# All Questions

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### How are molecules detected in space?

Recently the sugar glycoaldehyde was detected in a star system 400 light years from Earth. How exactly are molecules detected in space? I am aware that spectroscopy is used to detect them, but I don't ...
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### Is there a ceiling for stable L4 or L5 masses?

L4 and L5, the Lagrange points 60 degrees leading and trailing an orbiting body, are famous for being stable. A well known example are the Trojan aseroids at the Sun Jupiter L4 and L5. Nodding to ...
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### How would Jupiter's brightness relative to our sun seem to a remote observer (observing from a remote star)

Given that Jupiter is 5 AU from our sun and a remote observer viewing our solar system from some other part of our galaxy looks at it. We assume that Jupiter's radius is $11 \times 6700$ km. What ...
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### Can the supernova remnant SN 1572 be observed by amateur astronomers?

The SN 1572 remnant, also called Tycho's supernova remnant, is beautiful in X-ray images. It seems to be rather dim in visible light. Are there any amateur photographs of this object? How long are the ...
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### Relocation to Mars

One billion years into the future and the Sun has swollen in size and it is now not possible to live on Earth due to the heat. Mankind has relocated to Mars where the temperature is more favorable now ...
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### Heat from other Stars

Does the Earth receive any heat at all from the millions of other Stars in our Galaxy ? Is it light that is bringing the heat and perhaps it cools down on the long journey in Space getting to the ...
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### How long was the hyper inflation phase?

How long was the hyper inflation phase? Haw can we know that it lasted for a period of time and not more or les time?
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### What astronomical observations would give conclusive proof of alien life?

There are several ways we are coming closer to answering the question "is there life elsewhere in the universe?". One is by first understanding very well the origin life on our own planet. Another is ...
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### L4&L5 positions?

I know that, in L4&L5, the distances to the two main bodies should be equal. Still, how can I calculate that distance with accuracy? How can I know that that distance is inside the equipotential ...
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### What are the Gamma rays and Cosmic rays effects on humans and equipments? [closed]

First of all not to consider me a conspiracy theorist, but isn't landing on the moon a questionable issue? I am really not an expert in astronomy but let's assume that a moon landing has happened. 1- ...
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### Circular orbits

First of all, I'm studying orbits for a hobby: world building. Unfortunately, my mathematical abilities approach a ridiculous low threshold, which means I am stuck with reading the simplest ...
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### Is it proper to refer to objects beyond Neptune as “Kuiper Belt Objects?”

It seems to me that nowadays the more proper term is "Trans-Neptunian Object". Is there any difference between Kuiper Belt Objects and Trans-Neptunian Objects? If not, is one term preferred over the ...
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### Determination of orbital elements for Trans-Neptunian Objects, how?

How are orbits calculated for Trans-Neptunian Objects? I understand there are six standard parameters for defining an orbit (link) but I am not sure how telescope observations translate into these ...
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### How are parachutes usable in other places than Earth?

Mars landings, Moon landings. . . Wherever I see a documentary or still pictures in Wikipedia, there are parachutes in the landing of rovers. Whenever I see them, I ask myself, "How they can it ...
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### Estimates for how many Trans-Neptunian Objects there are [duplicate]

The Minor Planet Center shows that we know of about 1350 Trans-Neptunian Objects (TNO's). I think it is safe to assume that we have not found all the TNO's there are to find, even the ones that we ...
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### Can an astronaut ever reach a Black Hole theoretically? [duplicate]

Ok, bear with me, while I try to explain the question I have. I read that time slows as we approach a black hole. So, suppose,theoretically, as astronaut is approaching a Black Hole. And he gets ...
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### If Kepler-444 planets existed for 11.2 billion years, why fear for life on Earth after six billion years?

According to recent news, Kepler-444, a 11.2 billion year old star, has a system of five planets. It has a mass of 3/4 of solar mass. So I believe both Kepler 444 and the Sun will share the fate of ...
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### How precisely is planetary tilt defined (the tilt direction, not just the angle)?

The earth's axis is titled 23.4 degrees with respect to the ecliptic. Since this tilt is responsible for the seasons, it's clear that the tilt is in the direction away from the sun on the shortest day ...
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### Why would all places appear to be at the center of the universe's expansion?

I just watched an iMax planetarium video that claimed that no matter where you are in the universe, it will appear that you are at the center of the universe and all things are expanding away from ...
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### Calculate the time when Arcturus passed through the meridian

If the observer observes Arcturus passed through the meridian about 23:00:00 of 28 April. Find the time that Arcturus passed the meridian in 29 April. And what day does the Arcturus will pass the ...
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### Burning Out Stars

In the book "A Really Short History Of Nearly Everything", I read that the larger the star is, the faster it burns itself. Whys that? Wouldn't there be more energy to burn if it's larger, and just be ...
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### Does one need to take into account finite gravity speed in N-body simulations?

Most small-scale N-body simulations (e.g., planetary systems, solar system, stellar clusters, ...) use classical Newtonian gravity. Most large-scale N-body simulations (e.g., galaxy clusters, ...) ...
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### Why are gas giants colored the way they are?

As I understand it, Jupiter, Saturn, Uranus, and Neptune are all made primarily from varying proportions of hydrogen and helium. Despite this, Jupiter is very red, Saturn is yellow, and Uranus and ...
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### Are a black hole's jets caused by the black hole's magnetic field?

Do the jets sometimes emitted by a black hole result from its magnetic field? It would seem Jupiter's magnetic field tends to be concentrated at the poles, and I would imagine this might extend to ...
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### Cancelling out earth rotation speed, Altazimuth mount

I have a Dobsonian telescope. It is using Altazimuth mount. Basic idea of using it is to target the object by moving telescope vertical axis perpendicular to the ground, and an elevation axis that ...
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### Galaxy rotation curve and dark matter

I am reading "The Essential Cosmic Perspective" by Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider, Mark Voit. In Chapter 14, it is stated that an evidence of the presence of dark matter in ...
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### Does the cosmic microwave background change over time?

Does the cosmic microwave background pattern change over time? I would assume it is getting "cooler" as in more redshifted as time passes, but I am more interested if the pattern on the background, ...
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### Entropy of black hole

A line from one of the answers on a different question got me thinking: The simplest way to see this is probably that a black hole has a much higher entropy than a star or even another type of ...
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### Does the cosmic microwave background recede at the speed of light?

Does the cosmic microwave background recede at the speed of light? Is it possible it recedes even faster because of the stretching of space?
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### Find the height of the shooting star from the Earth's ground

One night, you and your friend were talking to each other. Your friend far about 20 km. from you. You told your friend that you see the shooting star pass through the sky at altitude of 75 degrees. ...
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### Is C/2012 S1 (aka ISON) the fastest comet on record to-date?

This source may be nebulous (no pun intended!) for some. It writes to say Starting at around 95,000mph at the start of this month, Comet ISON will eventually reach an astonishing 845,000mph on ...
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### What are the exact physical parameters used to calculate Mercury precession with Einstein theory?

NASA measured 43,13 arc seconds per century. General relativity predicts 42,98 arc seconds per century. I try to find out what the parameters' values such as $G$, $M_{sun}$, $\omega_{min}$ at ...
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### When we see half moon, why is it always the lower half?

Even if we see a crescent moon, always the lower circumference is visible. Why we never see this? PS: this image is vertically inverted.
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### Is it possible to disprove geocentrism without telescopes?

The development of telescopes enabled the discovery of moons orbiting around Jupiter, and the existence of a full set of phases of Venus, as opposed to a limited set which would be predicted by ...
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### Light Cone Explanation

Not sure if this question belongs here, or on Physics. Would someone please describe the "anatomy" of a light cone and provide an intuitive example? I have read the Wikipedia article ...
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### Mass, Radius, Colour, Size, Type of a Star from the Hipparcos Catalog

Using data from the Hipparcos Catalog download file, is there a way to determine the Visual or Apparent Magnitude from the data within? Can I obtain the Mass, Radius, colour, temperature, type ...
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### Could there be another planet between Mercury and the Sun?

Could there be another planet between Mercury and the Sun? Kepler found a lot of planets orbiting its star even 20 times closer than Mercury. If there were such planets in our system - would it be ...
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### What qualifies as a local star?

My professor used the term 'local star'. What range of distance is generally considered 'local' for a star? And what would be considered distant?
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### In geocentric models, did the earth rotate?

Under geocentric models, did the earth rotate around its axis? I assume that if the earth rotated around its axis, then the sun would not have to orbit around the earth at a very fast rate, whereas ...
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### How gently could a comet/asteroid/meteorite “hit” Earth?

Could an object from outer space with the right velocity and orbit come into contact with the surface of our planet in a "slowish" manner?
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### How are black holes found?

Black holes have so much gravity that even light can't escape from them. If we can't see them, and the suck up all electromagnetic radiation, then how can we find them?
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### Why do not we use optical telescopes to study cosmic rays directly?

HESS, CTA, and VERITAS are used to study cosmic rays. What they receive are optical (maybe very blue) photons. So my question is: Why don't we use optical telescopes to study cosmic rays directly?
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### earth is spherical , does it mean the ground on earth is like a ball? [closed]

I know earth is spherical in shape. Does this means earths atmosphere is spherical in shape or the ground/(land+water combined) is in spherical shape. I have some doubts if the second is true. ...
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### Why do we have so few neutrinos to study?

According to Wikipedia most neutrinos passing through the Earth emanate from the Sun. About 65 billion (6.5^10) solar neutrinos per second pass through every square centimeter perpendicular to the ...
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### How to complete the Hipparcos Catalog?

I've downloaded hipparcos catalog from the Strasbourg Universe but whilst there is a lot of information, I can't find the names of the stars that the HipID relates to. There is the wikipedia page ...
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### Do objects look larger the further away they are, beyond z=1?

I stumbled upon this text which illustrates and says: We find that as the object is moved to higher redshifts its angular size first decreases (as naively expected) but soon begins to increase ...
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### What does it mean to say 'space exists?'

From another question I posted, I learned that not only was matter created from the Big Bang, but more importantly, space itself. What does it mean for space to be created? Does it exist in the same ...
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### Theoretical limits for natural satellites having natural satellites

Is there an inherent instability or limit that prevents natural satellites like the moons of Jupiter from having their own natural satellites? I looked at other questions such as do moons have moons ...