All Questions

2
votes
1answer
65 views

Are ascending node of sun, the point of intersection of prime meridian and equator and center of earth all collinear?

I did a bit of googling but couldn't find the exact answer, so are the following 3 points collinear or not ? 1_center of earth 2_ascending(or descending) node of sun 3_point of intersection of ...
2
votes
1answer
46 views

Does near light-speed travel doppler-shift the light from the target into gamma rays?

If a space ship travels at near the speed of light towards a star, wouldn't the light from the star doppler shift into gamma rays (or worse?) and become lethal to life and destructive to space ship ...
1
vote
0answers
25 views

What is frequency range?

Using the NED, you can search via frequency range corresponding to the selected pass band filter. I'm a beginner here and don't really understand. Here's the quote: NOTES: Objects with ...
1
vote
3answers
79 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 ...
3
votes
1answer
57 views

Classification of a Comet

Google's definition of a comet is: a celestial object consisting of a nucleus of ice and dust and, when near the sun, a ‘tail’ of gas and dust particles pointing away from the sun. This ...
2
votes
1answer
54 views

What is the time/size/rigidity ratio for a space object to become mostly round?

In the answer here multiple comets are identified that do not form a single round body. A drop of water will form a round shape in the time it takes to free fall a couple of feet. All of the ...
2
votes
1answer
21 views

Do planetary radio frequency change upon alignments?

If Neptune would align Uranus, would the radio frequency perceived on Earth increase? Are the radio antennas on NM capable of getting the 2 different radio frequencies feom both planets or would they ...
2
votes
2answers
87 views

Is it possible to move a planet out of its orbit? At least a lighter planet?

As observed by many researches our sun will be exhausted in a distant future. So anyone thinks driving our planet (or any planet) closer to the sun for more light and heat is a solution for the life ...
1
vote
1answer
24 views

Can Summer Triangle asterism be used for navigation?

I am wondering, whether is it possible to use vega-altair-deneb asterism for navigational purpose? Or if there is any geometric relationship of it with Polaris? Any idea. Thanks
7
votes
2answers
97 views

How were the designations of “North” and “South” applied to the hemispheres of Mars?

How was it decided which hemisphere was North and which hemisphere was South on Mars? Clearly, the designations "North" and "South" apply only to the hemispheres which contain the axis of rotation at ...
7
votes
2answers
933 views

Can two comets travel together as one?

If two comets come together in space, will they bounce apart, merge into a single body, or could they travel together through space, either touching or orbiting a shared center of gravity?
1
vote
2answers
55 views

The RA and Dec of lunar poles

The moon faces the earth with one fixed side. However there is a small vibration. So I am not sure the south and north poles of the moon is fixed. Even if they are fixed points on the moon, the pole ...
2
votes
1answer
17 views

How to compare a Catadioptrics light asorbtion with a reflector?

I used to have a 6" Dobsonian reflector, and the next telescope I buy, I want it to have the equivlant of about a 11/12" dobsonian reflector. I'm looking at this Nexstar VX 9.25 , it says 235mm ...
2
votes
0answers
118 views

is there any theory or observational evidence that our universe is electrically neutral or not?

It seems our universe is neutral in large scale. There is CP violationwiki problem about matter and dark matter. Similarly is there any theory about whether our universe is electrically neutral? ...
8
votes
2answers
128 views

Is there any point on earth where the moon stays below the horizon for an extended period of time?

When I was teaching a class why the earth has seasons today, I mentioned how the poles of the earth experience months of daylight and darkness. Then one of my students asked whether the moon ...
1
vote
0answers
27 views

Alt-Az or Polar?

I have a Meade wedge that I am to install on one of their LX200 telescopes. Will I be able to align in alt-az afterwards? Is polar easier or harder to make an alignment? Any other tips welcome. Thanks ...
3
votes
1answer
54 views

Can astronomical radio sources be used as a verifiable randomness beacon?

A randomness beacon is a source of random data that is broadcast to multiple parties. Users listening to the beacon receive the same sequence of random strings and no one can predict the values in ...
1
vote
1answer
63 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 ...
2
votes
1answer
57 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 ...
1
vote
1answer
74 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) - ...
1
vote
0answers
27 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
48 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 ...
10
votes
3answers
402 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
38 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
46 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
82 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 ...
2
votes
2answers
126 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
49 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 ...
4
votes
1answer
69 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
117 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 ...
10
votes
2answers
694 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
36 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 ...
1
vote
0answers
35 views

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

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 ...
2
votes
0answers
65 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
497 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
33 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
101 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
18 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
47 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
192 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
41 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
41 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
85 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
163 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
43 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
121 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
36 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?
4
votes
1answer
66 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
69 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
200 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 ...

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