# All Questions

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### How can we derive photometric redshift?

Is there any good tool than can derive photometric redshift or good reference paper? We need to assess photometric redshift based on GALEX(Fnu and Nuv), Sloan(ugriz) and 2mass(jhk) magnitudes. Could ...
528 views

### How deep and shaped is the depth of a black hole?

A common representation of a black hole is a black circle which if I'm correct, indicates its breadth. This representation depicts it as a 'plate', so a really small depth compared to its breadth. ...
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### Calculating RA/dec from JPL ephemeris data

I'm using JPL planetary ephemerides to calculate the position of planets. Using DE405 ephemeris (using a parser provided by Project Pluto with all tests passing). I am fetching the position of Mars ...
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### Circular formation around the moon

I have seen a large circular formation of cloud around the full moon sometimes. Have anyone seen the same? What is the reason behind this formation? Due to lunar attraction? Most of the sky is empty ...
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### Concerning fate of Milky Way Galaxy

Andromeda Galaxy is the largest galaxy in the galaxy cluster[1] called Local Group[2] and our Milky Way Galaxy as well as some satellite/dwarf galaxies are orbiting around each other within Local ...
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### How long for a complete solar system cycle

Considering the solar system as a closed system, how long until all the planets pass twice by the same position relative to each other? I would say that you'd have to get the length of the year in ...
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### How to calculate magnitude of a star in a triple star system?

I want to find a star's magnitude in a triple star. I already knew the the magnitude of the triple star and the other two star, but I don't quit know how to solve it. Is there a way to find it?
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### Is there a legend for these 88 HST images?

Is there a legend for these 88 Hubble Space Telescope images? I have a 6000px x 4800 px version of this image (reduced & rotated to 480x600 here) that I use for an image slide show. I would ...
107 views

### What is the direction of a comet's dust tail before and after perihelion?

I recently created a visualisation of comet ISON's orbit. However, I received a critique that the dust tail of the comet should be pointing away from the Sun after perihelion. As far as I know, the ...
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### Could there be a closer star to Earth than the Alpha Centauri triple star system, excluding the Sun? [duplicate]

Do we know for certain that the nearest star to Earth, excluding the Sun and the theorized Nemesis, is the Alpha Centauri multiple star system, at +/-4.4 light-years away? Have we been able to ...
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### Are black holes solely responsible for hyper velocity stars?

I read that the stars orbiting around Sagittarius A* (a.k.a the supermassive black hole located at the heart of the Milky Way) move very fast (many times faster than our Sun moves across the galaxy), ...
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### What are the most popular computer programming languages in observational astronomy?

I would like to work in the field of observational astronomy (not so much theoretical astronomy). I currently know two computer programming languages: C# and MATLAB. I have read that computer ...
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### Why are there no green stars?

There are red stars, and orange stars, and yellow stars, and blue stars, and they are all understandable save the fact that there is a 'gap': There are no green stars. Is this because of hydrogen's ...
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### How to find RA 0

I am standing in an open area and can see the sky for a full 360 degrees. I have the coordinates of an object (RA and DEC). Where do I look to find RA 0?
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### Examples of Equal Mass, Unequal Mass and Double Binary Star Systems

Can anyone give me an example of a star (ideally those with a common name e.g. Rigel, Sirius, etc) of the following multiple star systems. Equal Mass Star System, where two binary stars orbit round a ...
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### Astronomical databases for machine learning?

I was reading this question about open problems in astronomy. The bounty-receiving answer says that I have just left the field where some colleagues are trying to develop some software to use ...
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### Does the Sun belong to a constellation?

Each new star we find is generally considered to be part of the constellation it is nearest to. Our Sun is obviously a star, just much closer. Is our Sun part of any constellation? If so, which ...
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### Years, Months, Day, and Weeks?

Sorry if this is a basic question. 1 year = earth revolution around the sun 1 month = moon revolution around the earth 1 week = 7 days = ??? 1 day = earth rotation about its axis Why do we ...
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### Galactic extinction as a function of distance

I am looking at several galactic sources in the $I$, $R$ and $V$ bands and I want to calculate their absolute magnitudes. I can get the apparent magnitude and I know the distance so I just need to ...
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### Variable and Multiple Stars in Hipparcos

Is there any way I can tell from Hipparcos catalog which stars are Binary/Multiple Stars and which are Variable stars?
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### If we built one hundred 3m telescopes and point them to a single star what would be the final resolution?

We'll mount all of them in a same location and connect them to each other (like VLT) so they will combined all the results and will produce some staggering images however my question is, would they be ...
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### Is the universe like the earth?

Is the universe much like the earth, in that if I were to travel in one and only one direction, I'd eventually end up where I started from?
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### Does the Sun's light travel fast enough to have a straight path to Earth?

Hopefully this question isn't too silly. When we travel through space, we use a curved path following an orbit to reach our destinations. As far as I'm aware, we could take a more straight line ...
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### What are Flamsteed numbers?

Can you tell me about Flamsteed numbers? I just know that it is a specific number used for identification of stars. But what is the theory behind it? In what way is the number given to stars?
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### The fastest Probe we could build now

I found this at http://www.nature.com/news/the-exoplanet-next-door-1.11605 Even when launched by one of the most powerful rockets on Earth, boosted by a gravitational slingshot around Jupiter, ...
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### How to differentiate between images of a gravitationally lensed object

The light coming from a distant galaxy or star can be distorted en route to Earth; this distortion is caused by the curvature of space when a massive object is present. My question is, how can we tell ...
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### Do neutrinos have as much information as photons do?

If neutrino detectors keep improving so that a fair number of neutrinos can be observed, would they be as informative for astronomy as photons are? They are of course a very valuable complement to ...
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### Is there Dark Matter inside the Earth?

Since Dark Matter is assumed to interact gravitationally, it follows that the gravitation of massive regular matter bodies should have an effect on it. Even if it is otherwise weakly interacting with ...
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### Time according to the gravity of Sagittarius A?

This may be a really dumb question (I'm more of a Biologist than an Astronomer) so I apologize in advance for my little knowledge pertaining to Astronomy, but, if I'm not mistaken, time is effected by ...
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### Can stars be observed from space by x-rays, near infrared and radio wavelengths? [closed]

I have a doubt. Can stars be observed from space by x-rays, near infrared and radio wavelengths?
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### Why does Earth have more gravitational force than the Moon if I stand on it?

Perhaps this is a silly question but I am trying to understand Einstein's general theory of relativity. I would like to explain my question in more detail. The greater the mass of an object, the ...
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### what is the current explanation for the formation of cosmic voids?

Why aren't galaxies distributed evenly in space, but instead form those sponge-like structures, with huge voids between filaments?
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### Is Earth's 1g solid surface gravity unusually high for exoplanets?

The surface gravities of the Sun’s planets are all close to 1g, 0.38-2.53 (about a factor of e, by chance). The cloud-top gravity of the gas giants is not too interesting here, but I suppose that the ...
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### How Does Black Hole Evaporation Look From the Inside?

Imagine you're inside a black hole event horizon. The curvature of spacetime is such that the direction towards the singularity becomes timelike, as reverse movement becomes literally impossible. How ...
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### Open problems in astronomy that an amateur (with a PhD in some other field) would have a chance of solving?

What are some open problems in astronomy that an amateur would have a chance of solving? Suppose the amateur has a PhD in some other field, owns a basic telescope, a set of filters, diffraction ...
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### Spectral analysis of AGN (velocity dispersion of galaxy absorption, doppler shifts)

I was wondering what parameters I need to know/measure to calculate the velocity dispersion of a galaxy, specifically an AGN. Also, I have spectra where there are blueshifted and redshifted ...
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### What is the distance between 2 cities? [closed]

Both Quito and Kampala lie on the Equator. The longitude of Quito is 82°30'W and that of Kampala is 37°30'E. What is the distance from Quito to Kampala? A) along the shortest surface path B) along a ...
429 views

### Is it possible to move a planet out of its orbit? At least a lighter planet?

As observed by many researches our sun will be exhausted in a distant future. So anyone thinks driving our planet (or any planet) closer to the sun for more light and heat is a solution for the life ...
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### Can we know the orbital planes of extraterrestrial planetary bodies?

Astronomers can tell if there are any exoplanets orbiting its parent star using but not limited to the following methods: Transit As an massive object usually a planet passing in front of a star ...
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### How long until the stars are no longer visible by the human eye due to light pollution?

I was curious to how long it will be until the stars are not able to be seen due to light pollution. I started wondering this after reading Yummie's Flash comic Knite.
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### How often are new astronomical objects (variable stars, supernovae, comets, etc) discovered by amateurs?

How often are new astronomical objects (variable stars, supernovae, comets, etc) discovered by amateurs? Where could one report new findings?
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### Stars in star clusters in SMC and LMC

Is there any catalog or any paper published in any journal that lists the stars discovered under whichever star cluster of the Small Magellanic Cloud (SMC) they belong to? There is one for Large ...
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### What will happen to life on Earth when the Andromeda and Milky Way galaxies collide?

It is said that the Andromeda and Milky Way galaxies are coming close to each other with a speed of approximately 400000 km/hour. They will be together in the next 4 billion years. What will happen ...
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### How many stars and galaxies can be seen by the naked eye?

How many of the luminous dots that we see naked are galaxies and not stars from our galaxy? I imagine that the majority of the luminous points that we see naked eye during the night, are actually ...
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### Where to obtain Tycho Brahe's data?

I would like to obtain Tycho Brahe's data on Mars. What would be an authoritative source? One source I could find is this page (the data is given as an Excel file) but I have no idea can that be ...
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### Weight of a celestial body

How do astronomers find out the correct weight of a planet even though there isn't any direct means to weigh them? What technique do they use? Just curious!
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### What would we find if we could travel 786 trillion light years in any direction

I've sometimes heard of galaxies that are millions or billions of light years away but if we could instantly travel 786 trillion light years in any direction, what are we likely to find? And what if ...
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### Is the sun too small to self-ignite?

I recently heard in a discussion that the sun is not massive enough to self-ignite via core-pressure. It simply has not enough mass to "generate" the gravitational force needed for that. The reason ...