Questions tagged [brightness]
For questions regarding the brightness of astronomical bodies
46 questions
1 vote
1 answer
143 views
What would someone sitting in orbit around one of the gas giants see with unassisted eyes? (Brightness levels)
*Assuming they are wearing a spacesuit of course. I know that the sunlight intensity decreases exponentially as we get further out - Jupiter and Saturn get only a couple percent of what Earth gets, ...
12 votes
1 answer
733 views
Why is Deneb brighter than Mu Cephei?
If my facts are correct, Mu Cephei is 2,840 light years from earth and Deneb is 2,600 light years from Earth. While the difference of 240 light years is not insignificant, it seems that it is not ...
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5 votes
0 answers
329 views
Are artificial Earthly radio emissions "brighter" than the Sun's?
I was reading this answer to a question from a person paranoid about the Voyager probes, which elaborated that the Earth itself had been outputting gigawatts of radio emissions into outer space since ...
- 4,409
-1 votes
1 answer
385 views
Sirius and Polaris Luminosity vs Brightness?
Why is the luminosity of Sirius less than Polaris, yet Sirius is claimed the brightest star in the sky? I read that Sirius is the brightest star in the sky however am reading some conflicts that ...
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0 votes
1 answer
396 views
Why aren't planets easily visible during daytime?
Let's consider stars. They emit a certain amount of radiation. If you move 2x farther from the star, the radiation reaching you follows the inverse square law so you get 1/4 times the amount of ...
- 223
2 votes
1 answer
363 views
What is the unit for 'magnitude' in terms of the Isophotal diameter of a galaxy?
Every site and AI and Google say that one way of measuring a galaxy's diameter is in terms of its isophotal diameter, using the blue D25 standard, using units of, "25 mag per arcsec2". But ...
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2 votes
1 answer
133 views
How to estimate artificial satellite brightness as seen from another satellite?
I'm looking for a way to estimate an object's brightness as seen by an observer in space. I expect the estimation to depend on factors such as the distance to the Sun, the Sun-satellite-observer angle,...
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3 votes
0 answers
104 views
Closest/farthest point where the sun stops being the brightest star?
Which is the closest point to the Sun where it's not the brightest star anymore? My intuition is that this is either on a direct line between the Sun and Alpha Centauri, or between the Sun and Sirius ...
2 votes
1 answer
733 views
How bright in the night sky would J0529-4351 (brightest quasar ever found) be if it were in our galaxy?
According to this article, the quasar (black hole) named J0529-4351 is the most luminous object in the known universe, being: 500 trillion times more luminous than the Sun To put it in terms easier ...
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3 votes
1 answer
282 views
Calculation of twilight sky surface brightness based on object's apparent magnitude
I would like to be able to compute the sky surface brightness, which is based on the object's apparent magnitude. We have formulas, which allow us to compute the sky surface brightness based on the ...
- 225
7 votes
1 answer
1k views
Human Brightness perception and contrast
This is kind of an interdisciplinary question on human brightness perception and the ability to distinguish grayscales. To be honest, I wasn't sure if the Physics, Biology or Computer graphics SE site ...
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16 votes
2 answers
4k views
Why was Jupiter so bright; is it the "phase"?
When I was walking in the evening (2023-12-30) in the south of Germany (roughly 49°N 12°E) I noticed a single bright object in the sky, and (not being an astronomer) I wondered what it might be. So I ...
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1 vote
1 answer
133 views
Visible angular size
Is it true that given two celestial objects of the same size and at the same distance, the fainter one will appear smaller? Is there a calculation that can be made about how smaller? Is it the same ...
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3 votes
1 answer
161 views
Does the reflected light from Earth boost Venus' apparent magnitude when it is seen transiting the Sun?
During solar transits of Venus as seen from Earth, exactly 0% of Venus' disk is illuminated by sunlight, as expected. However during these transits, Earth is at opposition and fully illuminated by the ...
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2 votes
1 answer
83 views
Standard definitions (ISO?) about subjects related to light emitted by stars
I'm a big fan of astrophysics and astronomy. However i'm quite confused by reading these last years plenty of books on the subject with various definitions (vocabulary) and notations for the same ...
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