# All Questions

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### If all stars rotate, why was there a theory developed, that requires non-rotating stars?

According to Penrose's research, a non-rotating star, would end up after gravitational collapse as a perfectly spherical black hole. However, every star in the universe has some kind of angular ...
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### Is tracking of unknown aerial vehicles beyond Earth atmosphere possible or even have been done already?

Afaik there are lots of deep space and Earth surroundings radar based asteroids observations. Now I've come across the USS Nimitz accident in 2004: there has been officially confirmed, now ...
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### Clearing the Neighbourhood: Definition of 'Orbital Region'?

I am trying to determine how wide a 'neighbourhood' a planet is expected to clear. However, the Wikipedia article on the matter provides no clarity, simply stating that a planet is expected to clear ...
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### How does the illumination of the sky from the sun compare to that of the moon?

I have trouble describing the questions but this is the best I can do. The sun lights up the sky, until it's about 18 degrees below the horizon. The moon also lights up the sky, and i'm wondering, how ...
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### Could anyone recommend a good book about the basics of astrophysics? [on hold]

I am sorry if a similar question has been asked before. I look at other questions but was not entirely satisfied. So, I am a Psychology student who would like to know more about the basics of ...
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### Assuming no light pollution, was “2C. 1406” ever visible to the naked eye?

Joseph Needham, in his Science and Civilisation in China Vol. III, claimed that there was an ancient record of a nova about three thousand years ago. As a result of private correspondences with a "Dr ...
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### Why didn't the parachutes on the Apollo 14 Command Module bump into each other? [on hold]

It seems like they would need some mechanism to keep them apart, but in this photograph I don't see anything telling, unless it's those small pilot chutes that are keeping them apart?
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Two questions: I read online that all objects emit the majority of their thermal radiation in the radio, and that this emission increases with temperature. Does this mean that all glowing bodies emit ...
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### Why is the Sun's Luminosity not equal to the Zero Point Luminosity?

I was doing some research and found that the zero-point luminosity was $L_\odot = 3.75\times 10^{28}$, while the sun's reported luminosity was $L_{Sun} = 3.828\times 10^{26}$, according to Wikipedia. ...
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### PSF magnification

I have a circular telescope pupil, a magnifying optic, and a detector. I am trying to calculate the point spread function as a function of wavelength. I am running into the issue that Python's 2D FFT ...
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### Why is our Sun hotter than UY Scuti?

As Wikipedia says the surface temperature of UY Scuti is 3,365 K and the sun is 5,778 K Why is the Sun hotter than a supergiant star like UY Scuti?
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### Why is Saturn invisible in this radar image of its rings?

The image below is from Radar imaging of Saturn’s rings Nicholson, P. D. et al., Icarus 177 (2005) 32–62, doi:10.1016/j.icarus.2005.03.023 and discussed further in this answer to How did Arecibo ...
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### Apparent Magnitude / Apparent Brightness relationship help

I'm a high-school student that is currently working on a project that describes, using mathematical notation and explanation, how scientists can find the values of each of the properties of stars, ...
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### Can dark energy or dark matter affect black holes

I was wondering if black holes are the greatest force of gravity how does other highly spoken about concepts such as dark energy or dark matter compare. Can a black hole absorb dark energy or dark ...
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### Control the behavior of a Black Hole

Is it possible to manipulate the size of a black hole or how a black hole behaves if scientists were able to synthesize hawking radiation on demand. That is, if I could find a way to imitate hawking ...
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### The dominance of Gravity vs Strength and its dependency on crater size

So I am trying to write a research paper (about 3700 words) for high school about the topic in the title or something similar. I have found the following information which I am struggling to ...
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### How does the Moon's gravity affect Earth's oceans despite Earth's stronger gravitational pull?

Given that Earth has a much stronger gravitational pull than the Moon, how does the Moon have any influence on Earth's oceans?
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### Local Bubble in space

Is the Local Bubble alone in space or is there another bubble similar to the Local Bubble in space, i.e., do we live in a special place or is this a more general phenomenon?
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### Are there any simulations of the Grand tack?

The BBC program with Brian Cox "The Planets" involved some description of the Grand Tack hypothesis to explain the current state of the solar system. This theory has Jupiter wandering through the ...
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### How does a Super-Massive Black Hole 'flare'?

This week we have read of evidence of the Super Massive Black Hole in the centre of the Galaxy 'flaring'. My understanding is that light cannot escape from a black hole. My question is: How does a ...
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### “Table of Astronomy's” depiction of the solar system models

This is going to be a follow up question to my question about the "Table of Astronomy" from yesterday, What is this “Table of astronomy” about?. I wanted to take a close look at the three depiction ...
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I'm looking for resources/texts to learn more about stars and things. I stopped studying physics when I was 15, so I'm pretty uninformed. However, I do have a pretty good maths background (UG courses ...
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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 ...
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### Can an Earth-like planet survive if our Sun went Supernova?

First, I would like to point out, yes, our sun does not have enough mass to be a candidate for Supernova, this is a scenario were our sun is though, and after the various life cycle stages of the sun ...
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### What is the hottest thing in the universe?

Straight from my 7 year old to you, exactly what it says on the cover: What is the hottest thing in the universe? To make it Stack Exchange-friendly, I'll add the following caveats: it should be ...
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### How did they estimate the mass of Sgr A*'s companion G2 without knowing what it was?

Gizmodo.com's Astronomers Spot Unprecedented Flashes From Our Galaxy's Black Hole mentions Sgr A*'s companion gas cloud G2. That Wikipedia article says: First noticed as something unusual in ...
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### Origins and most frequently used; perinigricon vs peribothron?

Gizmodo.com's Astronomers Spot Unprecedented Flashes From Our Galaxy's Black Hole mentions Sgr A*'s companion gas cloud G2 and that Wikipedia article uses the term perinigricon, but that mentions ...
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### Have more recent LIGO/VIRGO gravitational wave measurements narrowed down the speed of gravity further?

This answer to How precise are the observational measurements for the speed of gravity? says: ...in 2013 a Chinese group built a model using Earth's tides that helped them narrow it down. ...
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### Dark energy and light red shifting

When light is red shifted from distant galaxies, the photons have lost energy. When dark energy pushes objects apart, those objects have gained energy from a larger gravitational potential. Is the ...
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### Could anything consume a small black hole?

Whenever I read about black holes, it is normally involving how they devour anything that comes too close... regardless of how big anything is. But what if it were a really small black hole vs ...
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### Planets positions (azimuth, altitude) API

I'm looking for a simple API that will allow me to get positions of planets and the moon for a given date, location and time. Does anyone know an API like that? Any suggestions or alternatives would ...
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### What is this “Table of astronomy” about?

I found this picture while looking for some tattoo ideas and would like to know what these sketches are supposed to mean. Im especially interested in figures 1, 21, 53 and 56. It appears to be ...
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### Could Tabby's star be beamed by a neutron star's jet causing irregular star spots?

There have been some other questions here about what might cause the light curve dips of star KIC 8462852 as observed by Kepler Space Telescope. Here's one I haven't heard before: Could it be that a ...
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### The size of Copernicus’ and Ptolemy’s corrections

I understand that both Copernicus and Ptolemy needed epicycles, but one might assume that a heliocentric system would need much smaller corrections to account for the non-circular motion of the ...
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### What's the origin of Clyde Tombaugh's 9-inch Newtonian telescope?

Astronomer Clyde Tombaugh is shown in a now-famous photograph at the age of 24 with his "homemade" 9-inch Newtonian telescope in this image also shown in Elva R. O'Hara's Clyde W. Tombaugh: Farm Boy ...
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### Why do transits of Earth across the Sun seen from Mars follow a pattern of occurring after 26, 79 then 100 years?

According to this answer transits of Earth across the disk of the Sun as seen from Mars: The (Arthur C.) Clarke story is quite correct. Earth (and Moon) would transit the sun from the viewpoint of ...
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### Are red dwarfs (M dwarfs) known to be strong infrared sources?

If so, why? Are they known to be surrounded by large amounts of dust? Do they typically flare?
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### Relativistic Mercury orbit around the Sun

My question is the following,would the scalar of precession of Mercury orbit be the same if Mercury orbited Sun in the oposit direction?
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### Do gravitationally bound (e.g. orbiting) objects really resist the expansion of space?

Thinking about the expansion of space, it is commonly explained that gravitationally bound objects (like galaxies and galaxy clusters) will not be affected by the expansion of space (dark energy). I ...
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### Will intergalactic travel be impossible in roughly 15 billion years?

Even if we (or aliens somewhere in the universe living at that time) somehow invent something that can go just short of the speed of light, will intergalactic travel still be impossible in roughly 15 ...