Astronomers are Starting to Find the Wreckage Left Over from the First Stars in the Universe
The first stars were odd ducks. Nobody’s observed them yet (although astronomers are hopeful JWST might spot them someday) but their ghosts remain. Born more than 13.5 billion years ago, they were very different from most of those we know today. These were massive monsters made mostly of hydrogen and helium. And, when they exploded as supernovae, their “starstuff” got scattered to space. Astronomers have now found the chemical remains of those stars in three distant gas clouds observed by European Southern Observatory’s Very Large Telescope.
How can astronomers detect those remains? It’s a tough task because the succeeding generations of stars recycled the starstuff. When those “child” stars died, they scattered their own heavier elements throughout space, which, in turn, got used in the next generations of stars.
So, the very first stars and their remains are pretty much history. Or, are they? It turns out maybe not. “Primordial stars can be studied indirectly by detecting the chemical elements they dispersed in their environment after their death,” said Stefania Salvadori, Associate Professor at the University of Florence.
She and a colleague used data from the VLT to search for gas clouds with the chemical elements left over from the deaths of the first stars. Light from distant quasars passing through those clouds provided a way to look for those elements.
When the light of a quasar passes through a gas cloud, the chemical elements in it absorb different wavelengths. That leaves dark lines in the spectrum of the quasar. Each element leaves a different set of lines, so by studying the spectrum astronomers can work out the chemical composition of the intervening gas cloud. This is how astronomers found the chemical fingerprints of the first stars in three clouds of gas in the early Universe. Courtesy ESO.
Understanding Stellar Chemical Wreckage
The mass of these early stars and the strength of their explosions determined which elements were spread to space. The first ones may have been mainly hydrogen and helium, but they cooked up other elements inside their cores. That is, in fact, what stars do throughout their lives. They turn hydrogen into helium and other “heavy” elements in their cores. Typically, they form carbon, oxygen, silicon, and so on, all the way up to iron. When they die all that material gets scattered to interstellar space. Those like the Sun live fairly long lives and end up as white dwarfs. That’s after they go through a planetary nebula phase. Only the most massive ones die in supernova explosions.
An artist’s illustration of the first stars to appear in the universe.
Credit: N.R. Fuller, National Science Foundation
Those first massive stars died in really tremendous supernova explosions and those provided the chemical remains the astronomers found. However, some of those first explosions were not energetic enough to scatter elements like iron that existed in their cores.
The team had to take that into account, so they searched for gas clouds from stars that exploded as low-energy supernovae. The three they studied were in the early Universe and had very little iron but plenty of carbon and other elements.
Implications for Other Stars
Interestingly, the peculiar chemical composition in the clouds studied by Salvadori and her team shows up in many old stars in our own galaxy. These are second-generation stellar populations that formed directly from the “ashes” of the first ones. “Our discovery opens new avenues to indirectly study the nature of the first stars, fully complementing studies of stars in our galaxy,” explained Salvadori.
The second-generation ones had a much different, richer chemical composition than their “parents” from the early Universe. When they died, their “starstuff” became fodder for the third and subsequent generations.
Did you miss our previous article…
ARABSAT BADR-8 Mission Control Audio
This is the vehicle trajectory and mission control audio without any additional commentary. There may be very long periods of silence. For our full hosted webcast, visit
Did you miss our previous article…
When Black Holes Merge, They’ll Ring Like a Bell
When two black holes collide, they don’t smash into each other the way two stars might. A black hole is an intensely curved region of space that can be described by only its mass, rotation, and electric charge, so two black holes release violent gravitational ripples as merge into a single black hole. The new black hole continues to emit gravitational waves until it settles down into a simple rotating black hole. That settling down period is known as the ring down, and its pattern holds clues to some of the deepest mysteries of gravitational physics.
Gravitational wave observatories such as the Laser Interferometry Gravitational-Wave Observatory (LIGO) have mostly focused on the inspiral period of black hole mergers. This is the period where the two black holes orbit ever closer to each other, creating a rhythmic stream of strong gravitational waves. From this astronomers can determine the mass and rotation of the original black holes, as well as the mass and rotation of the merged black hole. The pattern of gravitational waves we observe is governed by Einstein’s general relativity equations, and by matching observation to theory we learn about black holes.
General relativity describes gravity extremely well. Of all the gravitational tests we’ve done, they all agree with general relativity. But Einstein’s theory doesn’t play well with the other extremely accurate physical theory, quantum mechanics. Because of this, physicists have proposed modifications to general relativity that are more compatible with quantum theory. Under these modified theories, there are subtle differences in the way merged black holes ring down, but observing those differences hasn’t been possible. But a couple of new studies show how we might be able to observe them in the next LIGO run.
The modified Teukolsky equation. Credit: Li, Dongjun, et al
In the first work, the team focused on what is known as the Teukolsky Equation. First proposed by Saul Teukolsky, the equations are an efficient way of analyzing gravitational waves. The equations only apply to classical general relativity, so the team developed a way to modify the equations for modified general relativity models. Since the solutions to both the Teukolsky and modified Teukolsky equations don’t require a massive supercomputer to solve, the team can compare black hole ring downs in various gravitational models.
The second work looks at how this would be done with LIGO data. Rather than focusing on general differences, this work focuses on what is known as the no-hair theorem. General relativity predicts that no matter how two black holes merge, the final merged black hole must be described by only mass, rotation, and charge. It can’t have any “hair”, or remnant features of the collision. In some modified versions of general relativity, black holes can have certain features, which would violate the no-hair theorem. In this second work, the authors show how this could be used to test general relativity against certain modified theories.
LIGO has just begun its latest observation run, so it will be a while before there is enough data to test. But we may soon have a new observational test of Einstein’s old theory, and we might just prove it isn’t the final theory of gravity after all.
Reference: Li, Dongjun, et al. “Perturbations of spinning black holes beyond General Relativity: Modified Teukolsky equation.” Physical Review X 13.2 (2022): 021029.
Reference: Ma, Sizheng, Ling Sun, and Yanbei Chen. “Black hole spectroscopy by mode cleaning.” Physical Review Letters 130.2 (2023): 141401.
The post When Black Holes Merge, They’ll Ring Like a Bell appeared first on Universe Today.
Did you miss our previous article…
There’s a Polar Cyclone on Uranus’ North Pole
Uranus takes 84 years to orbit the Sun, and so that last time that planet’s north polar region was pointed at Earth, radio telescope technology was in its infancy.
But now, scientists have been using radio telescopes like the Very Large Array (VLA) the past few years as Uranus has slowly revealing more and more of its north pole. VLA microwave observations from 2021 and 2022 show a giant cyclone swirling around this region, with a bright, compact spot centered at Uranus’ pole. Data also reveals patterns in temperature, zonal wind speed and trace gas variations consistent with a polar cyclone.
Uranus as seen by NASA’s Voyager 2. Credit: NASA/JPL
Scientists have long known that Uranus’ south pole has a swirling feature. When Voyager 2 flew past Uranus in 1986, it detected high wind speeds there. However, the way the planet was tilted did not allow Voyager to see the north pole.
But the VLA in New Mexico has now been studying Uranus the past several years, and observations collected in 2015, 2021, and 2022 were able to peer deep into Uranus’ atmosphere. The thermal emission data showed that circulating air at the north pole seems to be warmer and drier, which are the hallmarks of a strong cyclone.
“These observations tell us a lot more about the story of Uranus. It’s a much more dynamic world than you might think,” said Alex Akins of NASA’s Jet Propulsion Laboratory in Southern California, who is lead author of a new study published in Geophysical Letters. “It isn’t just a plain blue ball of gas. There’s a lot happening under the hood.”
The researchers said the cyclone on Uranus is similar to the polar cyclones observed by the Cassini mission at Saturn. With the new findings, cyclones (which rotate in the same direction their planet rotates) or anti-cyclones (which rotate in the opposite direction) have now been identified at the poles on every planet in our solar system that has an atmosphere. The researchers said this confirms a broad truth that planets with substantial atmospheres – whether the worlds are made of rock or gas – all show signs of swirling vortexes at the poles.
Uranus’ north pole is now in springtime. As it continues into summer, astronomers hope to see even more changes in its atmosphere.
The post There’s a Polar Cyclone on Uranus’ North Pole appeared first on Universe Today.
Did you miss our previous article…
Mens Health3 years ago
8 Things I Do Before 8 Am: My Morning Routine
Fashion2 years ago
Best Timepieces To Buy For The Holiday Season
Fashion3 years ago
Steampunk Clothing & Jewelry
Sports2 years ago
Best Christmas Gift For Your Golfer Co-Worker
Trending Stories2 years ago
Dior Homme Cologne Men’s Fragrance Review
Motor2 years ago
2022 Infiniti QX55 Carigami Can Be Yours
Uncategorized3 years ago
How To Attract Women Easily (Without Talking)
Grooming3 years ago
5 Men’s Hairstyles For Thin Hair – Haircuts For Receding Hairlines