5
votes
2answers
54 views

What known comets are binary?

Many asteroids are today known to be binary, to have "moons". But what comets are known to be binary? Or what fraction of them are theoretically thought to be binary? And if possible, then separate ...
6
votes
3answers
485 views

How does a gravity slingshot actually work?

From what I know of elliptical orbits, an object speeds up near the periapsis and slows down at the apoapsis, much like we learned in high school physics how a sphere would roll down and back up a ...
5
votes
1answer
310 views

Can the asteroid belt be seen from Jupiter?

Suppose that someone lives in the neighborhood of Jupiter. He may live in a space station around Jupiter, or in any ot it's moons (I believe that it doesn't matter for this question). If this person ...
2
votes
1answer
79 views

What's an order-of-magnitude main sequence star look like?

I'm looking for a very rough, order-of-magnitude approach to the main sequence. What I mean is, I have a spherically-symmetric hydrogen distribution. I'm looking to get a rough approximation for ...
2
votes
1answer
29 views

What are possible methods of discerning a starburst AGN composite galaxy?

I'm currently working on an independent project that involves discerning starburst galaxies that are themselves within active galaxies. I would assume radio observations would be best to discern star ...
2
votes
2answers
37 views

Can solar luminosity & activity be predicted?

Can a star's luminosity and its activity, solar flares and sunspots, be predicted? If so, with what accuracy & precision?
2
votes
1answer
85 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
65 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
2answers
33 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
82 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
136 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
61 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
23 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
147 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
29 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
98 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
946 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
61 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
162 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
145 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
1answer
35 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
57 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
91 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
65 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
113 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
1answer
55 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
53 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
458 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
47 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
48 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
95 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
150 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
56 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
72 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
137 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
723 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
76 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
108 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
926 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
177 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
68 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
197 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
59 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
45 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
93 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
180 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 ...

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