# All Questions

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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?
587 views

### why does venus flick?

I was watching Venus with the naked eye yesterday at about 7 pm and I noticed that it was flickering, almost like a star. I have always learned that planets don't flicker to the naked eye, only stars ...
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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 ...
85 views

### How was all the matter curled up inside a singularity during big bang ?

If the singularity had infinite mass, temperature and density, then it should curve space and time but there was no space-time before big bang. So where did the singularity come to existence without ...
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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 ...
108 views

### Planets orbiting Alpha Centauri

I read that a few years ago some planets were discovered orbiting Alpha Centauri. Has there been any more information since then concerning the possibility of life there? This is the closest star ...
104 views

### 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?
71 views

### 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 ...
118 views

### 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 ...
168 views

### 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 ...
191 views

### Can the Universe be spatially closed and expand forever?

In the lambda-CDM model, the Universe is spatially flat, and will expand forever. Is possible that a spatially closed Universe expands forever?
117 views

### Equations for coordinates of solar system objects

I would like to write a program that visualizes the solar system. To do this, I would need equations for calculating the coordinates of each solar system object at a given time. Where could I obtain ...
41 views

### Are there any works discussing planetary bodies being forms of life?

I'm searching for works or individuals that consider and discuss the idea of planetary bodies being considered stand alone living creatures, rather than objects either capable or incapable of ...
71 views

### How much do the mascons on the moon affect surface gravity?

The gravity anomalies on the moon (generally accepted to be caused by mascons) are powerful enough to affect the orbit of satellites. I'm trying to determine how much effect they would have on a ...
63 views

### Source of high energy cosmic particles

Earth receives shower of both solar and cosmic radiations every seconds. The Sun put up a heliosphere around the solar system and thus foreign high energy charged particles could not penetrate easily. ...
92 views

### Can you assume atmosphere height for the purpose of surface pressure calculation?

Given that by definition of scale height an atmosphere thins by a factor of 1/e^x where x is elevation in terms of scale height multiples (See the table here: Definition of Scale Height), can we ...
50 views

### Is there any astronomical phenomena that could emit strong radio waves with multiples of a discrete frequency?

In the New Scientist article Is this ET? Mystery of strange radio bursts from space, it is reported that several times since 2001, astronomers have detected fast radio bursts that seem to have a ...
177 views

### Is it certain that dark matter consists of particles? (And not just curved space)

The main idea about dark matter today seems to be supersymmetry. That there exists a set of yet undiscovered fundamental particles which (in a mathematically most convenient way) mirror the particles ...
108 views

### Collision of asteroid and gaseous planet - what would happen

What happens when asteroids (or other small bodies) "collide" with a gas planet? In my head it would either go through it or just stay "inside" it due to the strong gravity. I tend to believe in the ...
38 views

### Orbital Elements Mars near June 2014

do you know any website in which I could obtain orbital elements of planets at some date? For instance, I'm now needing the orbital elements of Mars around June, 2014. Thanks!
43 views

### SDSS: Inclination of a Field?

I am working with the Sloan Digital Sky Survey CasJob service. I am trying to determine the ellipticity of a galaxy using the stokes parameters $U$ and $Q$ from which I can deduce $e$ and $\phi$. But ...
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### Is there a publicly available Gliese Star List

Is there a publicly available list of the Gliese catalogue of nearby stars with their constellations? or a Gliese to Hipparcos List ?
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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 ...
415 views

### Why aren't brown dwarfs the dark matter?

There seems to be not enough matter to account for the fact that the speed of some stars located far from the Galaxy center is almost the same speed as those stars found nearer to the center of the ...
165 views

### How do we know the universe's expansion is speeding up?

Please forgive my ignorance, I am not an astronomer, just an interested layman. The further away a galaxy is from us, the faster it is moving away from us. But the galaxies we see exist in 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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### What happens when star spins too fast?

Some stars such as a neutron star can spin very fast around 600 times a second, wouldn't the star be ripped apart? Although the gravitational pull is very strong but gravity is the weakest of all ...
254 views

### Does the mass of the observable universe ever change?

First do we have anyway to even estimate the mass of the entire observable universe? And then is there any data that shows mass being gained or lost? Would we ever know if someone was playing with ...
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### Life planets orbiting black-holes. Can/Do they really exist?

So, I watched Interstellar and if you watched it too you know that there's a planet orbiting a black-hole, they call it Miller's Planet. According to the movie, every hour on Miller's Planet is ...
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### Why is the Boomerang Nebula colder than the CMB?

An earlier answer on temperature mentioned that the temp of the CMB is 2.4K and the temp of the Boomerang nebula as 1K. How did the nebula cool faster than the CMB?
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### Can we observe what objects exist at the L3 positiion of planets of our solar system?

From what I understand Earth's L3 is obscured by the Sun, so is that true for our viewpoint of the other planets? Or, are there times when other planets are on the other side of the Sun from Earth and ...
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### Binary stars system ultimate fate

I read an article mentioning that when two stars orbiting each other they'll produce gravitational waves that can carry away energy into space. These phenomenon increases the speed of the two orbiting ...
86 views

### What could be the utmost lowest temperature in the universe/multiverse?

What could be the utmost lowest temperature in the universe/multiverse?
26 views

### Can ground based telescopes use a starshade in space?

1) Could a starshade in orbit be used by ground based telescopes? If so, what kind of orbit should it have? 2) Could the same starshade be used by two different space telescopes, or does the ...
325 views

### death of a red dwarf star / minimum mass needed for a white dwarf?

OK, first, I know there's a variety of sizes and types of red dwarf stars and the universe is too young for any of them to have reached the end of their main sequence phase yet, so it's all ...
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### Infrared telescopes, magnitude and observations

Currently 22-23 magnitude could be the limit to make a spectrum for ground based 10m class telescopes, 21-22 magnitude may be easy for them. 4m class telescopes could possibly handle 20 magnitude, I ...
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### how to tell an optical spectrum is featureless or just with a low S/N?

A featureless spectrum and a spectrum low S/N are very similar. Is there a way to tell them?
318 views

### what is a Friedmann model?

Can you explain what is a Friedmann model to a layman? And also give some examples of Friedmann models, specially I would like to know if the lambda-CDM model is considered a Friedmann model.
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### Is the Oort Cloud actually opaque, or is the “cloud” used euphemistically because minor planets inside of it are too dim to be seen?

I did read several of the Oort Cloud questions/answers which I found very helpful and instructive, but this question still persists for me: Is the Oort Cloud actually opaque, or is the "cloud" used ...
358 views

### Is there any practical use for astronomy?

Although astronomy is very cool and the things we are learning are awesome, is there really any practical use to knowing the things we know about the universe? Do other fields of science draw from ...
108 views

### How can I calculate how the debris of an object ripped apart at the Roche limit will spread out?

Let's say I have a moon orbiting a planet at a distance $d$. Eventually, $d \leq d_R$, where $d_R$ is the Roche limit of the moon-planet system. I can figure out the mass of both bodies by experiment, ...
357 views

### Leaving the Milky Way

If we had a hypothetical spacecraft, would it be possible to exit our galaxy, wait for some time and enter back into another section? Will this method be more efficient that a more traditional flight ...
144 views

### Why are distant objects observed in the near infrared?

I was reading an article that explains why JWST is a successor to Hubble and not a replacement for Hubble. They explained that Hubble's science pushed astronomers to look at longer wavelength. And ...
120 views

### 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 ...
186 views

### What is the minimum size of a ball of gas to become a star?

I know there are two criteria to meet in order for nuclear fusion to occurs. High temperature (many times temperature at Sun's core) High pressure (protons are very close to each other) [Goal] ...
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### Is it possible to use the stars to determine the passage of time?

I'm writing a science fiction short story which involves a group of people being in suspended animation for a very long period of time, on the order of thousands of years. My question is, would an ...
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### Around what apparent magnitude can the naked eye observe an object during full moon

For a very rough guideline using healthy/corrected eyes adjusted to the dark, around how bright should an object be to expect it to be visible?