
1answer
93 views

What Is The Great Attractor?

I've heard that there is something called the Great Attractor which seems to have some kind of gravitational influence on objects in the Universe. Is this some kind of theoretical notion posited in ...
6
votes
1answer
65 views

What is a Barlow lens?

I am looking to buy a Celestron 21023 FirstScope 76 Telescope, which is quite inexpensive, and it has good reviews on Amazon. One thing that many reviewers have said is that the two lenses that it ...
11
votes
1answer
166 views

Our galaxy, the Milky Way, forms part of a galaxy group called The Local Group. What are the parameters that dictate what a galaxy group is?

Are there different classifications or just the one? How does our galaxy group compare with others?
3
votes
0answers
148 views

What skills would a software developer need to get a job in space research or exploration organization? [closed]

I am in the field of software programming. What skills should I brush up and gear up to get a job in space exploration and the observatory industry? What are various job profiles in terms of software ...
4
votes
1answer
153 views

Telescope buying guide for a beginner in India

I am located in the southern part of India and am looking forward to buy a telescope to gaze up to look ay farther planets, moons in our solar system and take pictures. How should I go about getting a ...
3
votes
1answer
76 views

Which planet or moon has all resources that can be used to sustain life in a controlled biosphere? [closed]

Now that we are making it to Mars, continuing onward, in an effort for humanity to civilize other planets, not just setting up residential colonies, but to mine minerals and carry on geological and ...
6
votes
1answer
83 views

Can Doppler shift make colors of two stars at same distance different?

As you know, Doppler effect can change the wavelength of the light. Suppose there are two stars at same distance and same temperature. If one star is receding and the other star is approaching, their ...
7
votes
1answer
137 views

How do we know Milky Way is a 'barred' spiral galaxy?

In reference to the question, "How can we tell that the milky way is a spiral galaxy?" The answers there clearly sum up the question asked. But Milky Way is not just a spiral galaxy. It is further ...
3
votes
1answer
86 views

Internet Resource which register all Ultra-long Gamma-Ray Bursts

I read in a scientific magazine there was new gamma bursts that last longer than usual. One was detected during december 2010, also known as Christmas Burst: GRB 101225A and another one in 9th of ...
5
votes
1answer
134 views

Light patch in the night sky [duplicate]

I am so sorry for being ambiguous. I'm not an astronomer and have have never actually even bothered to look at the sky before. I don't have a telescope nor camera. Yet, I'm really really curious ...
2
votes
1answer
86 views

The life course for a massive star from birth to death using the HR Diagram

could you explain to me the life course for a massive star (30-40 solar masses) from birth to death using the HR Diagram (by showing key events in its life on the HR Diagram)? thanks
7
votes
2answers
284 views

Why can you see the space station on some days but not on others?

In my area, from December 17th - 26th, you can see the space station every day, twice But from December 27th - January 6th, you can only see it twice My question is, why does it appear for ...
4
votes
2answers
84 views

What does the term alien planet actually refer to?

This article left me wondering what do they mean by the term alien planet? Aren't all planets simply alien by default, or do they mean planets outside our solar system are alien? Do they mean there is ...
0
votes
2answers
185 views

What is the Exact time earth takes to revolve around its axis [closed]

I read that our day is not exactly 24 hours long. If it is not then why weather seasons come at the same time (Summer, Winter, Autumn Spring) ? how it is equalized ? Update: Sorry I could not make ...
6
votes
1answer
175 views

What caused the comet ISON to disintegrate?

So curious to know why comet ISON disintegrated? Well, it went near the Sun but was the Sun the only reason it died? Or is there any other reason for it's fading away?
1
vote
0answers
62 views

Good Introductory Textbooks [closed]

I have a more mathematical background but have always been interested in astrophysics, cosmology, astronomy, etc. There are a lot of popular books on the subject, but I am getting more interested in ...
14
votes
4answers
544 views

How would the night sky look from inside a globular cluster?

When the weather is clear, we can look at the stars. And we normally would see several thousands of them, they all being more than a $\textrm{pc}$ away from us. Now, there are globular clusters, ...
5
votes
1answer
173 views

If we were to see the Sun with our naked eyes from the Orion belt, would all planets be encompassed inside the star? Is this calculable?

When we see a star it looks much bigger in diameter to us than it really is, this picture (extracted from here) explains what I mean: Notice that the point we see in the skynight, represented by ...
7
votes
1answer
47 views

How close are we to having the technology to measure planetary obliquity for exoplanets?

As far as I can tell, we do not yet have the precision to even put reasonable bounds on an exoplanets obliquity, but wikipedia seems to indicate that this may be possible in the "near future." It ...
7
votes
1answer
159 views

Is it possible for a moon to orbit a planet floating free in the galaxy rather than orbiting a star

This article got me thinking, can a planet hold a moon in orbit if it is just floating in the galaxy by itself not as part of a star system? Can a celestial body even qualify as a planet if it is ...
8
votes
3answers
363 views

Why are orbits elliptical instead of circular?

Why do planets rotate around a star in a specific elliptical orbit with the star at one of it's foci? Why isn't the orbit a circle?
2
votes
0answers
35 views

Why the earth revolves? [duplicate]

Why do the earthor any other planet continue to revolve around the sun or a star in general and that also with constant time period?What is the reason behind it?Other than gravitational force is ...
17
votes
4answers
858 views

How can we tell that the Milky Way is a spiral galaxy?

From Earth, we can distinguish the type of another galaxy very easily simply by observing the shape, colour, and structure of the galaxy when we image it. But since we are located inside the Milky ...
4
votes
1answer
114 views

Can I see the star of Bethlehem at Christmas? [closed]

In the Christian tradition the first Christians are believed to be three wise men who followed the star of Bethlehem to the stable where Jesus was supposed to be born. Is it with some accuracy known ...
11
votes
1answer
155 views

How stable are Lissajous orbits?

Now that the Gaia Space Telescope is on it's way to the Sun-Earth L2 Lagrangian point (SEL2), I start wondering about the stability of Gaia's orbit there. The Planck Telescope is already there, as was ...
7
votes
1answer
101 views

Did a piece of Halley's comet strike the Earth 1,500 years ago?

A friend showed me an article saying that there's evidence that a piece of Halley's comet may have struck the earth about 1,500 years ago. Is anyone here aware of such evidence?
4
votes
1answer
185 views

Solar Noon: meridian crossing time versus time of maximum elevation

According to the first paragraph of the Noon Wikipedia page, solar noon is the moment when the Sun crosses the meridian and is at its highest elevation in the sky. The wording there suggests that ...

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