Questions tagged [apparent-magnitude]

Questions regarding how bright an object appears to be.

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How could a hobbyist astronomer determine apparent magnitude of a star?

Apparent magnitude is a rather complex way to determine the brightness of a star. Quoting the introduction text from the linked to Wikipedia page: The apparent magnitude (m) of a celestial body is ...
TildalWave's user avatar
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32 votes
3 answers
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Is the Sun visible from Proxima Centauri to human eyes?

I know that the light coming from Proxima Centauri is not bright enough to make it naked-eye visible from the Earth. Is the Sun naked-eye visible from Proxima Centauri?
Patrick's user avatar
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27 votes
4 answers
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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 ...
Mark Besser's user avatar
23 votes
2 answers
4k views

At what distance from Earth would our Sun be the same apparent magnitude as the next brightest star in the sky?

When I stand outside looking at the night sky, to my untrained eye, everything except the moon looks like a star. I know intellectually that some are planets circling our sun, and some are entire ...
James Jenkins's user avatar
15 votes
2 answers
5k views

How bright is the full Earth during the lunar midnight?

At lunar midnight (i.e. the new moon as seen from Earth), the Earth is in its full phase with its entire disk in sunlight, and it is the brightest object in the lunar sky. How bright is it, and how ...
Emilio Pisanty's user avatar
13 votes
4 answers
4k views

Could Neptune be viewed with the naked eye from Uranus?

Which star or planet in our night sky can match what Neptune would look like when viewed from Uranus, or one of its moons? The answer would be for the most favourable condition, which is when Neptune ...
Constantthin's user avatar
11 votes
1 answer
1k views

Why was the standard distance set to 10 parsec and not simply to 1 parsec?

On closer inspection of the absolute visual magnitude and the apparent visual magnitude of the sun, I noticed that their magnitude range (4.83 + 26.74 = 31.57) exactly matches the human eye. The ...
SmilySunMike's user avatar
11 votes
1 answer
435 views

If Planet Nine indeed exists, how large a impact event there should be to be seen from Earth?

Recently I've found this news article, A meteorite crashed into the Moon during total lunar eclipse in January, about a collision into the moon that happened while a lunar eclipse was under way. ...
ksousa's user avatar
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9 votes
2 answers
2k views

How bright will Alpha Centauri A be from Earth when it becomes a red giant?

As of right now, both stars from Alpha Centauri are in their main sequence stages, but eventually Alpha Centauri A is going to quickly expand in a matter of time, and I’m pretty sure its luminosity is ...
Prince Pugs's user avatar
9 votes
2 answers
5k views

Why are nearby stars like Proxima Centauri and Barnard's star not visible to the naked eye?

Proxima Centauri is the closest star to the earth other than the sun yet it isn't visible to the naked eye, but stars that are further away are easily found in the night sky. Why is that?
immanebula's user avatar
9 votes
1 answer
518 views

What is the brightest star (relative magnitude) in M31?

I am wondering what the brightest individual star is in M31, the Andromeda Galaxy. Specifically, brightest as seen from Earth (so relative magnitude).
NeutronStar's user avatar
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8 votes
1 answer
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Determining the extinction by counting stars?

Hi I'm a highschool student studying astronomy at school. I learned that one can determine how much a luminosity of a star is reduced by counting stars, but I can't understand how it works. My ...
DH K's user avatar
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8 votes
1 answer
236 views

Adhara ultraviolet magnitude

I see Adhara is cited in many places (for example, here) as being the brightest source of ultraviolet light in the sky. The particular source uses the modifier "extreme", but most other ...
L. Scott Johnson's user avatar
8 votes
3 answers
2k views

Why do dark objects look white from a distance? (Moon, Ceres, but not Earth!)

What makes the Moon shine white in the sky, although it seems to be as dark as asphalt? Earth's average albedo is 3 and 4 times that of the Moon and Ceres respectively (0.37 vs 0.12 and 0.09). But ...
LocalFluff's user avatar
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8 votes
1 answer
171 views

How many photons does it take to determine the existence of a distant object?

This applies to any object, but I see the recent discovery of the oldest, most distant galaxy and it started me wondering what the limits are. Presumably you can do better with a bigger telescope and ...
Roger Wood's user avatar
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8 votes
0 answers
120 views

How long would it take to first detect a new object in the night sky given its apparent magnitude?

If an object as bright as the star Polaris (Apparent Magnitude +1.8) showed up in the night sky, it would be detected almost instantly by stargazers. If an object as bright as Pluto (Apparent ...
Connor Garcia's user avatar
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7 votes
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Have there been successful attempts at spotting Neptune with the naked eye?

As pointed out here, the limit of naked eye visibility for people with extremely good night vision is about magnitude 8.5. Neptune at opposition is much brighter at magnitude 7.7, so it should be ...
Count Iblis's user avatar
7 votes
1 answer
1k views

As viewed from Mars, what are Jupiter's and Saturn's maximum brightness in apparent magnitude?

From Earth, Jupiter's maximum brightness is -2.94 and Saturn's is -0.24. But what about from Mars? They should be brighter, but by how much? There are equations at the obvious wiki entry but I'm not ...
DrZ214's user avatar
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7 votes
1 answer
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Is Uranus the farthest object in Solar System that you can see with naked eyes?

The following text is from this article: The fact is, even at its brightest, Uranus is still quite faint. It’s barely perceptible as a dim speck of light to the unaided eye, even under dark skies. At ...
Nilay Ghosh's user avatar
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7 votes
3 answers
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Apparent magnitude of Milky Way?

We have apparent magnitude of stars, planets, DSOs. What about the apparent magnitude of Milky Way? Can it be estimated?
Mathematicie's user avatar
6 votes
1 answer
232 views

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 ...
Geographos's user avatar
6 votes
2 answers
371 views

A what distance could we see the Sun?

How far away can we see the Sun with the naked eye? How far with an amateur telescope? And with the James Webb telescope? In my own calculations the Sun would appear magnitude 6 at 56 ly, magnitude 8 (...
HugoF's user avatar
  • 186
6 votes
3 answers
167 views

Are apparent magnitudes corrected for extinction at zenith?

For example, according to Google, the apparent magnitude of the sun is $-26.74^m$. Is this the apparent magnitude viewed through Earth's atmosphere when the object is at zenith? (Assuming most ...
Cheng's user avatar
  • 332
5 votes
2 answers
556 views

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....
Nau's user avatar
  • 153
5 votes
1 answer
269 views

How long does lunar opposition surge last? Are there measurements of the full Moon getting suddenly brighter?

Wikipedia's opposition surge is a short article and forwards shadow hiding and coherent backscattering as proposed mechanisms, but it doesn't really explain how much the brightness of the Moon ...
uhoh's user avatar
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5 votes
1 answer
161 views

Would one have to be more than halfway to the Oort Cloud for the Sun to appear as bright as the full moon?

Is this correct? If the Sun is 400,000 times brighter than the full moon am I correct in figuring that one would have to be about 632AU from the Sun for it to appear as bright as the full moon. If ...
Bob516's user avatar
  • 1,467
5 votes
1 answer
287 views

How much dimmer is a partial solar eclipse that goes from -26.71 to -25.89?

Based on what I found in Stellarium, for Vlissingen, Netherlands, on July 2, 1666 there was a partial eclipse with a change of apparent brightness -26.71 to -25.89. Is it valid to say based on the ...
Bob516's user avatar
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5 votes
1 answer
300 views

Surface Brightness Definition

I know the surface brightness is calculated by taking the apparent magnitude of an object and then divide by the size of the thing. But this is more of "observed" surface brightness, how do ...
JOAQUÍN HERNÁNDEZ's user avatar
5 votes
1 answer
2k views

How to convert between AB and Vega magnitudes?

This might be a bit silly, but I'm really struggling with a conversion. I have apparent AB magnitudes: $$m_{AB} = -2.5 \log_{10}(f_\nu [\mu Jy]) + 25$$ that I would like to convert to Vega magnitudes, ...
theWrongAlice's user avatar
5 votes
1 answer
237 views

What is the apparent magnitude of the faintest stars visible during a full moon?

Assuming the viewer is far from any light pollution, it is a cloudless night, and humidity is very low. What is the faintest apparent magnitude of stars visible to the naked eye during a full moon (...
Bob516's user avatar
  • 1,467
4 votes
1 answer
679 views

Total apparent magnitude of eclipsing binary system

This is a question from the 2016 USAAAO national exam, for which no solutions are given: An eclipsing binary system has a magnitude $m_p$ = 14.2 during the primary transit and $m_s$ = 13.7 during ...
Alistair's user avatar
4 votes
1 answer
165 views

Why is there "modulus" word in the "distance modulus" term?

The difference of apparent (m) and absolute (M) magnitudes of an object is called "distance modulus", which is related to the distance $d$ to the object in parsecs with equation $$m - M = 5 \log \Big(...
Evgenii's user avatar
  • 185
4 votes
2 answers
1k views

How bright are geostationary satellites due to reflected sunlight?

We are all familiar with seeing low-Earth orbit satellites scooting across the sky in a couple of minutes. Many of them are bright and readily identifiable with the naked eye. Geostationary satellites ...
ProfRob's user avatar
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4 votes
1 answer
89 views

Comparing different magnitudes. Is this statement correct?

I have two methods which allow for a detection of a signal that is at most of magnitude x. If method 2 can detect signal that are half a magnitude larger, i.e. fainter, let's say x.5 mag, is it ...
Philipp's user avatar
  • 41
4 votes
2 answers
384 views

Galactic mass estimation from apparent magnitude and distance

Can we estimate the order of the total mass of any galaxy from the apparent magnitude and its distance to us? Just like \begin{equation} M_{galaxy}=c\times 10^{8}M_{\odot }, \end{equation} where $c$ ...
Haliki's user avatar
  • 41
4 votes
1 answer
140 views

What is the biggest magnitude (faintest light possible) seen by JWST?

I'm doing some digging around ultra-diffused galaxies and would like to know what is the faintest visible light (biggest apparent magnitude) JWST can see. I have not been able to find it online. Thank ...
Camila Pazmino's user avatar
4 votes
1 answer
408 views

How bright could Gliese 710 appear in 1.35 million years?

I read this article on Gliese 710 that stated it would come within about 1.1 ly (+/- 0.577 ly) of earth in 1.35 million years. Wikipedia states it would have an apparent magnitude of 0.5, and the ...
joseph.hainline's user avatar
3 votes
2 answers
604 views

What is the planet relative to earth that shows the greatest change in apparent brightness?

What is the planet relative to earth that shows the greatest change in apparent brightness? I think the answer is Mars, and a quick google search reveals it is Mars. I have my reasoning here, but I ...
K Split X's user avatar
  • 1,069
3 votes
2 answers
2k views

Sun's apparent magnitude at 2.5 AU?

Imagine an astronaut standing on an asteroid 2.5 A.U. distant from the Sun. He is gazing, naked-eye, towards the Sun. What is the apparent magnitude of the Sun at that distance, and is that bright ...
catsteevens's user avatar
3 votes
1 answer
185 views

Snowball Earth brightness

The Earth likely froze over almost completely about 700 million years ago. This increased its albedo significantly, and I wonder if that would have a considerable effect on its apparent magnitude from ...
Simon Korneev's user avatar
3 votes
1 answer
2k views

What is the "lunar irradiance" received by the Earth from the full Moon?

The solar irradiance received by the Earth is 1361 $W/m^2$. What is the lunar irradiance received by Earth from the full Moon in the same units? My first thought was to work it out via apparent ...
ChristieToWin's user avatar
3 votes
2 answers
198 views

Graph of apparent magnitude of Mars through time from around 2000 to present?

I tried to search online but failed to find a graph of the apparent magnitude of Mars over time from 2000 to present. From Wikipedia: Mars made its closest approach to Earth and maximum apparent ...
HaoQi Li's user avatar
3 votes
2 answers
301 views

Best way to simulate star sizes to scale in celestial sphere

Using the Hipparcos catalogue, I am trying to create a celestial sphere. As all the stars are a fixed distance from the centre of this sphere, the only way to differentiate the distances and magnitude ...
SidS's user avatar
  • 225
3 votes
2 answers
110 views

Can we measure comets in a similar way to exoplanets?

A 2km comet at 40AU's can dim a sun sized star at 100 light years by 3%, and a 10km comet can cause an eclipse (is that right?) So would 2,3,10 km objects be easy to measure via star dimming if we had ...
bandybabboon's user avatar
  • 4,252
3 votes
1 answer
473 views

How is the magnitude of a star measured?

How does one measure the brightness of a star?, I did not find anything on the internet.
Antp's user avatar
  • 177
3 votes
2 answers
1k views

How to compute a Flux through a filter using SYNPHOT in Python

I am in the process of building an exposure time calculator to help nail down the exposure times I need for different targets in my observatory. In amateur astronomy imaging, we use a filter called ...
Adrian's user avatar
  • 116
3 votes
1 answer
502 views

Approximate spectral type and luminosity given apparent magnitude and distance

I am looking at the data acquired from the Gaia DR2 survey. I found that most of the stars had their distance and apparent magnitude catalogued, but not their spectral type and luminosity class. Is ...
WarpPrime's user avatar
  • 6,653
3 votes
1 answer
706 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 ...
Gimcrack's user avatar
  • 179
3 votes
1 answer
170 views

How would a flat mirror on the Moon reflect sunlight

I was solving a task that said (paraphrasing): There is a flat mirror on the Moon, whose reflection coefficient is 100%, and observers on the Earth observe it as a star whose apparent magnitude is $...
Tosic's user avatar
  • 1,681
3 votes
1 answer
88 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 ...
user267545's user avatar