South African Clone of Penn State Telescope Makes First Scientific Discovery

The new Southern African Large Telescope (SALT), an international partnership that includes Penn State, has released its first public research results, which will be published in the journal Monthly Notices of the Royal Astronomical Society. The research gives new insight into an exotic pair of stars that are closely orbiting each other, known as a "polar" binary-star system. These two stars are orbiting each other so closely that the entire system would fit inside our Sun.

SALT was patterned after the successful design of the William P. Hobby-Robert E. Eberly Telescope--one of the largest and most powerful telescopes in the world--which was conceived by Lawrence Ramsey, department head and professor of astronomy and astrophysics at Penn State, and Daniel W. Weedman, formerly a professor of astronomy and astrophysics at Penn State. The Hobby-Eberly Telescope (HET) is located at the McDonald Observatory in a remote area of West Texas, where night skies are among the darkest in the continental United States. "It is gratifying to everyone involved with the Hobby Eberly Telescope that the first scientific results with the Southern African Large Telescope will be published soon," Ramsey comments.

One of the stars in the polar system studied with SALT is an ordinary star like the Sun, but cooler, redder, and about one-third of the Sun's mass and radius. The other star is a compact object called a white dwarf--a star that shrunk to about one millionth of the volume of our Sun after it used up its original store of nuclear energy. This white dwarf is hundreds of thousands of times as dense of the Earth. A chunk of white dwarf as large as a pair of dice would weigh as much as two small trucks. This density gives the white dwarf an intense gravitational field that sucks in material from the larger star. This particular white dwarf has a huge magnetic field--30 million times as strong as the Earth's. "These are incredibly fascinating objects," remarked Penn State Professor of astronomy and astrophysics Donald Schneider, who has worked on these types of binary stars. "The magnetic fields are so powerful that they compress the infalling material into a funnel-like structure that impacts the white dwarf at a single spot: the magnetic pole of the star."

Polars are the most readily accessible objects for studying gas accretion in strong magnetic fields. They also are among the most closely orbiting pairs of stars known. The polar that astronomers studied with SALT takes only one-and-a-half hours to complete an orbit, compared to a month for the Earth and moon, and a year for the Earth and Sun.

The radiation emitted as the gravitational field of a compact star gobbles gas from its companion star is one of the indirect ways astronomers detect black holes. It also is the way that mass builds up on some compact stars until supernova explosions blow them apart, producing the 'Type Ia' supernovas that astronomers have used recently to show that the expansion of the universe is speeding up.

The innovative, precision design of the HET dramatically reduces construction costs and has opened the door to a new era for such large-sized telescopes, including SALT, which was inaugurated in November 2005. The HET received the Discovery Magazine Award for Technological Innovation in 1997.

This first research result from SALT uses a strength of the telescope's design that is rare among large telescopes, the ability to take 'snapshots' of stars in very quick succession, making it possible to study the rapidly changing properties of compact stars, especially as they pull in gas from their companions or surroundings. SALT's advantages for this type of research are expected to allow SALT astronomers to be among the leaders in probing the mysteries of these 'cannibal stars'.

Source: Penn State

Related stories:

What's My Age? Mystery Star Cluster Has 3 Different Birthdays
Imagine having three clocks in your house, each chiming at a different time. Astronomers have found the equivalent of three out-of-sync "clocks" in the ancient open star cluster NGC 6791. The dilemma may fundamentally challenge the way astronomers estimate cluster ages, researchers said.
Hubble's sweeping view of the Coma Galaxy Cluster
Hubble's Advanced Camera for Surveys has observed a large portion of the Coma Cluster, stretching across several million light-years. The entire cluster is more than 20 million light-years in diameter, is nearly spherical in shape and contains thousands of galaxies.
W28: A Mixed Bag of Supernova Remnant
When some stars die, they explode as supernovas and their debris fields (aka, "supernova remnants") expand into the surrounding environments. There are several different types, or categories, of supernova remnants. One of these is known as a mixed-morphology supernova remnant.
White Dwarf Lost in Planetary Nebula
Call it the case of the missing dwarf. A team of stellar astronomers is engaged in an interstellar CSI (crime scene investigation). They have two suspects, traces of assault and battery, but no corpse.
Argonne supercomputer to simulate extreme physics of exploding stars
Robert Fisher and Cal Jordan are among a team of scientists who will expend 22 million computational hours during the next year on one of the world’s most powerful supercomputers, simulating an event that takes less than five seconds.
New type of pulsating white dwarf star discovered
University of Texas at Austin astronomers Michael H. Montgomery and Kurtis A. Williams, along with graduate student Steven DeGennaro, have predicted and confirmed the existence of a new type of variable star, with the help of the 2.1-meter Otto Struve Telescope at McDonald Observatory. The discovery is announced in today's issue of Astrophysical Journal Letters.
Crescent Moon Alert
The date was March 8th, less than a month ago. In a remote corner of Kansas, the sun was going down and the deepening twilight beckoned to photographer Doug Zubenel driving through the countryside. Something photogenic, he knew, was about to happen.
Black hole found in enigmatic Omega Centauri
A new discovery has resolved some of the mystery surrounding Omega Centauri, the largest and brightest globular cluster in the sky. Images obtained with the Advanced Camera for Surveys onboard the NASA/ESA Hubble Space Telescope and data obtained by the GMOS spectrograph on the Gemini South telescope in Chile show that Omega Centauri appears to harbour an elusive intermediate-mass black hole in its centre.

News discussion:

Space & Earth science news