2
votes
1answer
109 views

Derivation of the formula for longitude of ascending node for a satellite

I've been looking into the document IS-GPS-200H to understand how to calculate satellite location in the ECEF coordinate. I am having problem understanding the formula to derive $\Omega$, the ...
3
votes
1answer
74 views

What is the apparent magnitude limit for the naked eye?

If you only read the question, you will answer: ''That depends on the light pollution''. Yes, it does, but if you are in the darkest night sky (Bortle class 1), what magnitude would have the faintest ...
2
votes
1answer
148 views

Hour angle sunrise calculation problem

I am trying to program a sunrise/sunset calculator using this formula tutorial. If you follow the steps, eventually you get to this formula for "H" (the "hour angle"): $H = \arccos( [\sin(-0.83) - ...
2
votes
2answers
101 views

Is it difficult to see DSO in your eyepiece?

I want to know if bringing the image of a DSO in eyepiece generally represents a problem for beginners in astronomy.
2
votes
1answer
57 views

Sloan digital sky survey galaxies

I am trying to get some data from the Sloan digital sky survey (SDSS). This task turned out to be challenging for me as someone with only little knowledge about astronomy and maybe someone here can ...
11
votes
3answers
480 views

How do we know that the speed of the influence of gravity is instant?

When I was in college, I posed to my astronomy professor a thought experiment that had been puzzling my mind for some time: "If the sun magically disappeared, instantly, along with all its influences, ...
1
vote
1answer
64 views

how to measure temperature of the distant star [duplicate]

As part of small project i want to measure temperature of the distant star on basis of optical observations. so by what exact method i can do it? which instruments will be necessary? what is the ...
1
vote
2answers
49 views

Would a low albedo substance warm up Mars?

If Mars were coated in a dark substance that absorbs sunlight (including infrared light), would this heat up Mars? I am envisioning a fine dust that is dispersed into the atmosphere, but possibly ...
3
votes
2answers
105 views

Would a high albedo reflective substance cool down Venus?

If we were to put a highly reflective substance into Venus's upper atmosphere, could we cool it down? I am envisioning adding a highly reflective fine dust or gas, possibly lighter than "air" to the ...
3
votes
2answers
164 views

Accurate way to programmatically generate a main sequence star?

I am working on a (personal) programming project, part of which involves generating random stars and their parameters. In order to create a procedurally generated star, I want to randomly select as ...
3
votes
2answers
60 views

What is the difference between a dwarf spheroidal galaxy and a globular cluster?

This Wikipedia article states that Segue 1 is either a dwarf spheroidal galaxy or globular cluster associated with our own Milky Way. I am wondering what the difference is between dwarf spheroidal ...
5
votes
1answer
77 views

Is dark energy constant?

Does the "amount" of dark energy in the universe change over time, or is it constant? The dark energy I am asking about is the rate of acceleration of the universe's expansion.
5
votes
4answers
161 views

What is the farthest point of light that is emitted by a torch?

If I focus my torch into the night sky,what would be the farthest point the light can reach? Recently I looked at the night sky and noticed a light spark moving around the clouds for about 15 ...
11
votes
2answers
735 views

Is it Possible for Planetary Bodies To Exist In Close Proximity Without Adverse Effects?

There are several sci-fi movies where planetary bodies are shown in the sky in order to indicate that the characters are on an alien planet. A good example is in Predators (2010): Is it actually ...
1
vote
1answer
37 views

Is there a radius inside of which objects are (doppler) blue shifted?

The Andromeda galaxy is about 600,000 light years away and is doppler blue-shifted. Are there objects closer to us than Andromeda which are red-shifted? Are there objects farther than Andromeda that ...
2
votes
1answer
78 views

In regards to the holographic principle, what exactly is information? [closed]

I'm having trouble understanding what exactly "information" is in the context of the holographic principle suggested by string theory. Can it be equated to a matrix of ones and zeros? Does this ...
4
votes
1answer
114 views

What is the explanation for rapid inflation just after the big bang?

I often hear about cosmic inflation occurring rapidly after the Big Bang, but have never came across any explanation for it. What supposedly caused this inflationary period in the early universe? ...
6
votes
1answer
1k views

How can I accurately find & apply the white donut to the center of my mirror?

I have a Plettstone 18" Dobsonian telescope and use a Howie Glatter tuBlug, laser collimator, and Square Grid Projection Attachment to adjust the mirrors. Proper collimation requires an accurate ...
1
vote
2answers
37 views

Rate of star collpse

It is believed that our sun will become a red giant with a diameter of about 1 AU. When the fusion slows down, gravity will collapse the sun. Since the energy release from the fusion diminishes slowly ...
4
votes
2answers
252 views

How did Kepler determine the orbital period of Mars?

As I understand it, Kepler used the orbital period of Mars, along with observational data of Mars' and the sun's position in the sky to derive the orbits of Earth and Mars. (As described, here: ...
2
votes
1answer
19 views

Can spectroscopes identify minerals?

Could a spectrometer on a probe or space telescope identify minerals, not only elements and molecules, from the spectral lines? Is there any technology for identifying minerals remotely?
3
votes
2answers
84 views

how does redshift prove expansion is accelerating?

My astronomy teachers never would answer this for me... Redshift obviously indicates an object (such as another galaxy) is moving away, but how do we know its acceleration from this? It's my ...
4
votes
1answer
198 views

Sun path at poles

At places other than the poles, the sun is seen to "rise" on the Eastern horizon and to "set" on the Western horizon. After a period of night, the sun "reappears" on the Eastern horizon. At the ...
1
vote
1answer
70 views

Finding the radius of an eccentric orbit at any point

Knowing the apoapsis, periapsis and therefore period of an orbit, how can I find the radius of an object in an orbit at a given angle or time, whichever is needed. For example, if I have an object m ...
1
vote
1answer
48 views

Why there are three equations governing blackbody emission?

I learnt that the spectrum of a black body can be explained using Planck distribution Rayleigh -Jeans equation and Weins displacement law Can anyone tell me why there are three different equations ...
3
votes
1answer
96 views

What is the galaxy M87 doing these days?

The massive elliptical galaxy M87 in the Virgo cluster is 53,490,000 light years away. It also contains one of the largest, heaviest supermassive black holes in the known Universe. But it's also my ...
4
votes
2answers
183 views

Can I look at the sky and find the day of the week?

Suppose I wake up from a coma on a desert island in the 19th century (i.e. we already use the Gregorian calendar but have no satellites yet). I have a clear view of the sky and a couple of days to ...
2
votes
1answer
49 views

What is the ratio of cosmic microwave background radiation to normal radiation?

I would like to know the ratio of cosmic microwave background radiation to normal radiation in the universe. I am considering cosmic microwave background radiation to include the microwave, and any ...
4
votes
1answer
165 views

“If earth had rings like Saturn”: A few further thoughts on the consequences

I came across this video recently where artists depicted what it would look like if Earth had rings like Saturn. http://www.wimp.com/earthrings/ Please note: The video contains already some ...
2
votes
0answers
49 views

what will be the exact position of the Thirty Meter Telescope [closed]

TMT will be put at Mauna Kea in Hawaii. It should be near Keck and Gemini. However it seems there is no place left at that site. What is the exact position?
5
votes
1answer
70 views

Do star systems stripped from galaxies have different expected behavior?

Another way of stating this question: Does the fact that a star system (or comparable concentrated mass) exists in a galaxy affect its long-term evolution, in terms of expansion, contraction, ...
1
vote
1answer
193 views

Point Spread Function size: Full Width Half Maximum (FWHM) vs Sigma

I having been studying some astronomy papers related to galaxy observations and I realized that every time they want to express the size of the Point Spread Function (PSF) of a system which can be ...
2
votes
5answers
237 views

Could light be dark matter?

Is it possible that light itself is dark matter? I am speaking of photons (e.g. visible light, infrared, ultraviolet, etc...). I realize light is understood to be massless, but it is obvious it at ...
1
vote
1answer
63 views

Why do rocks on other solar system bodies that have an atmosphere seem to be flat?

Images taken by landers on Titan and Venus and Mars show landscapes where rocks, to me at least, are surprisingly flat. Being used to walking around in forests with roundish meter sized boulders, I'd ...
3
votes
1answer
46 views

Speed comparison of both voyagers

I came across this page which provides (mostly extrapolated) speeds of both voyagers. Assuming they are fairly accurate, any reason why the speed of Voyager 2 (5-6 km/sec) is less than that of Voyager ...
1
vote
0answers
81 views

Why doesn't this paradox disprove (some) multiverse quantum gravitational theories?

As I understand it, one theory of the multiverse is that there are an infinite number of universes separated by small distances in other (than our observable 3/4) dimensions and that gravity is weak ...
3
votes
2answers
86 views

If the Universe is infinite, why isn't it of infinite density?

If we make the assumption that the Universe is infinite, and has an infinite number of hydrogen atoms, then why is it not of infinite density - because, under Schrodinger's wave equation the ...
1
vote
1answer
31 views

Sensitivity of calculated orbital elements to observational errors

These days, we have some very precise ways of making measurements, but I'm sure it wasn't so in Kepler's day. So I am wondering how astronomers of that time could make such accurate determinations of ...
2
votes
1answer
39 views

Invisible in visible light but visible in non-visible light?

This may be a stupid question, but I've been wondering this for a while and haven't yet found a solid answer. I'm worried the answer will be something along the lines of "of course not, you dummy" but ...
1
vote
1answer
43 views

Can the next possible ice age be projected based upon the Milankovitch cycle?

The Milankovitch cycle describes the collective effects of changes in the Earth's movements upon its climate[.] By this theory, the Earth is now experiencing an interglacial. By the theory, ...
8
votes
1answer
205 views

How many galaxies disappear beyond the Hubble Bubble horizon every year now?

The accelerating expansion of space means that the space between us and far away galaxies expands faster than light can travel through space. There is a horizon of possible observation beyond which ...
1
vote
1answer
40 views

Naive star filter visible at night in certain country

I have a HYG catalogue and I'd like to filter out stars visible at night and in Europe. Doesn't have to be exact. I was assuming that it'll be all stars with positive declination, but I wasn't sure ...
8
votes
2answers
213 views

Are there a lot of collisions between stars in the core of the galaxy?

I'm reading on Wikipedia about Halo Stars that orbit the center of the galaxy at a high inclination away from the plane of the Milky Way. It seems that at some point, these stars must dive back into ...
2
votes
1answer
35 views

Are astronomers continuously monitoring exoplanetary systems?

I'm reading many of the Wikipedia pages about exoplanets and the different methods they are using to detect them. But I wonder, it seems that the emphasis is on detecting and finding new exoplanets, ...
6
votes
1answer
211 views

Are there large underground caverns on Mars?

Scientists talk about the possibility of life underground on Mars, and I assume they are talking about microscopic life that can live in small gaps in the soil or rock. But is there any evidence that ...
2
votes
2answers
82 views

Schmidt-Cassegrain telescope

What is a Schmidt-Cassegrain (SC) telescope? We have Newtonian telescopes and also Galilean ones. How is SC telescope different from other optical telescopes? What is its construction detail and ...
1
vote
1answer
76 views

CCD in telescopes: Observation and Astro-photography

This is a Celestron CPC 800 XLT telescope. It doesn't seem to have charge-coupled device (CCD) attached. Can a CCD be attached separately to this 8" Schmidt-Cassegrain telescope even if it didn't come ...
3
votes
2answers
182 views

Help in determining the features of an unusual, fictional star system

(Hope this is the right Stack-exchange site for this question) I'm working on a sci-fi RPG campaign, set on a very atypical location. Since this is a work of fiction, there's enough room for ...
4
votes
2answers
54 views

What are the objects that are visible from a city?

I live in a light polluted city of the northern hemisphere and I would like to know what I can see with my Skywatcher BK 707AZ2. I have already seen Jupiter (and its moons), Saturn, Mars, M45, the ...
2
votes
2answers
123 views

Does mass create space?

Imagine two cubes each with the side 1 light year. One of the cubes is empty of any matter. The other cube contains a massive star. Does the cube which contains the massive star have a larger volume ...

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