X-ray observations have revealed something curious about the young star that illuminates McNeil’s Nebula, a glowing jewel of cosmic dust in the Orion constellation: The object is a protostar rotating once a day, or 30 times faster than the sun. The stellar baby also has distinct birthmarks—two X-ray-emitting spots, where gas flows from a surrounding disk, fueling the infant star.
The young star, V1647 Orionis, first made news in early 2004, when it erupted and lit up McNeil’s Nebula, located 1,300 light years away in a region of active star formation within the constellation of Orion. The initial outburst died down in early 2006, but then V1647 Ori erupted again in 2008, and has since remained bright.
More recently, astronomers combined 11 observations of V1647 Ori from NASA’s Chandra X-ray Observatory, the Japan-led Suzaku satellite, and the European Space Agency’s XMM-Newton to determine the source of the high-energy emission. The team began monitoring the star shortly after its eruption in 2004 and continued to keep watch through 2010, a period covering both eruptions.
Strong similarities among X-ray light curves captured over this six-year period allowed the lead author on the study, Kenji Hamaguchi, astrophysicist at NASA’s Goddard Space Flight Center, to identify cyclic X-ray variations. Hamaguchi and the rest of the team determined the star is rotating once per day, making V1647 among the youngest stars whose spin has been determined using an X-ray-based technique. Results from the study will appear in the paper “X-raying the Beating Heart of a Newborn Star: Rotational Modulation of High-energy Radiation from V1647 Ori,” in the July 20 issue of The Astrophysical Journal.
“The observations give us a look inside the cradle at a very young star,” says co-author Joel Kastner, a professor of imaging science and astronomical sciences and technology at Rochester Institute of Technology. “It’s as though we’re able to see its beating heart. We’re actually able to watch it rotate. We caught the star at a point where it is rotating so fast as it gains material that it’s barely able to hold itself together. It’s rotating at near break-up speed.”