# All Questions

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### Do great spot like features favour appear in south hemisphere?

As we know, both Jupiter and Neptune have great spot like features in South hemisphere, and Saturn has dragon storm in south hemisphere, is it true that great spot like features appear in South ...
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### From which exoplanets is our sun the brightest star on the night sky?

The brightest star on the night sky is Sirius, here in the Earth. But are there any exoplanets, where the brightest star on the night sky is our sun?
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### Is solar wind a source of water?

Solar wind may contain some hydrogen and oxygen atoms which is the composition of water, some of them may move to the poles of earth, my question is, is solar wind also a source of water in earth?
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### What happens when an Ultra Massive Black Hole cannibalize another?

Say hypothetically an UMBH with 50 billion solar masses (supposedly upper limit) is beginning to merge with another (Super)MBH similar to Sagittarius A* that sits at the center of the Milky Way ...
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### Have we ever observed a body, such as a large asteroid, “hitting” the Sun?

Some other SE questions about launching ICBM's into the sun got me wondering whether we have ever observed an object on a path that intersected with the Sun? How close did it get?
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### When I read that a system is located x light years away, why is there no direction?

Well, I just read an article about a galaxy with two black holes, and it stated that the galaxy is 1 billion light-years away. Why is there no direction given? If the Big Bang happened, and things are ...
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In the Big Bang model of the Universe, every observable thing is thought to have expanded very abruptly from a point of infinite density and zero volume. However, the problem with this assertion is ...
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### How to calculate the temperature of a star

I need a way to calculate the effective temperature (surface temperature) of a star for a stellar model. I need something in the form Te=.... I have: Radius in m mass in kg the composition of ...
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### Should this photo of the sun's surface actually be white?

If I'm told correctly (eg. What Color is the Sun?) that the sun is actually white, should the photo on that page actually be white too? Is it just doctored to meet peoples expectations?: Likewise ...
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### What part of the milky way do we see from earth?

When looking up at the night sky, we can sometimes observe a bright band of stars stretching across it. I know this is our galaxy but exactly what are we looking at? Could we look at the centre of ...
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### Why isn't everything yellow(ish)?

I understand that - although appearing yellow - the sun is white. And that this is because the other light colours are scattered by the atmosphere. For example: Google image search for "The Sun from ...
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### Could a “burping” supermassive black hole be responsible for a spiral galaxy's look?

I read an article which suggests black holes could influence the production of stars in the galaxy as the black hole can burst out powerful X-rays to "snowplow" the surrounding dust and gas. Although ...
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### What constellations touch the 9-degree wide Zodiac?

Say Barry, could you abuse the answer-your-own-question feature of this site, and answer the following question: As noted in How many constellations in the Zodiac? the ecliptic itself touches 13 ...
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### uses of coordinate systems

Wikipedia describes the five following celestial coordinate systems each with rectangular/spherical variants: horizontal equatorial ecliptic galactic supergalactic What are the practical preferred ...
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### Is there any real chance of getting hit with a meteorite if we build a base on the moon?

I've been reading an article today on how the European Space Agency (ESA) has an interest in building a space village on the moon which will be 3D printed and assembled by robots. Eventually people ...
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### What is the temperature inside a Black Hole?

Is it insanely hot? Cause of so much gravity? Is it close to absolute zero? Cause the matter is so closely packed, there is hardly any space for particles to move? Is it room temperature? Cause ...
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### Fusion of elements inside heavy stars

I am confused with nucleosynthesis inside supernovae. I have read that the heavier elements are made through fusion of lighter element's namely hydrogen and helium. Does the star "store" all the ...
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### Number of galaxies per redshift

Does exist something like a distribution of number of galaxies per redshift interval? I'm studying galaxy formation and evolution, and I'm curious to know how many todays' galaxies (with redshift ...
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### Accuracy of Laplace Method for determining orbital elements

Recently I had to implement Laplace method and apply it to 3 observations of Mars (10 days in between two observations). The results were pretty good, with discrepancies with real data well below 5% ...
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### Conversion from Equatorial Coordinate to Horizon Coordinates

I'm developing my own Planetarium software using C++ following the book Practical Astronomy with your Calculator or Spreadsheet 4th Edition. I don't know if I my formulas are correct or not, but when ...
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### Can angular information be known more precisely than the diffraction limit?

The diffraction limit deals with the ability to determine if two things are separate. I am interested in the ability to find the the centroid of a single object. Imagine a star with no near ...
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### What was James Bradley's calculation to calculate the speed of light?

Looking into the history of how the speed of light came to be determined, to what we know it to be today, James Bradley is often mentioned. He was credited with the discovery of the aberration of ...
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### Center of the universe

Big bang is not an explosion, but an expansion of space and time. Universe had almost infinite density... wait a moment. If it had ALMOST infinite density, it had a certain volume, and thus, space ...
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### How do we know that the Universe is still expanding now?

Yes, I know that most galaxies have a red shift and that means they are moving away from us. The problem is that the farthest galaxies are 13.8 billion light years away. That means that the info is ...
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### Alignments of planets

I am going to ask an odd question, It is: In most of the images of our solar system we see that the planets are arranged in a straight line. As the paths of the planets are elliptical, could it be ...
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### Why aren't new stars in Earth's relative proximity constantly discovered?

Okay, bear with me. In layman's terms: The estimates vary, but on a clear night, away from big cities, one can see up to 5000 stars in the sky. All those are in the Milky Way, but they're hardly ...
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### Which is the most accurate stars catalogue for J2000 epoch?

I'm developing a planetarium software. I have no idea about how to obtain stars right ascension and declination. Searching on Internet I have found that Wikipedia has AR and DEC for a lot of stars. ...
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### Is the duration of a sidereal year stable?

According to this essay by Phil Plait, the duration of Earth's sidereal year is 31,558,149 seconds. Is this figure stable? If I were to meaure Earth's orbit several million (or billions) of years in ...
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### Camera reaching the event horizon

This question came to my mind after reading this. I think it is safe to assume that the supposedly thrown camera would not reach the event horizon in one piece. So my question is : If I dropped a ...
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### Trying to understand the way Saturn's ring look in this famous Cassini image

You all probably know the famous The day the Earth Smiled image. For the life of me I can't understand what's going on with the rings there. Seems like the "bottom" half of the rings is the half that ...
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### Why doesn't Jupiter increase the chances of an asteroid to strike the Earth?

I often hear the hypothesis that Jupiter decreases the chances of an asteroid strike on the Earth, but my question is, why does it only decrease the chances ? While Jupiter can deflect some ...
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### What would the apparent size of the four stars in the Capella system be from the L1 point between the first pair?

Capella is a system with four stars in two binary pairs (source: Wikipedia). If an observer were located at the L1 LaGrange point between the larger pair, how many degrees of the sky would each of the ...
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### humans leave earth forever? [closed]

my question is regarding space travel and also will some countries have colonies on mars etc cause the clear reason NASA etc are trying to send manned mars mission is to get raw materials etc or ...
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### Can a tidally locked planet have their own habitable zone?

As we know, if a planet is near a star and is tidally locked, then at near side it is very hot and at far side it is very cold. But between 2 sides there should be a gradient of temperature change and ...
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### What is the gravitational force felt on Earth from the other planets in our solar system?

How much gravitational force is felt on earth from the other planets in the solar system? The sun exerts the strongest g-force, holding us in it's orbit, followed by the moon which affects the tides ...
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### Gyrochronology?

I recently became aware of the work of the Kepler Cluster Study. In January of this year it was announced that a long awaited method of finding ages of "cool" stars is now available. This is huge and ...
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### A camera and time dilation?

If I travelled near a black hole, my time would progress slower relative to someone on Earth. This is clear enough. However, what if we sent a probe with a camera to a black hole? When we watch the ...
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### Beginner telescope for my daughter [closed]

My husband and I are trying to figure out what type of telescope to get our young daughter. We would like to be able to see planets but nothing too extreme. Just something to get her started. She has ...
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### Why do we believe that the super massive black holes at the centers of two merging galaxies would themselves merge?

When listening to podcasts or watching youtube videos of astronomers discussing galaxy mergers, I often hear talk about how the super massive black holes at their centers will themselves merge during ...
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### Are there accurate equinox and solstice predictions for the distant past?

I am trying to find information on the equinox/solstice dates before 1600, more exactly referring up to 10,000 BCE so as to create a sort of calculator on an Excel spreadsheet. I have read about the ...
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### Are black holes expanding?

We know that it is a commonly heard claim that in every black hole there is a universe. It is also believed that the universe is expanding. If we use both of these, can we conclude that every black ...
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### How frequently does a comet drastically change its orbit in the Solar System (like 67P did in 1959)?

Comet 67P/Churyumov–Gerasimenko flew by Jupiter at only 0.05 AU distance in 1959. This encounter lowered its perihelion from 2.7 to 1.3 AU (almost becoming an Earth crossing comet). Since it happens ...
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### Dating very old objects/events

After reading this space timeline, I have wondered how they managed to make these assumptions about various events like when the first black holes formed. This is obviously far beyond the good ol' ...
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### How long time since a typical asteroid collided with another asteroid?

How pristine and ancient are asteroids really? I suppose they melt and reform when they collide with each other. How frequently do they collide with each other?
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### Delta-v from Mercury surface to Venus surface

What it says on the tin: using the most efficient launch opportunity afforded by orbital mechanics, what delta-v would you have to impart to a payload to send it from the surface of Mercury to crash ...
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### How could we detect planets orbiting black holes?

Detecting planets orbiting around stars can be made with several methods, transit photometry seems to be by far the most popular method nowadays. I wonder how we could detect planets orbiting black ...
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### What instruments/science goals have the highest priorities for a combined orbiter and lander to Europa?

A NASA mission to Europa seems to have a friend in congress. What would be the most important instruments and science goals for such a mission? Seismometry, radar, surface chemistry, a drill/melter, ...
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### Theoretically, can a solar system evolve around lagrange points

My question is, during the evolution of a solar system is it possible to end up with a massive planet around a star with two small planets around their $L_4$ and $L_5$. Since we know it is not ...