Featured Research

from universities, journals, and other organizations

"Quiet" Star Wasn't Quiet After All, Say Scientists At National Space Science And Technology Center

Date:
July 9, 2002
Source:
NASA/Marshall Space Flight Center
Summary:
For more than two years the star was "quiet." Or so scientists thought. But the X-ray pulsar EXO 2030+375 was abuzz with activity. Scientists simply lacked the ability to "hear" it over the hum of a nearby black hole.

For more than two years the star was "quiet." Or so scientists thought. But the X-ray pulsar EXO 2030+375 was abuzz with activity. Scientists simply lacked the ability to "hear" it over the hum of a nearby black hole.

Related Articles


Pulsars are tiny rapidly rotating neutron stars – the material left over after normal stars burn out and collapse under their own gravity, until just a sugar cube-sized piece can weigh as much as 200,000 elephants.

A study by scientists at the National Space Science and Technology Center (NSSTC) in Huntsville Ala., the University of Southampton in England and the University of Valencia in Spain, offers new insight into the EXO 2030+375 star system, particularly during a period of 32 months, from August 1993 to April 1996, when it appeared to be inactive.

This type of pulsar studied, a transient accreting X-ray pulsar, orbits a massive star eight to 15 times the mass of our Sun, with a distinctive signature – optical emission lines caused by glowing material blown off the star into a disk around its equator.

"The nearby black hole, Cygnus X-1, makes a lot of noise," said Dr. Colleen A. Wilson-Hodge, a NASA astrophysicist at the NSSTC. "If this black hole were in the frequency range where we could hear it, it would hum."

This "humming" of the black hole, scientists now believe, was loud enough to give the false impression that the X-ray pulsar EXO 2030+375 was inactive. But thanks to a new technique developed by Wilson-Hodge and fellow NSSTC researcher Dr. Mark Finger, they now believe it was as active as ever.

The new technique analyzes existing data, but uses different mathematical equations to compensate for the hum of the nearby black hole.

The researchers used data from a special device -- the Burst and Transient Source Experiment, better known as BATSE. BATSE was designed to observe gamma rays, a powerful form of energy invisible to the naked eye and undetectable by most telescopes that -- unlike BATSE -- "see" only visible light.

This instrument was mounted on NASA's Compton Gamma Ray Observatory, which orbited Earth from 1991 to 2000. Unlike many telescopes that monitor cosmic objects one at a time, BATSE had a wider range, observing the entire sky for nearly a decade, what Wilson-Hodge believes was a key factor in making the surprise discovery.

"After we accounted for the hum of Cygnus X-1, we realized the pulsar was active during this time frame after all," said Wilson-Hodge. "The signal was merely fainter, as we can now observe using the new techniques."

Correlating the gamma ray observations with optical and infared observations taken by Dr. Malcolm Coe of the University of Southampton and Dr. Juan Fabregat of the University of Valencia in Spain showed the researchers why the pulsar became fainter – the disk of material around the companion star became less dense, giving the pulsar less material to consume.

In addition to discovering the pulsar wasn't "quiet" during those 32 months, the research led to another discovery about the star system. "For the first time ever, we've been able to observe a wave of density in gamma-rays," Wilson-Hodge said.

Density waves -- compression waves, like sound, that travel through cosmic objects and cause a collection of gas – have been observed in the optical wavelength, but never in the X-ray wavelength, until now.

Optical observations of emission lines from hydrogen by Coe and his collaborators also show evidence for a density wave in EXO2030+375. As this density wave moves throughout the disk of material around the companion star, the optical emission lines change shape and the X-ray activity occurs at a different place in the orbit.

These new techniques have the potential to unlock secrets of other star systems. "With every advance -- whether in how we obtain the data, or how we analyze the data -- we obtain yet another piece of the cosmic puzzle," Wilson-Hodge said. "Every breakthrough brings us that much closer to understanding star activity across the universe."

The new study, titled "A decade in the life of EXO 2030+375," was published in the May 1 issue of The Astrophysical Journal.

A collaboration that enables scientists, engineers and educators to share research and other facilities, the NSSTC is a partnership with NASA's Marshall Space Flight Center in Huntsville, Alabama universities and federal agencies. It focuses on space science, Earth sciences, materials science, biotechnology, propulsion, information technology and optics.


Story Source:

The above story is based on materials provided by NASA/Marshall Space Flight Center. Note: Materials may be edited for content and length.


Cite This Page:

NASA/Marshall Space Flight Center. ""Quiet" Star Wasn't Quiet After All, Say Scientists At National Space Science And Technology Center." ScienceDaily. ScienceDaily, 9 July 2002. <www.sciencedaily.com/releases/2002/07/020709054641.htm>.
NASA/Marshall Space Flight Center. (2002, July 9). "Quiet" Star Wasn't Quiet After All, Say Scientists At National Space Science And Technology Center. ScienceDaily. Retrieved December 21, 2014 from www.sciencedaily.com/releases/2002/07/020709054641.htm
NASA/Marshall Space Flight Center. ""Quiet" Star Wasn't Quiet After All, Say Scientists At National Space Science And Technology Center." ScienceDaily. www.sciencedaily.com/releases/2002/07/020709054641.htm (accessed December 21, 2014).

Share This


More From ScienceDaily



More Space & Time News

Sunday, December 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Spokesman: 'NORAD Ready to Track Santa'

Spokesman: 'NORAD Ready to Track Santa'

AP (Dec. 19, 2014) Pentagon spokesman Rear Adm. John Kirby said that NORAD is ready to track Santa Claus as he delivers gifts next week. Speaking tongue-in-cheek, he said if Santa drops anything off his sleigh, "we've got destroyers out there to pick them up." (Dec. 19) Video provided by AP
Powered by NewsLook.com
NASA's Planet-Finding Kepler Mission Isn't Over After All

NASA's Planet-Finding Kepler Mission Isn't Over After All

Newsy (Dec. 18, 2014) More than a year after NASA declared the Kepler spacecraft broken beyond repair, scientists have figured out how to continue getting useful data. Video provided by Newsy
Powered by NewsLook.com
Rover Finds More Clues About Possible Life On Mars

Rover Finds More Clues About Possible Life On Mars

Newsy (Dec. 17, 2014) NASA's Curiosity rover detected methane on Mars and organic compounds on the surface, but it doesn't quite prove there was life ... yet. Video provided by Newsy
Powered by NewsLook.com
Evidence of Life on Mars? NASA Rover Finds Methane, Organic Chemicals

Evidence of Life on Mars? NASA Rover Finds Methane, Organic Chemicals

Reuters - US Online Video (Dec. 16, 2014) NASA's Mars Curiosity rover finds methane in the Martian atmosphere and organic chemicals in the planet's soil, the latest hint that Mars was once suitable for microbial life. Linda So reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins