Author Topic: Thursday 2nd July 2009: Hydrogen Stars  (Read 4835 times)

Alice

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Thursday 2nd July 2009: Hydrogen Stars
« on: July 01, 2009, 11:17:32 pm »
Last week we looked at some pictures of increasing fuzziness to find out how far back into the distance we should ask zooite eyes to look for our next project, Hubble Space Telescope Zoo. This week the original plan was to look at some actual fuzzy blobs by Hubble - which is, contrary to appearances, Hubble's usual output! - but because poor Chris is laptopless, they will have to wait.

But the timing's excellent, because I would like to use this Object of the Day to expound on a little rant I indulged in for the She's an Astronomer project yesterday. (Well, actually a couple of months ago in advance, but you know what I mean. :D) I mentioned Jocelyn Bell-Burnell and Cecilia Payne-Gaposchkin as women who I believed were treated outrageously unfairly. We all know the story of Jocelyn Bell's supervisor being credited and winning the Nobel Prize for her discovery of pulsars. But Cecilia Payne-Gaposchkin is lesser known - but made an amazing discovery about stars and how they shine.

Here's a lovely star, posted by Citisue and nominated by Mukund Vedapudi:

587736979569901658

Cecilia Payne was studying physics at Cambridge in the early 1920s. But she gave up physics because the brilliant Ernest Rutherford, who discovered so much about atoms, was so rude to her. It must have been clear that her ideas and discoveries would never be heard; Cambridge didn't then even give women degrees after they'd completed their studies. But when she switched to astrophysics, Arthur Eddington was more welcoming, and in Marcus Chown's words, Payne became "fascinated with the problem of decoding the message in starlight". (This message is absorption and emission spectra, which reveal what types of atom are present in stars.)

Absorption and emission spectra tell us what element is present because of the way the electrons jump around, absorbing and emitting photons of light. The way they jump is unique to each type of atom. So it was known that the same types of atom as were present on the Earth were also present in the stars - but stars contained a lot more mysterious lines. Finally it was discovered that these extra lines weren't other atoms, but atoms with some electrons knocked off. (This is exactly what is happening with the Peas!) The raging heat inside stars causes the atoms to shoot around so violently that the collisions knock off one, or two, or many electrons.

A physicist called Meghnad Saha devised an equation to predict what fraction of any element's atoms would be ionised and by how much, at any given temperature and density. Eddington had worked out the temperature and density of many stars around us. Payne was the first person to apply the Saha equation to them.

She had to go to Harvard to pursue her idea, because Cambridge did not accept women as PhD students at the time. She began her calculations and the proportions of elements seemed mostly to be the same as on Earth (for example lots of iron, some oxygen and silicon, only a very little gold and silver, etc). By finding out how much of each element was ionised, she could work out how much of the element there was altogether. But then something unexpected happened.

She found plenty of ionised hydrogen on the surface of the Sun. And only a tiny proportion of hydrogen atoms should be ionised. That meant that the Sun must be mostly hydrogen! Astronomers were convinced at the time, and many remained convinced until the 1950s, that the Sun was made mostly of iron. Henry Norris Russell convinced Payne to retract her discovery and state in a journal that "the abundance of both hydrogen and helium in stars is improbably high and almost certainly not real". It wasn't until more evidence showed that Russell was forced to admit he had been mistaken, and Payne is not well known for her discovery. Nevertheless, her doctoral thesis, published in 1925, was described by an astronomer named Otto Struve as "undoubtedly the most brilliant Ph.D. thesis ever written in astronomy". She went on to make many other discoveries, such as on variable stars.

Posted by dthomas02 and nominated by Sophie 378:

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We now know that the Big Bang created almost exclusively hydrogen and helium, and that these elements are what chiefly make up our Universe. We also know that the Sun shines because it fuses hydrogen into helium, though larger stars and red giants can fuse heavier elements too.

All of which shows, if you ask me, that everybody should be welcomed into astronomy.

Thanks for reading! ;D
« Last Edit: July 02, 2009, 11:02:21 am by Alice »

mgp

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #1 on: July 02, 2009, 02:03:30 am »
Nice history lesson with the astonomy.  Thanks Alice!  :)

weezerd

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #2 on: July 02, 2009, 02:58:39 am »
Excellent story Alice, although sad to narrate!

However nice reading at 3:58a.m. :-\
Oh let me just a moment stay
where time is not and angels play the paeans of the galaxies;
then speed the stardust on its flight
to change dread darkness into light, cold chaos into ecstasy!

Lovethetropics

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #3 on: July 02, 2009, 03:08:01 am »
Wonderful OOTD dear Alice.  I had no idea about those pioneer women in astrophysics.  Thank you so much!  :-* ;D ;D ;D

 *and find lots of asteroids  ;D

AlexandredOr

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #4 on: July 02, 2009, 04:48:28 am »
Thx ! Great.
Unless error these stars make the population III (population I in disks, population II in globular clusters).


Baby star opening its eyes on the Universe.

elizabeth

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #5 on: July 02, 2009, 06:12:12 am »
 ;D ;D Oh, Alice that was a very good read. Thanks ;D

Budgieye

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #6 on: July 02, 2009, 06:23:35 am »
Totally excellent. ;D
It seems hard to believe that a hundred years ago, scientists thought that the sun was made of iron. Many children still think that the sun is made of lava.

Alice

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #7 on: July 02, 2009, 12:09:13 pm »
Thanks everyone for reading this, and thanks Weez for spotting a typo! (Electrons jumping down from "outer shells" to "inner shells" of atoms emit photons, not photos :D)

I have been asked by e-mail whether this story has a happy ending. I honestly don't know! I only find passing references to her in books, and have wanted to know more for a long time. At a guess, I'd say it did - she may not be well-known for her discovery, but she seems to have written hundreds of papers and discovered a great deal more. She married a fellow astronomer and they did a lot of amazing work together, which must have been great.

I think the link I put at the top offers the most information. There is of course a Wiki article, and Google turns up some interesting stuff. It also seems there is a biography. And since She's an Astronomer was the excuse for this post . . . Look what I found! ;D

But seriously, anyone who knows more about her, we'd love to hear. :)

klmasters

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #8 on: July 02, 2009, 01:31:41 pm »
Alice,
 Very nice post. Since you challenged me on your blog I'm going to jump in here! Also I know a few things about Cecilia Payne-Gaposhkin.

 First, I wanted to point out this article about her as an famous "Astronomy Mother" (she had 3 children with her husband): http://astronomom.blogspot.com/2009/04/famous-astronomoms-ceclia-payne.html

 Two things struck me as particularly interesting. The Physics department at Harvard would not grant Cecilia a PhD, so Shapely created the Astronomy Dept. to give her one! I also love the quotes which show how incredibly patient she must have been. Her career was littered with small frustrations even given her early seminal work (for which any man would have been feted), but she never seemed to think it mattered. She is quoted as saying: "I simply went on plodding, rewarded by the beauty of the scenery towards an unexpected goal." In this way Cecilia Payne, and Jocelyn Bell are similar. Neither of then has/did ever expressed (to my knowledge) any annoyance at all at the problems and obstacles they faced.

Karen.

Geoff

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #9 on: July 02, 2009, 01:40:38 pm »
Thanks for an interesting OOTD Alice - very good read  :)
  Sometimes I think we're alone. Sometimes I think we're not. In either case, the prospect is staggering!- Arthur C. Clarke

Alice

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #10 on: July 02, 2009, 02:27:13 pm »
KAREN!! I am so happy to see you here - thanks so much for joining us. 8)

Must follow up your links now. Your statement about how the two ladies didn't get annoyed is a good lesson to me, since I have been annoyed by less! :D

klmasters

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #11 on: July 02, 2009, 02:52:09 pm »
Alice,
 Yes - I am also guilty of getting annoyed at such things. It is so hard to find a balance though. At the award ceremony for women in science last night, the speaker (Baroness Susan Greenfield, a well known scientist famous for being denied entry to the Royal Society, which some people claim was because she was female) made some jokes about this. It's not really funny though. If you complain you're not seen in a good light, but if you keep quiet do you just help to hide the problem. Her recommended solution was to gripe with those in similar situations (other female scientists). Of course there's not always a lot of those around you...

How do I get a signature of my name in galaxies?

Karen.

Alice

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #12 on: July 02, 2009, 03:01:35 pm »
Ahhhhh, we have threads for everything! There are some Galactic Alphabet Repositories Pluk has made in the Cafe (the link to all at once is in my link); put them onto a background, perhaps a starry one, make this into a little JPEG file, host that on flickr or photobucket or similar, and then enter that into your signature the same way as you would post a galaxy picture. There will be plenty of people who would be happy to make one for you, including me :)

Edd

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When I look up at the night sky and think about the billions of stars out there, I think to myself: I'm amazing. - Peter Serafinowicz

Half65

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Re: Thursday 2nd July 2009: Hydrogen Stars
« Reply #14 on: July 02, 2009, 04:46:19 pm »
Great OOTD and great interview on the blog.