Nav: Home

Stars need a partner to spin Universe's brightest explosions

January 13, 2020

When it comes to the biggest and brightest explosions seen in the Universe, University of Warwick astronomers have found that it takes two stars to make a gamma-ray burst.

New research solves the mystery of how stars spin fast enough to create conditions to launch a jet of highly energetic material into space, and has found that tidal effects like those between the Moon and the Earth are the answer.

The discovery, reported in Monthly Notices of the Royal Astronomical Society, has been made using simulated models of thousands of binary star systems, that is, solar systems that have two stars orbiting one another.

More than half of all stars are located in binary star systems and this new research has shown that they need to be in binary star systems in order for the massive explosions to be created.

A long gamma-ray burst (GRB), the type examined in this study, occurs when a massive star about ten times the size of our sun goes supernova, collapses into a neutron star or black hole and fires a relativistic jet of material into space. Instead of the star collapsing radially inwards, it flattens down into a disc to conserve angular momentum. As the material falls inwards, that angular momentum launches it in the form of a jet along the polar axis.

But in order to form that jet of material, the star has to be spinning fast enough to launch material along the axis. This presents a problem because stars usually lose any spin they acquire very quickly. By modelling the behaviour of these massive stars as they collapse, the researchers have been able to constrain the factors that cause a jet to be formed.

They found that the effects of tides from a close neighbour - the same effect that has the Moon and the Earth locked together in their spin - could be responsible for spinning these stars at the rate needed to create a gamma-ray burst.

Gamma-ray bursts are the most luminous events in the Universe and are observable from Earth when their jet of material is pointed directly at us. This means that we only see around 10-20% of the GRBs in our skies.

Lead author Ashley Chrimes, a PhD student in the University of Warwick Department of Physics, said: "We're predicting what kind of stars or systems produce gamma-ray bursts, which are the biggest explosions in the Universe. Until now it's been unclear what kind of stars or binary systems you need to produce that result.

"The question has been how a star starts spinning, or maintains its spin over time. We found that the effect of a star's tides on its partner is stopping them from slowing down and, in some cases, it is spinning them up. They are stealing rotational energy from their companion, a consequence of which is that they then drift further away.

"What we have determined is that the majority of stars are spinning fast precisely because they're in a binary system."

The study uses a collection of binary stellar evolution models created by researchers from the University of Warwick and Dr J J Eldridge from the University of Auckland. Using a technique called binary population synthesis, the scientists are able to simulate this mechanism in a population of thousands of star systems and so identify the rare examples where an explosion of this type can occur.

Dr Elizabeth Stanway, from the University of Warwick Department of Physics, said: "Scientists haven't modelled in detail for binary evolution in the past because it's a very complex calculation to do. This work has considered a physical mechanism within those models that we haven't examined before, that suggests that binaries can produce enough GRBs using this method to explain the number that we are observing.

"There has also been a big dilemma over the metallicity of stars that produce gamma-ray bursts. As astronomers, we measure the composition of stars and the dominant pathway for gamma-ray bursts requires very few iron atoms or other heavy elements in the stellar atmosphere. There's been a puzzle over why we see a variety of compositions in the stars producing gamma-ray bursts, and this model offers an explanation."

Ashley added: "This model allows us to predict what these systems should look like observationally in terms of their temperature and luminosity, and what the properties of the companion are likely to be. We are now interested in applying this analysis to explore different astrophysical transients, such as fast radio bursts, and can potentially model rarer events such as black holes spiralling into stars."
-end-
* 'Binary population synthesis models for core-collapse gamma-ray burst progenitors' is published in Monthly Notices of the Royal Astronomical Society, DOI: 10.1093/mnras/stz3246

* The authors were supported through funding from the Science and Technology Facilities Council.

Notes to editors:

For interviews and a copy of the study contact:

Peter Thorley
Media Relations Manager (Warwick Medical School and Department of Physics) | Press & Media Relations | University of Warwick
Email: peter.thorley@warwick.ac.uk
Tel: +44 (0)24 761 50868

University of Warwick

Related Astronomers Articles:

Canadian astronomers determine Earth's fingerprint
Two McGill University astronomers have assembled a 'fingerprint' for Earth, which could be used to identify a planet beyond our Solar System capable of supporting life.
Astronomers help wage war on cancer
Techniques developed by astronomers could help in the fight against breast and skin cancer.
Astronomers make history in a split second
In a world first, an Australian-led international team of astronomers has determined the precise location of a powerful one-off burst of cosmic radio waves.
Astronomers witness galaxy megamerger
Using the Atacama Large Millimeter/submillimeter Array (ALMA), an international team of scientists has uncovered a startlingly dense concentration of 14 galaxies that are poised to merge, forming the core of what will eventually become a colossal galaxy cluster.
Double or nothing: Astronomers rethink quasar environment
Using Hyper Suprime-Cam (HSC) mounted on the Subaru Telescope, astronomers have identified nearly 200 'protoclusters,' the progenitors of galaxy clusters, in the early Universe, about 12 billion years ago, about ten times more than previously known.
Astronomers discover a star that would not die
An international team of astronomers has made a bizarre discovery; a star that refuses to stop shining.
Astronomers spun up by galaxy-shape finding
For the first time astronomers have measured how a galaxy's spin affects its shape -- something scientists have tried to do for 90 years -- using a sample of 845 galaxies.
Astronomers unveil 'heart' of Eta Carinae
An international team of astronomers has imaged the Eta Carinae star system -- a colossal binary system that consists of two massive stars orbiting each other -- including a region between the two stars in which extremely high-velocity stellar winds are colliding.
Astronomers capture best view ever of disintegrating comet
Astronomers have captured the sharpest, most detailed observations of a comet breaking apart 67 million miles from Earth, using NASA's Hubble Space Telescope.
Astronomers find the first 'wind nebula' around a magnetar
Astronomers have discovered a vast cloud of high-energy particles called a wind nebula around a rare ultra-magnetic neutron star, or magnetar, for the first time.
More Astronomers News and Astronomers Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Teaching For Better Humans 2.0
More than test scores or good grades–what do kids need for the future? This hour, TED speakers explore how to help children grow into better humans, both during and after this time of crisis. Guests include educators Richard Culatta and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Space
One of the most consistent questions we get at the show is from parents who want to know which episodes are kid-friendly and which aren't. So today, we're releasing a separate feed, Radiolab for Kids. To kick it off, we're rerunning an all-time favorite episode: Space. In the 60's, space exploration was an American obsession. This hour, we chart the path from romance to increasing cynicism. We begin with Ann Druyan, widow of Carl Sagan, with a story about the Voyager expedition, true love, and a golden record that travels through space. And astrophysicist Neil de Grasse Tyson explains the Coepernican Principle, and just how insignificant we are. Support Radiolab today at Radiolab.org/donate.