Post by Andrei Tchentchik on Jun 24, 2019 16:25:23 GMT 2
(.#220).- Hubble surprises an asteroid in full self-destruction.
Hubble surprises an asteroid in full self-destruction.
By Tristan Vey - Published 29/03/2019 at 17:50
The "tails" of the asteroid (6478) Gault extend respectively 800,000 and 200,000 km. They are only a few thousand kilometers wide. NASA, ESA, K. Meech and J. Kleyna (University of Hawaii), and O. Hainaut (European Southern Observatory).
The asteroid (6478) Gault was caught breaking up, forming behind him two long, luminous trails that give him false comet airs.
It is neither a comet nor a shooting star. It's not a spaceship either. This strange object with long luminous tails is actually a surprised asteroid breaking up. This amazing shot was taken by the Hubble Space Telescope. But by the way, how is it so surprising ?
Only about twenty asteroids have already shown a similar "activity". But rarely so dramatically. Asteroids are in principle simple rocks, more or less big and choppy, whose existence remains relatively monotonous (except collision with a planet, the dinosaurs remember it, or with another asteroid). They differ in that of comets, bodies of composition finally quite similar but remained for billions of years in the frozen confines of the Solar System before being projected to the Sun for another reason. With each passing near our star, they vaporize then giving birth to a hair and a tail as gigantic as spectacular.
But it is not this phenomenon that explains the formation of these long tracts of dust here. It is a priori the rotation of the asteroid on itself that eventually cause its disintegration (partial for the moment). This rotation would have gradually increased, over millions of years, under the action of YORP effect (Yarkovsky-O'Keefe-Radzievskii-Paddack), a complex phenomenon related to the fact that the asteroid does not shine in all directions in the same way.
Double disintegration
When the rotation reaches a critical speed of half a turn per hour, the gravity is no longer sufficient to maintain the cohesion of the whole. Landslides occur and some of the friable material is projected only a few kilometers away. Still enough to escape the attraction of the asteroid! Solar photons then accelerate the dust, the faster they are small. Astronomers estimate that the farthest, at 800,000 km for the longest tail, 200,000 for the smallest, are not larger than a grain of flour. The closest to the asteroid are the size of large grains of sand.
These are two successive disintegrations, a priori October 28th and then December 30th which led to the formation of the two "tails" of (6478) Gault. These were discovered only on January 5 by the ATLAS (Asteroid Terrestrial-Impact Last Alert System) telescope located in Hawaii. Other older data were then found in the telescope archives, but also in those of the PanSTARRS telescope, also in Hawaii. Different instruments then scanned the asteroid, including the Hubble Space Telescope.
All of these observations will soon be published in The Astrophysical Journal Letters.
F I N .
Hubble surprises an asteroid in full self-destruction.
By Tristan Vey - Published 29/03/2019 at 17:50
The "tails" of the asteroid (6478) Gault extend respectively 800,000 and 200,000 km. They are only a few thousand kilometers wide. NASA, ESA, K. Meech and J. Kleyna (University of Hawaii), and O. Hainaut (European Southern Observatory).
The asteroid (6478) Gault was caught breaking up, forming behind him two long, luminous trails that give him false comet airs.
It is neither a comet nor a shooting star. It's not a spaceship either. This strange object with long luminous tails is actually a surprised asteroid breaking up. This amazing shot was taken by the Hubble Space Telescope. But by the way, how is it so surprising ?
Only about twenty asteroids have already shown a similar "activity". But rarely so dramatically. Asteroids are in principle simple rocks, more or less big and choppy, whose existence remains relatively monotonous (except collision with a planet, the dinosaurs remember it, or with another asteroid). They differ in that of comets, bodies of composition finally quite similar but remained for billions of years in the frozen confines of the Solar System before being projected to the Sun for another reason. With each passing near our star, they vaporize then giving birth to a hair and a tail as gigantic as spectacular.
But it is not this phenomenon that explains the formation of these long tracts of dust here. It is a priori the rotation of the asteroid on itself that eventually cause its disintegration (partial for the moment). This rotation would have gradually increased, over millions of years, under the action of YORP effect (Yarkovsky-O'Keefe-Radzievskii-Paddack), a complex phenomenon related to the fact that the asteroid does not shine in all directions in the same way.
Double disintegration
When the rotation reaches a critical speed of half a turn per hour, the gravity is no longer sufficient to maintain the cohesion of the whole. Landslides occur and some of the friable material is projected only a few kilometers away. Still enough to escape the attraction of the asteroid! Solar photons then accelerate the dust, the faster they are small. Astronomers estimate that the farthest, at 800,000 km for the longest tail, 200,000 for the smallest, are not larger than a grain of flour. The closest to the asteroid are the size of large grains of sand.
These are two successive disintegrations, a priori October 28th and then December 30th which led to the formation of the two "tails" of (6478) Gault. These were discovered only on January 5 by the ATLAS (Asteroid Terrestrial-Impact Last Alert System) telescope located in Hawaii. Other older data were then found in the telescope archives, but also in those of the PanSTARRS telescope, also in Hawaii. Different instruments then scanned the asteroid, including the Hubble Space Telescope.
All of these observations will soon be published in The Astrophysical Journal Letters.
F I N .
