All Questions
14,651
questions
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My question is about the warp of time and space near black holes
I have seen some recent articles indicating that there might not be a singularity at the center of black hole at all1. Have further heard commentary about black holes that spin incredibly fast.
I was ...
13
votes
2
answers
2k
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Multiply Earth's orbital speed with square root of 2
Earth's escape velocity is 11.18 km/s.
If I multiply Earth's orbital speed with the square root of 2,
29.7827 km/s x 1.41 = 42.11 km/s
How is this speed called?
I found this equation in an old German ...
4
votes
0
answers
85
views
If a rogue planet entered near Jupiter planet could it tear the planet apart?
Theoretically, there could be a rogue planet made of iron or even osmium in large quantities, which can make it have 25 Earth masses within the volume of 1 Earth Radii. So if this object came near ...
0
votes
1
answer
227
views
How did ancient models explain 6 months of day and night at the respective poles?
We know that the Arctic circle experiences 6 months of continuous day light during the sun’s apparent northward journey (to the solstice) and vice verse for the Antarctic region. This is attributed to ...
2
votes
0
answers
29
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Gaia coordinates in J2000 as done by the CDS
So I'm interested in knowing how the CDS calculates the J2000 equatorial coordinates from the Gaia DR3 equatorial coordinates (that are given in epoch 2016.0).
For example, for the star HD 308819 = ...
1
vote
0
answers
38
views
Is the "light-time" correction for the Moon's position in Meeus "Astronomical Algorithms" putting the Moon in inertial position or apparent position?
Originally posted on Space Exploration SE, I was encouraged to post it here.
I'm looking at the second edition of Meeus's "Astronomical Algorithms," chapter 47, "Position of the Moon.&...
1
vote
0
answers
19
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Geocentric position of lunar ascending node relative to the true equator and equinox of date, using skyfield
The following is what I'm doing currently. Am I missing something here? I'm unsure if I am converting in and out of Skyfield objects correctly, and there is any unaccounted for behavior i'm not seeing
...
4
votes
2
answers
188
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Are there areas within Jupiter's magnetosphere without powerful radiation?
I know Jupiter has powerful radiation belts, but I'm wondering if there are places within the magnetosphere that are relatively calm. I'm asking about Jupiter (a gas giant we know) because I'm curious ...
6
votes
1
answer
120
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Doesn't the moon actually make asteroid impacts on Earth more likely?
So the moon adds to the total mass of the Earth-Moon system so together there is more mass so then there should be more gravity due to the total system and the moon is small relative to how much ...
23
votes
6
answers
12k
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How does Titan maintain its atmosphere?
Titan, which is smaller than Mars, has an atmosphere but Mars is not able to maintain its atmosphere. Even Luna (the Moon) doesn't have an atmosphere. Why is Titan able to hold an atmosphere, despite ...
7
votes
2
answers
515
views
Why do red dwarf (M-type) stars give off such violent flares and CMEs, out of proportion to their size and temperature?
Dr. Becky (Smethurst) just posted a new YouTube video mentioning, as I have heard many times, that it might not be possible for life to form on planets around Red Dwarf (M) stars because they would ...
5
votes
2
answers
565
views
How to calculate the true distance of the sun and the earth using skyfield?
I'm trying to calculate the true distance between the sun and the Earth using skyfield.
To estimate the distance at a time instance I use the barycentric coordinates of the sun and earth using the ...
4
votes
1
answer
160
views
Energy density of the inflaton field
In the textbook introduction to cosmology by Barbara Ryden, the author say that the energy density of the inflaton field is:
$$\epsilon_{\phi} = \frac{\dot{\phi^2}}{2 \hbar c^3} + V(\phi)$$
However, ...
3
votes
1
answer
243
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'...
5
votes
1
answer
69
views
Query spectral type for absolute magnitude
I'm working on a project with stars where, given their spectral type (such as B0IV), I want to be able to know its approximate absolute magnitude.
I have searched online and found data sources like ...
9
votes
2
answers
372
views
Can Jupiter's nightside be classified as spectral type Y?
As far as I am aware, the latest spectral types that have been assigned are around Y2, for objects like WISE 0855-0714 that have temperatures around 250 K or so. I've also seen several directly-imaged ...
10
votes
1
answer
190
views
Color index B-V of the dimming Betelgeuse
Using AAVSO light curve generator I have plotted V and B magnitudes of Betelgeuse in the past 150 days to see trend of B-V color index. If dust would be the cause of the recent drop in the star ...
8
votes
1
answer
133
views
Do all C-O white dwarfs have more-or-less the same proportions of carbon and oxygen?
Type 1a supernovae are known for having very consistent energy yields, and they are caused when a carbon-oxygen white dwarf reaches the Chandrasekhar limit of about 1.4 solar masses. Since type 1a ...
7
votes
1
answer
141
views
Where will all atoms on the Earth end up when the Sun engulfs the earth?
I am curious about what will happen to all atoms on the Earth including all of our atoms after the Sun engulfs the Earth?
Will they become the part of the Sun's white dwarf?
Or most of them will be ...
8
votes
1
answer
166
views
Can two Stars form an Einstein Ring?
We know that when two galaxies are perfectly aligned they form an Einstein Ring by gravitational lensing but can two stars form it? We know gravitational bending by stars, but can two perfectly ...
0
votes
0
answers
77
views
Do all the planets in the universe rotate? [duplicate]
Do all the planets in the universe rotate by their own means. Do they rotate like the Earth? Are there any planets which don't rotate?
9
votes
2
answers
233
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How much mass does the Sun gain from the Poynting-Robertson effect?
I understand that the Poynting–Robertson effect describes solar radiation-induced drag on certain sized dust particles, causes them to lose orbital angular momentum and eventually fall into the Sun.
...
-1
votes
0
answers
140
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Birthday question
For X, this month in 2024, he has his 46th birthday on Earth, and, in the same day, it is his 191st birthday on Mercury. How often this happens?
Reedit: what is the relation between the orbital ...
0
votes
0
answers
28
views
Electron Temperature of a Gas Cloud
Would a gas cloud made of HII and OIII have a higher electron temperature than a cloud just consisting of HII? I understand that electron temperature is the temperature of the electrons in a plasma, ...
2
votes
1
answer
88
views
Details of the Moon's night photographed in a total solar eclipse
I didn't know that in photographs of total solar eclipses you could see details of the Moon's night.
To my surprise, look at this beautiful photo of the solar eclipse of 2024/04/23 taken by amateur ...
22
votes
3
answers
8k
views
Why wasn't the planet Uranus recognized by ancient cultures?
Mercury, Venus, Mars, Jupiter, and Saturn have been identified by ancient astronomers as they are visible with naked eye at night. The planet Uranus, despite being visible during very clear nights, ...
4
votes
1
answer
178
views
Voyager spacecraft distance from Earth
According with NASA JPL the earth catches up with the spacecraft because Earth is moving a lot faster than the spacecraft. Can one calculate the times when the spacecraft gets closest to Earth
4
votes
1
answer
87
views
Finding ones way around the sky
Thinking about this recent question Identify T-shaped constellation the first thing I have to say is that I applaud the poster for actually looking up and noticing the stars: something that becomes ...
1
vote
0
answers
88
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Kepler's description of lunar mountains before telescope
This question Why is the lunar relief not visible in photographs of solar eclipses?
Reminds me of something that I remember that Johannes Kepler wrote. When telescopes discovered mountains and ...
6
votes
2
answers
3k
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Why is the lunar relief not visible in photographs of solar eclipses?
I looked at a lot of high-quality images of solar eclipses and noticed the following thing:
In all the photographs I've seen, the lunar disk has a completely clear outline, in which it is impossible ...
1
vote
1
answer
77
views
Why do we call radio images "maps"? Is it because it is not optical, so therefore not an "image", strictly speaking?
Or is it just historical convention? I know that within research circles, it is common to also use the term "radio image". I am mainly wondering whether the term originally comes from ...
1
vote
2
answers
112
views
Book for young enthusiast
I'm looking for an astronomy book that's picture first, and covers a variety of topics but leads into the relevant math. Enough of a start for a kid that really studies could do a few easy examples ...
9
votes
2
answers
4k
views
Why do most planets remain within a few degrees from the ecliptic?
Why do planets, just like our moon, have their sidereal paths almost the same (with only slight deviation) as that of the ecliptic? Is it mere coincidence? Or is there a better solution?
This question ...
3
votes
3
answers
1k
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What is the nature of "rock vapor" in this description of the formation of the Moon?
The NPR News item MacArthur Fellow And Planetary Scientist Sarah Stewart Discusses How The Moon Was Formed and audio podcast begins:
Ari Shapiro, Host: Sarah Stewart likes to think about what happens ...
0
votes
0
answers
64
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Do solar eclipse paper glasses need to list both the ISO and CE stamp to be compliant or is the ISO sufficient?
I purchased them at the checkout at Walmart. They are Manufactured by American Paper Optics, LLC. Visionscientific.com ISO 12312-2.
However I don't see the CE on the glasses. Are they still OK? The ...
2
votes
1
answer
66
views
Expanding voids ending being collapsed?
According to some papers I've found 1, 2 expanding voids can be foun inside clouds of denser materials that can cause them to eventually collapse. I have two questions about this:
Overdensities ...
25
votes
2
answers
5k
views
What exactly is the "paradox" in Olber's Paradox?
To the extent of my understanding, Olber’s paradox states that if the universe was static and homogeneous, we should see a star at every point in the night sky and therefore the night sky should be ...
0
votes
1
answer
197
views
Rest-frame magnitudes and fluxes
I have a question concerning rest-frame vs observed frame. In the observer frame, I can define an apparent magnitude and an absolute magnitude (as the apparent magnitude if the object were at d=10pc). ...
1
vote
0
answers
63
views
Is this description of ecliptic times correct?
I did a brief write-up as a pet research project to explore astro-geological calculation and visualisation for
Muslim prayer times. It's not meant to be authoritative (either scientifically
or ...
3
votes
1
answer
116
views
How do go about seeing or photographing the ISS in front of the moon or sun?
I have the following telescope and kind of know how to set it up to look at the moon or sun (with filter of course). Other than that I am pretty much a total astronomy noob.
Besser®
Reflector ...
1
vote
1
answer
72
views
Determing timestamp of a photo of the stars using a plate solver
This question from 2016 seems to suggest that you need a powerful telescope to get a photo of the stars in such a way that you can use their proper motion to get a timestamp. If this is possible, how ...
2
votes
1
answer
242
views
How many tsunamis have been caused by meteorites falling?
I don't know if this is a better fit for Earth Science (because of the tsunami part) or for Astronomy (because of the meteorite part).
The Wikipedia page on tsunamis says that tsunamis can be caused ...
3
votes
1
answer
179
views
How does the geometry for constructing a declining vertical sundial work?
I understand how to construct South-facing vertical an horizontal sundials and the geometry behind their construction by projecting an equatorial sundial into a plane, but I can't quite get how to do ...
1
vote
1
answer
141
views
Could a red dwarf be "deionized"?
Even the smallest red dwarf stars have amazing flares. But the photosphere temperature can be as low as 2700K, which (I think) is too cool to ionize hydrogen. Even the sun at 5800K is cool enough that ...
0
votes
0
answers
16
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Converting equatorial coordinates of a comet's pole into cometocentric orbital coordinates I and Phi
The comet's spin axis orientation is usually reported in equatorial coordinates RA, Dec; however sometimes these are shown in form of the Eulerian angles equatorial obliquity (I), i.e. the angle ...
1
vote
1
answer
69
views
How far away are the two components of the Rigel system?
How far away is Rigel A and B and what is the angular diameter of Rigel B from A?
0
votes
3
answers
1k
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Right Ascension to Zodiac House
At the moment (01-04-2020 09:36) the Moon is situated in Gemini:
"The Moon is currently in the constellation of Gemini. The current Right Ascension is 06h 37m 56s and the Declination is +23° 42' 09”."...
5
votes
1
answer
1k
views
Sun moves relative to the stellar background?
I just got reading this book- "Astronomy - Principles and Practice 4th ed. - A. Roy, D. Clarke" and I got stuck at the following bold lines (I am providing the full text for context to my ...
5
votes
1
answer
788
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Is there any way to detect the three-dimensional distribution of baryonic gas in our Universe?
As the title suggests, can the current observational techniques detect the 3D large-scale distribution of the baryonic gas, rather than just the gas within groups or clusters?
0
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0
answers
63
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Why are paths of solar eclipses symmetrical around a January 2015 axis?
My cousin, James Andrews, observed that the paths of eclipses before and after Jan 2015 form a symmetry. Here is a visual description
I know there's a logical explanation, but it's been ascribed a ...