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1500 questions
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Are rogue planets ever born in isolation?
I'm using the term "rogue planet" here loosely to mean anything of planet-level mass that is not orbiting around a star. Popular discussions of these objects always describe them as forming around a star and then being ejected by gravitational…
Mark Foskey
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Why is the track of the subgiant stage almost horizontal on the HR diagram?
It is stated that:
After the main sequence, as fusion weakens or stops in the core, outward radiation weakens. The helium core contracts and heats up. Gravitational energy is converted to thermal energy again!
The star will appear to cool slowly…
velut luna
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Why does the Earth's orbital eccentricity oscillate with a period of about 100,000 years?
This answer says:
Earth's orbital eccentricity varies over time from being nearly circular (low eccentricity of 0.0034) and mildly elliptical (high eccentricity of 0.058). It takes roughly 100,000 years for Earth to undergo a full cycle.
Why does…
uhoh
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Recommendation for introductory cosmology text
I am looking for recommendations for an introductory text (or texts) on cosmology on the advanced undergrad or beginning grad level. I am coming from primarily a physics undergrad background (doing some undergrad research on galaxy Lyman-alpha…
NeutronStar
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Was the progress of astronomy in the 1800s surprisingly slow, and if so why?
The 1800's was a century of fantastic scientific discoveries in chemistry, geology, biology, engineering and so on. Is it correct to say that astronomy did not keep up with this development? And if so, why? If not, what might be some main reasons…
LocalFluff
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Dark Flow: statistical limits on existence
Dark Flow has been thrown around as a term a lot lately, especially with the latest Planck results.
New Scientist reported last year that it was now statistically improbable, but the paper by Atrio Barandela mentioned in the article places doubt on…
christopherlovell
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What is the distance of the Earth's orbit around the Moon?
I realize the Earth and the Moon both orbit around their shared center of mass, and that in the case of the Earth and Moon this center is "inside" the Earth. However, I'm looking for an approach to determine the distance the Earth travels in one…
MT.
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What is the significance of the discovery of a pulsar flipping between radio and x-ray emissions?
This morning on the radio I heard about the discovery of a pulsar that, due to its proximity to a companion star, was flipping between a state where it emitted radio waves and one where it emitted x-rays. The flipping between states was said to be…
Gavin Simpson
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Can Liquid Water exist on Mars?
Outside of a specially crafts environment, could liquid water exist on Mars? Not some time in the distant past, but within the last few years. Mars' atmosphere is too thin for water to exist, right?
Perhaps if the water was mixed with salts or other…
Johnny
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How do we know how fast the surface of a neutron star is rotating?
I understand that we can count pulses in time, but how do we know that the magnetosphere is rotating along with the surface of a neutron star?
Can we measure the rotation of a neutron star in any other way like red-blue shifts? It should be pretty…
dllhell
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What is the current routine of modern astronomy?
With about all visible stars catalogued, measured and photographed it seems that chapter is closed. I realize currently while amateur astronomy is big on cataloguing all asteroids in the Solar System, the "Big Boys" are now primarily busy with…
SF.
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Why is twilight longer in summer than winter and shortest at the equinox
I recently decided to set my alarm clock to wake me up when it is "dark" out. In the end, I decided to set my clock to the earliest time that nautical sunrise is in my state (Illinois) and stick with that all year.
While doing some research for…
firebush
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Motion of the sun as observed from mercury
I recently found this animation which shows the motion of sun as observed from mercury. It seems as if the sun stops in between, retraces a bit and then continues towards the west. What is the reason for this strange motion? Is it because of…
Yashbhatt
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How do scientists know that a rock found on Earth came from Mars?
There are many documented cases of meteorites being reported as from Mars.
http://en.wikipedia.org/wiki/Allan_Hills_84001
While I can understand that it's possible to know if a rock originated as a meteorite. What I don't understand is how…
Reactgular
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Could asteroid 'Oumuamua actually be round?
News articles have mentioned that the recently discovered asteroid 'Oumuamua is theorized to be greatly elongated based on observations of brightness variation. However, this hypothesis seems to be based on the assumption that the object's albedo…
user2127894
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