It is a visitor from a strange land.
Category: cosmology – Page 285
Eventually, galaxies stop making new stars. But why did some stop so much sooner than others? Hint: black holes play a role.
A galaxy’s main business is star formation. And when they’re young, like youth everywhere, they keep themselves busy with it. But galaxies age, evolve, and experience a slow-down in their rate of star formation. Eventually, galaxies cease forming new stars altogether, and astronomers call that quenching. They’ve been studying quenching for decades, yet much about it remains a mystery.
A new study based on the IllustrisTNG simulations has found a link between a galaxy’s quenching and its stellar size.
Scientists are finally figuring out how much dark matter — the almost imperceptible material said to tug on everything, yet emit no light — really weighs.
Astronomy owes George Ellery Hale and the Palomar Observatory a great debt of gratitude for persevering with the construction of a telescope that forever changed cosmology.
I don’t think that star is the same after that one night stand.
When black holes swallow down massive amounts of matter from the space around them, they’re not exactly subtle about it. They belch out tremendous flares of X-rays, generated by the material heating to intense temperatures as it’s sucked towards the black hole, so bright we can detect them from Earth.
This is normal black hole behaviour. What isn’t normal is for those X-ray flares to spew forth with clockwork regularity, a puzzling behaviour reported in 2019 from a supermassive black hole at the centre of a galaxy 250 million light-years away. Every nine hours, boom — X-ray flare.
After careful study, astronomer Andrew King of the University of Leicester in the UK identified a potential cause — a dead star that’s endured its brush with a black hole, trapped on a nine-hour, elliptical orbit around it. Every close pass, or periastron, the black hole slurps up more of the star’s material.
A new paper suggests that the mysterious X17 subatomic particle is indicative of a fifth force of nature.
Very interesting.
Albert Einstein’s theory of general relativity profoundly changed our thinking about fundamental concepts in physics, such as space and time. But it also left us with some deep mysteries. One was black holes, which were only unequivocally detected over the past few years. Another was “wormholes” – bridges connecting different points in spacetime, in theory providing shortcuts for space travellers.
Wormholes are still in the realm of the imagination. But some scientists think we will soon be able to find them, too. Over the past few months, several new studies have suggested intriguing ways forward.
Physicists imagine a day when they will be able to design a clock that’s so precise, it can detect dark matter.
Circa 2018 o.o!
We are not living in the first universe. There were other universes, in other eons, before ours, a group of physicists has said. Like ours, these universes were full of black holes. And we can detect traces of those long-dead black holes in the cosmic microwave background (CMB) — the radioactive remnant of our universe’s violent birth.
At least, that’s the somewhat eccentric view of the group of theorists, including the prominent Oxford University mathematical physicist Roger Penrose (also an important Stephen Hawking collaborator). Penrose and his acolytes argue for a modified version of the Big Bang.
In Penrose and similarly-inclined physicists’ history of space and time (which they call conformal cyclic cosmology, or CCC), universes bubble up, expand and die in sequence, with black holes from each leaving traces in the universes that follow. And in a new paper released Aug. 6 in the preprint journal arXiv— apparent evidence for Hawking points in the CMB sky — Penrose, along with State University of New York Maritime College mathematician Daniel An and University of Warsaw theoretical physicist Krzysztof Meissner, argued that those traces are visible in existing data from the CMB.