Jan 20, 2025 08:54 PM
(This post was last modified: Jan 21, 2025 07:07 PM by C C.)
The early universe’s ‘Little Red Dots’ are still a big mystery
https://www.astronomy.com/science/little...g-mystery/
EXCERPTS: On Tuesday, at the 245th meeting of the American Astronomical Society, astronomers revisited some recent mysteries. Dale Kocevski, from Colby College in Maine, spoke during a press conference about the Little Red Dots (LRDs) found in data from the James Webb Space Telescope (JWST).
[...] Scientists simply don’t understand how so many stars and so much material can accumulate in so little time. When the news first broke, there were six of the objects. Now, JWST has revealed 341 of them. Kocevski’s update to the LRD investigation has been accepted for publication in The Astrophysical Journal.
[...] These can no longer be thought of as quirks or outliers. Instead, they make up one out of every five to 10 galaxies in the early cosmos, making them routine. That ups the pressure to understand them, and only emphasizes the gathering suspicion that something about how we understand galaxy assembly, at least the ones at the dawn of cosmic time, is incomplete.
[...] What’s more, these galaxies only appear in the early universe. They disappear from surveys around a redshift of 4, meaning when the universe was less than 2 billion years old. It’s very likely that they evolve into more typical galaxies — but even that tells us that something strange is happening in those early days to produce these phenomena. The LRD mystery goes hand-in-hand with other findings by JWST that the young universe didn’t unfold the way we thought... (MORE - missing details)
Habitable worlds could have formed before the first galaxies
https://www.universetoday.com/170521/hab...-galaxies/
EXCERPT: Could habitable planets really have formed before there were galaxies?
In the immediate aftermath of the Big Bang, there were no heavy elements. There was only hydrogen, which comprised about 75% of the mass, and helium, which comprised the remaining 25%. (There were probably also trace amounts of lithium, even beryllium.) There was nothing heavier, meaning there was nothing for rocky planets to form from. After a few hundred million years, the first stars and galaxies formed.
As successive generations of stars lived and died, they forged heavier elements and spread them out into the Universe. Only after that could rocky planets form, and by extension, habitable planets. That’s been axiomatic in astronomy.
However, new research that’s yet to be published suggests that habitable worlds could’ve formed in the early stages of the Cosmic Dawn, prior to galaxies forming. Its title is “Habitable Worlds Formed at Cosmic Dawn,” and it’s available at the pre-press site arxiv.org. The lead author is Daniel Whalen from the Institute of Cosmology and Gravitation at the University of Portsmouth in the UK.
The research hinges on primordial supernovae, the first stars in the Universe to explode. These massive stars lived fast and died young in cataclysmic explosions. They peaked at about redshift 20 when population III stars, which were extremely massive, exploded as pair-instability supernovae. Simulations show that these stars formed in dark matter haloes where the temperature allowed large amounts of molecular hydrogen to gather.
According to Whalen and his co-researchers, when these stars exploded, low-mass stars formed in the aftermath. Planetesimals formed around those stars, leading to the formation of potentially habitable, rocky worlds. This all happened before the first galaxies formed. These results are based on simulations the research team performed with Enzo.
It starts with a star forming with about 200 solar masses. It lives for only about 2.6 million years before it explodes as a PI supernova. The explosion enriches the supernova bubble to high metallicity. In the aftermath, hydrostatic instabilities cause a dense core to form about 3 million years later, with 35 solar masses.
“All known prerequisites for planet formation in this core are fulfilled: dust growth, dust enhancement in a dead zone, the onset of the streaming instability, and conversion of dust to planetesimals,” the authors explain... (MORE - details)
https://www.astronomy.com/science/little...g-mystery/
EXCERPTS: On Tuesday, at the 245th meeting of the American Astronomical Society, astronomers revisited some recent mysteries. Dale Kocevski, from Colby College in Maine, spoke during a press conference about the Little Red Dots (LRDs) found in data from the James Webb Space Telescope (JWST).
[...] Scientists simply don’t understand how so many stars and so much material can accumulate in so little time. When the news first broke, there were six of the objects. Now, JWST has revealed 341 of them. Kocevski’s update to the LRD investigation has been accepted for publication in The Astrophysical Journal.
[...] These can no longer be thought of as quirks or outliers. Instead, they make up one out of every five to 10 galaxies in the early cosmos, making them routine. That ups the pressure to understand them, and only emphasizes the gathering suspicion that something about how we understand galaxy assembly, at least the ones at the dawn of cosmic time, is incomplete.
[...] What’s more, these galaxies only appear in the early universe. They disappear from surveys around a redshift of 4, meaning when the universe was less than 2 billion years old. It’s very likely that they evolve into more typical galaxies — but even that tells us that something strange is happening in those early days to produce these phenomena. The LRD mystery goes hand-in-hand with other findings by JWST that the young universe didn’t unfold the way we thought... (MORE - missing details)
Habitable worlds could have formed before the first galaxies
https://www.universetoday.com/170521/hab...-galaxies/
EXCERPT: Could habitable planets really have formed before there were galaxies?
In the immediate aftermath of the Big Bang, there were no heavy elements. There was only hydrogen, which comprised about 75% of the mass, and helium, which comprised the remaining 25%. (There were probably also trace amounts of lithium, even beryllium.) There was nothing heavier, meaning there was nothing for rocky planets to form from. After a few hundred million years, the first stars and galaxies formed.
As successive generations of stars lived and died, they forged heavier elements and spread them out into the Universe. Only after that could rocky planets form, and by extension, habitable planets. That’s been axiomatic in astronomy.
However, new research that’s yet to be published suggests that habitable worlds could’ve formed in the early stages of the Cosmic Dawn, prior to galaxies forming. Its title is “Habitable Worlds Formed at Cosmic Dawn,” and it’s available at the pre-press site arxiv.org. The lead author is Daniel Whalen from the Institute of Cosmology and Gravitation at the University of Portsmouth in the UK.
The research hinges on primordial supernovae, the first stars in the Universe to explode. These massive stars lived fast and died young in cataclysmic explosions. They peaked at about redshift 20 when population III stars, which were extremely massive, exploded as pair-instability supernovae. Simulations show that these stars formed in dark matter haloes where the temperature allowed large amounts of molecular hydrogen to gather.
According to Whalen and his co-researchers, when these stars exploded, low-mass stars formed in the aftermath. Planetesimals formed around those stars, leading to the formation of potentially habitable, rocky worlds. This all happened before the first galaxies formed. These results are based on simulations the research team performed with Enzo.
It starts with a star forming with about 200 solar masses. It lives for only about 2.6 million years before it explodes as a PI supernova. The explosion enriches the supernova bubble to high metallicity. In the aftermath, hydrostatic instabilities cause a dense core to form about 3 million years later, with 35 solar masses.
“All known prerequisites for planet formation in this core are fulfilled: dust growth, dust enhancement in a dead zone, the onset of the streaming instability, and conversion of dust to planetesimals,” the authors explain... (MORE - details)