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Questions tagged [apparent-magnitude]

Questions regarding how bright an object appears to be.

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Is there a specific constant name for the fifth root of 100?

I understand that each scale you go up on the absolute magnitude scale, the luminosity decreases by the fifth root of 100, or around 2.512. Is there a name for the constant 2.512, or not. Also, is the ...
Astrovis's user avatar
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11 votes
1 answer
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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
2 votes
2 answers
208 views

Are there any bright *main-sequence* K-type stars in the night sky? Or are all of them giants?

It's well known that stars of a higher (i.e. hotter) spectral class have higher luminosities, due to their larger radii and hotter temperatures. Stars of spectral types O through G have no problem ...
user267545's user avatar
4 votes
1 answer
198 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
3 votes
1 answer
95 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
0 votes
1 answer
211 views

Betelgeuse, placing light bulb so that its apparent brightness is similar to that of Betelgeuse; wavelength where it shines brightest?

The giant star Betelgeuse will develop into a supernova in the future. After this event, his remains will be far too dark to be observed from Earth. In order to maintain the view of the starry sky, it ...
mathgirl752's user avatar
2 votes
1 answer
43 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 ...
Vincent ISOZ's user avatar
1 vote
2 answers
148 views

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 ...
DrZ214's user avatar
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16 views

What is a good resource for finding accurate apparent magnitudes stars in different filters?

I am unable to find this information online, does anyone know of a database, book, or website that contains all of the B-band, V-band, I-band etc.... apparent magnitudes for each star? Thanks for any ...
Thanos's user avatar
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1 vote
1 answer
262 views

Is there a way to calculate a star's luminosity from its apparent magnitude?

I was wondering if there's a way to calculate a star's luminosity from apparent magnitude data.
Nam's user avatar
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0 votes
1 answer
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3rd brightest ever object in the sky

What’s the 3rd brightest ever recorded object in the sky? For example Venus is normally the 3rd brightest object in the sky. However there have been the occasional comet or Supernova that have ...
blademan9999's user avatar
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0 answers
92 views

Which is brighter, starlight or the CMB?

Which do we receive more energy from, the CMB or starlight? (Not including the sun of course.)
blademan9999's user avatar
1 vote
2 answers
741 views

How to calculate the apparent magnitude of sun?

I know the apparent magnitude of sun is -26.74, but I wonder how to get this value if we don't know the absolute magnitude? Thanks!
Lance798's user avatar
0 votes
2 answers
82 views

Comparison of apparent magnitude (Apmag)

How can I compare the apparent magnitude of one object to another in percentages, e.g. the positive apmag of a dim star versus the negative apmag of the Sun? EDIT: I'm an absolute amateur with ...
Kazon's user avatar
  • 587
28 votes
4 answers
7k views

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
6 votes
1 answer
277 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
1 vote
2 answers
157 views

What stars are brighter than any more distant stars?

Which stars have a greater apparent brightness (lower apparent magnitude) than any stars that are further away? (i.e. the only stars that appear brighter than them are also closer)
blademan9999's user avatar
8 votes
1 answer
239 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
2 votes
0 answers
35 views

Which value of the apparent magnitude do I use from a Supernova light curve

I am trying to get the distance modulus from a light curve of a supernova and obviously the apparent magnitude changes with time. Not only that but there are so many filters with different mags. So my ...
Abdullah's user avatar
2 votes
1 answer
2k views

calculate the absolute and apparent magnitude for a binary star system

I'm used to use this formula to find the apparent magnitude of a star $$m_1 - m_2 = -2.5 log(\frac{f_1}{f_2})$$ If both star are at the same distance from us and their luminosity is the same, does it ...
InvisibleParticle's user avatar
2 votes
1 answer
59 views

What stars are brighter then any star nearer to the south celestial pole [closed]

What stars are brighter (apparent magnitude) then any star nearer to the south celestial pole? I know that there’s no bright star within a few degrees of the south celestial pole.
blademan9999's user avatar
6 votes
2 answers
417 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
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5 votes
1 answer
340 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
7 votes
1 answer
2k views

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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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
1 vote
0 answers
76 views

How bright does Venus appear from the moon if it replaced Earth?

If you were standing on the moon, Earth will appear mostly around -17.7 at maximum brightness. However, since Venus has a higher albedo than Earth, Venus would be brighter. What would be Venus's ...
InfinitySwordofDiamond's user avatar
1 vote
0 answers
137 views

What is the brightness and size of Jupiter from the Galilean moons, the closest moon, and the farthest moon?

From the Moon, Earth would appear 4 times larger than the Moon seen from Earth, and the magnitude of a "full earth" is around -17. However, Jupiter from the Galilean moons appear much larger ...
InfinitySwordofDiamond's user avatar
6 votes
3 answers
180 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
  • 342
3 votes
1 answer
331 views

absolute magnitude of an asteroid

I've done some research and found that one could derive the absolute magnitude $H$ of an asteroid in the following way. $H$ is the brightness of the asteroid, observed on Earth, if the asteroid were ...
mysterium's user avatar
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1 vote
0 answers
153 views

How to calculate absolute magnitude of planets?

Knowing: Star's radius $r_s$ , luminosity $L_s$, and absolute magnitude $V$ Planet's radius $r_p$ , albedo $a$ , and distance $d_s$ How can you calculate the absolute magnitude of a planet in a ...
E.UCIT's user avatar
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1 vote
0 answers
77 views

How do stellar magnitude and integrated magnitudes compare, perceptually?

(P.S. this is naked eyed) Magnitudes are easily defined for point-like objects i.e. stars. However, for extended objects, the "magnitudes" quoted are actually integrated magnitudes. For ...
Cheng's user avatar
  • 342
2 votes
0 answers
33 views

Calculating absolute error in apparent magnitude of a star [duplicate]

I know that the apparent magnitude $m$ of a star is related to its intensity by Pogson's law: $m = −2.5 log_{10} I$. And I also know that the absolute error is defined as follows: Let $\hat{𝑥}$ be an ...
Lujan's user avatar
  • 153
1 vote
1 answer
71 views

Computation of magnitude of the secondary

How to approximately compute the magnitude of the secondary in a binary when I know the magnitude of the primary, masses, radii, and approximate luminosities for both of them, please? Thank you very ...
Anna-Kat's user avatar
  • 505
1 vote
0 answers
27 views

V magnitude of binary components

Which catalog provides visible magnitudes of binary components, please? How to find it, for instance, in VizieR, please? I have a list of binaries.
Anna-Kat's user avatar
  • 505
2 votes
2 answers
238 views

What would be the highest possible naked-eye apparent magnitude?

What would be the highest possible magnitude $m$ of some star that could be viewed with a naked-eye? I am acquainted with this question, but mine is about the ideal conditions. In order to achieve ...
User123's user avatar
  • 2,879
2 votes
1 answer
1k views

What is the smallest (brightest) magnitude that the JWST can safely observe?

Similar to Can JWST be damaged by looking at a bright star?. I'd like to know the brightest magnitude that the James Webb Space Telescope can safely observe without damaging any of its instruments. ...
WarpPrime's user avatar
  • 6,683
2 votes
0 answers
187 views

Can JWST be damaged by looking at a bright star?

Can JWST be damaged by looking at a bright star? The Sun as well as particularily bright solar-system objects like Jupiter, Venus or the Moon not meant with this question.
sno's user avatar
  • 1,455
2 votes
1 answer
350 views

What is the apparent magnitude of the Milky Way from the viewpoint of the Large Magellanic Cloud?

Wikipedia contains the essentially unsourced claim that From a viewpoint in the LMC, the Milky Way's total apparent magnitude would be −2.0—over 14 times brighter than the LMC appears to us on Earth—...
rhombidodecahedron's user avatar
2 votes
1 answer
170 views

Brown Dwarf Sun: How dim can a star be in the visible spectrum and still provide enough heat for a planet to be habitable?

After reading this question on wordbuilding. I saw that a brown dwarf emits most of its energy in the infrared which made me wonder: How bright would such a star appear from it's exoplanet in the ...
SurpriseDog's user avatar
2 votes
2 answers
133 views

Finding stellar radii

Is apparent magnitude of star, distance(in pc) and effective temperature enough to calculate its stellar radii or we need some extra information?
Particle king's user avatar
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
0 votes
1 answer
69 views

What is going on with comet C/2021 A1 Leonard? Is it going to be bright this weekend or not?

I have to plan an excursion to try to find clear evening skies to try to see if we can spot comet C/2021 A1 Leonard about 10 to 15° above the ocean in the Southwest after sunset this weekend. I'm ...
uhoh's user avatar
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-4 votes
2 answers
207 views

What is Jupiter's apparent magnitude as watched from Uranus?

Saturn's apparent magnitude from Uranus is +3.228. Jupiter orbits closer to the sun than Saturn. Can we therefore expect Jupiter’s apparent magnitude from Uranus to be dimmer than Saturn's, or is it ...
Constantthin's user avatar
0 votes
1 answer
46 views

How to find magnitude of one galaxy being a hypothetical observer in the other?

The given apparent magnitude of M31 galaxy is 3.4$^m$, M33 - 5.7$^m$. I wonder how can I calculate the apparent magnitude of one of them (ex. M33) if I imagine myself being in the other (ex. M31)?
ALiCe P.'s user avatar
  • 1,017
-2 votes
1 answer
402 views

What is Saturn’s apparent magnitude at its brightest when viewed from Uranus?

Considering that the apparent magnitude scale is an inverted scale; what is the lowest apparent magnitude of Saturn that can be seen from Uranus. We are of course talking about when Saturn is viewed ...
Constantthin's user avatar
-5 votes
2 answers
242 views

What is 5 in 5log10 the value of?

I know what 2.5 stand for in $2.5 \log_{10}$, but what does the number 5 in $5\log_{10}$ stand for and what application does it have. Thus, why is the number a five and not a four, or a three, or ...
Constantthin's user avatar
0 votes
1 answer
110 views

Is subtracting one apparent magnitude from another ever practical?

Does a circumstance exist for subtracting one apparent magnitude from another to reach a solution to a problem? Is it ever suitable to do so?
Constantthin's user avatar
0 votes
1 answer
312 views

Why does apparent magnitudes get increased fourfold when distances get halved, instead of simply getting doubled?

This website explains: The apparent brightness of a star is proportional to 1 divided by its distance squared. That is, if you took a star and moved it twice as far away, it would appear 1/4 as ...
Constantthin'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
2 votes
1 answer
706 views

E(B-V) , the color excess between B and V bands, for galaxy at redshift 0

Following Mo et al. 2010 (page 479), the quantity $E(B-V)$, called the color excess between B and V bands, is equal to: $$E(B-V) = A_B - A_V = (B - V) - (B - V)_0 = (m_B - m_V) - (M_B- M_V)$$ where $...
fslack's user avatar
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