- 4189 - SUPERNOVA EXPLOSION - discovered early? The massive star, in the final year of its life, ejected large amounts of matter into space before going supernova. This massive star exploded in the Pinwheel Galaxy in May, 2023. It appears to have unexpectedly lost approximately one sun's worth of ejected mass during the final years of its life before going supernova.
----------------- 4189 - SUPERNOVA EXPLOSION - discovered early?
- This star had
exploded in the nearby Pinwheel Galaxy (Messier 101), which is just 20 million
light-years away in the constellation of Ursa Major, the Great Bear. Amateur
astronomers around the world started gazing at “SN 2023ixf” because the
Pinwheel in general is a popular galaxy to observe.
-
- Astronomers want
to understand exactly what is happening in the moments immediately after a star
goes supernova. Yet all too often, a supernova is spotted several days after
the explosion took place, so they don’t get to see its earliest stages.
Considering how close, relatively speaking, SN 2023ixf was to
us and how early it was identified, it was a prime candidate for close study.
-
- Alerted to the
supernova astronomers began measuring the supernova's light spectrum, and how
that light changed over the coming days and weeks. When plotted on a graph,
this kind of data forms a "light curve."
- The light curve
spectrum from SN 2023ixf showed that it was a type II supernova, a category of
supernova explosion involving a star with more than eight times the mass of the
sun. In the case of SN 2023ixf, searches in archival images of the Pinwheel
suggested the exploded star may have had a mass between 8 and 10 times that of
our sun.
-
- The spectrum was
also very red, indicating the presence of lots of dust near the supernova that
absorbed bluer wavelengths but let redder wavelengths pass. This was all fairly
typical, but what was especially extraordinary was the shape of the light
curve.
-
- Normally, a type
II supernova experiences what astronomers call a 'shock breakout' very early in
the supernova's evolution, as the blast wave expands outwards from the interior
of the star and breaks through the star's surface. Yet a bump in the light
curve from the usual flash of light stemming from this shock breakout was
missing. It didn’t turn up for several
days. Was this a supernova in slow motion.
-
- The delayed shock
breakout is direct evidence for the presence of dense material from recent mass
loss. Observations revealed a
significant and unexpected amount of mass loss, close to the mass of the sun,
in the final year prior to explosion.
-
- This unstable star
was puffing off huge amounts of material from its surface. This creates a dusty
cloud of ejected stellar material all around the doomed star. The supernova
shock wave therefore not only has to break out through the star, blowing it
apart, but also has to pass through all this ejected material before it becomes
visible. This took several days.
-
- Massive stars
often shed mass, just look at Betelgeuse over late 2019 and early 2020, when it
belched out a cloud of matter with ten times the mass of Earth’s moon that
blocked some of Betelgeuse’s light, causing it to appear dim. However,
Betelgeuse isn’t ready to go supernova just yet, and by the time it does, the
ejected cloud will have moved far enough away from the star for the shock
breakout to be immediately visible. -
- In the case of SN
2023ixf, the ejected material was still very close to the star, meaning that it
had only recently been ejected, and astronomers were not expecting that. Astronomers were able to see the collision
between the supernova shockwave and the circumstellar cloud.
-
- We can think of an
evolved massive star as being like an onion, with different layers. Each layer
is made from a different element, produced by sequential nuclear burning in the
star's respective layers as the stellar object ages and its core contracts and
grows hotter.
-
- The outermost
layer is hydrogen, then you get to helium. Then, you go through carbon, oxygen,
neon and magnesium in succession until you reach all the way to silicon in the
core. That silicon is able to undergo nuclear fusion reactions to form iron,
and this is where nuclear fusion in a massive star’s core stops. Iron requires more energy to be put into the
reaction than comes out of it.
-
- Thus the core
switches off, the star collapses onto it and then rebounds and explodes
outwards.
-
- The final stages of
burning high-mass elements inside the star, such as silicon (which is used up
in the space of about a day), is disruptive, causing pulses of energy that
shudder through the star and lift material off its surface.
-
- Amateur
astronomers around the world started gazing at SN 2023ixf because the Pinwheel
in general is a popular galaxy to observe.
Astronomers measured the supernova's light spectrum, and how that light
changed over the coming days and weeks.
-
- This "light
curve." spectrum from SN 2023ixf showed that it was a type II supernova
. This is a category of supernova
explosion involving a star with more than eight times the mass of the sun. In
the case of SN 2023ixf, searches in archival images of the Pinwheel suggested
the exploded star may have had a mass
between 8 and 10 times that of our sun.
-
- The spectrum was
also very red, indicating the presence of lots of dust near the supernova that
absorbed bluer wavelengths but let redder wavelengths pass. This was all fairly
typical, but what was especially extraordinary was the shape of the light
curve.
-
- An unstable star
puffing off huge amounts of material from its surface creates a dusty cloud of
ejected stellar material all around the doomed star. The supernova shock wave therefore not only has
to break out through the star, blowing it apart, but also has to pass through
all this ejected material before it becomes visible.
-
-
October 15, 2023 SUPERNOVA EXPLOSION
- discovered early? 4189
------------------------------------------------------------------------------------------
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Sunday, October 15, 2023 ---------------------------------
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