10
votes
4answers
6k views

What is the difference between our time and space time?

I am trying to understand the phenomenon of space-time. But, everything on internet seems to be too complicated for me since I do not have a background in physics. Can anyone give me simple ...
5
votes
0answers
65 views

Are stars NML Cygni, UY Scuti, VY Canis Majoris and VV Cephei near the ends of their lives?

Are the three stars mentioned in the title stars that are going to go supernova, or are they stars that are in mid-life, like our Sun, but just happen to be so much larger than our Sun?
3
votes
2answers
80 views

Do NEA (Near Earth Asteroids) have minable water ice?

Water is very useful for rocket fuel and life support in space. But does water, in abundance and form which conceivably could be usefully mined this century, really exist in NEA's? Or do we have to go ...
1
vote
2answers
80 views

What is the axial tilt of a planet measured relative to?

I am very much a beginner on the astronomy front but I understand about planets having different axial tilts, hence why Venus turns the opposite direction from the Earth and Uranus turns sideways. ...
3
votes
1answer
68 views

Why was Pluto's resonance not discovered until 1965?

Over here, I was shocked to learn: The Neptune–Pluto system lies in a 3:2 orbital resonance. C.J. Cohen and E.C. Hubbard at the Naval Surface Warfare Center Dahlgren Division discovered this in ...
2
votes
1answer
115 views

Day Length on Double Planets

Assume two similarly sized bodies tide-locked to one another orbiting a barycenter between the two. That barycenter orbits a star. Since the two are tide-locked, their sidereal rotational period and ...
0
votes
1answer
35 views

Where to get Polaris Right ascension value from

To calculate for example the polaris hour angle I use this formula to calculate polaris hour angle. τ = θ - α τ= hour angle θ= sideral time α= polaris RA (~ 2h32m) But where does the α=2h32m come ...
4
votes
0answers
41 views

Could the James Webb Space Telescope detect biosignals on exoplanets?

The James Webb Space Telescope (JWST) which is slated to launch in 2018 will bring us a better view of exoplanets, but will it be sufficient to detect signs of life on at least some of those worlds? ...
0
votes
1answer
42 views

What is the next planned mission that can discover life on another planet?

I've heard that we have a great shot at finding life on Mars if we just drill deep enough down to the surface to the water and detect if its sterile or not. Are there planned missions to do this? If ...
0
votes
1answer
32 views

Why doesn't the Moonrise appear red when viewed from orbit?

After searching through many videos, I finally found one that shows, from the perspective of low earth orbit, the Moon transiting the horizon. It is actually a Moonset, but it shouldn't make a ...
-1
votes
0answers
36 views

Can we spot a gray-goo exoplanet? [on hold]

How would look an earth-like planet eaten by nano-machines? I guess there must be some properties we can assume from different nano-machine scenarios - strange size, too uniform landscape (a perfect ...
0
votes
1answer
96 views

Stability of solar system

My question is simple: Is the Solar system stable? You can see this Wikipedia page. Edit: Sorry, because i think my question is more about mathematics and classical mechanics of planets in ...
1
vote
1answer
66 views

What is the air pressure in the heliosphere (Sun's atmosphere)?

Specifically, I am wondering what the pressure is at a distance of around 1 AU. Does it it decrease quadratically with distance?
2
votes
0answers
28 views

Why didn't we have inflation when the theory of everything and GUTS broke symmetry? [closed]

Inflation seems to have occurred when the symmetry breaking of the electroweak occurred. But do we know of any reason why we did not have inflation when gravity separated from the other forces or ...
-1
votes
1answer
46 views

what is the time mentioned after date (1962-07-03+02:00) the +02:00? [closed]

i was retrieving a some personalities birthday date through computer programming when i retrieve a person's birthday the result was ...
1
vote
1answer
114 views

What uncertainty does an error bar signify in astronomy?

When an astronomer talks about her/his topic and shows an X/Y-plot with error bars. What should one assume that those error bars represent? 1 standard deviation? Or 2? Or some specific significance ...
0
votes
1answer
84 views

Eternally collapsing objects?

As has been pointed out by some scientists, that black holes aren't stable bodies but are eternally collapsing objects. How does one come to such a conclusion? Is hawking radiation related to this in ...
0
votes
2answers
85 views

Accidental or deliberate? [duplicate]

We know the visual size of Sun and Moon from the Earth in our life time(!) are nearly equivalent. Now my question: this event is random or have a scientific reason? For example maybe there is ...
1
vote
1answer
128 views

What is the brightest star (by absolute magnitude) that we can see by naked eye?

Is it Rho Cassiopeiae or Mu Sagittarii? I see in the Stellarium 0.13.0 that Mu Sagittarii have absolute magnitude -11.43!!
0
votes
1answer
26 views

Are mass extinction events more likely during meteor showers / passing through comet debris?

Meteor showers happen when Earth passes through the debris left by a comet in its orbit. Meteors are generally tiny, like snow flings or pebbles and don't make it to the ground as meteorites. But ...
3
votes
2answers
73 views

Is any meteorite known to come from a comet?

Comets are mostly icy but they should have some rocky components too, right? I wonder if there's any rocky piece of a former comet among collected meteorites. Is it possible today to identify a ...
2
votes
1answer
54 views

How to calculate the limiting magnitude of Hubble?

I've found various sources on the web stating that the limiting apparent magnitude of the Hubble Space Telescope is about 31 or 31.5. Wikipedia lists that here and it has a cite to a pdf about it. ...
4
votes
2answers
360 views

Are space telescopes completely out of the earth's atmosphere?

Is the Hubble Space Telescope, and every other space telescope for that matter, completely outside the Earths atmosphere?
4
votes
2answers
157 views

Would a tablespoon of a neutron star remain intact?

I've heard people say that a tablespoon of neutron star would weigh over a billion tons. If we ever could take a tablespoon of one would it still remain intact with the same density?
1
vote
4answers
119 views

Image sets for testing stacking algorithms?

I am looking for sets of astronomical images for testing different kinds of stacking algorithms. The idea is simple: if one has $N$ images of the same object, the signal-to-noise ratio of the ...
0
votes
1answer
29 views

Eclipse on the moon

What kinds of eclipse is seen by the person on the moon, when there is i)Solar eclipse on the earth and ii)Lunar eclipse on the earth
1
vote
3answers
150 views

Years, Months, Day, and Weeks?

Sorry if this is a basic question. 1 year = earth revolution around the sun 1 month = moon revolution around the earth 1 week = 7 days = ??? 1 day = earth rotation about its axis Why do we ...
1
vote
1answer
67 views

How much larger would a star have to be to cause thermonuclear reactions if it was made out of mostly rock like Earth, instead of gases?

I assume it would have to be considerably larger since rock isn't as flammable as gases are? But it's also more dense to begin with.. Do we know of any suns that are made like this? Is it even ...
5
votes
1answer
176 views

How can Halley's Comet be predictable?

How can we know that Halley's Comet is going to come again every 76 years? I understand that the comet has an orbit around the sun but how can scientists know that it won't be thrown off course for ...
0
votes
1answer
36 views

How can I find out which known stars lie within or close to M8

I'm looking for a way to find stars within a certain region of space, the Lagoona Nebula in this case, based on what we currently know. Are there some databases that allow you to make such queries? ...
3
votes
2answers
137 views

Does the mass of the observable universe ever change?

First do we have anyway to even estimate the mass of the entire observable universe? And then is there any data that shows mass being gained or lost? Would we ever know if someone was playing with ...
1
vote
1answer
66 views

How to find Exomoons?

How would we be able to detect Exomoons? We detect exoplanets by seeing if the light gets faint from a star, but could we really use the same method for determining if there is an exomoon around that ...
0
votes
0answers
41 views

Stellar mass database

I need a stellar mass database that also has the distance of the star/system from the sun. Can anybody tell me the name of such of database and where I can find it. I need to do a project on this. ...
2
votes
2answers
115 views

Does a week represent something in astronomy? [duplicate]

I know that a day represent the time for the earth to make a full rotation around its own axis and a year is the time for the earth to make a full rotation around the sun. But does a week represent ...
0
votes
2answers
52 views

Star formation analogy

If I have understood correctly, stars form in big clouds of gas and dust that are pulled together by their gravity. And the stars are often ignited when something disturbs the cloud, such as a passing ...
1
vote
1answer
82 views

Which is the shape of the sky?

I'm a software developer and I'm developing a planetarium and the first thing that I don't know is: What is the shape of the sky? First, I though that it is a semi-sphere, but searching on Internet I ...
-1
votes
4answers
243 views

Does the Sun turn around a big star?

The moon turns around the Earth. The Earth turns around the Sun. Does the Sun turn around a big star? If so, does this big star turn around a very big star? ... etc ... What are all the intermediate ...
19
votes
3answers
3k views

Does the Earth have another moon?

I was just wondering what are the chances that there is a small object (say less than 1 km but more than few meters) that orbits the Earth but has remained undetected by us? Are we actually ...
1
vote
3answers
130 views

How does gravity interact with a photon?

If photon is mass-less and gravity can interact only with matter, then how does gravity alter the trajectory of light?
1
vote
1answer
29 views

What to do after first year of amateur astronomy? [closed]

I have practiced astronomy as a hobby for a while now. I have an entry-level telescope (6-inch Newtonian). In addition to observing the night sky, I have been studying physics related to optics, ...
0
votes
0answers
31 views

material exchange between a planet and its host

Of the exo-planets found so far, there is one that can exchange material much with its host? How to prove that? Io may be a good example, but it is not a planet.
1
vote
1answer
45 views

Dark Matter Detection

A paper appeared at the arXiv.org (in April or May) claimed that the writers have found the gamma rays emitted by annihilation of dark matter in a satellite galaxy of the Milky Way by examining the ...
0
votes
0answers
33 views

Abbreviations for days of the week

Is there a set of standard abbreviations for the days of the week for use in astronomy? I couldn't find any reference to it in the The IAU Style Manual (1989).
0
votes
1answer
76 views

Question about total absolute magnitudes of galaxies - negative or not?

I have seen this in a couple of places, but when the authors in the paper - http://chandra.as.utexas.edu/~kormendy/kfcb-accepted.pdf - wrote: "All 10 of our ellipticals with total absolute ...
5
votes
5answers
1k views

What would the effects be on Earth if Jupiter was turned into a star?

In Clarke's book 2010, the monolith and its brethren turned Jupiter into the small star nicknamed Lucifer. Ignoring the reality that we won't have any magical ...
5
votes
1answer
112 views

Has the great Andromeda Galaxy ever collided with any galaxies?

We know that the Andromeda Galaxy is moving towards the Milky Way and vice versa, so there will be a collision. Because of the vast space between the stars as they are defined will not themselves ...
1
vote
2answers
161 views

Why doesn't this paradox disprove (some) multiverse quantum gravitational theories?

As I understand it, one theory of the multiverse is that there are an infinite number of universes separated by small distances in other (than our observable 3/4) dimensions and that gravity is weak ...
2
votes
2answers
124 views

Why is the moon a fuzzy, white ball?

I currently own a telescope, I'm an amateur astronomer and currently just trying to view the moon. I own the Celestron PowerSeeker 70AZ. Link for information on the telescope: ...
2
votes
0answers
40 views

If nothing can pass the schwarzschild radius, how can black holes even start? [duplicate]

From our point of view, no object can fall into a black hole in finite time. The object will seem to be more and more red-shifted to us, but it will never quite pass the schwarzschild-radius / event ...
2
votes
1answer
290 views

If oxygen was abundant in Neptune, would there be combustion?

Since Neptune/Uranus have high percentages of methane, wouldn't it be highly likely that there will be combustion (triggered by the lightning storms or any other factor) if oxygen was abundant? And ...

15 30 50 per page