8
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2answers
79 views

Do the orbits of planets change sometimes?

Do planets sometimes wobble and get off their paths? What if an asteroid were to hit it?
8
votes
2answers
206 views

Are there a lot of collisions between stars in the core of the galaxy?

I'm reading on Wikipedia about Halo Stars that orbit the center of the galaxy at a high inclination away from the plane of the Milky Way. It seems that at some point, these stars must dive back into ...
8
votes
1answer
96 views

Blowing up an asteroid/comet really potentially worse?

Often on television shows and in articles I see it mentioned that it'd always be bad to blow up an asteroid or comet because then the energy would just be spread out and cause even more damage. ...
8
votes
1answer
100 views

How do scientists know that a rock found on Earth came from Mars?

There are many documented cases of meteorites being reported as from Mars. http://en.wikipedia.org/wiki/Allan_Hills_84001 While I can understand that it's possible to know if a rock originated as a ...
8
votes
1answer
92 views

How do we calculate the escape velocity of galaxies?

How do we calculate the escape velocity of galaxies? Do we have to know the total mass? What is the escape velocity for Milky Way?
8
votes
1answer
745 views

Finding the solar noon based on longitude and latitude?

Please could someone advise the best method of finding the solar noon based upon location? http://pveducation.org/pvcdrom/properties-of-sunlight/suns-position The stuff on here has been helpful but ...
8
votes
1answer
60 views

Are any Pluto-sized objects remaining to be discovered in the Kuiper Belt?

An object approximately the same size as Pluto, Eris, was discovered only 8 years ago (in 2005). Are there any Pluto-sized objects remaining to be discovered, and if so, how far away from the Sun ...
8
votes
1answer
152 views

What is the current accepted theory for Neptune's immense wind speed?

According to "Neptune: The Other Blue Planet in Our Solar System" (Choi, 2010), Neptune, despite its great distance from the sun, is the windiest planet in the solar system, with winds reaching ...
8
votes
2answers
220 views

If the Wow! signal was not directed at us, then where?

We probably all know the Wow!-Signal, happened on August 15, 1977. Assume that it wasn't meant for us. What was it pointing at then? The signal at that time came from RA= 19h25m31s ± 10s or 19h28m22s ...
8
votes
1answer
82 views

Mechanisms of binary/multiple star formation

What are mechanisms of binary/multiple star formation in different mass ranges (low, intermediate and high stellar masses)?
8
votes
2answers
146 views

How often does Earth cross the galaxy regions with higher supernovae activity?

According to Summa Technologiae, a book by a Polish author Stanisław Lem that based his science fiction novels on scientific research of the era, the Earth crossed in the moment of forming of life the ...
8
votes
1answer
60 views

How was Io not torn apart by tidal forces during its formation?

Jupiter's moon Io is arguably one of the most volcanically active bodies in the Solar System. The reason, according to NASA's page Scientists to Io: Your Volcanoes Are in the Wrong Place is believed ...
8
votes
1answer
194 views

How do we detect if a planet has a liquid core?

In case of Earth, we have many hints about the internal structure of our planet, from what I know, the most important of which is analyzing seismic waves. Do we have any instruments to detect if ...
8
votes
2answers
62 views

How can the orbit of a Kuiper Belt Object be differentiated from the transit of a rogue planet?

Related to the question "Are any Pluto-sized objects remaining to be discovered in the Kuiper Belt?" and the fact that most of the Kuiper Belt objects have very elliptical orbits, the question begs, ...
8
votes
1answer
86 views

What is a White Hole?

White holes are purely hypothetical at this point and are considered only because it is assumed something like it could exist as the balance to black-holes. Reading this article seems mostly writers ...
8
votes
1answer
106 views

How many galaxies disappear beyond the Hubble Bubble horizon every year now?

The accelerating expansion of space means that the space between us and far away galaxies expands faster than light can travel through space. There is a horizon of possible observation beyond which ...
8
votes
1answer
85 views

What implications do younger Earth and Moon have on Late Heavy Bombardment genesis hypotheses?

The Late Heavy Bombardment (LHB) or the Lunar Cataclysm is when the inner solar system, including the Earth and the Moon, underwent multiple and sustained heavy impacts early in their history (around ...
8
votes
1answer
68 views

What is the current accepted theory as to why Mercury, despite its size, has a similar density to Earth?

According to the NASA web page overview about Mercury, despite the planet being just a bit larger than our moon, it's density is about 98.4% of Earth's. This high density suggests a comparatively ...
8
votes
2answers
83 views

Adjust axis labels in ds9

How can I adjust the axis labels in ds9? I'd like to have something like: So far I only managed to get floating points (tl h%f3): or the leading hours are missing (tl h%f1 m): Edit: I tried ...
8
votes
1answer
67 views

How Does Cosmology Constrain the Number of Neutrino Species?

I've asked this question already on the Physics SE, but I felt it would be worth posting here as well. I know that based upon theories of structure formation cosmologists can constrain the sum of the ...
8
votes
1answer
63 views

How far apart is the dust in the Sombrero Galaxy's dust lane?

In his answer to this question, TildalWave made this remark: I think that first, we have to properly appreciate the size of the Sombrero Galaxy. It is roughly 50,000 light years (15 kilo parsecs) ...
7
votes
4answers
164 views

What will a lunar eclipse look like from moon?

What will a lunar eclipse look like from moon? Will earth become a completely dark circle?
7
votes
2answers
940 views

Can two comets travel together as one?

If two comets come together in space, will they bounce apart, merge into a single body, or could they travel together through space, either touching or orbiting a shared center of gravity?
7
votes
2answers
1k views

Why can we sometimes see the moon during the day?

At some points in the year, the moon at my location can be clearly visible during the day. Why is this? If it is any help, I live in Alberta, Canada.
7
votes
2answers
189 views

Why do the Pleiades look clearer when viewed indirectly?

I've noticed that the Pleiades look bright in the sky, but when I look directly at the constellation, it suddenly goes dim and it's more difficult to make out the individual stars. Why does this ...
7
votes
3answers
98 views

What qualifies as a good place for stargazing, i.e. with least light pollution?

I know that minimal light pollution is a must for stargazing, and a place which is away from civilization is better. Does altitude of a place matter for light pollution? Does it affect the quality ...
7
votes
1answer
1k views

Are satellites orbiting around earth visible to the naked eye?

I was just lying under the sky trying to possibly see some meteorites, unfortunately never seeing any I might add, but I saw three objects all moving at about the same speed( all at different times). ...
7
votes
4answers
2k 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 ...
7
votes
2answers
497 views

Why don't we see the galaxy center?

When we look at the sky, and see the Milky Way, we mainly see a band, with no real center. On a more accurate picture we can guess the center of the galaxy (see this picture), but we still don't see ...
7
votes
1answer
160 views

Is it possible for a moon to orbit a planet floating free in the galaxy rather than orbiting a star

This article got me thinking, can a planet hold a moon in orbit if it is just floating in the galaxy by itself not as part of a star system? Can a celestial body even qualify as a planet if it is ...
7
votes
2answers
93 views

Does the Moon Have Enough Water for Robert Zubrin's Mars settlement Plan To Work?

In Robert Zubrin's "The Case for Mars" he outlines a plan to settle Mars by(among other things) finding water and using electrolysis to break up water into Hydrogen and Oxygen. This provides fuel for ...
7
votes
3answers
196 views

Do parallel universes exist?

Do other universes like ours exist? If they exist, how do we know that they exist when we have even not seen the ends of our own universe?
7
votes
3answers
178 views

Can impact craters on the moon act like giant radio telescopes?

Could large craters on the moon be used as reflective lenses for radio signals? Acting like a large radio telescope reflecting radio waves to a satellite positioned over the crater.
7
votes
2answers
97 views

How were the designations of “North” and “South” applied to the hemispheres of Mars?

How was it decided which hemisphere was North and which hemisphere was South on Mars? Clearly, the designations "North" and "South" apply only to the hemispheres which contain the axis of rotation at ...
7
votes
1answer
234 views

Is it possible that all dark matter is made of rogue planets (free-floating planet)?

Is it possible that all dark matter is made of rogue planets (free-floating planet)? (and other stuff like asteroids or meteoroids)
7
votes
1answer
125 views

Which is the closest exoplanet to Earth?

The closest star to Earth (after the Sun) is well-known: Alpha Centauri, 4.3 light years away. But what about the closest exoplanet to Earth, outside of the Solar System?
7
votes
2answers
80 views

What is the current estimation for how much time the Sun will function properly?

Eventually, the Sun will run out of fuel, go dark, and other bad things will happen. About how much long is it predicted that we will have a sun functioning as it is currently?
7
votes
3answers
534 views

Do we expect life to develop only in certain regions of the galaxy?

If I understand correctly, the Earth lies in an area of the galaxy - the "local bubble" - that is relatively free of dust and gases and where no new stars are being born. What is the current theory ...
7
votes
2answers
144 views

Is the Hubble Ultra-Deep Field image representative of the entire sky?

The Hubble ultra-deep field image is a photograph of an area of sky equivalent to a 1mm x 1mm piece of paper held a metre away from the eye (one thirteen millionth of the entire sky). It contains an ...
7
votes
2answers
78 views

Recommendation for introductory cosmology text

I am looking for recommendations for an introductory text (or texts) on cosmology on the advanced undergrad or beginning grad level. I am coming from primarily a physics undergrad background (doing ...
7
votes
2answers
499 views

Are Barlow Lenses Good For Deep Sky Observing?

I'm using a 750mm (focal length) by 150mm (aperture) newtonian reflector and I've been curious about using Barlow lenses on deep sky objects. Some of the astronomers at my local observatory say that ...
7
votes
1answer
65 views

Why does mars appear to retreat across the sky?

If you plot the movement of mars across the Earth's sky it appears to move back on itself during its orbit. Why does it appear to have a loop shape from Earth?
7
votes
1answer
95 views

How fast do we travel through space?

Could someone give the rough estimates of speeds of our travel through space? I can easily find the two nearby ones: Earth's own rotation - depending on latitude, up to 40,075 km/24h = 463 m/s ...
7
votes
1answer
120 views

Can we see the Big Bang happen if we look far enough?

The observable universe is constantly expanding as more light from the Big Bang reaches us. This light has been travelling for billions of years, so we are looking at the universe as it was a few ...
7
votes
2answers
132 views

With gravitational lensing, is it possible to mathematically compute the correct image of the galaxy that is being distorted?

There's been another report of gravitational lensing in the news. Wikipedia has a good image of an example of gravitational lensing taken by the Hubble Space Telescope. This brings me to wonder ...
7
votes
2answers
292 views

Why haven't Earth and Venus got any tiny moons? Or have they?

Why haven't some meteoroids gotten caught in Earth's or Venus' orbit? AFAIK most meteors are tiny fragments from comets. Shouldn't some comet tail sometime have passed Earth orbit at velocities ...
7
votes
3answers
206 views

How would we detect an Earth doppelganger planet?

With our current technology, or technology available in the near future (up to 2025), how would we detect a planet exactly like our own, and how close would it have to be to be detectable? Which ...
7
votes
2answers
478 views

How long until we cannot see any stars from other galaxies?

Since all the galaxies are moving further away from each other at a faster and faster rate, eventually we won't be able to see stars from other galaxies. How long until we can't see stars from other ...
7
votes
1answer
55 views

How does interstellar matter density vary?

Answer to my question partially answers this one, about density of intergalactic matter and matter within galaxy: But it is mostly a hot, ionized void. How void? The density of the intergalactic ...
7
votes
1answer
95 views

What is the Lyman Alpha forest Used For?

The Lyman-alpha forest is an interesting feature found in the spectra of sufficiently distant objects. This series of absorption lines extends over a range of frequencies, and are a result of the ...

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