presentation on the topic supernova and hypernova

1. Deepak Kumar
21213

2. Supernova And
Hypernova

3. What Is a Supernova?

4. One type of supernova is caused by
the “last hurrah” of a dying massive
star. This happens when a star at least
five times the mass of our sun goes out
with a fantastic bang!
Massive stars burn huge amounts of
nuclear fuel at their cores, or centers.
This produces tons of energy, so the
center gets very hot. Heat generates
pressure, and the pressure created by
a star’s nuclear burning also keeps that
star from collapsing.
A star is in balance between two
opposite forces. The star’s gravity tries
to squeeze the star into the smallest,
tightest ball possible. But the nuclear
fuel burning in the star’s core creates
strong outward pressure. This outward
push resists the inward squeeze of
gravity.
What causes a supernova?

5. When a massive star runs out of
fuel, it cools off. This causes the
pressure to drop. Gravity wins out,
and the star suddenly collapses.
Imagine something one million
times the mass of Earth collapsing
in 15 seconds! The collapse
happens so quickly that it creates
enormous shock waves that cause
the outer part of the star to explode!
Usually a very dense core is left
behind, along with an expanding
cloud of hot gas called a nebula. A
supernova of a star more than about
10 times the size of our sun may
leave behind the densest objects in
the universe—black holes.

6. A second type of supernova can
happen in systems where two
stars orbit one another and at least
one of those stars is an Earth-
sized white dwarf. A white dwarf is
what's left after a star the size of
our sun has run out of fuel. If one
white dwarf collides with another
or pulls too much matter from its
nearby star, the white dwarf can
explode. Kaboom! The Crab Nebula
Image credit: NASA, ESA,
A white dwarf pulls
Image credit: STSc

7. How bright are supernovas?
These spectacular events can be so bright that they outshine their entire galaxies
for a few days or even months. They can be seen across the universe.
How common are supernovas?
Not very. Astronomers believe that about two or three supernovas occur each
century in galaxies like our own Milky Way. Because the universe contains so many
galaxies, astronomers observe a few hundred supernovas per year outside our
galaxy. Space dust blocks our view of most of the supernovas within the Milky Way.
What can we learn from supernovas?
Scientists have learned a lot about the universe by studying supernovas. They
use the second type of supernova (the kind involving white dwarfs) like a ruler, to
measure distances in space.
How do scientists study supernovas?
NASA scientists use a number of different types of telescopes to search for and
then study supernovas.
NASA’s NuSTAR spacecraft
Image credit: NASA/JPL-Caltech

8. What Is a Hypernova?
A hypernova (sometimes called a collapsar) is a very
energetic supernova thought to result from an
extreme core-collapse scenario. In this case, a
massive star collapses to form a rotating black
hole emitting twin energetic jets and surrounded by
an accretion disk. It is a type of stellar explosion that
ejects material with an unusually high kinetic
energy, an order of magnitude higher than most
supernovae, with a luminosity at least 10 times
greater.

9. In less than a heartbeat, the rug gets pulled out from
underneath the star, and the whole shebang (a star tens
of times more massive than the sun) collapses in on itself
in a sped-up trainwreck of a supernova explosion,
releasing far more energy than it normally would, thus
resulting in a hypernova.
What causes a supernova?
History
In the 1980s, the term hypernova was used to describe a theoretical
type of supernova now known as a pair-instability supernova. It referred
to the extremely high energy of the explosion compared to typical core
collapse supernovae.[1][2][3] The term had previously been used to
describe hypothetical explosions from diverse events such
as hyperstars, extremely massive population III stars in the early
universe,[4] or from events such as black hole mergers.[5]

10. Properties
Hypernovae are now widely accepted to be supernovae with ejecta
having a kinetic energy larger than about 1045 joule, an order of
magnitude higher than a typical core collapse supernova. The ejected
nickel masses are large and the ejection velocity up to 99% of
the speed of light.
Astrophysical models
Models for hypernova focus on the efficient transfer of energy into the
ejecta. In normal core collapse supernovae, 99% of neutrinos generated
in the collapsing core escape without driving the ejection of material. It is
thought that rotation of the supernova progenitor drives a jet that
accelerates material away from the explosion at close to the speed of
light.
Collapsar model
The collapsar model describes a type of supernova that produces a gravitationally
collapsed object, or black hole. The word "collapsar", short for "collapsed star",
was formerly used to refer to the end product of stellar gravitational collapse,
a stellar-mass black hole. The word is now sometimes used to refer to a specific
model for the collapse of a fast-rotating star

11. Gamma-ray burst progenitors – Types of celestial
objects that can emit gamma-ray bursts
Quark star– Compact exotic star which forms matter
consisting mostly of quarks
Quark-nova – Hypothetical violent explosion resulting from
conversion of a neutron star to a quark star