Giant stars and solar storms at NAM2010

The National Astronomy Meeting, 2010 at Glasgow University has been filling a few headlines today (in the area of physics the STFC seemingly believes has the lowest impact of its sectors, or at the very least deserves minimal if any funding…) – Solar Terrestrial Physics. But before I get on to that, a few of the other stories that have leaked out from Scotland. Astronomy Now magazine has been keeping a NAM2010 blog, and I’ve been using that, space news websites and the tweets of those there to keep a little more up to date than I otherwise would’ve been.

We start at the beginning with evidence that giant stars form in the same manner as small stars. This has been a problem due to the high luminosity of giant stars seeming to suggest that material would be blasted away from them before they got too big. Then the magnetic field came into play and new ways of feeding the giant formations became clear. At NAM, evidence for a feeding giant protostar has been presented, with an accretion disc possibly three times the Sun-Earth distance and jets of material blasting away from the central body.

(as a sort of relevant aside, jets of plasma can be produced in any accretion situation, including that of black holes. Active Galactic Nuclei and Quasars are believed to owe their luminosities to this sort of event – here’s a LOFAR – Low Frequency Array – image of the jets of the distant galaxy 3C61.1 – and black holes accreting matter from a binary companion, producing jets, are known as micro-quasars. Observations of a galaxy a mere 10 million light years from us, M82, has revealed the first indication of a microquasar detected in radio wavelengths beyond the bounds of the galaxy. The signal could be a faint ‘radio supernova’, but positional measurements suggest a far larger structure).

Speaking of supernova, the end of the life of massive stars has also been a point of discussion at NAM. As the star moves into the very end of its life cycle, the processes of shedding outer layers of gas reveal layers enriched with the products of the fusion cycle it is undergoing. These Wolf-Rayet stars (hot with strong stellar winds) were the targets in a survey of the galaxy NGC 7793, 13 million light years from us. 52 were found, of which 27 were nitrogen rich (likely to produce a 1b type supernova) and 25 carbon rich (likely to produce a 1c type), believed to represent 90% of all carbon Wolf-Rayets and 80% of all nitrogen ones to be found there. The astronomers hope that next time a supernova is seen in that galaxy, it can be linked to the star that has exploded, giving us information on which stars explode and why.

…and it didn’t end there. The Swift satellite managed to track a Gamma Ray Burster and direct optical telescopes toward it to view the associated supernova for only the second time. Gamma Ray Bursts are bright flashes of gamma rays seen in the night sky. They appear anywhere and on average are seen once a day, though there have been as many as four seen in one day. The theory behind them is they are due to jets of particles unleashed during the supernova of a massive star. The optical telescope spotted evidence of a type 1c supernova (a carbon Wolf-Rayet) at the position of the gamma ray burst. Observations will continue as the supernova cools down.

Now slipping back a moment to just before the deaths of stars and moving down the range to smaller stars like the Sun. As age gets the better of it, the Sun will expand into a red giant and then slowly cast off the enlarged envelope of gas, leaving behind the stellar core as a white dwarf star. The outer envelope will float into space as a giant nebula, glowing through heat and radiation left over from its time in the star as well as new heat and radiation passed on by the glow of the white dwarf. As well as expelling massive amounts of gas and dust in this way, such stars can also create discs of dust around themselves. Such discs, extending a thousand times the Earth-Sun distance, have been spotted at various stages of their evolution, by the Very Large Telescope.

But why should we care if a star happens to be a bit dusty or not? Well according to experiments carried out in a vacuum chamber at -268 C at the Heriot-Watt University, dust may be the source of the missing oxygen. You didn’t know there was missing oxygen? Well as all these chemicals come together in space, they find they are bombarded with and destroyed by radiation from stars. There’s plenty of hydrogen about, some atomic oxygen and even less molecular oxygen (which gets split into atomic oxygen by radiation). The trouble is, hydrogen doesn’t care to react with atomic oxygen at the rate required to produce the water we see and there isn’t enough molecular oxygen to make up the short fall. Experiments have shown that once a bit of frosting exists on the outside of a dust grain, molecular oxygen can survive inside and help make up a little of the shortfall. Future experiments will determine whether adhesion to the surface of the grain can help promote reactions between hydrogen and atomic oxygen (sort of like the lunar surface water, I guess).

I mentioned yesterday about one water bearing thing spoken about at NAM – main belt comets, that is comets residing in the asteroid belt devoid of outer water, but leaking some inner ices due to collisions or fragmentations. An interview with the speaker at the NAM talk has been done by Astronomy Now.

…and so we’re onto the good stuff where all the cool kids were. The Solar Terrestrial Physics stuff…

Just to augment this session the ESA satellite Proba 2 has released a movie or two of the eruption that struck the Earth on April 3rd. This was just a small squall, but the chances of a massive strike by the Sun are pretty high, as they tend to follow times of low activity. The Carrington event of 150 years ago was the first time a connection was made between an observed flare and auroral activity, and also the largest such event in a long time. Using collected archive data, scientists estimate the X-ray flux of the flare would’ve been twice that of the largest flare of the past ten years (which damaged the Swedish electricity network). Furthermore, using the most sophisticated yet models of national power grids, scientists have begun to estimate the damage that such an event would have on modern societies. They estimate 1-2 trillion dollars worth of damage to the USA power grid, with a 4-10 year timeline for it to fully recover. This has received some newspaper and TV coverage. But there are efforts around to try and predict when something is coming. Or at least there is for Mars… using the ACE and STEREO satellites to watch for Coronal Interacting Regions, which produce fast solar wind streams that compress the normal slow wind into a pulse that then strikes the planets.

Of course, if for some reason you feel the need to watch out for things hitting the Earth rather than Mars, then you can always use Solar Storm Watch to look out for solar activity in data from STEREO. More on this in an interview with Astronomy Now on their youtube channel can be seen below:


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