Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Wed Sep 08, 2010 5:05 am
I love the Buffer Brown and Tighe image!
Ann
Ann
Starship Asterisk*
APOD and General Astronomy Discussion Forum
https://asterisk.apod.com/
Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
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Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Wed Sep 08, 2010 11:03 pm
Ok Dr. Jerry Bonnell - Now that you have asked and answered a question that you would have liked to have been asked but never was, could you please explain the answer that you gave?? I can not find anything anywhere that gets rid of a pant leg tugging feeling that i have about your answer.
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Mon Sep 13, 2010 3:10 pm
How many people do you think, like myself, read the APOD every single day?
Kind regards.
Kind regards.
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Mon Sep 13, 2010 3:35 pm
There is probably a difference betweenBobby Woods wrote:How many people do you think, like myself, read the APOD every single day?
the number of people who actually read the APOD and
the number of people who just look at the pictures
(much as with Playboy magazine).
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Mon Sep 13, 2010 4:28 pm
There have been 1275 views of this thread. 1275, what a great astronomical number! 1275, as in NGC 1275, the remarkable Perseus A galaxy.
This image was APOD on July 25, 2005, in case you are wondering!
Ann
This image was APOD on July 25, 2005, in case you are wondering!
Ann
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Mon Sep 13, 2010 8:37 pm
Ann, that was before my time. To me NGC 1275 looks like >The Attack of The Pinkish-Red thing!
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Mon Sep 13, 2010 10:20 pm
Why are there no green stars?
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Mon Sep 13, 2010 10:53 pm
The color of stars is mainly determined by their temperatures- they are approximately black body emitters, and the shape of a black body spectrum, combined with the responsivity of our eyes, means that there is no temperature that can produce green. There is a temperature where the peak wavelength is green (in fact, that's pretty close to our own Sun), but when mixed with all the other wavelengths, our eye sees something else. When you heat something up, from cold to hot it goes red-orange-yellow-white, with a hint of blue at the hottest end. Gas in the stellar envelope, or in the intervening space, can result in a shift of color, as can scattering and absorption by dust. But none of these mechanisms can really make a star look green.Curiosity wrote:Why are there no green stars?
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Mon Sep 13, 2010 11:24 pm
They keep all the "green" stars hidden behind cloaks of dust and gas so that the only stars you see are mature stars that have been aged properly and are no longer considered "green".Curiosity wrote:Why are there no green stars?
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Mon Sep 13, 2010 11:31 pm
Now I'm confused. Isn't the Moon made of well-aged green cheese? Are there different rules for stars and planetary satellites?bystander wrote:They keep all the "green" stars hidden behind cloaks of dust and gas so that the only stars you see are mature stars that have been aged properly and are no longer considered "green". :lol:
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Mon Sep 13, 2010 11:34 pm
In that case, are all the really "old" stars grey and hiding in the dust and stuff alsobystander wrote:They keep all the "green" stars hidden behind cloaks of dust and gas so that the only stars you see are mature stars that have been aged properly and are no longer considered "green".Curiosity wrote:Why are there no green stars?
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Tue Sep 14, 2010 12:25 am
But when separated from all the other wavelengths, our eye sees green:Chris Peterson wrote:There is a temperature where the peak wavelength is green (in fact, that's pretty close to our own Sun),Curiosity wrote:Why are there no green stars?
but when mixed with all the other wavelengths, our eye sees something else.
http://asterisk.apod.com/vie ... sh#p131453
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Tue Sep 14, 2010 12:48 am
Of course. For all the images we see on APOD, vastly more astronomical data is collected using spectroscopes, which do show precisely how much green is really there.neufer wrote:But when separated from all the other wavelengths, our eye sees green...
For that matter, you can view the stars using a green filter, and see which ones have lots of green and which have little.
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Tue Sep 14, 2010 1:53 am
Chris Peterson wrote:Of course.neufer wrote:A horse is a horse...
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Tue Sep 14, 2010 5:12 am
Same rules apply, the green cheese the moon is made of is ripe (mature) green cheese not "green" green cheese, unless, of course, it's a blue moon, then it's made of ripe bleu cheese (not "green" bleu cheese).Chris Peterson wrote:Now I'm confused. Isn't the Moon made of well-aged green cheese? Are there different rules for stars and planetary satellites?bystander wrote:They keep all the "green" stars hidden behind cloaks of dust and gas so that the only stars you see are mature stars that have been aged properly and are no longer considered "green".
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Tue Sep 14, 2010 5:18 am
Of course, and no one can talk to a horse, of course.neufer wrote:Chris Peterson wrote:Of course.neufer wrote:A horse is a horse...
That is, of course, unless the horse is the infamous Equine Locutionist.
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Tue Sep 14, 2010 5:45 pm
Re: Why are there no green stars?Chris Peterson wrote:Now I'm confused. Isn't the Moon made of well-aged green cheese? Are there different rules for stars and planetary satellites?bystander wrote:They keep all the "green" stars hidden behind cloaks of dust and gas so that the only stars you see are mature stars that have been aged properly and are no longer considered "green".
Thanks, Cris and bystander, for your prompt and illuminating answers. I admit being still a greenhorn in astronomy. When I was a boy, 60 years ago, all stars were "golden" to me until my grandfather taught me to find Mars, which, I had to admit, was more reddish.
Meanwhile my sense of decorous diversity in the universe is pleased looking at the lovely greenish yellow of the Lemon slice nebula, IC 3568, which I discovered in the Wikipedia: http://en.wikipedia.org/wiki/Lemon_slice_nebula
Curiosity
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Tue Sep 14, 2010 6:22 pm
Hey, thanks curiosity. I already knew Space was NUTS!!, but i had no idea that it was also Fruity!!curiosity wrote: Lemon slice nebula,IC3568
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Wed Sep 15, 2010 6:19 pm
Well, delaying my decision to register and participate in posting here means I missed the chance to ask questions in this thread! 
Just in case, though, here's one:
What do you think of the various citizen science projects that anyone (with a decent internet) connection can now join? Do you have any favorites?
OK, two questions.
How likely do you think it is that a new class of astronomical object will be discovered, from analyses of the data from Fermi? By analogy, RRATs were recently discovered by radio astronomers.
Just in case, though, here's one:
What do you think of the various citizen science projects that anyone (with a decent internet) connection can now join? Do you have any favorites?
OK, two questions.
How likely do you think it is that a new class of astronomical object will be discovered, from analyses of the data from Fermi? By analogy, RRATs were recently discovered by radio astronomers.
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Wed Sep 15, 2010 6:59 pm
Good questions, both. I'll forward them to Dr. Bonnell, but I promise nothing.JeanTate wrote:Well, delaying my decision to register and participate in posting here means I missed the chance to ask questions in this thread!
Just in case, though, here's one:
What do you think of the various citizen science projects that anyone (with a decent internet) connection can now join? Do you have any favorites?
OK, two questions.
How likely do you think it is that a new class of astronomical object will be discovered, from analyses of the data from Fermi? By analogy, RRATs were recently discovered by radio astronomers.
Re: Ask an Astrophysicist - APOD's Dr. Jerry Bonnell
Posted: Mon Oct 21, 2013 2:11 am
Locked the thread and split a reply regarding comet ISON from this thread to a new topic since this interview is over.
http://asterisk.apod.com/viewtopic.php?f=8&t=32332
http://asterisk.apod.com/viewtopic.php?f=8&t=32332