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Neutron star smash-up: Jet hits a roadblock

Collision of two neutron stars

On Aug. 17, 2017, observatories around the world witnessed the collision of two neutron stars. At first, many scientists thought a narrow high-speed jet, directed away from our line of sight, or off-axis, was produced (diagram at left). But observations made at radio wavelengths now indicate the jet hit surrounding material, producing a slower-moving, wide-angle outflow, dubbed a cocoon (pink structure at right.

More about this image
Millions of years ago, a pair of extremely dense stars, called neutron stars, collided in a violent smash-up that shook space and time. On Aug. 17, 2017, both gravitational waves -- ripples in space and time -- and light waves emitted during that neutron star merger finally reached Earth. The gravitational waves came first and were detected by the twin detectors of the National Science Foundation (NSF)-funded Laser Interferometry Gravitational-wave Observatory (LIGO), aided by the European Virgo observatory. The light waves were observed seconds, days and months later by dozens of telescopes on the ground and in space.

Now, scientists from Caltech and several other institutions are reporting that light with radio wavelengths continues to brighten more than 100 days after the Aug. 17 event. These radio observations indicate that a jet, launched from the two neutron stars as they collided, is slamming into surrounding material and creating a slower-moving, billowy cocoon.

This research was funded by NSF (grants CCF 07-28703 and CCF 08-32824).

To learn more about this research, see the Caltech news story Update on neutron star smash-up: Jet hits a roadblock. (Date image taken: May 2011; date originally posted to NSF Multimedia Gallery: Dec. 27, 2017)

Credit: Lulu Qian, California Institute of Technology

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