# All Questions

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### What did New Horizons photograph that was close enough to be out of focus? [migrated]

The picture below shows a Kuiper Belt object and a number of stars. It was recently taken by the New Horizons probe and published by NASA. The arrow points at the KBO and the rest of the bright ...
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### Are we moving faster than the Cosmic microwave background radiation?

if the Cosmic microwave background radiation is coming towards us in the speed of light and all matter and energy was singular at the big bang, doesn't that mean we somehow moved faster than the speed ...
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### Replacing the tripod on a Celestron Travel Scope 70

I have a Celestron Travel Scope 70. The tripod seems incredibly wobbly, making it very difficult to view anything without the whole system bobbing up and down. I was thinking about replacing it with ...
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### Which lens and magnification is best to see planets?

I just bought a Celestron Travel Scope 70 and it comes with a 20mm and a 10mm eyepiece. I get a good view of the Moon but I am not able to see Jupiter, Saturn or Mars as expected. I read about the ...
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### Does the retrograde movement affect the true angular distance between 2 planets?

I need to calculate the relative angular path between two planets in the geocentric view or in other words the number of degrees of a circle one planet travels away from another planet around the ...
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### What is the reason the Chinese want to measure the <30Mhz radiation behind the moon?

On earth it is difficult to measure radiation below 30MHz due to our atmosphere. But why do they want to measure this radiation behind the moon. It has something to do with the big bang, but isn't the ...
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### Could the earth become a star if more mass was added?

I've heard that the only difference between a star and a planet is mass, meaning that if planets accredited enough mass they would too become stars. Does this mean that the star started off as a ...
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### Are white dwarf stars supported by proton degeneracy as well?

In general, fermions form a degenerate gas under high density or extremely low temperature. It's clear that white dwarf stars are supported by electron degeneracy pressure. However, there are still a ...
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### Have there been successful attempts at spotting Neptune with the naked eye?

As pointed out here, the limit of naked eye visibility for people with extremely good night vision is about magnitude 8.5. Neptune at opposition is much brighter at magnitude 7.7, so it should be ...
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### Is Universe Sandbox 2 realistic?

Universe Sandbox 2 is the second installment of Universe Sandbox that is available on Steam. It is an educational simulation game based on astronomy and anything space, it ranges from supernova ...
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### Star formation: When a nebula collapses, is it only the gasses that form the star?

A nebula is made of dust (elements heavier than He and H) and gas (H and He). Stars are made when nebulae's collapse and hydrogen begins to fuse. 99% of nebula material goes into making the star. The ...
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### What is the shape (along the plane, not up-down) of stellar orbits in flat spiral galaxies

What I mean is, with a central mass orbits are relatively simple, but orbits around the galaxy are different, in essence as the star orbits through the dark matter halo, the further it moves away from ...
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### What is the word for space that is in the solar system, but outside the heliopause?

Wikipedia says the definition of interplanetary space is the region dominated by the interplanetary medium, which extends out to the heliopause where the influence of the galactic environment ...
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### Is Planet Nine observable in principle?

Is so-called Planet Nine (given it exists) observable in principle? By "observable in principle", I mean "if we knew exactly where to look, would we be able (from a technological standpoint) to get an ...
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### Is the composition of stars in future made of more and more heavy elements?

In the beginning stars only consisted of the hydrogen element and due to nuclear fusion of those elements in stars and supernova's more heavy elements were created. Because of that, like our Sun, the ...
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### Why do the planets orbit in the same direction?

Theoretically, planets would have an approximately equal chance of going one way in their orbit or another but in reality, this is not the case (at least in our solar system). Why is this?
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### How does the sun move within the galaxy [on hold]

I am trying to know what is the exact movement of the sun. I saw article like this one http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question18.html and from it I understand that the sun ...
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### Why the light curve goes down when the planet is behind the star?

There is a video explaing the transiting exoplanet light curve — https://www.youtube.com/watch?v=RrusIZaWDW8 It is clear to my why the curve goes down when the planet is between the observer and the ...
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### Why don't globular clusters flatten with a galactic disc?

Globular clusters lie in the galactic halo, outside of the disc. However, galaxies are more or less a collection of material and objects — why is it, then, that most stars form a plane due to the ...
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### Two moons and one Earth?

Can any one explain to me What will happen to Earth if its has two moons? Same Distance & two sides of earth (North & south)? Will it be good for humans or bad?
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### Eyepiece projection photography [on hold]

Nothing is showing up in the viewfinder of camera when I try to do eyepiece projection photography.could I have something set up wrong?
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### a random distribution of RA&Dec

How to make random positions in Equatorial coordinate system? If I divide Dec between -90 and 90 evenly, the space distribution is not random.
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### Why is the CMB not simply travelling parallel to us?

When we look to the distant farthest reaches of the universe we see light that was emitted at the big bang 14 billion years ago. But the universe was tiny back then so that light, which is only ...
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### How can black holes be sometimes so gaseous?

One of the most massive Supermassive Black Hole observed is the one at the centre of the galaxy NGC1600 with a mass of 17 billion suns. It would have a density of ∼0.01kg/m^3, or one part in 100,000 ...
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### How do astronomers distinguish the spectral lines?

As a black body a star emits a continuous spectrum of light and other radiation. I've learned they are capable of knowing of what elements the stars are made of because of the spectral lines. But how ...
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### How would seasons at the equator be if the Earth were tilted 90 degrees? [duplicate]

If Earth's axis of rotation were tilted 90 degrees, what type of seasons would be observed at the equator. My prediction is that there would be no seasons, as the orientation of the equator would be ...
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### How close would merging black holes have to be to feel gravitational waves? [duplicate]

Recently LIGO discovered gravitational waves caused by two black holes that were orbiting each other, and then collapsed into one black hole. A few months later, we find out that this actually happens ...
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### an exercise from Spherical Astronomy by Smart

I want to solve this exercise from Spherical Astronomy by Smart: Prove that, in latitude 45°, the interval between the moment at which a star's azimuth is 90° east and the moment of setting is ...
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### Unable to achieve focus

I feel like this is going to be a duplicate of this question, Astrophotography - Unable to achieve focus with current setup. However, the suggestions to go to a straight adapter doesn't apply in my ...
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### Send a rocket against orbit around the sun [migrated]

I presume it's a bit simplified, but ... What if we launch a rocket, the same speed but opposite direction of the orbit of our planet around the sun. Will that rocket fall into the sun?
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### Is it possible to build space elevators? [closed]

Can we build an elevator so high that it goes out of the earth's atmosphere and can be easily used to launch satellites??
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### Distance and orbital period for terrestrial binary planets

This article, http://phys.org/news/2014-12-binary-terrestrial-planets.html, suggests binary planets could orbit each other at a distance of only three planet radii. For two earth-like planets, that is ...
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### What is the Galactic Latitude and Galactic Longitude? How is different from the latitude and longitude we use on Earth?

It has to something with the positioning of sun and galactic center of the milky way but I wasn't able to understand how for a given star, its co-ordinates are calculated. Some explanation would be ...
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### Having some weird issues with my tracking (Advanced VX)

I need your help! I am having some weird tracking issues with my tripod (Advanced VX). When I setup and calibrated my scope yesterday I took this picture of NGC6888 (90s exposure): As you can see ...
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### Black hole darkness a result of gravity or temporal distortion?

Please correct me if I am wrong as I may have made some incorrect assumptions. Okay so we know that at some stage of "nearness to a black hole", light is no longer reflected back at us from the black ...
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### Black holes and material interaction

I was wondering about what happens when a black hole forms. I mean, a black hole forms when a star collapses, so when an enormous mass of protons, electrons, neutrons etc collapses together. But when ...
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### How to understand orbit definitions

I've been reading about satellite observations (such as this one). The writer uses terms such as these to define the orbit: ...
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### What is the name of the cycle whereby the lunar azimuth and altitude recur on a given day?

Like the Metonic cycle, except for position in the sky, not phase. Original question: If I look up at the moon tonight, how long before it is in the same apparent position, and same phase, again? I ...
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### a math problem in Spherical astronomy [closed]

this is an exercise from Spherical astronomy by Smart, which i want to solve: $\frac{d \eta}{d H}= -\cos(\phi) \cos (A) (\sin (z))^{-1}$ when $\phi$ is latitude, $\eta$ is parallax, $H$ is sidereal ...
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### Could the Sun's magnetosphere block extraterrestrial contact?

I was reading how certain strong magnetic fields can block or alter radio waves so bearing this in mind would it be possible for the Sun's magnetosphere to block attempts to establish radio contact ...
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### What are the requirements to become a planet? [duplicate]

A planet is taught to us (at primary school) as a ball of rock that orbits around the Sun and is similar to our own planet, Earth (in as a ball of rock). But of course, humans have to be more specific ...
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### Virial coefficient when computing dynamical mass enclosed by a rotating galactic disk of gas

Suppose I have a large thin disk of rotating gas in a galaxy -- the disk has a maximum inclination-corrected $V_{max}$ and a maximum radial extent of $R_{max}$ corresponding to that $V_{max}$ ...
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### How can there be 1,000 stellar ancestors before our Sun?

I've heard from a few sources recently that the Sun is a 1,000th generation star, meaning it had a thousand stars that came before it based on it's heavy element content. I understand that earlier ...
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### Would a viewer see Earth from the rim of Shackleton Crater?

I've been researching this but so far have not found an answer. If you were standing on the top of the rim of Shackleton Crater at the lunar south pole, would you be able to see any of Earth? I can't ...
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### Could this three moons system be stable?

In my fictional world I have selected all parameters to maximize the Hills Sphere of my planet. The planet has three times Earth's mass and it is located in 2 AU from its star that's 1.4 times more ...
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### What would Earth be like without the Moon?

If somehow our moon was destroyed (for example by an asteroid) what would happen to Earth? Would the Earth be affected by the absence of the moon? Would humans be able to live normal lives without ...
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### Is there always visible airglow from space? [migrated]

Looking at time lapses taken from the International Space Station, I discovered that earth atmosphere can glow at night, even when it seems that those pictures were taken far away from auroras. ...
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### Where can I find the DR12 SDSS dataset in their website

I have to cross-match the SDSS DR12 dataset with that of GALEX but apparently I cannot find the fits document which has the same field as that in GALEX. I have explored the website but I couldn't find ...