# All Questions

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### How can the universe be infinite?

I've heard from renowned astrophysicists that we don't yet know whether or not the Universe is infinite. How is that possible regarding the big bang theory is accepted (as they all do)? Are they ...
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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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### Big Bang / Big Crunch cycle?

I've been reading some of Stephen Hawking's work on the theory of the expansion (and ultimate contraction) of the universe and was curious if anyone has every hypothesized that the universe has ...
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### Why is [O III] a good density probe in interstellar medium?

According to Draine in his book "Physics of the interstellar and intergalactic medium" (page 210/211) and Caltech [O III] line ratio's (amongst others) are a good density probe, but I cannot really ...
190 views

### Basic DIY Telescope

I am looking for a design of a cheap and easy telescope to build with my 9yo daughter with the only basic requirement being that I'd love to be able to see detail on the moon. Looking around, there ...
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### Origin of the original bright light and matter [closed]

Do any theories exist as to where this bright light and matter came from that expanded to form our Universe ?
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### How fast does Venus move as seen from the earth?

So last night I was about to sleep with the window in front of me. there was a 3 inch gap between the curtains that let me see a small portion of the sky. I could see something magnificently bright in ...
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### Meteorites bring water

The latest information suggests that Earth's water came from Meteorites . The Moon was also bombarded by Meteorites and yet it has no water. Is this because it lacks an atmosphere and its water was ...
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### Why is liquid water considered a requirement for life?

I`ve heard about different extremofiles living on earth. Is water a requirement for life because we have not seen life survive on earth without it, is it a chemical reason which makes life without ...
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### What is the line of light in galaxy cluster MACS J1206?

I noticed this in a thread from world building, what is the continuous line of light in MACS J1206 slightly right of center in this picture? The only thing I could think of would be the side view of a ...
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### What is the process for vetting the 4,175 candidate planets Kepler has discovered?

In the National Geographic article about NASA's announcement of new planets discovered by the Kepler spacecraft, it states that there are 4,175 candidate planets. What is the process for vetting these ...
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### What scientific evidence is there to support or refute the Iron Sun Hypothesis?

Professor Oliver Manuel, a professor of nuclear chemistry at the University of Missouri-Rolla, claims in the article Sun Is Made Of Iron, Not Hydrogen, Professor Says that iron, not hydrogen, is ...
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### How do astronomers choose their research topic? [closed]

Astronomers don't face much of an ordinary jobs market in their "trade". What does the process look like from choosing a topic for the PhD to doing research in a specific topic? Let's say that you're ...
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### What is the shape and size of a gamma ray burst?

As I understand it, a gamma ray burst is created when a massive star collapses into a black hole. The poles of the black hole eject a massive burst of energy which we know as gamma ray bursts. So my ...
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### Why stars are named Gliese?

There are exoplanets called Gliese 581c, Gliese 581d etc. I assume their star is Gliese 581. So where does this Gliese come from?
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### How do or could radio telescopes contribute to exoplanet studies?

Current and upcoming telescopes which find exoplanets and take spectra of their atmospheres seem to be optical or infrared. What about radio telescopes applied to exoplanets? They are larger and more ...
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### What causes jets from newly born stars?

Newly born stars often have bilateral jets of gas ejected from them at high speeds (hundreds of km per seconds), often ending in Herbig-Haro objects. As I understand it those jets would have something ...
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### US observations relevant in UK?

When I listen to the Planetary Radio podcast, there is a section at the end where they suggest objects to look out for in the night sky. If I am in the UK, but they are talking about the USA, will I ...
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### If the expansion of the universe is speeding up, how long until everything nears the speed of light, and what would happen?

Since dark energy is causing everything to speed up infinitely, wouldn't everything near the speed of light? And since it's nearing the speed of light, wouldn't all kinds of strange things start ...
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### Did cosmological inflation occur at speeds greater than $c$?

If cosmological inflation occurred at speeds less than $c$, wouldn't we see the CMB right in front of our noses (or not at all) instead of at 13.7 billion light years? And if it happened faster than ...
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### Objects entering or leaving the observable universe

Have there been any observations of objects entering or leaving the observable universe? When looking at the physical limit of observing something like this I will to assume that the "object" would ...
162 views

### Milky Way Formation

Is the Milky Way a collection of merged galaxies, or has it only been one galaxy that was created from the interstellar media?
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### When will the Milky Way “arrive” at the Great Attractor, and what all happen then?

The Great Attractor is described as a location to towards which the Milky Way, along with all other galaxies in the Laniakea Supercluster are moving. How long will it take for the Milky Way to ...
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### Would bagging an asteroid destroy valuable science about it?

NASA has a plan called "Asteroid Redirect Mission option A". It would robotically put an asteroid of a few meters diameter in a bag and push it into reach of astronauts for thorough examination. 44 ...
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### Observational Evidence for the Existence of Black Holes

What is the direct observational evidence that black holes exist? I have read that black holes have been detected through X-ray emission. What is some other observational evidence for black holes?
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### How did the Hulse-Taylor Pulsar Provide Confirming Evidence of General Relativity?

What measurements and observations of the Hulse-Taylor Pulsar agreed precisely with the predictions of general relativity, and how did these measurements support the theory?
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### Mechanism for Brown Dwarf Fusion

I've read (at here, among other places) that during the Degenerate Era, star formation will end and the last stars will go out. But it was noted that there is still the possibility of star birth, ...
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### Spectra of electromagnetic radiation emitted during solar flare

During solar flare, electromagnetic energy is released at a wide range of wavelengths but the most dominating are x-rays and extreme ultraviolet rays. Why is that intensity of these wavelengths is ...
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### Do Roche limits apply to black holes?

Consider black hole A, a super massive black hole at the center of the galaxy. Orbiting it is black hold B, a less massive black hole. If some passing body were to modify black hole B's orbit such ...
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### Near-future astronomic events that could threaten Earth

What kinds of astronomical events can pose a serious threat to life on Earth in the near future (1000-10,000 years). If there are none in the near future, when is the soonest event that is predicted ...
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### Collision of two Earths

Assume that two Earth-like planets orbited the same star, with elliptic orbits. Eventually, something occurs that caused the two planets to collide. What would be the outcome of such a catastrophe? ...
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### What's the furthest object observable by the naked eye from earth?

From XKCD: Caption: 'The light from those millions of stars you see is probably many thousands of years old' is a rare example of laypeople substantially OVERestimating astronomical numbers. So, ...
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### Photos from galaxy

So, I hear people say blah blah blah is 3 light years away, and here's a photo. So does that mean the photo that we see are actually at least 3 years ago since that's how long it takes that light to ...
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### As days get longer, why isn't the added daylight split evenly between sunrise and sunset?

I have a basic understanding of the sinusoidal relationship of the rate of change of daylight as the year goes on. But it seems intuitive that the changes should be equally split between sunrise and ...
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### How can I predict space directions?

Did the Neptune and Pluto trajectories ever cross or was it a mere reclassification? Do studies say that I can predict an intersection between 2 trajectories or movements based on data now? Do I have ...
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### Why is the Eagle Nebula so “static”?

This, of course, is a newbie question, as I am nothing more than a hobbyist. But I was quite surprised to see the recently-released "before and after" pictures of the so-called "Pillars of Creation" ...
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### If an asteroid twice the size of Earth passed super close would half of the Earth be pulled towards it?

So let's say that an asteroid the twice the size of Earth passed by going relatively slow say in between the Moon and Earth. Among so many other things (and perhaps you can touch on some of the ...
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### Do contracting objects show redshift?

If we consider a point on the central part of a contracting object as observed from earth, the point is continuously moving away from us as the object contracts. Moreover, light emerges from a deeper ...
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### What would happen if a wormhole gets swallowed by a black hole?

Assume wormholes exist: one hole allows matter to pop out of another hole somewhere else in the universe. If one end of the wormhole is swallowed by a black hole then no information can get from that ...
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### Does CIBER Experiment from Caltech suggest that there can be lots of stars which are not in any galaxy?

My question is about the implications of the observations recently made by the Cosmic Infrared Background Experiment, or CIBER, from Caltech. I've read at Caltech web site: "The total light ...
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### Is there an element of chance/chaos in stellar evolution?

Since stars are an ideal example of macroscopic objects, is their evolution determined by their initial mass and metallicity? Are there any non-trivial random internal processes going on that may ...
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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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### Quantum death of stars

This comes from a comment on this question, to quote: The death of (large mass) stars is also based on quantum events with probabilities technically not 1 (and is very fast), so it is technically ...
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### What are dark matter and dark energy? [closed]

I've recently read about dark matter and dark energy. But unfortunately, there were not enough answers for me. The article I read was more of a hypothesis than a real answer. So I'm asking for all the ...
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### Working with high-magnification eye-pieces

My telescope (Newtonian reflector) has a focal length of 900 mm. So, using a 25 mm eye-piece, I get 900 mm / 25 mm = 36X magnification. Using a 10 mm eye-piece, the magnification would be 90X. My ...
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### Lack of contact with Aliens [closed]

Lack of contact could be due to one of three things ? Interstellar space travel is just not possible . There is no other Alien Life in the Galaxy . There exists Alien life and interstellar space ...
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### What does designation VY, NML, UU in star names stand for?

I've read the a IAU page on the subject but i am no closer to understanding how this works. Also did search the already asked question, but didn't see anything on the subject. What does bolded item ...
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### Astrochemistry - what does freeze-out mean?

I was recently watching a video on the physics and chemistry in planetary accretion disks, and the speaker at a certain point mentioned 'freeze-out and UV dissociation'. Is freeze-out a purely ...