Salving a Cosmic Mystery

Daniel Wik, assistant professor of physics and astronomy, helped conclude a study using data from NASA’s NuSTAR space telescope to confirm that Eta Carinae, the most luminous and massive stellar system within 10,000 lightyears, is accelerating particles to ultra-high energies. Some of the particles could reach Earth as cosmic rays.

“The key to accurately measuring Eta Carinae’s X-rays and identifying the star system as the gamma ray source—and thus proving that the colliding winds of this binary system are accelerating cosmic rays—was to fully characterize NuSTAR’s background,” said Wik.

Wik previously developed a multi-component background model for the NuSTAR mission, but Eta Carinae’s location in the plane of the Milky Way caused the background of NuSTAR’s nine separate observations to be more complicated than usual. He helped identify additional sources of background and how to account for them, allowing the link between Eta Carinae’s X-ray and gamma ray emissions to become clear.

Eta Carinae, located about 7,500 light-years away, contains a pair of massive stars whose eccentric orbits bring them unusually close to Earth every 5.5 years. The two stars contain 90- and 30-times the mass of our Sun, and they pass 140 million miles apart at their closest approach—about the average distance between Mars and the Sun.

Adapted from an original release written by Francis Reddy of NASA’s Goddard Space Flight

Center, available here: https://go.nasa.gov/2knv825.Eta Carinae’s great eruption in the 1840s created the billowing Homunculus Nebula, imaged here by Hubble. Now about a light-year long, the expanding cloud contains enough material to make at least 10 copies of our Sun. Astronomers cannot yet explain what caused this eruption.