1
vote
0answers
9 views

Time after sunset until star can be seen

Given a star's apparent location and apparent magnitude, how how many degrees below the horizon must the sun be for the star to be visible to the naked eye for an observer on Earth at a specified ...
2
votes
0answers
12 views

Is there a paper on galaxy mergers in clusters of galaxies?

I'm looking for something to cite about galaxy mergers in clusters of galaxies. I need numbers on the frequency of mergers in the outer parts of galaxy clusters vs. the cluster center. In the center ...
1
vote
1answer
34 views

How many light years away is Earth from the closest outer edge of the black hole at the center of the Milky Way?

How many light years is Earth away from the closest outer edge of the supermassive black hole in Sagittarius A* at the center of the Milky Way? I don't mean the distance to the center of the galaxy, ...
1
vote
1answer
28 views

Which spiral arm of the Milky Way is Kepler-62 in?

I am trying to find out which spiral arm of the Milky Way the star Kepler-62 and its planetary system are in. All I can find by Google searching is that it is part of the Lyra constellation, but I ...
1
vote
1answer
31 views

Star System Formation questions

I'm making a game in which I'd like to randomly generate star systems. Which is cool. The trouble I'm having is working out exactly what limits I need to place on the generation. So far, the ...
1
vote
1answer
58 views

How do black holes evaporate?

Will black holes evaporate, if they evaporate? When and why do they evaporate? What are the conditions for evaporation? Under what principle do they evaporate?
4
votes
1answer
47 views

Can we see the Big Bang happen if we look far enough?

The observable universe is constantly expanding as more light from the Big Bang reaches us. This light has been travelling for billions of years, so we are looking at the universe as it was a few ...
5
votes
3answers
62 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 ...
3
votes
0answers
15 views

Can the Gaia telescope detect small temporarily captured asteroids near its Lagrange orbit?

The Gaia space telescope is in a Lissajous orbit around the Sun-Earth Lagrange point 2. The orbit period is about 180 days and the size of the orbit is 263,000 x 707,000 x 370,000 km. It has been ...
9
votes
3answers
144 views

Why do (most of) the planets rotate counterclockwise, i.e. the same way the Sun does?

Referring to the mechanisms explaining the solar system formation and to the initial rotation of the gaseous cloud that collapsed, I understand easily why the planets orbit the Sun the same way this ...
4
votes
0answers
27 views

Would bagging an asteroid destroy valuable science about it?

NASA has a plan called "Asteroid Redirect Mission option A". It would robotically put an asteroid of a few meters diameter in a bag and push it into reach of astronauts for thorough examination. 44 ...
1
vote
0answers
55 views

Multiple apparent lunar eclipses last night

I saw something very strange last night that I'm hoping someone can help me explain. I was sitting on my roof with a night-cap at about 3am last night. The moon, about the last quarter, was low in the ...
2
votes
1answer
54 views

What type of energy is escaping from black-hole's poles?

Following this article, it is stated that: As a star drifts too close to a supermassive black hole, intense tidal stresses rip the star to shreds. As this happens, the shredded material will ...
-2
votes
0answers
36 views

What is the secret behind the existence of gravitational force? [closed]

Why does the gravitational force exist? What is the reason behind it? Does it exist due to mass? What do you mean by tidal frictional interaction?
1
vote
2answers
99 views

Why don't planets give off their own light? [closed]

Why don't the planets glow like stars?
2
votes
4answers
129 views

Why aren't there galaxy-sized balls of iron out there?

Since we know that stars burn out, collapse, or blow up when too many of their atoms fuse inti iron, then how come, with all the ancient galaxies we've been observing, there isn't one galaxy whose ...
3
votes
2answers
30 views

Why do some celestial bodies have atmospheres, and not others?

Question is rather self-explanatory. An answer touching upon how/why atmospheres are formed in the first place would be ideal as well. An example of such astral bodies would be The Earth and it's ...
1
vote
1answer
73 views

How was an infrared picture of the entire universe taken?

(click to enlarge) How was this picture of the supposed entire universe taken in infrared? Also, why does it seem as though almost all of the matter is in a line formation over the center? It makes ...
1
vote
1answer
36 views

the length of second, minute or hour, what defines the time of exo planetary bodies

we measure time based on earth and earth mass\gravity plays a role in the measurement ? so how and what would be time if not earth time on other exo planets since they will be having different ...
2
votes
2answers
67 views

The face of the moon at moonset

It appears that the face of the moon "rotates" clockwise from the time the moon rises to the time it sets. Tycho's crater seems more to the left and the "Rabbits head" looks like it's facing down ...
1
vote
0answers
36 views

Is Rosetta changing the theory of comets?

Rosetta is now arriving at Comet 67P. Other comets have been analyzed to some degree (Giotto, Deep Space 1, Deep Impact, etc.) So my question is... where I can study the up-to-date theory of ...
1
vote
0answers
26 views

Original Hubble diagram units incorrect?

Figure 1 from Hubble 1929 has velocity with units of km. Is this just a typo or was there a reason the plot is printed this way?
0
votes
0answers
12 views

Problem with Python [migrated]

I'm using Python 2.7.3 on my Debian server. Here is the input code: import aplpy import pyfits from numpy import * import matplotlib as plt import montage as montage_wrapper import PIL ...
0
votes
1answer
66 views

Contradiction between Theory of Relativity and Newton's Law of Universal Gravitation?

Newton's Law of Universal Gravity states that an object will accelerate constantly as it falls. Let's assume an object falling into a black hole. According to Newton's Law, when it reaches the event ...
2
votes
1answer
52 views

What is star composition after formation

Most descriptions of star ignition go something like... The star reaches a critical mass and ignites, blowing away the surrounding material. The most obvious question would be "Why are stars not all ...
1
vote
2answers
63 views

Can we conclude with reasonable certainty that there is/are no Type 3 Civilizations in our galaxy?

As per the Kardashev Scale, type-3 civilizations are defined as "civilization(s) in possession of energy on the scale of its own galaxy, with energy consumption at ~ 4 x 10^44 erg/sec". Considering ...
0
votes
1answer
45 views

Starting out in practical astronomy [closed]

I want to start observing the night sky, what advice would you give to get started?
2
votes
1answer
61 views

How is space-time bent by black holes?

I just read When a star becomes a black hole, does its gravitational power become stronger? and it confused me a bit; I always thought black holes are supermassive and that is why they bend ...
1
vote
2answers
41 views

Telescope on polluted environment

this one bothering me,to buy a telescope. I live in a city,unfortunately with dust and polluted air, is there any affect in viewing a nice capture of our galaxy? Or i need to buy a special telescope?
0
votes
2answers
67 views

Infinite universe? How? [duplicate]

So it seems the overall thought is that the universe is infinite. I don't get how. Most depictions I read mention something to the effect of "at 1^-20 seconds the universe was the size of _". ...
0
votes
0answers
10 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 ...
1
vote
1answer
17 views

Beta profile fit of Virgo cluster gas?

I'm looking for the parameters $r_c$, $\rho_0$ and $\beta$ in a $\beta$-profile fit of the Virgo cluster's ICM density. I just can't find a reference for it. Unlike for Coma (Abell 1656) where it's in ...
1
vote
1answer
45 views

Weight of a celestial body

How do astronomers find out the correct weight of a planet tough there isn't any direct means to weigh them?What technique do they use?Just curious!
2
votes
1answer
43 views

Data for red-shifting

I am looking for basic data regarding red-shifting that comes with reliable measure of distance of the emitting star.
1
vote
1answer
23 views

How to polar align an equatorial mounted telescope when you are close to the equator?

I recently moved to southern Mexico (16 degrees N) and I wonder what would be the best way to align my EQ telescope when the polar star is not visible?
1
vote
1answer
34 views

Electron Degeneracy Pressure and the Pauli Exclusion Principle

I have read that what keeps white dwarfs from gravitational collapse is electron degeneracy pressure. How does this pressure prevent further collapse, and how is it related to the Pauli Exclusion ...
1
vote
1answer
34 views

Under Earth's gravitational pull, how dense would an object have to be to reach its Schwarzschild Radius?

The Schwarzschild Radius is a theoretical radius, that if the mass of the object was compressed into that certain radius, the escape speed from the surface of the compressed object would equal the ...
6
votes
1answer
54 views

Name of area close to Local Bubble?

The following image is a map of the area surrounding the Local Bubble. One side of the image is 1700 lightyears. From the Sun to the Hyades (immediately below the sun) it is 150 lightyears. The local ...
0
votes
0answers
25 views

fit sine wave to data [migrated]

I have some astronomical data which I know has a sinusoidal component to it of the form y = Asin(Ωt+Φ). The period of the sinusoid is equal to a sidereal day. So ...
5
votes
3answers
128 views

Why do astronomers like Green Laser Pointers? [on hold]

When I've been to Astronomy-nights for the public at the local observatory, they always use green lasers to point things out. Why is there such a preference for green lasers? What's wrong with red ...
1
vote
0answers
44 views

Why are explosions always used to represent the Big Bang?

In documentaries the Big Bang is often represented as blackness followed by a big explosion with loud noises. This always feels cheap and falling short of explaining the origin of the Universe. Is ...
6
votes
3answers
491 views

Do we expect life to develop only in certain regions of the galaxy?

If I understand correctly, the Earth lies in an area of the galaxy - the "local bubble" - that is relatively free of dust and gases and where no new stars are being born. What is the current theory ...
2
votes
2answers
25 views

Difference between quasar and Active Galactic Nuclei?

Are there any differences between quasars and Active Galactic Nuclei (AGN)? As I understand it, they are both caused by extremely luminous electromagnetic emission from material accreting onto a ...
1
vote
0answers
7 views

Estimating the tangential and cross component of the galaxy's shear using Gnomonic projection

I would like to know how I can estimate the tangential and cross component of the galaxy's shear using Gnomonic projection of the right ascension and declination ...
0
votes
0answers
8 views

Python troubles [migrated]

I've been trying to throw together a python program that will align, crop and create an RGB image from HST and VLA .fits data. Unfortunately I've run into a bit of a problem with it continually ...
1
vote
2answers
76 views

Is a white dwarf hotter than a Red Giant?

From what I've read, white stars are hotter than red ones. But a white dwarf would have just heavy elements to fuse, so shouldn't it be less bright?
3
votes
3answers
50 views

Are multiple satellites required to handle geostationary orbits?

Do geostationary satellites need to have the equator as the plane of rotation, and the earth's centre to be the centre of rotation? Can it rotate over, say, the Tropic of Cancer, focusing on a single ...
2
votes
0answers
13 views

Going from the second moments of an object to its ellipticities and half-light-radius

I am studying ellipticity distributions of galaxies and am having trouble moving from the second central moment matrix (covariance matrix) to properties for an object such as its half-light radius. I ...
3
votes
1answer
46 views

What are Flamsteed numbers?

Can you tell me about Flamsteed numbers? I just know that it is a specific number used for identification of stars. But what is the theory behind it? In what way is the number given to stars?
2
votes
1answer
16 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?

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