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Frowny face in the sky
By adamg on Wed, 12/03/2008 - 11:25am
Sushieque took this cool photo of the moon, Jupiter and Venus on Monday from a Back Bay rooftop. Hey, which one is Jupiter and which is Venus?
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Comments
WAG
I bet the lower (larger, brighter) one is Jupiter.
brighter planet
All the folks I talked to at the Honan Library on Monday said that the brighter planet is Venus.
The hotter one
That's Venus. :-p
Which is which
Venus is the lower planet in this picture. Jupiter is the planet to the upper right closer to the scaffolding.
Venus is brighter to us because it is closer. Jupiter is so visible even though it is so much further away because it is so large. What's really cool about this planetary and lunar conjunction is that Venus is actually on the "inside" of us, being closer to the Sun and Jupiter is outside of our orbit. The maximum angle Venus can get from the Sun is 46 degrees giving us only, at most, about 3 hours before or after sunrise/sunset to see it bright at night like this. So, for it to be hanging out in the night sky at all is not always possible. To then have it hanging out where Jupiter and the Moon are passing at the same time is just really cool.
It's not Jupiter, it's
It's not Jupiter, it's Saturn.
Wrong
That is what you are.
You're talking out
Uranus
That's got a ring to it!
Then again, Neptune and even uranus have rings too!
My 5th grader just studied planets ... when his brother was in the same classroom two years ago, he said that the teacher told them to "get all the Uranus jokes out now so we can put them away". So my boy told this joke:
What do the Starship Enterprise and Charmin have in common?
They both go rings around Uranus wiping up klingons.
Fascinating
My four-year-old pointed these out to me as I picked him up at day care yesterday, and he informed me they were both planets, not stars. I figured the lower one was Venus, but wasn't sure what the higher one was. Thanks.
Which?
Find out at a local website.
It was in the Globe too.
Venus is the lower, brighter planet
Venus is the lower, brighter planet in the image, at apparent magnitude -4.2.
Jupiter is the upper planet at apparent magnitude -2.0 -- hard to tell from that image, but around seven times fainter than Venus.
-Your resident astronomer
See also images at Harvard-Smithsonian Center for Astrophysics website.
Well, just to calm the fears
Well, just to calm the fears of any UHers who think they may be going blind, it should be pointed out that apparent magnitude is a measure of an object's luminosity - the amount of energy in the visible spectrum reaching Earth. As Michael said, there's about 7 times as many visible-light photons reaching us from Venus as Jupiter.
But our eyes and brain respond to near-point sources of light (like stars and planets) in a non-linear way. So when you're out in the yard staring up at the sky, Venus only "looks" about twice as bright as Jupiter.
(and btw, although you need a telescope to see it, Pluto is also sitting a bit to the right (west) of Jupiter right now, so you can claim to be looking at three planets as you freeze your tuchus off).
Dopey
You'll be looking at 2 planets and a dwarf (or minor) planet.
My Very Educated Mother Just Served Us Nectarines.
Why any very educated mother these days would serve up nine pizzas is beyond me. This country is fat enough as it is and Pluto lost its planet status.
Apparent magnitude is flux, not luminosity
@ Jeff F:
Almost, but not quite. Apparent magnitude is how bright an object appears to us, not how intrinsically bright (= luminosity) it is. The object's luminosity is represented by the absolute magnitude, not the apparent magnitude.
For example, an extremely luminous star may be located in a galaxy far, far away from us -- and hence it appears faint to us.
Your point of the non-linearity of our eyes is another topic altogether... and I won't claim any expertise in biology.
astronomy pissing war! (or not)
Fair enough - apparent magnitude is a function of both apparent luminosity and distance. I was already wonking out on astronomy stuff and didn't want to get into (even more) anal-retentive descriptions of Watts per parsec, etc.
My point was that objects with significantly different brightnesses appear much less so to our human senses. It's something I have to explain fairly often when doing naked-eye astronomy with folks. For instance, most people find it hard to believe that staring at the moon even briefly can actually ruin your night vision for a while - I mean, sure it's bright, but it's nothing compared to the sun - or even a typical lightbulb, right? But a full moon is literally more than a million times brighter than many of the stars you can see in the night sky around Boston.
Phew!
I was going to say, if that big crescent-shaped one is Jupiter, boy are we in trouble.