- 4369 - SUPERNOVA 1987 - Using the James Webb Space Telescope (JWST), astronomers have ended a nearly decade-long game of celestial hide-and-seek after they discovered a neutron star in the wreckage of a stellar explosion.
------------------- 4369 - SUPERNOVA 1987
- Supernova 1987A
represents the remains of an exploded star that once had a mass around 8 to 10
times that of the sun. It is located around 170,000 light-years away in the
Large Magellanic Cloud, a dwarf galaxy neighbor of the Milky Way.
-
- Supernova 1987A
was first spotted by astronomers 37 years ago in 1987. As it exploded, Supernova 1987A first
showered Earth with ghostly particles called neutrinos and then became visible
in bright light. This made it the nearest and brightest supernova seen in the
night sky over Earth for around 400 years.
-
- Supernova
explosions such as this are responsible for seeding the cosmos with elements
like carbon, oxygen, silicon and iron. These elements ultimately become the
building blocks of the next generation of stars and planets, and can even form
molecules that may one day become integral to life as we know it.
-
- These explosions
also birth compact stellar remnants either in the form of neutron stars or
black hole. For 37 years, astronomers
haven't known which of these may lurk at the heart of Supernova 1987A.
-
- Neutron stars are
born when massive stars exhaust their fuel supplies needed for nuclear fusion
happening at their cores. This cuts off the outward energy flowing from these
stars' cores that protects them from collapsing under their own gravity.
-
- As a stellar core
collapses, tremendous supernova explosions rip through the star's outer layers,
blasting them away. This leaves behind a "dead" star as wide as the
average city here on Earth, but with a mass around one or two times that of the
sun. The star ends up composed of a
fluid of neutron particles, which is the densest known matter in the universe.
-
- Neutron stars are
supported against complete collapse by quantum effects occurring between
neutrons in their interiors. These effects prevent the neutrons from cramming
together. This so-called "neutron degeneracy pressure" can be
overcome if a stellar core has enough mass, or if a neutron star, after its
creation, piles on more mass. This would result in the birth of a black hole.
-
- Scientists have
been fairly sure that the object in Supernova 1987A is a neutron star, but they
couldn't rule out the possibility that this newly deceased star, at least as we
see it 170,000 or so years ago, hadn't gathered the mass to transform itself
into a black hole.
-
- One other
possibility was that the infalling matter could have been accreted onto the
neutron star and caused it to collapse into a black hole. So, a black hole was
a possible alternative. The spectrum
that infalling material produces is not the right type of spectrum to explain
the emission that we see.
-
- The newly
identified neutron star had avoided detection for 37 years due to the fact
that, as a newborn, it was still surrounded by a thick shroud of gas and dust
launched during the supernova blast that signaled the death throes of its
progenitor star.
-
- Detection has been
hindered by the fact that the supernova condensed about half a solar mass of
dust in the ensuing years after the explosion.
This dust acted as a screen-obscuring radiation from the center of
Supernova 1987A.
-
- The dust is far
less effective at blocking infrared light than it is at blocking visible light.
So, to see through this death shroud and into the heart of Supernova 1987A,
astronomers used the highly sensitive infrared eye of the JWST, particularly
the telescope's Mid-Infrared Instrument and Near-Infrared Spectrograph.
-
- The smoking gun
evidence for this hidden neutron star had to do with emissions from the
elements argon and sulfur coming from the center of Supernova 1987A. These
elements are ionized, meaning they have had electrons stripped from their
atoms. This ionization could have only
occurred due to radiation emitted by a neutron star.
-
- The emissions
enabled them to put a limit on the brightness or luminosity of the once-hidden
neutron star. They determined it to be around a tenth of the brightness of the
sun.
-
- The ionization of
argon and sulfur that served as their smoking gun could have been caused by a
neutron star in one of two ways. Winds of charged particles dragged along and
accelerated to near light speed by a rapidly rotating neutron star could have
interacted with surrounding supernova material, causing the ionization. Or,
ultraviolet and X-ray light emitted by the million-degree surface of the hot
neutron star could have stripped electrons away from atoms at the heart of this
stellar wreckage.
-
- If the former
scenario is the right one, then the neutron star at the heart of Supernova
1987A is actually a pulsar surrounded by a pulsar wind nebula. Pulsars are spinning neutron stars. If the latter
scenario is the right recipe for these emissions, however, this close supernova
birthed a "bare" or "naked" neutron star, the surface of
which would be exposed directly to space.
-
- We have a program
which will be getting data with 3 or 4 times the resolution in the
near-infrared. So by obtaining these new
data, we may be able to distinguish the 2 models that have been proposed to
explain the emission powered by a neutron star.
-
-
February 27, 2024 SUPERNOVA 1987 4369
------------------------------------------------------------------------------------------
- Comments appreciated and Pass it on to whomever is
interested. --------
--- Some reviews are
at: -------------- http://jdetrick.blogspot.com -----
-- email feedback,
corrections, request for copies or Index of all reviews
--- to: ------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- ---
Wednesday, February 28, 2024 ---------------------------------
No comments:
Post a Comment