Astronomy Stack Exchange
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1500 questions
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Which stars did the Sun form with?

The Sun formed 4.5 billion years ago, in a molecular cloud. I assume that there were other stars in the vicinity (as is common in molecular clouds). Which stars are they? Where are they now? Are they similar to the Sun?
HDE 226868
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Is Earth's orbital eccentricity enough to cause even minor seasons, without axial tilt?

I was reading the answers to this question about an exoplanet having seasons without axial tilt, and several responders mention that orbital eccentricity could cause a similar effect, but that the orbit would need to be "very eccentric," as opposed…
Nerrolken
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Questions about spiral galaxy arms

I have 2 questions related to spiral galaxies. Firstly, how did the arms form? Why would the stars accumulate into those specific areas? And secondly, why are they still intact? The inner parts of the arms must be revolving more rapidly than the…
stanley dodds
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How do/did we figure out that planets move in orbits?

I've learned that planets move in orbits around the Sun, but I really don't know how I would come to this conclusion myself. I've only seen planets in the sky a couple times (knowingly), and I am curious how we know for certain today that planets…
Jackson
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Affordable night sky photography

As an amateur with limited budget, I'd be interested in taking photos of the night sky, trying to capture more detail than human eye armed with a lens of comparable parameters to what I have in my camera normally could see. I doubt I'd ever get down…
SF.
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Could we (Earth, Humanity, Solar System) be falling into a black hole?

With the expansion of the universe, all objects far away from us appear to be moving away (ie: exhibit Redshift). With distance, this acceleration / redshift also seems to increase (~73,000 (m/s) / (1,000,000 parsecs)). The general trend across…
G. Putnam
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Is it possible to have satellites (natural or not) orbit the same celestial object in different directions ? (clockwise, counterclockwise)

Is it possible to have satellites (natural or not) orbit the same celestial object in different directions, or is the orbital direction dependent on the celestial object's spin? Also, is the direction of spin of a celestial object dependent on how…
Demis
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Should I focus more on Aperture or Focal Length for a telescope?

Let's assume there are three types of telescopes with the following specifications: Telescope Aperture Focal Length -------------------------------------------------------------- Example 1 …
www
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Could we detect the light of cities at night in other solar systems?

Would it be possible to see electric lights on distant planets using current telescopes?
user48394
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Why is time referred to as "The" capital T 4th dimension?

Often you hear people say "time is The 4th dimension". What confuses me is that people talk about "The 4th" dimension as if it's a specific thing and I don't understand why. What I mean by that, is that I can plot the position of a point in 3D space…
Michael Seltenreich
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How many undiscovered planets might be in our solar system?

Some people talk about the possibility of a planet 9. Could there be a planet 10 or 11? How many undiscovered planets could there be in our solar system?
Eric Coulthard
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Has the small meteorite that hit Webb done a lot of damage?

I read on the web about Webb: A tiny meteoroid struck the newly deployed James Webb Space Telescope in May, knocking one of its gold-plated mirrors out of alignment but not changing the orbiting observatory's schedule to become fully operational…
Felicia
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Is it possible to have a stable 3 body system that orbits in a perfect circle?

I.e. a system that has 3 objects of equal mass, rotating around the system's center of gravity like so: Please excuse the crude drawing, but I've just been reading The Three-Body Problem book by Liu Cixin and it made me wonder if such a system like…
ROODAY
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What's the percentage of strange matter inside a star at any time?

Is there any amount of strange matter (or "top matter"?) inside stars? By strange matter I mean matter made out of flavours of quark other than up/down.
Alexandre
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What's the difference between minutes and arcminutes?

I read in trigonometry class that 1 minute is equal to 1/60 degrees. So, 'minute' is an angular unit. But also 'arcminutes' are used to measure seperation between celestial objects and also equals to 1/60 degrees. Are they any similar? If not, then…
Tanya
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