<p>The (boldly titled) <a href="https://www.omnicalculator.com/physics/luminosity" rel="nofollow noreferrer">omnicalculator</a> can do luminosity calculations.  At 500 trillion solar luminosities, this object would have an absolute magnitude of -32, and if placed at 26000 light years distance, it would have an apparent magnitude of -17.5  That is much brighter than the moon (about 100 times brighter) but not nearly as bright as the sun (The sun would be 10000 times brighter)</p>
<p>It would, however be no larger in the sky than Venus. So it might be &quot;fair&quot; to compare it to bright stars and planets.  It would appear to be a &quot;star&quot; that is about 60000 times brighter than Venus.  Or about 4000000 times brighter than Sirus.</p>

CC BY-SA 4.0
2024-02-21T00:12:38.190Z
So it'll be visible during the day, and quite obvious too, given it's 100 times brighter than the Moon! Wow.
Ahmed Tawfik
CC BY-SA 4.0
2024-02-21T04:58:10.687Z
Venus, Mars, and Jupiter are already bright enough to sometimes be seen during the day sometimes.  And possibly - repeat possibly - it might sometimes be possible to see the very brightest stars like Sirius in bright daylight- they are certainly visible at twilight.      So if an object 500 trillion times as luminous as the Sun at the center of the Galaxy appeared to be tens of thousands of times as bright as Sirius or Venus, that would be really, really, bright.
M. A. Golding
CC BY-SA 4.0
2024-02-21T12:22:31.453Z
@M.A.Golding Indeed! [Is it possible to do planet observation during the day?](https://astronomy.stackexchange.com/q/40362/7982) and [Can an average person see stars from the bottom of a well or through cardboard tubes? Definitive answer required!](https://astronomy.stackexchange.com/q/38504/7982) and in Aviation SE [At what altitude might a pilot be able to see at least the brightest stars during the day?](https://aviation.stackexchange.com/q/73024/14213)
uhoh
CC BY-SA 4.0
2024-02-21T12:36:08.523Z
@M.A.Golding All of the links that uhoh references seem to be with aids. I've personally never seen anything except the Moon during daytime unaided.
Ahmed Tawfik
CC BY-SA 4.0
2024-02-22T03:34:12.833Z
@Ahmed Tawfik   I find it easy to believe that you, a specific person, has never seen any astronomical objects in daylight with unaided vision.  I do not remember seeing any myself.  But others have.  https://earthsky.org/astronomy-essentials/space-objects-to-see-during-the-day-top-10-space-objects/
M. A. Golding
CC BY-SA 4.0
2024-02-20T21:53:52.673Z
2024-02-20T21:53:52.673Z
James K
<p>According to <a href="https://www.eso.org/public/news/eso2402/" rel="nofollow noreferrer">this article</a>, the quasar (black hole) named J0529-4351 is the most luminous object in the known universe, being:</p>
<blockquote>
<p>500 trillion times more luminous than the Sun</p>
</blockquote>
<p>To put it in terms easier to understand at a human level, how bright would the quasar be if it were within our galaxy? I'm considering that it is either in place of the current black hole in the galactic center of the Milky Way, or somewhere perhaps less shrouded by dust (if it matters).</p>

CC BY-SA 4.0
2024-02-20T19:11:48.973Z
FWIW, it has a mass of 17 billion solar masses, which means its Schwarzschild radius is ~46.5 light-hours. That's big, but [TON 618](https://en.wikipedia.org/wiki/TON_618) has more than double that mass.
PM 2Ring
CC BY-SA 4.0
2024-02-20T19:15:57.997Z
Are you just asking about the luminosity of the central object, i.e., that 7 light-year diameter accretion disk? Quasar tend to have [jets](https://en.wikipedia.org/wiki/Astrophysical_jet), which can span over a million light-years, which is larger than the Milky Way.
PM 2Ring
CC BY-SA 4.0
2024-02-20T20:10:13.117Z
Actually, small correction - the article you provided says that a lens galaxy magnified the quasar to *appear* to be 500 trillion L☉. It is thought to be "just" around 11 trillion naturally.
4NT4R3S
CC BY-SA 4.0
2024-02-20T21:36:37.517Z
@4NT4R3S I got confused by that as well, but it's not talking about J0529-4351 but rather another quasar.
Ahmed Tawfik
CC BY-SA 4.0
2024-02-20T21:37:44.597Z
@PM2Ring I'm just talking about the luminosity that they reference, whatever the source is. I'm not sure if it is known whether the luminosity is due to the jet or the accretion disk.
Ahmed Tawfik
CC BY-SA 4.0
2024-02-20T21:51:25.807Z
@AhmedTawfik, Oh, that's the previous recordholder. It really is half a quadrillion solar luminosities then...
4NT4R3S
<supermassive-black-hole><quasars><brightness>
How bright in the night sky would J0529-4351 (brightest quasar ever found) be if it were in our galaxy?
Ahmed Tawfik
# How bright in the night sky would J0529-4351 (brightest quasar ever found) be if it were in our galaxy?

(Asked by: username_0 on 2024-02-20)

According to [this article](https://www.eso.org/public/news/eso2402/), the quasar (black hole) named J0529-4351 is the most luminous object in the known universe, being:

> 500 trillion times more luminous than the Sun

To put it in terms easier to understand at a human level, how bright would the quasar be if it were within our galaxy? I'm considering that it is either in place of the current black hole in the galactic center of the Milky Way, or somewhere perhaps less shrouded by dust (if it matters).

**Tags:** supermassive-black-hole, quasars, brightness
> **Comments:**
> **username_1**: FWIW, it has a mass of 17 billion solar masses, which means its Schwarzschild radius is ~46.5 light-hours. That's big, but [TON 618](https://en.wikipedia.org/wiki/TON_618) has more than double that mass.  
> **username_1**: Are you just asking about the luminosity of the central object, i.e., that 7 light-year diameter accretion disk? Quasar tend to have [jets](https://en.wikipedia.org/wiki/Astrophysical_jet), which can span over a million light-years, which is larger than the Milky Way.  
> **username_2**: Actually, small correction - the article you provided says that a lens galaxy magnified the quasar to *appear* to be 500 trillion L☉. It is thought to be "just" around 11 trillion naturally.  
> **username_0**: @4NT4R3S I got confused by that as well, but it's not talking about J0529-4351 but rather another quasar.  
> **username_0**: @PM2Ring I'm just talking about the luminosity that they reference, whatever the source is. I'm not sure if it is known whether the luminosity is due to the jet or the accretion disk.  
> **username_2**: @AhmedTawfik, Oh, that's the previous recordholder. It really is half a quadrillion solar luminosities then...  

---

## 1 answers

### Answer by username_3 on 2024-02-20. Score: 3 | Accepted answer

The (boldly titled) [omnicalculator](https://www.omnicalculator.com/physics/luminosity) can do luminosity calculations. At 500 trillion solar luminosities, this object would have an absolute magnitude of -32, and if placed at 26000 light years distance, it would have an apparent magnitude of -17.5 That is much brighter than the moon (about 100 times brighter) but not nearly as bright as the sun (The sun would be 10000 times brighter)

It would, however be no larger in the sky than Venus. So it might be "fair" to compare it to bright stars and planets. It would appear to be a "star" that is about 60000 times brighter than Venus. Or about 4000000 times brighter than Sirus.

> **Comments:**
> **username_0**: So it'll be visible during the day, and quite obvious too, given it's 100 times brighter than the Moon! Wow.  
> **username_4**: Venus, Mars, and Jupiter are already bright enough to sometimes be seen during the day sometimes.  And possibly - repeat possibly - it might sometimes be possible to see the very brightest stars like Sirius in bright daylight- they are certainly visible at twilight.      So if an object 500 trillion times as luminous as the Sun at the center of the Galaxy appeared to be tens of thousands of times as bright as Sirius or Venus, that would be really, really, bright.  
> **username_5**: @M.A.Golding Indeed! [Is it possible to do planet observation during the day?](https://astronomy.stackexchange.com/q/40362/7982) and [Can an average person see stars from the bottom of a well or through cardboard tubes? Definitive answer required!](https://astronomy.stackexchange.com/q/38504/7982) and in Aviation SE [At what altitude might a pilot be able to see at least the brightest stars during the day?](https://aviation.stackexchange.com/q/73024/14213)  
> **username_0**: @M.A.Golding All of the links that uhoh references seem to be with aids. I've personally never seen anything except the Moon during daytime unaided.  
> **username_4**: @Ahmed Tawfik   I find it easy to believe that you, a specific person, has never seen any astronomical objects in daylight with unaided vision.  I do not remember seeing any myself.  But others have.  https://earthsky.org/astronomy-essentials/space-objects-to-see-during-the-day-top-10-space-objects/  

---

