# All Questions

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### Is “Main Sequence” a temporal sequence?

Stars plotted by luminosity and surface temperature fit into patterns in a Hertzsprung–Russell diagram. A rough diagonal subset of this plot is called the main sequence. Is this in any sense a ...
292 views

### How long will it take Pluto to grow to planet size? [closed]

Pretty much everything in our solar system has collisions with smaller objects that lead to an increase in the mass of the larger. With Pluto being one of the largest things in the area of which it ...
208 views

### Does Sun have a reflection on Earth?

The new Google Maps1 presents an actual view of Earth, with the current position of Sun illuminating half part of Earth in real time. It is quite an exquisite view. My question is based on the ...
159 views

### Given a date obtain latitude and longitude where is the sun zenith

Searching is easy to find terminator line (frontier between day and night) or the position of the sun in the sky given a position on the earth and a time; but I can't find how to obtain where is the ...
182 views

### What is the name of our Solar System?

what is our Solar System called rather than "the Solar System"? I've found "Sol System" and "Monmatia", too, but is there more to it?
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### Is the Milky Way Visible from Nebraska?

Is the Milky Way Visible from Nebraska? If so, where is the best place to view it, and also what would be the best time of night to see it? I know this is probably a very novice question, just ...
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### Milky Way stellar number density : is the stated equation in this paper incorrect?

The paper is : http://www.astro.washington.edu/users/ivezic/Publications/tomographyI.pdf The equation is equation #23 in the paper. It's a model for the density of stars in the Milky Way's disk. It ...
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### How do you calculate length of day in a multiple-star system?

How can you calculate the length of day for a planet (given a particular latitude and longitude on that planet) orbiting multiple stars? What about a planet that is orbiting one star, but that star ...
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### 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 ...
1k views

### 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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### Why some stars appear to move differently when viewing device shakes

I was looking at Arcturus with a pair of binoculars, and noticed that when they vibrate due to my heartbeat, Arcturus seemed to move differently than the other dimmer stars. I started playing with ...
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### Age of the universe vs. its contents

A couple of decades ago I read an article (could have been either Astronomy, Space, or Science News) that suggested the contents of the universe may be older than the universe itself. Of course, that ...
158 views

### Interstellar movie: What is the “portal” to the other galaxy?

I recently watched Interstellar with some friends and we didn't come to the same conclusion. In my opinion, the portal they use to go to the other galaxy (to visit the three planets) is not a black ...
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### Is metallicity low at the central region or nucleus of the Milky Way?

Is metallicity low at the central region or nucleus of the Milky Way? Does metallicity decrease or increase as we move from the center out to the edges of our galaxy?
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### Why do pictures of the Milky Way look like a spiral?

When I see pictures of the Milky Way they show a spiral shape. Why is this?
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### How can I use Polar Alignment to find objects in the sky?

I have a six inch telescope on an equatorial mount and I've been struggling to use the mount properly. For a couple months now, the only strategy I've used is just 'point and look.' I've watched some ...
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### Does the universe prefer a velocity?

As I understand it, the distribution of matter is roughly homogeneous across space -- anywhere I stand in the universe, there will about the same amount of matter in every direction around me. Is the ...
62 views

### Metal rich or metal poor?

What does the image in the link mean? Are the stars in the halo high in metallicity or low? How about at the bottom by the disk? ...
252 views

### What are the arguments against the Feng and Gallo thin disk explanation of galactic rotation curves?

The well-known galaxy rotation problem is described here. Basically (as one moves outward from the galactic centre, $R$ increasing) the observed pattern of variation in orbital speed $V$ is very ...
8k views

### What's the fastest moving object in the universe?

We know that nothing can have proper velocities larger than the speed of light in vacuum. But are there any objects in space that get close to it? Any comets, or other objects thrown by gravity or ...
119 views

### Name and language of symbol in astronomy book

I've been working on a programming project involving Peter Duffett-Smith's Practical Astronomy With Your Calculator (3rd Ed.), which has a large number of mathematical/astronomical formulas in it. ...
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### Available data on the Milky way around 1920

In a book by Alexander Moszkowski, there is an Einstein quote about a hypothetical size of the universe (100 million Light years). Moszkowski claims that Einstein had deduced that from the ...
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### What is the distance that the Moon travels during one orbit around the Earth?

Also, does it always take the same amount of time, or does it fractionally differ on each revolution?
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### Do Noctilucent clouds cause problems with telescopes?

Noctilucent clouds are at around 85km altitude and are formed of ice crystals. The ISS recently posted a number of photographs of these clouds and pointed out the key feature, which is the bright blue ...
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### What was the orbit of the meteor that impacted the Moon on 2013 September 11?

On 2013 September 11th, a meteor impacted the Moon leaving a 34-meter crater. So far the only info I've found was from youtube (https://www.youtube.com/watch?v=zCFDkj2JtyA) and this site: ...
368 views

### What will happen when landing on Jupiter?

Jupiter is a gas giant, so landing on it will not be like as on Earth, our moon or Mars etc., as it does not have a solid surface like these. If we have a hypothetical spaceship or probe landing on ...
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### What is the force of a CME on objects in space?

I've been reading a little bit about coronal mass ejections lately and they seem really interesting, and they cause a lot of amazing things to happen. However, one thing I haven't seen is the physical ...
209 views

### When will we be able to detect Earth-sized exoplanets?

I have heard that the only planets able to be seen outside the Solar system are Jovian-sized planets with the occasional detection of planets three times the Earth's size. But, as far as I know, we ...
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### How do we convert other waves of the EMS to visible light?

So I just had a quick question and I was wondering how we convert other waves of the electromagnetic spectrum to visible light waves. For example we use X-ray's or radio waves to see things in space ...
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### In 2016, the summer solstice will coincide with a full moon. How often does this happen?

I found that the solstices work on a 400 year cycle based on this. I can't find anything similar for the lunar cycle. Is there a formula I can use to calculate the date of the full moon?
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### Apollo Moon Landing [duplicate]

Can there be any truth to the rumour that the Apollo Moon landing in 1969 was staged ? I dismissed this rumour as being nonsense but today on the news I was surprised to hear that the head of the ...
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### What makes a really good observatory site, besides altitude?

Let's limit this to optical telescopes. I understand that the higher you are, the less atmosphere is above you to get in the way of observations. From reading around, there seem to be a few more but ...
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### Is it possible to use Hubble Telescope to observe Earth in the past?

We can observe many astronomical objects and structures beyond our solar system, however our observations are as the objects appeared in the past due to the speed of light. My question: "Is it ...
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### Why won't the Milky Way colliding with Andromeda affect the Solar System?

According to Wikipedia Such an event would have no adverse effect on the system and the chances of any sort of disturbance to the Sun or planets themselves may be remote. I'm imagining that this ...
102 views

### Why does the focal length of a telescope have an effect on the magnification?

I previously asked that Is the angular resolution of a telescope irrespective of used eye-piece? I learned that the resolution is fixed when the light enters the telescope, and that the ...
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### How accurate are rederings of something entering Earth's atmosphere?

Supposedly how accurate is it when you see a movies showing something entering Earth's atmosphere traveling 1 mile to 10 miles an hour or barely at all but skinning the atmosphere they show it heating ...
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### Accelerating universe expansion and standard candle

Recent stars (and standard candle supernova), afaik, contain more heavy elements than older stars. As consequence, I guess, recent stars and supernova should be slightly dimmer than older stars? If ...
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### Pulsars: How do astronomers measure minute changes in period (~picoseconds per year)?

I've been to some talks that mention how stable the period of a millisecond pulsar is over long periods of time. Recently, it was mentioned that astronomers have calculated the change in period over ...
329 views

### What is the difference between solar wind and solar radiation?

Is there a difference between solar wind and solar radiation or are they just different ways of describing the same thing?
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### Is our universe included inside a black hole?

This question repetitively comes to my mind but I've never found any good scientist article to argue about it, only esoteric or speculative web articles without much valuable background. So let's ...
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### For how many bodies can there be a stable orbit with no very heavy central body?

The question is a bit vague, but let me explain: Take for example 2 bodies of the same mass. They can orbit around their centre of mass/gravity. Is something like this possible with multiple ...
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### Does the Moon have any oxygen in its atmosphere?

Since the moon has gravity, it's almost impossible that there aren't some gasses trapped on the surface by the moon's gravity. Has any free-floating oxygen been found on the Moon? If so, in what ...
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### How does the Grand Tack Hypothesis explain how Jupiter formed inside the frost line?

The Grand Tack Hypothesis states that Jupiter formed at roughly 3.5 AU from the Sun, then interacted with a large portion of objects in the Solar System before settling into its current orbit. Yet as ...
260 views

### What Causes the Large Radiation Fields Around Jupiter?

I had heard that the large radiation belts around Jupiter may be formed by liquid metallic hydrogen in (or around) Jupiter's core (which Wikipedia says haven't been observed in labs yet due to the ...
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### How did Jupiter form where it is?

Since Jupiter is the biggest planet in our solar system and is made up of mostly hydrogen and helium, (the gases the Sun uses to create energy), how come it didn't form as far out as say Uranus or ...
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### Moon's orbit around the Sun

The Earth revolves around the Sun and the Moon revolves around the Earth. Out of curiosity I started thinking about the orbit of the Moon around the Sun and expected (assumed) it to be as follows: ...
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### How do astronomers determine the texture of an exoplanet?

So I was wondering how astronomers are able to get the texture/detail of an exoplanet or how they know a planet has water or not. I know how they discover planets by using the light of a star and ...
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### Is the Dwarf Planet class really necessary?

Another way of asking this is, what is the difference between dwarf planets and asteroids? Aren't they the same things? It's just that some asteroids are spherical and others aren't...or is there ...
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### is there any theory or observational evidence that our universe is electrically neutral or not?

It seems our universe is neutral in large scale. There is CP violationwiki problem about matter and dark matter. Similarly is there any theory about whether our universe is electrically neutral? ...
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### The tidal locking problem concerning Earth sized planets in habitable zone around Red Dwarfs

Would twin planets orbiting around each other present a solution to tidal locking of habitable planets in red dwarf systems? It's an awfully easy equation to set up. I'm fibbing; I can't do it. I was ...

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