- 4324 - BLACKHOLE - or neutron star detected? - The supernova observed is “SN 2022jli” This occurred when a massive star died in a fiery explosion, leaving behind a compact object which is a neutron star or a black hole.
-------------------- 4324 - BLACKHOLE - or neutron star detected?
- This dying star
had a companion which was able to survive this violent event. The periodic
interactions between the compact object and its companion left periodic signals
in the data, which revealed that the supernova explosion had indeed resulted in
a compact object.
-
- The explosive
deaths of supermassive stars, supernovae,
lead to the creation of black holes or neutron stars? At least, that’s
the evolutionary path that astronomers suggest happens. And, these compact
objects exist throughout the Universe. But, no one’s ever seen the actual birth
process of a neutron star or black hole in action before.
-
- That changed when
supernova “SN 2022jli“ occurred in the
nearby galaxy “NGC 157”. This catastrophic star death event was discovered in
May 2022. Observations were made from
the European Southern Observatory’s Very Large Telescope and New Technology
Telescope provided high-quality light-curve measurements.
-
- The supernova
explosion ended up creating a massive compact object. Until now, no one has observed the process
happen in (almost) real-time. That makes the light curve a useful window on the
creation of either a neutron star or a black hole.
-
- Astronomers wanted
to establish a direct connection between the death of a massive supergiant star
and the creation of the object. In “SN
2022jli” data there was a repeating
sequence of brightening and fading.
This is the first time that repeated periodic oscillations, over many
cycles, have been detected in a supernova light curve.
-
- Supernovae occur
pretty frequently in the Universe. Astronomers study them and chart how their
brightness changes over time. After the initial explosion, the light it
generates fades out over some time. Usually, it’s a smooth change in the light
curve. But, SN 2022jli didn’t fit the “normal” curve. Instead of fading out
smoothly, the brightness of light from the explosion oscillated in a
12-day-long period.
-
- A rapidly
spinning neutron star (a pulsar) at its heart, surrounded by material rushing
out from the site of the explosion. SN
2022jli could have either a neutron star or a black hole orbiting with a
companion star.
-
- What story does SN
2022jli’s strange light curve tell us about the creation of black holes or
neutron stars? The explosion itself
was a fine example of what astronomers call “Type II supernovae”. At the end of its life, a supermassive star
collapses and then explodes outward. The remaining core collapses further to
create one of two types of massive objects.
-
- A neutron star is
one. It’s what’s left over after the rapidly collapsing core of the star
crushes the remaining protons and neutrons of matter into neutrons. It’s
essentially a ball of neutrons. Most neutron stars have about the mass of the
Sun crushed inside themselves. But, they are small compared to their progenitor
stars. Most are 20 kilometers across.
-
- Stellar-mass black
holes also come from the deaths of supermassive stars that were at least 20
times the mass of the Sun or more. The core collapses during the event, the
same as with a neutron star. But, the mass is so great that the event creates a
black hole, crushing all the leftover core material into a pinpoint of dense
matter.
-
- Like many massive
stars, the progenitor of SN 2022jli appears to have had at least one companion
star. It probably survived the supernova explosion. The outburst threw out huge
amounts of material, and the companion star interacted with it. That caused its
atmosphere to “puff up”.
-
- The newly created
compact object passes through the orbit of the star and sucks hydrogen gas away
from the star. That material funnels into an accretion disk around the compact
object. Those periodic episodes of matter theft from the star release lots of
energy, which gets picked up as regular changes of brightness in the light
curve measurements as well as the gamma-ray signals.
-
- We can’t see light
coming from the compact object itself, whether it’s a neutron star or a black
hole. But, we do see radiation from the heated material drawn into the
accretion disk around the compact object. And, since astronomers were able to
track the changes in the light curve due to activity by the massive object, it
amounted to watching its formation.
-
- Exactly what
astronomers saw being formed? Was it a
neutron star with tremendously strong magnetic fields and gravity, or a black
hole with gravity so strong nothing (not even light) could escape it? What do you think?
-
-
January 21, 2023 BLACKHOLE - or
neutron star detected? 4324
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