2
votes
2answers
84 views

What is meant by “Radial Direction” of a galaxy?

There is a scientific journal article having a line: "In order to study the star formation scenario in the radial direction of the LMC...." What is meant by 'radial direction' of a galaxy ?
2
votes
1answer
53 views

What percentage of visual stars are actually binary stars?

I know this is such a thing as a binary star where for example two stars rotate around a central point of gravity but to the naked eye are just a star. What I do not know is how common this is ...
3
votes
2answers
1k 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 ...
2
votes
2answers
29 views

Why the lows of the GRB 2014-04-27 in Andromeda?

The Swift gamma ray burst space telescope has measured a GRB according to the link below. But why the oscillations in the measured gamma rate? Why wasn't just an increase detected, but also as big ...
2
votes
1answer
52 views

Did the Babylonians believe in the Heliocentric version?

It's mentioned that the Babylonians decreed that there were exactly 360 days in a year. This statement was based upon the utilization of 360 as a standard (based on the sexagesimal system) i.e., they ...
1
vote
0answers
31 views

Torus of the AGN

How much do we know about the structure of the torus surrounding the galactic nuclei? Is the shape defined or still under speculations? And are there different structures for this torus possible i.e., ...
5
votes
2answers
204 views

Why is twilight longer in summer than winter and shortest at the equinox

I recently decided to set my alarm clock to wake me up when it is "dark" out. In the end, I decided to set my clock to the earliest time that nautical sunrise is in my state (Illinois) and stick with ...
5
votes
2answers
1k views

Is Sun a part of a binary system?

Does our Sun have a counterpart, i.e., is it a part of a binary-system? If so, how does the other star look like and where is it?
4
votes
1answer
77 views

What study profiles could land me the job of Astronomer?

I realize there are very few to none universities that offer direct specialization of Astronomy. If I aspired to be make astronomy my career choice, I'd likely have to pick something like physics and ...
4
votes
2answers
71 views

What are shooting stars and how are they formed? [duplicate]

What are shooting stars? How are they formed and how often do they occur during the night? Also, why are there more shooting stars on some nights than on others?
3
votes
1answer
71 views

How would a planetary defence against comets work?

Mappings of practically all potentially dangerous asteroids is well underway. But comets seem almost hopeless to protect against. How far away are approaching comets detected today? How long time ...
13
votes
1answer
201 views

How exactly does inflation convert random gravity fluctuations into coherent gravitational waves?

In the course of this very enjoyable press announcement, it is mentioned that inflation can create gravity waves by amplifying gravity fluctuations. I do not properly understand this statement. I ...
4
votes
1answer
35 views

Calculating Angular Distance

Given the horizontal coordinates of two objects in the sky, how does one go about calculating the angular separation between them?
3
votes
1answer
53 views

Triple Stars v/s Ternary Stars

Ternary (or trinary) stars are not the same as triple stars. So, what is the basic ...
5
votes
2answers
78 views

Are Gamma Ray Bursts of galactic or extragalactic origin?

I read about the 1995 Lamb-Paczynski debate on whether GRBs are galactic or extragalactic in origin. With our current experimental evidence, have we found whether GRBs are galactic or extragalactic?
2
votes
1answer
39 views

How can pre-main sequence stars radiate more energy than main-sequence stars?

How can a pre-main sequence star radiate more energy by gravitational contraction than a main-sequence star can by hydrogen fusion?
3
votes
2answers
105 views

Why do pictures of the Milky Way look like a spiral?

When I see pictures of the Milky Way they show a spiral shape. Why is this?
4
votes
1answer
36 views

Active Galactic Nuclei - categorisation on the basis of observer?

As we know AGNs are considered to be one of the most luminous objects to be found in the cosmos.Based on the observer, for instance on Earth, we categorize them on the basis of the angle between the ...
3
votes
1answer
40 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
1answer
67 views

Taking Advantage of Time Dilation

According to Einstein's theory of Special Relativity, one's speed in relation to a relatively stationary object would 'slow down' time on the moving object. With this in mind, would it be possible to ...
4
votes
1answer
22 views

2SB mixer in radio astronomy?

In literature about the instrumentation of radio astronomy, I frequently come across a type of mixer described as "2SB". I'm familiar with single-sideband (SSB) and double-sideband (DSB) mixers, but ...
6
votes
1answer
60 views

Calculation of Horizontal Coordinates

Given a fixed coordinate location on Earth (i.e. a latitude and longitude), and a fixed equatorial coordinate location of a particular astronomical object in the sky (i.e. right ascension and ...
2
votes
2answers
156 views

Where is a Hollow Object's Center of Gravity? [closed]

Let's imagine that the Earth's moon is hollow. Given this scenario, where would its center of gravity be? What would the conditions be like at the center? Also would one still be able to stand on the ...
2
votes
1answer
134 views

Meaningful theories of the shape of the universe

Normally, when people say "the universe is infinite" they generally mean something like "the observable universe is locally flat, it is easy to assume that it is flat way beyond the observable ...
1
vote
2answers
84 views

What does “Normalized to Si 10 to the power 6” mean?

I'm writing a space game that I want to give a more "realistic" feel. When looking for a reference as to distribute elements in planets (for mining, etc) Instead of finding the more usual percentage ...
1
vote
2answers
53 views

Do origin theories imagine each planet to first orbit the Sun very irregularly before stabilizing?

What I was wondering is that, for example, toss a few balls into zero gravity space randomly, what would be the steady state motion? Would not all the balls go on weird directions and undergo ...
-3
votes
1answer
83 views

Active Galaxies

I've read that there are 4 distinct although related forms of AGs : Seyferts, Quasars, Radio and Blazars. Are there any other forms possible? Also do these forms ever intermix to give something new?
3
votes
1answer
83 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 ...
1
vote
0answers
23 views

golden and red colored light even after Sunset [closed]

I heard about golden hour but today i saw golden and red colored patches in sky even after Sunset. why it happens? and would like to know more about science behind golden hour.
1
vote
1answer
89 views

How big would a disc have to be to blot out the sun covering 5% of the land mass of earth?

Like this, but floating in space. I imagine that this would also be influenced by the distance of the object from the sun, and that there is some ideal distance for this object to be? (and ...
1
vote
1answer
25 views

how steady over time are right ascension and declination values?

I understand that astronomers use right ascension and declination for the position of stars. However both these values strike me as very anthropocentric and, more importantly, unreliable over time as ...
6
votes
1answer
81 views

How are the masses of celestial bodies determined?

I was scrolling through the list of moons of Jupiter and I wondered how astronomers where able to determine the masses of those objects. When I tried to google it I meanly found results of people ...
8
votes
1answer
91 views

Mechanisms of binary/multiple star formation

What are mechanisms of binary/multiple star formation in different mass ranges (low, intermediate and high stellar masses)?
4
votes
1answer
78 views

What kind of collision of celestial bodies would be visible to the naked eye?

When asteroids crash into the Moon they give of huge amounts of energy resulting in a "bright" flash, as can be seen in this video. At the end of the video its also says that anyone looking at the ...
2
votes
1answer
48 views

Broadband spectrum of Sun

Broadband spectrum is one which is inclusive of all the observed wavelength ranges. In the case of the BB spectra of our Sun, there is a sharp (non-differentiable) kink in the curve in the UV-range ...
1
vote
1answer
59 views

Is the expansion of the universe proof of the big bang?

Is the expansion of the universe proof of the Big Bang theory? Or are there other proofs?
4
votes
1answer
95 views

How did astronomers first come to understand that the Sun's core was a gas?

I was reading a very old book (around 1850) on astronomy and the author explains Sun spots as a phenomena where you can see the black planetary like hard core of the Sun through two different ...
1
vote
1answer
117 views

A day in earth, a thousand years somewhere else

By followig the laws of physics, is it possible, that in a place far far away that one day (at that place), is counted as 1000 years in the earth. I am familiar with black holes having impact on ...
0
votes
2answers
97 views

Determine north just by one shadow

I am not sure if this is the right place to post at, but I tried to find the best place to do so. To my point, I wonder if it is posssible, to determine where north is, just by one shadow, that means ...
6
votes
3answers
75 views

Flatness of the universe?

How does inflation explain why the curvature in the early universe was flattened out and now results in a flat universe?
0
votes
2answers
110 views

Does Earth revolves around Milky Way?

As we know Earth rotates around Sun and Sun around Milky Way but then Sun must have some velocity/angular momentum (I don't know that much physics terms). So as Earth revolves around Sun, it must ...
6
votes
2answers
159 views

Why do we have the cosmological constant?

Since the cosmological constant is not required to explain that the universe seem to be expanding, why do we have it? What other factors cause us to have that constant? Background: Without the ...
3
votes
1answer
85 views

How many black holes exist?

How many black holes exist and what is their distrubtion over mass? There is a list of black holes, but I'm interested in an estimate of all black holes in the visible universe.
5
votes
1answer
95 views

Would space-faring vehicles in interstellar space be in pitch darkness, show reflections from the nearest star or be bathed in light completely?

This is not a science fiction question, but I was considering the visual accuracy of ships in space depcicted in Battlestar Galactica and the like. They are always strongly lit. If they are in ...
4
votes
1answer
157 views

How many earths fit in the observable universe?

I was pondering our insignificance, when I wondered - how how much smaller is our planet then the (observable) universe? And being as I dont know how to do the math, I'm asking it here. So how many ...
3
votes
5answers
128 views

Could there be life beneath the surface of Mars or moons?

I realize radiation and extreme temperatures would probably destroy life on the surface of most planets and moons, but could life exist beneath the surface (e.g. like earth worms on earth)?
0
votes
1answer
108 views

Can Mercury hit Earth or Mars in the next 5 billion years?

Mercury is the most unstable planet of the solar system, with an oscillating orbital eccentricity (between 0 to 0.45). It seems there is a 1% probability in the next 5 billion years Jupiter and ...
35
votes
4answers
5k views

Is the moon only 60 pixels?

In doing research on vision, I have learned that "20/20" vision corresponds to a visual acuity of being able to resolve details 1 arcminute in size, that most people have around 20/15 vision, and that ...
3
votes
2answers
91 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 ...
-1
votes
2answers
157 views

What would happen if a planet is removed from the solar system? [closed]

More exactly what would to happen to us/Earth in general if any of the gas giants is removed by magic from the solar system ? How long would it take after such change before we notice it ? How major ...

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