1
vote
2answers
39 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. ...
0
votes
1answer
11 views

about H$_\alpha$ and H$_\beta$ lines in stellar spectra

Generally there may be some line ratio between the two lines. If H$\alpha$ is strong, it is quite possible we can see H$_\beta$ too. Is it possible we can see H$_\beta$, but can not see H$_\alpha$? ...
2
votes
1answer
33 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
102 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
18 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 ...
5
votes
4answers
412 views

Can magnetism escape a black hole?

I know light, and practically nothing but gravity can escape a black hole. My question is: can magnetism escape a black hole? A couple things that convince me it can are: Jupiter's magnetic ...
1
vote
1answer
22 views

How to run MOOG on OS X Yosemite

By what process can a user running the latest version of OS X Yosemite execute MOOG with $MOOG in bash? Due to the removal of 32bit libraries in OS X 10.7+, the ...
3
votes
0answers
13 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
35 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 ...
3
votes
2answers
57 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
votes
0answers
25 views

How clearly would I be able to see a galaxy with the naked eye if viewed from a “close” distance?

In images of other galaxies they look very bright and vivid against the blackness of space (example). If I was located a few tens of thousands of lightyears away from a galaxy, would I see something ...
0
votes
1answer
22 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 ...
0
votes
0answers
27 views

Can we spot a gray-goo exoplanet?

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 ...
-1
votes
0answers
27 views

How is expansion different from contraction? [on hold]

For example, two space ships cross the event horizon. There would be a period of time where space is 'expanding' correct? I mean, the lead ship would always be accelerating faster than the one ...
0
votes
1answer
81 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
56 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
26 views

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

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 ...
0
votes
0answers
20 views

How does the Higgs field relate to the Yang-Mills fields and gauge theories in general? [on hold]

It is very confusing. Is there an easy explanation that will tell me how these differ or what the difference is?
0
votes
0answers
36 views

Why did Kepler Telescope's Reaction Wheels fail? [on hold]

I was just reading about the Kepler telescope and how it uses reaction wheels to finely control orientation, much like Hubble. Reaction wheels seem like very simple devices with only one moving part: ...
-1
votes
1answer
43 views

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

i was retrieving a some personalities birthday date through computer programming when i retrieve a person's birthday the result was ...
-1
votes
0answers
20 views

How can I use Buchdahl's equation of state with analytic solutions to Einstein's equations to solve for the mass-radius relation analytically? [on hold]

I am trying to model a neutron star as a polytrope based on the non-relativistic equations of stellar structure. Post continued below since I have less than 10 reputation.
1
vote
1answer
110 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 ...
-1
votes
3answers
54 views

Does the sun move

I'm curious, does the Sun actually move? The concept behind the question is, if you wear a shirt and you move, does the shirt actually move? Like the Solar system orbits around the Milky Way, but does ...
0
votes
1answer
78 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 ...
1
vote
2answers
75 views

What causes horizontal and vertical lines coming out of pictures of stars?

What causes the horizontal and vertical lines coming out of pictures of stars, instead of them simply appearing as circles? For example, this picture from Wikipedia: .
0
votes
2answers
80 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
votes
0answers
17 views

Dull, Red, Slow Moving, Meandering Meteors?

+Localfluff I've seen three to date. One 2-3 years ago the last two March 2015 5 minutes apart! Naked eye 11:00pm or so from Aviemore area of Scotland. First and biggest (pinkie nail at arms length) ...
1
vote
1answer
105 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!!
1
vote
2answers
95 views

How to calculate conjunctions of 2 planets

So, the recent conjunction of Jupiter and Venus seems to have spawned lots of excitement over this "rare" event. But what I can't figure out, is exactly how rare it is. And I've seen such conflicting ...
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
66 views
+150

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
40 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
341 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
150 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
115 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
24 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
146 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
61 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
136 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
35 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
132 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
49 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
30 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. ...
1
vote
2answers
48 views

How/where to check where the Sun is (constellation)?

I would like to check in which constellation the Sun was in at some time in the past, any recommendations how to do that?
1
vote
1answer
45 views

Is the diameter of the observable universe a relative quantity?

The diameter of my observable universe is 90 billion ly measured in proper distance. But isn't lenght a relative quantity in the theory of Relativity? Could an observer moving at a different velocity ...
2
votes
2answers
107 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
0answers
27 views

How far away would a supernucleus comet be visible?

If an instrument like LSST quickly spots something as soon as it reaches magnitude 24½, how far away would a 60km first-time visitor from the Oort cloud be when it is spotted? I'm thinking that a ...
0
votes
1answer
39 views

What is the projection of Earth's axis on the sphere with the Sun in center (see explanation)

Seems like it is the most convenient SE community for this question.. Imagine the sphere, witch center is the Sun and radius is, say, ~1.5 distance from Sun to earth (in arbitrary time, precise ...
0
votes
1answer
17 views

When will the next summer solstice and a full moon coincide? What day?

What day will the summer solstice and full moon coincide? As far as I know the next time will be in 2016. I would like to know what day.
0
votes
2answers
50 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 ...

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