# Questions tagged [fundamental-astronomy]

Questions involving reference frames, time scales, and how they are determined.

18 questions
Filter by
Sorted by
Tagged with
2k views

### Where can I find/visualize planets/stars/moons/etc positions?

What resources are available to find the positions of planets, stars, moons, artifical satellites, asteroids, and other heavenly bodies?
458 views

### Calculation of Horizontal Coordinates

Given a fixed coordinate location on Earth (i.e. a latitude and longitude), and a fixed equatorial coordinate location of a particular astronomical object in the sky (i.e. right ascension and ...
3k views

### 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 ...
512 views

### Equations for coordinates of solar system objects

I would like to write a program that visualizes the solar system. To do this, I would need equations for calculating the coordinates of each solar system object at a given time. Where could I obtain ...
45 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?
653 views

### Open problems in astronomy that an amateur (with a PhD in some other field) would have a chance of solving?

What are some open problems in astronomy that an amateur would have a chance of solving? Suppose the amateur has a PhD in some other field, owns a basic telescope, a set of filters, diffraction ...
3k views

### How would the night sky look from inside a globular cluster?

When the weather is clear, we can look at the stars. And we normally would see several thousands of them, they all being more than a $\textrm{pc}$ away from us. Now, there are globular clusters, ...
264 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. ...
2k views

### Why you use log to measure metallicity in galaxies?

For example, I saw the next expression for matallicity in a paper: $\log(O/H) + 12$. I understand O/H is the O(Oxygen) to H(Hydrogen) ratio but why is there the number 12? And why the logarithm?
58 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 ...
591 views

### What is the effect of the axial precession on the orientation of the planet's orbits?

I am working on an online application to visualize the positions of the planets and to calculate their ephemerides (you find it here, but it is not complete yet). I do not have much knowledge in ...
5k views

### How to measure the altitude and azimuth of a star?

Given that the star is crossing the local meridian line in a certain location, I've tried calculating the altitude of a star by finding the difference between the declination of the star and the ...
6k views

### How to calculate Longitude from Right Ascension?

Considering that a star of certain declination is crossing the local meridian at the observer's zenith at an unknown location on the earth. Here, the declination of the star is equal to the observer's ...
201 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?
803 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 ...
109 views

### Red shifting galaxies

I am an amateur astronomer please correct if any of my understandings are wrong. We all know that from the Hubble's ultra deep field image the most distant galaxies which were created shortly after ...