STARS AND PLANETS
Well, after reviewing the subjects in my files, I’ve discovered the one that’s dear to my heart is bulging. That’s the ‘space’ file of course, and most of you know that I run the University of Guam Planetarium and I’m also known as “The Star Lady”.
So without further ado, let’s don our spacesuits and make some excursions into the unknown. As I tell my astronomy students, everything you learn in college has to do with the happenings on a very small planet. The course I teach is about everything else! We’ll travel some distance away from our tiny planet for our first stories and then return a little closer to home.
STAR LIGHT, STAR BRIGHT
Most little kids will tell you that stars are star-shaped and very small. They are, of course, wrong. Stars are gigantic balls (our Sun is almost a million miles across) and they’re gigantic atomic bombs. They generate their heat and light from a process called nuclear fusion and when they die, some strange and wonderful things can happen.
Our first story concerns what is probably my favorite star (after the Sun, of course) and it’s also probably the favorite star of every schoolchild everywhere. The star is Betelgeuse and it’s really hard not to like a star whose name is pronounced “Beetlejuice”!
But in addition to the cool name, Betelgeuse is a truly awesome star; one of the largest we know about. It’s a red supergiant and it’s almost 1000 times larger than our Sun. If Betelgeuse took our Sun’s place in our solar system, the star’s edge would be past the orbit of Jupiter and we’d be inside it!
Betelgeuse is nearing the end of its lifespan and it will soon become a supernova. The star is close enough that when that happens, Betelgeuse will become so bright it will be visible in the daytime.
One of the questions that remain about stars like Betelgeuse is just how they shed the tremendous quantities of material they produce. Astronomers have used the European Space Agency’s Very Large Telescope (VLT) to take a closer look at the gigantic star.
The team used a technique called adaptive optics to obtain very good images of Betelgeuse, even with Earth’s turbulent, image-distorting atmosphere in the way. In addition to the adaptive optics technique, only the very sharpest exposures were used. They were combined to form an image much sharper than a single, longer exposure would be. The resolution of this image would allow you to see a tennis ball in orbit around the Earth!
Using these techniques, the astronomers discovered a large plume of gas that extends from the surface of Betelgeuse to at least three billion miles out into space. (That’s about how far away Neptune is.) This plume tells astronomers that Betelgeuse isn’t shedding its matter evenly.
The scientists decided that they were looking at the gas streaming out of one of the poles, or that the plume was simply the top of a very large convection current in the star but there was no way to tell at that resolution.
So another team of researchers used the Very Large Telescope Interferometer which combines the light from three auxiliary telescopes; each with large mirrors. The resolution of this combined instrument was the equivalent of seeing a marble in orbit around the Earth. By using this instrument, astronomers were able to see gas moving on different areas of Betelgeuse’s surface ― the first time this has been done for a star other than the Sun.
The observations revealed that the gas in Betelgeuse’s atmosphere is moving vigorously up and down, and that these bubbles are as big as the star itself. The astronomers now propose that these large-scale gas motions roiling under Betelgeuse’s red surface are behind the ejection of the massive plume into space.
This artist’s impression shows the Betelgeuse as it was revealed ESO’s Very Large Telescope. You can see the plume and the bubble boiling on its surface. These discoveries help explain how these mammoths shed material at such a tremendous rate. (Credit: ESO/L. Calçada)
TWINKLE, TWINKLE LITTLE STAR
After a star like Betelgeuse becomes a supernova, what remains can become what’s called a white dwarf (it can also become a neutron star or a black hole, but we’re not going there this week!). Astronomers have used the data from a satellite that’s sadly no longer with us to discover some really interesting things about one of these stellar remnants.
Although there’s a marketing rip-off scam that purports to name stars for your loved ones, stars are never named for people. There’s been an international prohibition against the practice for centuries. So, most stars have letter and number designations. The white dwarf we’re interested in today is named KPD 0005+5106. Since I loathe typing meaningless strings of letters and numbers, I think we’ll temporarily name it for something small and white and valuable. We’ll call it Diamond.
The kids in the Planetarium ask me how hot the Sun is and I tell them that the inhaled end of a cigarette is around 1,200 degrees and that the surface temperature of the Sun is 12,000 degrees. White dwarf suns are considerably hotter than our star, however and the surface temperatures of many of them have been measured in excess of 100,000 degrees.
Diamond was discovered in 1985 and appears in visible light telescopes as a faint blue star. Blue stars are much hotter than our yellow Sun or white stars which means that Diamond is hotter than most ‘white’ dwarf stars. Theories of stellar evolution predicted stars as hot as Diamond, but astronomers never thought they’d see one because the stage that produces them doesn’t last very long.
The astronomers studying Diamond used the data gathered by NASA’s space-based Far-Ultraviolet Spectroscopic Explorer (FUSE) (1999-2007 RIP) and realized something interesting. Diamond is so hot, that amounts of its energy are being radiated in the far-ultraviolet; the first time this has been observed for any star. The analysis of data from FUSE proves that Diamond’s surface temperature has to be over 200,000 degrees and Diamond is the hottest star we know about!
BRIGHT LIGHTS AND BOOMY NOISES
A few weeks ago, I talked about the new prevalence of thunderstorms on Guam and the fact that air pollution from China is undoubtedly what’s causing them. Lightning is a gigantic electric spark and it’s quite common on the gas giants. There’s been speculation for a long time that lightning also occurs on Venus and in fact, one of our orbiting spaceships confirmed that a few years ago.
Mars has long been considered a ‘dead’ world but the presence of methane detected in Mars’ atmosphere last year says that either Mars has active volcanoes, or there’s primitive life on the Red Planet. Now new data has shown that there’s also lightning on Mars.
University of Michigan researchers have found signs of electrical discharges during dust storms on the Red Planet. The bolts were ‘dry lightning’, the only kind you can have on Mars since there’s no water vapor in the thin atmosphere of Mars.
What the planetologists saw was a series of huge and sudden electrical discharges caused by a large dust storm. There was no rain associated with them, but the implied possibilities are exciting because electrical activity in Martian dust storms has important implications for Mars science.
It affects atmospheric chemistry, habitability and the preparations for human exploration. And it might even have implications for the origin of life, reports Nilton Re
nno, a professor in the Department of Atmospheric, Oceanic and Space Sciences.
The researchers used a microwave detector that can detect between heat radiation and other types of radiation. The instrument took measurements of microwave emissions from Mars for approximately five hours a day for 12 days between May 22 and June 16, 2006. On June 8, 2006, an unusual pattern of non-thermal radiation and an intense Martian dust storm occurred at the same time. This was also the only time non-thermal radiation was detected and non-thermal radiation suggests the presence of lightning.
The researchers reviewed the data to determine the strength, duration and frequency of the non-thermal activity, as well as the possibility of other sources. But each test led to the conclusion that the dust storm likely caused dry lightning.
This work confirms soil measurements from the Viking landers 30 years ago. Data from the Viking landers raised the possibility that Martian dust storms might be electrically active like Earth’s thunderstorms and thus, might be a source of reactive chemistry.
"Mars continues to amaze us. Every new look at the planet gives us new insights," said Michael Sanders, manager of the exploration systems and technology office at Jet Propulsion Laboratory and a researcher involved in this study.
An illustration of a dust storm on Mars. (Credit: Brian Grimm and Nilton Renno)
Space in general continues to amaze me. That’s what I love about my field. It changes every day!!
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