Most Popular
1500 questions
32
votes
4 answers
What will succeed the Arecibo Observatory?
Just a few minutes ago, I got a notification from Space.com stating that the Arecibo Observatory will be, sadly, decommissioned due to extensive damage to its structure. So, with the loss of one of the world's largest telescopes, we will be put at a…
WarpPrime
- 6,653
- 1
- 24
- 61
32
votes
1 answer
If two white dwarfs collided, would they become a star?
Would the temperatures during such a collision be able to ignite nuclear fusion, bringing the dead star back to life? If so, would it only be able to fuse for a short time before running out of fuel, or would it turn into a full-fledged star?
Gliese
- 831
- 6
- 10
32
votes
3 answers
Is the Sun visible from Proxima Centauri to human eyes?
I know that the light coming from Proxima Centauri is not bright enough to make it naked-eye visible from the Earth. Is the Sun naked-eye visible from Proxima Centauri?
Patrick
- 423
- 4
- 5
31
votes
3 answers
How far is the Earth/Sun above/below the galactic plane, and is it heading toward/away from it?
How far is the Earth/Sun above/below the galactic plane, and is it heading toward/away from it?
We know the Sun is orbiting the galactic center every 225 million years.
But how far are we from the galactic plane, and is the inclination of the plane…
jmarina
- 1,016
- 1
- 9
- 10
31
votes
1 answer
Why did it take so long to invent telescopes given glass was used 4000 years ago in Mesopotamia?
Is a telescope difficult to make? Does glass have to be polished and shaped very precisely? Or is a device using two or more lenses to magnify things just not obvious?
user50918
31
votes
2 answers
Why is one picture of this star blue with red, and the other red with blue?
Someone just retweeted a NASA tweet onto my timeline, and it includes two images, allegedly from the same star that was in the process of dying, taken by the new space telescope, side by side:
I don't quite understand what I'm looking at though. If…
Tinkeringbell
- 419
- 4
- 6
31
votes
1 answer
Trying to identify something I saw in the sky
I'm trying to identify something I saw in the sky. This occurred in central Virginia (Louisa county), US on Sunday at around 2:15 AM EST. It started as a ring of what looked like smoke, high in the sky. The ring got gradually larger. Then a small…
robotcookies
- 413
- 3
- 6
31
votes
6 answers
Why does light accelerate instantaneously to c, while no other phenomena do it?
In physics, it always takes some time for a particle to move from rest to some speed.
However, photons (light particles) accelerate instantly from zero to c. How? (A visualization would be helpful.)
AnnexRemotelearn
- 425
- 1
- 4
- 5
31
votes
1 answer
What's the map on Sheldon & Leonard's refrigerator of?
In the Big Bang Theory, there's a map on Sheldon & Leonard's refrigerator throughout the entire show It has false-color shadings of various kinds, with prominent craters, and so is presumably of some non-terrestrial body, perhaps Mars, the moon, or…
scottef
- 411
- 4
- 4
31
votes
3 answers
What keeps galaxies together?
The super massive black hole at the centre of Milky Way has a mass of about 4 million times that of our sun. Is this enough to keep the entire galaxy together, is it this black hole which keeps the galaxy together? I did read that there are also…
O S
- 466
- 1
- 4
- 9
31
votes
2 answers
Which of the planets would be detected if they were exoplanets?
An (almost-)omnipotent being selects the solar system, presses Ctrl+C, and then Ctrl+V several times, creating copies at distances of 5, 500, 50.000, and 5.000.000 light-years away. All in a direction where the instruments we have are currently…
Ink blot
- 421
- 4
- 8
31
votes
1 answer
Why do planets and satellites in the Solar system look so wildly different if they came from more or less the same matter?
First, the planets. We have Mercury, which is rocky, no atmosphere. But then we have Venus, which is completely different: thick atmosphere, very hot, geologically active. Then Earth - blue, full of water. Mars, the opposite: red like nothing else.…
stackzebra
- 1,429
- 8
- 14
31
votes
2 answers
What is the current accepted theory as to why Venus has a slow retrograde rotation?
According to this NASA overview, the planet Venus is unique (amongst the major planets), Venus has a slow retrograde axial rotation, taking 243 Earth days to make one rotation (which is longer than its orbital revolution).
What is the current…
user8
31
votes
3 answers
Why can't we observe the Oort cloud with a telescope?
The Oort cloud is a hypothetical structure based on our observation of long-period comets. There are currently proposals to design probes to confirm the existence of the Oort cloud.
Now, sending a probe would have other benefits, but why can't we…
called2voyage
- 6,312
- 1
- 32
- 62
31
votes
2 answers
Is this photocomposition of Andromeda's galaxy and the Moon accurate?
I recently saw the below image circulating around twitter/Facebook/reddit. It is titled "Andromeda's actual size if it was brighter":
One of the comments provides a link to another comparison provided by APOD, and the following comment mentions…
Federico
- 395
- 1
- 3
- 11