Asteroid smackdown.
Earth is in a constant game of celestial bumper cars, colliding with—and obliterating—the relatively puny space rocks that dare cross its path. The planet is still standing after 4.6 billion years, but a modern collision could devastate cities, continents, and even life itself. (Just ask the dinosaurs.) NASA’s Center for Near-Earth Object Studies keeps watch on more than 18,000 potential troublemakers, ranging from just 3 feet to more than 3,000 feet across. Meteorites smaller than 100 feet usually explode in midair, like one did over Chelyabinsk, Russia, in 2013. There wasn’t enough shrapnel to leave a crater, but the sonic boom did blast out windows. So how much havoc could larger rocks wreak?
Diameter 3,300 ft.
Lights out: This debris could throw enough dust to block out the sun—globally.
Impact energy 0.01 MT
Chelyabinsk: Russia’s airborne explosion was 20–30 times more powerful than Hiroshima.
Impact energy 1 MT
Kaboom: Equals about 11,000 tons of TNT. The Eiffel Tower weighs around 10,000.
100 million Avg. years between impacts:
The dino killer: These can obliterate nearly all life—but our odds look good.
Need for speed
One reason these flying objects are so dangerous is their velocity. A zippier asteroid can do more damage. And these things are fast—upwards of 44,000 miles per hour. All other factors (size, angle of entry, target) being equal, a faster asteroid can dig a bigger crater, and melt the rock it’s slamming into.
Tough stuff
Composition is key. Metal asteroids are durable enough to reach the surface even at small sizes, while carbon-rich rocks almost always break up in the atmosphere. The stony sort—which make up 94 percent of all meteorites—fall somewhere in between. But even a broken-up hunk of space junk can cause a dangerous shockwave in transit.
Location is everything
More than 70 percent of Earth is ocean. If an asteroid happened to make a water landing, it might be less harmful than if it struck populated land. Experts do have some (minor) concerns about a tsunami, which occurs when large amounts of water get displaced, but the real worry is a high-speed projectile launching dust from the seafloor high into the atmosphere.
When you look up into the sky on a clear night, you’ll see stars littered throughout the darkness. It may seem like a random pattern. But some people used those patterns to tell stories—and the stars still have uses for scientists today. A constellation is a group of stars that create a recognizable pattern in the sky. There are 88 officially recognized constellations, some of which are named after mythological creatures and might sound familiar if you’ve ever looked up your horoscope. Some of them are named after heroes like Hercules and Orion. Other star patterns are named after animals, like Ursa Major or the big bear. The stars acted as a way to preserve stories, like the legend of Perseus rescuing princess Andromeda from a sea monster named Cetus. Certain parts of the sky let you see the whole story from one constellation to the next. These constellations are used for more than just remembering stories.Explorers used constellations to navigate. Ursa Minor, or the littl...
The dust sculptures of the Eagle Nebula are evaporating. As powerful starlight whittles away these cool cosmic mountains, the statuesque pillars that remain might be imagined as mythical beasts. Featured here is one of several striking dust pillars of the Eagle Nebula that might be described as a gigantic alien fairy. This fairy, however, is ten light years tall and spews radiation much hotter than common fire. The greater Eagle Nebula, M16, is actually a giant evaporating shell of gas and dust inside of which is a growing cavity filled with a spectacular stellar nursery currently forming an open cluster of stars. This great pillar, which is about 7,000 light years away, will likely evaporate away in about 100,000 years.
BLACK HOLE FACTS Black holes are among the strangest things in the universe. They are massive objects – collections of mass – with gravity so strong that nothing can escape, not even light. The most common types of black holes are the stellar-mass and supermassive black holes. Stellar-mass black holes are created when massive stars explode, leaving behind a black hole with the mass of just a few suns. Supermassive black holes exist in the hearts of galaxies and usually contain the mass equivalent of millions of suns. Black holes are among the strangest things in the universe. They are massive objects – collections of mass – with gravity so strong that nothing can escape, not even light. The most common types of black holes are the stellar-mass and supermassive black holes. Stellar-mass black holes are created when massive stars explode, leaving behind a black hole with the mass of just a few suns. Supermassive black holes exist in the hearts of galaxies and usuall...
Comments
Post a Comment