April 2024 : ABC's of GRB's

Episode Audio

ABC's of GRB's. In this episode, Soheb and Fiona interview Dr Gavin Lamb from Liverpool John Moores University and they discuss the exotic nature of gamma ray bursts. In our News section Fiona is joined by Mel and Honor and they discuss NASA's DART mission, the oldest 'dead' galaxy yet and why Gallifrey must not exist. Jodbites also makes a comeback! Here Fiona interviews Micah Bowles and they discuss some of his research using machine learning.

The News

NASA's DART mission

Two years ago, NASA deliberately crashed a spacecraft into an asteroid called Dimorphos for its Double Asteroid Redirection Test (DART) mission, as part of efforts to test out whether it would be possible to redirect asteroids away from Earth before their orbit led them to collide with us. The aim of this mission was to reduce Dimorphos's orbital period around the larger asteroid Didymos by at least 73 seconds, and it proved even more successful than hoped when its orbit was instead shortened by about half an hour. Since the collision occurred we have been studying its aftereffects, and a recent paper in Nature has shown that we seem to have altered the shape of the asteroid itself. Dimorphos appears to be comprised of a significant amount of loose rock and dust, and when hit by DART this loose material was disrupted; about 1% escaped the weak gravitational pull of the asteroid, but another 8-9% was redispersed around the rest of the asteroid and has both changed its overall shape and prevented a visible crater forming. Further observations on Dimorphos will be carried out in 2026 by ESA's Hera spacecraft.

Astronomers spot oldest ‘dead’ galaxy yet

An international group of astronomers led by the University of Cambridge have used the James Webb Space Telescope to spot the oldest ‘dead’ galaxy yet, meaning it is ‘quenched’ or no longer star-forming. This research, published in Nature could help determine how the factors that affect star formation have changed, and why we see galaxies stop forming new stars. Star formation can be halted in a variety of ways, especially in galaxies found in the later universe. Some of these include black holes, feedback blowing gas out or the galaxy itself depleting the available gas by forming stars too quickly.

The galaxy was found in JADES -JWST Advanced Deep Extragalactic Survey- and has a relatively low mass, similar to that of the Small Magellanic Cloud or a dwarf galaxy. The team determined that the galaxy had a period of intense star formation, before stopping abruptly and ‘dying’ around 10-20 million years before the observation. By looking for other galaxies around this time period, the team could determine whether or not these old ‘dead’ galaxies have permanently or temporarily 'turned off' their star formation phase and help further constrain ideas about star formation within the earliest galaxies.

Why Gallifrey must not exist!

It turns out that circumbinary planets should be icy, not rocky. According to a recent article by Pierens & Nelson (2024), we should expect planets in orbit around binary stars to be icy. Their investigations into the snow line of circumbinary discs led them to conclude this. Their simulations showed that the distance from the binary stars at which water ice would have condensed, is in a narrow region of the circumbinary disc, typically circa 1.5 - 2 au from the stellar pair. Could a planet form this close to its binary host stars?

Previous work has shown that the formation of icy grains from dense clouds and the accretion of pebbles formed within the protoplanetary disc are insufficient to explain planetary formation at this distance. As such, planets are likely to form beyond the snow line of their binary hosts, rather than below to it, ruling out the possibility of rocky planets forming in binary star systems.

Interview with Gavin Lamb

Soheb Mandhai and Fiona Porter interview Dr. Gavin Lamb from Liverpool John Moores University, where he researches gamma ray bursts and the astrophysical objects that produce them.

Odds and Ends

We discussed the paper “Could a Kilonova Kill: A Threat Assessment”. Though the expected occurrence rate of one nearby enough to be dangerous is something like one every few 100 billion years, if one happened within a few parsecs of earth it could kill us in four or five different ways !

Show Credits

News : Fiona Porter, Mels Azombo, Honor Harris and Soheb Mandhai
Interview : Dr Gavin Lamb and Soheb Mandhai and Fiona Porter
Night Sky : Fiona Porter, Mels Azombo, Honor Harris and Soheb Mandhai
Presenters : Fiona Porter, Mels Azombo, Honor Harris and Soheb Mandhai
Editors : James Turner and Louisa Mason
Website : Lily Correa Magnus & Jessy Marin
Producer : Lily Correa Magnus and Jessy Marin
Cover Art : Artist interpretation of a GRB. CREDIT:Dr Soheb Mandhai