Questions tagged [fundamental-astronomy]

Questions involving reference frames, time scales, and how they are determined. Not for general Astronomy 101 questions.

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2 votes
1 answer
115 views

What is a "fundamental location", and why is Mosting A defined as one for the moon?

The crater Mosting A was chosen to be the "fundamental location" for the Moon's coordinate system (latitude and longitude). But what exactly is a "fundamental location"? What does ...
2 votes
0 answers
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LSR and peculiar motion corrections to RAVE survey velocities

I am working towards getting a bunch of halo stars in our galaxy for my thesis. I am doing this with the help of a Toomre diagram and I am stuck. I am using the RAVE survey in conjunction with Gaia as ...
9 votes
2 answers
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Why didn't Johannes Kepler use data about more planets?

In Astronomia Nova (1609) Johannes Kepler used observations of Mars in order to refute circular orbits. Throughout Astronomia Nova he hardly even mentions other celestial objects than Mars, Earth and ...
15 votes
0 answers
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Planning to revisit Arthur Eddington's experiment from 1919

As the fateful day draws closer, the United States will host a celestial event that comes once in three generations. I plan to witness this first hand at the exact center of greatest eclipse. In the ...
5 votes
2 answers
3k views

Difference between J2000, FK5 and ICRS coordinate systems? Which one does the Yale Bright Star Catalog use?

I have no background in astronomy. I have been wanting to write code to make star charts for a given location and time, which led to this question. I figured out that I would need to convert the ...
7 votes
1 answer
1k views

On what basis is the information about the distance and velocity of the Voyager probes determined?

Voyager 1 was the first-ever object to reach interstellar space on August 25, 2012 when it passed beyond the sun’s realm of plasma influence (the heliosphere)[...] (source) Although some of their ...
-1 votes
1 answer
106 views

How does Polaris remain constant for millennia if the earth is spinning, orbiting and traveling with the galaxy? [duplicate]

Look at Polaris. Understand heliocentric theory and then reason.
0 votes
0 answers
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How spaghettification is possible at the Event Horizon of a supermassive black hole?

if gravity is too strong then it will break a object apart as gravity is strong enough to break the chemical composition of object why we consider "Spaghettification" relevant in this case ?
4 votes
1 answer
176 views

How can the IAU 2000A vs IAU 2000B nutation comparison be reproduced?

I am attempting to plot how the IAU 2000A nutation model degrades as its terms are omitted. As a spot-check, I decided to compare it to IAU 2000B, which includes only the 77 most important lunisolar ...
6 votes
3 answers
662 views

What do the months and hours mean in Tomas Filsinger's Map of The Universe

I have had one of these in my room for decades: I don't have the booklet that seems to usually come with it, can someone explain to me what the months (with days below it) and hours mean? I imagine ...
4 votes
1 answer
443 views

Have there been studies of "old photons" to see just how constant things like Planck constant has been?

The question Are photons aged? and answers therein have got me thinking: I vaguely remember hearing something about experiments where "old photons" were collected by large telescopes from very ...
2 votes
0 answers
118 views

Why do astronomers use the equatorial coordinate system that moves, instead of one based on fixed, distant stars?

As an outsider to the field, I am surprised to learn that astronomers commonly use the equatorial coordinate system, in which fixed stars are not actually fixed. Isn't that making life harder than it ...
3 votes
0 answers
87 views

Is TDB monotonic? Does it or any of its derivatives have yearly discontinuities with respect to an atomic clock?

This in-depth answer mentions that ...TDB is updated every year. As technology improves, these subtle updates change the timing of past events. This makes me wonder... Does this updating result ...
1 vote
0 answers
400 views

evaluate solar eclipse Besselian elements? [closed]

I found this NASA website which says that to predict eclipse, we should solve the Besselian elements ..what does this mean, how can I solve for Besselian elements? Is there a numerical method? I need ...
20 votes
3 answers
6k views

Can a magnetic field of an object be stronger than its gravity?

Can a planet, star or otherwise have a magnetic field that is stronger or have more range than its gravity?
0 votes
1 answer
318 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 ...
1 vote
0 answers
65 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 ...
4 votes
1 answer
157 views

Massive degraded impact crater on Mercury - chemical evidence?

The planet Mercury has a myriad of impact features - this has been known for some time. However, observe in the following images, a relatively large 'High-Mg region' detected on the planet (below): ...
2 votes
1 answer
83 views

Basis of color index

As an amateur astronomer for 60 years and always as interested in the science as in the observing, I thought I had a pretty good understanding of the fundamentals. But I'm distance-auditing a third-...
4 votes
1 answer
304 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.
3 votes
2 answers
2k views

How to determine the eccentricity, knowing the orbital speed and distance

How to determine the orbital eccentricity of a planet, knowing the instantaneous orbital speed of it and the distance from the Sun to the planet at that moment?
5 votes
3 answers
204 views

Does any asteroid we have ever seen have a hot core like earth.?

I was wondering if any of the asteroids we have ever seen has a hot core like Earth's. I'm thinking that Earth has a strong gravitational field and so formation would have involved a lot of ...
2 votes
1 answer
1k views

Making sense of the lomb-scargle periodogram

I am trying to use the periodogram to tell when a signal is periodic or not by following the tutorial for the astropy Lomb-scargle periodogram here. http://docs.astropy.org/en/stable/stats/...
1 vote
1 answer
2k views

How to calculate declination of Moon?

Is there any way to calculate declination of Moon for any day?I'll subtract inclination of Earth on the ecliptic from the result. I'll get Moon's the shortest angular distance from Sun. Thanks for all ...
1 vote
1 answer
268 views

Why the more-luminous star has larger surface area when two stars have the same temperature?

If two stars have the same temperature but one is more luminous than the other, the more-luminous star must have a larger surface area, and therefore a larger radius than the dimmer star. The ...
4 votes
3 answers
307 views

Do interstellar asteroids decelerate and eventually stop?

I do wonder, do interstellar asteroids eventually stop at one point in space after they gradually decelerate (or) even do they decelerate? Though there is no air like on earth and thus asteroids ...
0 votes
1 answer
123 views

Does weight influence Earth's spin? [closed]

If put enough weight on a particular point on Earth's surface disturbing the balance between hemispheres, is it possible that the Earth's spin could change like an unbalanced spinning top?
3 votes
1 answer
180 views

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 ...
1 vote
1 answer
242 views

Luminosities and Apparent Brightness of Two Stars of which one is 8 times the distance of the first star [duplicate]

Suppose two stars have the same apparent brightness, but one star is 8 times further away than the other. What is the ratio of their luminosities? Which one is more luminous, the closer or the further ...
0 votes
1 answer
305 views

The Luminosity of two stars with same brightness but at different PC away

Stars A and B are both equally bright as seen from Earth, but A is 120 pc away while B is 24 pc away. Which star has the greater luminosity? How many times brighter is it?
0 votes
1 answer
742 views

How can the temperature of stars can be determined by their color?

How do you determine the temperature of a star by color?
3 votes
2 answers
3k views

What's the useful magnification for a scope with 70mm objective lens?

Some of the spotting scopes which are e.g. 70mm claim to magnify terrestrial objects at 75x. But yet they cannot produce sharp and clear images at even 30x-35x. While 90mm scopes can do a better job ...
1 vote
1 answer
110 views

Why do most of the myths behind constellations originate from Greek? [closed]

Why do most of the myths regarding constellations happen to have begun from Greek civilization? Why not other civilizations? Most people who lived in the past era probably observed star patterns in ...
2 votes
1 answer
285 views

Simulating Noise in Astronomical Images

I want to add realistic noise to a simulated image but I am a little confused about the process. I want to have some Gaussian random noise representing the readout noise and to also add Poisson noise ...
2 votes
0 answers
489 views

Any ideas for an astronomy + ML project? [closed]

I wish to do an astronomy related project which incorporates machine learning.Do you have any suggestions?
1 vote
2 answers
680 views

How to find the radius of a satellite not knowing the mass

If I know the semi-major axis, the density of the planet, and orbital period.. how can I find the radius of the satellite? I can't think of any formula to use.
7 votes
1 answer
10k views

How many astronomers are there in the world today?

How many now living individuals have a PhD in astrophysics, or by some other definition can be reasonably classified as astronomers? I think Richard Feynman once said that only one in a million is an ...
3 votes
0 answers
66 views

How strong are the stellar flares on YZ Ceti?

Doing research for a game and trying to understand the implications of the stellar flares from YZ Ceti. In short (ignoring the planets for now), if people were to build large space stations of various ...
4 votes
2 answers
4k views

What liquids can be found in the void space?

Is there any material natural or otherwise a free floating liquid that can exist in space? https://space.stackexchange.com/questions/32274/what-liquids-last-the-longest-in-space
2 votes
1 answer
64 views

Obtain IR diffuse data from WISE

I need some help obtaining IR background diffuse data from the WISE observation. There is already some work done in this regard; see: http://wise.skymaps.info/ . These are .fits files. How do I find ...
7 votes
2 answers
505 views

What was the length of the solar day 73 million years ago?

How could this be estimated, or how accurately could it be extrapolated from a present-day measurement of the Earth's spin-down rate?
2 votes
1 answer
139 views

Need help with the calculations/conversion of a celestial object

I'm developing a telescope controller open-source application. I started this project with a very little knowledge of Astronomy. Basically, the app is going to send data to telescope over a wireless ...
5 votes
2 answers
1k views

A curious relationship between lunar periods and the solar year

Earlier today I was exploring the astronomy features on WolframAlpha, when I stumbled upon an intriguing numerical relationship involving the values for the lunar synodic and sidereal months. Using ...
3 votes
1 answer
445 views

Numbers 80 to 85 in Ancient Astronomy

Do any numbers in between 80 and 85 (or thereabouts) hold any relatively important or relatively obvious meaning in ancient astronomy ? A few clarifications: By ancient I mean related to human ...
1 vote
1 answer
240 views

The Solar Motion and the peculiar velocities of stars

Local standard Of Rest is the hypothetical origin of a reference system with respect to which the motions of all stars in some neighborhood of the sun average out to be zero which type of motions of ...
1 vote
1 answer
250 views

What factors determines the size of a galaxy?

Recently i saw a post comparing sizes of different galaxies with the Milky Way. The largest one being the Ic 1011.What makes this galaxy so large? What factors decide the size of a galaxy?
3 votes
1 answer
367 views

Equation of the Center constant factor

This questions concerns the longitudinal aspect of the Equation of Time, also called the Equation of the Center. In some sources the equation looks like the following: $\nu - M = 2\varepsilon \sin M$ ...
8 votes
2 answers
391 views

Planetary reference systems and time

I am researching into how coordinate systems of solar systems objects are created by reading some of the reports written by the Working Group on Cartographic Coordinates and Rotational Elements (e.g. ...
5 votes
3 answers
515 views

Directions to Proxima Centauri

I'm writing a sci-fi novel in which humans venture to the stars for the first time. Their "shake down" cruise takes them to Proxima Centauri. I'm trying to understand where Proxima Centauri is located ...
3 votes
3 answers
154 views

Account for radiation energy in the statement "total energy of universe is zero"

I've read in Hawking's book The Theory of Everything that total energy of the Universe is zero. He explained this by saying that if there are two bodies separated by a distance and having some mass, ...