Comments on: BAFact Math: The Sun is mind-crushingly brighter than the faintest object ever seen. Seriously.

By: Matt B.

Matt B. — Fri, 31 Aug 2012 22:37:47 +0000

Or we could take our view of the Sun from Venus, getting us another factor of 2.

By: Itskurtins

Itskurtins — Fri, 31 Aug 2012 17:37:52 +0000

Looking at a recent review in Science Avishay Gal-Yam, considers Super Luminous Super Nova as thoes with magnitudes greater then -21. These object have been found in wide field surveys and are not yet used for estimation of cosmological age though they may find some use their when their features are mapped out.

By: Messier Tidy Upper

Messier Tidy Upper — Fri, 31 Aug 2012 15:45:35 +0000

No link to here :

http://blogs.discovermagazine.com/badastronomy/2012/08/28/bafact-math-the-sun-is-12-trillion-times-brighter-than-the-faintest-star-you-can-see/

there BA or did I just miss it?

BTW. Went back and checked and seems the faintest star visible to the unaided human eye is probably the 61 Cygni duo (K5 & K7 V) ahead of (K4.5 V) Epsilon Indi :

http://stars.astro.illinois.edu/sow/61cyg.html

although one red dwarf, EV Lacertae, the roaring red dwarf :

http://blogs.discovermagazine.com/badastronomy/2008/05/19/the-red-dwarf-that-roared/

can flare so luminously that it could apparently become visible briefly if you know just where to look for it and are super-fortunate enough to catch it at the right momement! 8)

By: Arik Rice

Arik Rice — Thu, 30 Aug 2012 12:14:36 +0000

For fun, I quickly calculated what magnitude an object would be if it had the apparent brightness of one mole of Suns. The answer was illuminating (har har): magnitude -86.1.

By: Neil Haggath

Neil Haggath — Thu, 30 Aug 2012 12:07:20 +0000

Re Avogadro’s Number: “and a lot of (geeky) folks have heard of it”.
And everyone who believes in homeopathy should be made to have heard of it!

By: Nigel Depledge

Nigel Depledge — Thu, 30 Aug 2012 11:59:04 +0000

@ Jeff Eriksen (11) -
It’s because lunar regolith reflects light preferentially back in the direction from whence it came.

You can see this effect in many of the Apollo photographs – there’s a brighter patch of regolith that lines up with the antisolar point.

By: Nigel Depledge

Nigel Depledge — Thu, 30 Aug 2012 11:55:05 +0000

Tara Li (6) said:

Couldn’t we get that fainter object detection just by extending the exposure time a while?

For that matter, an object emitting light emits a finite number of photons. At some distance, it should become statistically sufficiently unlikely that a photon would *ever* hit the detector, that you could say it is invisible, no matter how good a detector you use – you couldn’t even get a one-photon “image” of it.

This does not feel right.

It seems to me that, as long as there is no constraint on the direction in which photons are emitted, then sooner or later, one should hit our detector.

I guess it is theoretically conceivable to have an object that is so distant that we’d have to wait longer than the lifetime of the universe to get a photon recorded, but that distance would be much farther away than the limit of the observable universe that arises through the expansion of the universe.

By: Atheist Panda

Atheist Panda — Thu, 30 Aug 2012 11:53:32 +0000

@11 Jeff: Interesting… Made me do some investigation, and I found this, http://www.asterism.org/tutorials/tut26-1.htm, which seems to explain why, when the incident light from the Sun is at a very shallow angle, the cratered surface of the Moon casts many more shadows, reducing the apparent brightness. AP

By: Nigel Depledge

Nigel Depledge — Thu, 30 Aug 2012 11:45:14 +0000

The BA said:

I know, it’s an odd unit, but it’s handy in chemistry, and a lot of (geeky) folks have heard of it.

Wait, what do you mean “odd”?

The mole is a fundamental SI unit.

Relative molecular mass (molecular weight if you’re stil in the 19th century) is defined in grams per mole.

Concentration is defined in moles per dm^3 or in moles per kg (these units are casually referred to as molar and molal, but these casual terms are not SI).

The mole is as fundamental a unit as the Coulomb, and would you call that odd?

By: Jeff Eriksen

Jeff Eriksen — Thu, 30 Aug 2012 03:59:45 +0000

I do not know how else to contact you Phil, and this BAFact prompted to me to remember something I heard recently at a star party, that the quarter Moon is only 9% of the brightness of the Full Moon (which is twice the visible area of the quarter Moon). Could you please explain this to us sometime in a future post? I know it is mainly because of the angle of incidence of the Sun’s light on the Moon combined with the angle of incidence on the observer on Earth, but why 9% instead of say 25%?