All Questions

0
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0answers
14 views

Gravity on a Planet

Would it be possible to live on an Exoplanet Planet whose gravity was twice that of earth ? We would weigh double what we weigh here on Earth and as I can imagine that would cause all sorts of ...
3
votes
1answer
99 views

Line of lights moving in a straight line , with a few following

My husband and I have just seen a line of about 15 lights moving in a straight line, quite high above clouds level with a gap then 5 lights, gap, another few, gap 1, gap a few. They were moving at ...
0
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0answers
10 views

Could images of (very) nearby targets be recovered from the EHT data

Reading this question I was struck by the fact that the "pointing" of an interferometer is effectively done in the correlator, at least within the common field of view of all the telescopes, which is ...
2
votes
1answer
29 views

How are pulsars detected from Earth?

This paper on Arxiv indicates that the signal period of known pulsars is 1 ms-15 s (0.07-1,000 Hz since F=1/T). I have an EE background and it's a long story how I ended up here, but suffice it to say ...
2
votes
1answer
36 views

Can a black hole “supernova”?

In layman terms: nothing ever escapes the pull of a black hole, not even light when a large star reaches the end of it's life you get a supernova sometimes the "remains" of these stars can turn turn ...
0
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2answers
36 views

Planets may repel each other in few cases

We know that when two huge black holes collide they produces gravitational waves in space time curvature. So if I am not wrong another object in space if goes in that direction during production of ...
1
vote
1answer
57 views

Is there a maximum Julian day?

I have read various discussions of the Julian day, including that on the Wikipedia, but none of these appear to define the maximum Julian day or proleptic Gregorian year in which that maximum day ...
1
vote
0answers
23 views

What maintains the high orbital eccentricity of many exo-planets near their sun?

Over the last decade we've discovered that many exoplanets not only have highly eccentric orbits, but also orbit very close to their sun. This is true of many classes of stars. I definitely have a ...
1
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0answers
30 views

What constraints are there on solid material in the ice giants?

Recently there has been experimental verification of superionic water ice (suggested to be called ice XVIII, not sure if this nomenclature is official yet), which turns out to be a solid (or at ...
0
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1answer
51 views

How Did Early Astronomers Measure Distances?

Prior to the era of radar and other forms of radio/RF/EM ranging, what approaches, methods, and techniques did early astronomers (e.g., Kepler, Cassini, Copernicus) use to measure the distance(s) from ...
2
votes
2answers
83 views

How would a Fast Fourier Transform Telescope work without a mirror, dish or lenses?

I recently came across a short article mentioning the idea for a telescope built without mirrors or lenses that instead uses an array of antennas and massive computing power to resolve an image. Such ...
2
votes
1answer
34 views

How much difference did the supply of “fresh” r-process elements make to the Solar System.?

In one of the answers to this question @MartinKochanski made the interesting point that the abundance of elements heavier than iron (r-process elements) in the solar system is probably due to a fairly ...
1
vote
1answer
80 views

Why a blue spot in some hubble images of NGC 4302?

In some images with coloring like in this one: There is a noticeably bluer region in the "bottom left" of the image, and the bottom part of the galaxy on the left. Being an inexperienced galaxy ...
0
votes
1answer
61 views

Are exoplanets which are above escape velocity of particular interest?

I was perusing the exoplanet database and looking for some of the more extreme orbits, when I happened upon HD 20782 B: http://exoplanets.org/detail/HD_20782_b Which is also listed (in two sentences)...
3
votes
1answer
90 views

Word for blue ring around the Earth

From certain positions in outer space the Earth will appear to have a blue ring around it when the viewer is in the shadow of the Earth and sunlight is passing through the atmosphere. Here is a ...
3
votes
2answers
60 views

What is the temperature about 10 or 15 feet below Mars' surface?

I was wondering this for a school paper I'm writing.
1
vote
0answers
27 views

Calculation of day lengths of moons or moons of moons

Is it possible to calculate the day lengths of moons or moons of moons? If so, does the day length depend on the longitude as well as the latitude? Also, if we calculate the day length, is it possible ...
2
votes
2answers
86 views

Can I learn astrophysics and astronomy with my basic math?

I want to learn astrophysics and astronomy, I'm very interested in it because there are many questions that popped up in my head, and really curious about things, but I'm afraid of a little bit on ...
27
votes
2answers
5k views

Are black holes spherical during merger?

I've been thinking about black holes, specifically during the final moments before two merge. I'm wondering if black holes, or I guess more specifically their event horizons, are always spherical. ...
1
vote
0answers
26 views

Calculating the range of visible Right Ascension and Declination from specific location + time

Given a specific date and time, and coordination of a location on earth, how can I calculate (myself, or using a python package) range of visible RA and Dec? For example (but I'm looking for a ...
5
votes
1answer
249 views

Why isn't Earth tidally locked to the sun?

Given that the moon has long been tidally locked with the Earth, why isn't Earth (or any of our other solar system's planets) tidally locked to the sun?
2
votes
1answer
58 views

Could an Earth-like magnetic field protect life at exoplanet Proxima Centauri b?

I took a look at Wikipedia's page for Proxima Centauri b, the exoplanet that orbits Proxima Centauri, where it is said it is expected to receive 2000 times of stellar wind pressures than on Earth. It ...
3
votes
0answers
37 views

How did Arecibo make radar images of ice on Mercury's poles?

How did Arecibo make radar images of ice on Mercury's poles? How were observations of the poles of Mercury geometrically possible from Earth? How was "high-resolution (1.5-km) imaging" possible from ...
2
votes
1answer
71 views

Question from a non-astronomer /non-mathematician regarding rotation speeds

I have been watching too much TV related to black holes. Most black holes are depicted with a disk of matter that spirals into the black hole. Does the mass and diameter of the disk have a bearing on ...
-5
votes
1answer
72 views

How were the orbital sizes determined in ancient India? [on hold]

Rg Veda of ancient India contains a code that gives all planetary orbital information visible in the night sky. It is worth knowing the origins of our solar system and its development through the ages....
2
votes
1answer
29 views

Extracting kinematics from stellar spectra. Why are template stellar spectra necessary?

I am trying to understand how to extract stellar velocity and velocity dispersion maps from spectral cubes, but with no success so far. To be more precise, I do not understand why people use stellar ...
1
vote
2answers
35 views

Is there a term for asteroseismology as applied to giant planets?

Giant planets such as Jupiter have oscillations which enable analyses using the techniques of asteroseismology, for example Gaulme et al. (2011) detected global modes on Jupiter via radial velocity ...
0
votes
0answers
44 views

really fast moving star-like light [duplicate]

I don't know ANYTHING about astronomy but I know what I saw and 2 of my siblings saw it too. I initially thought it was a shooting star, but a Google search quickly made it clear that it wasn't. it ...
2
votes
1answer
49 views

Why doesn't the solar azimuth vary uniformly

For the past few dates, I've been observing the rotation of the earth around the sun and noticed that the azimuth of the sun doesn't vary uniformly throughout the day. The azimuth varies faster during ...
1
vote
4answers
83 views

Is it plausible for a planet that is positioned in the habitable area of a solar system to have little extractable metals?

I am big fan of Asimov's Foundation and I am wondering about the plausibility of some of Foundation's imagined words. According to this article Terminus was a special world with little metals: It ...
-2
votes
2answers
163 views

Ludwig's star distance

Mizar and Alcor, each about 83 light-years away, have a fainter line-of-sight companion known as Ludwig's star, which was mistaken for a planet in 1722. The Wikipedia page only says it is "roughly ...
2
votes
1answer
38 views

Given a star's mass, age, and composition, how do I calculate the rest of its properties?

If I'm given a star's starting mass, starting composition (metallicity), and its current age, How do I calculate the star's luminosity, current mass, and radius? I want to know how to do this for any ...
2
votes
0answers
55 views

Why does the number of extrasolar planets vary in different sources?

There are at least three catalogues that are counting up-to-date discovered exoplanets. What criteria do they use to count the number of planets? Every catalogue has a different count value. So at ...
1
vote
1answer
77 views

Is Enceladus the moon with salty water?

May anyone tell me does it known if Enceladus has water and is that water salty?
0
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0answers
39 views

Question on dec 2013 answer to“How to measure the altitude and azimuth of a star?”

I am looking at your response to the above question. You stated: For Northern Hemisphere, a star that is crossing the North local meridian (that is, between the Zenith and the North Horizon) the ...
3
votes
1answer
58 views

Why are Bok globules so cold?

I have recently read a bit a out Bok globules. One thing, that is repeatedly emphasised is that they are among the coldest objects in space, with a temperature of ~3 K. Why is that so? Naively, I ...
1
vote
1answer
30 views

Relationship between Periapsis and apoapsis longitude

What is the relationship between Periapsis and Apoapsis longitude ? Are they 180° apart ? (ie) Periapsis + 180° = Apoapsis ? Related question: if apoapsis is not known, what orbital elements are ...
3
votes
1answer
53 views

How to check what telescopes were looking at a certain portion of sky at a particular time?

I have some data that I collected from observations at a specific RA, DEC and I am trying to figure out what telescope surveys were looking at that portion of the sky at that particular time? I am ...
3
votes
0answers
46 views

Are there any estimates for the combined mass of all near earth objects (NEOs)?

I tried looking around but couldn't find any sources attempting to answer this particular question. It's obviously impossible to know the exact answer, but all I'm looking for is an estimate. My ...
1
vote
0answers
19 views

A good definition of specific intensity?

I’m studying specific intensity for a course on astronomical instrumentation. I can’t quite get my head around the proper definition of the term. One definition I’ve found in various lecture notes / ...
6
votes
2answers
87 views

Why would tidal forces on planets become more intense when a star becomes a white dwarf?

I was puzzled by this press release by the Royal Astronomical Society: "Small, hardy planets most likely to survive death of their stars" - phys.org, May 14, 2019 Astrophysicists from the Warwick ...
2
votes
1answer
27 views

Astrophysics of Supernovae - Energy over Distance?

I need this for worldbuilding, but it is a physics question. I want to be able calculate the energy over distance from a hypernova of a variable star like Eta Carinae. Understanding what energy levels ...
0
votes
0answers
25 views

Expansion of space or constriction of length scales?

According to wikipedia, "Technically, neither space nor objects in space move. Instead it is the metric governing the size and geometry of spacetime itself that changes in scale. Although ...
4
votes
1answer
40 views

Obtaining TESS input catalog (TIC) IDs for Gaia `source_ids`?

The TESS input catalog (TIC) "uses the GAIA DR2 catalog as a base" according to the catalog's website. The Gaia DR2 database provides source_ids for each ...
1
vote
1answer
49 views

Time taken for sun to rotate [closed]

If sun rotates with the same angular velocity of earth, how much time does it take to complete one rotation.
0
votes
0answers
41 views

Theory of relativity [closed]

Theory of relativity states that a fabric of spacetime exists on which objects are present, creating depression according to their masses. But then how are we able to see various objects with ...
1
vote
1answer
38 views

tidaly locked celestial body in three planet system

If a Planet have 2 Moons (so suppose system of 3 bodies) and we say "One Moon is tidally locked to Planet" how can we say that it is tidally locked when Baricenter of 3 bodies has its trajectory?
0
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0answers
35 views

What is the center of rotation used to determine if two bodies are tidally locked? [on hold]

Is it the barycenter, or some other point or coordinate system origin which we use to determine if two bodies are tidally locked?
1
vote
1answer
40 views

How is stellar mass of a galaxy obtained?

I believe there is a difference between the mass calculated using the orbital speed and the stellar mass of the galaxy. So how is the stellar mass calculated? Thank you :)
0
votes
0answers
77 views

Integral for tidally locking of the Moon [closed]

May a one explain with integral tidally locking? We know that the Moon when we look at it from Earth makes "tilts" and that tilts describes function which can be integrated. What is the formula of ...

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