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# Questions tagged [fundamental-astronomy]

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

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337 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 ...
108 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 ...
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) ...
447 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
498 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 ...
241 views

### Finding the radius of a star in arcsec

If i know the radius r of a star in cm, how can I convert it to arcseconds? For example, if I have a star with r = 3.18e13 cm, and distance to the star d = 220 parsecs, what is the relation to ...
605 views

### Does a week represent something in astronomy? [duplicate]

I know that a day represent the time for the earth to make a full rotation around its own axis and a year is the time for the earth to make a full rotation around the sun. But does a week represent ...
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 ...
80 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 ...
170 views

### In layman's terms, why do we put the “time” in space-time?

What does "time" mean in the term space-time? I am trying to understand why anything that travels through space, from a proton to massive galaxies, is always referred to as traveling in space-time, ...
152 views

### Requesting book references for a non-expert person with math background or just a non-expert person

I've just finished my masters degree (to be exact previous week ^_^). And I'm completing my collection of applications of my studies. During previous year I started reading about Robotics and Coding ...
113 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, ...
88 views

### If I look beyond (about same region, higher redshift) a galaxy, will I see its progenitors?

Is there a range of redhsift dz, such that if I look at z+dz from a massive object at redshift z, I will see its progenitors? (in a LCDM scenario of halo assembling, with smaller halos evolving ...
2k 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 ...
144 views

### Is there an astronomy exam I can take?

I am currently living in Bangkok and I love astronomy. However, I haven't been able to find an official astronomy exam that I can do to gain college credit. Could someone help me out please?
586 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 ...
46 views

### Photometric redshift

I have decided to do undergraduate thesis on "estimating photometric redshift" or something related to this using machine learning. Reading previous papers, I have come to know that work has been done ...
99 views

### What to do after first year of amateur astronomy? [closed]

I have practiced astronomy as a hobby for a while now. I have an entry-level telescope (6-inch Newtonian). In addition to observing the night sky, I have been studying physics related to optics, ...
57 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 ...
1k views

### Can some stars not emit any energy in the visible spectrum?

Stars convert mass into energy. Even converting the slightest mass into energy is immense because the speed of light is so great and $E = mc^2$. This means that stars have to emit large amounts of ...
117 views

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 ...
53 views

### When black holes forms out of a supernova do they have a very high velocity?

When black holes forms out of a supernova do they have a very high velocity ?? Or do they remains at the position of parent star ??
339 views

### Power of the James Webb Space Telescope [duplicate]

I have heard that the JWST will be capable of looking at the early stages of the universe. However I have also heard that it won't be capable of detecting the Oort Cloud that supposedly provides ...
63 views

### The M-theory to understand black holes [closed]

I am a layman in astronomy. Can someone please explain it to me whether the M-theory can be used to explain what is happening in the centre of the black hole where the singularity exists? Or is it ...
463 views

### If the universe is 'flat', what shape is it? [duplicate]

As in the title, If the universe is considered to be 'flat', what shape is it? Is it a disc, elliptical, square, rectangle? Or is this still unknown as we can only study a small segment of the ...
170 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 ...
92 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 ...
198 views

### Can I learn astrophysics and astronomy with my basic math?

I want to learn astrophysics and astronomy, I'm very interested in it because there are many questions that popped up in my head, and really curious about things, but I'm afraid of a little bit on ...
140 views

### 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?
888 views

### How to calculate position of an unknown star knowing positions of some other stars from an image?

Suppose I know the coordinates (right ascension and declination) of the stars marked with red. How should I calculate the coordinates of an unknown star, marked with yellow? Searching over the web, I ...
42 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-...
171 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/...
49 views

### How does one “use” the Pan-Starrs data?

I've seen that a large block of Pan-Starrs data has been released and is available on-line and how the distributors of the data expect professionals and the general public to use the data in their ...
88 views

### How small a location is possible to identify when any visible star is at its zenith directly above?

How small an area on Earth is it possible to identify with any precision when any celestial object (star, planet, comet, nova) (visible with the naked eye alone) is at its zenith directly overhead? --...
173 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: $\nu - M = 2\varepsilon \sin M$ ...
855 views

### Determining distance from semi-major axis and eccentricity

I am trying to obtain the distance covered by an object in orbit around the earth within a specified amount of time past its perigee passage. The object is in an elliptical orbit with eccentricity 0.2 ...
59 views

### Can angular information be known more precisely than the diffraction limit?

The diffraction limit deals with the ability to determine if two things are separate. I am interested in the ability to find the the centroid of a single object. Imagine a star with no near ...
207 views

### Name and language of symbol in astronomy book

I've been working on a programming project involving Peter Duffett-Smith's Practical Astronomy With Your Calculator (3rd Ed.), which has a large number of mathematical/astronomical formulas in it. ...
44 views

The further away we see, the older states of the world we observe. And the volume of the part of space which is observable, increases by the square of the distance to it. So there should basically be ...
524 views

### How might Thales have predicted a solar eclipse?

Thales of Miletus purportedly predicted a solar eclipse (most likely the solar eclipse of May 28, 585 BCE). The historicity of Thales' prediction can't be verified with any certainty given the ...
109 views

### 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 ...
108 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?
48 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 ...
87 views

### What happens if one day aliens want to talk to us. How can we talk to them? [closed]

Always I wonder about that if some day alien wants to talk to us, then how can we talk to them? They didn't know any of the language on the Earth. What will be the basic building blocks for it?
63 views

### Units of integrated flux density (irradiance) along longitudes

If I've taken an image of the Galactic bulge with the pixel units in MJ per steradian: and I've looked down each column of the image and added up the values: then do the units change? My thinking is ...
103 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 ...
54 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 ...
124 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?