NASA Telescopes Discover Strobe-Like Flashes In A Suspected Binary Protostar

Thu Feb 7, 2013 1:05pm EST

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WASHINGTON,  Feb. 7, 2013  /PRNewswire-USNewswire/ -- Two of NASA's great
observatories, the Spitzer and Hubble space telescopes, have teamed up to
uncover a mysterious infant star that behaves like a strobe light.

(Logo:  http://photos.prnewswire.com/prnh/20081007/38461LOGO)  

Every 25.34 days, the object, designated LRLL 54361, unleashes a burst of light.
Although a similar phenomenon has been observed in two other young stellar
objects, this is the most powerful such beacon seen to date.

The heart of the fireworks is hidden behind a dense disk and envelope of dust.
Astronomers propose the light flashes are caused by periodic interactions
between two newly formed stars that are binary, or gravitationally bound to each
other. LRLL 54361 offers insights into the early stages of star formation when
lots of gas and dust is being rapidly accreted, or pulled together, to form a
new binary star.

Astronomers theorize the flashes are caused by material suddenly being dumped
onto the growing stars, known as protostars. A blast of radiation is unleashed
each time the stars get close to each other in their orbits. This phenomenon,
called pulsed accretion, has been seen in later stages of star birth, but never
in such a young system or with such intensity and regularity.

"This protostar has such large brightness variations with a precise period that
it is very difficult to explain," said  James Muzerolle  of the Space Telescope
Science Institute in  Baltimore, Md.  His paper recently was published in the
science journal Nature.

Discovered by NASA's Spitzer Space Telescope, LRLL 54361 is a variable object
inside the star-forming region IC 348, located 950 light-years from Earth. Data
from Spitzer revealed the presence of protostars. Based on statistical analysis,
the two stars are estimated to be no more than a few hundred thousand years old.

The Spitzer infrared data, collected repeatedly during a period of seven years,
showed unusual outbursts in the brightness of the suspected binary protostar.
Surprisingly, the outbursts recurred every 25.34 days, which is a very rare
phenomenon.  

Astronomers used NASA's Hubble Space Telescope to confirm the Spitzer
observations and reveal the detailed stellar structure around LRLL 54361. Hubble
observed two cavities above and below a dusty disk. The cavities are visible by
tracing light scattered off their edges. They likely were blown out of the
surrounding natal envelope of dust and gas by an outflow launched near the
central stars. The disk and the envelope prevent the suspected binary star pair
from being observed directly. By capturing multiple images over the course of
one pulse event, the Hubble observations uncovered a spectacular movement of
light away from the center of the system, an optical illusion known as a light
echo.

Muzerolle and his team hypothesized the pair of stars in the center of the dust
cloud move around each other in a very eccentric orbit. As the stars approach
each other, dust and gas are dragged from the inner edge of a surrounding disk.
The material ultimately crashes onto one or both stars, which triggers a flash
of light that illuminates the circumstellar dust. The system is rare because
close binaries account for only a few percent of our galaxy's stellar
population. This is likely a brief, transitory phase in the birth of a star
system.  

Muzerolle's team next plans to continue monitoring LRLL 54361 using other
facilities including the European Space Agency's Herschel Space Telescope. The
team hopes to eventually obtain more direct measurements of the binary star and
its orbit.  

For related images and video, visit:

http://hubblesite.org/news/2013/04

For more information on Hubble visit:  

www.nasa.gov/hubble

http://hubblesite.org/

For more information on Spitzer, visit:

www.nasa.gov/spitzer

SOURCE  NASA


J.D. Harrington, Headquarters, Washington, 202-358-5241,
j.d.harrington@nasa.gov; or Ray Villard, Space Telescope Science Institute,
Baltimore, Md., 410-338-4514, villard@stsci.edu

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