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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Why do telescopes move synchronously?

Here's a very nice video (see it in HD) of timelapses captured at the atacama desert. In the beginning of the video you can see that 4 telescopes move synchronously. Could anyone explain why? I always ...
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6answers
5k views

Why can't we see light travelling from point A to B?

Lets say we have a cloud of dust which is a lightyear across and someone shoots a beam of light from point A to B , why it is not possible for an observer far far away to see the light while it ...
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0answers
37 views

What are some of the observable effects of black holes

Is there some kind of of observation of a black hole (or a black hole candidate) which could be made from earth, and which might be able to distinguish between two Black Hole models? (1) the classical ...
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1answer
36 views

Is it possible that a satellite once was a small planet?

Very common fact that a planet has satellite which revolves around it and has an impact on that planet too.Is it possible that a small planet had been bombarded with a big planet and transformed ...
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23 views

Does every particle in a neutron star accretion disc undergo Thomas precession?

Assuming, based on this wikipedia article Accretion Discs That accretion discs surrounding neutron stars are diffuse (I take this to mean they are composed of a gas and / or plasma). That the ...
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1answer
52 views

What is this big, white, dense, circular collection of stars in this picture taken from a Telescope? (See the image)

I was visiting this website- http://crest.iiap.res.in/iaonightcam.html, where there was a picture of the night sky coming live from a Telescope. My question is, why is there so many stars in this ...
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1answer
36 views

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
70 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
30 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
30 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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1answer
31 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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1answer
62 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
52 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
44 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
40 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
84 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
94 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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0answers
21 views

Solar time correction due to longitudinal difference

I've been always calculating the correction in solar time due to difference between observer's meridian and the meridian on which the local standard time is based using the following formula "Design ...
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2answers
1k views

Do we know what event caused the Sun and Solar System to form?

Some stellar formation theories suggest that stars are formed by shock waves from trigger events such as supernovae. This excerpt from Star Formation basically gives the background to my question: ...
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1answer
537 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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1answer
55 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
90 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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0answers
52 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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1answer
43 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
54 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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1answer
45 views

Standardising shadow length on sundials

The sundial is fundamentally flawed in that the length of each hourly shadow changes with the seasons. If the base of the sundial was engineered to move cyclically on an anual basis however, the ...
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1answer
124 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
125 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
103 views

How is “little $h$” measured in cosmology? The dimensionless parameter from the Hubble constant, $H_0$

Hubble's law has been well-know for close to a century now. It is written as $v = H_0 d$ where the Hubble constant $H_0$ is the constant of proportionality between recession speed $v$ and distance ...
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0answers
26 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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3answers
968 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
27 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
95 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
170 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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0answers
17 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
18 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
82 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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0answers
28 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
93 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
84 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
31 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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0answers
31 views

Need help with which books I should buy [duplicate]

I need some help with witch books i should read. I would like to study science, physics, quantum physcics, astrophysics and all other kind of physics. Hit me with the best books inside of thoes ...
3
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2answers
109 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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0answers
19 views

How do I calculate the right ascension of the ecliptic at the points where it intersects the horizon?

Given an observer's location on the Earth's surface, and time, how do I calculate the right ascensions of the points along the ecliptic where it intersects the observer's horizon?
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0answers
29 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
24 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?
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1answer
68 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 ...
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1answer
85 views

Do the arms of a spiral galaxy spin around like a candy bar in long spirals?

Because the arms of a spiral galaxy have a linear center, perhaps they rotate around their center same as a candy bar spiral or a spiral of smoke? Have similar movements within galaxies been measured? ...
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1answer
103 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, ...
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2answers
49 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 ...