Cosmic dust from ‘zombie’ galaxies could form planets and life
Sarah Knapton
Sat, 10 February 2024
A spiral galaxy, located 30 million light-years away from Earth, is seen from the James Webb Space Telescope - NASA
Stars exploding in “zombie” galaxies produce cosmic dust that could form planets and even life, scientists have discovered.
Elliptical galaxies - known as “red and dead”, or “zombie” galaxies - consist of old stars that lack the energy to explode in the intense supernovae that create the building blocks of planets.
Yet observations by Cardiff University found that many “dead” galaxies were surprisingly dusty.
To find out what might be causing the unexpected cosmic dust, astronomers studied the aftermath of a low energy supernova in an elliptical galaxy more than 300 million light years away.
The original star had been part of a binary star system and the team found that when it exploded, the shock wave crashed into material cast off by itself and its sister star, causing dust to form.
The findings reveal a new source for the tiny particles of cosmic matter thought to be the building blocks of the small bodies of gas and dust known as planetesimals, and ultimately rocky planets and even life across the universe.
Prof Haley Gomez, Head of Cardiff University’s School of Physics and Astronomy, said: “One of the fundamental questions in astronomy is: what types of stars form dust? We thought we had a pretty good answer to this until ESA’s Herschel Space Observatory hinted at the existence of some puzzling elliptical galaxies around 10 years ago.
“Sometimes called red and dead or zombie galaxies, ellipticals are different to spirals like the Milky Way – they are made up of swarms of stars and they do not have core-collapse explosions – and yet Cardiff astronomers discovered a whole host that were extremely dusty.
“Our new study shows that only 1,041 days after the explosion, a huge amount of cosmic dust was formed, equivalent to 1 per cent of our Sun’s mass.
“This may offer an explanation for the abundance of dust we see in these strange elliptical galaxies.”
Cosmic dust, just like dust on Earth, is made from molecules that have condensed and stuck together to form a grain. Over time more and more can come together to form planets.
The team used space-based telescopes including Nasa’s Spitzer and Neowise missions, and ground-based facilities in China, South America, and Australia to observe the zombie supernova explosion over three years.
Data showed that the visible light from the supernova grew dimmer over time, suggesting the newly formed dust was starting to screen out its glow. Meanwhile the infrared glow of dust grew brighter.
Prof Gomez added: “Our study shows that the explosive material from the supernova needs to interact with a companion, in this case a younger, slightly more massive star in order to create a lot of dust.”
Until now researchers had focused their search for so-called dust factories on Type II supernovae – massive stars which explode at the end of their short lives through a process known as core collapse.
Prof Andy Howell from Las Cumbres Observatory and the University of California Santa Barbara said: “The creation of dust is just gas getting cold enough to condense.”
“One day that dust will condense into planetesimals and, ultimately, planets. This is creation starting anew in the wake of stellar death. It is exciting to understand another link in the circle of life and death in the universe.”
The new research was published in Nature Astronomy.
Sarah Knapton
Sat, 10 February 2024
A spiral galaxy, located 30 million light-years away from Earth, is seen from the James Webb Space Telescope - NASA
Stars exploding in “zombie” galaxies produce cosmic dust that could form planets and even life, scientists have discovered.
Elliptical galaxies - known as “red and dead”, or “zombie” galaxies - consist of old stars that lack the energy to explode in the intense supernovae that create the building blocks of planets.
Yet observations by Cardiff University found that many “dead” galaxies were surprisingly dusty.
To find out what might be causing the unexpected cosmic dust, astronomers studied the aftermath of a low energy supernova in an elliptical galaxy more than 300 million light years away.
The original star had been part of a binary star system and the team found that when it exploded, the shock wave crashed into material cast off by itself and its sister star, causing dust to form.
The findings reveal a new source for the tiny particles of cosmic matter thought to be the building blocks of the small bodies of gas and dust known as planetesimals, and ultimately rocky planets and even life across the universe.
Prof Haley Gomez, Head of Cardiff University’s School of Physics and Astronomy, said: “One of the fundamental questions in astronomy is: what types of stars form dust? We thought we had a pretty good answer to this until ESA’s Herschel Space Observatory hinted at the existence of some puzzling elliptical galaxies around 10 years ago.
“Sometimes called red and dead or zombie galaxies, ellipticals are different to spirals like the Milky Way – they are made up of swarms of stars and they do not have core-collapse explosions – and yet Cardiff astronomers discovered a whole host that were extremely dusty.
“Our new study shows that only 1,041 days after the explosion, a huge amount of cosmic dust was formed, equivalent to 1 per cent of our Sun’s mass.
“This may offer an explanation for the abundance of dust we see in these strange elliptical galaxies.”
Cosmic dust, just like dust on Earth, is made from molecules that have condensed and stuck together to form a grain. Over time more and more can come together to form planets.
The team used space-based telescopes including Nasa’s Spitzer and Neowise missions, and ground-based facilities in China, South America, and Australia to observe the zombie supernova explosion over three years.
Data showed that the visible light from the supernova grew dimmer over time, suggesting the newly formed dust was starting to screen out its glow. Meanwhile the infrared glow of dust grew brighter.
Prof Gomez added: “Our study shows that the explosive material from the supernova needs to interact with a companion, in this case a younger, slightly more massive star in order to create a lot of dust.”
Until now researchers had focused their search for so-called dust factories on Type II supernovae – massive stars which explode at the end of their short lives through a process known as core collapse.
Prof Andy Howell from Las Cumbres Observatory and the University of California Santa Barbara said: “The creation of dust is just gas getting cold enough to condense.”
“One day that dust will condense into planetesimals and, ultimately, planets. This is creation starting anew in the wake of stellar death. It is exciting to understand another link in the circle of life and death in the universe.”
The new research was published in Nature Astronomy.
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