Strange Ring Found Circling a Dead Star

NASA’s Spitzer Space Telescope has detected an unusual ring of material surrounding the magnetic remains of a blasted star. The stellar ‘corpse’, called SGR 1900+14, belongs to a class of objects known as magnetars, which are the cores of massive stars that blew up in supernova explosions. The new discovery may help scientists figure out whether a star’s mass determines if it becomes a magnetar when it dies.

Rings and spheres are quite common in the universe. Young, hot stars ‘blow’ bubbles in space, carving out dust into spherical shapes. When stars die in supernova explosions, their remains are blasted into space, forming short-living beautiful orbs called supernova remnants. Another way rings form is around exploded stars, whose expanding shells of debris ram into pre-existing dust rings, causing the dust to glow; that is the case with the supernova remnant, called 1987A. However, the ring around the magnetar SGR 1900+ raises several questions; for one thing, supernova remnants and the ring around 1987A emit X-rays and radio waves, but the ring around SGR 1900+14 only glows at specific infrared wavelengths.

At first, the astronomers thought the ring must be an infrared echo. These occur when an object sends out a blast wave that travels outward, heating up dust and causing it to glow with infrared light. However, a closer observation of the SGR 1900+14 indicated that the ring was not moving outward as it should have been were it an infrared echo. A second analysis of the pictures revealed that the ring is most likely a carved-out cavity in a dust cloud, a rare phenomenon which has not been seen before.

Stefanie Wachter of NASA’s Spitzer Science Center at the California Institute of Technology, Pasadena, found the ring by accident; Wachter and her colleagues think that the ring formed in 1998 when a magnetar erupted in a giant flare. They believe the cracking of the magnetar’s crusty surface sent out a flare that excavated a nearby cloud of dust, creating a dusty ring. This ring is oblong, with dimensions of about seven by three light-years. The scientists say that it appears to be flat, but they do not rule out the possibility of a three-dimensional shell.

Magnetars differ from other stars by pulsating with X-rays and having tremendously strong magnetic fields. The discovery of this magnetar ‘corpse’ may shed light on the importance of mass in the process of becoming a magnetar. Although scientists know that stars above a certain mass will “go supernova,” they lack the knowledge needed to predict the creation of a magnetar. According to the science team, the ring demonstrates that SGR 1900+14 belongs to a nearby cluster of young, massive stars. By studying the masses of these nearby stars, the scientists may be able to learn the approximate mass of the original star that exploded and became SGR 1900+14.

“It’s as if the magnetar became a huge flaming torch and obliterated the dust around it, creating a massive cavity,” said Chryssa Kouveliotou, Senior Astrophysicist at NASA’s Marshall Space Flight Center, Huntsville, Alabama. “Then the stars nearby lit up a ring of fire around the dead star, marking it for eternity.” Enrico Ramirez-Ruiz of the University of California, Santa Cruz, elaborates: “The ring has to be lit up by something, otherwise Spitzer wouldn’t have seen it; the nearby massive stars are most likely what’s heating the dust and lighting it up, and this means that the magnetar, which lies at the exact center of the ring, is associated with the massive star-forming region.”

“The universe is a big place and weird things can happen,” said Wachter. “I was flipping through archived Spitzer data of the object, and that’s when I noticed it was surrounded by a ring we’d never seen before.” Ramirez-Ruiz adds: “This magnetar is still alive in many ways; it is interacting with its environment, making a big impact on the young star-forming region where it was born.”

TFOT has been consistently covering NASA’s astronomical findings, including the first “real time” observation of an exploding star and the discovery of the youngest neuron star, made by NASA’s Rossi X-ray Timing Explorer. Other space-related TFOT stories include the confirmation of the leading theory regarding particles’ acceleration close to black holes and Spitzer’s discovery of water vapor inside the accretion disk of a newborn star located approximately 1,000 light-years from Earth.

For more information on the ring found around SGR 1900+14, see NASA’s website.

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