Finally, You Can Witness the Explosion of a Cosmic Supernova With Your Own Eyes
A mysterious “hand” stretching through the cosmos has just revealed fresh information on how huge stars die horrible deaths.
The magnificent structure is the ejecta from a core-collapse supernova, and astronomers have been able to see it explode into space at almost 4,000 kilometers (2,485 miles) per second by taking photos of it over a 14-year period.
At the tips of the “fingers” the supernova remnant and blast wave dubbed MSH 15-52 are smashing into a cloud of gas dubbed RCW 89, generating shocks and knots in the material and causing the expanding supernova to slow down.
MSH 15-52 is approximately 17,000 light-years from Earth and appears to be one of the Milky Way’s youngest supernova remnants.
Around 1,700 years ago, light from the stellar explosion reached Earth as the progenitor star ran out of fuel for fusion, bursting its outer material into space and collapsing its core.
This collapsing core became a sort of “dead” star known as a pulsar, an extraordinarily dense object with neutrons packed so closely together that they exhibit some of the features of an atomic nucleus, pulsing light from its poles as it rotates at a fast rate of speed.
This spinning also contributes to the shaping of the X-ray nebula, which is composed of expelled star material extending into space.
The rate at which it is expanding has been detailed in a new study, which examines changes in RCW 89 as the supernova remnant plunges into it using photos from 2004, 2008, and 2017-2018.
We can gain a better picture of the shock wave’s velocity and the knots of ejected star material in MSH 15-52 by measuring the distance traveled by these features over time. This is demonstrated in the figure below.
The blast wave, positioned near one of the hand’s fingertips, is a feature formed by the intersection of MSH 15-52 and RCW 89. It travels at a rate of 4,000 kilometers per second, but some knots of material travel at speeds of up to 5,000 kilometers per second.
These knots are believed to be clumps of magnesium and neon that developed within the star before to the supernova explosion and are travelling at varying speeds. Even the slowest appear incredibly fast, at over 1,000 kilometers per hour.
Nonetheless, as these features interact with the material in RCW 89, they slow down. The distance between the pulsar and RCW 89 is approximately 75 light-years; to span this distance, the mean expansion velocity of MSH 15-52’s outer edge must be 13,000 km/s.
This indicates that the material would have gone through a very low-density cavity or bubble in the gas surrounding the shattered star before coming into contact with RCW 89. This is consistent with the supernova model based on core collapse.
As the precursor star approached the end of its main-sequence life, a tremendous stellar wind would have blown into the surrounding space, depleting the star of hydrogen and forming a massive cavity. Then, when the star’s core eventually shattered in a supernova explosion, the remnants of the star were flung into this comparatively unoccupied region of space.
RCW 89 denotes the cavity’s wall. When MSH 15-52 collided with this denser zone, it experienced a rapid deceleration.
High-velocity supernova ejecta have also been observed in the supernova remnant Cassiopeia A, located 11,000 light-years away. This is likewise believed to have been a core-collapse supernova, but we detected it much more recently – the explosion’s light reached Earth only 350 years ago.
We do not yet understand the origin of the fast-moving aggregates in either supernova, but collecting further data and studying such explosions over a longer time period will aid scientists in painstakingly piecing together the puzzle.
The Astrophysical Journal Letters published the research.