Questions tagged [brightness]
The brightness tag has no usage guidance.
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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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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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How bright would an object need to be in order to block out stars at night?
I am wondering just how bright a star or other object would have to be before it starts blocking out the night sky. I'm looking for an answer in apparent magnitude.
I'll note the Full Moon gets to ...
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Bright out north Idaho
It is Oct 9th 10;30- 11:00 pm. I'm in Northern Idaho and it is as bright as it would be with a full moon (or brighter). The moon is going to be new in a few days and the sliver as it is won't be out ...
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Why are sometimes the brightest star of a constellation not named alpha?
From the Wikipedia page of Alpha Ursae Majoris:
Alpha Ursae Majoris, Latinised from α Ursae Majoris, formally named Dubhe /ˈdʌbiː/, is, despite being designated "α" (alpha), the second-...
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Which is brighter, Mars as seen from Earth, or Earth as seen from Mars?
At their closest flyby, Earth is ‘new’ and dim from Mars, and Mars is ‘full’ from Earth and brightest as seen from Earth.
When Earth is 39 degrees from the Sun then Earth is brightest as seen from ...
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Solar eclipse impact on twilight
Has anyone observed the impact of the solar eclipse on twilight? I mean mostly the extension of the totality path in the atmosphere.
I mean the pattern below:
I - normal situation with total solar ...
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Sky surface brightness vs magnitude limit visibility
I am wondering how we can calculate the magnitude limit of the celestial object, which could be visible at the given sky surface brightness conditions.
We already know that Venus and Jupiter are ...
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Surface brightness of transparent vs opaque galaxies
When describing surface brightness of galaxies, I would imagine that in some wavelengths some galaxies are mostly transparent and in other wavelengths some are somewhat opaque (for example galaxies ...
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Does anybody know how to solve this Earth-Venus-Sun problem?
How can I find (in terms of the angle) the moment when in the system Sun-Earth-Venus, Venus can be seen the most bright if its brightness (flow received in Earth) is proportional to the size projected ...
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What's the brightest magnitude that the ISS can appear from Earth's surface?
Heavens-above indicates that this evening, it will fly almost over my head (79°) with a sizzling magnitude of -3.9. What is the maximum brightness it can have?
Is there a formula to calculate its ...
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How bright would Betelgeuse's supernova appear?
Popular science articles suggest that when Betelgeuse goes supernova, for some days it would appear as bright as the full moon. But I have no intuition about a celestial point source that bright.
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Conservation of specific intensity
I am trying to understand the proof of the conservation of specific intensity. Here we are trying to prove that specific intensity at dσ1 and dσ2 along the ray emitted by a source is the same. I don't ...
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Why are galaxies thought to get bigger with distance in an expanding universe model?
In an expanding universe model. In addition to galaxies getting fainter with distance, they are also thought to get bigger. Thus the surface brightness of the object should decrease with distance. ...
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Flashes in the Sky
Short Version: went camping into a very dark, remote location with clear air, no moon.
Was able to see everything from the Pleiades and Orion, to the Southern Cross and the Magellanic Clouds (I live ...
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Brightness and flux density
The alpha star in a constellation has the highest brightness, but does that mean it has the highest flux density among the other stars in the constellation?
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Brightest Stars (by its Apparent Magnitude) List beyond 300
I've been observing the stars and I have found some lists on internet that sort them by its apparent magnitude (m), so you end up with lists of brightest-stars like this one: https://www.star-facts....
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Question about calculating the ratio of volumes of two components of an eclipsing binary star
I'm trying to solve this task:
At the maximum, the eclipsing binary star has a brightness of 6^m, and at a minimum of 8^m. Considering the eclipse to be central and the companion to be dark, find the ...
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What would shadows look like on a planet with two suns?
On planet Tatooine which has two (main-sequence I guess) suns people still have one shadow only. Tatooine's suns seem quite close to each other, so it may actually be the case that the two shadows are ...
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How to calculate apparent brightness in relation to the sun
I know that we can determine the apparent brightness of an object in our solar system using the following formula:
$$B=\frac{A\cdot L_S\cdot R^2}{D^2\cdot d^2}$$
$B$ = Brightness of observed object in ...
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How can the author of this article conclude that earth-shine on the moon is 100 times brighter than moon-shine on earth? [duplicate]
I don't understand the reasoning of the author of this article, on page 26. How can he conclude that full earth-shine on the moon is 100 times brighter than full moon-shine on earth?
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Exoplanet dip in transit light curve when the planet passes behind the star
In the animation below, I don't understand why the brightness slightly decreases when the planet is behind the star.
Where does this effect come from?
user16492
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Why is T Tauri So Dim?
I'm looking at stellar objects and doing some math here and...
Now, I can't find these values directly listed, but from it's relative magnitude and distance, (10.27, 471ly,) I calculate T Tauri to ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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How do we measure the brightness of the stars?
How do scientists measure the brightness of so distant stars?
