# All Questions

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### Ramifications of black hole stellar system

Recently, I got around to seeing the movie Interstellar. In it, the characters of the movie visit a stellar system that appears to be built around a black hole instead of a star. On top of this, their ...
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### Can objects enter hydrostatic equillibrium through processes other than the influence of gravity?

Wouldn't a droplet of liquid (say water) floating around in space become spherical and "in hydrostatic equilibrium" due to surface tension but not gravity?
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### moonless night and lunar phase

How to define moonless night? There is no moon at all during some night? How to calculate and know whether the moon would appear during one night? If the lunar phase is full moon, is it possible ...
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### Is axial tilt direction correlated with semi-major axis direction?

Earth comes closest to the Sun every year around January 3. Winter solstice is at 21-22 December, merely some 12-13 days away. That means projection of Earth rotation axis onto the plane of its ...
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### What causes the bright white area in this photo of the earth?

Regarding the photo of the earth described here, I know that the green tinge on the left hand side is to do with the aurora borealis. What's causing the bright white light on the right hand side?
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### Is Zeta Reticuli within the Orion Arm?

My research has told me astronomers have labeled the galaxy arm that our system is located the Orion Arm but I have yet to find out if that also applies to Zeta Reticuli or not (not asking about ...
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### Appropriate battery for overnight viewing to drive telescope and GOTO?

I have a Plettstone 18" Dobsonian telescope with GOTO and clock drive that runs off a 12 volt cigarette lighter adapter. What is an appropriate battery to use to run this overnight while viewing all ...
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### Is there a term for stars without any planets?

Quite simply, is there any used term for stars that don't have any planets? While contemplating this and doing numerous searches to no avail, I think I found my own answer, but I'm asking here for ...
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### During what time of the year can Centaurus be seen from Tokyo?

During exactly what dates of the year can the Centaurus constellation be seen from Tokyo, Japan? And what is the ideal date for viewing it from Tokyo? I found on a website that it can been seen ...
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### Star System Formation questions

I'm making a game in which I'd like to randomly generate star systems. Which is cool. The trouble I'm having is working out exactly what limits I need to place on the generation. So far, the ...
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### Beta profile fit of Virgo cluster gas?

I'm looking for the parameters $r_c$, $\rho_0$ and $\beta$ in a $\beta$-profile fit of the Virgo cluster's ICM density. I just can't find a reference for it. Unlike for Coma (Abell 1656) where it's in ...
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### What is CMB radiation doing to the universe?

It is said that due to CMB radiation our universe has been expanding? Firstly what lead the universe to expand? What do scientists mean by dark energy? Will energy convert into matter?
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### Date and time system on moons

Supposedly, if humans were to establish a colony on one of the moons of a planet (such as gas giants in our own solar system), how could we possibly design date and time system? On Earth, we define ...
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### Visibility of Apollo 11 module

I wasn't around when man landed on the moon in 1969. When I see the moon, I always wonder, were people able to see the rocket? Yesterday, I looked at the moon in daylight and wondered again. My ...
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### Can solar luminosity & activity be predicted?

Can a star's luminosity and its activity, solar flares and sunspots, be predicted? If so, with what accuracy & precision?
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### What is frequency range?

Using the NED, you can search via frequency range corresponding to the selected pass band filter. I'm a beginner here and don't really understand. Here's the quote: NOTES: Objects with ...
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### What is the time/size/rigidity ratio for a space object to become mostly round?

In the answer here multiple comets are identified that do not form a single round body. A drop of water will form a round shape in the time it takes to free fall a couple of feet. All of the ...
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### Is it difficult to see DSO in your eyepiece?

I want to know if bringing the image of a DSO in eyepiece generally represents a problem for beginners in astronomy.
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### Does mass create space?

Imagine two cubes each with the side 1 light year. One of the cubes is empty of any matter. The other cube contains a massive star. Does the cube which contains the massive star have a larger volume ...
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### Metallicity: What are the metallicity values of various galaxies?

What are the various values of metallicity of various known galaxies, like Milky Way, Large Magellanic Cloud, Small Magellanic Cloud, Andromeda and so on?
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### If an object with mass were to somehow go the speed of light, would it destroy the whole universe?

Would an object with mass traveling the speed of light destroy the whole universe because it would have infinite energy / mass? According to ...
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### How many stars are visible to naked eyes around Equator area?

In the best sky conditions, we can see about 44,000 stars in the sky. But what if I am located around Equator area? How many stars I can see? From what I know, the number of stars I can see should ...
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### Term for a momentary geometric pattern formed by astronomical objects

Few days back, the Pleiades, the Sun and the Moon were forming an almost perfect equilateral triangle. Is there a term that describes such momentary geometrical patterns? ...
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### How can pre-main sequence stars radiate more energy than main-sequence stars?

How can a pre-main sequence star radiate more energy by gravitational contraction than a main-sequence star can by hydrogen fusion?
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### Is it dark inside a black hole?

Assuming you could be standing inside a black hole, would it be light or dark around you?
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### Choosing a diffraction grating

I am interested in doing some solar spectroscopy on my own for fun. How do I go about choosing the appropriate diffraction grating?
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### Satellite/Planetary Orbits

All planetary orbits contain 5 unusually stable points. These points are particularly important because they allow man-made satellites to orbit the Sun with a period equal to that of Earth’s. 3 of ...
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### Black dwarf binary systems

I know black dwarf stars do not exist yet, and that they are what white dwarfs end up after a long time. The question is really simple: would it be possible to have a binary system in which one of the ...
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### Question about the formation of elements

So, elements such as iron, gold, etc. are formed from different types of supernovas, whether it's type 1A or 2. My question is, is it possible that there are elements that are formed that we never ...
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### What is the speed of light relative to (in space)?

From what I understand the universe is expanding faster than the speed of light and accelerating so that it's possible that a given galaxy: $A$ will no longer be visible to another given galaxy: $B$. ...
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### What would the sky have looked like when galaxies first started to form?

If I stood on a theoretical earth at the time that galaxies were just starting to form, what would the sky have looked like? Due to the smaller size of the universe would it have been densely packed ...
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### if the big bang only expanded the universe when and how did it originate? [duplicate]

If the big bang expanded the universe from a singularity point, that means that there was matter before, so where and how did matter form for the first time if it's even possible to know such a thing? ...
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### If oxygen was abundant in Neptune, would there be combustion?

Since Neptune/Uranus have high percentages of methane, wouldn't it be highly likely that there will be combustion (triggered by the lightning storms or any other factor) if oxygen was abundant? And ...
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### If the tilt of the Earth changed, would the tropics latitude change too? [closed]

I wanted to know if the tilt of the earth were changed to 30 degrees would the tropics of cancer and Capricorn also both change to 30 degrees?
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### the most accurate system that can show the positions of planets at my birthday [closed]

My birthday : 4 December 1982 If you have such astronomical calculator on your computer please send me the result ! Alternatively if you know an online astronomical service for my purpose please ...
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### How do kepler orbits account for planetary migration?

This article got me thinking if kepler orbits explain how a planet moves in a solar system how can a planet migrate as explained in the article. At some point don't the kepler orbits must need some ...
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### brown dwarfs and planets

As far as I know, a brown dwarf is a 'star' whose core never underwent a fusion reaction, so it never became a star. So I was wondering if, appart from orbiting a star, is there any difference between ...
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### Why is there so much methane in space?

In school I learned that methane is organic matter and that it is a possible product of crude oil refinement. However, recently I read that Uranus has huge methane storms and the Saturn moon Titan ...
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### How long does it take Dawn to orbit Ceres?

I haven´t been able to find the orbit time of Dawn around Ceres. Do you know how long it takes?
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### How much light does Jupiter project onto the surface of Ganymede?

I suppose the answer would be a range as the Jupiter-facing side of Ganymede passed from Jupiter's light side to its shadow side. I'd also like to know how much light the sun projects onto the surface ...
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### How can a galaxy in-between our view and the galaxy behind it have a 'lensing effect'?

In this article, the author writes: This galaxy is so distant that it would have been invisible without the gravitational lensing effects of a large galaxy cluster called Abell 1689, located ...
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### What does it mean to say 'space exists?'

From another question I posted, I learned that not only was matter created from the Big Bang, but more importantly, space itself. What does it mean for space to be created? Does it exist in the same ...
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### Is the universe simply a mass of atoms in 'void'; what does it look like?

I've always been stumped with the question of what lies beyond the universe, and I've come to the firm conclusion - void (i.e. completely empty). Does it make sense then to think of the universe as a ...
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### Wher can I find a list of blueshifted regions in the Milky Way?

It would be nice to get a relation between the blueshifted regions and the distance to earth. I'm searching especially for objects in other galactic arms.
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### How do you find the altitude of the Sun if you are on the Moon?

The question is: If you stand on the equator of the Moon, at midday your position occurs when the Moon is located at the line of the node. What is the altitude of the sun at that moment? ...
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### Gravitational tidal force problem

if we have spherical mass held by its self-gravity, there will be a limit to distance - let's say it is $r$ - that the center of this body may approach a much more massive body (lets we call $M$ ...
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### Visibility of earth from moon during day-time of moon

Inspired by this question. I am curious whether earth, besides being nearly fixed on one place on the moon's sky, is it visible during the day-time on moon too? My understanding is that earth should ...
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### speed of light measurement

While searching for different methods of speed of light measurement, i came across one of the method of fizeau discussed below which i cannot fully understand. In short,in Fizeau’s apparatus, a beam ...
In a model of the solar system, given the Sun is at the point $(0, 0, 0)$, an given the six orbital elements for each object in orbit ($a$, $\epsilon$, $i$, $\Omega$, $\omega$, $M_0$), how can I ...