Rare Strobe-like Starsystem Contains Baby Binary Protostars

First Posted: Feb 08, 2013 12:02 AM EST

A star system discovered by the Spitzer and Hubble space telescopes blinking like a strobe light is the subject of a study explaining the phenomenon. The object, designated LRLL 54361, unleashes a burst of light every 25.34 days. Although a similar phenomenon has been observed in two other young stellar objects, this is the most powerful such beacon seen to date.

This could be easy if the heart of the fireworks weren't hidden behind a dense disk and envelope of dust. Astronomers now propose that the light flashes are caused not by one, but 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, who published his paper in the 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.

Astronomers used NASA's Hubble Space Telescope to confirm the Spitzer infrared observations of the flashes repeating in the very rare pattern and reveal the detailed stellar structure around LRLL 54361. Hubble observed two cavities above and below a dusty disk which are visible by tracing light scattered off their edges and were likely blown out of the surrounding natal envelope of dust and gas by an outflow launched near the central stars.

Muzerolle and his team also think that 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 eventually crashes into one or both stars, which triggers a flash of light that illuminates the circumstellar dust. The system is rare, with binaries accounting for only a few percent of our galaxy's stellar population. The assumption is therefore that the observed state is only a brief, transitory phase in the birth of a star system.

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