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.

learn more… | top users | synonyms (2)

3
votes
1answer
545 views

What is the future of gravitional lensing? [closed]

What do physicists expect to find or accomplish with gravitational lensing in the next 15 years? Is there a specific type of object, or a concept that they are looking for?
9
votes
3answers
8k views

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! ...
2
votes
1answer
64 views

Observed gravity of Venus aside from the Magellan probe

I have been searching but cannot seem to find it. I would like to know what the surface gravity of Venus has been observed to be from different missions/probes that were sent to Venus on separate ...
3
votes
2answers
112 views

Could some astronomical objects have superconducting properties?

The colder it is, the more efficient the superconductivity process works. And as we know, if there is no star nearby, space gets pretty cold. I do appreciate that many condensed, burnt out, stars ...
2
votes
2answers
102 views

Is it possible to build an optical system that increases the perceived surface brightness?

So is it possbile to build a system from lenses and mirrors that can make faint gas nebulas brighter or can be used as nightvision? If you increase the size of the aperture of a telescope it will ...
1
vote
0answers
63 views

Does the Earth's moon have a moon of it's own?

Out of simple curiosity, does anybody know if any searches have been done to check on the possibility that the earth's moon has a moon of it's own? Excluding man made objects, of course. I would ...
0
votes
2answers
310 views

Next crescent moon?

How do I find the date of next crescent moon on Wolframalpha or any other site which tells the appearance date time of next crescent on a specific location? I am searching for it to look for 1st of ...
2
votes
0answers
309 views

Precession of Mercury (Python simulation)

I was trying to simulate the precession of Mercury based on the perturbed solution, and my questions about its implementation in python can be seen here: ...
0
votes
1answer
49 views

Would the Hubble Space Telescope be of benefit for optical astronomy at Lagrangian L5 point?

The Hubble Space Telescope will enter a decaying orbit in 2024. This is a physics based question, so I don't want to get into the engineering details more than necessary. Just for background, the ...
1
vote
1answer
73 views

Do Massive Twin Quasar Jets Condense into separate Spiral Galaxies?

I was looking at a quasar, radio image of “Cygnus A”. Do the massive twin quasar jets condense into two separate galaxies? Do the average twin quasar jet emissions, plasma, condense, turn into ...
0
votes
2answers
137 views

Mass-to-light ratio and rotation curve from brightness profile

This should probably be basic but I've been looking for days and I can't find how to (I'm probably over complicating, but still). I want to calculate a rotation curve for some spiral galaxies. From ...
1
vote
1answer
144 views

What is the reason we originally and still use the non-SI unit, the Jansky?

The Jansky is the unit for spectral flux density. It is defined as $$1 {\rm \ Jy} = 10^{-26} {\rm W \ m^{-2} \ Hz^{-1}}$$ in terms of Watts per square meter per Hertz. I've never quite understood ...
0
votes
0answers
43 views

Magnification: Microscopes Telescopes

What is the difference between the way a microscope magnifies say a star and a telescope say a cell? Why is it, that the eyepiece of a telescope magnifies stronger when it is smaller and with a ...
1
vote
0answers
91 views

Structure formation: growth of density perturbations in sub-horizon vs super-horizon scales

I've always had difficulty visualizing how sub-horizon scales work versus super-horizon scales. Inflation causes perturbations due to quantum fluctuations. These are under-densities and ...
14
votes
3answers
1k views

How many observations are needed to determine a comet's orbit?

Based on the following facts: We have Kepler's laws of planetary motion. We have a good knowledge of the positions and orbits of the gravitationally significant objects in the Solar System. We can ...
0
votes
0answers
33 views

observational-astronomy

I am looking for the current location of the line of apsides in tropical astrological coordinates; I tried using the sun's position at the time of earth's perihelion, but the results vary too much. ...
7
votes
1answer
335 views

Is it feasible to measure the energy of cosmic ray muons with a consumer Digital Single Lens Reflex camera?

I have read this article SIBBERNSEN, Kendra. Catching Cosmic Rays with a DSLR. Astronomy Education Review, 2010, 9: 010111. and it talks about estimating the muon cosmic ray flux by means of a DSLR ...
13
votes
5answers
5k views

Where can I find public domain astronomical pictures?

Where can I find public domain astronomical pictures of nebulae, stars, etc. that can be freely used?
4
votes
1answer
207 views

Mass and distance of the bodies of the solar system?

This might be a bit of a historical question in nature. Obviously given that we know the constant G, the mass of the sun, and the distance between a solar body and the sun we can calculate it's mass. ...
0
votes
0answers
20 views

How do I compute the galactic cooridinates of the Earth for a given date?

The question is simple enough, but I wasn't able to find any tools online. Does anyone know of one, or a simple formula?
2
votes
1answer
53 views

numerical galaxy morphology classification scheme

For an assignment, I've been told to divide up the galaxies with a Virgo Cluster Catalog number into early and late-type galaxies using the GOLDMine database, http://goldmine.mib.infn.it:8080/ ...
7
votes
2answers
14k views

How could scientists know how far a star or galaxy is from us?

How do astronomers measure how far a star (or galaxy) is away from the earth? How would they know that it has taken 13 million years for light to travel in space before it reaches us?
0
votes
0answers
34 views

Can you explain in mathematical term of how the moon makes the earth spin stable?

I heard that our moon keeps the earth's rotation at the same angle. This is, as the Science Channel explained, is essential for regular seasons on earth. I am not interesting in the fact why it is ...
3
votes
1answer
499 views

What is the precise definition of “cadence” in astronomy?

I'm finding it difficult to find a precise definition of "cadence" in astronomy. This term is commonly used to describe the data of astronomical surveys. For instance, one of the data products for the ...
3
votes
2answers
121 views

Olbers Paradox Solution

Olbers’ Paradox says that in an infinite universe every line of sight will end on a star. Surface brightness is independent of distance (moving a star further away makes it smaller and reduces its ...
2
votes
0answers
51 views

How accurately do Airy discs need to be superimposed in an optical interferometer to create fringes?

In an astronomical optical interferometer, what is the largest amount of error in the alignment of the Airy disks of point source star images from different arms of the interferometer that will still ...
4
votes
2answers
439 views

How were the ratios of distances between planets and the Sun first calculated?

I was reading some literature and I found that long before the actual distances between other planets and Earth or distance between Sun and Earth were known, physicists had calculated the ratios ...
10
votes
2answers
23k views

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?
4
votes
2answers
188 views

How do we measure distance using parallax?

This is a quick mock-up of how stars are measured using parallax method. My question is : How on earth (literally) do we measure the anfle $\theta$? Is theta measured from the zenith of Earth? ...
0
votes
1answer
119 views

How to measure distances to stars by means of spectroscopic parallaxes?

How to measure distances to stars by means of spectroscopic parallaxes on practice? What is the accuracy of measuring distances using this method compared with distances based on HIPPARCOS ...
7
votes
1answer
326 views

What are the different ways to measure the spatial curvature of the universe?

Just what the question asks. Assuming the Friedmann-Rovertson-Walker (FRW) metric, what measurements can be performed to determine the spatial curvature of the universe.
1
vote
1answer
660 views

How does color of galaxies explain their distance?

Why do distant galaxies have different colors than closer ones?
0
votes
1answer
222 views

Resolving power of ultra-telescopes [duplicate]

Assuming we could create and orbit optical telescopes of arbitrary size, perhaps starting with (say) inflatables or active membrane of 100m diameter what kind of resolution in imaging extra-solar ...
1
vote
0answers
31 views

Accretion disks on neutron star binaries

Why does hydrogen gas from accretion disks not constantly get sucked onto/into a neutron star or into a black hole? I understand that some gets sucked into the black hole and some may come down and ...
1
vote
0answers
27 views

Who orbits who? Earth or Sun [duplicate]

We always say that the earth orbits the sun, but how can we prove this? Could we not say that the sun orbits the earth or that the earth orbits Mars?
7
votes
3answers
9k views

How are Cepheids used to evaluate their distance?

Cepheids are used to evaluate distances. What is the math and physics behind their use?
5
votes
1answer
109 views

Can you use pulsar observations to determine absolute time? How long can you go without anything else?

In this old answer of Steve Allen's, he quotes this nice passage Imagine for a moment what would happen if, just as a practical joke, someone found a way to stop all atomic clocks, just for a ...
-1
votes
2answers
287 views

Need help buying binoculars online for astronomy (10x50) [closed]

After reading much online I've decided to by a 10x50 porro prism Binoculars. The one I have in mind http://www.letsbuy.com/celestron-upclose-10x50-p-34652 has BK7 prisms. The one I would like to buy ...
12
votes
3answers
587 views

If time standard clocks and any memories about the time standard are destroyed, can we recover the time standard again?

Assume the time standard clocks and any memories about the time standard are destroyed. Can we recover the time standard again exactly? Recovering the time standard again means we can determine the ...
20
votes
4answers
13k views

How do astronomers measure the distance to a star or other celestial object?

How do scientists measure the distance between objects in space? For example, Alpha Centauri is 4.3 light years away.
3
votes
1answer
162 views

Do we actually measure distances in light years?

The cosmic distance ladder has a wide range of length scales, which are quite difficult to measure and to conceptualize. These distances are commonly quoted, particularly in less technical articles, ...
2
votes
2answers
64 views

Color of objects in Yellow sun

The sun appears yellow but the objects on the earth appear as if they have been illuminated in white light. Are all objects that we see in sunlight actually in a yellow shade, and would appear ...
0
votes
0answers
43 views

Perturbations of planetary Orbits

I have, for years, been an Astronomy and physics nerd. For the first while, I was a total astronomy nerd. Then I slowly transitioned into physics and have been, for less than a year, a physics nerd. ...
2
votes
1answer
160 views

Is there a map which shows all the black holes in our galaxy?

I am looking for a map which shows all black holes in the Milky Way. See this exoplanet map for what I mean. If it is not existing (yet). Is there at least an online catalogue which summarizes for ...
31
votes
8answers
29k views

Why CAN we see the new moon at night?

I understand that the Moon's phases are determined by its position in orbit relative to the Sun. (See: Full Story on the Moon). The "shadow" is not cast by the Earth (a common misconception - this is ...
1
vote
2answers
71 views

Mass of NGC 1097 Galaxy

I've been looking all over the internet for this and can't seem to find a reference. Can anyone refer me to a paper citing the mass of NGC 1097 based on luminosity?
1
vote
1answer
187 views

Why is the lyman alpha line asymmetric at high redshift?

If someone could explain this to me I'd be very grateful, thanks.
2
votes
1answer
107 views

Using nuclear bombs to detect near earth orbit objects

This question is based on an article written some years ago by A. C. Clarke, in which he attempted to solve two problems with one solution. His idea was to remove the Earth's stockpile of nuclear ...
1
vote
1answer
83 views

Redshift of supernova light curve

I am trying to understand how the width of a supernova light curve depends on the redshift of its component frequencies. Let us make the simple assumption that the light curve is Gaussian. The ...
1
vote
0answers
37 views

Which technique is used to measure huge astronomical distances which are in terms of billions of light years? [duplicate]

I know what a "light year" means. However, I am very curious to know about the technique through which scientists are able to calculate the distance of various astronomical bodies from earth which are ...