The science dealing with objects and phenomena located beyond Earth. In particular, this applies to observations and data. At its core, astronomy is the physically informed cataloging and classifying of the contents of the universe in order to better understand what is out there.

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6
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4answers
105 views

Does the current light pollution set a fundamental limit for the range of Earth-based telescopes?

As far as I know, all deep-sky pictures are captured with the Hubble Space Telescope. If there would be no atmospheric distortion, could we make deeper pictures in the optical spectrum with ...
7
votes
1answer
88 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 ...
5
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1answer
4k views

How do astronomers measure the distance of the planets from its star?

I know they have accurate means of measuring the distance of the planets in the Solar System from the Sun. I'm skeptical how can they use the same tools or techniques for other systems so far away as ...
4
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2answers
166 views

What is an extreme deep field image (XDF) and how is it captured?

NASA recently took this Extreme Deep Field image (XDF) that is the area of only small fraction of the dia of moon and contains 5,500 galaxies. Nasa says this was capture by extreme long exposures so ...
1
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1answer
282 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 ...
1
vote
1answer
75 views

how is the reference for the star maps in google determined?

If I go to google sky - http://www.google.com/sky/ Ihere is a longitude and latitude measure at the bottom of the page. Iow are these coordinates determined and who sets it? Do those coordinates ...
1
vote
1answer
207 views

What are “cycles of anomaly” and “cycles of longitude”?

In several early (pre-1600) astronomical texts I read about "cycles of anomaly" and "cycles of longitude", but it us unclear to me what these terms mean. They were clearly familiar to authors at the ...
5
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1answer
1k views

When and how were relative distances to the planets first measured?

I understand that the absolute distance to a planet can be measured using earth-baseline (e.g., diurnal) parallax, and that the first reasonably accurate such measurement was made for Mars by Cassini (...
2
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1answer
1k views

How did Copernicus establish the relative distance to the superior planets?

I understand that the relative distances to the planets had been calculated using various methods since ancient times, and, in particular, that the assumptions of the Copernican model of the Solar ...
5
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2answers
563 views

The “official” mass of the sun as unit?

I'm searching for the "official" mass of the sun as a unit in astrophysics. The mass of the sun can be calculated by: $M_{\odot}=\frac{4\pi^2\times(1 \ \text{ua})^3}{G\times(1\ \text{year})^2}$ So ...
1
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1answer
189 views

converting daily global radiation into hourly values

I would like to convert daily global radiation into hourly solar radiation. While I do not know the terms, I tried using below equations I found in the papers but I have negative radiation values ...
3
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1answer
82 views

Assuming an observer is 50 light years away, in the plane of the solar system and observing earth, what is the light flux of earth he would see?

As in, from what the planet emits and re-radiates out into space (this is going to be important if we are to image any Earth-like planet)
2
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1answer
466 views

Did Aristarchus take the radius of the Earth into account in calculating the distance to the Moon?

My text says that Aristarchus (310 BC – ~230 BC) measured the "angle subtended by the Earth-Moon distance at the Sun" ($\theta$ in the figure below) to establish the relative Earth-Moon and Earth-Sun ...
6
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2answers
2k views

What are the differences in using an eyepiece with a barlow instead of a shorter eyepiece?

I intend to start making visual observations, and I want to know more about the difference between using barlow lenses and one or two eyepieces and using a complete kit of eyepieces, both for ...
4
votes
2answers
251 views

How could Horrocks have measured the AU?

I have always understood that the great historical significance of the transits of Venus, and the reason for the expeditions mounted to observe it, were that, by observing it simultaneously from two ...
3
votes
1answer
915 views

Would Titan moon blow up if you light a match?

Given that the atmosphere of Titan is mostly methane, and from a comment on this TED talk... Would it blow up from a lighted match-stick? Seems like it's at least plausible. But, wouldn't the lack of ...
3
votes
1answer
156 views

Why a star commonly exhibits 6 rays?

Have you realized, that often the photo of a star shows 6 rays spreaded symmetrically around it, independently of the camera chosen? Do you have idea of what kind of optical phenomena is behind it?
4
votes
1answer
147 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 ...
1
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1answer
59 views

Derivation of superluminality in astronomy

Can somebody provide derivation of the relativistic explanation of (apparent) superluminality in astronomy? The derivation on wikipedia seems to be a bit confusing.
13
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1answer
676 views

What percentage of the sky is occluded by stars?

If you drew rays from the center of the earth out to infinity at every angle, what percentage of them would intersect a star? Extra details: Assume the rays are mathematical rays, or that they ...
4
votes
3answers
916 views

Sky-Watcher Skyhawk 1145P SynScan AZ GOTO

What is the experience using the Sky-Watcher Skyhawk 1145P SynScan AZ GOTO telescope and can it be recommended for a new astronomer? Is it any good?
5
votes
5answers
2k views

Curiosity Rover (MSL): specification / dimensions

I have been looking all over and I can't find a detailed specification about the Curiosity Rover. The length is about 10 feet but it would be cool to find out the dimensions of the wheels, clearance ...
20
votes
3answers
1k views

Direct observations of a black hole?

I'm not very knowledgeable about physics generally, but know that nothing can escape a black hole's gravitational pull, not even light (making them nearly invisible?). My question is: What has been ...
4
votes
3answers
231 views

How empty of fuel are spacecraft booster rockets typically?

A recent XKCD What-if article mentions the situation where each additional kilogram of cargo to LEO requires an additional 1. 3 kilograms of fuel, which in turn requires fuel to carry (simplification)....
6
votes
2answers
568 views

Is dark matter really present around the sun?

Recently I read an article that there is dark matter around the sun but if it is so, than why can we see it clearly. If it is called matter than it shall show some hindrance in radiation we receive ...
2
votes
1answer
245 views

What is the diameter of the sun as a function of wavelength/frequency (around 10GHz)?

I have this vague recollection of being told that the diameter of the apparent surface of the sun is a function of what band you observe it in. I'm looking for a model of this that works for bands in ...
7
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2answers
957 views

How would one navigate interstellar space?

Headed out from Earth within the Solar System, Sol and Earth both may be used as reference. When traveling in interstellar space with stellar systems themselves traveling at varying velocities even ...
3
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2answers
189 views

Oort cloud blocking light?

Is the Oort cloud blocking a substantial amount of light in the visual spectra, making it harder for observers seeing outside the solar system?
0
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1answer
47 views

Does an uneven and/or moving surface affect quality when using a solar filter?

I have chosen to make my own solar filter using Baader as opposed to Mylar or anything else based on these: http://physics.stackexchange.com/a/25204/6805 and http://irwincur.tripod.com/...
5
votes
3answers
208 views

Why are planetary systems so rare?

According to this site there are 258 know planetary systems and 302 planets. Mostly each of the listed system has only 1 planet of Mercury's or Mars' size, while our system has up to 8 planets. From ...
0
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1answer
62 views

Is it possible to check from the EM waves(basically Light rays)?

Is it possible to check from the EM waves(basically Light rays), if there are any extraterrestrial objects interference/passage during its travel from the Sun? I mean, can these EMs from the Sun be ...
6
votes
1answer
961 views

What telescope would I need to observe Mars's polar caps?

What telescope refractor aperture size would I need to observe Mars's polar caps? I have a Levenuhk Strike NG 80mm, and I can see red disk of planet but cannot see any details on the surface.
1
vote
2answers
457 views

Light pollution calculation using camera

Is it possible to calculate light pollution values using camera (analyzing camera feed) integrated in new smartphones (8 Mpx camera) but with pretty decent accuracy? Or that is only possible with ...
0
votes
1answer
259 views

Reflectance of Round Moon vs Flat Moon

Treating the moon as an ideal, bright Lambertian reflector, I was trying to compare its efficiency as a light source to an equally-sized flat sheet of drywall. It's pretty straightforward to set the ...
1
vote
2answers
307 views

Will Pluto be in the ecliptic plane when New Horizons passes by? Was this deliberate?

From the illustrations at the New Horizons website it seems that Pluto may be in or near the ecliptic plane when New Horizons passes by. Is this intentional? Of course Pluto was to move to that ...
12
votes
2answers
504 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 ...
4
votes
3answers
73 views

Can the Hanbury-Brown and Twiss effect be used to measure the size of composite objects like galaxies?

I know that the Hanbury-Brown and Twiss effect can be used to measure the size of stars. Can it also be used to measure the size of galaxies?
0
votes
2answers
299 views

What's the evidence supporting 1 singular Big Bang? [duplicate]

Possible Duplicate: What has been proved about the big bang, and what has not? I love to dabble with science, I'm by no means a scolar in this field. One thing that haven't seen proven yet (...
0
votes
1answer
90 views

What does the latin letter mean in Bayer name of a star such as “$\Upsilon$ Andromedae $b$”?

What does the latin letter mean in Bayer name of a star such as the "$b$" in "$\Upsilon$ Andromedae $b$"? I tried in vain to look it up in Wikipedia or elsewhere on the Web.
3
votes
2answers
159 views

Black hole Cyg X-1 doesn't seem dense enough

According to wikipedia, here are the Cygnus X-1 vital stats: Mass 14-16[7] M☉ Radius 20–22[8] R☉ A radius of 10 R☉ means a volume of 10^3 = 1000 Sols. ...
2
votes
2answers
4k 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 ...
4
votes
1answer
228 views

Why isn't sunset time in sync with solstice?

The winter solstice in the Northern Hemisphere in 2011 is on December 22. But if I look at the sunset times for a location such as Washington, DC on the USNO site, the sunset time starts reversing ...
4
votes
1answer
27 views

What demonstrations for a five-hour optical and radio astronomy workshop? [closed]

I volunteer at a group that has restored the oldest German radio telescope. We are now at a point where we want to invite interested amateur astronomers and school children to workshops. I'm currently ...
3
votes
2answers
115 views

Cannon on spacecraft: hitting yourself

Some Soviet space stations reportedly had anti-aircraft cannons installed. Could such a cannon hit the firing space station accidentally on a subsequent orbit? The muzzle velocity of the cannon is ...
2
votes
1answer
78 views

Sunrise time across the globe?

This question is more astronomy related, I started thinking when I heard from one of my friends living in Jiamusi, that Sun rise at 02:00 and sets at 14:00, I know that this place is more near to ...
2
votes
2answers
139 views

How bright are auroras (aurorae)?

Digital cameras are making the recent auroras look magnificent, but what are they like to the naked eye? Are they comparable in surface brightness to the Milky Way?
9
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2answers
3k views

How can the date of lunar eclipses be calculated by hand?

How can the date of lunar eclipses be calculated? Especially without the aid of a computer.
0
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0answers
63 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?
2
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2answers
56 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 ...
9
votes
2answers
2k 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.