# All Questions

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### Why don't all space junks burn up? [migrated]

Man-made satellites have to use boosters to accelerate to maintain orbit around the Earth, space debris and old satellites with depleted booster should be pulled by either Earth's gravity or slowed by ...
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### What are the analysis steps in taking raw data from Kepler to a planetary system determination

I wish to get a concise list of the analysis steps required to take raw light data from a Kepler data set of a star through the steps needed to get to an analytical determination of the existence of a ...
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### Chances of man-made satellite colliding with space debris [migrated]

Firstly, has a man-made satellite, or indeed any spacecraft, ever collided with space debris and been destroyed? What are the chances of this happening? (I imagine very slim, but how slim?) And do we ...
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### How much time runs from derailing to the fall of the satellite and its true anomaly at the fall? [on hold]

Planet with a radius R and mass that goes around on the elliptical orbit with a semi-minor axis a and eccentricity e. Its speed of the fall equls v0. What is full of energy at the satellite at ...
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### How much time comet is within the Earth's orbit?

Comet on the parabola orbit flies by Sun. I would like to know what is comet's full energy? What is its distance from Sun at perihelion?
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### Retrograde momevent and Distance of Saturn from the Sun and its Sidereal Period [on hold]

The numbers marked a reference position of the planet at the beginning of the relevant month. Elongation Saturn at stationary point (jam) is 109 degrees. I wonder how much elapses between two ...
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### To what extent we should just before the collision with the rock change the speed of the probe that it would be relative to the rock equal to 0? [on hold]

We are having a satellite lauched from the Earth to reach the roch on a hyperbolic orbit around the Sun. The both have the opposite velocity vectors. I wonder how long does it take to reach the rock ...
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### How to calculate full (mechanical) energy on the hyperbolic orbit?

For example, for a comet that travels on the hyperbolic orbit around the sun.
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### Asteroids in langrangian Points 4 & 5

There are Asteroids "trapped" in Jupiters Langrange points 4 and 5 called trojans and greeks. Are there any asteroids in the earths L4 and L5? Have we seen asteroids in Lagrange points of the earth ...
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### Michigan's Pole Star

Unfortunately, I'm not any good at figuring these things out myself so hope for help here. If the (true) north pole were over the Keweenaw Peninsula of Northern Michigan, what would the North Star be; ...
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### How to deal with shifting CCD bias (zero exposure) levels?

The median values of the bias frames coming from our teaching telescope shift up or down with each capture. For example: ...
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### What is the reason for the dispute over the variation of core mass with heavy metal abundance?

In Metal-Poor Stars IV: The Evolution of Red Giants, Rood writes The differences in the results of these papers are large enough to introduce appreciable uncertainties into the study of the ...
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### coordinates in ICRF

The International Celestial Reference Frame (ICRF) is defined based on distant quasars and the origin is the barycentre of the Solar system. So, how can we measure the coordinates (\alpha, \delta) of ...
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### why are solar telescopes built on lakes? the site differnece between a solar and an optical telescope

According to the wikipedia page big bear, water can cool the observatory. Big bear is in the southern California. It is better to build it on a cold high mountain with stable and clear atmosphere? ...
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### How is the age of a star on the Henyey track calculated?

I was reading Stellar Evolution in Early Phases of Gravitational Contraction, by Chushiro Henyey, where he writes, If $L \propto R^{-\alpha}$ along the path, the age of a star from the time when ...
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### How would time travel work with a man made wormhole, with one side of it sent on a rocket at light speed and then returned to Earth? [on hold]

I just watched an episode of the History channel series The Universe: Collection, this particular episode was focused on time travel. One of the theories mentioned is that a man made wormhole could be ...
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### Sunsets: Mars/Earth

I understand why our sky is blue and turns red when the sun sets or rises. I know why the sky on mars is red, but why does it turn blue during sunsets and rises? Shouldn't this actually not work due ...
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### For how many bodies can there be a stable orbit with no very heavy central body?

The question is a bit vague, but let me explain: Take for example 2 bodies of the same mass. They can orbit around their centre of mass/gravity. Is something like this possible with multiple ...
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### Types of Exoplanets

We discover vastly more exoplanets, that are gas giants that orbit their parent star very closely, than small terrestrial planets that are more distant to their sun. Could this be due to the methods ...
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### Probability of finding life-supporting exoplanets

We've found over a thousand exoplanets by now, but how many of them could support life? What percentage of newly found planets are potentially life-harbouring? Or haven't we found any exoplanets that ...
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### Circumstances that would make it impossible to predict a large metorite strike? [on hold]

Under what circumstances would it be impossible to observe a large meteorite on collision course with Earth, and thus to do anything to prevent or mitigate the consequences of the impact?
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### Why aren't secondary mirrors offset to get rid of diffraction spikes due to the support vanes?

Some kind of ellipsoidal shape mirror could reflect to a secondary mirror which is not in the way of the infalling light. Two advantages are immediately obvious. The primary mirror would not be partly ...
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### Can the Milky Way be seen with the naked eye? Does this apply to any galaxy? If yes, then how and when?

I have seen different pictures in a different community to showcasing the Milky Way. I can never tell whether it's edited or it's the real picture. Actually, I can never see any galaxy as such by with ...
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### Milky Way stellar number density : is the stated equation in this paper incorrect?

The paper is : http://www.astro.washington.edu/users/ivezic/Publications/tomographyI.pdf The equation is equation #23 in the paper. It's a model for the density of stars in the Milky Way's disk. It ...
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### How can we tell the difference between matter and antimatter by observation in space?

I just was wondering and searching on the internet with little luck in the topic. On Antimatter Wiki they tell the observable universe is built up by matter. I read antimatter can be detected in ...
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### Finding the northernmost latitude in a great circle that passes through two points on the sphere [migrated]

I'm trying to prove that: a) If A and B are two places in the earth's surface with the same latitude Φ, and the difference between their longitudes is 2l then the highest latitude reached by the ...
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### Longest and shortest wavelength

What is the longest and what is the shortest wavelength of light? How fast would a light-emitting object have to recede in order to shift the frequency of light to increase the wavelength from the ...
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### Attraction to barycenter

If an object was a distance from a planet away that equaled the distance from the object to a moon of the said planet, would it be drawn into the direction of the barycenter as it is the common center ...
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### Globular cluster star density as a function of distance from the center

Context: I want to simulate globular clusters in a simple way, just to display the positions of stars. Assuming isotropy, what would be a reasonable model of the stellar number density as a function ...
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### How would the solar system look in a Geocentric model?

If I fix the Earth as the center of the solar system, what would this look like? Are there any good images? How complex is this system?
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### Is radiation from neutron stars delayed by time dilation?

I understand a neutron star to be the densest stuff that can exist without becoming a black hole, the densest thing which directly gives off radiation we can detect. At the event horizon of a black ...
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Ok so I was reading about the Fermi paradox, assuming life will form and thrive where possible as soon as possible and there is a very probable chance many other earths formed would they have started ...
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### Exoplanets and relativity [duplicate]

Ok, so I have read about how exoplanets are found using all sorts of genius methods. I also understand the further an obect in a telescope is the further into the past I am looking. So given that ...
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### What supernova has created the iron currently found in Earth core?

Iron is generated by stars in a certain part of their life cycle. Earth contains a lot of iron inside, however it is clear that this iron could have not been generated in a star in close proximity. If ...
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### What happens to galaxies when they die?

Stars explode when they die and blast heavy elements into space. Do galaxies do the same thing?
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### Standardized “constellation” regions?

The current system of constellations is historical and has kind of arbitrary boundaries. This has a number of obvious downsides: Difficult to define boundaries need complex tables to express Each ...
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### What is a typical value for core-to-star efficiency?

I was reading Unfolding the Laws of Star Formation: The Density Distribution of Molecular Clouds by Kainulainen et al., which discusses star formation rates and efficiencies. One variable used is ...
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### Occurence of Venusian transits

As transits of Venus come in pairs each seperated by 8 years, wouldn't that imply an accurate ratio between earths and Venus' revolution period? I've found the ratio to be about 0.681. I presume one ...
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### Where might a semi proficient amateur analyst participate in meaningful astronomical efforts

I am a retired engineer that has an ongoing interest in space efforts. In my youth I did work on the Apollo program but on propulsion and vehicle thermal control: not flight dynamics. I have ...
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### Evidence that galaxies are made of billions of stars?

What is the evidence that galaxies are made of billions of stars? Even faint galaxies? Can spectral analysis distinguish galaxies from individual stars?
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### If conjuncting planets are 1/3° apart (geocentric) at 15° elongation how low could the elongation at closest approach be?

Does anyone even have a rough idea? I don't know which pairs of planets can appear close for longer without changing elongation too slow like Mars does when behind the Sun.
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### “Up” and “down” in Space [on hold]

From my understanding, "up" and "down" in space is going towards (down) an object's gravitational pull or (up) which is going away from it. I get confused with this explanation, and I believe simply ...
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### Finding Latitude and Longitude of a person or of where a picture was taken

this is my first post on the Astronomy stack exchange site. Please let me know how this question is based on y'all's generally accepted criteria for a good question as well as possible improvements. ...
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### Has the sun become way brighter the last years?

Up to last year, I never got blinded by the sun in everyday situations (e.g. running towards it), at no time of the year I was. But since last christmas, it occured to me more often that I cannot ...
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### Difference in redshift between 2 interacting galaxies

I have a galaxy 'A', say at redshift 1. Let's suppose this galaxy has no peculiar velocity. What would be the redshift of another galaxy 'B', that has a radial velocity of 500 km/s, relative to A? ...
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### Which is more rare: Lunar eclipse or Solar eclipse?

Which is more rare: Lunar eclipse or Solar eclipse? Please explain why either one is more rare than the other. Thank you in advance for your inputs.
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### Stars in the sky

Are the stars we can see with the naked eye in the night sky only from our Milky Way galaxy or can we see stars from Andromeda? I am aware we can see other celestial objects like nebulas and the ...
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### Why can we see stars but not astronaut on the moon

A question came up today in astronomy class and it got me wondering all night. How is it that if stars are so far away, we can see them so clearly but we cannot see astronauts on the moon.