Tags: Astronomy, astroseismology, coronal mass ejection, helioseismology, Kepler, Nasa
1 comment so far
There has been a lot of talk about the Kepler space telescope and its mission to find Earth-like planets outside the solar system. Its lesser-known but perhaps more important mission, however, is to collect information about the internal sonic vibrations of stars (expressed as small, periodic variations in emitted light) in order to learn about their evolution and structure.
I interviewed Professor Mike Thompson of the University of Sheffield, who will be analysing the information sent back by Kepler for this purpose.
Mike Thompson is a professor of applied mathematics and solar physics, and head of the school of mathematics and statistics at Sheffield University. He studies astroseismology and helioseismology, in other words the vibrations of a star. He also studies solar physics, stellar structure and evolution, and astrophysical fluid dynamics.
Can you tell me about what you are doing for this mission?
My own scientific interest actually is in terms of the stars themselves rather than the planets that are going around them. I use a technique called astroseismology. Many stars oscillate because of the presence of sound waves that are travelling inside them. These sound waves, if they have the right frequency and wavelength, will actually set up certain resonant oscillations of the star. We measure these frequencies at which stars vibrate by making careful observations of the variations of their light. We can use those frequencies, combining many of them, to measure how temperature varies inside the star, what its composition is, even how fast it’s rotating inside.
A good analogy would be of an organ pipe. And organ pipe of a given length will only sound certain notes. If you measured the frequency of those notes or listened to them you would be able to tell something about the structure of that organ pipe. How long it is or what it’s made of, combined with something about the composition of the gas inside it or the composition of the gas. We’re doing similar things with stars.
What sort of practical applications could we see coming from the information that you’re going to analyze?
I think the main practical benefit of learning about stars is what it tells us about our own sun. One of the things we want to understand better is how the magnetic activity cycles work. So in the case of the sun the magnetic activity cycle manifests itself as a sunspot cycle and that’s connected with highly energetic and potentially damaging explosive events (such as flares and coronal mass ejections). These things come out in ways we don’t fully understand and can’t yet predict at the earth and can have serious impacts on our technological society, on communications satellites, on our power grids and so on.
Are there health implications for these coronal mass ejections?
Yes, there certainly are. If an astronaut is in space when one of these things goes off then they could get seriously fried. People have looked at the occurrence of these against the times when the manned Apollo missions were up in space. The Apollo astronauts were quite fortunate. There were some big explosive events that went on and very fortunately there were no Apollo missions up there at the time. But if we want to send manned missions to Mars which of course is now being talked about, then those astronauts are going to be in space for a considerable period of time.
At the moment one of the very big concerns for those of us who study solar variability is the high likelihood that there would be events that would happen during that time which would actually be fatal to the astronauts involved. So how do you develop technologies, perhaps using magnetic fields around the spacecraft, to protect humans in space?
An artificial magnetosphere would actually deflect these particles away. The alternative would be to have large amounts of lead around you, but of course the expense of getting that mass into space is absolutely prohibitive.
How often do these coronal mass ejections occur?
They happen quite frequently. At the height of the solar cycle there could be one a day of these going off, but most of them aren’t coming towards us. But occasionally you get one of these guys and it comes in full face on at the earth, and then it shakes the Earth’s magnetosphere and causes interesting and very exciting aurora displays. They can knock out power lines.
These coronal mass ejections will take a few days to get from the sun to the Earth, whereas light takes eight minutes. Nonetheless, you don’t get much warning. So, better understanding of the sun, better understanding of what the precursors are for predicting these things would be very valuable.
That’s all for today. He gave me some interesting info about Kepler which I will save for a later post.
Purely by coincidence, New Scientist had an alarming article about the disastrous potential consequences of coronal mass ejections in this week’s issue. Read about it here, with an interesting comment here.
Also, take a look at these amazing robot fish!