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1500 questions
22
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Why is the sun not directly overhead at noon on the March equinox at N 0° 0' 0.00" E 0° 0' 0.00"?
I'm trying to teach my sons the difference between using azimuth-altitude coordinates and ecliptic coordinates. In the course of setting up some demonstrations, using Stellarium, I set my location to N 0° 0' 0.00" E 0° 0' 0.00", the time to GMT, and…
adam.baker
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Are there non-rotating objects in the universe?
All celestial bodies I can think of rotate. The sun, the planets, the moon, the galaxies, clusters of galaxies, the supermassive black hole at the center if the Milky Way, accretion discs, etc. It would be very strange if they didn't. They couldn't…
Deschele Schilder
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22
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Why was there a gap in the number of asteroid detections between 1807 and 1845?
The first asteroid, Ceres, was discovered in 1801, although it wasn't called an asteroid yet. Pallas, Juno and Vesta were discovered shortly after. Then no new asteroids were discovered for 38 years, until Astraea in 1845 when the rate of discovery…
usernumber
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Does anything orbit the Sun faster than Mercury?
Mercury's orbital period around the Sun is about 88 days. Comets and other things have gotten closer to the Sun than Mercury does. But has there ever been an asteroid or some other body discovered that has a shorter orbital period? Are there…
Connor Garcia
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Please check my Mars photo
Hi built my own newtonian telescope for the first time. Up until that point I had never used a telescope.
Can you please look at the photos attached and tell me if this is what Mars should look like as I'm disappointed somewhat.
Specs are as…
Edd
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22
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3 answers
Why does a planet rotate and revolve?
Why do planets rotate and revolve in the universe?
M.Tarun
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When was it worked out/discovered that our Sun can't go supernova?
As the title says, when did we realise with reasonable confidence that our star is not going to be going out in a supernova blaze of glory?
I ask because a while ago I read "The Songs of Distant Earth" by Arthur C. Clarke which was from 1986 (but…
Wiggo the Wookie
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Where do we define the "surface" of a gas planet?
Since gas giant consist of most gas components, where do we establish their "surface"?
My take is basically to take the limit in which all light is opaque. For example, in this photo:
The surface, then, will be the limit of the black blackground…
Carlos Vázquez Monzón
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What would an asteroid inside of Mercury's orbit be called?
The first Vatira asteroid has been discovered. This makes me wonder if there is already a name for the hypothetical class of asteroids that orbit entirely inside of Mercury's orbit. It wouldn't be the first time that an astronomical class is named…
usernumber
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Do we know a star that is similar to the Sun when it would be a red giant?
In about 5 billion years the Sun is predicted to become a red giant and have more than 200 times its current size, reaching a radius of about 5 AU when largest.
I wonder what spectral class the Sun would have then, I think somewhere from M1III to…
user30007
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5 answers
How far away are the events that caused the gravitational waves that have been detected?
A certain number of gravitational wave events have been detected. Is it possible to know how far away the mergers that caused those gravitational wave events are?
usernumber
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22
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1 answer
Are stars expected to become dimmer before a supernova?
With the recent news about the "fainting" of Betelgeuse and the speculation that this might be a precursor to a supernova, I'm wondering if there is any theoretical/observational basis for this interpretation, or whether this is a case of reading…
user24157
22
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2 answers
What is the name of meteoroids which hit Moon, Mars, or pretty much anything that isn’t the Earth?
A meteorite according to the Oxford English Dictionary is
A piece of rock or metal that has fallen to the earth's surface from outer space as a meteor.
But, meteors impact other planets. Are they still meteorites? Or is there another word for…
EDL
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22
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6 answers
Puzzling quotes from astronauts about earth size
I have no doubt that we have been to the moon. This question has nothing to do with a moon landing hoax. But, there are two quotes from two different astronauts regarding the size of the earth as viewed from the moon that are puzzling to me. Both…
Lambda
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What's the brightness of Alpha Centauri from Proxima Centauri?
Self-explanatory, but I would like a comparison as well. Is the light enough to see by? How disrupted will the pitch darkness on the spot opposite of the 'solar pole' be?
GoingFTL
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