Astronomy Stack Exchange
Astronomy Stack Exchange

Questions tagged [fundamental-astronomy]

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

IAU Division A is responsible for fundamental astronomy.

The scientific community of Division A:

  • provides definitions and models that describe reference systems and frames used in astronomy to determine positions and motions of celestial objects in space and time;
  • investigates dynamical behavior of celestial bodies including both high-accuracy descriptions for shorter periods of time and evolution over extended periods of time;
  • obtains physical information on celestial objects and investigates physical laws using the methods of astrometry and celestial mechanics;
  • offers services that provide data and ephemerides of solar system bodies, Earth orientation data, time scales, astronomical constants, models including relevant software procedures, etc. for users within the astronomical community as well as within society.
142 questions
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What would the night sky look like if the Milky Way were the only galaxy in the universe?

I'm curious to know what the sky would look like without any other galaxies out there. How much do other galaxies factor into the stars we see? Does the Milky Way account for most of them? Would the night sky look normal? Or would it be very empty?
J.Todd
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Are there more stars than all the words ever spoken by humans?

A while ago I saw Neil deGrasse Tyson comparing the number of stars in the universe with the number of words spoken by all of humankind, ever since. I realize both of these numbers are not strictly defined, but still, we can use our best…
Jens
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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 astronomer, I would think there are many more…
LocalFluff
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Astronomical ABCD...!

Today, I thought to make a list of Astronomical objects, A to Z. It goes as follows : A - Asteroid B - Black Hole C - Comet D - Dwarf Planet E - Elliptical Galaxy F - Falling Star G - Globular Cluster H - Hypergiants (Stars) I - Interstellar…
Jaideep Khare
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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 it has to do with the position of the earth and…
rafael.js
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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 relative to the sun rather than Earth, as that…
Eric J.
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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-year course in the fundamentals of applied…
hlritter
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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 the Moon to be half lit. By observing the angle…
user8314628
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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: $\nu - M = 2\varepsilon \sin M$ (1) where $\nu$ is the True Anomaly of the…
Spencer Rugaber
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Tips for a beginer who wants to learn more about astronomy

I have completely no idea about astronomy, but I am starting growing interest in it as I have been always wondering on what has been discovered out there and since I am studying CS, maybe I will learn more than I think as CS and astronomy as…
Κωνσταντίνος Κορναράκης
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Is it possible to calculate the time of day given latitude, longitude and solar elevation angles (zenith, azimuth, elevation)?

I am trying to determine the time of day of some images I have. I know the lat/lon, the day and year of image. I also know the 3 solar angles (zenith, azimuth, and elevation). Is there MATLAB or any other code that can do this…
Andy
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Please take the time to visit Meta!

A lot of you are probably already aware of our meta site, but I wanted to take the time to remind you that it only requires 5 reputation points to participate--and this is a critical part of our site. Meta is where we decide what kinds of questions…
called2voyage
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Are any other planetary bodies warming up as well in the Solar System?

Do we have a few decades worth of surface temperature data to compare?
Logray
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Coordinates of the Moon

How does one compute the right ascension and declination of the Moon at a given time (or for that matter, the altitude and azimuth)?
ruadath
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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 latitude is 90−alt=dec−lat For Northern Hemisphere,…
user28084
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