Hypernova

Some stars have a giant blast.

This blast is called a hypernova. It is much bigger than other star blasts. It is very bright in the sky.

A huge star falls in on itself. This makes a black hole. The black hole sends out two fast jets. These jets move very quickly.

The blast sends out a lot of energy. It can even make light we cannot see. These bursts can last for a long time.

One big blast was seen in 1998. It was much brighter than a normal star blast. It was a very special event to see.

Space is full of big and bright things. Hypernovae are some of the brightest. They are amazing to learn about.

A hypernova is a very big star blast. It is much more powerful than a normal supernova. These blasts are at least ten times brighter than most.

How does a hypernova happen? It starts with a very massive star. The star collapses in on itself. This collapse makes a black hole. This black hole may spin very fast. As it spins, it sends out two jets. These are called astrophysical jets. They are streams of matter that shoot out from the center. These jets move at nearly the speed of light.

Hypernovae also make gamma-ray bursts. These are bright flashes of light. They can last for two seconds or more than a minute. One famous hypernova was seen in 1998. Its name was SN 1998bw. It was 100 times brighter than other star blasts. This event was the first to link a blast to a gamma-ray burst. Scientists study these to learn how stars die. They help us see how much power a star can hold.

A hypernova is a very powerful type of stellar explosion. It is much more energetic than a normal supernova. These explosions are at least ten times brighter than most. They also push out material with huge amounts of energy. Scientists sometimes call them superluminous supernovae. This name describes explosions that are extremely bright. Hypernovae are very important for understanding how massive stars end their lives.

How does this massive explosion work? It often starts with a huge star that is at least 30 times the mass of our Sun. The core of the star collapses inward. This collapse creates a spinning black hole. A disk of matter forms around the black hole. This disk is called an accretion disk. The spinning black hole then shoots out two twin jets of matter. These jets move at nearly the speed of light. They plow through the star and create a giant explosion.

Astronomers have studied these events for many years. In the 1980s, people used the term hypernova for different ideas. By 1997, a satellite named BeppoSAX helped find a gamma-ray burst. Scientists Bloom et al. looked at the data in 1998. They concluded a hypernova likely caused the burst. That same year, astronomer Bohdan Paczyński suggested hypernovae come from fast-spinning stars. Since then, the name has been used for explosions with very high energy.

There are many specific facts about these events. The first observed hypernova was named SN 1998bw. It was 100 times brighter than a standard Type Ib supernova. It was also linked to a gamma-ray burst called GRB 980425. This explosion ejected about 10 solar masses of material. It also released about 0.4 solar masses of nickel. The speed of the ejected material can reach 99% of the speed of light. These events are often linked to long gamma-ray bursts.

Hypernovae help us understand the life of stars. They are part of a process called stellar evolution. We can compare them to other bright events in space. For example, some objects look like hypernovae but are actually different. One such event was named AT2021lwx in 2023. It was likely a huge gas cloud falling into a black hole. Some people even gave it the nickname "Scary Barbie." Studying these bright flashes helps us map the history of our universe.

A hypernova is an exceptionally energetic type of stellar explosion. It represents a more powerful version of a standard supernova. These events are at least ten times more luminous than most supernovae. They also eject material with much higher kinetic energy. This energy is often an order of magnitude greater than typical core collapse supernovae. Scientists sometimes refer to them as superluminous supernovae. However, that term can also include other bright explosions with different origins. Hypernovae are vital for understanding the most massive stars in our universe.

The mechanism behind a hypernova often involves a process called the collapsar model. This model describes the collapse of a rapidly rotating star. It starts when a massive star undergoes core collapse. If the star's core is at least fifteen solar masses, it may collapse into a black hole. In some cases, the explosion energy is too low to expel the outer layers. However, if the star is rotating quickly, the collapse creates a black hole with an accretion disk. This disk is a swirling ring of matter around the black hole. The rotation drives twin astrophysical jets that shoot outward from the center. These relativistic jets plow through the stellar material at nearly the speed of light. This action creates powerful shock waves that detonate the hypernova explosion.

Hypernovae are usually classified as Type Ic supernovae. This means their spectra show no hydrogen and no clear helium features. Instead, they show strong silicon lines. A key feature is the presence of extremely broad spectral lines. These lines indicate that the ejected material has an extremely high expansion velocity. The velocity of this ejected material can reach up to 99% of the speed of light. These explosions are also one mechanism for producing long-duration gamma-ray bursts. These bursts are intense flashes of gamma rays that last from two seconds to over a minute.

Our understanding of hypernovae has changed significantly over time. In the 1980s, the term described theoretical events like pair-instability supernovae. It was also used for hypothetical explosions from hyperstars or black hole mergers. In February 1997, the BeppoSAX satellite traced a gamma-ray burst to a distant galaxy. Researchers Bloom et al. analyzed this data in 1998. They concluded that a hypernova was the likely cause. That same year, Polish astronomer Bohdan Paczyński hypothesized that hypernovae come from rapidly spinning stars. This helped refine the modern definition of the term.

The first observed hypernova was SN 1998bw. This event was 100 times more luminous than a standard Type Ib supernova. It was also the first to be associated with a gamma-ray burst, known as GRB 980425. The total mass ejected by SN 1998bw was about 10 solar masses. It also ejected about 0.4 solar masses of nickel. The radioactive decay of the ejected nickel, specifically 56Ni, makes the outburst much brighter. Hypernovae are also associated with unusually bright radio supernovae, sometimes called radio hypernovae.

Scientists study different models to explain how these stars lose their outer layers. One idea involves binary systems, where two stars orbit each other. A companion star might strip the outer envelope of a massive star. This leaves behind a bare carbon-oxygen core. This process helps create the specific conditions needed for a Type Ic explosion. Another theory involves induced gravitational collapse. This occurs when a neutron star collapses into a black hole because of a nearby companion star. These models help explain why some stars become the progenitors of hypernovae.

While hypernovae are distinct, they can be confused with other energetic events. In 2023, astronomers observed a very strong event named AT2021lwx. This event emitted energy from mid-infrared to X-ray wavelengths. However, it was not a hypernova. It was likely a huge gas cloud being absorbed by a massive black hole. The Zwicky Transient Facility gave it the random name ZTF20abrbeie. Because of its ferocity, the press nicknamed it "Scary Barbie." Studying these different high-energy events helps astronomers distinguish between various cosmic phenomena.