by Ann » Sun Apr 05, 2020 6:45 am
De58te wrote: ↑Sat Apr 04, 2020 11:20 pm
Never mind how much brighter Venus is to Alcyone. I think it would be more interesting how much brighter the Sun is to Alcyone if the Sun was the same distance away as the Pleiades, or vice versa, how bright would Alcyone be if it was in the place of the Sun, 1 Astronomical Unit away?
According to
Wikipedia, Alcyone is 2030 times brighter than the Sun. But Wikipedia also claims that Alcyone is 2,400 times brighter than the Sun.
The problem is that different sources disagree on how far away Alcyone is (the farther away it is, the intrinsically brighter it must be). But we must also define how we measure the brightness of stars.
The Sun's output of energy peaks in the visible part of the spectrum.
Hot stars peak in the ultraviolet part of the spectrum,
while cool stars peak in the infrared part of it.
Alcyone is undoubtedly much brighter than the Sun even in the visible part of the spectrum. But Alcyone is also a hot star, with a temperature of about 13,000 K versus some 5,800 K for the Sun. My guess is that Alcyone is about 1,000 times brighter than the Sun in visible light. But the total (bolometric) brightness of Alcyone is certainly more than 2,000 times that of the Sun, because Alcyone emits so much ultraviolet light.
Ann
[quote=De58te post_id=300978 time=1586042454 user_id=141631]
Never mind how much brighter Venus is to Alcyone. I think it would be more interesting how much brighter the Sun is to Alcyone if the Sun was the same distance away as the Pleiades, or vice versa, how bright would Alcyone be if it was in the place of the Sun, 1 Astronomical Unit away?
[/quote]
According to [url=https://en.wikipedia.org/wiki/Alcyone_(star)]Wikipedia[/url], Alcyone is 2030 times brighter than the Sun. But Wikipedia also claims that Alcyone is 2,400 times brighter than the Sun.
The problem is that different sources disagree on how far away Alcyone is (the farther away it is, the intrinsically brighter it must be). But we must also define how we measure the brightness of stars.
[float=left][attachment=1]Solar spectrum.png[/attachment][c][size=85]The Sun's output of energy peaks in the visible part of the spectrum.[/size][/c][/float] [float=right][attachment=0]Spectrum for different kinds of stars.png[/attachment][c][size=85]Hot stars peak in the ultraviolet part of the spectrum,
while cool stars peak in the infrared part of it.[/size][/c][/float]
Alcyone is undoubtedly much brighter than the Sun even in the visible part of the spectrum. But Alcyone is also a hot star, with a temperature of about 13,000 K versus some 5,800 K for the Sun. My guess is that Alcyone is about 1,000 times brighter than the Sun in visible light. But the total (bolometric) brightness of Alcyone is certainly more than 2,000 times that of the Sun, because Alcyone emits so much ultraviolet light.
Ann