Astronomers spot a completely new type of supernova explosion

The death of a massive star and the birth of a compact neutron star binary.

The three panels represent moments before, during, and after the faint supernova iPTF14gqr, visible in the middle panel, appeared in the outskirts of a spiral galaxy located 920 million light years away. The massive star that died in the supernova left behind a neutron star in a very tight binary system. These dense stellar remnants will ultimately spiral into each other and merge in a spectacular explosion, giving off gravitational and electromagnetic waves. Credit: SDSS/Caltech/Keck
The three panels represent moments before, during, and after the faint supernova iPTF14gqr, visible in the middle panel, appeared in the outskirts of a spiral galaxy located 920 million light years away. The massive star that died in the supernova left behind a neutron star in a very tight binary system. These dense stellar remnants will ultimately spiral into each other and merge in a spectacular explosion, giving off gravitational and electromagnetic waves. Credit: SDSS/Caltech/Keck

Astronomers at the Caltech have recently observed the peculiar death of a massive star that exploded in a surprisingly faint and rapidly fading supernova.

These perceptions recommend that the star has an unseen companion, gravitationally siphoning without end the star’s mass to abandon a stripped star that exploded in a quick supernova. The blast is accepted to have brought about a dead neutron star orbiting around its thick and compact companion, recommending that, out of the blue, researchers have seen the introduction of a minimal neutron star binary system.

When a massive star—at least eight times the mass of the sun—runs out of fuel to burn in its core, the core collapses inwards upon itself and then rebounds outward in a powerful explosion called a supernova. After the explosion, all of the star’s outer layers have been blasted away, leaving behind a dense neutron star—about the size of a small city but containing more mass than the sun. A teaspoon of a neutron star would weigh as much as a mountain.

Mansi Kasliwal (MS ’07, PhD ’11), assistant professor of astronomy said, “We saw this massive star’s core collapse, but we saw remarkably little mass ejected. We call this an ultra-stripped envelope supernova and it has long been predicted that they exist. This is the first time we have convincingly seen core collapse of a massive star that is so devoid of matter.”

The fact that the star exploded at all implies that it must have previously been enveloped in lots of material, or its core would never have become heavy enough to collapse. But where, then, was the missing mass?

The specialists inferred that the mass more likely than not been stolen—the star must have some sort of dense, compact companion, either a white smaller person, neutron star or dark gap—close enough to gravitationally siphon away its mass before it exploded. The neutron star that was abandoned from the supernova must have then been naturally introduced to orbit with that dense companion. Observing iPTF 14gqr was really observing the introduction of a smaller neutron star binary. Since this new neutron star and its partner are so close together, they will, in the long run, converge in an impact like the 2017 occasion that delivered both gravitational waves and electromagnetic waves.

Not exclusively is iPTF 14gqr an outstanding occasion, the way that it was seen at all was chance since these marvels are both uncommon and brief. For sure, it was just through the observations of the supernova’s initial stages that the specialists could derive the blast’s starting points as a massive star.

De said, “You need fast transient surveys and a well-coordinated network of astronomers worldwide to really capture the early phase of a supernova. Without data in its infancy, we could not have concluded that the explosion must have originated in the collapsing core of a massive star with an envelope about 500 times the radius of the sun.”

The event was first seen at Palomar Observatory as part of the intermediate Palomar Transient Factory (iPTF), a nightly survey of the sky to look for transient, or short-lived, cosmic events like supernovae. Because the iPTF survey keeps such a close eye on the sky, iPTF 14gqr was observed in the very first hours after it had exploded. As the earth rotated and the Palomar telescope moved out of range, astronomers around the world collaborated to monitor iPTF 14gqr, continuously observing its evolution with a number of telescopes that today form the GROWTH network of observatories.

The Zwicky Transient Facility, the successor of iPTF at Palomar Observatory, is examining the sky even more broadly and frequently in the hopes of catching more of these rare events, which make up only one percent of all observed explosions. Such surveys, in partnership with coordinated follow-up networks like GROWTH, will enable astronomers to better understand how compact binary systems evolve from binary massive stars.

The research was primarily funded by the National Science Foundation under the PIRE GROWTH project. A full list of funding sources and co-authors can be found in the Science study, titled “A hot and fast ultra-stripped supernova that likely formed a compact neutron star binary.” In addition to De and Kasliwal, other Caltech co-authors are Gary Doran of the Jet Propulsion Laboratory; graduate student Gina Duggan; Shri Kulkarni, George Ellery Hale Professor of Astronomy and Planetary Science; and Russ Laher and Frank Masci of Caltech’s Infrared Processing and Analysis Center.

The research was led by graduate student Kishalay De and is described in a paper appearing in the October 12 issue of the journal Science.