archive: SETI Ulysses Captures Gamma-Ray Flare

SETI Ulysses Captures Gamma-Ray Flare

Walt Williams ( (no email) )
Fri, 2 Oct 1998 17:52:02 +0000

Hello All,

The SOHO spacecraft went ka-blooie around August 27: was its
anomaly related to this event?

What about the GOES-7?

Thank you.

Walt Williams, 98.10.01
dfheli@pacificnet.net
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------- Forwarded Message Follows -------
From: Larry Klaes <lklaes@zoomtel.com>
To: "'CS'" <carlsagan@craigerware.avalon.net>, "'ST'" <seti@sni.net>
Cc: "'SK'" <skingsle@postbox.acs.ohio-state.edu>
Subject: SETI FW: [ASTRO] Ulysses Captures Gamma-Ray Flare From Shattered Star
Date: Fri, 2 Oct 1998 17:17:08 -0400

----------
From: Ron Baalke
Sent: Friday, October 02, 1998 12:41 PM
To: astro@lists.mindspring.com
Subject: [ASTRO] Ulysses Captures Gamma-Ray Flare From Shattered Star

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Contact: Diane Ainsworth

FOR IMMEDIATE RELEASE October 1, 1998

ULYSSES CAPTURES GAMMA-RAY FLARE FROM SHATTERED STAR

The signal of a cataclysmic magnetic flare emanating from a
star that
cracked apart halfway across the galaxy has been captured by NASA's
Ulysses spacecraft and is providing important clues about some of the
most unusual stars in the universe.

The magnetic burst from the star SGR1900+14, located in the
constellation Aquila 20,000 light-years away, was observed by Ulysses
and other spacecraft with high-energy radiation detectors in space on
August 27, 1998, as its heavy metal crust fractured and released the
most powerful wave of gamma radiation yet observed from this type of
star.

"Soft gamma repeaters (SRGs) emit magnetic radiation
sporadically,
every few years, unlike gamma ray bursts, which explode and
disappear," said Dr. Edward J. Smith, Ulysses project scientist at
NASA's Jet Propulsion Laboratory, Pasadena, CA. "This was the fourth
soft gamma repeater to be observed, but unlike the others we have
studied, this one emitted an exceedingly intense burst of radiation.
We estimate that it released as much energy in a few seconds as the
Sun emits in 300 years." Ulysses is a joint mission of NASA and the
European Space Agency.

SGR1900+14 is a newly discovered type of star called a
"magnetar" - a
dense ball of super-heavy matter about the size of a city, but
weighing more than the Sun. Objects in this class have the greatest
magnetic fields known in the universe. A magnetar is so intense that
it powers a steady glow of X-rays from the star's surface, often
punctuated by brief, intense gamma-ray flashes and, occasionally, by
catastrophic flares like the one observed on August 27. Astronomers
think that all these effects are caused by an out-of-control magnetic
field -- one capable of heating, mixing and sometimes cracking the
star's rigid surface.

Using several spacecraft detectors, including the Ulysses gamma
ray
burst instrument, scientists were able to measure this extremely rare
event and pinpoint the precise source of the explosion with
unprecedented clarity.

"The star, which has an extremely strong magnetic field,
appears to
have experienced a 'star quake' so powerful that it created a
temporary ionosphere on the night side of Earth and sent two
spacecraft into protective safe modes," Smith said.

Data from the Ulysses experiment, showed radiation counts that
rocketed from background (near zero) levels to several thousand
electrons per second. Dr. Kevin Hurley of the University of
California, Berkeley, who is principal investigator of the gamma ray
burst experiment on Ulysses, reported that energy measurements were
two times greater than any other recorded burst.

"The radiation, as seen by the gamma ray burst detector, spiked
quickly and soon settled into a series of ever-smaller spikes that
clearly revealed the neutron star's rotational period," Hurley
reported at a NASA science press briefing on September 29. "The star
reminded us of a dying lighthouse. It kept rotating, but the lamp
steadily faded away."

Hurley, who had been part of a team observing the star,
recorded
pulses or flashes of magnetic radiation emanating from the star every
5.16 seconds using another satellite, known as the Japanese/NASA
Advanced Satellite for Cosmology and Astrophysics (ASCA). Comparisons
of the ASCA data and measurements from other satellites showed that
the X-ray pulses were gradually slowing down after the radiation burst
subsided.

From its intensity and rotational slowing, scientists
calculated that
SGR1900+14 has a magnetic field about a thousand trillion times
stronger than Earth's magnetic field and about one thousand times
stronger than any found elsewhere in the universe, Smith said. During
the flashing episode, Dr. Chryssa Kouveliotou of NASA's Marshall Space
Flight Center in Huntsville, AL, who led another team observing the
star with sensitive X-ray detectors aboard NASA's Rossi X-ray Timing
Explorer satellite, found faint X-rays coming from the star, similar
to what they had observed in another soft gamma repeater which turned
out to be a magnetar.

Three of the four confirmed soft gamma repeaters - designated
1900+14, 1806-20 and 0526-66 -- have localized X-ray emissions;
1806-20 and 1900+14 have regular pulsations and 0526- 66 had an
eight-second period during its magnetic explosion observed in 1979. It
is by comparing the change in the rotational period of these stars
across several observations that scientists can measure their magnetic
fields.

"Magnetars seem to answer several mysteries about the structure
and
evolution of stars," said Kouveliotou. "We think magnetars spend their
first 10,000 years as soft gamma repeaters. As they weaken with age
and slow their rotation, they become anomalous X-ray pulsars -- stars
that do not have enough 'juice' to flash anymore, but which emit a
steady flow of X-rays for perhaps another 30,000 years. After that,
they fade to black and drift for eternity through the heavens. The
absence of observable pulsars in some supernova remnants just means
that the pulsar's lights have gone out sooner than we expected."

Additional information on magnetars or the August 27 burst is
available on the Internet at http://www1.msfc.nasa.gov/NEWSROOM/ and
http://www.magnetars.com/

The Ulysses mission to study the poles of the Sun is managed
jointly
by NASA and the European Space Agency. The Jet Propulsion Laboratory
manages the U.S. portion of the mission for NASA's Office of Space
Science, Washington, DC. JPL is a division of the California Institute
of Technology, Pasadena, CA.

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