Questions tagged [fundamental-astronomy]

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

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213 views

Why the Hubble constant is so inconsistent?

Having a look on Wikipedia I noticed the following values (of the last 6 years) for the Hubble constant: 67.6±0.7 SDSS-III Baryon Oscillation Spectroscopic Survey 73.00±1.75 Hubble Space ...
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60 views

Amateur astronomy plan for GCSE students

I'm designing an amateur astronomy observational plan for GCSE Astronomy students here in the UK. I would like some advise to the suitability of what I have selected as the content. For the beginner ...
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What is meant by ionization states?

I am going through the theory of saha equation but I am not able to understand the concept of ionisation state? What are ionization states actually?
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55 views

Coordinates of the Moon [duplicate]

How does one compute the right ascension and declination of the Moon at a given time (or for that matter, the altitude and azimuth)?
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107 views

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. ...
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1answer
60 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 ...
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2answers
187 views

Why Can’t we make a star [closed]

If we know that the reason a star burns without oxygen and fuel is that it converts hydrogen into helium and we have these two elements on earth then why can’t we make a star on our planet
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2answers
2k views

Why don't planets give off their own light? [closed]

Why don't the planets glow like stars?
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3answers
207 views

Basic celestial data

complete beginner here, only got into star gazing a few days ago using my friend's telescope and I don't really understand at all what any of the measurements mean. Anyway, talk about jumping in the ...
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2answers
3k views

How can apparent magnitude be negative?

What is the reason for that scale? Is it because otherwise defining an maximum would be too hard(?). Why do objects that are (apparently) brighter get assigned a smaller number (and down to negative)?
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1answer
189 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 ...
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3answers
91 views

Could space time curve from the vantage point of earth and out into the universe, and would d = 1 / P in that case give false estimates?

The seventeenth century saw a revolution in astronomy. The invention of the telescope and the acknowledgement of the heliocentric system triggered a race amongst astronomers to measure the parallax of ...
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1answer
228 views

Cosmic microwave background radiation: why did it take so long to get here?

I understand that the universe after the big bang was a super dense cloud of elementary particles, and because of this high density was "not transparent" to light. Then, roughly 400.000 years (380....
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1answer
108 views

Questions about terminology used for Mars and its moons

I am having difficulty with some terminology: sub-Martian hemisphere of Deimos ... what place on Deimos does it refer to? leading/trailing apex of Phobos ... what place are those? Apex ... in general ...
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1answer
99 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?
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1answer
79 views

Why do we need the “mean” in mean free path?

I was introduced to mean free path in my astro physics class, and the professor posts a question for us to ponder: "Why do we need the "mean" in mean free path?" This further makes me to wonder what ...
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1answer
77 views

Black holes and time relation

Why Is it said that if someone is being sucked inside a black hole then he/she may see that time is running slowly?
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1answer
76 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 ...
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84 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.
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1answer
46 views

How to find if a set of objects lies within a given resolution (5 arcsec) on a telescope?

I am new to astronomy and I was given the task of finding out if there are objects which can't be resolved by a telescope of resolution 5 arcseconds. I was given the values of RA and Dec of these ...
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1answer
124 views

does a minority of all planetary systems show transits?

do most or only a minority of all planetary systems to show transits? I feel like its minority due to the random orientation of their orbits? But the thing is I seem to find conflicting information. ...
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1answer
978 views

Calculation of hour angle

I need to determine Right Ascension and Declination from Azimuth and Altitude, working in C#. The problem is that the formula for calculating hour angle, for some reason, doesn't work. Here's the code:...
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3answers
970 views

Calculate time when star is above altitude 30°

To find the best observation time for an object, I'd like to calculate the time when it is 30° or more above the horizon. Local Sideral Time would be sufficient. To include that in my program, I need ...
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68 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 ...
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1answer
87 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 ...
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1answer
230 views

What should I read next after Neil deGrasse Tysons “Astrophysics for people in a hurry”? [closed]

I really liked the clever way the author explained stuff in this book but I already understood most of it. Neil himself states in the book that if you are not in a hurry and want to know more about ...
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82 views

Does anyone knows the origin of the Maunder Minimum and Dalton minimum?

Solar spots seams to be a good indicator of solar activity. Does anyone know the reason for the Maunder and Dalton minima?
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83 views

How long would it take to collect a certain amount of photons? [closed]

So, I've received this question to solve, it's not a very advanced one, though advanced enough to cause headaches. The situation is as follows: Say, you are observing with a telescope with an ...
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57 views

Attempting to determine astronomy values in a parameter file

Recently I inherited quite a few old QuickBasic programs which perform various astronomical calculations. I'm attempting to understand these programs and rewrite some of them in Python. I do not ...
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Star Formation in the future [duplicate]

From what I understand stars form in dense clouds of hydrogen and helium molecules. Only so much hydrogen and helium were "created" from the Big Bang or rather formed if you may. Is it conceivably ...
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87 views

Can an astronaut ever reach a Black Hole theoretically? [duplicate]

Ok, bear with me, while I try to explain the question I have. I read that time slows as we approach a black hole. So, suppose,theoretically, as astronaut is approaching a Black Hole. And he gets ...
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1answer
147 views

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

How do you determine the temperature of a star by color?
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1answer
273 views

What are Thorne-Żytkow objects?

Last night I was randomly surfing astronomy pages and came across this.I searched up Wikipedia and other sites,but it doesn't exactly give me enough information about their characteristics.
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114 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?
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1answer
34 views

US observations relevant in UK?

When I listen to the Planetary Radio podcast, there is a section at the end where they suggest objects to look out for in the night sky. If I am in the UK, but they are talking about the USA, will I ...
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1answer
72 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 ...
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1answer
68 views

Frequency of transit in planar and non-planar planetary systems

Supposing that another planetary system is in one plane like our solar system, if let's say that the transit of one planet is visible then is it safe to also assume that all planets in the system must ...
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1answer
166 views

Local sidereal time interpretation

I am new to this domain and trying to understanding the fundamentals of local sidereal time. Through an online available calculator https://www.iiap.res.in/personnel/reks/software/javascript/calclst....
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1answer
5k views

What is the shape of the Sun's orbit around the Earth taking into account elliptical orbits?

Consider the non-inertial frame that is at rest with respect to the Earth's revolution around the Sun. (Ignore the Earth's rotation around its own axis.) My question is, what is the shape of the Sun'...
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1answer
44 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?
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103 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 ...
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1answer
323 views

Nodes and declinations of Moon

This nice page from NASA has the possibility to create an astronomical events calendar for a certain period. I tried to do that for the year 2017 for Central Europe. What comes out puzzles me: On ...
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1answer
67 views

applying nutation to ecliptical coordinates (apparent position of star)

I'm trying to calculate RA and DEC with nutation correction. The direct calculation in MEEUS Page 151 can't be used for stars close to celestial poles and I thought I'd turn RA/DEC into ecliptical ...
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1answer
2k views

Who is considered as the father of modern astronomy? [closed]

Googling is giving me both Galileo Galilei and Nicolas Copernicus as the answer. I am sorry and will remove this question if it is an opinion based question.
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1answer
266 views

Calculating azimuth from equatorial coordinates

I try to get the azimuth of an object from its equatorial coordinates using this formula: $a = \arctan2(\sin(θ - α), \sin φ * \cos(θ - α) - \cos φ * \tan δ)$ Where φ = geographic latitude of the ...
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1answer
467 views

Converting ecliptical to equatorial coordinates

When looking for a formula to convert polar ecliptic geocentric coordinates of an object to equatorial coordinates I find various sources that give these formulae (like Wikipedia): Declination $δ = \...
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1answer
83 views

Which force makes planets to continuously revolve around their parent star?

We know that planets revolve around their parent star (or specifically Barycenter), they maintain a specific speed of revolution so that they don't end up smashing into their planet star. Which force ...
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Draw celestial sphere [duplicate]

How to draw ecliptic if First point of Aries and First point of Libra are known. How to draw the angle between equator and ecliptic and know it's direction.
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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 ...
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1answer
55 views

Books describing first-hand experience of astrophysicists finding planets without skipping actual maths

Are there good references of astronomical texts where we get a first-hand experience of astronomers uncovering astronomical gems using maths alone and not using observation. Observation may have been ...