Tuesday, October 30, 2012

Looks like Lunch for Sag A*?

In the past week I've fielded several questions about the gas cloud, G2, which is possibly on course to be accreted by the supermassive black hole at the centre of our Galaxy. So I decided I would update my knowledge (and the wikipedia page about Sag A*) on this object with the below:

Discovery of G2 Gas Cloud on an Accretion Course with Sag A*

An artists impressive of G2 approaching Sag A* (orange). The blue lines indicate orbits of known stars about the black hole. Credit: ESO/MPE/Marc Schartmann
First noticed as something unusual in images of the centre of our Galaxy in 2002 (https://www.llnl.gov/news/newsreleases/2012/Oct/NR-12-10-07.html), the gas cloud, G2, which has has mass about 3 times that of the Earth was confirmed to be likely on a course taking it into the accretion zone of Sag A* in a paper published by Nature in 2012 (Gillessen et al. 2012). Predictions of its orbit suggest it will have a closest approach to the black hole (a perinigricon) in mid to late 2013. At this time the gas cloud will be at a distance of just over 3000 times the radius of the event horizon (or ~260 AU, 36 light hours) from the black hole. Opinions differ as to the impact this might have on both G2 and the black hole. G2 appears to already be being distrupted over the past 3 years of observation (Gillessen et al. 2012), and may be completely destroyed by the encounter. If this is the case a significant amount of it may be accreted by Sag A* which could lead to a significant brightening of X-ray and other emission from the black hole, likely to last over the next several decades. Other astronomers (http://www.scientificamerican.com/article.cfm?id=black-hole-gas-blob) have suggested the gas cloud may be hiding a dim star, or even a stellar mass black hole, which would hold it together against the tidal forces of Sag A* and the ensemble may pass by without any effect. 

The average rate of accretion onto Sag A* is unusually small for a black hole of its mass (Morris et al. 2012) and is only detectable because it's so close to us. This passage of G2 in 2013 will offer astronomers the chance to learn a lot more about how material accretes onto supermassive black holes. A suite of astronomical facilities are planning to observe this closest approach, with observations confirmed with Chandra, XMM, EVLA, INTEGRAL, Swift, Fermi and requested at VLT and Keck (https://wiki.mpe.mpg.de/gascloud/ProposalList). 

Groups at ESO (http://www.eso.org/public/news/eso1151/) and LLNL (https://www.llnl.gov/news/newsreleases/2012/Oct/NR-12-10-07.html have been working on simulations of the passage. 

Gillessen et al. 2012
Morris et al. 2012

Tuesday, October 23, 2012

Wiki-a-thon for Women in Science

On Friday I participated via Twitter in the Wiki-a-thon hosted by the Royal Society to improve/create articles about women scientists in wikipedia.

Ever since I heard about this I thought it was a fantastic idea, and while I couldn't make it to London on Friday I was happy to participate online via the Twitter hashtag #WomenSciWP

During the event I improved the article about Martha Haynes (my former thesis advisor), notable especially as a Henry Draper Medal Winner, and made a new article for Lisa Kaltenegger, a young astronomer (with a dual posting at Harvard and MPIA) who works on exoplanets, and is already notable - she has an asteroid named after her, and was named "America's Young Innovator in Science and Technology in 2007 - and will I'm sure become more notable in the future.

What I missed on the day was the page with the list of scientists the Royal Society suggested needed pages. This is an excellent resource to keep plugging away at improving this area of wikipedia. As soon as I found the list I made two new articles about women astronomers on it who are featured in a book I have on "Women in Early British and Irish Astronomy" (by Mary Bruck). These are Anne Walker and Isis Pogson. I was delighted to notice this morning that the article on Isis has already been expanded beyond the start I made.

During the event @edyong209 tweeted to ask me some questions (and said he was writing an article for Nature about the event). He quoted me in that article which was a nice surprise: Edit-a-Thon Gets Women Scientists into Wikipedia (a note for any twitter skeptics - if I wasn't on twitter I would neither have known about this event, connected with Ed to have this "interview", or been quoted in Nature - an event which got picked up this morning by my University's media stream and emailed to me by my head of department.....).

There's been several other articles about the event too. It seems to have struck a chord which is great.

Throw off the Cloak of Invisibility (by Athene Donald, also in Nature)
Wikipedia Edit-a-thon Brings Women Scientists out of the Shadows (in the Guardian)

And as I write this my book on early British and Irish women astronomers sits on the table next to me, and I'm itching to dig into it to add more women to wikipedia. This might turn out to be a bit addictive!

Friday, October 19, 2012

Tuesday, October 16, 2012

Ada Lovelace Day Post: Nobel Prize Winning Women in Science

This post is for Ada Lovelace Day, and will appear on Finding Ada as a book reveiw.

Celebrated annually on 16th October, Ada Lovelace day is a day for sharing online inspiring stories of women scientists, engineers or mathematicians. The Guardian covered it yesterday (article). And if you don't know who Ada Lovelace is, well then she's just one of the amazing women you need to read about on this day.

I've been asked to write a book review about "Nobel Prize Women in Science", by Sharon Bertsch McGrayne. It's a book in which you can read chapter long biographies of 15 women who have won (or significantly contributed to the science of) a Nobel Prize in one of the science fields. Certainly a good theme for a day about celebrating inspirational women scientists. 

When I first read this book several years ago, the thing which struck me most about it, was that it could exist in a (then) complete form. In fact it remained a complete listing of all women who had won Nobels in science fields until 2008 (with Françoise Barré-Sinoussi being a joint winner of the medicine prize that year).

In the last couple of weeks, the 2012 Nobel Prizes in science fields (physics, chemistry and medicine) have been announced. The physics prize went to David Wineland and Serge Haroche for "ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems"; the chemistry prize went to Brian Kobilka and Robert Lefkowitz for work on protein receptors; and the medicine prize went to John Gurdon and Shinya Yamanaka for their work demonstrating that mature cells could be turned into stem cells. 

These are undoubtably all great contributions to science, and well worthy of the prize (although there has been some controversy over if the chemistry prize winning work really counts as chemistry), but as I watched the announcements roll in I couldn't help be a little bit disappointed that yet again there were no women among the recipients. In 2012, six men won the prizes in science, in 2011 seven men shared the prizes. In fact in the last women to win a science prize were three years ago in 2009 when three of the nine total recipients were women (Elizabeth Blackburn and Carol Greider sharing the medicine prize with Jack Szostak, while Ada Yonath was one of the three winners of the chemistry prize). 

In the whole of the 21st century (2001-2012), only four of the recipients of Nobel prizes in science (out of 89 total winners) have been women (that's just about 4.5%); added to the 10 women who won in the 20th century, that makes 14 women who have ever been given Nobel Prizes in a science field. 

In a sense this is good news for the book which is only missing 4 stories to be complete to this day. But of course it's also disappointing. At the point of it's publication, the book claims that only 2% of the more than 300 Nobel Prizes in Science had gone to women. That we cannot do better than just doubling that fraction in the first decade of the 21st century is not encouraging.  

The book itself is well worth a read. I find it actually rather inspiring and motivating, and often dip into it when in need of a bit of perspective on the struggles of a career in science. The lives of these women were at times so difficult, and not one of them had an easy route. The common factor they all possess seems to be an overwhelming love of science and of discovering the world around them. Nothing more than that could have taken them to the point they reached. 

The book is arranged chronologically, and as such represents an interesting progression, from the outright discrimination and legal barriers faced by the pioneers in the early part of the 20th century (Marie Curie, Physics 1903, Chemistry 1911; or Lise Meitner and Emmy Noether - neither of whom won a Nobel Prize), to more complex (and often WW2 related) problems of the second generation,  (Gerty Cori, Irene Curie, Barbara McClintock, Maria Mayer, Rita Levi-Montalcini, Dorothy Hodgkin, Chien-Shiun Wu, Gertrude Elion, Rosalind Franklin and Rosalyn Yalow). 

 Many of these "second generation" women faced problems with anti-nepotism laws in the US (not allowing univerisities to hire married couples). McGrayne points out that even today something like 70% of women physicists are married to other scientists, and when working in a team with men, women's contributions have historically been overlooked. Several of these women only received formal recognition for their work after they won a Nobel. In the first Chapter of the book McGrayne writes an interesting summary of all these obstacles, concluding with a statement which sticks in my mind:
Given the enormous problems they faced and the important discoveries they made, the real question to be asked about these women is not "Why so few?" A better question is "Why so many?" (Chapter 1, pg 8).
The last two chapters profile what McGrayne calls the "New Generation". These are Jocelyn Bell (whose advisor won the Nobel Prize for the discovery of pulsars which she led the observations of) and Christine Nusslein-Vollard (Nobel Prize in medicine, 1995), who only appears in the Second Edition version. It makes me wonder if McGrayne was expecting this book to become dated quickly as significantly more women from this group won prizes. I wonder if she's disappointed in the still slow progress in the decade since this edition of the book was published. In her afterword some of this frustration already seems to be showing: 
Are women racing into science? Yes and no. The number of women earning science degrees rose steadily between the 1960s and the late 1980s. Then it stopped growing. Why?
She talks about one of the reasons being the poor representation of women scientists in textbooks (usually just Marie Curie appearing). I hope Ada Lovelace day will do its bit to improve this.

Curiously, women (well at least in goddess form, and perhaps less clothed than a typical scientist) are well represented on the medal itself. The reverse shows two female figures, the upright one depicts nature, in the form of the godess Isis, emerging from the clouds holding a cornucopia (a "horn of plenty); while the kneeling women holding up the veil off the face of Isis depicts the "Genius of Science". You can read a full description on the Nobel Prize website.

I hope one day the representation of women winning this prize will be as good. 

I linked to all the Wikipedia articles about these women where you can find some fascinating facts. For example, did you know that Rita Levi-Montalcini is the oldest living Novel laureate, and the only one so far to have reached 100! Also it reminded me of this great Royal Society Workshop happening later this week: Women in Science: Wikipedia Workshop, with the aim of improving wikipedia articles about women in science. The event can be joined online (Twitter hashtag #WomenSciWP). 

Friday, October 5, 2012

LOFAR observation of beautiful galaxy, M87

I just posted the below over on the LOFAR-UK blog, but is also fits into my series of Messier Object posts - this one M87, which has a beauty in the eye of the beholder perhaps as a "boring" elliptical, but check out that jet from it's actively accreting supermassive black hole. Amazing!


A paper appears on the arxiv today with new images of the centre of nearby elliptical galaxy M87, taken with the Dutch LOFAR stations.

M87 at Metre Wavelenghts: the LOFAR Picture, by de Gasperin et al. (A&A in press).

M87 (also known at Virgo-A) is one of the two massive elliptical galaxies found at the centre of our nearest cluster of galaxies (the Virgo cluster).

In the centre of M87 is a well know actively accreting supermassive black hole, which is emitting jets of energetic particles which emit significant amounts of radio. These jets are even (just) visible in optical images of M87 (the blue line below).

Optical image of M87 taken with Hubble Space Telescope. Scale 3x3 arcmins.  More details. 

M87 has often been a poster child for radio astronomy images. These images of the jet taken by the NRAO's VLA can be seen in many talks about radio galaxies and AGN.

M87 imaged at 90cm (300 Mhz) with the VLA. Scale 15x15 arcmin. More details. 
And especially this series of images zooming into the central regions.

For more details see the APOD entry for this image

The paper on the arxiv today used observations of M87 with both the HBA and LBA arrays of LOFAR. The Dutch stations only were used in this observation - adding in international stations like Chilbolton will be able to increase the resolution even further, and I will look forward to seeing that in the future.

I have extracted two of the images from the paper. This first was taken with the HBA at 140 MHz (2.1 m) and shows an area 15x15 arcmin in size (same as the VLA image above, but at wavelengths more than twice as large).

And this shows one of the many LBA images made - this one at 25 Mhz (12m) of a slightly larger sky area (21x21 arcmin). 

These new observations at lower frequencies than ever before allow scientists to better constrain the spectral shape of the radio emission from the jets, which in turn can be used to constrain the details of how the supermassive black hole in the centre of M87 is able to power these extremely extended emission regions.

Thursday, October 4, 2012

Talking about Girls in Physics on BBC News Channel

Last night I was invited to talk about girls in physics on the BBC News Channel. It was an interesting experience - driving to Southampton for just a couple of minutes on screen, but I felt well worth it to help highlight this important issue.

Thanks to @billkeck2 for tweeting this screen shot of me mid flow!

A report (It's Different for Girls) was published yesterday by the Institute of Physics which showed that almost half of all state schools in England do not send any girls to study physics A-level.

This has been picked up very widely in the UK, following an excellent article by Pallab Ghosh: "State Schools Failing Girls in Physics". It was also covered by the childrens news show "Newsbeat": A-level physics turns off girls from studying subject.

 I was interviewed as a "talking head" by Joanna Gosling about the subject. She started by asking me if I was surprised by the findings (not really, although it's disappointing it's not getting any better), then we talked about what might be the reason. I thought there'd been too much teacher  bashing about this, and so instead I brought up the early gender labelling we apply to children (using my daughter as an example) which must contribute to girls thinking they shouldn't want to study physics. We then talked about good ways to encourage children to be interested in science, and finally she asked me why I went on to study physics - I talked about getting hooked by being able to explain things you can see in the night sky with physics. 

Edited to include the below clip of the interview: