# All Questions

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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 device?...
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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 ...
106 views

### 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 craters?...
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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?
206 views

### 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 ...
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### Which stars have been named after astronomers?

Most apparent stars have ancient names. But some of the newer (since 200 or so years) discoveries have been given the name of some prominent astronomer. Kapteyn's star is one example, and there are ...
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### White dwarf's impact on orbiting bodies

Recently the Kepler telescope in its study of white dwarfs detected the first planetary object transiting a white dwarf in the data from the K2 mission. It was consistent with earlier theories' ...
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### Subterranean Oceans On Other Planets/Planetoids: How Do Astronomers Deduce This

Recently I have been looking into planetoids in our asteroid belt and I have found one that caught my interest, Ceres. One of the main points that was said about it was that it had a subterranean ...
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### Recommendation for learning about stellar astrophysics

I would like to know which are the best books to learn about stellar astrophysics at (just) graduate level. I have a basic formation in general astrophysics but I'm interested in learning about ...
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### classification of the Kozai mechanism

As Wikipedia says, In celestial mechanics, the Kozai mechanism, or the Lidov–Kozai mechanism, is a perturbation of the orbit of a satellite by the gravity of another body orbiting farther out, ...
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### Annual path polar chart for a star

I've often come across sun path charts like this (Wikimedia Commons) that show the position of the sun at any point of the year, at any time of day, for a specific location (or a set of locations), on ...
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### Could an asteroid knock the moon out of its orbit?

As describe in this CNN article, an asteroid is going to pass near the Earth on Halloween. The article says that As it misses Earth by about 300,000 miles (slightly farther away than the moon), ...
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### What is meant by matter distribution?

Frustratingly, I find this could be a very simplistic question and may leave me feeling a little stupid for asking it. But I have to ask this. My lecturer keeps refering to "matter distributions" for ...
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### Uncertainty in the FWHM (IRAF)

I measured the FWHM (Full Width at Half Maximum) of several emission lines using SPLOT in IRAF, and now need to calculate the uncertainty. How can I do that?
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### Is there a database for stars? [duplicate]

I'm interested, is there any database of stars which I could browse on the internet? It would be good, because I could read their parameters, features and maybe find a picture about it. Thanks!
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### Is a supernova's core temperature absolute zero just before collapse?

I thought a supernova's core temperature was absolute zero just before it collapsed, as it has run out of all nuclear and thermal energy, but I haven't been able to confirm this online anywhere and I ...
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### How massive does a main sequence star need to be to go type 1 supernova?

We know the mass a white dwarf needs to be. That's well defined by the Chandrasekhar limit, but before a main sequence star turns into a white dwarf it tends to lose a fair bit of its matter in a ...
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### When the sun explodes, will some of the planets in the Solar System survive and become rogue planets?

Say if a large enough star, that has a number of planets, were to explode in a supernova: Would any of the planets survive? Would they become rogue planets?
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### Why can't this be the simple (and obvious) explanation for the dimming of KIC 8462852?

Couldn't it be just a relatively large object, anywhere in the interstellar space between the star and Earth? I mean, look out the window at a far away car or a tree, then stretch out your hand and ...
117 views

### How do rogue planets orbit around stars in other planetary systems?

I got some interesting answers for What would happen if a rogue planet hit one of the planets in our Solar System? But I have seen some documentaries that state that rogue planets from other ...
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### Acceleration in Galaxies Collision

In the far future the Milky Way and Andromeda will collide. As far I know direct collision between large dense objects (black holes, stars, planets, etc.) is unlikely due to the relative "low density" ...
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### What would happen if a rogue planet hit one of the planets in our Solar System?

As their are millions of rogue planets in the Milky Way, what would happen if one hit a planet in the Solar System. For example, if the rogue planet hit Pluto, would Pluto fall in to the Sun due to ...
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### mountains higher than atmosphere

Is it theoretically possible that planets exist with mountains so high that their peaks overtop the planets atmosphere? And which physical laws are relevant for this question? I'm just curious. Thanks ...
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### Does Mars contain more iron than the Earth?

Is the reason Mars is red because its surface contains a lot of iron? (When dirt is red on Earth, it is sometimes caused by a high amount of iron). If so, does Mars contain more iron than the earth?
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### What would night sky look like if Earth was made of antimatter

Let's assume that Earth in its current state is suddenly replaced with the Earth completely identical, but made entirely of antimatter. Ignoring meteorites and asteroids which would cause mass ...
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### Is the time lapse considered when estimating the age of the universe?

We say that our universe is 13.7 billion years ago. During the big bang, it doubled at least 90 times in trillionth of a second (as given here), and other topological statements. The question is ...
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### What were the 2 satellites I saw this morning?

This morning at 6:03am Israel time (3:03 UTC) I saw, simultaneously, what appeared to be 2 satellites streaking across the sky directly overhead. If I remember correctly, they were both coming from NW ...
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### How astronomers distinguishes between natural and artificial signals coming from outer space?

How astronomers really distinguishes between the natural and artificial signals? From time to time astronomers detects many signals from outer space and SETI is always trying to find signals that ...
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### Tidal lock of earth and moon

As the Moon is tidally locked to Earth, that means, from Earth we can only ever see one side of the moon. Can we see all the sides of the Earth, from the moon?
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### How does one add false colour to a fits image

I have an exposure of a star field with a small galaxy located near the centre. It is of course a greyscale image. I would like to add colours (realistic) to this image for aesthetic purposes. What ...
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### Theoretically, what is the biggest optical telescope that may exist?

Recently, I read yet another news about E-ELT. It will have 39.3-metre-diameter segmented primary mirror. And I was interested in the next question: Theoretically, what size of the primary mirror (...
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### Is there any other theory, apart from the Big Bang paradigm, which describes the birth of universe? [closed]

The Big Bang theory is the approved theory of the "birth" of Universe. Are there any other theories which can explain how our Universe came into existence?
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### Is antimatter present on Earth?

As we all know, antimatter is present across all of space. Is it also present on Earth? If it is present on Earth then by the interaction of matter and antimatter, why don't we feel the energy around ...

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