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Questions tagged [astronomy]

The science dealing with objects and phenomena located beyond Earth. In particular, this applies to observations and data. At its core, astronomy is the physically informed cataloging and classifying of the contents of the universe in order to better understand what is out there.

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Is there a reason why in the astronomic pictures of galaxies and nebulosas there is so little green color?

From a quantum physics standpoint, why do astronomical images of galaxies and nebulae exhibit so little green color in their spectral composition? When we look at the pictures of galaxies provided by ...
Alfredo Maranca's user avatar
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About redshift and distant objects observation

I did a few Time&Length dilation factor calculations. This is for a distant clock away from any field and a clock on Earth on the equator with the moon passing over clock coordinates, the factors ...
olivierlambert's user avatar
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Is there a database or catalog of all black hole candidates?

I am searching for a catalog, list, database, etc. That should show astronomical observations of known black hole candidates. I am primarily interested in knowing the mass of these candidates. I have ...
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2 answers
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Is the information or energy in a black hole converted to another form of energy during decay of Hawking radiation?

The Hawking temperature equation states that the temperature of a black hole is inversely proportional to it's mass, and and the black hole loses mass when it emits particles in the form of radiation, ...
Sumer's user avatar
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Geocentrism and annual tide variation

I have read that in the before common era, Seleucus of Seleucia have studied tides and probably used annual variation as an evidence of heliocentric. However, tides are known to be affected by ...
mohamed's user avatar
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What is emission line ratio?

As the header stated, what exactly is the 'emission line ratio'? Like, [O III]/Hβ or [Ne V]/[Ne II]. Recently I've been reading some research papers in astronomy and astrophysics pertaining to ...
ZenithalizeSquads's user avatar
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1 answer
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Assessing the quality of wavefront correction in adaptive optics systems: the case of single and multiple radiation sources

Generalized diagram of an adaptive optical system is as follows: Wavefront from the observation object passes through the atmosphere and is distorted. It is then reflected from the deformable mirror ...
ayr's user avatar
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Should luminosity distance be $0$ at $z=0$?

I am working on coding up the luminosity function for blazars but I have ran into a problem. In equations 1-3 of this paper https://arxiv.org/abs/1912.01622 they state that the flux can be broken down ...
John's user avatar
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Stars that have fairly high gravitational redshift and calculation of their surface temperature by Planck emition spectra?

How high can the ratio between gravitational redshift and planck emition spectra be depending on the mass of the star so by how much this gravitational redshift could elongate the Planck spectra of ...
Krešimir Bradvica's user avatar
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1 answer
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What is the function that demonstrates a planetary transit light curve given a planet's projected distance from its star?

Last night I was measuring the brightness of a Hot-Jupiter parent star to try and isolate the transit light curve (specifically Tres-2b). I have been wondering how to obtain the function that ...
Kareem Shamma's user avatar
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Using helioseismology what are the equations astrophysicists use to determine the age of the Sun? [closed]

Astrophysicists talk about solar models when determining parameters of the Sun. But these models must be built from equations. When explaining to the general public what these equations are would be ...
Walter 's user avatar
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Does the Kardashev Scale have any practical application?

As the question states: are there any practical applications of the Kardashev Scale?
Dancrumb's user avatar
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5 votes
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Is it possible to predict the appearance of auroras?

Yesterday I saw online a lot of people seeing auroras both in the North and in the South of the globe. Unfortunately, I wasn't one of these people, and this got me curious about how much we can ...
Níckolas Alves's user avatar
2 votes
1 answer
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Trajectory of supergiants on HR diagrams

I am a secondary school student currently studying cosmology. My A Level textbook supplies the following HR diagram with regards to what trajectories different stars follow: I found myself unable to ...
Chun Hei Chau's user avatar
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Magnetic tubes or magnetic field lines around a black hole?

A picture is worth thousand words: Magnetic field lines, unlike magnetic tubes, have a continuous distribution. Recent pictures of black hole magnetic structure show tubes. Is there a model that ...
Shaktyai's user avatar
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2 votes
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Which of the blocked radiation windows will (mostly) open if one where to observe from the surface of Mars, instead of the Earth?

Earth’s atmosphere is composed of about 78 percent nitrogen, 21 percent oxygen, 0.9 percent argon, and 0.1 percent other gases. Trace amounts of carbon dioxide, methane, water vapor, and neon are some ...
some_math_guy's user avatar
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Galaxy harassment; flyby encounter (tidal interaction)

This following image is from the paper https://adsabs.harvard.edu/pdf/1978AJ.....83..219R#page=4 It shows the path of a flyby encounter of NGC 3627 (M66) with the galaxy NGC 3628 (the Hamburger galaxy)...
Hey's user avatar
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How can I see Orion's Belt in winter and summer?

How can the 23 degree tilt of the Earth enable someone in Argentina to see the same constellation (Orion's Belt) in winter as someone in Britain in summer?
Danny Rosenberg's user avatar
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The astonomer's method of color differencing as applied to proving Einsteinian relativity during a total solar eclipse

I'm looking to see if the astonomers' method of color differencing was ever applied to the stars near the Sun during a total solar eclipse, for example, to demonstrate Einsteinian relativity visually ...
user1621287's user avatar
3 votes
1 answer
187 views

Speed at which the Moon moves past a point on Earth's surface?

I'm trying to calculate how fast a point on the surface of the Moon is moving past a point on the surface of the Earth (I assume a point on the equator of each for simplicity). I know the Earth is ...
tansvaal's user avatar
1 vote
0 answers
95 views

Why does the peak of quasar distribution move from near to far with increasing magnitude?

I made a little tool to examine the distribution of quasars in various catalogs, including SDSS DR16Q: If you check the +/- box, and move the magnitude slider from low (-20) to high (-30), the peak of ...
MikeHelland's user avatar
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1 answer
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Clarification regarding the meaning of Universal Time UT1

I've been reading the book "From Sundials to Atomic Clocks: Understanding Time and Frequency" by James Jespersen and Jane Fitz-Randolph which is available at https://www.nist.gov/system/...
russell.price's user avatar
3 votes
0 answers
48 views

Authoritative Reference for Astronomical Constants

Is there a reference that is considered authoritative when it comes to astronomical data, especially for the planets and their satellites and the Sun? I've been using the most recent CRC Handbook of ...
1 vote
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What creates the Global Dipole Magnetic Field in the Sun?

I understand that the Sun undergoes convection and with rotation, the convective cells have a helical motion because of the Coriolis Force. My confusion comes from the fact that via the right-hand ...
M-Conn's user avatar
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1 vote
1 answer
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Luminosity and absolute magnitude relationship

Context : an exercise gives the temperature, mass, distance and apparent magnitude of Sirius B and asks to calculate its density. One key step of the calculation is to get the luminosity from the ...
quantum_unicorn's user avatar
3 votes
2 answers
543 views

Is it possible, by monitoring the brightness of stars, to find a “copy of the Earth + Moon” near them?

More than a dozen Earth-like planets have been discovered around nearby stars based on observations of changes in the brightness of their sun as they pass across its disk (transit events). If an Earth-...
Ванек Огонек's user avatar
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0 answers
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How is a complete image of a distant object formed with an obstruction in the line of sight? [duplicate]

Can anyone please link to or sketch a diagram demonstrating how a complete (and clear) image can be formed of a distant celestial object with a central obstruction blocking part of the line of sight ...
flextempers's user avatar
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0 answers
49 views

Why does a total solar eclipse happen every 18 Months?

What is the math involved in calculating how often a total solar eclipse happens. Can you predict it by just looking at the period of the moon around the earth and the period of the earth around the ...
244529's user avatar
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The expectation value of intersecting particles

If I have a light beam (a straight line) it goes through a box of dust, which has travelling length $l$, dust molecule cross section $\sigma$, dust number density $n$. how to calculate the expectation ...
Firestar-Reimu's user avatar
2 votes
1 answer
68 views

$1°$ shift in sun's sidereal position over a day

I couldn't understand the bold lines in the following excerpt (from the book "Astronomy - Principles and Practice 4th ed. - A. Roy, D. Clarke") The month is the next period of any ...
some random person's user avatar
1 vote
1 answer
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Determining star position and velocity to deduce closest approach?

I am trying to replicate the results found for Gliese 710's closest approach of ~0.05 parsecs in 1.3 million years approximately. I thought that by plotting the sun at (0,0) and using the stars ra,dec,...
user2279603's user avatar
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2 answers
126 views

$30°$ shift in a star position w.r.t earth over a month

I couldn't understand the following excerpt (from the book "Astronomy - Principles and Practice 4th ed. - A. Roy, D. Clarke") The month is the next period of any significance to our watcher....
some random person's user avatar
0 votes
1 answer
33 views

Measuring distances between the stars

If we know how far away are the two known stars from Earth, then is it a safe bet that we can know how far apart those two stars are from each other using sine rules? Does that mean we must first ...
user6760's user avatar
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1 answer
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(Astrophysics) How to calculate photons detected by a radiometer over a period of 10 seconds?

I know the Flux (calculated from flux density), and frequency but i dont think I have area. This is the question, it is part d and ive done all other parts: "Consider three widely separated ...
jedijessop's user avatar
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1 answer
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How is the trajectory of a star found relative to the Sun?

So i know we can get radial velocity by measuring blue shift and then we can use the distance to the star and its proper motion to get its tangential velocity. In the case of Bernards star, its ...
user2279603's user avatar
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0 answers
55 views

Determine the equation of earth's orbit

I am trying to find the the equation earth's orbit using Kepler's Scheme. After every 1.88 years Mars returns to its initial position in the sky. With reference to the diagram and data below find the ...
sameed hussain's user avatar
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0 answers
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Is there a galactic "goldilocks" region in the galaxy

I'm wondering if there's a region where the star density in the galaxy create the conditions in outer space where the galactic temperature is between 0 and 200°F. This may cause a ring shaped where ...
Matt Staab's user avatar
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1 answer
100 views

Estimate Saturn's mass [closed]

How can you estimate Saturn's mass using data from Cassini's final moments in September 2017 (apoapsis on September 12 at 1:27 a.m. EDT Saturn time at a distance of about $1.3*10^6$ km from Saturn, ...
Enkt Enktson's user avatar
2 votes
1 answer
89 views

Einstein's derivation of stellar aberration formula: replacing the direction of the ray with a difference in angles justified?

I was going through the translation of Einstein's 1905 paper "On the Electrodynamics of Moving Bodies"(See https://einsteinpapers.press.princeton.edu/vol2-trans/175). In deriving the stellar ...
JKrsl's user avatar
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1 vote
1 answer
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Do the colder and warmer poles of the CMB's Axis of Evil corresponds to the terrestrial poles?

Does the terrestrial North or South Pole correspond to the colder and warmer poles in the CMB, as differentiated by the 'axis of evil'? If so, which to which?
Svenn's user avatar
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2 answers
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Observing an event horizon while approaching one

A thought crossed my mind that I realized was hard to conceptualize so I decided to simplify the question by putting it in terms of event horizons. If I am an observer approaching black hole "A&...
Diniden's user avatar
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0 votes
1 answer
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Is there any tools for observing magnetic fields and forces of black holes and galaxies?

I want to know about how we can find magnetic forces and fields in space around stars, planets, galaxies, pulsars especially pulsars. How (by what means) did determine magnetic fields around a pulsar?
QQQ's user avatar
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1 vote
2 answers
129 views

Is cosmological redshift associated with recession velocity when the light left or when it arrived?

Is the cosmological redshift $z$ associated with the recession velocity when the light left, when it arrived, or something in-between?
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1 vote
2 answers
155 views

Why is $G*M_{sun}=4\pi^2$ when using AU/year units?

So, when using AU/year units, it turns out that 3rd Kepler Law: $\frac{r^3}{T^2}=\frac{G*M_{sun}}{4\pi^2}=1$, meaning $G*M_{sun}=4\pi^2$, any easy explanation for this? Cheers.
Ruba18's user avatar
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Derivation of the coherence length of the light coming from a star

Consider a star perceived under an angle $\alpha$ from the earth. In the Hanbury Brown Twiss experiment, they say that the coherence length $L_{coh}$ of this light is given by $$ L_{coh}= \frac{\...
Nicolas Schmid's user avatar
1 vote
0 answers
115 views

What is the reason for slanting of (Solar) analemma?

Why is a (solar) analemma, photographed (Multiple exposure imagery)in the morning or afternoon at latitudes other than geographical poles or the equator, slanted? (For further examples of slanting ...
Jacob Miller's user avatar
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0 answers
33 views

How do you find the extinction coefficient for Gaia photometry?

I have Gaia photometry g, bp, and rp. My final goal is to find the photometric temperature but first I need to account for reddening by finding the extinction coefficient. I’m really stumped on how to ...
Snav's user avatar
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27 votes
2 answers
6k views

Is the speed of Earth's spinning constant over a given 24 hours?

Is the speed that the Earth spins on its axis constant over the course of 24 hours? As opposed to does it turn faster and slower during different hours over any given day even by a very small ...
JohnTrainor's user avatar
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0 answers
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Does the Earth's magnetic field lag behind the Earth as Earth orbits the sun?

I imagine that when the earth orbits the sun, the earth's magnetic field is also subject to the sun's gravity, since photons and light are subject to gravity. As a result, the magnetic field does not ...
garmichaels's user avatar
1 vote
1 answer
103 views

Measured Value of Hubble's Constant [duplicate]

As we know, Hubble's Constant is not exactly a constant, but its value varies with time. However, we also speak of measuring its present-day value. The measurements by cosmic distance ladder would ...
V Govind's user avatar
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