All Questions

1
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1answer
49 views

Expansion of the Universe [duplicate]

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 ...
2
votes
4answers
127 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?
2
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0answers
37 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 ...
4
votes
2answers
129 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 ...
10
votes
1answer
1k views

How can I collimate a dobsonian telescope with a laser collimator?

I've had a dobsonian telescope for a while now, but I've never been able to collimate it. I thought I had it collimated once, but when I looked through it the star didn't look right, it looked kind ...
2
votes
1answer
23 views

Collimator for Dobsonian, same as Newtonian?

I have been looking on line for Collimator for my Meade Dobsonian. The only Collimators I can find are made for Newtonian Lenses. It's a 8" mirror with a 1.25" lens. Will this work for my telescope?
3
votes
1answer
94 views

What is the farthest object we've been able to bounce signals off of to date?

I know people bounced lasers off of Venus and Mercury in 1960s in order to test the Shapiro delay. Since then, we've developed higher power lasers and radio transmitters (Bolshakovo transmitter). ...
1
vote
0answers
35 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. ...
1
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3answers
72 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 ...
1
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2answers
125 views

How to calculate right ascension of Greenwich? [closed]

If I know specific time, t0, how can I calculate RA of Greenwich?
1
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1answer
58 views

Distance of extra-galactic Classical Cepheids

There have been many questions and answers about finding the distance of a star from the earth. But as I did some research on the net, I found that we have specific approaches for finding the ...
4
votes
2answers
133 views

How was the Earth-Sun distance originally calculated?

AFAIK it was possible long before the first interplanetary probes. Who did it?
2
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1answer
57 views

How massive can a star be at birth? [duplicate]

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 ...
4
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2answers
185 views

Are there stars that don't emit visible light?

Are there stars that do not emit any light in the visible part of the EM spectrum?
8
votes
1answer
288 views

Determining effect of small variable force on planetary perihelion precession

Is there an analytical technique for determining the effect of a small variable transverse acceleration upon the rate of aspides precession (strictly not a precession but rotation of the line of ...
3
votes
1answer
26 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
26 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 ...
9
votes
2answers
174 views

How are Galaxy Super Clusters Generated

I have seen pictures of clusters of galaxies, usually used in regards to theories of dark matter and galaxy formations. One of the most famous ones has the perceived shape of a stick-figure. If I am ...
5
votes
1answer
65 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 ...
6
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4answers
151 views

The Existence of Natural Satellites in Geostationary Orbits

While browsing through Physics SE, I noticed a question about satellites in geostationary orbit (unrelated to the one I'm asking here), and for a moment I interpreted it as referring to natural ...
1
vote
1answer
45 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
1answer
26 views

meaning of p-wave charmonia

What exactly does p-wave mean when referring to particles, like charmonia states. For example, see the following reference: http://arxiv.org/abs/hep-ph/9208254 My doubt is - p wave in scattering ...
2
votes
1answer
32 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
2answers
79 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
2answers
55 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 ...
1
vote
1answer
65 views

Mechanism for Brown Dwarf Fusion

I've read (at here, among other places: http://deepblue.lib.umich.edu/bitstream/handle/2027.42/55288/index.html?sequence=1) that during the Degenerate Era, star formation will end and the last stars ...
9
votes
7answers
649 views

What's the largest non-spherical astronomical object in the universe?

Some asteroids and comets are non-spherical. But is the nature of big things and gravity so that large things in the universe are always spherical? What is the biggest astronomical object in terms of ...
3
votes
1answer
77 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 ...
6
votes
2answers
225 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.
2
votes
1answer
42 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 ...
4
votes
3answers
203 views

What's the likelihood of the existence of unknown elements in the Solar System?

What's the chance that there might be undiscovered chemical elements in the Solar System - either on planets or around the Sun or on asteroids of the Oort-cloud?
5
votes
2answers
267 views

Our universe the surface of a 4-dimensional sphere?

The cosmic microwave background that we observe uniformly around us is usually explained by assuming that our universe is the surface of a four dimensional sphere. That way the uniformity makes sense ...
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? ...
1
vote
0answers
34 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
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0answers
30 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 ...
0
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1answer
25 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 ...
1
vote
1answer
58 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 ...
2
votes
1answer
65 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
95 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 ...
3
votes
1answer
51 views

Potential Re-Capture of Rogue Planets

Rogue planets can be designated as rogue planets due to one of two possible scenarios: 1) the "rogue planet" formed as a sub-brown dwarf, or 2) the planet was ejected from its home star system. I want ...
4
votes
1answer
149 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?
4
votes
1answer
99 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 ...
3
votes
1answer
53 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.
1
vote
1answer
25 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 ...
1
vote
2answers
132 views

Contradict the expansion of the universe?

Lets say that we observe in a distant galaxy cluster, which in all the galaxies move far away from us. and here we see in the same cluster a galaxy that move away from us in a much lower velocity ...
1
vote
1answer
24 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 ...
3
votes
1answer
22 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
34 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, ...
7
votes
2answers
141 views

Is the Hubble Ultra-Deep Field image representative of the entire sky?

The Hubble ultra-deep field image is a photograph of an area of sky equivalent to a 1mm x 1mm piece of paper held a metre away from the eye (one thirteen millionth of the entire sky). It contains an ...
0
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3answers
45 views

Could the universe have evolved differently?

Given the initial conditions at the Big Bang, could our universe have evolved any differently? In other words, did the initial conditions predetermine every stage in the evolution of the universe to ...

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