The Stellar Object on its Way Out of Our Galaxy

A Binary Star System of Sirius A and Sirius B. Sirius B is a white dwarf, which is left over remnants from a large star and has exhausted its nuclear fusion

Post Author - J. Carlin Decker III

Have you ever wanted to leave a party quickly? While our Irish goodbyes may seem fast, it pales in comparison to how speedy CWISE J1249 is making its exit from the galaxy at one million miles per hour. A group of citizen scientists from the Backyard Worlds: Planet 9 program noticed this extremely fast-moving body a few years ago and labeled it CWISE J124909.08+362116.0. Follow-up observations from a variety of ground-based locations have been made to help classify CWISE J1249, and the initial citizen scientists are cited as co-authors in the published discovery.

The team believes CWISE J1249 to be either a lower-mass star or a brown dwarf—a substellar object that is slightly larger than the biggest gas giants, but has less mass than the smallest stars. Another unique property is that CWISE J1249 has much less iron and metals than other stars and dwarves, which suggests it is very old, possibly from one of the first stars in the galaxy. 

Size comparisons of different stellar objects relative to our own solar system

In terms of how the object is traveling so fast and on its intergalactic course the team has two hypotheses. The first is that CWISE J1249 was part of a binary system, a pair of stars locked in orbit with each other. One of these stars, a faint white dwarf, pulled too much material from the other and exploded, which launched CWISE J1249 away at high speeds. The other hypothesis is that it was part of a cluster of stars that encountered a pair of black holes, which separated CWISE J1249 from the cluster and sent it soaring out of the Milky Way. 

The various teams of researchers, volunteers, and students will continue to examine the composition of CWISE J1249 to determine its true source and continue to observe the route of its intergalactic journey. This discovery might be one of many high velocity, low mass objects traveling speedily through our galaxy