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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Calculate which star is at Zenith using my latitude, longitude, and time

I'm developing a Planetarium software and I have no idea about how what stars and planets are visible today (mm/dd/yyyy hh:mm) given a latitude and longitude. Reading this tutorial, I have found how ...
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5answers
147 views

Superheavy… “Stars” production of super heavy elements w/o solar fusion

Just a soft question: Let's say a field of stars all die within a short amount of time. Just for argument's sake they produce a debris field of iron ( or any other heavy element). Provided that ...
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1answer
43 views

Observations of erratic rotation of asteroids

An asteroid generally has an irregular shape, therefore, one would expect its rotation is quite erratic in some sense. Are there any observational examples?
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1answer
60 views

Is surface brightness constant as a function of distance?

Well of course it is - the flux drops off as the square of the distance, but the solid angle subtended by the source drops off the same way, so surface brightness is constant, right? Yet other ...
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2answers
267 views

Explain relationship between angular diameter distance and luminosity distance, Etherington Theorem

I have a question relating to the Etherington Theorem. The luminosity distance is defined by the equation for flux, i.e. $F=\frac{L}{4\pi D_L^2}$ where flux is in units energy per unit time ...
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2answers
169 views

Is there a confirmation of dark matter signal?

Dark matter, as we know does not emit light, so confirmation of its presence is indirect. Are there any recent indirect confirmations of dark matter. A place one would look for in detecting dark ...
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1answer
52 views

Sol Lagrange points

Where are the Sol-Sagittarius A* Lagrange points, what is located there, have we ever focused a telescope to look? And the larger question, could the existence of these points offer some explanation ...
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3answers
574 views

“Reverse engineering” of a horoscope?

I'll start with a disclaimer -- this is not a question about astrology itself, I'm neither trying to refute nor to defend astrology. I'm interested in purely technical things, which are mostly ...
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1answer
310 views

How can we see objects that are so far away? [duplicate]

The HUDF used to be the deepest image of the universe ever taken by the Hubble telescope, the furthest star in this image is 59000 light years away. The star in question: Now Imagine a light ...
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1answer
65 views

What is the safest distance to create a star? [closed]

What is the safest distance we could create a star without affecting the gravitational force of our solar system? Thanks.
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1answer
58 views

Effect of dark matter on measuring our weight

We know that 95% of the matter in the universe, and all around us, and in our room is dark matter. Dark matter does interact with normal matter only through gravitation. So, does it have an effect on ...
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1answer
100 views

Do stars produce spatially coherent light? Why?

If I understand correctly, the existance of astronomical interferometry implies coherence of light produces by stars. The temporal coherence can probably be achieved by wavelength filters. But what ...
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2answers
95 views

What's the point of looking at distances beyond $13,7$ billion light years?

Question: Provided that the age of the universe is $13.7$ billion years, but the actual radius is $48$ billion ly, what are we really going to see if we built a telescope powerful enough to reach ...
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1answer
198 views

Did dark matter cause the formation of the Solar System?

This question is related to my previous question on Solar System Formation and is a pure thought experiment, with as few as possible assumptions made. From my previous question, I learned that stars ...
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1answer
129 views

Drift of Earth's orbit?

How much has Earth drifted (inwards or outwards) from its orbit about the sun? Or has Earth has not moved at all, compared to, say, 1000 years ago? 10,000 years ago?
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1answer
546 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?
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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! ...
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1answer
70 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 ...
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2answers
113 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 ...
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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 ...
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0answers
64 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 ...
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2answers
312 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 ...
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0answers
319 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: ...
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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 ...
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1answer
75 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 ...
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2answers
138 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 ...
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1answer
149 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 ...
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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 ...
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0answers
97 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 ...
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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 ...
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0answers
34 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. ...
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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 ...
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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?
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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. ...
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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?
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1answer
58 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/ ...
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2answers
15k 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?
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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 ...
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1answer
526 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 ...
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2answers
123 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 ...
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0answers
53 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 ...
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2answers
476 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 ...
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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?
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2answers
191 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? ...
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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 ...
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1answer
340 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.
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1answer
673 views

How does color of galaxies explain their distance?

Why do distant galaxies have different colors than closer ones?
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1answer
231 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 ...
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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 ...
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0answers
28 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?