# All Questions

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### Finding Mass of Star with only Luminosity

Estimate the mass of the star given this formula: $L/L_\mathrm{sun} = (M/M_\mathrm{sun})^{3.5}$ Given $L= 2.752\times10^{28}\,\mathrm{W}$, how do I find the Mass of the star? Thanks for any help.
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### How accurately can you tell the time using a photo of the stars?

If I were to go out on a clear night, in an area with low light pollution, and take a photo of the stars, could an expert analyze the photo and figure out what date the photo is from? We can assume a ...
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### Need Simple equation for Rise, Transit, and Set time

I've been looking, unsuccessfully, for hours for a simple set of equations: Input: RA and Dec of an object Observers Lat and Lng Current Time Output: Rise Time Transit Time Set Time (and, ...
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### How high does light pollution reach into the sky?

I want to know how high does light pollution typically reach into the sky STRAIGHT UP? Has anyone ever researched this because I wonder if being at 10000ft elevation would reduce the amount of light ...
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### Question on Equatorial and Galactic coordinate systems

I'm currently working with proper motions and have needed to convert my galactic longitude and latitude into right ascension and declination (ie from galactic to equatorial coordinates). This is fine ...
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### Why do most meteors vanish just before hitting the ground?

Many times we see in the sky that most of the meteor shower trails vanish when they are about to strike the earth several feet above the ground. Why does this happen? They could strike the earth's ...
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### Retrograde motion of planets: reason and time?

I am a beginner. I'd like to understand how planets (except Sun and Moon) exhibit retrograde motion. When does the retrograde motion start for a planet (eg Mars) and how long (time limit) planets ...
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### Is Io's orbit or rotation affected by its volcanism?

The rotations of comets and asteroids are affected by outgassing volatilities. Io is very volcanicly active. Does it give Io a varying orbit and a slow rotation? Tidal forces should take longer than ...
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### Can the expansion of spacetime be directly measured with laser interferometry (like GW can)

LIGO has a mind boggling sensitivity. What would it take to directly measure the expansion of spacetime, along the laser beam? I suppose it could be done at interplanetary scale.
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### The relation between the light of full moon and the distance between the sun and the earth

If we want the full moon to be 2 times more bright,how we should change the distance between the sun and the earth? Thanks for your help.
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### What makes the Moon and Venus shine?

Is there some substance on Venus or some kind of material, because neither bodies have any source of light.
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### VLT interferometry vs E-ELT?

If the VLT (very large telescope) can use interferomerty to act as a 200 meter mirror, then why are they trying to build the 39 meter E-ELT? What advantage does the E-ELT have, if the VLT can act as a ...
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### What would be the apparent magnitude of Betelgeuse if it were as close to Earth as Sirius?

How large and bright would Betelgeuse appear if it were as close to Earth as Sirius, before and after it goes supernova?
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### If a white dwarf collides with a giant star, could it create a TZO?

Thorne–Żytkow objects (TZOs) form from collisions between neutron stars and main sequence or giant stars. Ultimately, the neutron star becomes the "core" of the giant star. However, could this also ...
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### Term for altitude of the sun?

The sun travels in an arc across the sky. Where I live, during the summer the arc rises higher, but in the winter the arc is lower. Once might speak of highest altitude or elevation the sun reaches ...
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### Far side of the moon question

Do all / most / any other moons orbiting a planet synchronize their rotation so as to become tidally locked with it, or is the earth a special case?
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### How is it possible that the CMB approaches the earth from all directions?

I presume that the photons from the CMB approach the earth from all directions, otherwise we couldn't detect them with a picture where it is present everywhere in the universe with a tiny anisotropy. ...
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### Would a Einstein–Rosen bridge change size and/or position in an expanding Universe?

I appreciate that a Einstein–Rosen bridge has never been observed but since there are some valid theories in General Relativity I thought I'd ask this. Would the start and end point of a ...
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### How common are Stars that have no orbiting planets? [duplicate]

How common are Stars that have no orbiting planets compared to Stars that do?
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### Is the earth bombarded equally in all directions by neutrinos?

Perhaps it is hard to known for sure because neutrinos are very difficult to detect, although they do go through the earth in very large numbers. But are they passing through the earth equally from ...
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### Explanation for the first spinning neutron star detected in the Andromeda galaxy?

A new class of Neutron stars has been found in the Andromeda galaxy (M31), This is the first time a Spinning Neutron star has ever been detected by astronomers in M31. The article states- “pulsars” ...
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### If Venus had moon before and it fell back to Venus, why don't I see a unique, very big crater?

Does lack of a very big crater support the idea that Venus never had big moons before? If not, why can't I find a very big crater from the moon impact?
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### If “9 th planet” is ejected by Jupiter or Saturn, why does it have a very far perihelion?

If the "9 th planet" is ejected by Jupiter or Saturn, I think the perihelion should be near Jupiter and Saturn, but now the predicted orbit is very far away from Netpune, why would that happen?
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### How do we know that there is no border at the end of “infinite” space? [duplicate]

It has been suggested that space and beyond is infinite, but admittedly the same hypothesis was made by virtue of the fact that it is physically impossible to prove otherwise. How do we know that ...
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### Can dark matter be found in the shape of planets, galaxies etc.?

If dark matter has gravity just like normal matter, does that mean it can also form planets, solar systems and so on? Any answer will be appreciated.
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### Create heatmap from significance

I am working on my project in astrophysics and I would like to create my heatmap from the significance which is obtained by the gaussian fitting my histogram. I get this map : First picture : ...
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### Can you see the stars when it is trickling?

I am writing a book with the following scene in one chapter: It is trickling and my protagonists are outside looking into the night sky, looking to the stars. Reviewing the scene I am wondering: Is ...
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### Which class of objects in Solar System carries more mass?

Could you help me sorting this list in terms of total mass carried by these classes of objects? The star (Sun) - it's very big but only one. The planets (incl. dwarf planets). Certainly beaten by ...
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### Two body orbit of equal masses

Given two bodies of equal mass in an elliptical orbit: I know they will be orbiting about a common center of mass, i.e. the barycenter. But, do the velocities have to be equal in magnitude and ...
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### What was the flash I saw in the night sky?

On Saturday night (April 2nd) in Sydney, Australia, somewhere between 8:30 PM and 9:00 PM my partner and I saw three flashes in the sky. We were looking at Jupiter through a pair of 7x50 binoculars ...
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### Magnetic field in blazars

How such high magnetic fields are generated in Blazars? What is the orientation of magnetic field in accretion disc and jets? How magnetic field effects variability? How magnetic field causes shock ...
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### How to create synthetic test images of stars?

Is there any python/IDL code available to create synthetic test images of stars with and without background noise?
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### Can we tell how fast bodies are moving away by measuring their frequency?

It's clear the universe is expanding because light from distant bodies, like galaxies, are shifted towards the red side of the spectrum. In other words, the light measured is more red than it should ...
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### How was precision astrometry done before digital imaging?

Did they just put a ruler on the photographic plate? Quite some precision must have been required to discover Neptune from its influence on Uranus for example.
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### Could we verify the structure of a black hole by observing an orbiting object?

Can we determine the physical structure of a black hole by observing its gravitational effect on objects in orbit? There are three possibilities that I see, and would like to test: Singularity at ...
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### Unknown moving objects

Last night, I used my new Sony WX500 camera to get long exposure pictures of the sky from my backyard. I used the "Heavens Above" app to find out when satellite flares would happen, and I even got a ...
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### How the watches are showing perfect time?

The actual time for one day is 23hrs, 56mins, 4.1secs right? Then how can the clocks and watches can show perfect time? I mean, if I observe the sun rise at 6:00am this day, tomorrow I should observe ...
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### How does an absolute horizon form before the apparent horizon?

If I understand it correctly, the apparent horizon is the boundary between where light directed outwards will move outwards, and light directed outwards will move inwards. Even if light is moving away ...
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### Longitude of the Ecliptic

I originally went to math.stackexchange.com and they suggested I try here as well. I'm trying to figure out how to calculate times of moonrise and moonset for a given position on the earth on a ...
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### What is the definition of “deep space”?

I need to know the definition of deep space. I am an amateur astronomer, and am experiencing some difficulty understanding this.
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### Protocol for establishing longitudinal meridians on other heavenly bodies

When we first observe a new heavenly body (it could be a new star, asteroid, etc., but let's say a minor planet in our own solar system), are there any procedures set in place for establishing a ...
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### What happens over time as a neutron star cools?

My understanding of a white dwarf star is that, although it hasn't happened yet due to the age of the universe, eventually as it loses energy due to radiating heat and tidal forces, it will cool to ...
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### What happens if two or three stars collide with each other?

After finding out that there is a solar system with three stars, I did extensive research. I couldn't get a definitive answer. What would happen if they collided with each other? I know there would ...
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### Is it possible that Mercury was originally the moon of Venus after a giant impact?

Mercury looks like the Moon, and so it makes me think about a question: is it possible that Venus and Mercury were the a same planet originally, and a giant impact with that planet made it split into ...
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### My supernovae question [duplicate]

I understand the collapse of a star during a supernova, as the outward pressure cannot compete with the gravitational field. Is it conceivable, that a relaxation of the space-time curvature is what ...
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### Has the Kepler data been examined for light curves due to phase changes of non-transitting hot Jupiters and other?

I found this article http://www.epj-conferences.org/articles/epjconf/pdf/2011/01/epjconf_ohp2010_03005.pdf from 2011 announcing that two dozen secondary eclipses of "hot Jupters" have been seen in ...
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### Is nucleosynthesis responsible for the expansion of the universe?

Is it just a coincidence that the two major expansionary periods occur close to periods of nucleosynthesis? Big Bang nucleosynthesis occurred very close to the inflationary period. Supernova and ...
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### What is it that distinguishes one atmospheric layer from another?

The atmosphere of a planetary body (assuming it has an atmosphere) is described as being made up of distinct layers. For example, Earth, Saturn and Jupiter all have a stratosphere and a ...