# All Questions

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### Conversion between Astronomical Frames, ex. IRCF, FK5, FK4, etc…

I'm a little bit confused about reference frames, and I was wondering if someone could help clarify a few things? So let's say I have equatorial coordinates that refer to the mean equator and equinox ...
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### Where are we in an approximate timeline of the possibly habitable universe?

Our universe is supposedly 13+ billion years old and our Sun is a third generation star. It seems to me that we are now in a relatively young stage of the universe. How many generations of stars will ...
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### How do scientists name space objects?

I am curious that there are lots of celestial objects (planets, comets, stars, galaxies, etc.) in space. How do we name them?
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### Is there a ninth planet?

After Pluto's demotion as a planet, we have currently eight planets in our solar system. But Sun's gravitational pull can be felt well beyond Pluto, so is it possible to have a ninth planet beyond ...
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### Is this a wet moon?

Tonight around 12:20 AM I realized that the top part (instead of the side) of the moon was missing. I live at a country in the tropics. I took this picture with my phone so it isn't very good. ...
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### Where can I look up the 3D positions of the closest stars? [duplicate]

The problem: I want to simulate a travel from Earth to the closest 15-25 stars. Which is the fastest way to accomplish this? What i have: I currently have the distance between Earth and the nearby ...
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### I can't find Rigel on Tycho 2 catalogue

I'm trying to develop a planetarium using Tycho 2 catalogue. To read it I use the WCSTools. But I have a problem. On Wikipedia I have found that Rigel star has RA: 05h 14min 32,3s and Dec: -08º 12’ ...
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### Astrophysical “unitised” version of the Gravitational constant

This question relates formalising the gravitational constant, $G$, (which in S.I. units is usually quoted as $\sim6.67\times10^{-11}\,\mathrm{m}^{3}\,\mathrm{kg}^{-1}\,\mathrm{s}^{-2}$) in units which ...
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### What is a dead comet?

How is a Dead Comet different from the normal comet? How are they formed? And why is the Halloween asteroid 2015 TB145 called a dead comet?.
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### Gravitational Propulsion [closed]

I am not a physicist, in fact I am just a family doctor, so I beg of you to excuse me of anything I say that you may find outrageous :) But I came to this forum to see if anyone would be able to ...
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### What does oxygen on comet 67P/Churyumov-Gerasimenko mean?

Recently, the Rosetta mission found oxygen on the comet 67P/Churyumov-Gerasimenko. According to theories, oxygen should not be in the state in which it is on the comet. What are the previous theories ...
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### How long New Horizons will remain operational? [closed]

As of now the New Horizons probe is well beyond the orbit of Pluto, moving towards the Kuiper belt. In an article I read that New Horizons will eventually follow the path of Voyager probes to the ...
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### Which are the best American universities/colleges for observational astronomy? [closed]

I'm a French student and I'm planning to go to the United States for a graduate program in astronomy. When I will arrive in the U.S. I will begin by the first year of graduate. Then I will pursue ...
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### Linear limb darkening coefficient, u

I was wondering if anyone knew of any resources to understand the linear limb darkening coefficient, $u$. That is to say, how the $\theta$-dependent coefficient $u$ (or sometimes $b_{\nu}$) varies ...
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### Acquirable Raw Data in Amateur Astrophotography

What raw data can I possibly acquire from an 8" Classical Dobsonian Telescope, and a DSLR? Could anything eye-opening to amateur astronomers be computed or calculated first-hand with such equipment? ...
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### What makes small interferometers useful? Like NIRISS on JWST

NIRISS is an instrument on the James Webb Space Telescope. It has a "non-redundant aperture mask" which obviously covers most of the area of the sensor. It seems to be advantageous for high contrast ...
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### How gravity works in a black hole? [closed]

In astronomy class, we have to state how gravity work in the black hole? I know for one fact is that black hole is strong enough to stretch you thin enough like a noodle. Any ideas?
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In radio/microwave observations, I understand the beamsize is the response of the telescope to a point source - effectively, the telescope's resolution. Now, the Planck satellite (par exemple) ...
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### Is there any difference between rotation axis 90 degrees and 270 degrees? [closed]

Is there meaningful reason to distinguish 90 and 270 degree rotational axis?
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### How to disentangle a very distant star's relative velocity vs. redshift distance

We measure a star's relative velocity towards or away from us via its Doppler-shifted spectrum. This is also how we measure the distance of very distant stars: measuring the shifts in the spectrum ...
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### How to determine atomic number density of an element in a star based on equivalent width measurements

Given an equivalent width measurement $W$ of a spectral line of element $X$ and the effective temperature $T_{eff}$ of a star, how can you determine the atomic number density of $X$ in that star? ...
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### Best approximation for Sun's trajectory around galactic center?

What is the current best approximation for the path the Sun takes around the center of the Milky Way? I have found some information on the approximate position of the Milky Way's center, the speed of ...
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### Do boulders erode differently on asteroids than on the Moon?

If I understand it correctly, boulders on the Moon are only found near fresh craters, because micrometeorites erode them over time. Asteroids are believed to have formed sometimes even earlier than ...
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### Is Jupiter just a super earth with hydrogen atmosphere?

Often I see books which state that Jupiter has a rocky core, if it is true, does it originate from super earth with excessive collection of hydrogen?
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### Illusion of a lunar eclipse [closed]

A little over half a year ago, I think it was mid March 2015, I glanced out of my window at about 4 am, to see what appeared to be a very bright total lunar eclipse, as in, the moon was full and ...
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### A universal reference point [duplicate]

I would like to use a system of co-ordinates (x,y,z,t) based on a specific well known point. My original choice (the center of the universe in the big bang theory, Bigbang0), was wrong as the universe ...
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### What will happen if a black hole appears near our solar system?

We know that black hole possesses immense power and can destroy anything coming in front of it's path. If such a black hole appears near our solar system, are we going to survive? Is there any way not ...
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### Why does the Hertzsprung–Russell diagram's x-axis go from large temperatures to lower?

In my textbook, the H–R diagram’s y-axis is $\log(L/L_{\odot})$ and values are higher as we go higher on the scale, but the x-axis is $\log(T_\text{eff})$ and gets smaller as we proceed to the right. ...
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### How does one find the extinction coefficient of a particular galaxy?

I am doing photometry on a number of objects in a number of different galaxies. I need the extinction coefficients for these galaxies for various filters passes. Is there some database that displays ...
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### nasaworking on a way to travel faster than speed of light [closed]

even if they did how will time pass in that ship. Also that ship would require a infinite amount of energy to fight the drag.but what would provide the drag since in space there is nothing to resist?
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### Do the terrestrial planets form later than gas giants in our solar system?

Sorry I forgot where this statements come from, but I also remember the reason behind it is due to young Jupiter moves inwards and destroys the original super earth in inner solar system, and the ...
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### Why does the moon appear on cloudy night sky?

Now, I was looking the sky when I saw the Moon showing up in a sky completely cloudy, like this: But a little different. The clouds were doing an eye shape. What does explain that phenomenon? ...
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### What is in the brightest area of the night sky?

When I look up in the night sky, I assume the brightest area, commonly known as "The Milky Way", is the Galactic Center of our home galaxy. But then I stumbled upon this illustration, which seems ...
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### Are meteors and meteorites considered “Small Solar System Bodies”?

The difference between meteorites, meteors, and meteoroids is one of altitude relative to a celestial surface: in space, it's a meteoroid; in the atmosphere, it's a meteor; and on the surface, it's a ...
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### Planet-timer “device” from 1970s or 1980s possibly by Edmund Scientific

Many years ago (early 80s or late 70s), I bought a cardboard "device" which I think was called "Planet Timer" and I think was sold by Edmund Scientific. Does anyone have any information on this ...
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### Strength of gravity during the big bang?

I was watching a documentary on the big bang, one of the astronomers said that initially the four fundamental forces were combined as one, they then emerged to become: The strong and weak nuclear ...
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### Formation and capture of Mars' moons, Phobos and Deimos

Mars's moons have the appearance of captured asteroids. How could this capture have taken place. An asteroid in solar orbit would need to loose some momentum to be captured. The gas Giants can ...
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### Do orbital resonances always form naturally?

For example, if I throw two planets to orbit a star at random direction, would they form an orbital resonance?
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### How did Mars come to have a 24 hour 39 minute day?

Mercury rotates three times for every two revolutions around the Sun, apparently due to a gravitational resonance with the Sun.Venus takes about 225 days to rotate, and rotates in the opposite ...
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### How long does an over contact binary star system last?

I read recently about VFTS 352, an overcontact binary star system where both stars have roughly equal mass. All of the reports I've read (in mass-media type publications) have said that the system has ...
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### How do we know that light is redshifted/blueshifted and not the original light of a star/galaxy? [duplicate]

If a star/galaxy is moving towards us, then its light is blueshifted, and if it is moving away from us, then its light is redshifted. How do we exactly know that the color we are seeing is not part of ...
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### Brown Dwarf transcending past the sun with the naked eye [closed]

I seen with my naked eye in mid 2014 from Ca. right after sunrise a black spot in front of the Sun.I observed it for about a hour with my naked eye. Here is a picture that closely resembles what I ...
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### Volcano activity on moon

Are the dark grey areas on the moon formed from the last lava flows from volcanoes? And that is why there are hardly any craters in those dark grey areas because the lava has covered the old ...
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### What is the minimum distance from city that allow to see Milky Way plane? [closed]

The light pollution fades the starlight coming from the Sky and this dont let people to see the Milky Way disc. Is there any study about this?
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### Inclination in Kepler's laws

So, you can determine the location of an object in an orbit at any given time via Kepler's laws, but how do you determine the orbital inclination at any given point in time?
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### Is axial tilt critical for life?

According to this explanation at the Georgia State University website, Axis Tilt is Critical for Life . . . The Earth's spin axis is tilted 23.5° with respect to the ecliptic, giving ...
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### Does more ocean on an Earth analog produce a different rotation period?

Would an exoplanet that has more ocean than Earth rotate at a different speed as a result of this? Would the amount of water impact the weight, gravitational pull, and/or tidal forces and cause a ...
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### What is the temperature on surface of Pluto facing Sun?

According to wiki page, the mean temperature of Pluto is 44 degree K (-229 degree C). However, given that Pluto is tilted greatly and there is daylight for long periods on part of Pluto facing the Sun ...