Questions tagged [apparent-magnitude]
Questions regarding how bright an object appears to be.
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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—...
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1answer
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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 ...
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2answers
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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?
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2answers
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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 ...
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1answer
55 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 ...
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1answer
97 views
What is Jupiter's apparent magnitude as watched from Uranus?
Saturn's apparent magnitude as watched from Uranus is +3.228. Jupiter's orbit is further in towards the sun. Can we expect its apparent magnitude to be greater than Saturn's, or is it in fact lesser? (...
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1answer
31 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)?
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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 ...
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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 ...
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1answer
78 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?
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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 ...
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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 ...
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1answer
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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 $...
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2answers
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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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Estimate the shape of an object based on flux curve
Is there an aproximation to know the shape of a dust cloud,etc based on the magnitude/flux curves of stars they transit? Example, can I know if the shape is (at least in 2 dimensions) elliptical, ...
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1answer
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Apparent Magnitude of First quarter Moon [closed]
Given
Apparent magnitude of moon is -12.5.
Distance of moon and earth is 384400 km.
Diameter of Moon is 31 arcmin.
Phase of moon is 0.5.
Find the apparent magnitude of first quarter moon.
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vote
1answer
35 views
Why must all magnitude systems have a reference point?
Let $f_*$ and $f_0$ be the observed flux of a star and a reference flux in a particular spectral band, and let $m_*$ and $m_0$ be their respective apparent magnitudes. Then the star's magnitude is ...
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1answer
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Has lunar opposition surge ever been observed from Earth? From Earth orbit?
This thorough answer to How long does lunar opposition surge last? Are there measurements of the full Moon getting suddenly brighter? details observations of lunar opposition surge by the Clementine ...
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1answer
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When calculating absolute magnitudes of distant objects, do you use the light-travel distance or the comoving distance?
I want to calculate the absolute magnitude of GN-z11. Its light-travel distance is 13.4 billion ly (4.1 Gpc), its comoving distance is 32 billion ly (9.8 Gpc), and its apparent magnitude is $25.8$. ...
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1answer
165 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 ...
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1answer
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Limiting magnitudes for different telescopes
I live in an extremely light polluted place. On a new moon night, magnitude 3.5 stars are at the limit of naked eye visiblity on clear nights, and the Orion nebula is visible as a smudge through my ...
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1answer
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How to compute for Distance Modulus' uncertainty/ies?
This is rather a short question. As we know of;
Distance Modulus (DM) $\mu = 5 \log d - 5$
If $d = 168_{-14.9}^{+27.5}$ pc ($3\sigma$ value), how can I possibly compute for $\mu$'s uncertainty?
P.S. ...
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1answer
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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. ...
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How to calculate the luminosity of a quasar?
Is there a relation between the distance ($d$) and the apparent bolometric magnitude ($m_{bol}$) of a quasar and its luminosity ($L$) in watt? If so, what is that relation?
Thanks in advance!
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1answer
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How was Mars' very noticeable change in apparent magnitude explained by the Geocentric Model?
In the geocentric model, the Sun, the Moon, and the 5 naked-eye planets (Mercury, Venus, Mars, Jupiter, Saturn) all orbited Earth.
Today we know that the planets orbit the Sun, and thus they come ...
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1answer
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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 ...
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1answer
139 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, ...
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2answers
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Formula to calculate the apparent magnitude of Earth from arbitrary distances
I would like to calculate the apparent magnitude of Earth from various distances, say from the Voyager probe at this moment or from various stars in the sky. I know there must be a formula that I can ...
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1answer
107 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 ...
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votes
1answer
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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 ...
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How many streetlights should we turn off to decrease light on the ground by about 2.512 times?
I am looking for some guidance for a back-of-the-envelope-calculation to show that turning off street lights can make a difference for light pollution in the style of a Fermi problem.
My first step is ...
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1answer
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Is it possible to calculate a star's apparent magnitude in another photometric band knowing its visual magnitude?
Or, in other words, is it possible to know a star's luminosity in a certain photometric band?
Proxima Centauri's Wikipedia page provides the apparent magntiude in each UBVRIJHK band (getting ...
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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 ...
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2answers
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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
...
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1answer
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A double star consists of two stars of equal brightness at equal distance from the Earth. What is the apparent magnitude of the combined object?
The magnitude of each star in the V-band is mV= 8.34. If these stars are so close together that they appear as one object, what is the apparent magnitude of the combined object?
I just want someone to ...
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1answer
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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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Apparent magnitude of a spherical body with specular, rather than diffuse reflectivity? How bright were Sputnik 1 and Vanguard 2?
How bright are geostationary satellites due to reflected sunlight? and Did Sputnik 1 tell us more than “beep”? What science was improved by information gained from its orbiting the Earth? now have me ...
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2answers
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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 ...
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1answer
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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 ...
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3answers
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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?
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1answer
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What is wrong with my calculations of Jupiter's apparent magnitude?
I was searching for a formula to calculate the apparent magnitude of a planet knowing its physical characteristics and stumbled upon this answer.
The final formula given is:
$$m_{planet} = V_{planet} +...
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1answer
74 views
apparent and absolute magnitude of meteors and space debris
I have a question regarding the apparent and absolute magnitude of space debris objects or meteors reentering the earth's atmosphere. I already understand the difference between apparent and absolute ...
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2answers
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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 ...
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1answer
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How is Comet SWAN C/2020 F8 doing? Will it become easily visible by eye?
The New York Times article How to See Comet SWAN in Night Skies says:
Astronomers have their fingers crossed that the comet will keep brightening in the coming weeks as it heads north, passing 52 ...
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1answer
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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 ...
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1answer
291 views
Distance to star using color index
I'm doing the following question:
A star is observed with UBV magnitudes $m_u = 16.31$, $m_b = 14.52$,
$m_v = 13.76$. Spectral analysis gives $M_{bol} = 7.31$, $BC = -1.02$, $(U − B)_0 = 1.222$. ...
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1answer
280 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 ...
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0answers
55 views
Minimum apparent magnitude of galaxy
currently I'm working on astronomy problem which deals with finding redshift of a galaxy. But the first part asks to derermine apparent magnitude of a galaxy:
Find what should be the minimum ...
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1answer
37 views
Extinction and reddening dataset
Where can I find a dataset containing the interstellar reddening and extinction values for all globular clusters, preferably in the HST/WFC3 system.
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1answer
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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(...
