1
vote
1answer
64 views

Looking back in time by looking further away

I have been pondering the question of how we can look back to the state of the early universe for some time. So I came here and found, to my delight, that several such questions have been asked, such ...
6
votes
2answers
755 views

When was the term “orbit” (in the modern sense) first used and by whom?

Wikipedia coyly suggests that some notions and views kept circulating (apparently since Adam and Eve) until finally Kepler, of all people, ... etc. I find this hard to believe. Please elucidate.
1
vote
1answer
367 views

Does this black hole magnetohydrodynamics equation even superficially make sense?

My question is about the journal paper mentioned in an Academia Stack Exchange post. Please understand that this paper has never been posted on arXiv, and I can provide only a link whose content is ...
1
vote
2answers
116 views

why hasn't Nasa gone back to our Moon? [closed]

why has not Nasa gone back to our Moon since the first landing on the moon
17
votes
7answers
3k views

How can we focus radio telescopes on a star when the earth is spinning?

Reading about the Star KIC 8462852, it has been said that the SETI project turned its radio telescopes towards the star to search for extra terrestrial radio signals as the star had strange ...
2
votes
2answers
92 views

Is time itself speeding up universally?

Time moves more slowly near a mass than in relatively empty space. For example, I get that an observer would see someone falling into a black hole to appear to move more slowly and get "stuck" on the ...
1
vote
1answer
93 views

What's the difference between the apparent horizon and event horizon of a black hole?

The Wikipedia page for apparent horizon is pretty sketchy and requires some GR knowledge. Is there any simple definition?
2
votes
1answer
138 views

Need help with the math in Python program to flag Jovian radio emissions

A few days ago I decided to take on the little project of converting a Qbasic program into Python (as a side project to my Radio Jove project), and I've managed to get it to run, but the math is ...
2
votes
1answer
84 views

Has the most luminous object in the universe been found?

It's hard to search through the entire (observable) universe, but the most luminous thing there is must on the other hand be easy to find. Can we now say that the most luminous quasar we know, is the (...
4
votes
2answers
163 views

How does the appearance of the analemma vary with latitude

How does the appearance of an analemma vary with latitude? This what I take to be a definition of an analemma: If the position of the sun is plotted or photographed at noon clock time (say UTC) every ...
3
votes
1answer
141 views

Is the mechanism of solar flares on red dwarfs and brown dwarfs the same as that on the Sun?

The Sun has solar flares that are caused when there is a magnetic reconnection in the Sun's atmosphere, causing a loop of magnetic field to be ejected at high energy, along with a large number of ...
3
votes
1answer
137 views

What you would see in a wormhole?

Science fiction seems to depict the experience of traveling through wormholes (if possible of course) as seeing psychedelic colors or lines of light where stars once were (ie. 2001 or Contact). I ...
1
vote
0answers
35 views

Extra dimensions [closed]

String theory, Kaluza Klein theory etc. need extra-dimensions. For string theory these are compactified. My feeling is that these extra dimensions are not of our 4-D space, but are only of the space ...
5
votes
1answer
54 views

Diameter of Astronomical Object Using Magnification

I took a picture of Jupiter through my telescope, using an iPhone. I know the magnification of the telescope lens I used, and can Google to get the magnification of the iPhone lens (the magnification ...
4
votes
6answers
225 views

How can an infinite universe expand?

I understand the expansion of the universe as actually an increase in the ratio of space to matter. Is this a correct understanding? Otherwise, I don't understand how an infinite structure can expand....
1
vote
2answers
52 views

can we use connect a long pipe with space station and use vacuum for fuel transfer? [closed]

We all know that we need a lot of fuel to escape from earth. Even 90% fuel of an spaceship is wasted in escaping the earth which definitely affect our power to explore the universe. we have to do a ...
3
votes
2answers
59 views

Luminosity of black hole accretion disc

The luminosity of a black hole accretion disc gaining mass at a rate $dM\over dt$ can be estimated as ${1\over 12}{dM\over dt}c^2$ That is a substantial proportion of the rest mass of the in-falling ...
1
vote
1answer
167 views

If the Universe is infinite, would heat death be impossible?

If the Universe is infinite, one would imagine that if we kept moving through space, we'd constantly find newer and newer galaxies and objects forever. This would imply that there is an infinite ...
4
votes
0answers
80 views

Is there an upper limit to the mass of terrestrial planets

The exo-planet Kepler-10c has a mass between 15 and 19 times the mass of the Earth (making it comparable in mass to Neptune), and yet is thought to have a density of about 7g/cm^3 and to be a ...
1
vote
0answers
63 views

Why does spectral class and U-V colour correlate slightly differently for main sequence, giant and supergiant stars?

In this diagram the $x$-axis is spectral type for stars and the $y$-axis is B-V colour. Taking Series 1 as the Main Sequence, Series 2 as Giants and Series 3 as Super-giants. Why the spectral class ...
1
vote
2answers
146 views

Could a star revolve around a planet? [duplicate]

They actually do, but let's set Relativity aside for a moment. And the whole barycenter thing too. Here's the scenario: Somewhere in the backwaters of a galaxy there is this huge planet. It is NOT a ...
2
votes
1answer
52 views

Age of Occator Crater

Has any official information been published regarding the estimated age of the Occator crater on Ceres? I ran some quick searches but couldn't find anything putting a definitive (or even speculative) ...
2
votes
1answer
34 views

Formation of a magnetosphere for gas giants / small stars

This question got me thinking about this. Jupiter has, and presumably super-Jupiters can have a strong magnetospheres. A solid metallic core and rotating material around the core, creates a magnetic ...
2
votes
3answers
75 views

Orion Constellation request

This isn't a question so much as a request. I'm looking for an image of the Orion constalletion I could use, but I would like to have a very high resolution HD image, whereby a lot of the deep sky ...
5
votes
1answer
115 views

How small a star can provide Sun-level illumination to its planets?

...or how small can a solar system be, to sustain an Earth-like planet? Sun is not really small, and 1AU is pretty far when you look at orbital radii of exoplanets and size of their stars. How small ...
1
vote
1answer
119 views

Conversion of magnitudes to Jansky and MAGPHYS?

I'm a bit puzzled and not an observer, so please bear with me if I'm being stupid here. The code MAGPHYS specifies Jansky (Jy) as the input unit for flux through ...
8
votes
1answer
69 views

What are the best candidates for solar lensing of exoplanets, and what would the results be?

If we were able to send a probe to 550AU from the Sun, which exoplanets could be examined, to what resolution, and what form would the examination take? It is radio telescopy only, or would it be ...
5
votes
2answers
183 views

Is there any hard evidence that rogue planets exist?

A rogue planet (or a rogue anything, for that matter: a celestial body other than a star) is something that's drifting through space without being attached by gravity to any star. They're just out ...
1
vote
1answer
122 views

How do we know which elements are in a galaxy spectra?

I know that each element has it's own distinct spectra (this is a good site that lists them: Periodic Table) but when looking at a spectra of a galaxy (or even a star) how do we match those elements ...
11
votes
2answers
2k views

Is Earth unique in its fairly clear atmosphere?

So, we have surface pictures from two alien planets, Venus (captured by the Venera 13), and Mars (captured by the rover). Both of these pictures appear to be very dusty. For Venus we see strong ...
2
votes
1answer
48 views

Divide a star catalogue to optimize star search

I'm continue working on my Planetarium software and I have a doubt. At this moment my star catalogue is very small, but I'm planning to use a bigger one. To optimize the search inside this catalogue ...
3
votes
1answer
62 views

Is the size and heat of a star important in the development of a solar system?

How do the size and heat of stars affect development of solar systems and what kinds of planets can develop? Is it possible to orbit supermassive stars? Furthermore, would star's unleashing violent ...
3
votes
2answers
412 views

Equation to find distance between objective and eyepiece

I have a home made astronomical telescope with 100 cm objective lens and 5 cm eyepiece.when viewing an object in infinity the distance between eyepiece and objective is 105 cm. So how could I ...
2
votes
2answers
175 views

Can we have a second moon?

This question sounds like silly and rather fantasy filled. But can our earth's gravity capture a sizable asteroid and make it rotate around our earth like our moon which become visible from ground. Is ...
3
votes
2answers
88 views

Is it plausible that Mars could have been one of Jupiter's natural satellites at one time?

Would more questions regarding the planet be answered if this was the case?
2
votes
1answer
46 views

What is Color Index?

I found this Wikipedia page on this property called color index. Unfortunately, I could not find a source that explains this property well. My interpretation is that color index is the brightness ...
3
votes
1answer
125 views

Does the Sun orbit the Milky way in a (kind of) flat or inclined orbit or more of a sine wave? [duplicate]

I know it can't be a perfect ellipse or smooth orbit due to all the matter in every direction, and our Sun could be affected by a gravity assist of sorts if it passes close enough to another massive ...
2
votes
4answers
145 views

Notable differences if all stars would disappear except the Sun

I am not an astronomy expert, but as of today, all other stars than the Sun have little to no effect on life on Earth. So I was thinking, would there be any differences for the Earth at all if all ...
5
votes
1answer
227 views

Can a gas moon exist?

Could a gaseous moon exist in the same way as a giant gas planet? All the moons in the solar system are rocky, or icy. Why shouldn't gas planets have gas moons?
3
votes
1answer
179 views

Is a black hole heavier than the star from which it was created?

I did some googling around and couldn't get answer to a simple question of black hole mass compared to the star from which it was created. It is well known that giant stars burn very bright and ...
5
votes
3answers
163 views

Visibility of human activity on the moon

In this video the host of Test Tube Plus states that you can go out a buy a laser, point it at the moon, and see the retroreflector left by the astronauts. When you point at the right spot you'll ...
1
vote
1answer
113 views

Where did everything come from?

Where did all the material and gas contained in our universe come from? If it was the size of a "coin," then it could not have contained all the matter that is in our universe today before the Big ...
3
votes
0answers
58 views

How bright can white dwarf stars glow as they accrue matter?

I realize this is kind of general as it would depend on the size of the white dwarf and the rate of accrual. The general idea I got thinking about is what would happen if a white dwarf star - lets ...
8
votes
3answers
251 views

How do we know that our galaxy is a spiral galaxy?

I know that our galaxy is spiral in shape, but I'm wondering how the scientists found out that our galaxy has a spiral shape. I don't think we can see the entire galaxy from telescopes on Earth, ...
1
vote
2answers
97 views

Are objects in the universe moving away from each other at the same acceleration?

This is a follow up question to Does the universe expand at the same rate everywhere in the universe?. If the universe is expanding, then it would seem necessary for each object (ie galaxy) to be ...
2
votes
1answer
51 views

What is the share of stars in total radiation input of Earth?

Earth gets its radiation input primarily from Sun, then from reflected sunlight from Moon, and stars. Among these, what is the share of stars (or sources outside solar system) to this total radiation ...
2
votes
1answer
85 views

How can the observable universe be so small if there are so many stars in it?

The observable universe has a radius of about 46.5 billion light years. That’s big but I just wonder how that can be big enough to fit in everything we know exists in the universe. There are hundreds ...
3
votes
1answer
89 views

Is there a photo that shows a iron meteor or asteroid in space in raw form having no layers of fusion crust?

A raw iron meteor or asteroid in outer space should be in its raw form having no signs of fusion crust from the friction of atmospheric entry and should therefore show distinctive signs like the ...
3
votes
1answer
160 views

Why is the Color scheme of natural satellites in our solar system based of light shades of grey?

What is the explanation of the color similarity that the majority of natural satellites obtain?
1
vote
0answers
53 views

What would be the maximum theoretically possible angular resolution?

I have studied some basic astronomy, but I have difficulty conceptualizing the physics of luminosity and optics. We use electromagnetic spectra to detect existence and properties of distant planets, ...

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