A rogue planet-sized mass of reconstituted "star-stuff" could very well be in our part of the galactic neighborhood, catapulted in Earth's direction from the supermassive black hole at the Milky Way's center. And if that wasn't bad enough, and even though it is not exactly a star, its mass is traveling at a velocity of about 20 million miles per hour (mph). A collision with such a missile would prove Earth-shattering -- literally.
CBS News reported last week that a new study indicates that the planet-size masses are the result of stars being shredded by the black holes that inhabit most galactic centers, including the Milky Way. But instead of the star's material being further distended and torn apart into small components and being forever captured by the gravity of the black hole, some of the star's mass escapes in a stream of gaseous material back out into space at speed. Since mass attracts mass, much of the gas streamers coalesce into planet-sized shapes within a year after exiting the black hole's grip. The good news is, this type of event occurs about once every thousand years or so. But the bad news is two-fold: as mentioned, the "star-stuff" is moving at 20 million mph, and one solitary star can be shredded into hundreds of world-sized missiles.
"A single shredded star can form hundreds of these planet-mass objects," Eden Girma, an undergraduate student at Harvard University and lead author of the study, said in the statement posted by Harvard-Smithsonian Center for Astrophysics (CfA). "We wondered: Where do they end up? How close do they come to us? We developed a computer code to answer those questions."
Girma, who referred to the recombined objects as "spitballs," noted that one of the masses -- some of which will reach masses somewhere in the neighborhood of an object like Neptune or even a Jupiter -- could be within about a few hundred light years from Earth. However, modern telescope technology is not sensitive enough to pick up its heat signature. Future detection instruments like the Large Synoptic Survey Telescope in northern Chile (full operations to begin in 2022) and the NASA/ESA's James Webb Space Telescope (set to launch in 2019) should be able to pick up these speeding missiles.
It should be noted that even though the masses might be planet-sized, they are not planet-like, as CfA researchers noted in the statement.
"It takes only a day for the black hole to shred the star (in a process known as tidal disruption) and only about a year for the resulting fragments to pull themselves back together. This is in contrast to the millions of years required to create a planet like Jupiter from scratch."
And if one those cosmic "spitballs" was sling-shot across the galaxy toward Earth? According to RT, scientists calculate it would take about 1 million years for the rogue to make the trip.
Still, Girma noted that her calculations showed that about 95 percent of all the planet-mass objects were hurled outside the galaxy.
But it is not just the Milky Way's central black hole that must be taken into account. Most galaxies house black holes at their core.
"Other galaxies like Andromeda are shooting these 'spitballs' at us all the time," co-author James Guillochon of the Harvard-Smithsonian CfA.
The challenge for future scientists will be to not just detect the potentially world-ending objects but to be able to differentiate them from free-floating worlds (rogue planets) that get created during star and planet formation.
"Only about one out of a thousand free-floating planets will be one of these second-generation oddballs," adds Girma.
Of course, the 20 million mph speed generated from a sling-shot around a black hole might give it away.
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