Questions tagged [astronomy]
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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How is distance between sun and earth calculated?
How has the distance between sun and earth been calculated?
Also what is the size of the sun?
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Differences between astronomy, astrophysics and cosmology? [closed]
What is the main difference between Astronomy, Astrophysics, and Cosmology?
I have the impression that astronomy is a subject that runs parallel to physics but it is outside the physics field. This ...
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How can one get the eccentricity of the orbit of the Sun around center of the Milky Way?
How can one get the eccentricity of the orbit of the Sun around center of the Milky Way? Can it be measured?
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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 ...
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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 - 2000 km....
Elzo Valugi
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Why are all-Sky images drawn as a filled ellipse?
There is some convention? how is this 3d to 2d mapping done?
here an example
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Distribution of star colours in a galaxy
I'm trying to randomly generate a representation of a galaxy.
I have some Idea on the spatial distribution of stars within a galaxy, and I can find plenty of material on the colour of stars, but ...
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If the Earth didn't rotate, how would a Foucault pendulum work?
How does the Foucault pendulum work exactly, and would it work at all, if the Earth didn't rotate?
Foucault
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How/why can the cosmic background radiation measurements tell us anything about the curvature of the universe?
So I've read the Wikipedia articles on WMAP and CMB in an attempt to try to understand how scientists are able to deduce the curvature of the universe from the measurements of the CMB.
The Wiki ...
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What prevents digital interferometry in an optical telescope array?
I understand it is common to combine an array of radio telescopes in to a single instrument using interferometry. This has the photon collecting area of the combined radio telescopes but an aperture (...
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Are there any experimental bounds on the ratio of neutrinos to antineutrinos in the universe?
In the Standard Model, both baryon number and lepton number are conserved quantities (excluding the theoretical possibility of sphaleron processes which are exceeding rare, at least at non-"near in ...
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Do photons lose energy while travelling through space? Or why are planets closer to the sun warmer?
My train of thought was the following:
The Earth orbiting the Sun is at times 5 million kilometers closer to it than others, but this is almost irrelevant to the seasons.
Instead, the temperature ...
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Does Earth have a code name?
Everything we discover in the sky get eventually a code name, like NGC 7293, Simeis 147, etc.
Does Earth/Moon have a code name too? Or it is just Earth/Moon, etc.?
isioutis
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How does the formation of a solar system not break the second law of thermodynamics?
Please forgive: I am a layman when it comes to physics and cosmology, and have tried finding an answer to this that I can understand, with no luck.
As I understand it, the solar system evolved from a ...
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What made us think that Earth moves around the Sun?
Trying to observe the night sky for a few weeks, the motion of the Sun and the stars pretty much fits into the Geocentric Theory i.e. All of them move around the Earth.
What then, which particular ...
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Is the moon a planet?
Can our moon qualify as a planet? With regard or without regard to the exact definition of the planet, can the moon be considered as planet as Mercury, Venus and Earth etc. not as the satellite of the ...
Ujjwol
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Names, maps for Milky Way dust clouds? (Dark Cloud Constellations)
There is a nice image of the Milky Way, labeled with constellations, at 360°x45° panorama with constellations:
It leads me to wonder how much we know about the Great Rift, Coalsack and other ...
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Which is the strongest meteor shower expected in the next years in the Northern hemisphere?
Which is the strongest meteor shower expected in the next years in the Northern hemisphere?
Is it possible to give good predictions for this?
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What is the irregularity in Uranus' orbit that is caused by Neptune?
I carefully read the Wikipedia article Discovery of Neptune, and I don't get what the irregularity of Uranus orbit was that lead to the discovery of Neptune. Years ago, I watched some educational film ...
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Silicon-based life [closed]
My question may not be suitable here, because it's more of astrobiology. Life as we know it is carbon based.
Is life based on silicon possible?
What would the conditions for habitability for silicon ...
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Will the James Webb Space Telescope be able to capture something similar to, or better than, the Hubble Ultra Deep Field?
Will the James Webb Space Telescope (JWST) be able to capture, or ever be used for, anything similar to the Hubble Ultra Deep Field (HUDF)?
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Orange ring in a black hole image
What exactly is the origin of the orange ring around M$87$?
I understand that the image was not taken in the visible light range. The colors are therefore artificial.
I also read that the image ...
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What's the best way to watch meteor showers?
I have read somewhere that the best/easiest way to watch meteor showers is to lie on the ground or other horizontal surface with your feet oriented towards the "apparent point of origin" (what was ...
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Why does a blue sky at dusk appear nearly black through a telescope?
Earlier this evening I was looking at the Moon through my cheap toy telescope (x150 magnification) when I noticed a (rather mundane) optical effect I couldn't explain. The Sun had just dipped below ...
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Has Hawking radiation and black hole evaporation been observed by astronomers?
Has Hawking radiation ever been observed or has there been any attempt of observing them? Do we have any evidence that black holes can evaporate?
I wonder how would one distinguish between Hawking ...
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From how far away could Earth's telescopes detect Earth-like radio signals?
The Earth has been broadcasting human generated radio signals for about 100 years now. If a nearby civilization were broadcasting similar radio signals, could we detect them with our own radio ...
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How distorted does the Andromeda Galaxy appear to us due to the speed of light?
The Andromeda Galaxy appears to us at an angle to the galactic disk, i.e. we are not in the Andromeda Galaxy disc's plane, nor are we near the direction that the galaxy's pole points. Therefore, due ...
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Is the universe a giant telescope?
Due to the space expansion, the universe should act as a giant telescope. The farther objects are from us (beyond the redshift of $z\approx 1.5$), the larger (not smaller!) they should appear in the ...
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Is there a fundamental limit to the temporal resolution of signals from space?
In Earth-based experiments, we can measure phenomenon very rapidly in an experiment given appropriate equipment. Clearly if something takes a long exposure to see (due to a weak signal), then the ...
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Does the Milky Way have dark matter satellite galaxies?
This recent paper by Weinberg et al. discusses that one potential problem with our current model of Cold Dark Matter (CDM) is that is predicts a greater number of satellite galaxies for the Milky Way ...
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How could Tycho Brahe determine positions without accurate clocks?
Tycho Brahe determined the positions of stars and planets to an accuracy of 2 minutes of angle. Pendulum clocks hadn't been invented yet so he couldn't have known the time to better than 15 minutes. ...
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Why can I never see any stars in the night sky?
I have always lived near a large city. There is a stark contrast between the picture linked below for example, and what I see with the naked eye.
Sometimes I can see a few stars here and there, but ...
Hassan
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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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Why is this radio telescope's reflector spherical and not parabolic?
This is the Arecibo Observatory in Arecibo, Puerto Rico. Its reflector is spherical, measuring 1,001 ft. in diameter. It is considered the most sensitive radio telescope on Earth, but the fact that ...
Frank Computer
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Where does a star's angular momentum go as its spin slows down?
So we know that stars slow down as they age. But total angular momentum must be conserved. Where does that angular momentum go?
The dissipation of Earth's tides somehow transfers Earth's angular ...
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What is exactly a Dobsonian, and what are the differences when compared with Schmidt-Cassegrain or Newtonian?
What is exactly a Dobsonian telescope, and what are the differences between this technical choice over a Schmidt-Cassegrain or a Newtonian configurations?
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How many percent of the visible light reaching the Earth are from other stars than the Sun?
How many percent of the whole visible light reaching the Earth are from other stars than the Sun?
Is it maybe 0,5 - 1% or is my guess already too much?
I am interested mainly in visible light, but ...
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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 ...
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Could the earth have another moon?
First, to clarify: I'm not asking if perhaps there's a moon that we haven't found yet. The question is, theoretically, would the earth be able to have another stable moon in addition to the current ...
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How fast will the sun become a red giant?
I've read many accounts of our sun's distant fate, but what I've never heard is on what time scale these events occur.
For instance, when the sun runs out of hydrogen, I presume it doesn't just WHAM! ...
Gary
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How many earth-sized planets have been discovered outside the solar system?
How many earth-sized planets have been discovered outside our solar system? Is there a combined registry of them anywhere? Where might I look for more information?
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Difference between Gunn Peterson trough and the Lyman Alpha Forest? Cosmological implications?
I'm having difficulty understanding the full implications of the Lyman alpha forest and its use in cosmology.
My understanding is this: we detect features in the Intergalactic Medium (IGM) by very ...
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What are ADU (analog-to-digital units)?
Can someone explain simply what are ADU's? I was reading this post here: http://www.qsimaging.com/blog/understanding-gain-on-a-ccd-camera/
However, I still don't quite understand this statement:
"...
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How do air Cherenkov telescopes work?
The very highest energy photons, gamma-rays, are too energetic to be detected by standard optical methods. In fact they rarely actually make it to the surface of the Earth at all but interact with ...
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Observing Jupiter's non-Galilean moons
What strength of telescope is required to observe some of the non-Galilean moons of Jupiter?
My current telescope at 50 magnification resolves the Galilean moons well, but I'm guessing it's far ...
jball
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Why did the june 2011 lunar eclipse last so long?
It was kind of hard to miss the lunar eclipse this week, although I didn't see it in person (Sod's law means that on every relatively major astronomical event clouds cover where I am). From what I ...
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Are Uranus and Neptune too big for their location?
So I was watching some TV, and I heard Dr. Plait mention that the planets Uranus and Neptune are too big to be located so far out in our solar system. Now, I heard his explanation on the show as to ...
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