Aug 23, 2022 04:40 PM
(This post was last modified: Aug 23, 2022 04:43 PM by C C.)
Dark matter could finally reveal itself through self-interactions
https://www.space.com/dark-matter-theory...nteracting
INTRO: Despite loads of circumstantial evidence for the existence of dark matter — the mysterious form of matter that dominates galaxies and clusters — astronomers have yet to make direct observations of it.
But the search is not over. One hypothesis for the nature of dark matter is that some of it could be self-interacting, meaning the individual particles interact slightly with one another. If this is true, there would be a host of subtle observational clues for the existence of this subclass of dark matter.
A few of these hints were recently outlined in a paper submitted for publication in the journal Reviews of Modern Physics and published to the preprint database arXiv.... (MORE - missing details)
COVERED: Strong gravitational lensing ... Weak gravitational lensing ... Rotation curves ... Warping of galaxies ... Mergers
The strange case of eyeball planets
https://astronomy.com/magazine/news/2022...ll-planets
INTRO (excerpt): . . . Among these Earth-like exoplanets, there exists a bizarre class known as eyeball planets. These worlds orbit so near to their suns that they are tidally locked, with one hemisphere always facing toward the star and the opposite one in eternal night. Scientists are beginning to realize that eyeball worlds are more than just curiosities — they’re key to understanding how common life might be in the universe. Their arrangement of an always-lit and always-dark side causes fascinating weather and unusual surface conditions. These characteristics may make eyeball planets within the Goldilocks zone prime candidates for hosting life, but they could also make otherwise habitable planets inhospitable.
After coalescing around its star, a planet has some spin. But over time, the host star’s gravity pulls at the world, slowing the body’s rotation until it becomes tidally locked. We have a good example of such synchronous rotation on our own cosmic front porch: The Moon orbits Earth once a month and takes the same amount of time to turn once on its axis. This means that we always see the same face of our Moon.
Eyeball planets initially got their moniker when astronomers noted that in the habitable zone, tidally locked worlds covered by water would become frozen starting at the terminator (the edge of night) while the seas would remain clear near the substellar point (the point that directly faces the star). This dark blue central ocean surrounded by sea ice gives the appearance of an eyeball.
As astronomers racked up exoplanet discoveries over the last 30 years, they realized eyeball planets may be plentiful among planetary systems and that a wide range of worlds may take on an eyeball form.... (MORE - missing details)
COVERED: Types of eyeball planets ... detailed examples, like TRAPPIST-1 e ... Proxima Centauri b ... 55 Cancri E ... LHS 1140 B ... James Webb Space Telescope role
https://youtu.be/9NOW3AormJc
https://www.youtube-nocookie.com/embed/9NOW3AormJc
https://www.space.com/dark-matter-theory...nteracting
INTRO: Despite loads of circumstantial evidence for the existence of dark matter — the mysterious form of matter that dominates galaxies and clusters — astronomers have yet to make direct observations of it.
But the search is not over. One hypothesis for the nature of dark matter is that some of it could be self-interacting, meaning the individual particles interact slightly with one another. If this is true, there would be a host of subtle observational clues for the existence of this subclass of dark matter.
A few of these hints were recently outlined in a paper submitted for publication in the journal Reviews of Modern Physics and published to the preprint database arXiv.... (MORE - missing details)
COVERED: Strong gravitational lensing ... Weak gravitational lensing ... Rotation curves ... Warping of galaxies ... Mergers
The strange case of eyeball planets
https://astronomy.com/magazine/news/2022...ll-planets
INTRO (excerpt): . . . Among these Earth-like exoplanets, there exists a bizarre class known as eyeball planets. These worlds orbit so near to their suns that they are tidally locked, with one hemisphere always facing toward the star and the opposite one in eternal night. Scientists are beginning to realize that eyeball worlds are more than just curiosities — they’re key to understanding how common life might be in the universe. Their arrangement of an always-lit and always-dark side causes fascinating weather and unusual surface conditions. These characteristics may make eyeball planets within the Goldilocks zone prime candidates for hosting life, but they could also make otherwise habitable planets inhospitable.
After coalescing around its star, a planet has some spin. But over time, the host star’s gravity pulls at the world, slowing the body’s rotation until it becomes tidally locked. We have a good example of such synchronous rotation on our own cosmic front porch: The Moon orbits Earth once a month and takes the same amount of time to turn once on its axis. This means that we always see the same face of our Moon.
Eyeball planets initially got their moniker when astronomers noted that in the habitable zone, tidally locked worlds covered by water would become frozen starting at the terminator (the edge of night) while the seas would remain clear near the substellar point (the point that directly faces the star). This dark blue central ocean surrounded by sea ice gives the appearance of an eyeball.
As astronomers racked up exoplanet discoveries over the last 30 years, they realized eyeball planets may be plentiful among planetary systems and that a wide range of worlds may take on an eyeball form.... (MORE - missing details)
COVERED: Types of eyeball planets ... detailed examples, like TRAPPIST-1 e ... Proxima Centauri b ... 55 Cancri E ... LHS 1140 B ... James Webb Space Telescope role
https://youtu.be/9NOW3AormJc
