5
votes
1answer
51 views

Population of excited H levels in a Strömgren Sphere

In chapter 2.2 of Astrophysics of Gaseous Nebulae and AGN Ostriker and Ferland claim that, as far as ionization is concerned, one can assume all atoms to be in the ground state in a Strömgren Sphere ...
0
votes
3answers
106 views

What is the temperature 55 km beneath the surface of Mars?

What is the temperature 55 km (34.18 miles) beneath the surface of Mars? The reason I ask is that I want to know if it might be habitable for a possible future colony if they could dig that deep (...
-7
votes
1answer
136 views

Why aren't people going to The Moon any more? [duplicate]

In 1969 America landed on the moon, and at that time our technology was not as good as it is now. So my question is, we have much more advanced technology than in 1969, so why are we not utilising ...
0
votes
1answer
48 views

At what depth on Mars would the atmosphere have equal pressure of that on Earth?

I know the atmospheric pressure on Mars is less than that of Earth, and so is its gravity. However, I know that the deeper you go (e.g. in a cave or a hole that is dug), the more atmospheric pressure ...
1
vote
2answers
114 views

How to make a telescope for viewing planets, moon and DSOs using a convex lens of aperture 100 mm and focal length 200 mm and other lenses at home?

I wanted to make a telescope with DIY things lying around in home. I read up that the aperture was a very important aspect and thus bought a convex lens with 100mm aperture and 200mm focal length, to ...
0
votes
0answers
23 views

Directly calculating lat/lon of a satellite directly from RA/declination

I have RA/declination values of a satellite and the observer's location in terms of lat/lon. I want to convert the values for satellite into lat/lon. I have tried to use the method which uses ...
3
votes
1answer
77 views

How come the northern and southern lights are the same?

Not an expert, hence the question. To my knowledge the magnetic field of the earth travels south to north. Wouldn't there be a bias on whether the charged particles causing the auroras are negatively ...
0
votes
0answers
27 views

How to Calculate Parallax Angle [duplicate]

I understand that parallax "is a displacement or difference in the apparent position of an object viewed along two different lines of sight" - Wikipedia. So, when calculating the distance from the ...
1
vote
1answer
50 views

UTC to UT1 time corrections

Astronomic observations in geodesy. It is well understood that sun and star positions may be expressed in Greenwich hour angle and declination. Or Right Ascension Declination. And may be published ...
0
votes
0answers
4 views

DUT time offsets to UTC [duplicate]

Astronomic observations in geodesy. It is well understood that sun and star positions may be expressed in Greenwich hour angle and declination. Or Right Ascension Declination. And may be published ...
1
vote
2answers
68 views

Tripod mount missing!

I have received a new Celestron Powerseeker 127 (a 5' short Newtonian), however it came without a tripod mount. Ideas or suggestions on how to procure the right mount our a suitable alternative ...
3
votes
1answer
145 views

Do stars tend to fuse all hydrogen even when the mass is small?

Suppose a brown dwarf requires only one more hydrogen atom to become massive enough to start fusion, what will happen if we add a hydrogen atom to it? It fuses until the mass is dropped and then ...
0
votes
1answer
34 views

Moving-Cluster method for determination of the distance of Hyades. A starter problem

I am currently following a class of observational astronomy lab. I will present a brief description of the method in first and then proceed to the question, so anyone is welcomed to read the entire ...
1
vote
2answers
120 views

Why did Mercury not appear to transit through the middle of the sun?

Why did Mercury not appear to transit through the middle of the sun (the equator)? I initially thought that this was because of the ecliptic, but, then I thought that actually we'd see it above the ...
0
votes
0answers
37 views

radio white dwarfs

We have discovered about 2500 radio pulsars. Part of them show pulsations in other bands like X-ray and gamma ray. The radiation mechanism remains unclear now. I wonder whether there are radio ...
-1
votes
1answer
32 views

Topography / elevation data of Mars

For a design project I'm looking for elevation data for Mars' surface - the idea is to replicate a surface area of Mars as a physical model, using the elevation data to create a very rough 3d model of ...
3
votes
1answer
58 views

How many stars are there in a Globular Cluster of 10^5 solar masses?

I was wondering whether there is an easy way to approximate the number of stars in a Globular Cluster (GC) with 10^5 solar masses. Can one, for instance just assume the GC is made of sun-like stars ...
1
vote
1answer
77 views

How can we explain high redshift numbers?

I just finished an introductory astrophysics course$^1$ and I have a lingering question that I can't seem to resolve. We learned that for the first few hundred million years, the universe was pretty ...
3
votes
1answer
70 views

Likelihood of extra planets in systems identified by Kepler?

Kepler has found some systems with multiple planets and shown that it's likely that 7% of sun-like stars have Earth-like planets (video). I don't think we know enough about extra solar planets to ...
1
vote
1answer
107 views

Why was the size of the solar system not defined by Mercury Transits?

The first measurements of the (absolute) size of the solar system was made using the Transit of Venus, an event that arguably will only happen twice in a lifetime. Transits of Mercury occur far more ...
5
votes
1answer
101 views

What would the night sky look like if the interstellar medium didn't exist to absorb or block light?

I was curious about how much brighter it would be and how much further we could see.
0
votes
1answer
67 views

Redshift to calculate age of stars

In multiple articles I have seen the age of a star, within the milky way, referred to as its redshift (typically denoted by $z$). I know that $z$ can be calculated as $z=\frac{\lambda_{obsv} - \...
0
votes
1answer
52 views

LLR & Orbital Motion

As I understand it, light that is emitted from a source is not imparted with the motion of the source and so always follows a "straight line". If this is correct, I am having a difficult time ...
0
votes
1answer
214 views

Why aren't all planets in the same plane?

Obviously all planets are not in same perfect plane. Because if at all they were in the exact same plane, it would mean that Mercury transits and Venus transits would not be that rare. Any ...
3
votes
3answers
390 views

Do all the stars visible to the naked eye belong to Milky Way?

It is surprising that even late in 1920, people do not know there are galaxies besides the Milky Way. Does this mean that all the stars visible to the naked eye are near to us?
1
vote
1answer
42 views

Intuitive explanation for why the universe is flat

I went through Prof. Hitoshi Murayama's online lecture where he describes why the universe is flat. One of the evidences for a flat universe is the evenness of CMB radiation on all directions. My ...
1
vote
3answers
59 views

Would a telescope that uses Fresnel lenses be more practical than using regular lenses?

If we were to make telescopes with Fresnel lenses instead of regular lenses, would it be more practical? Would this also allow for much bigger telescopes to be made? Here is an example of the type ...
0
votes
2answers
51 views

General question on Solar Eclipse

Let's assume 'solar eclipse' occurred Now, at what degree 'moon' will be in 'with reference to' earth (and) at what degree 'moon' will be in 'with reference to' sun In other words, by 'how many ...
0
votes
2answers
55 views

What visible star is closest to the ecliptic?

If we were to project the ecliptic out as an infinite plane, what visible star (besides the sun) would lie closest to it?
0
votes
1answer
45 views

Metalicity and age of bulge stars vs halo [duplicate]

From what I understand of current models, the bulge of the galaxy formed first, and thus, would contain older population II like stars. Currently, however, the halo has a higher population of stars ...
4
votes
1answer
159 views

Chemical reactions in white dwarf and carbon allotropes

White dwarfs consists mostly of carbon and oxygen. In my opinion, they are too hot to contain these elements in molecular form and hence chemical reactions does not happen (I think resulting CO2 will ...
-1
votes
1answer
45 views

Calculating Orbital Period

I was using this formula to calculate the orbital period of a satellite in days: T = sqrt[(4*pi^2)*R^3/GM-center] Where R^3 is the radius of the orbit, or distance of the semi-major axis, G is ...
3
votes
2answers
98 views

Why (actually) aren't ground-based observatories using adaptive optics for visible wavelengths?

Adaptive Optics (AO) techniques allow ground based observatories to dramatically improve resolution by actively compensating for the effects of Astronomical Seeing. The atmospheric effects are quite ...
0
votes
2answers
127 views

Are we made of stars we're seeing? [duplicate]

a fresh astronomy enthusiast here. Recently I've been reading upon how immensely far other stars are from our solar system and how is it possible that we may be seeing stars that are already dead. My ...
-3
votes
2answers
147 views

Is it possible for the Sun and the Moon to crash into each other? [closed]

Is it possible for the Sun and the Moon to crash into each other? If yes, under what conditions? If no, why?
0
votes
0answers
21 views

Can dark matter be explained by a nearby universe? [duplicate]

There is a conjecture in string theory wich says that dark matter is the result of a nearby universe. Suppose we live, to make things imaginable, in a line on a very small cylinder, then on the other ...
-4
votes
2answers
94 views

Was NASA's moon mission completely fake? [closed]

I really want to know whether NASA's Moon mission really was a hoax, or if it is a fact. Since there are many points and scenarios which proves it as being filmed in a film studio with controlled ...
0
votes
1answer
41 views

Why weren't the Hubble light-echo images of V838 Monocerotis supplemented by ground telescopes?

Drawing from this answer The V838 Monocerotis expansion (not a supernova) and the observation of the subsequent "spectacular" light echo was quite a notable event! From Nature 422, 405-408 (27 ...
0
votes
0answers
47 views

Does a self-gravitating gas necessarily develop turbulence?

Though we may still doubt the exact driving mechanism of turbulence in each particular case (ISM, MC, circum-BH/-stellar discs, atmospheres...), can I say that in a sphere of dark matter particles no ...
0
votes
2answers
90 views

Solar Elevation Angles — Anomaly?

"The solar elevation angle is the altitude of the sun, the angle between the horizon and the centre of the sun's disc." - Wikipedia The meridian is when the sun is directly facing earth and is at ...
0
votes
1answer
85 views

When was the nearest star discovered? [closed]

When historically did we realize that the Sun is a star, like all the others? An answer was posted, then the question was put on hold. I would like to answer: If indeed someone asserted that the Sun ...
3
votes
1answer
49 views

Why Free-Free emission is regarded as Thermal emission?

I read that thermal emission/radiation are the ones whose spectra is similar to that of a Black body radiation. Also thermal radiation depends solely on the temperature of the object. How can we ...
0
votes
1answer
41 views

How to calculate the pixel size and beam size of an image?

I have an image with some sources in it. I need to get the pixel size and beam size of that image. How can I calculate it?
0
votes
0answers
44 views

Which frequency should be used to communicate with a cube satellite?

I am trying to build a cube satellite using a raspberry Pi. I am trying to figure out which radio frequency could be used to communicate with the cube sat to transfer data like images, videos, ...
0
votes
0answers
50 views

Why did time progress past the singularity?

I hope this doesn't sound stupid but I've always wondered: Why didn't time stop with the singularity before the big bang? I might be mistaken but doesn't time slow in proportion to the distortion of ...
1
vote
1answer
178 views

What is the first recorded reference to the Moon being a satellite of the Earth?

I saw a list recently of the moons of the various planets and the discoverer(s) and date of discovery. Earth's Moon was listed as Unknown. I know you don't 'discover' a huge disc in the sky. But ...
4
votes
2answers
59 views

Why do post main sequence stars enter the red giants branch?

I am an early graduate student in astronomy and have hard time understanding why do post-MS stars move up the RGB. Here is what I understand about post main sequence evolution of stars. As their ...
1
vote
1answer
134 views

Why can't neutron stars ignite and explode?

Beyond the Chandrasekhar limit, white dwarfs become extremely hot. As a result, previously unfusable carbon can become fusable, causing nuclear reactions. This leads to thermal runaway and ultimately ...
8
votes
2answers
119 views

Boötes Void numbers, 2016

As a general science (hence Wikipedia!) reader, the latest information I have is that 60 galaxies "have been found and counted" inside the Boötes void, this of 1997. (1) What is the latest count of ...
0
votes
0answers
19 views

How to calculate the LST of an astronomical object at a given height above the horizon [in degrees]?

My situation: I want to observe M52 at RA = 23h24m48s, DEC = +61deg35arcmin36arcsec from, let's say, Calar Alto at 37.23deg N and 2.546deg W. How can I calculate the Local Sidereal Time (LST) at ...

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