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Questions tagged [fundamental-astronomy]

Questions involving basic astronomical concepts or information.

46
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3answers
10k views

If Earth is tilted, why is Polaris always above the same spot?

Why is Polaris, the North Star, always above (or near) the North Pole? If Earth is tilted, Polaris' path should be in winter 23 degrees away from its path in summer, or not?
22
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4answers
2k 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, ...
22
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2answers
1k 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?
18
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2answers
3k views

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 ...
13
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2answers
625 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 ...
12
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2answers
393 views

How to discover Neptune from the Uranus orbit (by computer simulation)

I would like to demonstrate the existence of another planet (Neptune) by studying the discrepancy between the observation of the Uranus orbit and the mathematical prediction, this work was made from ...
12
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1answer
1k views

Was the progress of astronomy in the 1800s surprisingly slow, and if so why? [closed]

The 1800's was a century of fantastic scientific discoveries in chemistry, geology, biology, engineering and so on. Is it correct to say that astronomy did not keep up with this development? And if ...
10
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2answers
164 views

How can I contribute to the scientific community using my telescope?

I've been using my Meade 90 ETX for a few years trying to become a better astronomer and am familiar enough with the basics to navigate my way around. I was wondering in what way an amateur astronomer ...
10
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1answer
13k views

Calculation of right ascension and declination

I am confused about this problem: If I see an object from Mount Teide (longitude is 16"30'E and latitude is 28"18'N) that passes the meridian (azimuth=0) at 5h (am) UTC, and I also know that the ...
8
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2answers
2k 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 ...
8
votes
2answers
1k 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?
8
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1answer
442 views

Astronomical databases for machine learning?

I was reading this question about open problems in astronomy. The bounty-receiving answer says that I have just left the field where some colleagues are trying to develop some software to use ...
8
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2answers
352 views

How well can we in principle determine $T_{\textrm{eff}}$ of a star?

This is a question about the basics of astronomy, which I have never happened to see a good discussion for. It is about how well would we be able to measure effective temperature of a star, if we had ...
8
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0answers
171 views

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 ...
7
votes
3answers
995 views

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 ...
7
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2answers
313 views

Why do we use FITS format for scientific images especially in astronomy? How is it different from formats such as JPEG, PNG etc?

I am new to astronomy and I found that the telescopic dataset can be stored in the FITS format instead of JPEG. Why do we have a special image format just for scientific images?
7
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2answers
178 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?
7
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2answers
330 views

Why does each and every planet of our solar system have an unique axial tilt angle?

Why do planets have an axial tilt? From the above image we can see that each planet's axial tilt angle varies and differs from the others. What was the cause of this, was this from the beginning of ...
7
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2answers
3k views

Which came first: Galaxies <=> Stars <=> Planets?

If a galaxy is defined as a collection of planetary systems (and all matter in between), and a planetary system is defined as a collection of planets circling a star (and all matter in between), and a ...
7
votes
1answer
6k 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 ...
7
votes
1answer
386 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 ...
7
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3answers
1k views

Where to obtain Tycho Brahe's data?

I would like to obtain Tycho Brahe's data on Mars. What would be an authoritative source? One source I could find is this page (the data is given as an Excel file) but I have no idea can that be ...
6
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2answers
668 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 ...
6
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3answers
554 views

Is there a flaw with the newer purposes and correlations attributed to the HR diagram? (And would a third axis of mass correct the enclosed flaw?)

When I was younger, I was looking at HR diagrams, and began to experiment with the HR diagram. I was looking at plotting different groups of stars on the HR diagram when I found RV Tauri stars. ...
6
votes
1answer
241 views

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 planets than Mars, Earth and the Sun (...
6
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2answers
223 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. ...
6
votes
1answer
305 views

How were the orbits of planets first mapped out?

I'd like to know how the orbits of planets were first 'mapped out' and to understand the maths behind it. e.g. How do we know what position in space a planet will be at certain time so that spacecraft ...
6
votes
2answers
383 views

How can we be 13.2 billion light years from another galaxy?

How did we get 13.2 billion light years from the faraway galaxies being discovered with Hubble? If we all started near each other at the Big Bang, and we all travelled slower than the speed of light, ...
6
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2answers
1k views

How to plot orbit of binary star and calculate its orbital elements?

I have a set of dates, position angles ($\theta$) and angular separations ($\rho$) for visual binary star. For example: ...
6
votes
1answer
4k 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 ...
6
votes
4answers
245 views

Image sets for testing stacking algorithms?

I am looking for sets of astronomical images for testing different kinds of stacking algorithms. The idea is simple: if one has $N$ images of the same object, the signal-to-noise ratio of the ...
5
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4answers
3k views

Which is more rare: Lunar eclipse or Solar eclipse?

Which is more rare: Lunar eclipse or Solar eclipse? Please explain why either one is more rare than the other. Thank you in advance for your inputs.
5
votes
3answers
219 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 ...
5
votes
1answer
203 views

How to know that the 21cm Hydrogen line is the actual emission and not any other redshifted line?

Is it possible that we mistake some other wavelength emission to be 21 cm because of redshift?
5
votes
1answer
1k views

Calculating Angular Distance

Given the horizontal coordinates of two objects in the sky, how does one go about calculating the angular separation between them?
5
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2answers
772 views

Location on (or in) the celestial sphere

First off, I apologize if I am breaking any site-etiquitte. Secondly, this is probably extremely elementary. For a lab, I was given the question: When we are sitting in a planetarium, where are ...
5
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3answers
104 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 ...
5
votes
1answer
1k views

How did Copernicus get the idea of heliocentric model?

The heliocentric model marked the beginning of modern astronomy. But what were the reasons which led Copernicus to think that the earth orbited the sun. I've read that his model was based on ...
5
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1answer
227 views

Coordinate transformations between reference frames in spherical astronomy

Suppose there are two observational frames of reference with origins $O$ and $O'$, respectively, separated by some constant distance. A body located at point $P$ has Cartesian coordinates $\left(x,y,z\...
5
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2answers
295 views

What exactly is 'eastward movement'

I am reading a book on spherical astronomy. Surprisingly, my problem is not with the mathematics. The author mentions several times words like 'eastward movement' and 'westward movement'. For example, ...
5
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2answers
221 views

K-Pg asteroid impact

Is it possible to determine what daytime the Chicxulub impactor striked the Earth 66 mya? Was it day or night, what was the current phase of the Moon etc.? Can sediments, rhytmites or something else ...
5
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0answers
52 views

Does an algorithm exist that takes an image of the night sky and tell you where in the milky way that perspective likely originates? [duplicate]

In Stargate they talk about using the stars on other planets to figure out their location. I know that's fiction, but it made me wonder if such an algorithm (with arguably little usefulness right now) ...
4
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3answers
660 views

Relation between angular resolution and aperture?

The angular resolution of a telescope is given by $\frac{1.22\lambda}{D}$. This should mean that the smaller the aperture D, the higher the angular resolution. But it is exactly the opposite - why?
4
votes
3answers
123 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
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2answers
1k views

How and when did we learn about the universe?

I'm 13 - I'd like to know how we found/discovered important details about the Universe. I know we have found many different things about the Universe, but when did we find how amazingly large the ...
4
votes
1answer
214 views

Which is the shape of the sky?

I'm a software developer and I'm developing a planetarium and the first thing that I don't know is: What is the shape of the sky? First, I though that it is a semi-sphere, but searching on Internet I ...
4
votes
2answers
245 views

Acronyms of catalogs in SIMBAD database

How to find acronym of specific catalog in SIMBAD database? For example, I want to select stellar names, object types and all binary stars from "Stellar effective magnetic fields. II." catalog (...
4
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2answers
274 views

Creating a rectangular star map

I'm trying to find/create a star map between the declinations of -45 to +60, and need it to be a rectangle. Is there any software/website that would let me create this? Is there a name for this kind ...
4
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1answer
242 views

Sun Zenith angle and location on earth

Let suppose you are at +3 degrees latitude (3 degrees north of Equator ... for example at Cali in Colombia). At what periods of the year will the sun be at your vertical (at your zenith) at noon? I ...
4
votes
1answer
160 views

Speed of light through the ISM and Wavelength

Articles written about fast radio bursts describe the signal's short-wavelength components arriving before its longer-wavelength components, suggesting energy-dependent time delays in the interstellar ...