# All Questions

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### How large must an object be to be seen through a telescope?

I've studied this in a few optics classes before, but I'm drawing a blank at the moment. If I know the aperture size and focal length of a telescope, as well as how far away the object I want to view ...
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### Hubble law, cosmological redshift and distance

I have got confused with some cosmology formulas which calculate distance. The most famous formula is indeed the Hubble law which says (nowadays) velocity is proportional to Hubble's parameter at ...
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### How to read NOAA/NASA GOES satellite data?

I requested satellite image data (GVAR_IMG) for a project that I am working on from the GOES satellite, but I don't know what format it's in or how to read it. When I open it with a text editor it is ...
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### How did New Horizons take such well-lit pictures of Pluto?

The photos of Pluto from New Horizons are truly beautiful. But considering that Pluto is so far away from its nearest start - our Sun - how is it so well lit up? Did the New Horizons have a massive ...
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### How much more massive would Pluto have to be to clear its neighborhood?

How much more massive would Pluto have to be to clear its neighborhood?
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### Is expanding universe adding potential energy?

A system with two massive bodies has potential energy proportional to their separation. Since the universe is expanding, is the potential (and total?) energy of such a system slowly increasing? What ...
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### How can a planet have a 90° inclination?

Planetary systems as we understand it exist from a disk of mass when the parent star is young. That's why all our planets are in the same plane, or close to it. See also Why is the solar system ...
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### Orbits in a binary star system

I know of three sets of stable orbits in a binary star system: orbiting closely around star A, orbiting closely around star B, or orbiting distantly around both stars (and their mutual center of ...
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### Why do some neutron stars become pulsars? [duplicate]

I suspect this may be an open problem in astronomy, but I have to ask anyway. There doesn't seem to be any large-scale difference in the formation of pulsars from the formation of "normal" neutron ...
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### Do all orbiting bodies eventually collide?

If two celestial bodies are in orbit, will they always eventually collide if not acted upon by outside forces?
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### Where can I find a catalog for stars within 450 light-years of Earth?

Where can I find a catalog for stars within 450 light-years of Earth? I'd prefer one that has approximated masses as well.
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### Massive Nearby Stars

Is there a possibility that I will find records of stars with masses around 25-30 solar masses within 30 parsecs of solar system. If not, how far do I need to look?
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### Pluto- Current theories regarding its geological nature?

The images of New Horizons from Pluto will take more a year to arrive from space, for the moment with have some compressed images as a preview. Nasa has advanced some information regarding the ...
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### Calculating the mass of star

I am doing a project which requires that I have data for the mass of several stars. However, the data for mass of stars is obviously not readily available as it's really hard to calculate. In such a ...
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### Speed of blast from supernova

How fast does the blast front of a supernova expand at? Is it close to the speed of light or is it less than a quarter of the speed of light?
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### Can a supernova make a new star? [duplicate]

Today I was wondering with a friend about the birth of a star. So we know that stars are born from a nebula, but the residue of a dead star (like a supernova) is itself a nebula. So can a star be born ...
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### Any freely available large stellar spectra catalog?

For a non-astronomy personal project I would like to have a large set of optical stellar spectra combined with absolute magnitude when available. I search for a dataset that contains 10k - 10M ...
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### Has SETI data been used for astrophysics? How, or why not?

SETI collects alot of data from space, mostly radio. I wonder if this data has any astrophysics value other than SETI?
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### How will the Breakthrough Initiatives affect other astronomy observations?

BACKGROUND The Breakthrough Initiatives is in the news because of a \$100 million private donation for a SETI project. It doesn't seem to be for building any new observatory (but maybe for buying ...
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### Can a galaxy splits into multiple galaxies?

Is there any naturally occurring event powerful enough that can cause a galaxy regardless of shape and size to divide itself into two or more smaller galaxies?
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### Could an ejected “extra ice-giant” still be lurking in distant solar orbit?

BACKGROUND Hot Jupiters are thought to have migrated inwards, implying that another giant planet has been ejected in order to conserve the orbital momentum of those planetary systems. The number of ...
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### Can we see Earth by looking into space?

It is known that spacetime is curved,so I am wandering to know if its possible to look into space and we see earth (light from earth long long ago). Did I understood spacetime correctly and if its ...
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### Shall we say now that Pluto is “larger than Mercury” ?

http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150717-3 "Scientists working with NASA’s New Horizons spacecraft have observed Pluto’s atmosphere as far as 1,000 miles (1,600 kilometers) ...
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### why do peple think the most energetic events in the universe are GRBs?

Recently people have found supermassive black hole binaries with very short orbital period. link They should be more energetic than GRBs when they merge, right? It seems people do not talk about ...
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### How does the lack of magnetic field on Mars affect the possibility of using electricity there? [closed]

Thank you to all who spend time and energy reading this and using your brains. I am learning about electricity and magnetism and find that they are two phenomena of the same thing. What that is...? If ...
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### Why do we observe spectral lines of specific energy?

The basis of my confusion is that atomic orbitals, even when described accurately by quantum numbers, have definite energies, meaning they represent energy eigenstates of the wave function. They're ...
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### Is the Tombaugh Regio on Pluto visible from Earth?

Is the Tombaugh Regio on Pluto discernably visible from Earth ground based or Earth orbiting telescopes? And more generally, can surface features seen in Hubble images be matched with images from New ...
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### Are lunar occultations visible to the naked eye?

The Moon occults a lot of stars. But are these events visible to the naked eye? Won't it be blinded out by the crescent even at its thinnest just before sunrise? Did ancient astronomers actually ...
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### What is a “jumping trojan”? And what do their orbits look like?

I was googling Neptune's trojan companions and found on Wiki this claim about ~200 km diameter (316179) 2010 EN65: " the object is actually a jumping trojan, is jumping from the Lagrangian ...
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### Does Pluto have impact craters?

I've heard from a lot of sources that Pluto doesn't seem to have any impact craters, but I see a few things that look like impact craters, highlighted in this picture: For comparison, here's ...
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### How significant is a planet's density to the formation of life?

I'm doing some writing set on a fictional earthlike planet that for reasons needs to be substantially larger than Earth but can't have substantially higher gravity. I've been able to compromise with a ...
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### How did our ancestors discover the Solar System?

I wonder, how did our ancestors discover the Solar System? They did not have any telescopes to see distant objects, right? Even a planet looks like a star from a distance. They discovered the ...
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### Whats to be gained from the New Horizons mission once its beyond the Kuiper Belt?

Now that we have seen what Pluto has to offer and New Horizons is headed to the Kuiper Belt, is there anything we can gain from the mission in interstellar space after it travels beyond the Kuiper ...
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### How do you determine which star, between two, is more luminous?

For example, if star 1 is 4x bigger than star 2 but both are the exact same temperature how do you determine which is more luminous?