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1500 questions
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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 galaxies disappear from us.
At what rate do…
LocalFluff
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What is the likelihood of the existence of unknown elements in the Solar System?
What's the chance that there might be undiscovered chemical elements in the Solar System - either on planets or around the Sun or on asteroids of the Oort-cloud?
Zoltán Schmidt
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Are there any gaps in the range of gravitational wave frequencies we can detect?
We have LIGO and other earth-based interferometers for detecting high-frequency gravitational waves, we're going to have satellites in orbit around the sun for low-frequency waves, and we have a pulsar timing array for very low frequency waves. Are…
zucculent
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How would a cooled down neutron star look when illuminated?
Assume we have a neutron star that has cooled down so far that it no longer emits visible light. If we illuminate it with a powerful external light source, what would it look like? Would it reflect light, would it scatter it, would it re-emit it…
cuckoo
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What is the most accurate measurement of the Astronomical Unit?
I am using the Earth-Sun distance to teach kids the usefulness of trigonometry. This site is helpful.
But one of the more engaged asked what the most accurate measurement is. After some research, I found that elapsed time measurements of reflected…
aquagremlin
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How would the pocket cellular clock work?
In a museum in Lviv, I saw a pocket cellular clock. I don't have a photo, but it was a small disc that had 2 or 3 filaments in it which were pointed at the stars (one of them was Andromeda, I think). Through analyzing the position of the stars it…
Danubian Sailor
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Why are there not yet any instruments dedicated to registering time dilation caused by passing gravitational waves?
Why are there not yet any instruments dedicated to registering time dilation caused by passing gravitational waves?
Wouldn't it be interesting to augment LIGO/Virgo capturing of space distortion with simultaneous capturing time dilation (both caused…
Alex
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Undiscovered dwarf planets
Scientists think there may be dozens of undiscovered dwarf planets in the Solar system. What I find intriguing is that, we have been able to detect distant galaxies and clusters, locate supermassive black holes...but how is it that dwarf planets in…
Ambica Govind
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Using parallax to find distance to the moon
I want to use the parallax method (from scratch) to find the distance between the earth and the moon. To get a significant parallax, I need to choose a large baseline. I live in India and my friend in the US and so the baseline will be about…
Young Kindaichi
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Formation of elements in the Sun other than helium
I just learned that the Fraunhofer lines of the Sun's spectrum indicate that the Sun contains various elements other than just hydrogen and helium (for example, Na and Fe) but don't the Sun's p-p chain reactions only involve hydrogen and helium? So…
Jack the Ranger
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Can there be planets, stars and galaxies made of dark matter or antimatter?
We know that the universe has more dark and anti matter as compared to normal matter. Can there be dark matter galaxies or antimatter galaxies?
Dark Knight
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What caused this mysterious stellar occultation on July 10, 2017 from something ~100 km away from 486958 Arrokoth?
In 2017 a series of stellar occultations by asteroid 2014 MU69 "Ultima Thule" now officially named 486958 Arrokoth were timed in order to obtain better orbital information before the New Horizons flyby and to look for additional large chunks of…
uhoh
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Is the surface of TrES-2b actually dark?
The exoplanet TrES-2b is known as the darkest planet ever found, reflecting <1% of the light that hits it.
What does it mean in respect to the surface? What would we see below the atmosphere of this planet? Is it a "shadow planet" with an atmosphere…
Zoltán Schmidt
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Is there a name for a planet and its moons/satellites?
I'm wondering if there's a name that encapsulates the concept of a planet and the objects that orbit in its gravity. There's a solar system that encapsulates a star and its multiple planets and other objects, but I don't think that "solar system"…
Edward Loveall
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What was the absolute limit to the possible sizes of the first stars formed from "primordial material with no metals"?
This answer to Why don't or (can't) stars be more than 325 or so times the mass of the sun? What limits their size? includes the following:
...The upper limit you refer to is for compositions similar to the Sun. For stars born in the distant past…
uhoh
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