# All Questions

6,952 questions
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### What I can see with a 80/900 refractor telescope?

Recently I bought a telescope after a very good conversation with an astronomer friend of mine. The main goal is to see planets. However, Mars is so difficult and is far to find it in opposition. I ...
8 views

### Which is the farthest distance a particular distant known- identified object from the asteroid belt can get from the sun?

According to Space facts The Asteroid Belt is located in an area of space between the orbits of Mars and Jupiter. That places it between 2.2 and 3.2 astronomical units (AU) from the Sun But ...
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### What is so special about the Ultima Thule passed by New Horizon spacecraft?

I read that the New Horizon spacecraft passed by the Ultima Thule. I also got to know that it is a flat, snowman-shaped rock. What is so special about it?
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### How to calculate the argument of perihelion for exoplanets with incomplete orbital elements?

I'm trying to simulate the Kepler-444 exoplanetary system using data from this website. The problem is that there is no argument of periapsis parameter for the Kepler-444 system, so while I think I'm ...
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### Are galaxies moving in each direction with same speed?

All galaxies are moving away from each other (us) because of the expansion of the universe. Are they moving with same speed in each direction?
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### White Dwarf/Degenerate Gas Behaviour

just want to try to clarify a few things about the nature of White Dwarfs and degenerate gases. So if a white dwarf is help up by an electron degenerate gas, the electrons are unable to lose energy ...
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### Star rotational axes and Solar system orientations

How does the orientation of stars axes of rotation and any planetary systems relate to the plane of the galaxy? Is there any relationship that has been detected, are they grouped from their parental ...
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### Asteroid identification in fits image

I have a fits image, and I need to identify an asteroid. What characteristics do I look out for?
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### How come the Sun does not make the Moon crash on the Earth?

As the Moon loops around the Earth, on one side of the Earth it moves toward the Sun (let's call it downward side) and on the other side it moves away from the Sun (let's call it the upward side). ...
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### Historical Distance of Planets to Earth

I'm curious if there is a readily accessible tool available, or simply a reliable way to find out what the distance of the planets in the solar system were on a given date. For example, if I am ...
47 views

### What's the proportion of Mars' surface compared to Earth's surface uncovered of water?

How does Mars surface compare to Earth's surface? Mars is quite smaller than Earth, but most Earth's surface is covered with water. I thought making the math could be relatively easy but Earth isnt a ...
33 views

### Mass of the universe

How do we calculate the mass of the universe taking into consideration dark matter? Mass of visible matter can be computed by stellar method, but how do we calculate mass of dark matter which we don'...
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### Motivation for using $\sigma_{8}$?

Press-Schechter formalism allows one to universally quantify the number of massive dark matter halos in a given volume -- The Halo Mass Function. The density contrast is given by the rms mass variance ...
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### Change in declination due to precession

If the presenet declination(0°) and R.A(3 h) are known , when will the declination have the same value again?
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### Is there any known moon of a moon? [duplicate]

As far as I understand, a moon is an object in permanent orbit around a planet, dwarf-planet, asteroid, etc. If there was another object permanently orbiting this moon, would that be a moon-moon? Is ...
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### How long a photon stay suspended in orbit around a black hole?

Can a black hole free from an accretion disk collect photons in the photon sphere in a prolonged stable orbit? Could enough photons be in orbit to shade the actual black hole with light? Would a ...
43 views

### Found green rock 20cm below surface, is this an meteor piece? [on hold]

I am wondering if this rock on picture below is meteor fragment? If so what composition you think it is? It is magnetic i tried with magnet and it sticks to it very strong, it does have a lot of mass.
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### Finding the diameter of a molecular cloud using period of intensity variation of hydroxyl maser

So I have this problem (which I translated to English as accurately as could): When studying a compact molecular cloud with radiotelescope, at a wavelength of 18 cm, hydroxyl (OH) maser(ic) ...
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### How to calculate the time of Ekadashi days?

Is there an official reference algorithm for calculating the Ekadashi days? I found the textual description of Ekadashi calculation on wikipedia but can't really make sense of it in order to write ...
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### How do we know that the mass ratio of hydrogen and helium in the sun is approximately 3:1?

From what I learnt, we can find what elements are in the sun by analysing spectrums since each elements has same emission spectrum, and when you look at the sun's spectrum, you can see absorption ...
32 views

### Astronomy/Astrophysics Project With C++/C/Python [on hold]

I am a Computer Science Engineering student, in the 1st year of college. I'm insanely interested in making a project regarding astronomy/astrophysics but I don't know where to begin from. I know C, C++...
91 views

### Why do sun spots appear near the equator of the Sun?

I noticed on many examples sun spots are near the equator of the Sun. Why are there no sun spots closer to the poles of the Sun?
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### Why the Circumstellar Habitable Zone is defined as it is, if life could be possible outside of it?

According to Circumstellar habitable zone In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a ...
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### How was Cruithne's orbital time calculated?

How was it determined that Cruithne takes 770 years to complete its cycle with Earth? Janus and Epimetheus were disovered long enough ago, and have short enough cycle times, that we've had time to ...
47 views

### What causes random irregularities in the earth's rotation accounted for by dynamical time

I read in a book that the earth's rotation sometimes shows unpredictable irregularities(not caused by precession, nutation, tidal forces) which are accounted for using dynamical time. What would be ...
68 views

### How does making a refracting telescope very long reduce the chromatic aberration of an uncorrected lens?

Below are two cropped views of "Johannes Hevelius's 8 inch telescope with an open work wood and wire "tube" that had a focal length of 150 feet to limit chromatic aberration." from Harvard University, ...
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### Can rogue/nomad planets and other starless planetary bodies orbit each other in a stable system?

Nomad planets (also called planemos or rogues planets) which drift in space without a star or substellar object to orbit. The majority of such planets we have discovered are gas planets with thick ...
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### How can you verify the science presented on TV shows like “How the Universe Works” is current or valid? [closed]

What resources are there available where I could verify current scientific thinking on the origin of the universe theories?
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### What does half-lit means?

Aristarchus estimated the relative distance of the Sun and Moon by observing the angle between the Sun and the Moon (α in the diagram) when the Moon is exactly half lit. Angle β must be 90° for ...
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### What causes the duration of moon phases (the time the moon is visible above the horizon) to vary for an observer in the northern hemisphere?

Why does each phase of the moon stay up a different number of hours per phase, so that, for example, January’s full moon was up twice as long as the new moon? Plus every month this bulge shifts and at ...
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### Stars located outside of a galaxy

How common or rare is it to find stars outside of a galaxy? Can such a star still have planets that contain life? Recently, I think that I heard of a star with a planet that entered our Galaxy. Did ...
42 views

### nonagesimal in Kepler's parallax computation

I'm starting to learn Kepler's Astronomia Nova using William Donahue's translation . In the translator's introduction, it is demonstrated how Kepler did his parallax computation. I failed to ...
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### Do known exoplanets confirm or refute the Titius-Bode law?

We've had the Titius-Bode law around since the early 1700s or so, suggesting a mathematical sequence to planetary orbits. Since then we've managed to find some planets outside of our solar system. ...
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### Could FRB be the result of matter-antimatter annihilation?

I was listening to a scientific podcast about CPT-symmetry and mirror-universes, and when speaking about matter-antimatter annihilation, they stated that several emissions would occur at this time, ...
50 views

### Rendering asteroid orientation as seen from Earth

I am writing a program to render an asteroid as seen from various parts of the solar system. My goal is to roughly reproduce the image of Cacus according to information on its DAMIT detail page. ...
27 views

### Tides with 3 Largish Moons [closed]

As part of my worldbuilding for a book, I’d like to have a planet with extreme variance in its tides. I want lowest tide reveal about 30 miles of floodplain, and occasional massive tidal waves. I ...
17 views

### Necessary steps to calculate photon's path by using null geodesic equation

Can anyone please give me an explanation on how to calculate photon's path by using the null geodesic equation? N.B. I know all of the non-zero values of Christoffel symbols.
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### Scientifically important discoveries with the help of amateurs

I am looking for examples where amateur astronomers in these days contributed sigificantly to important scientifically discoveries. I am aware of one example: Victor Buso from Argentina was lucky ...
138 views

### How close to circular is the Earth's equator

Earth's orbit is about 99% circular. How circular is Earth around the equator? I know it bulges around the equator and is a spheroid. I also know it is not smooth and has oceans and mountains and all ...
28 views

### Field rotation / Parallactic angle question

edit: I am assisting a heliostat practical where students take spectra of a solar projection and calculate the rotational velocity of the Sun and the angle under which it is rotating. One of the ...
69 views

### Can the Dark Energy be Pauli pressure?

Some neutrinos are fermions. There are quite of few of them out there. Could their degeneracy pressure give rise to an expansion force to explain Dark Energy?
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### Are the stars seen at the equator different throughout the year?

If you live on the equator and look up at the night's sky at, say, midnight, would you see a completely different sky on the 1st of January than you would on the 1st of July? I assume you would as ...
945 views

### Beta Andromedae (Mirach) and distances mentioned in original Cosmos series from 1980

In one of the episodes from Carl Sagan's show Cosmos he explains that Beta Andromedae is the second brightest star in the constellation Andromeda, and is 75 light years away. The link to the video is ...
28 views

### Why would the Chang'e-4 lander find lunar far side temp. “colder than scientists expected”, when the LRO has already been taking thermal readings?

In January, the Chinese probe lander Chang'e-4 was was announced to have found temperatures dipping lower on the far side than expected ("Chinese rover finds lunar nights 'colder than expected'" by R. ...
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### Daylight Time Expansion

I live in northern hemisphere around 44th latitude. Starting from Winter Solstice, December 21, 2018 the duration of daylight is naturally increasing. What I observe, however, is that the duration ...
2k views

### Which Saturn satellite passes closest to Saturn's rings and at what distance?

I was using Stellarium to watch Saturn from its moon Pan and I saw the rings were very close to this moon. Now Saturn's rings extend for a large distance so several moons see them from close. I was ...
64 views

### How close would the orbit of Mars have to be to that of the Earth to induce a collision?

When the Earth passes by Mars they exert a slight gravitational pull on each other, but the force is so small that their orbits are not significantly disturbed. However, if we imagined that the ...
40 views

### Does the KBO 2014-MU69 have two numbers and entries in asteroid databases? How did it get promoted to Major Body designation?

In this answer I show that the (now pretty famous) Kuiper Belt Object 2014-MU69 has two entries in JPL's ephemeris generating Horizons site; Major Body ...