Daily Bulletin

The Conversation

  • Written by Gavin Rowell, Associate Professor in High Energy Astrophyics, University of Adelaide

The brightest fireworks in the universe are called gamma-ray bursts and are created by the death throes of certain kinds of stars. These intense blasts release as much energy in one second as the Sun will over its whole lifetime, but we still don’t understand exactly how they do it.

We are getting closer, however. We recently had the best ever look at the incredibly high-energy gamma rays emitted by these bursts. Gamma rays are like particles of visible light, but each of these high-energy rays carries as much as 100 billion times more energy.

New research published this week in Nature by two teams of scientists from around the world (I am a member of one of them) reveals the gamma rays are more energetic than we knew and that the afterglow of the burst lasts much longer.

What are gamma-ray bursts?

In the late 1960s, secret spy satellites designed to look for gamma-ray flashes from nuclear explosions began to detect mysterious bursts of gamma rays coming from outer space. It was not until the 1990s that scientists began to unravel the mystery with data from new satellites.

We now believe at least some of these gamma-ray bursts are caused by the collapse of super-massive stars. Many stars end their lives in an enormous explosion called a supernova, but very heavy stars can create an even bigger blast called a hypernova.

Read more: Flash, aah-aah! Could a gamma ray burst eradicate all life on Earth?

In this process, the star’s core collapses and becomes a rapidly rotating black hole. The surrounding gas forms a spinning disk around the black hole, which then creates a narrow, intense jet of radiation. If this jet is pointing towards Earth, we can see it as a bright gamma-ray burst, which typically lasts no more than a minute or two.

The very high-energy gamma rays are given off by matter that is accelerated to very close to the speed of light as it whirls around the black hole.

Because the bursts are rare and don’t last long, it can be difficult to get a good look at one with a telescope.

The afterglow

On July 20 2018, gamma-ray and X-ray satellites alerted the world to a new gamma-ray burst, named GRB 180720B. It was a very strong burst and lasted for about 50 seconds – a relatively long duration, indicating the death of a massive star.

Following the alert, several observatories around the world immediately began observing the spot in the sky that the burst came from. About 10 hours later, that spot came into view for the High-Energy Stereoscopic System (HESS) gamma-ray telescopes in Namibia.

Even though 10 hours had passed, HESS was able to observe the afterglow of the burst, which still included extremely energetic gamma rays.

A collapsing star in a distant galaxy fired out some of the most energetic gamma rays ever seen Very high-energy gamma rays from the gamma-ray burst GRB 180720B, 10 to 12 hours after the burst, as seen by the large HESS telescope. Supplied, Author provided

At HESS we have been looking at other gamma-ray bursts in this way for more than a decade. This was the first time it detected gamma rays from the high-energy afterglow at energies never seen before.

While we had anticipated the detection of gamma-ray bursts at these high energies, the discovery that they were still around many hours after the initial burst came as a great surprise.

This result suggests the accelerated particles creating the gamma rays still exist or are created a long time after the explosion, which is hard to explain with our existing theories of what happens in gamma-ray bursts.

Read more: An extragalactic mystery: where do high-energy cosmic rays come from?

Even more energy

Also just published are observations of a different gamma-ray burst (GRB 190114C) made using the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes in the Canary Islands.

The MAGIC astronomers caught the “prompt” early stages of the burst, detecting gamma rays with even more energy – some of the most energetic ever seen.

These detections show we still have much to learn about gamma-ray bursts. But they also give us confidence that our methods to detect them are improving. We will be able to study plenty more in the future with the much more sensitive Cherenkov Telescope Array, which is now under construction.

Authors: Gavin Rowell, Associate Professor in High Energy Astrophyics, University of Adelaide

Read more http://theconversation.com/a-collapsing-star-in-a-distant-galaxy-fired-out-some-of-the-most-energetic-gamma-rays-ever-seen-127114

Writers Wanted

Major reform of surveillance laws proposed by review


Thank you to everyone who helped The Conversation survive (and thrive) in 2020


The Conversation


Prime Minister Interview with Ben Fordham, 2GB

BEN FORDHAM: Scott Morrison, good morning to you.    PRIME MINISTER: Good morning, Ben. How are you?    FORDHAM: Good. How many days have you got to go?   PRIME MINISTER: I've got another we...

Scott Morrison - avatar Scott Morrison

Prime Minister Interview with Kieran Gilbert, Sky News

KIERAN GILBERT: Kieran Gilbert here with you and the Prime Minister joins me. Prime Minister, thanks so much for your time.  PRIME MINISTER: G'day Kieran.  GILBERT: An assumption a vaccine is ...

Daily Bulletin - avatar Daily Bulletin

Did BLM Really Change the US Police Work?

The Black Lives Matter (BLM) movement has proven that the power of the state rests in the hands of the people it governs. Following the death of 46-year-old black American George Floyd in a case of ...

a Guest Writer - avatar a Guest Writer

Business News

How to Find the Best SEO Services Company That Offers Guaranteed Results

As a business owner, you have to be strategic about how you’ll be able to reach your target market. That is why entrepreneurs implement various marketing tactics to reach their goals. With today...

News Co - avatar News Co

Top Reasons Why Your Business Needs SEO

SEO is crucial for the ranking of a website. You may think that SEO offers greater searchability while it can do more than this. The most cost-effective tool for the survival of smalls businesse...

News Co - avatar News Co

Nisbets’ Collab with The Lobby is Showing the Sexy Side of Hospitality Supply

Hospitality supply services might not immediately make you think ‘sexy’. But when a barkeep in a moodily lit bar holds up the perfectly formed juniper gin balloon or catches the light in the edg...

The Atticism - avatar The Atticism

News Co Media Group

Content & Technology Connecting Global Audiences

More Information - Less Opinion