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February 2001

News about Science, Technology and Engineering at Iowa State University

Astronomers detect supernova in the making
Astronomers recently discovered a supernova in the making. A group of astronomers from Iowa State University helped an astronomer from the Smithsonian Astrophysical Observatory discover the supernova, designated SN2001V, as it ramps up to "maximum light," or the point at which the greatest amount of visible energy is emitted from the object as viewed from Earth.

"It is incredible to see a supernova of this type caught so early before it reaches maximum light," said Phil Appleton, an ISU associate professor of physics and astronomy. "We use these types of supernovas to map out the expansion of the Universe, so studying and understanding these 'type 1a' supernovas is quite important."

Appleton said a quick check of ISU's archived images showed that the astronomers had images of the object "before the explosion" as it transformed into a supernova. Type 1a supernovas are thought to be caused by the explosion of a white dwarf star when matter from a nearby companion star flows between the two and causes one to explode. SN2001V is roughly 180-million light years from Earth.

Appleton said the supernova was detected as part of an international COLA project -- for Compact Objects in Low-power AGNs (active galactic nuclei) -- in which astronomers were carrying out a survey of galaxies both in the northern and southern hemispheres. As part of that project, the ISU team had obtained service observations -- observations performed by a third party -- of a nearby galaxy (NGC 3987), on a telescope run at the Center for Astrophysics at Harvard.

"The exciting thing is we can map the supernova over a period of a few days as it grows to its peak brightness," said Appleton, who monitors the object from the E.W. Fick Observatory, near Boone, Iowa. "The supernova continues to grow in brightness by 15 per cent per day and we expect the peak to be reached within a week (March 1-7)." For more information, contact Appleton, (515) 294-3667, or Skip Derra, ISU News Service, (515) 294-4917. An image of SN2001V is at www.public.iastate.edu/~pnapplet.

Galactic collisions' continuing role in universe formation
The Milky Way galaxy is cruising through space towards the Andromeda galaxy and the two will collide causing some celestial fireworks. But don't worry. It isn't going to happen any time soon and when it does, the Earth -- given it's relative size and inconspicuous existence -- most likely will be unscathed, said Curt Struck, an Iowa State University professor of physics and astronomy.

Astronomers have found that galactic collisions help generate intense rates of star birth and thus represent a fundamental process in the life of galaxies. "We have found that collisions in local groups are a very important piece of the big puzzle of galaxy evolution," Struck said. Our "local group" of galaxies includes a couple of large galaxies plus a couple dozen small galaxies that are gravitationally bound to the Milky Way. Andromeda is a member of our local group.

Struck -- with ISU collaborator Phil Appleton -- has studied galaxy collisions by examining Cartwheel galaxies, which form a characteristic ring-and-spoke shape after a whole galaxy has passed through the center of it. His research has helped determine how enormously large amounts of star birth are stimulated by galaxy collisions.

The Milky Way-Andromeda collision won't happen for another 500 million years. Struck said the two galaxies are in each other's grasp, but Andromeda is about 50 per cent larger than the Milky Way. Astronomers are not sure how the collision might work out.

"The collisional effects might amount to as little as having a night sky with twice as many stars," Struck said. But from a different vantage point the collision could be spectacular. "If you were viewing it from a companion galaxy, one galaxy diameter away (roughly 30,000 light years) after a direct collision, you might see a second Milky Way in the form of an elliptical ring subtending about 60 degrees on your sky with a couple dozen 2 to 4 magnitude blue knots around it. Pretty cool," Struck said. For more information, contact Struck, (515) 294-3666, or Skip Derra, ISU News Service, (515) 294-4917.

Three Ames Lab inventions make DOE's top 100
Three technologies developed at the U.S. Department of Energy's Ames Laboratory at Iowa State University are among those recognized on DOE’s all-time scientific and technological achievements. The Energy 100 awards honor the 100 best scientific and technological accomplishments since DOE's creation in 1977. Photonic bandgap structures was number 24 on the list, a lead-free solder was 36th and magnetic refrigeration was 59th.

Photonic Bandgap (PBG) Structures. Developed in 1990 by senior physicists Kai-Ming Ho and Costas Soukoulis, and physicist Che-Ting Chan, these structures can manipulate light the same way semiconductors manipulate electrons. The feature sizes of PBG crystals have been made smaller and smaller so that the devices can be used to manipulate radiation from microwaves to visible light. Uses range from directional antennas to more efficient lasers and possibly optical chips that use photons instead of electrons.

Lead-Free Solder. Developed by a team of researchers led by Iver Anderson, director of the Ames Lab Metallurgy and Ceramics program, this material is a candidate for a universal paste-type solder. It is an alloy composed of tin, silver and copper. Anderson's solder, developed in 1994, has a low melting point, stands up well to corrosion and oxidation, and remains strong at high temperatures.

Magnetic Refrigeration. Ames Lab senior metallurgists Karl Gschneidner Jr. and Vitalij Pecharsky discovered a material that could replace liquid chemicals as coolants in refrigerators and developed (in 1997) magnetic refrigeration as a potentially reliable cooling technology. Magnetic refrigeration takes advantage of the magnetocaloric effect, the ability of some materials to heat up when magnetized and cool down when removed from the magnetic field. Using this technology, Gschneidner and Pecharsky built a proof-of-principle apparatus that demonstrated magnetic refrigeration as a reliable, competitive cooling technology. Recently, the scientists discovered the giant magnetocaloric effect, which is 2 to 10 times larger than other prototype refrigerants, in gadolinium-silicon-germanium alloys.

For more information, contact Ho, (515) 294-1960; Anderson, (515) 294-4446; Gschneidner, (515) 294-7931; or Kerry Gibson, Ames Lab Public Affairs, (515) 294-1405.


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