Questions regarding electromagnetic radiation in the visible spectrum.

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3
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1answer
60 views

Why the light curve goes down when the planet is behind the star?

There is a video explaing the transiting exoplanet light curve — https://www.youtube.com/watch?v=RrusIZaWDW8 It is clear to my why the curve goes down when the planet is between the observer and the ...
3
votes
3answers
71 views

Can't we see all of the Milky Way's supernovae with the naked eye?

I found this on the Wikipedia page on supernovae: The total supernova rate in our galaxy is estimated to be about 4.6 per century, or one every 22 years, although we haven't actually observed one ...
1
vote
1answer
29 views

What does the filter name I+z' mean

On the TRAPPIST telescope, the filter wheels are described to have a filter with the following description: NIR Luminance I+z' (>700nm) After a bit of googling, I wasn't able to find what the ...
2
votes
2answers
117 views

Solar Pressure and Gravity

I recently read some articles and pages on Solar Sails, and the possibility of using lasers to propel spacecraft, and I had a relatively outlandish idea. Would it be possible for a star to be ...
1
vote
1answer
86 views

How long can you be trapped orbiting around a black hole for?

I have a story I wanna write but I want to be sure it's not completely scientifically irrelevant. I know there is black hole modelisation called the Kerr black holes, in which there is a limit ...
0
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0answers
96 views

In a finite universe, what happens when light reaches the boundary?

If a universe is finite and is not expanding at a speed equal to or greater than c, what happens when light or another form of electromagnetic radiation traveling reaches the boundary?
5
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1answer
101 views

What would the night sky look like if the interstellar medium didn't exist to absorb or block light?

I was curious about how much brighter it would be and how much further we could see.
0
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1answer
53 views

LLR & Orbital Motion

As I understand it, light that is emitted from a source is not imparted with the motion of the source and so always follows a "straight line". If this is correct, I am having a difficult time ...
0
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2answers
127 views

Are we made of stars we're seeing? [duplicate]

a fresh astronomy enthusiast here. Recently I've been reading upon how immensely far other stars are from our solar system and how is it possible that we may be seeing stars that are already dead. My ...
0
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1answer
41 views

Why weren't the Hubble light-echo images of V838 Monocerotis supplemented by ground telescopes?

Drawing from this answer The V838 Monocerotis expansion (not a supernova) and the observation of the subsequent "spectacular" light echo was quite a notable event! From Nature 422, 405-408 (27 ...
0
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2answers
56 views

V838 Monocerotis “light-echo” images morphed into nice video, but why so few original images?

This NYTimes video shows what I think is a series of real Hubble images which have been "morphed" artistically to appear to be continuously expanding. (also see The V838 Monocerotis Star Still Has ...
0
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1answer
43 views

How high does light pollution reach into the sky?

I want to know how high does light pollution typically reach into the sky STRAIGHT UP? Has anyone ever researched this because I wonder if being at 10000ft elevation would reduce the amount of light ...
0
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1answer
38 views

The relation between the light of full moon and the distance between the sun and the earth

If we want the full moon to be 2 times more bright,how we should change the distance between the sun and the earth? Thanks for your help.
3
votes
1answer
49 views

Gravitational Waves and the Big bang

The Ligo website says "Detecting the relic gravitational waves from the Big Bang will allow us to see farther back into the history of the Universe than ever before." I find this puzzling. How can a ...
18
votes
3answers
4k views

Why can't moon light (reflected sun light) turn the sky blue?

Does turning the colour of the sky blue need more luminous light? Does it depend on luminosity or some other factors are also responsible for this phenomenon? Why can't the moon light turn the sky ...
2
votes
1answer
68 views

Given a collection of pixels, how to deduce the flux from them?

I've obtained the coordinates of brightest pixels from different images (.fits files) using Python. I want to get the flux of each pixel. How do I go about finding out the flux?
25
votes
2answers
4k views

Why doesn't the moon twinkle?

Stars twinkle because their light has to squeeze through several different layers of the Earth's atmosphere. So why doesn't the moon twinkle as well?
0
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2answers
61 views

Regarding the age / size of the Universe [duplicate]

I believe the current estimated age of the Universe is around 14 billion years. I just read in another post on here that the diameter of the Universe is around 90 billion light years. This doesn't ...
1
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2answers
55 views

What is the longest observable wavelength of light using an optical telescope?

How far outside the visible spectrum could an optical telescope feasibly operate?
2
votes
1answer
49 views

In what manner is the spectrum of a black body really a continuum?

Usually they say the spectrum of a black body is a continuum and emits radiation at every frequency. Is it really a continuum like a line or are there (small) intervals? For example, can a body emit ...
0
votes
1answer
97 views

When stars explode why can we still see them?

This might be a silly question but if light travels at the speed of light and time is frozen in that speed then why the stars we see could be dead already and not just instantly disappearing from the ...
2
votes
2answers
37 views

Is the colour of a wave from a far galaxy the same for us as for a galaxy which lies between?

Because of the expansion of the universe, light from a far galaxy is redshifted. The expansion of the universe will make the wavelength of light longer. But is the colour of such light the same for us,...
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3answers
73 views

Can “dark matter” be the additional mass from the speed of the Galactic Cluster?

Considering that the Earth orbits the Sun at 100 000 km/h and that the Sun orbits the Milky Way at almost 1 000 000 km/h, could it be possible that the galactic cluster orbits some super cluster at ...
4
votes
2answers
52 views

Which planets have abundant amounts of photoluminiscent matter?

Which planets have abundant amounts of photoluminiscent matter? Photoluminiscent or chemoluminiscent whatever the glow-in-the-dark stuff it may be. Planets or bodies which have good enough the ...
3
votes
1answer
95 views

Would I actually be able to see Ceres without shining a really bright torch onto it?

NASA's put out a semi-CGI video of a Ceres flyby using material from the Dawn mission. Now I realise that visibility is relative, even on Earth: I can walk into my basement and not be able to see ...
2
votes
2answers
132 views

Why isn't everything yellow(ish)?

I understand that - although appearing yellow - the sun is white. And that this is because the other light colours are scattered by the atmosphere. For example: Google image search for "The Sun from ...
1
vote
1answer
78 views

What was James Bradley's calculation to calculate the speed of light?

Looking into the history of how the speed of light came to be determined, to what we know it to be today, James Bradley is often mentioned. He was credited with the discovery of the aberration of ...
2
votes
1answer
116 views

Is Darkness Faster Than Light?

I've been looking around, and can't find a solid answer. Many websites say darkness is the speed of light due to the fact it is the absence of light, but other sources say otherwise, that in some ...
14
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6answers
3k views

Are we still going to have rainbows if Sun is replaced by another star?

Rainbow is a property of light splitting due to the water molecule present in the clouds and is related to the light emitted by our Sun. Our sun is a yellow star. Now if we replace sun by a blue giant ...
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2answers
84 views

Plausible? Brown Dwarfs are rogue celestial bodies because they absorb all light due to their thick layer of matte black soot [closed]

My theory of why Brown Dwarfs are the rogue celestial bodies that travel through galaxies without a set course. My first theory would be their matte black in color due to a layer of soot.Light does ...
1
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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?
0
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1answer
60 views

TIME TRAVEL-Can it be really done? [closed]

Is it posssible for us to time travel? Is light essential factor or the dark matter and dark energy?
4
votes
3answers
355 views

Is a black hole a perfect sphere?

I know all about how black holes form and why their gravity is so strong. However, is the gravity equally powerful in all directions? Will the event horizon appear as a perfect sphere?
3
votes
0answers
78 views

How does light so travel so fast?. [duplicate]

I've read that photon's have zero mass, hence no force is needed to accelerate them. But then the second question. How can gravity affect something which has 0 mass?. Yes, gravity(black hole) can bend ...
2
votes
1answer
73 views

Travelling at light speed(inside water) [closed]

It is a said fact that 299792458 m/s is the speed limit,nothing can go faster than this speed, or it will take an infinite amount of energy for propulsion.What we perforce in vacuum is one thing.Can ...
0
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2answers
6k views

Star like light moving in the sky, what could it be?

I was camping this weekend away from the city, so my friends and I decided to spend one of the nights watching the sky, since it's impossible to see anything around where we live. After a little while,...
2
votes
1answer
34 views

how to assess a periodical signal?

After folding a light curve, we may get some kind of shape. How to tell whether there is a real periodical signal quantifiably? The fluctuation may be small, and the folded shape may not be perfect.
3
votes
2answers
308 views

Is the ratio between earth's distance from the sun and the speed of light just a coincidence?

I was doing some calculations to see how hard it would be to observe the speed of light and discovered an interesting correlation between the speed of light and the average distance from the earth to ...
3
votes
1answer
165 views

How much illumination do the background stars provide?

I'm trying to get a better understanding of what things look like in "outer space." The main problem I'm trying to solve right now, is how much illumination is provided by the background stars. Is it ...
3
votes
3answers
114 views

What is the average color of the universe?

Our Earth, being a beautiful blue orb, has an overall perceived wavelength of somewhere near 470 nm, that being the wavelength of light blue, because the oceans play an enormous role in the weighted ...
10
votes
1answer
237 views

How did New Horizons take such well-lit pictures of Pluto?

The photos of Pluto from New Horizons are truly beautiful. But considering that Pluto is so far away from its nearest start - our Sun - how is it so well lit up? Did the New Horizons have a massive ...
5
votes
1answer
71 views

Why do some artificial satellites decrease and increase in brightness multiple times?

I just observed a satellite almost directly above me travel for a few minutes while constantly dimming and then getting brighter. It did this for about 3 minutes until it faded out. I also observed a ...
4
votes
1answer
52 views

Speed of light through the ISM and Wavelength

Articles written about fast radio bursts describe the signal's short-wavelength components arriving before its longer-wavelength components, suggesting energy-dependent time delays in the interstellar ...
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0answers
88 views

Energy required for light speed [closed]

It is said that in order for us to travel at the speed of light, there has to be an infinite amount of energy. Light is made up of photons but photons themselves do not have an infinite amount of ...
4
votes
1answer
293 views

How to calculate the limiting magnitude of Hubble?

I've found various sources on the web stating that the limiting apparent magnitude of the Hubble Space Telescope is about 31 or 31.5. Wikipedia lists that here and it has a cite to a pdf about it. ...
3
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3answers
456 views

How does gravity interact with a photon?

If photon is mass-less and gravity can interact only with matter, then how does gravity alter the trajectory of light?
6
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4answers
517 views

Does Sun have a reflection on Earth?

The new Google Maps1 presents an actual view of Earth, with the current position of Sun illuminating half part of Earth in real time. It is quite an exquisite view. My question is based on the ...
3
votes
3answers
2k views

What's in the center of a Galaxy?

Ok, so it's supposed that there is a black hole in the center of any galaxy, that makes my head explode because: There is light in the center of the galaxy, but it is supposed that black holes, also ...
0
votes
1answer
44 views

Sunsets: Mars/Earth

I understand why our sky is blue and turns red when the sun sets or rises. I know why the sky on mars is red, but why does it turn blue during sunsets and rises? Shouldn't this actually not work due ...
2
votes
3answers
416 views

Longest and shortest wavelength

What is the longest and what is the shortest wavelength of light? How fast would a light-emitting object have to recede in order to shift the frequency of light to increase the wavelength from the ...