Questions tagged [brightness]

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3answers
369 views

Can we visually perceive exoplanet transits with amateur telescopes?

Is it possible for an amateur astronomer to visually perceive an exoplanet transit by the change of brightness of the star via observations spaced over time, or is the variation of the brightness too ...
3
votes
0answers
26 views

What is the average luminance of the star background?

What is the luminance of the star background, i.e. of all the objects outside of the Solar system? E.g. if we measured average luminance of the sky from the far side of the Moon (so that solar and ...
2
votes
1answer
48 views

Why do brighter stars/planets appear physically larger?

Look at Sirius and then some 2nd magnitude star. Sirius appears physically larger despite both stars subtending approximately the same angular diameter. Callisto is far enough from Jupiter at its ...
2
votes
1answer
60 views

When does a solar eclipse become noticeable?

For a human viewer located on Earth, is there an approximate apparent magnitude at which a solar eclipse becomes apparent in the form of a noticeable change in ambient brightness? Assume normal ...
3
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0answers
58 views

In terms of power delivered to Earth, what is the brightest object in the sky?

I was reading about TXS 0506+056, a distant blazar. The Wikipedia article mentions it is one of the brightest objects in the sky at both gamma and radio frequencies. This got me wondering — if we ...
4
votes
1answer
111 views

Can a telescope ever increase the apparent luminance of an extended object?

From what I know about common telescope designs, telescopes don't increase the apparent luminance of extended objects compared to the luminance seen with the naked eye. In this sense extended objects ...
3
votes
1answer
41 views

Strip Brightness in a Spherical System

My question concerns the following problem, published in Galactic Dynamics by Binney and Tremaine and based on a work by Schwarzschild. Specifically, I am having difficulties in deriving the given ...
2
votes
1answer
37 views

How imperceptible will the 4-July-2020 penumbral lunar eclipse be?

Wikipedia's July 2020 lunar eclipse; Visibility says: It will be visible from some parts of North America during moonrise, South and North America, the extreme part of Namaqua Land in South Africa ...
1
vote
1answer
70 views

Is it possible to calculate how much a star's brightness dims when a planet transits in front of it from a viewer's perspective?

Last night I got to thinking about what would happen if Jupiter and Venus suddenly switched places. Since Venus comes the closest to Earth than any other planet and Jupiter is much larger, does that ...
3
votes
1answer
250 views

How do we measure the brightness of the stars?

How do scientists measure the brightness of so distant stars?