V1647 Ori resides 1300 light-years away in McNeil’s Nebula. It is a young Sun-like star spinning at high speed and spewing out super-hot plasma and astronomers have now been able to deduce what might be happening behind the dusty disc cloaking the star. 

Three telescopes, XMM-Newton, Chandra, and Suzaku, have kept their eyes on it during two multi-year outbursts. The first lasted from 2003 to 2006; the second has been under way since 2008.  During these extended outbursts the star displays faster growth in mass, a surge in X-ray emission and a dramatic increase in temperature to 50 million degrees celsius.

Stars like V1647 Ori form from clouds of gas and dust, which collapse under gravity and develop a dense protostar at their center, surrounded by the remaining orbiting disc of gas and dust. The protostar continues to grow as material in the disc works its way towards the center and falls onto the newborn star at speeds of up to a few hundred miles per second. However, rather than falling onto the protostar, some of the material is ejected in the form of high-speed jets emanating from the north and south poles of the star. These jets can be highly variable, pointing to energetic activity in the innermost regions but the thick gas and dust envelope surrounding the central star makes it hard to see what is going on.

Enter the X-ray vision of three space telescopes. 



“We think that magnetic activity on or around the stellar surface creates the super-hot plasma,” says Kenji Hamaguchi, lead author of the paper. “This behaviour could be sustained by the continual twisting, breaking, and reconnection of magnetic fields, which connect the star and the disc, but which rotate at different speeds. Magnetic activity on the stellar surface could also be caused by accretion of material onto it.” 

In addition, another variation in X-ray emission was found to repeat regularly, with a period around just one day.  For a star of V1647 Ori’s size, this implies that it is spinning as fast as it can without ripping itself to pieces. At the same time, matter falls onto the star in large pancake-shaped hotspots on opposite sides of the stellar surface. 

 “We think the super-hot plasma is located on the surface of the star, which rotates with a one day period,” says Hamaguchi. “The rising and falling in flux that we see would probably be due to the emergence and disappearance of the bright hot spot in our line of sight.” 

Yet the regular heartbeat of X-ray emission seen at various times between 2004 to the present day suggest that despite the chaotic behavior, the large-scale configuration of the star–disc system remains stable over timescales of several years.


Citation: “X-raying the Beating Heart of a Newborn Star: Rotational Modulation of High-energy Radiation from V1647 Ori” by K. Hamaguchi et al. Astrophysical Journal, vol. 754, 20 July 2012.