| Courtesy Photo
The recently discovered brown dwarf is located in the
constellation Sagitta. It orbits a star not unlike our own
UH astronomer finds rare star
made with Hawai'i telescopes using new technology
By Mia La Londe
Ka Leo Contributing Writer
New celestial bodies have come into view, thanks to recent
developments in telescope optics, said a University of Hawai'i
Michael Liu gave a lecture Tuesday night on his recent findings
on brown dwarfs, also known as failing stars; the use of adaptive
optics in telescopes; and the discovery of planets in other solar
systems, known as extra-solar planets.
"In the last few years, observational astronomy has undergone a
revolution. We are now able to study, observe and characterize
worlds around other stars," said Liu.
Liu and his colleagues announced the discovery of a brown dwarf
at the meeting of the American Astronomical Society in January 2002.
Liu found the brown dwarf using the Gemini North telescope and
the Keck telescope on Mauna Kea. Both of the telescopes use a
technology called an adaptive optics system.
Adaptive optics sharpen images which would normally be blurred
due to the turbulence of Earth's atmosphere, said Liu. Telescopes
using adaptive optics are able to make some images sharper than
those produced by the Hubble Space Telescope, he said.
Liu said the use of adaptive optics was instrumental in the
discovery of the brown dwarf. "It is too faint and too close to its
parent star to be seen otherwise," he said. "If you were standing on
Diamond Head looking at your friend standing on Mauna Kea, you would
be able to tell if they were wearing gloves. That's how powerful
Brown dwarfs are believed to be categorized between planets and
stars. They start out with high temperatures comparable to stars,
but cannot sustain nuclear fusion like stars do.
"Brown dwarfs start off very bright, then cool off. They get ever
fainter, ever dimmer and ever cooler," he said.
Brown dwarfs have masses 55 to 78 times the mass of the planet
Jupiter, the largest planet in our solar system. Jupiter is about
300 times larger than the earth.
According to Liu, since brown dwarfs are more massive than
planets, they cause more tugging on the main star, which makes them
easier to detect than planets.
"Despite the fact that they are easier to detect, we don't see
any brown dwarfs and it is a bit of a mystery. It is something that
astronomers are calling a brown dwarf desert," he said.
The brown dwarf Liu found is located in the constellation Sagitta
around a star known as 15 Sge., which is very similar to our own
Liu said the star is relatively nearby: approximately 58
light-years from Earth. "Its age is 1 to 3 billion years old, which
is slightly younger than our solar system which is about 5 billion
years old," he said.
The brown dwarf lies 14 astronomical units away from its parent
star, 15 Sge. One astronomical unit is the distance between the
earth and the sun; this is equal to 93 million miles.
Until 1995, the planets that rotated around the sun in this solar
system were the only basis that astronomers had to theorize about
planets around other stars.
"In 1995 everything changed for astronomy. They had found a
planet circling a star just like our own sun," Liu said.
Scientists have since discovered many planets and say that those
solar systems are not unlike our own. Five percent of the stars they
have observed have planets and some of those stars have more than
one planet. There are currently 80 known extra-solar planets, said
Scientists cannot detect a planet of Earth's size using current
techniques but according to Liu, they they soon may be able to infer
the existence of Jupiter-sized planets.
Mauna Kea is a world-class site for astronomy, said Liu. On Mauna
Kea, there are currently 11 telescopes, which are operated by
astronomers from 11 different countries. If measured from its base
beneath the ocean, Mauna Kea is the highest mountain in the world.
It rises 32,000 feet, to an altitude of 13,976 feet above sea level.
The atmosphere above Mauna Kea is extremely dry, which is important
in measuring infrared light from celestial sources. Liu called the
view from Mauna Kea "a spectacular sight."
Liu is the Beatrice Watson Parrent Postdoctoral Fellow of the
Institute for Astronomy and UH. Parrent Fellows are given two years
of funding for their choice of study. The funds can be extended to a
third year at the discretion of the director of the Institute for
Liu received his doctorate in physics and astronomy from the University
of California at Berkeley.