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Gizmorama - March 12, 2014
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GopherArchives****-- Hubble telescope sees nearby galaxy rotating like 'clock in the sky' --*BALTIMORE - U.S. astronomers using the Hubble Space
Telescope say they've precisely measured, for the first
time, the rotation rate of a galaxy. Based on the
clock-like movement of its stars, the central part of a
neighboring galaxy called the Large Magellanic Cloud (LMC)
completes a rotation every 250 million years, the Space
Telescope Science Institute reported Tuesday. Institute
scientist Roeland van der Marel and Nitya Kallivayalil of
the University of Virginia used Hubble to measure the
average motion of hundreds of individual stars in the
galaxy located 170,000 light-years away. Disk-shaped
galaxies like the LMC and our own Milky Way generally
rotate like a carousel. For the past century astronomers
have calculated galaxy rotation rates by observing a
slight shift in the spectrum of stars in the galaxy as
one side of a galaxy's spinning stellar disk moves toward
Earth while stars on the other side are moving away.
"Determining a galaxy's rotation by measuring its
instantaneous back and forth motions doesn't allow one
to actually see things change over time," van der Marel
said. "By using Hubble to study the stars' motions over
several years, we can actually for the first time see a
galaxy rotate in the plane of the sky." Hubble is the
only telescope that can make this kind of observation
because of its sharp resolution, its image stability,
and its 24 years in space, the researchers said. "This
precision is crucial, because the apparent stellar
motions are so small because of the galaxy's distance,"
van der Marel said. "You can think of the LMC as a clock
in the sky, on which the hands take 250 million years to
make one revolution. We know the clock's hands move, but
even with Hubble we need to stare at them for several
years to see any movement."
*-- Distant pulsar seen spewing record-breaking particle jet into space --*GREENBELT, Md. - NASA says its Chandra observatory has
seen a fast-moving pulsar escaping a supernova remnant
and spewing out a record-breaking jet of high-energy
particles. The peculiar behavior of the pulsar tracked
by the Chandra X-ray Observatory can likely be traced
back to its birth in the collapse and subsequent
explosion of a massive star, the space agency said
Tuesday.
Located about 60 light-years away from the center of the
supernova remnant SNR MSH 11-61A in the constellation of
Carina, its estimated speed between 2.5 million and 5
million mph makes it one of the fastest pulsars ever
observed, astronomers said. The pulsar's jet of
high-energy particles is the longest from any object in
the Milky Way galaxy, they said. "We've never seen an
object that moves this fast and also produces a jet,"
Lucia Pavan of the University of Geneva in Switzerland
said. "By comparison, this jet is almost 10 times longer
than the distance between the sun and our nearest star."
Usually, the spin axis and jets of a pulsar point in the
same direction as they are moving, but this pulsar's spin
axis and direction of motion are almost at right angles,
the astronomers said. "With the pulsar moving one way and
the jet going another, this gives us clues that exotic
physics can occur when some stars collapse," study
co-author Gerd Puehlhofer of the University of Tuebingen
said.
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