All Questions

3
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1answer
63 views

Formation of stars

How are stars formed? I read somewhere that when dust, gas, rocks etc come close to each other due to gravity, slowly and gradually build up a lot of pressure and form stars. If what I read is ...
3
votes
1answer
71 views

Dark Energy Expansion

The new Cosmos extra features mentions that at about 6,771,500,000 years ago the universe began an accelerated expansion. How do we know this? What evidence do we have for this renewed and accelerated ...
3
votes
1answer
279 views

Average amount of annual daylight at any place on earth

If this is the wrong group please direct me to the correct one. It seems intuitively obvious that the amount of daylight per annum should be the same for any latitude on earth. For example, 12 hours ...
3
votes
1answer
81 views

What is the optimal escape trajectory from near a black hole?

Consider a space ship that is being drawn closer to a black hole. The crew begins to notice the effects, and discovers that they are nearing the black hole. They then manage to halt their ...
3
votes
2answers
37 views

How does solar activity (e.g. flares, coronal mass ejections) change over the life cycle of a Sun-like star?

As a Sun-like star is born from a collapsed nebula and generates energy by nuclear fusion some of that energy is converted to magnetic fields which fuel solar activity. How does that activity evolve ...
3
votes
1answer
84 views

Motion of the sun as observed from mercury

I recently found this animation which shows the motion of sun as observed from mercury. It seems as if the sun stops in between, retraces a bit and then continues towards the west. What is the reason ...
3
votes
1answer
92 views

What determines which frequency range a radio telescope has?

My simple understanding is that a parabolic dish focuses radio waves to a receiver. It is obvious that any parabola focuses visible light and heat, so I assume that it focuses all radio wavelengths ...
3
votes
2answers
147 views

What mechanism causes oscillations of the solar system's orbit about the galactic plane?

In a recent paper (news release here) Lisa Randall and Matthew Reece propose that a dark matter disk coinciding with the galactic plane together with the solar system's oscillations through the ...
3
votes
2answers
92 views

Apogalacticon and Perigalacticon

What is the length of the apogalacticon and perigalacticon of the Sun and Milky Way? The general terms seem to be apoapsis and periapsis. My greatest efforts at Googling have failed miserably. If ...
3
votes
1answer
285 views

How can I calculate the orbital periods in a binary star system?

I have two stars, with known masses and known orbital radius. How do I calculate the orbital periods of both stars?
3
votes
1answer
61 views

How many earth-like planets do we know at this moment?

Well, the title says everything... How many earth-like planets have we discovered out there? Discard too big (made of gas), too cold, too hot, etc. Consider earth-like sun distance, size, temperature, ...
3
votes
1answer
98 views

What's the estimated remaining life of Halley's Comet?

I know that Halley's comet is seen from Earth every 76 years or so since a couple centuries. As it travels, and particularly when it comes near the sun, it loses some of its material (ice). Someday, ...
3
votes
1answer
78 views

Can orbital migration cause a planet to crash into the sun?

If the planets move out of their current orbits into other orbits over long periods of time could this cause a planet to crash into the sun? Maybe the term crash is a little dramatic, could the orbit ...
3
votes
1answer
72 views

Motion of rogue planets

Two Questions: 1) Are rogue planets in motion, i.e. are they just wandering freely in space or stationary? 1) Do rogue planets have defined path or a one which can be anticipated? I understand that ...
3
votes
1answer
85 views

Recommended papers

I am highly interested in how the moon originated. Theories suggest that the moon is a chunk of the earth, or rather, both were at one point one celestial body. Is there any literature out there with ...
3
votes
2answers
74 views

Does gravity propagate?

Gravity is sometimes described as a curvature in space-time. Due to relativity, doesn't this imply that gravity doesn't propagate? A thought experiment. If you are moving toward a black hole, this ...
3
votes
1answer
87 views

Internet Resource which register all Ultra-long Gamma-Ray Bursts

I read in a scientific magazine there was new gamma bursts that last longer than usual. One was detected during december 2010, also known as Christmas Burst: GRB 101225A and another one in 9th of ...
3
votes
2answers
805 views

How to calculate Longitude from Right Ascension?

Considering that a star of certain declination is crossing the local meridian at the observer's zenith at an unknown location on the earth. Here, the declination of the star is equal to the observer's ...
3
votes
1answer
254 views

Periodic error correction in automatic telescopes

I am starting a study on automatic telescopes and the correction of their periodic error. I found two ways of correcting it : with a CCD camera and manually by recording the error. I was wondering if ...
3
votes
1answer
121 views

Which galaxy is receding from the Milky the fastest? What is known of the mechanism behind its recession?

Galaxies are always in motion relative to the Milky Way, my question is, which galaxy is receding the fastest from our viewpoint? What is the theorised mechanism that causes this?
3
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1answer
92 views

Evidence behind Giant Impact hypthesis

The giant impact hypothesis is a theory to explain how the moon was formed. What evidence is there that supports the theory and led us to find the current theory?
3
votes
1answer
58 views

Hypothetical scenario, two nearby black holes

I've always wondered what would happen if a hypothetical scenario, two black holes meet, with similar proportions: Maybe one swallow the other one? Or would make a bigger one between them.
3
votes
1answer
46 views

How did the Hulse-Taylor Pulsar Provide Confirming Evidence of General Relativity?

What measurements and observations of the Hulse-Taylor Pulsar agreed precisely with the predictions of general relativity, and how did these measurements support the theory?
3
votes
1answer
71 views

How did the reionization epoch make the universe “transparent”?

I've been reading about the reionization epoch of the universe, and it isn't entirely clear to me. As I understand it, very shortly after the big bang the universe was ionized, with the electrons ...
3
votes
1answer
113 views

Compute Planet's Apparent Visual Magnitude

In a hypothetical solar system there exist: a sun of radius $r_s$ and absolute visual magnitude $V$ the Earth, with radius $r_e$ and distance from the sun of $1\,AU$ another planet, wit radius ...
3
votes
1answer
80 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 ...
3
votes
1answer
80 views

Is the expansion accelerating or Decelerating?

According to Hubble's Law, the farther a galaxy is, the farther it is moving away. But do we take into account the fact that we are actually looking in the past? For example, there are two galaxies A ...
3
votes
1answer
60 views

Does Tobler's First Law of Geography Apply to Star Composition?

There is a principle in Geography called Tobler's First Law of Geography which states that "Everything is related to everything else, but near things are more related than distant things." Does this ...
3
votes
1answer
33 views

Instrument aperture sizes on Hubble Telescope

When looking at the diagram of the focal plane of the Hubble Space Telescope I noticed that the aperture sizes of most of the scientific instruments are very small. They occupy a very tiny fraction of ...
3
votes
2answers
72 views

Where can I find a set of data of the initial conditions of our solar system?

As title suggests I'm in need of a set of data of our solar system. Similar to this http://bima.astro.umd.edu/nemo/archive/#iau25, specifically dubinsky milky way-andromeda data. I'm creating a ...
3
votes
1answer
111 views

Could an asteroid impact cause radioactive fallout?

Could a (regional or global) fallout of radioactive material be a "bonus" disaster effect of an asteroid impact? My reasoning for how such a scenario maybe could be possible: A) Some asteroids maybe ...
3
votes
2answers
82 views

Why is Mars considered the outer edge of the “goldilocks zone”?

In both books and documentaries I often see the Goldilocks Zone as described between Venus and Mars with the Earth "just right." This seems sort of ill thought out to me, because it assumes that ...
3
votes
2answers
96 views

Questions about time and space (from beginner)

To be honest my knowledge about astronomy and related physics is close to zero. However, since I studied math a bit, I would like to ask a couple maybe stupid questions, which I am curious about and I ...
3
votes
1answer
106 views

Which type of telescope should I make?

I am not very much interested in observational physics but I just like to look at the night sky. It gives me a lot of inspiration. So, i was thinking about making a telescope for basic observations. I ...
3
votes
1answer
67 views

What’s the object between the earth and the sun currently showing in Google maps?

If I select satellite imagery in Google maps and zoom out, the earth is shown in space. It shows light/dark regions correctly updated, but there’s an object between the earth and the sun. It looks too ...
3
votes
1answer
51 views

Sattelite's orbit

What is the maximum distance for a satellite to orbit the earth? Does earth's gravity has the impact on satellite? I do know that earth's gravity will never be zero and it's gravity is inversely ...
3
votes
1answer
287 views

How to get the longitude/latitude from solar zenith/azimuth?

How do I get the longitude/latitude from zenith/azimuth? Or how can I position my sun in a 3d application? code extracted from here ...
3
votes
3answers
282 views

Spotting the International Space Station (ISS)

Recently, I visited the NASA website which provides sighting locations to see the International Space Station (ISS). As we all know, we can even see ISS with the naked eye in a clear sky as a passing ...
3
votes
1answer
47 views

What happens to the shrinking universe in the presence of the pressure of Hawking radiation?

Black holes release Hawking radiation. Now assume that the universe after all collapses back again, bringing all matter to a single black hole. I assume that this would bend the whole space-time of ...
3
votes
1answer
60 views

How is the magnitude of a star measured?

How does one measure the brightness of a star?, I did not find anything on the internet.
3
votes
3answers
141 views

Why is the outline of a crescent moon brighter?

Some quick googling has given me the answer to whether seeing part of the moon that receives no sunlight is an optical illusion or not: it isn't. Earthshine lights the moon enough for the human eye to ...
3
votes
1answer
64 views

Periodic behavior of Venus

After a couple months of watching a very bright Venus appear at dusk and set soon after the Sun, I've noticed that it seems to have temporarily disappeared to the naked eye. I used a virtual sky ...
3
votes
1answer
65 views

What does it mean for a black hole to “evaporate”?

It says in this Wikipedia's article: Entropy, however, implies heat and therefore temperature. The loss of energy also suggests that black holes do not last forever, but rather "evaporate" slowly. ...
3
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1answer
79 views

Coordinate transformations between reference frames in spherical astronomy

Suppose there are two observational frames of reference with origins $O$ and $O'$, respectively, separated by some constant distance. A body located at point $P$ has Cartesian coordinates ...
3
votes
3answers
94 views

Without using absolute magnitudes or isochrones, how might we tell a star's age and evolutionary status?

Usual methods of estimating stellar ages involve isochrone approximations. It can also help to estimate a star's radius by correlating its absolute magnitude with effective temperature and apparent ...
3
votes
1answer
157 views

How does a Bahtinov mask work?

For focusing the image of a telescope, one can use a Bahtinov mask. How does this mask work, and how did Mr Bahtinov get the idea to cut such a peculiar shape? Is it possible for me to design my own ...
3
votes
1answer
49 views

Hulse-Taylor binary pulsar - what is the rate of mass/energy loss from the source?

Following on from an earlier question about the very interesting Hulse-Taylor binary pulsar. The high-frequency (radio) beam from the spinning pulsar sweeps across Earth about 17 times per second. ...
3
votes
1answer
34 views

What is the degree of ionization is the solar photosphere?

I am wondering how many free electrons per baryon and how many free electrons per atom there are in the solar photosphere. This number depends on the abundances of the various atoms found in the ...
3
votes
1answer
68 views

How bright are the outer planets, when at close range?

Seven probes have passed by or orbited outer planets. I wonder how their photos differ from the naked eye view one would have if one were actually there. Saturn is 10 AU from the Sun, which means ...
3
votes
1answer
79 views

Is early life required for life?

I was watching the new Cosmos and Neil DeGrasse Tyson said something that made me go hmmm... He mentioned that the only reason that the Earth did not experience the runaway greenhouse effect like ...

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