# All Questions

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### Observed sun/moon rise/set times to nearest second?

Where can I find a list of observed (not computed) sun/moon rise/set times to the nearest second, along with the location (latitude, longitude, altitude [or enough information to find these three ...
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### Brain vs galaxy [closed]

The number of neurons in the human brain is equated with the number of stars in the Milky Way. Could the Milky Way act as a consciousness of its own, with the gravitational strength between the stars ...
51 views

### local stellar mapping data

I've been playing around with Near Star Map, and I think I kind of want something more sophisticated, so for all stars within 100ly/30pc, is the following known? velocity (it would be nice to have a ...
87 views

### Exoplanet naming conventions

I'm looking for any exoplanet nomenclature, official, semi-official, proposed, or just a good idea, beyond what can already be found on Wikipedia at ...
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### Accretion of in-falling material for a young main sequence star

I'm reading material that is seemingly contradictory. Some sources indicate that the evolution of a protostar to a main sequence star is characterised by a stellar wind that precludes the accretion ...
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### When do Mercury/Venus reach greatest elevation at sunset/twilight for a given location?

On what day does Mercury reach its greatest elevation (in degrees from the horizon) at sunset a given location? The obvious answer is the day of Mercury's greatest elongation from the Sun, but, ...
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### Are ascending node of sun, the point of intersection of prime meridian and equator and center of earth all collinear?

I did a bit of googling but couldn't find the exact answer, so are the following 3 points collinear or not ? 1_center of earth 2_ascending(or descending) node of sun 3_point of intersection of ...
151 views

### Sky Glow calculations

I am leading a project for my High School NASA Club, and am looking for some advice. The goal of our project is to use a Raspberry Pi to control a camera that takes photos of the sky, and uses the ...
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### What is it like at the edge of the universe? [duplicate]

If the universe is expanding, then if you were to be close to the edge of that expansion, what would it look like? What would be happening? Would it be chaotic? Would objects be appearing or ...
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### Can Space-Time Itself Have Energy Qualities Like Momentum?

Hypothetically, if space could be moved or scaled, what would happen to everything inside? I'd like to know if an element of momentum could be transferred to objects by contorting space-time. Other ...
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### Would bacteria on incoming meteors burn before impacting?

I was watching an old Ancient Aliens last night and there was a whole episode dedicated to how the "Gods" (aliens) were spreading disease/plagues. A good portion of the show was dedicated to how ...
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### I know when the human history ends. Or not?

If you think that we born on 1920...2000 and knows that the sun will explode 4 to 5 billion years from now. you will say that the time is a strange thing. I can not say that i will die before i know ...
32 views

### How could we observe Dyson spheres? [duplicate]

Hypothetically, if Dyson spheres were already present, how could we observe them? My layman understanding of the reason we believe dark matter exists is that our current estimates of the total mass of ...
51 views

### Long term effect on rocks of high pressure and temperature?

The mean surface temperature of Venus is about 460 C and the pressure is about 92 atmospheres. Assuming this situation (or similar) has prevailed for millions of years what changes (if any) would ...
274 views

### Are there large underground caverns on Mars?

Scientists talk about the possibility of life underground on Mars, and I assume they are talking about microscopic life that can live in small gaps in the soil or rock. But is there any evidence that ...
217 views

### Milky way: How do we know its appearance? [duplicate]

How can we know how does the Milky Way look like if we are in it? Sorry if the answer is evident, I am not an expert.
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### What is the size of the universe.is it infinite? [duplicate]

What is the exact size of the universe.is it infinite?
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### Formation of Cosmic Microwave Background

It is said that the cosmic microwave radiation (CMB) was formed when the universe was 379,000 years old. How is this calculated?
157 views

### Planetary gas giants

I've read that a gas giant, like Jupiter, doesn't have a rocky surface. But planets must start as a rocky conglomerate of flotsam. Is the interior so hot that all the material is molten and there ...
98 views

### Is there a paper on galaxy mergers in clusters of galaxies?

I'm looking for something to cite about galaxy mergers in clusters of galaxies. I need numbers on the frequency of mergers in the outer parts of galaxy clusters vs. the cluster center. In the center ...
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### Why can't we detect water on Mars in the same way as in exoplanets?

Often I see news articles claiming astronomers found exoplanets with water. If we are capable of detecting water on such distant objects, why don't we employ similar methods to find water on Mars or ...
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### On (minuscule) dark matter production in supernovae

It is believed that dark matter is made of particles, which interact with matter only weakly and gravitationally. One common candidate for dark matter are so called WIMPs. WIMPs, specifically, are ...
239 views

### What is the Fundamental plane for Elliptical Galaxies?

An alternate explanation rather than from wikipedia is preferable.
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### Using Tully Fisher to measure Distance Problem

Can anyone explain by looking at the solution in the pic, how did the cos (i) came about? I guess they are getting this from the major-minor axis info in the question, but I am not sure about the ...
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### What was the greatest spatial extent of the Asteroid Belt prior to the Late Heavy Bombardment?

Reading the article On the asteroid belt’s orbital and size distribution (Gladman et al. 2009), there is an interest point made: asteroids a few kilometers and smaller in size are recent ...
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### Did the Late Heavy Bombardment Period Happen Because of a Stellar System Collision?

I was thinking about the impending collision between M31 and the milky way galaxy, and I've heard that since a galaxy is mostly space most of the contents of both galaxies would be just fine. Could a ...
148 views

### Do meteorites streak across the sky in the same direction?

Once while camping with my family as a child we all watched a meteor shower in the summer (in the month of August). All the meteorites streaked across the sky in the same direction. Obviously, this ...
105 views

### Is the expansion of the universe greater than the speed of light?

If the rate of expansion of the universe is increasing , won't it eventually become greater than c? Also, after inflation, did the rate of expansion slow down and then start to accelerate again?
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### Spotting the International Space Station (ISS)

Recently, I visited the NASA website which provides sighting locations to see the International Space Station (ISS). As we all know, we can even see ISS with the naked eye in a clear sky as a passing ...
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### Why are (Type II) supernovae so bright?

The vast majority of energy from a supernova is emitted as neutrinos and high-energy radiation, both of which being invisible to the naked eye. Yet a supernova can outshine its galaxy in the visible ...
147 views

### Earth's gravitational pull on ISS

How do they make International space station to orbit the earth beyond earth's gravity acting on it? We all know that ISS is rotating at an altitude of just 350km away.How could ISS escape earth's ...
149 views

### How can light reach us from 14 billion light years away?

One thing that I can't quite wrap my head around is how light is traveling to Earth from 14 billion light years away, aka the beginning of the universe. The way I see it, the universe itself was very ...
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### What is the galaxy M87 doing these days?

The massive elliptical galaxy M87 in the Virgo cluster is 53,490,000 light years away. It also contains one of the largest, heaviest supermassive black holes in the known Universe. But it's also my ...
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### Why natural satellites (moons) of all Planets are Solid?

Why the natural satelittes (moons)of all planets including moons of Gas Giants are are Solid or Rocky and not gaseous like them?
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### Are there standard algorithms and procedures for creating unique sky maps based on latitude/longitude/date/time?

I am trying to build an astronomy app that will use the user's latitude and longitude, along with the current date and time, to create a 3D view of the celestial sphere as seen based on that data. ...
84 views

### Requesting book references for a non-expert person with math background or just a non-expert person

I've just finished my masters degree (to be exact previous week ^_^). And I'm completing my collection of applications of my studies. During previous year I started reading about Robotics and Coding ...
156 views

### During an eclipse, does the size of the moon and sun match perfectly?

During a lunar or solar eclipse, from our perspective when we look towards the moon and the sun is behind the moon, does it fit exactly? Has anyone calculated the sizes of each in a relative ...
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### How certain are we about the universe's flatness?

The universe is thought to be flat: $\Omega = 1 \pm 1\%$. As I understand it we can determine this by measuring triangles against the CMB. Yet during inflation dark energy made the universe grew ...
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### Is there matter forming in the inflationary space?

Following the answers and the line of thinking from here Is there enough hydrogen left after a star dies so another star will have enough to light up? I was wondering if is there any possibility to ...
275 views

### Can you explain the pattern of Hill sphere sizes of the objects of the Solar system?

I found this image on calculations of Hill sphere for planets/dwarf planets of the Solar system. From http://en.wikipedia.org/wiki/File:Hill_sphere_of_the_planets.png I found it interesting that ...
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### How fast is a comet moving when it crosses Earth's orbit?

Is it about the same as Earth's orbital speed?
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### What is the ultimate fate of a cluster of galaxies?

We're fairly aware clusters of galaxies drift apart due to space expansion, which will drive them out of each other's cosmic event horizon eventually, leaving them separate, alone, each a single ...
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### Conundrum involving distance to object, universal expansion, age of universe, etc

I was recently reading about a galaxy or quasar (not sure which, so lets just say quasar) where the estimated distance to this thing was some very significant fraction of the age of the universe. ...
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### Expansion of the Universe [duplicate]

Please forgive my ignorance. I dare say that these questions arise from me trying to understand the nature of the Universe using Newtonian physics. There are a few things that really bother me when ...
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### Which kind of properties can we get for cosmic ray particles hitting on an optical ccd?

It is very common that we meet cosmic ray particles in optical images recorded by CCDs. You can see the "snowflakes" in the hubble images below: Generally we should remove them in order to get ...
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### Selecting a Telescope for Viewing Planets

I hope to observe planets like Jupiter and Saturn, and moons. I am a novice when it comes to telescopes and I know images in magazines are not taken with at least 12-inch telescope in a middle of ...
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### How can I collimate a dobsonian telescope with a laser collimator?

I've had a dobsonian telescope for a while now, but I've never been able to collimate it. I thought I had it collimated once, but when I looked through it the star didn't look right, it looked kind ...
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### Collimator for Dobsonian, same as Newtonian?

I have been looking on line for Collimator for my Meade Dobsonian. The only Collimators I can find are made for Newtonian Lenses. It's a 8" mirror with a 1.25" lens. Will this work for my telescope?