Megan's Blog

Outback Outreach (part three!)

I've just got back from my third trip out to the Murchison region of WA. It was also the third time I've been up there to do public outreach - far more than I'd imagined when I took this job! I was hoping to visit the proposed site for the SKA once (if I was lucky) while I was here, even if I had to take a holiday to do it, but despite the region having a very low population density, I've done three trips up there to do public outreach in less than a year.

The first was to visit the school at the remote Aboriginal community of Pia Wadjarri, the second was with a group of Aboriginal artists who were working on pieces for an astronomy-themed exhibition. This one was to run an observing evening for the Meekatharra School of the Air kids who were camping at Boolardy station. Because the population is so sparse up there, the kids are taught over the airwaves until they go off to secondary school. Several times a year, they all get together in one place and have a camp.

It was a long way to go for one evening, but it was worth it. The kids were brilliant. They had some unusual questions, but I was expecting that. I guess they have a slightly different outlook on life than kids who go to school in Perth. Some of them knew quite a lot, so giving answers that everyone understood was something of a challenge.

This time I went up with Tim Colegate, a PhD student at CIRA. I picked up the 4x4 (a Toyota Prado) in the morning and (by the time we'd loaded everything) we set off for Geraldton sometime between 11am and noon. It rained a lot. They were short showers, but they were heavy and frequent. We got to Geraldton late afternoon and went for some food in town. Being a Monday, the place was rather quiet, but the little Italian place was open, so we ate in there.

We had a few errands to run in Gero on Tuesday morning, so we set off for Boolardy late morning. After all the recent rain, the dirt road north from Pindar was still open, but there were some big puddles. We arrived at Boolardy, with a pretty dirty 4x4, at about 3pm and met some of the kids before driving out to the telescope site for a quick nose around. We got back and the clouds still hadn't lifted, so we had to change the plans slightly. By the time dinner was over (two camp-oven stews created in a cook-off between two teams!), the clouds were patchy enough that it was worth getting out the 8-inch Dob (but not the motorised 5-inch as it would take too long to set up).

We split the group into two: half looked at the Moon through the Dob with Tim, while the others played with a radio receiver and MWA dipole with me, then swapped over. As there are no radio stations in the Murchison, we hooked up Tim's FM transmitter to an iPod and challenged the kids to find the signal! The clouds cleared enough to let everyone see Saturn by the end of the evening. Once the kids had gone to bed, it cleared up beautifully of course... so we showed the adults Jupiter which had just risen, and a whole bunch of Milky Way highlights, before packing up, finally, at 11pm.

Today we drove all the way back from Boolardy, skipping the detour to Geraldton this time as Marissa from MSOTA had offered to return the 8-inch for us. We left Boolardy at about 9am with some directions from Carolyn at Boolardy on the most efficient route back to Perth. It involved a lot of driving on dirt roads (great fun - and what 4x4's are actually meant for...) and a lot of small towns, but it was fun.

As we had more time than we would have if we'd gone via Geraldton, we took a short detour to New Norcia. The place was founded by Benedictine monks a couple of hundred years ago and has some buildings which are totally out of character with what you'd ecxpect in WA. It also has a tracking station, used to send commands and receive transmissions from spacecraft. So, being a geek, I stopped to take a photo. By the time we got back to Perth, Tim and I had driven more than 1500 km between us.

All in all, another great trip. And it's unlikely to be the last as we are planning to visit many more of the remote schools to run astronomy days like we did at Pia last year. I can't wait. It's so different up there, so quiet and peaceful. I feel more at home up there than I do in the city!

In the News this month... and finally

May was a busy month in space with the successful launch of two space telescopes and a servicing mission to Hubble. On the 11th of May, the space shuttle Atlantis took off on the fifth and final flight to service the Hubble Space Telescope. During the 13-day flight, the crew carried out five spacewalks totalling 36 hours and 56 minutes, successfully installed the Wide Field Camera 3 and the Cosmic Origins Spectrograph, and repaired both the Advanced Camera for Surveys and the Space Telescope Imaging Spectrograph. The astronauts also replaced all six of Hubble's batteries launched with the telescope in 1990 and now losing capacity as they age. Other tasks included replacing the fine guidance sensors and all six rate sensor units - the gyroscopes essential to keep the telescope pointing in the right direction. The upgrades will hopefully allow the telescope to keep functioning until 2014 when the James Webb Space Telescope is scheduled to launch.



May 14th saw the successful launch of the Herschel and Planck satellites, lifting off together on board an Ariane 5 rocket from the European Space Agency's launch site in French Guiana. Planck is a telescope designed to map the tiny fluctuations in the Cosmic Microwave Background in unprecedented detail, while Herschel is an infrared telescope which will study some of the coldest objects in the Universe. Once in space, the two satellites separated from each other in order to travel independently out to a point known as L2 - a gravitationally stable orbit one and a half million kilometres on the opposite side of the Earth from the Sun. Both satellites are undergoing in-flight tests and are so far functioning perfectly.

In the News this month... Fermi sheds light on high energy cosmic rays

There has been much speculation over the cause of an excess of cosmic-ray electrons and positrons recently detected by the ATIC and PAMELA experiments. Suggested sources of this excess not only include Galactic pulsars and supernova remnants, but also more exotic explanations such as dark matter annihilations. Now, new results from the Large Area Telescope, or LAT, on board the Fermi satellite have added new information to the puzzle.

Models of cosmic ray electrons and positrons interacting with the interstellar medium predict a featureless distribution in the number of particles with energies between 10 and a few hundred giga electron volts. However, last year the European satellite PAMELA detected surprisingly large quantities of high-energy positrons, while the balloon-borne ATIC experiment found a significant peak in the total electron plus positron count at high energies. Like ATIC, the LAT on Fermi is sensitive to the total electron plus positron flux. The new results from Fermi, published in the journal Physical Review Letters on the 4th of May, do show a larger number of particles with energies of around 500 giga electron volts, but the excess is no where near as large as that measured by the ATIC experiment. The new results are, however, consistent with the excess of positrons seen by PAMELA.

While these Fermi observations are the most precise yet at these energies, they are still not enough to either confirm or rule out a particular origin for these high energy particles. The LAT team are planning further observations to reduce the uncertainties and hopefully determine whether the particles are caused by dark matter annihilations or known local sources of electrons such as pulsars and supernova remnants.

In the News this month... the puzzle of crystalline silicates in comets

Models of solar system formation show that comets form at large distances from their parent star. This makes sense as they are made up largely of frozen material, but a long-standing mystery is how they end up containing tiny silicate crystals which need very high temperatures to form. These crystals start out in an amorphous form where their atoms are arranged randomly. At high temperatures, the atoms in these crystals become more ordered, forming what is known as a crystalline lattice. Because they need high temperatures to form, these crystalline silicates were not expected to be found in comets, so how they come to be there is a puzzle. In the May 14th issue of Nature, a team led by Peter Abraham of the Hungarian Academy of Sciences, published the first evidence of the formation of crystalline silicates in the disk around a young sun-like star. Together with colleagues from Leiden Observatory and the Max Planck Institute for Astronomy in Heidelberg, Abraham used the Spitzer Space Telescope to observe the eruptive star EX Lupi in April 2008 during one of its outbursts. When they examined the spectra from these observations, the researchers discovered the infrared signature of silicate crystals in the disk of dust and gas around the star.

When they compared their results to similar spectra of EX Lupi taken between outbursts, they found that the older observatories only showed the presence of amorphous silicates rather than the crystalline form. In the newer observations taken during the star's outburst, a broad peak corresponding to amorphous silicates was present, but an additional narrow peakat a wavelength of 10 microns was also visible. This narrow feature is likely caused by the presence of forsterite, the magnesium-rich crystalline form of the mineral olivine.

The appearance of this additional feature in the spectrum during the star's outburst suggests that crystal formation was happening in the star's disk during the outburst.  The researchers think that this is the first time ongoing crystal formation has been observed.  They say that the crystals were probably formed on the surface layer of the star's inner disk by heat from the outburst, in a process known as thermal annealing where a substance is heated to a temperature where some some of its bonds break and then re-form altering the material's structure and physical properties.  The forsterite crystals detected are just like those found in comets in the solar system which could have been produced by similar outbursts from out own Sun when it was much younger.

In the News this month... evidence for the origins of millisecond pulsars

Fast-spinning radio pulsars with millisecond rotation periods are thought to be the result of a process involving the transfer of material from a companion low-mass star onto a normal pulsar. This accretion process adds mass and angular momentum to the pulsar resulting in its rotation rate speeding up and the emission of X-rays. Using telescopes around the world, a team of astronomers has for the first time discovered evidence of this process taking place.

Pulsars are extremely dense neutron stars, left over after massive stars explode as supernovae. They have strong magnetic fields which generate beams of light and radio waves which sweep across the sky as the pulsar spins. Most pulsars rotate a few times a second, but some, known as millisecond pulsars, rotate hundreds of times a second. Ordinary pulsars in a binary system with a low-mass companion can start to accumulate material in an accretion disk - a flat spinning ring of material around the pulsar. While this disk exists, it is thought that the radio waves characteristic of a pulsar would be quenched and the object would not appear as a pulsar. When the rate of infalling material slows down and stops, the pulsar's emission would be able to disrupt the accretion disk, blowing material out of the system and allowing the radio emission to resume. Now, a team led by Anne Archibald at McGill University in Montreal, Canada, have found evidence of this process taking place in a binary star system 4000 light years away.

A millisecond pulsar was discovered in the system in 2007, so the team looked back through archive data from several telescopes. What they discovered was a dramatic change in the system over the last decade. Optical observations in 1999 showed a Sun-like star, while observations a year later showed evidence of an accretion disk around the neutron star. By 2002, the evidence for this disk had disappeared. The observations in 2007, made with the Green Bank Telescope in West Virginia, found a millisecond pulsar spinning 592 times per second. The researchers say that this system appears to be the missing link between millisecond pulsars and accreting binary systems known as Low Mass X-ray Binaries. The results were published in the journal Science during May.