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1500 questions
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Using the Sun as a Gravitational Lens
Can the Sun be used as a gravitational lens to achieve better telescopic viewing? Can this effect be practically used to view celestial objects?
Sarah Szabo
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Why doesn't Titan have a carbon dioxide atmosphere?
Earth's primitive atmosphere had large amounts of carbon dioxide, as did the ancient Martian atmosphere. Venus's current atmosphere is no exception either. So why does Titan have next to none of this compound? Is it due to its location with respect…
URIZEN
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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 large iron core (compared to the rest of the…
user8
12
votes
4 answers
Visible Stars in Andromeda Galaxy
So when I look at images taken of Andromeda, I see a lot of individual stars.
Image by André van der Hoeven
It seems to me that the actual individual stars that far away would be too small to resolve, even with a big scope like the Hubble. So, I…
Kerry Thomas
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Replenishing hydrogen in the core of the sun
How is hydrogen supplied to the core of the sun? Shouldn't the radiative zone prevent this? Shouldn't heavier helium fill the core? How much of the hydrogen can the sun fuse?
Bingohank
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Why does a hot cloud need more mass to collapse?
I was wondering why does a hot cloud need more mass to collapse than a cold cloud to form a protostar? Is it because there's a higher thermal pressure inside the hotter cloud than it is in a colder one?
space nerd
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Why aren't there blue elliptical galaxies or yellow spiral galaxies?
Elliptical galaxies are universally old and yellow; about three-quarters of all ellipticals have no significant star-forming gas or dust left, and even the quarter or so of ellipticals that are still forming stars do so at much lower rates (and with…
Vikki
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How many meteorites have been found some place other than Earth? Where is an authoritative list maintained?
Backgound:
After seeing this tweet by astronomer Kacper Wierzchoś about our not-so-new but at least newly-discovered "mini-moon" I scrolled down and saw the tweeted image below.
The object is the known short-period comet 114P/Wiseman–Skiff. The…
uhoh
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How long do the phases of sunset take?
How long does it take from the moment the Sun star 'touches' the horizon, to the time it totally disappear? (I'm not talking about the radiation (rays), but just about the appearance of the star by itself. I don't care of the rays). If I were near a…
Reckless Glacier
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What alternative facilities would be available in the event of JWST being destroyed?
Unfortunately, space launches can and do go wrong. Suppose that after all the delays and budget overruns, the launch of the James Webb Space Telescope fails and the telescope becomes a cloud of very expensive shrapnel raining into the sea.
Are there…
user24157
12
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2 answers
How (the heck) does Astrometry.net work?
What magic is this?
This answer to my question Astronomy detective question: what part of the sky are these photos of? What are a few of the stars? nails it, and the output (linked there) contains the following images along with a whole lot more…
uhoh
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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?
user96
12
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3 answers
What do the fusing 'onion layers' of a pre-supernova star look like to scale?
I'm sure we've all seen the diagrams of various layers of element fusion from hydrogen to silicon in a star that's just about to go supernova.
(Picture from courses.lumenlearning.com)
I suspect these pictures grossly exaggerate the relative radii…
Ingolifs
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12
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What will future populations of stars be like?
As stars slowly using up hydrogen and ejecting heavier elements into space, the future stars will form from nebulae that are more metal and helium rich.
The question is: how does the increased ratio of helium and metals affect star formation and…
Calmarius
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How did Arecibo detect methane lakes on Titan, and image Saturn's rings?
This answer to Farthest distance to a solar system object that's been measured by radar? mentions that Saturn's rings, and the Uncover Travel post Arecibo Observatory, Puerto Rico – The World’s Largest Radio Telescope For Over 50 Years…
uhoh
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