# All Questions

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### Plot an AltAz grid over a square grid of RADec points

first post here. As I'm new, StackExchange won't let create or use the wcsaxes tag. wcsaxes looks like the most appropriate tool for the job, but astropy is closely related. I think the title says ...
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### The Blackhole “Creator of Stars” [on hold]

I have thought for some time on how Blackholes and Neutron stars behave and interact in the nature of space, Now I know we have made some theory's and are still in the process of observation, we ...
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### Stellar mass limits for Neutron Star and Black Holes

Don't hate on me if I am asking a very basic and straightforward thing. I have a few questions about black holes and neutron stars. What is the mass range (in terms of solar masses) for a main ...
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### How much time does the ISS take to repeat its orbit?

I used to go to my roof to see the ISS, but it is not always visible. Then it appears again but does it appear with the exact same orbit as I saw before? Thanks!
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### Is there Kuiper belt/Oort cloud like structure in gas giants?

I know gas giants have moons, just like star have planets, how about kuiper belts or Oort Cloud? Is there any corresponding structure in gas giants? If not, why don't they have?
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### What does the Sun's orbit within the Solar System look like?

Everything in the Solar System revolves around the "barycenter": the overall center of mass. This barycenter is not in the center of the Sun. Some articles and essays I've read go so far as to suggest ...
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### Pinhole Projector: Can I use a specific solar optical eye piece to focus the Transit of Mercury?

The title pretty much explains this one. Can I use a specific solar optical eye piece, or other optical device, in conjunction with the pinhole projector method to focus the Transit of Mercury? ...
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### Can I use an array of inexpensive cameras as an alternative to a telescope?

The link below describes how an array of inexpensive cameras can create very detailed images. Would this work for astronomy? https://graphics.stanford.edu/papers/CameraArray/
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### What is the equation of state for a relativistic fluid/gas?

say we have a relativistic fluid/gas, as we have in some astrophyical systems. now let us write: $e$ - energy density in the fluid's rest frame. $P$ - pressure in the fluid's rest frame. $n$ - ...
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### Does this video catch an Eta Aquarid - Earth skimming meteor?

I did a time-lapse animation looking towards the sunrise from Sydney, Australia on 25th of April. You can see it here around 1m 25s in (that link should jump to just before it appears very near where ...
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### How big will Apophis appear?

How big will Apophis appear in the sky at its closest point of approach in 2029? Will it compare to the moon? How long will it linger as it passes?
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### Why does Titan have lower surface gravity than the Moon when Titan is more massive?

Reading on Wikipedia I saw that Titan is 80% more massive than the earth's moon but has only 85% the surface gravity. Why is this?
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### Is a planetary system star's referred to as their sun?

It's my understanding that our Sun (uppercase) is used to refer to our sun/star, because it is The Sun. Technical name is Sol, hence the Solar System. Even the tag (lowercase sun) on this post has the ...
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### Pinhole projector for the Transit of Mercury

Very quick and simple one today. What would be the best/optimal pinhole size for a pinhole projector to observe the transit of Mercury on May 9th? I want to get the optimum between resolution and ...
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### What is the possibility for everyone on earth get sucked into laboratory created black hole? [duplicate]

Assuming that we have created a small scale black hole in earth laboratory, now how big is the chance that we all get sucked into it?
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### V838 Monocerotis Supernova images morphed into nice video, but why so few original images?

This NYTimes video shows what I think is a series of real Hubble images which have been "morphed" artistically to appear to be continuously expanding. (also see The V838 Monocerotis Star Still Has ...
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### Calculate right ascension in Zenith at this moment in my location

I've been searching on Internet about how to calculate which RA is in zenith at a given location in a given time but I haven't find anything (or maybe I don't know how to search). Using my star ...
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### Why does shell fusion produce more energy than core fusion?

Stars go from the main sequence phase to the red giant branch due to the depletion of hydrogen in the core. As a result, the star contracts and shell hydrogen fusion begins, which apparently produces ...
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### Why are certain elements so common?

I understand why hydrogen and helium are the most common elements in the universe. I also understand iron, because that's where stellar fusion stops. But why are (specifically) oxygen, carbon and neon ...
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### Are there any electrons inside the sun / a star?

Like the question says, are there electrons inside an active star, or has all the matter been so thoroughly ionized / plasmarized that the electrons are long gone? I ask because it would make sense ...
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### A good place to start? [duplicate]

I am a high school student (going into 11th grade next year), who will be taking an introduction to astronomy and astrophysics as part of my core curriculum. As such, I would like to get a head start ...
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### Evidence of CMB redshift

Are there any known spectral lines shifted by ~1100? If not, then how certain is mainstream that the CMB has a redshift of ~1100? All I see is a blackbody radiation curve void of spectral lines.
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### Watching the Mercury transit with improvised devices

I have learned that it is not possible to watch the upcoming Mercury transit with the plain eye (using special filter glasses). Is it possible to watch the transit with improvised devices (like a ...
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### Could there be a brown dwarf in our solar system? [duplicate]

Is it possible that a brown dwarf object could be orbiting our star and undetected so far by wise surveys?
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### Can you see city lights on the Moon from Earth?

This is the opposite of another question. That question is about whether you could see cities on Earth if you were standing on the Moon. Let's there are cities on the Moon and you're standing on the ...
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### Seeing a galaxy (quasar) greater than 46.6 billion light years away

Assuming the Big Bang was 13.8 Billion Years ago: Is it possible to observe a Galaxy's redshift showing distances slightly greater than that, like 48 Billion Light Years away? I understand that in a ...
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### Tunnel vision while viewing through a reflector

I have a Celestron astromaster130 eq. While viewing through its eyepiece, or using a smartphone camera for photography purpose there is always a definitive no light region( it is circular in ...
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### What is the volume of the universe?

Of course it is not exactly known how big the universe is, but I thougt that the universe is about 100 billion lightyears in diameter. But if that is true can you also make an estimation of the volume ...
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### How does unmanned probe avoid the (gravity pull of) stars, planets, comets and other gravity source? [migrated]

Refer to the ambitious probe sent by Yuri Milner, Stephen Hawking and Mark Zuckerberg to Alpha Centauri: Yuri Milner is spending \$100 million on a probe that could travel to Alpha Centauri ...
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### What does “EW(Hα)” mean?

I came across a website saying that classical T Tauris have an "EW(Hα) > 5 angstroms". Does anybody know what "EW" means? Thanks.
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### Are we center of universe? [duplicate]

So I just learned that CMB redshift is 1100 regardless where we look (up down left right). According to Hubble's Law that makes it around 46 billion light years away, making it the farthest matter ...
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### Locations of farthest matter

Regarding matter that has the highest redshifts, do we see such matter in every general direction we look (relative to Earth: up down left right front back)?
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### What is the last nuclear reaction in a binary system before supernova?

I understand that binary star systems may cause type Ia supernovae. I have a question regarding supernova explosion in a binary system. What is the last nuclear reaction before massive explosion? I ...
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### Why do the gas giants in the Solar System have comparatively large orbits compared to the inner planets?

Ever since I observed the depictions of the Solar System, I was obsessed with the question of why the gas giants (outer planets) have very large orbits, compared to the planets that are closer to the ...
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### Is it possible that Titan is a kuiper object captured by Saturn?

I think Titan may be just captured by Saturn, not formed with Saturn together, because: It has so much nitrogen and methane, which is similar to Pluto and Triton Except Titan, other moons of Saturn ...
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### Jupiter appearing odd through a 6" reflector

Recently I have been trying to get a good look at Jupiter through my 6" Orion reflector, but the image seems to always come out as an oblong white streak. I've tried changing the lenses I'm using, but ...
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### Were there any images of a transitary event of Jupiter or Saturn as imaged by a deep probe mission

I'm quite certain that there isn't any actual images of a transitory event of Jupiter or Saturn across the solar disk from say e.g.,s the Voyager probe, Pioneer 10/11 or even recent New Horizons ...
124 views

### What Makes Stars Hot?

Simple question, but can't seem to find the answer anywhere. It can't be nuclear fusion because nuclear fusion occurs as a result of the heat. And it can't be because of gravity because it's believed ...
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### Three-torus model of the universe

I want to ask a question about the Three-torus model of the universe, as described in wikipedia: https://en.wikipedia.org/wiki/Three-torus_model_of_the_universe "is a proposed model describing the ...
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### Cosmological redshift and comparing past galaxy sizes

If you were to divide the present-day universe into cubes with sides 10 million light-years long, each cube would contain, on average, about one galaxy similar in size to the Milky Way. Now suppose ...
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### Do other stars have Oort clouds? [duplicate]

Stars have in the past passed within 1 light year from the Sun, and will do so in the future too. If they have Oort clouds, would there not be interactions between their Oort cloud objects and the ...
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### Question regarding the Milky Way when calculating galactic space velocities for galaxies

I have been calculating galaxy space velocities (where proper motions are known) in order to measure their orbits of the Milky Way using the method proposed in the appendix of ...
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### How to form Copper from Calcium in a supernova explosion?

What are the reasonable chain of reactions to form copper (63, 29) from ca(40, 20) during supernova explosion? And how it will happen? I do not understand the theory behind it. I thought that the ...
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### How do I see DSO's in my telescope? [duplicate]

I just bought a new telescope. I tried it out, and I even woke up at 3am when the moon set so there was light pollution. I have an 8 inch dobsonian telescope with a focal length of 1200 mm. For some ...
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### How long would it take to reach the edge of the reachable universe?

How long would it take to reach the current edge of the reachable portion of the universe, with the following bounds in mind: We figure out a way build a space ship to provide a constant 1 G ...
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### Triple stars with retrograde orbits

Where can I find the observed frequency of triple star systems where the outer star is in a retrograde orbit?
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### How do I see more than just points in the sky?

I just bought a new telescope with these specifications: Aperture: 203 mm Focal Length: 1200 mm F/ratio: f/5.9 I usually use a 28 mm eyepiece, giving me about 42.5x magnification, but I also have ...
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### Coordinates reduction python

How can I calculate position (alt, az) of star for observer at some station (longitude, latitude) on specific date and time? I need full coordinates reduction with all elements included in calculation ...