0
votes
1answer
12 views

Why isn't the star that created the black hole a black hole?

If the mass of a black hole is creating so much gravity that light cannot escape, why isn't the mass of the star that created the black hole (before it went supernova) trapping light as well? By all ...
0
votes
1answer
7 views

How can light reach us from 14 billion light years away?

One thing that I can't quite wrap my head around is how light is traveling to Earth from 14 billion light years away, aka the beginning of the universe. The way I see it, the universe itself was very ...
0
votes
0answers
18 views

Isn't the expanding universe a violation of conservation of mass-energy?

Correct me if I'm wrong here. I have been told that the universe is expanding faster than the speed of light, but still, Einstein was not wrong about his claim that nothing can move faster than the ...
0
votes
0answers
9 views

Free neutrons and stellar nucleosynthesis

Both the R-process and the S-process of stellar nucleosynthesis rely on absorbing 1 (S) or more (R) neutrons. Where do they come from? I thought there are no free neutrons in stars. (Also the ...
3
votes
0answers
10 views

Why are (Type II) supernovae so bright?

The vast majority of energy from a supernova is emitted as neutrinos and high-energy radiation, both of which being invisible to the naked eye. Yet a supernova can outshine its galaxy in the visible ...
1
vote
2answers
29 views

Is there enough hydrogen left after a star dies so another star will have enough to light up?

A star consumes quite a lot of hydrogen in its life, and is pretty much "vacuuming" everything in its vicinity. After it dies (eventually by supernova which will spread all its composition over light ...
2
votes
2answers
38 views

How fast is a comet moving when it crosses Earth's orbit?

Is it about the same as Earth's orbital speed?
2
votes
3answers
44 views

Did cosmological inflation occur at speeds greater than $c$?

If cosmological inflation occurred at speeds less than $c$, wouldn't we see the CMB right in front of our noses (or not at all) instead of at 13.7 billion light years? And if it happened faster than ...
1
vote
1answer
34 views

Expansion of the Universe

Please forgive my ignorance. I dare say that these questions arise from me trying to understand the nature of the Universe using Newtonian physics. There are a few things that really bother me when ...
1
vote
0answers
29 views

What are the biggest problems about the numerical, finite-element GR models?

As I know, for example the modelling of the collapse of a neutron star (to a black hole) wasn't done correctly until now. Why? Yes, I know, the Einstein Field Equations aren't really easy to solve. ...
2
votes
0answers
32 views

Which kind of properties can we get for cosmic ray particles hitting on an optical ccd?

It is very common that we meet cosmic ray particles in optical images recorded by CCDs. You can see the "snowflakes" in the hubble images below: Generally we should remove them in order to get ...
2
votes
1answer
48 views

How massive can a star be at birth?

We have discovered some incredibly massive stars. R136a1, the most massive known star is estimated to have 265 times mass as our Sun. Yet it has been burning for at least a million years, and must ...
3
votes
1answer
24 views

Tools for creating a multiwavelength view of the sky

Not sure that this is the correct place to ask this question, but here goes. I am trying to find tools to accumulate image data (preferably in FITS format) on a given (RA, Dec)-coordinate of sky. ...
2
votes
1answer
22 views

Conditions on Hot Jupiters

Hot Jupiters are close to their parent star - after all, that's why they're so hot. Their atmospheres are thought to be slowly blown away by the parent star, and they will eventually become chthonian ...
2
votes
0answers
35 views

What is the difference between Sphere of Influence and Hill sphere?

Wikipedia's definition of Hill sphere is: An astronomical body's Hill sphere is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit ...
3
votes
2answers
89 views

Selecting a Telescope for Viewing Planets

I hope to observe planets like Jupiter and Saturn, and moons. I am a novice when it comes to telescopes and I know images in magazines are not taken with at least 12-inch telescope in a middle of ...
2
votes
0answers
45 views

Milky way: How do we know its appearance?

How can we know how does the Milky Way look like if we are in it? Sorry if the answer is evident, I am not an expert.
5
votes
3answers
48 views

Can you explain the pattern of Hill sphere sizes of the objects of the Solar system?

I found this image on calculations of Hill sphere for planets/dwarf planets of the Solar system. From http://en.wikipedia.org/wiki/File:Hill_sphere_of_the_planets.png I found it interesting that ...
1
vote
1answer
34 views

Is a spotting scope or binoculars a better choice for astronomy?

I'm interested in observing the moon and planets, and maybe some nebulae and star clusters. I have a pair of binoculars: Nikon OceanPro 7x50 binoculars (around \$300) Celestron 20x80 binoculars ...
3
votes
0answers
22 views

Equinoxes and solstices: start of the season or mid-season? [migrated]

In the United States, the upcoming autumnal equinox is marked on most calendars as the "first day of autumn." Similarly the solstices are commonly called the "first day of summer" and "first day of ...
0
votes
1answer
42 views

Time-density and time-temperature functions of the Universe since the Big Bang

I am looking for these... functions. I want to be able to say, "at a 1873. second there were around 54230000000 K temperature and 0.00435 kg/m^3 density". On the net I could find only tables or ...
2
votes
1answer
30 views

Is there an astronomy exam I can take?

I am currently living in Bangkok and I love astronomy. However, I haven't been able to find an official astronomy exam that I can do to gain college credit. Could someone help me out please?
1
vote
3answers
64 views

the metal distribution in our solar system

The sun dominates in our solar system. I wonder whether in every aspect the sun play the most role in our system. For example, all kinds of metals are mainly located in the sun instead of the rest ...
3
votes
1answer
42 views

How many astronomers are there in the world today?

How many now living individuals have a PhD in astrophysics, or by some other definition can be reasonably classified as astronomers? I think Richard Feynman once said that only one in a million is an ...
1
vote
1answer
10 views

How do I find the RA of sunset and sunrise in a specific location?

I want to make some observations with a telescope in Hawaii on Mauna Kea but I am living somewhere else (not Hawaii) and I want to plan a night's viewing on the Hawaiian telescope. How do I find the ...
2
votes
1answer
27 views

Assuming a sufficient amount of mass above the density threshold, does the actual concentration of the mass matter in creating a black hole?

I've heard that the actual density of a black hole (within the volume of the event horizon) is pretty low - does that mean that any sufficiently large volume of mass over that density is also a black ...
8
votes
1answer
78 views

If we count Avogadro's Number of stars that are closest to Earth, how big that space would be?

I posted this as a question to Scientific Imagination (Area 51 proposal) a while ago. And it was suggested that this question "is perfectly acceptable on Astronomy SE", since "it's about stellar ...
1
vote
0answers
18 views

Sedna, VP113 and the likelihood of the PX/Tyche/Thelistos hypotheses

Crosslisted question from http://physics.stackexchange.com/questions/131876/sedna-vp113-and-the-likelihood-of-the-px-tyche-thelistos-hypotheses The recent discoveries in exoplanetary science ...
1
vote
2answers
50 views

Why does the Moon sometimes look Yellow?

My friend and I both noticed that the Moon looked yellow Yesterday, but it wasn't like that the same time the day before, as far as I remember. Does the Moon sometimes look Yellow? If it does, why ...
2
votes
1answer
37 views

If the speed at which the universe contracts in reverse time decreases over time, then how did scientists arrive at a date for “The Big Bang”?

If the speed at which the universe expands is constantly increasing (just like a derivative), then the opposite must also be true: the speed at which the universe contracts in reverse time is ...
1
vote
0answers
28 views

Are there sufficient observational data to measure non-Newtonian perihelion advances of any Asteroid and Comet orbits?

Anomalous (i.e. not predicted from Newtonian theory) advances of the perihelion direction have been observed for many solar system planet orbits and have been accounted for by Einstein's General ...
1
vote
2answers
69 views

any unique phenomenon when the cores of two planets are aligned with their star's core?

Imagine a line passing through the cores of two planets (in the same planetary system) and their star. Have we ever witnessed this - either with both planets on the same side of the star or on ...
1
vote
0answers
20 views

Long term effect on rocks of high pressure and temperature?

The mean surface temperature of Venus is about 460 C and the pressure is about 92 atmospheres. Assuming this situation (or similar) has prevailed for millions of years what changes (if any) would ...
0
votes
1answer
24 views

Adaptive Optics?

I get the general idea of adaptive optics. The light from an object distorted by differences in the earth's atmosphere, and a telescope with AO tries to compensate for this distortion by various ...
4
votes
1answer
89 views

Is it possible that a ultra-large portion of the space we live in is already inside a black hole? How could we refute this?

Trying to wrap my head around some concepts involving the very large gravitational fields of black holes, and what the gravitational gradients look like on a cosmic scale. I'm familiar with the Great ...
1
vote
1answer
35 views

what is the metal distribution in our universe

Most of the metals are located in ISM,IGM, or stars? Maybe different metals have different distributions? For one kind of metal element, what is its distribution? Let's classify the metals according ...
5
votes
1answer
49 views

Objects entering or leaving the observable universe

Have there been any observations of objects entering or leaving the observable universe? When looking at the physical limit of observing something like this I will to assume that the "object" would ...
2
votes
1answer
58 views

Is there a term for stars without any planets?

Quite simply, is there any used term for stars that don't have any planets? While contemplating this and doing numerous searches to no avail, I think I found my own answer, but I'm asking here for ...
4
votes
1answer
90 views

What can a lunar-based telescope do?

What can a lunar-based telescope do? If the band is ultraviolet and it can do high time sampling exposure, maybe it can be used to get distance for a star with stable pulses. However, the star should ...
2
votes
4answers
89 views

Milky Way Formation

Is the Milky Way a collection of merged galaxies, or has it only been one galaxy that was created from the interstellar media?
4
votes
1answer
72 views

When will the Milky Way “arrive” at the Great Attractor, and what all happen then?

The Great Attractor is described as a location to towards which the Milky Way, along with all other galaxies in the Laniakea Supercluster are moving. How long will it take for the Milky Way to ...
1
vote
1answer
24 views

What is the radius of observable universe- 46 billion LY or 200 yottameters?

I have found two answers for the radius of the observable universe. Wikipedia (and other places, including this site) say approximately 46 billion LY. I am researching this to study for the National ...
2
votes
1answer
49 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.
4
votes
1answer
141 views

Is there a 'South Star'?

The star Polaris is commonly known as the Northern Star because it always points North. This being said is there a South star that always points south?
6
votes
2answers
182 views

Why does the Moon never set in Svalbard, Norway?

I heard in a documentary that, in Svalbard (Spitsberg), Norwegian archipelago in the Arctic Ocean, the Moon never sets. Why? A drawing would certainly help.
4
votes
2answers
113 views

How was the Earth-Sun distance originally calculated?

AFAIK it was possible long before the first interplanetary probes. Who did it?
3
votes
1answer
21 views

Save current state in ds9?

After fooling around with a FITS file(s) (e.g. setting scale, changing color) is it possible to save the session such that there is a file associated with all those tweaks the next time I open it up? ...
2
votes
2answers
33 views

Why is sodium such a common ion for in ion tails?

I was doing research about ion tails of planetary bodies and noticed that ion tails composed of sodium were common. For example, Mercury and the Moon both have ion tails made of sodium. Why is sodium, ...
1
vote
1answer
18 views

During what time of the year can Centaurus be seen from Tokyo?

During exactly what dates of the year can the Centaurus constellation be seen from Tokyo, Japan? And what is the ideal date for viewing it from Tokyo? I found on a website that it can been seen ...
1
vote
2answers
42 views

Birthdate differences calculation relative to earths orbit duration

I have got a question as i am trying to figure out what the real difference between the birthdate of my friend and me is. I am born on 1983 6th February 7 am. My Friend is born on 1984 7th February 1 ...

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