# All Questions

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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? ...
939 views

### 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 ...
355 views

### 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 ...
55 views

### 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 ...
2k views

### 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" ...
427 views

### 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 ...
64 views

### 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 ...
157 views

### 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 ...
79 views

### 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 ...
128 views

### 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 ...
88 views

### 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 ...
81 views

### 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?
113 views

### 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? ...
121 views

### Questions about a fictional binary system, and habitability [closed]

Note: Questions are at the bottom. The rest had simply been written in a format to better organize my thoughts. The formulas used to construct this fictional solar system, had been borrowed from ...
335 views

### How is the path of an asteroid calculated?

How do scientists and astronomers recognize the perfect path or orbit (if it's orbiting an object) of an asteroid or a comet? Just curious! Thanks in advance!
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### Question: calculating orbit using another orbit

A satellite which is moving around a planet of mass $M$ in a circular orbit of radius $R$ is given a sudden thrust into the center of the planet, so that it deviates an angle $a$. Find the ...
59 views

### Could supermassive black holes form in dwarf galaxies?

Supermassive black holes often exist in large galaxies (e.g. the Milky Way, Andromeda). They make up a fair portion of the galaxy's mass. Is it possible for a supermassive black hole to form in a ...
224 views

### How is the diameter of a gas giant calculated?

As we know atmospheres of celestial bodies don't just stop at a given distance. They gradually become less dense as you move away from the center. I understand that the diameter of stars is ...
507 views

### Maximum and minimum gas giant & ice giant densities

I'm working on a star system generator for a game; I'd like its results to be plausible but they needn't be super-realistic. I've got the orbital distances and masses of each body in the system, and ...
185 views

### Is the white hole a myth or not?

I've been doing some research on white holes, and there has not been enough information to provide the answer. Some websites are saying that they might exist, but it is not yet proven. So, is it true ...
482 views

### Are there any known objects in a “dual” tidally locked orbit?

Is there any known pair of objects tidally locked with each other? I know the moon is tidally locked with the earth (e.g. one side always facing earth), but I don't know of any pair of objects that ...
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### landing on a comet is more important than landing on an asteroid?

Philae landed on comet 67P this year. And it means a big breakthrough for the science and technology of human being. However Hayabusa mission of Japan not only landed on an asteroid but also returned ...
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If there are indeed multiple universes, where do they exist? We "know" that outside our universe, consisted of spacetime, there is nothing - i.e. 0 dimensions, no space and no time. So "where" are ...
729 views

### Position of Neutron stars in H R diagram

Why is that Neutron Stars are never depicted in an H R diagram? They can be placed in the bottom right corner but you will never find any diagram in literature showing neutron stars.
111 views

### How should exoplanet discoveries affect SETI?

Given that SETI was created before the discovery of exoplanets, has this changed how they search? Would it make more sense to focus efforts on discovered earth like exoplanets?
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### Which wavelength is the most quiet, for a ground-based radio telescope?

This might seem like a backwards question, but I'm interested in what wavelength to select in a (hypothetical) ground-based radio telescope observation to expect detecting as little as possible! :) ...
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### What is the temperature of an accretion disc surrounding a supermassive black hole?

What is the temperature of an accretion disc surrounding a supermassive black hole? Is there plasma in the disc?
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### Why do comets come from our local Oort cloud instead of from interstellar sources?

Comets form where stars form. And they are then ejected by the orbital changes of giant planets. But why are they ejected to form specifically a local Oort cloud instead of going interstellar and ...
258 views

### How to see Saturn's rings through a pair of binoculars?

I have a pair of 15x70 binoculars. I would not say what manufacturer to avoid being the subject of 'hold'. The current angular diameter is 15.5 arcseconds. I am wondering if that condition is enough ...
265 views

### Is it possible for a star to orbit a planet?

Is it possible for a red dwarf to orbit a gas giant? OR Has this happened and it is just assumed that the gas giant is orbiting the star?
105 views

### What are the odds of (Semi) Intelligent Life in the Milky Way? [closed]

I know that it can vary A LOT if you are using the Drake Equation but using realistic figures, how likely is it to discover a civilisation that is at least semi-intelligent (stone age - medieval era, ...
74 views

### One Universe or Multiverse? [closed]

I watched a program where four astrophysicists were debating this topic. I couldn't fully understand what they were saying but wanted to ask others' opinions on whether there is only one Universe or ...
221 views

### What is the orbital path of the newly discovered star-less planet PSO J318.5-22?

Recent results from Institute for Astronomy at the University of Hawaii at Manoa claim that there is a Jupiter-sized gas giant planet that is independent of a star about 80 light-years from Earth. ...
230 views

### Can Jupiter's bands be made out using a 15x70 pair of binoculars? [closed]

I have been getting mixed opinions on this. I have a 15x70 Pair of Binoculars. I have tried staring at Jupiter for several minutes with it, I was able to see the Galilean moons, in fact the last time ...
101 views

### How can I make Stellarium match the magnitude of stars visible in London, UK?

Can someone recommend some Stellarium settings to mimic the amount of light pollution, and magnitude of stars that should be visible on a clear night in London, UK?
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### How do we get radio signals of the big bang?

From TV shows I have known that we still get some radio signals of the big bang and they are every where. My question is is the universe expanding so fast that even electromagnetic wave has failed to ...
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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 $M$ ...
178 views

### Could we actually freeze a star?

I read an article recently that said NASA has discovered a brown dwarf that has frozen. If we had the technology, resources, and supplies, could we actually freeze a star and stop it from burning its ...
129 views

### Universe as 2d sphere surface - a round trip?

If Universe's analogy is 2D surface of the sphere, could we come around in circle? Say on Earth you decided to travel straight in one direction, after completing one full circle you'd find yourself at ...
444 views

### Full Moon Position of Sun

I am trying to figure out the position of sun with respect to moon on a full moon day. Here's an image from certain wiki which I do not find convincing. 1 If the sun rays point as shown in the image ...
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### Why is a star at its highest point when local sidereal time = RA (right ascension)?

I'm currently taking a course called Introduction to Astronomy at Coursera. It's not very formal so they didn't present a proof of the statement in the title. I understand why logically one could ...
548 views

### What to look for in a tripod for binoculars?

I have been looking at large astronomy binoculars in the 25x100 and 20x80 range. Clearly, these monsters cannot be held steady by hand, or even be held at all for any reasonable length of time using ...
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### Is Nomad data heliocentric or geocentric?

I'm wondering if the data in star catalogues are heliocentric equatorial coordinates or geocentric equatorial coordinates. Also given the distance between stars compared to the distance between the ...