• How to 'hear' Russian meteor blast

    By Becky Oskin, OurAmazingPlanet

    A new recording lets human ears listen in on the largest infrasound blasts ever recorded, created by the meteor that exploded over Russia last week.

    Infrasonic waves from the Russian meteor fireball were picked up by 17 infrasound stations around the world, part of a network for detecting nuclear weapon explosions. Stations as far away as Antarctica tracked the blast's low-frequency waves as they traveled through Earth's atmosphere.

    The signal was filtered and sped up 135 times to make it audible to human ears, according to the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), which runs the stations. [Listen to the recording]

    The meteor blast was not a fixed explosion, Pierrick Mialle, an acoustic scientist for the CTBTO, said in a statement. Instead, the meteor was traveling faster than the speed of sound, burning up as it went. "That's how we distinguish it from mining blasts or volcanic eruptions," he said.

    Mialle said that scientists around the world will use the infrasound data to learn more about the meteor's final altitude, how much energy it released and how it disintegrated.

    Based on scrutiny of infrasound records, NASA scientists initially concluded the fireball released about 300 kilotons of energy, Bill Cooke, head of the Meteoroid Environments Office at NASA's Marshall Space Flight Center in Huntsville, Ala., said Feb. 17.

    Reach Becky Oskin at boskin@techmedianetwork.com. Follow her on Twitter @beckyoskin. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.

    © 2012 OurAmazingPlanet. All rights reserved. More from OurAmazingPlanet.

  • Another meteor? 'Fireballs' light up Florida sky

    View more videos at: http://nbcmiami.com.

    By Juan Ortega and Gilma Avalos, NBCMiami.com

    South Floridians who happened to be looking in the right place at the right time Sunday night saw one spectacular light show – possibly a sporadic meteor.

    The Coast Guard began getting flooded with phone calls about 7:30 p.m., with reports of folks seeing flare-like objects from Jacksonville to Key West, according to Coast Guard Petty Officer 3rd Class Sabrina Laberdesque.

    People called in, describing the flares “as orange or red fireballs in the sky,” Laberdesque said. The display was limited to the sky: No injuries were reported, Laberdesque said.

    A sporadic meteor is basically a rocky object that comes from the asteroid belt, said Mike Hankey, operations manager for the American Meteor Society, based in Genesee, N.Y. The group logged 27 reports within about the first two hours of the event, he said.

    "This is a lot of reports to come in quickly," Hankey said. 

    Gauging by the reports, it happened somewhere over the ocean.

    "These fireballs are common," Hankey said. "It’s rare for any one person to see one more than once or twice in their lifetime. But on any given night, it might happen somewhere in the globe a few times in a day."

    Hankey added: "People should not be scared of the sky falling or anything at all."

    Amanda Mayer, of West Palm Beach, said she saw something in the sky and said she thought it was somebody flashing a light. She said she hit record on her camera.

    "I was like, 'Wow! That's weird," Mayer said. "I just started videotaping, and that's when it happened."

    More news from NBCMiami.com

    It turned out to be good timing: The ball of light appeared as she recorded, she said.

    "I was pretty sure it was a meteor because of everything else that's been happening," Mayer said.

    The Coast Guard said it had suspected Sunday's sighting was a meteor shower, but Hankey disagreed. "Meteor showers usually are much dimmer and faster moving," Hankey said. 

    After a meteor exploded overhead near Chelyabinsk, Russia, on Friday, reportedly injuring more than 1,000 people, many people elsewhere in the world have wrongly thought that streaks they've seen in the sky, including planes, are meteors, Hankey said.

    Traveling at 33,000 mph, a massive meteor hit the Earth's atmosphere creating a giant shockwave that blew out windows of glass, injuring nearly 1,000 people and creating panic. On the same day, an asteroid half the size of a football field came within 17,000 miles from Earth. NBC's Tom Costello reports.

    "We’re getting a lot more false reports," Hankey said.

    But with false reports, the group tends to receive only one report describing an incident, Hankey said. If the same event is reported over and over in five or 10 minutes, then that’s more likely to be "a legitimate event,” or sporadic meteor, Hankey said. 

    In South Florida Sunday night, the Coast Guard found that the light streak vanished in an instant. The Coast Guard sent out a helicopter to check out a report of a flare near the MacArthur Causeway in Miami, but found nothing there, Laberdesque said.

    Related:

    Fireball over N. California causes stir

  • Fireball over N. California causes stir

    Traveling at 33,000 mph, a massive meteor hit the Earth's atmosphere creating a giant shockwave that blew out windows of glass, injuring nearly 1,000 people and creating panic. On the same day, an asteroid half the size of a football field came within 17,000 miles from Earth. NBC's Tom Costello reports.

    By Gil Aegerter, NBC News

    A fireball streaking across the Northern California sky Friday night brought a flood of witness reports -- the same day that a meteor exploded over Russia and an asteroid made a near-Earth fly-by.

    The fireball was seen around 7:45 p.m., by witnesses as far north as Fairfield and as far south as Gilroy, NBCBayArea.com reported. It was also reportedly seen in Sacramento and Walnut Creek. NBC station KSBW of Monterey said the object was visible along California's Central Coast, too.

    NBCBayArea.com said Candice Guruwaiya gave this account on Facebook of seeing it in San Jose: "I was leaving Safeway on Branham and Snell when I saw it. ... It was a bright green when it first appeared, then it went to a bright yellow. It was awesome!"

    The fireball was seen about 24 hours after a meteor exploded over Russia's Chelyabinsk region and a 150-foot-wide asteroid came within 17,200 miles of Earth.

    An astronomer at the Chabot Space and Science Center in Oakland told NBCBayArea.com that Friday night's event wasn't related to the asteroid's passing:

    Gerald McKeegan, an astronomer at Chabot, said he did not see it, but based on accounts he thinks it was a "sporadic meteor," which can happen several times a day but  most of the time happens over the ocean, away from human eyes. Sporadic meteors bring as much as 15,000 tons of space debris to Earth each year, according to McKeegan. He explained that meteors, which are hunks of rock and metal from space that fall to Earth, burn up as they go through Earth's atmosphere, which is what apparently  caused tonight's bright flash of light.

    He said it was likely smaller than another meteor that landed in the Bay Area in October, which caused a loud sonic boom as it fell, breaking apart and spreading rocks, called meteorites, in the North Bay.

    More about the cosmic hits (and near-misses):

    Astrophysicist Neil deGrasse Tyson, director of the Hayden Planetarium, speaks to NBC's Lester Holt about the meteor and asteroid that approached Earth on Friday.

  • Russian meteor explosion outshone sun

    Traveling at 33,000 mph, a massive meteor hit the Earth's atmosphere creating a giant shockwave that blew out windows of glass, injuring nearly 1,000 people and creating panic. On the same day, an asteroid half the size of a football field came within 17,000 miles from Earth. NBC's Tom Costello reports.

    By Miriam Kramer, SPACE.com

    The fireball that exploded over Russia Friday morning provided onlookers with an incredible spectacle, even outshining the sun for a brief period, scientists say.

    The meteor exploded just above the city of Chelyabinsk just before 9:30 a.m. local time, damaging hundreds of buildings and injuring more than 1,000 people. The blast probably released about 300 kilotons of energy, sending out a powerful shock wave and lighting up the daytime sky, researchers said.

    "This event must have been brighter than the sun, if you were there to watch it," Paul Chodas, a scientist with the Near Earth Object Program Office at NASA's Jet Propulsion Laboratory in Pasadena, Calif., told reporters today. "It's just incredible."

    The object that caused the Russian meteor was probably about 50 feet (15 meters) wide and weighed approximately 7,000 tons, said Bill Cooke of NASA's Marshall Space Flight Center in Huntsville, Ala. [See Photos of the Meteor Streaking over Russia]

    This space rock exploded 12 to 15 miles (19 to 24 kilometers) above Earth's surface, releasing roughly 15 times as much energy as the atomic bomb the United States dropped on the Japanese city of Hiroshima during World War II.

    The resulting blast shattered windows and knocked down walls, according to media reports.

    Dr. Paul Chodas at NASA's Jet Propulsion Laboratory discussed the asteroid that flew by Earth  and the fireball that struck Russia. Choda called it "a huge coincidence."

    "When you hear about injuries, those are undoubtedly due to the shockwave," Cooke said.

    The fireball hit Earth's atmosphere at about 40,000 mph (64,374 kph) and left a trail 300 miles (483 kilometers) long in the sky, he added.

    Although the explosion did shoot fragments of the rock toward the ground, there have been no confirmed reports of recovered pieces of the space rock, Cooke said.

    Scientists have a particularly difficult time tracking small asteroids like the one that exploded earlier today because they are so small and dim. The Russian meteor was particularly difficult to spot because it came from the daylight side of the planet. Telescopes can only detect meteors in the dark, Cooke said.

    Space rocks like the Russian fireball hit the Earth once every 50 to 100 years, he added.

    Most asteroids are loose masses of rock, and NASA experts think this meteor probably fit that description. As the fireball entered the atmosphere, it started to break apart and eventually exploded when the heat generated by its dramatic plunge toward the Earth's surface became too great.

    AFP

    This video still image shows the smoke trail created by the meteor that exploded over the Chelyabinsk region of Russia on Feb. 15, 2013.

    This is the most powerful meteor explosion of its kind since the Tunguska Event 1908, researchers said. The meteor that exploded that year over the Tunguska region of Russia's Siberia was probably 130 feet (40 m) in diameter and flattened 825 square miles (2,137 square km) of forest.

    A meteor similar to today's fireball exploded in the air over Indonesia in 2009, but it didn't cause nearly this amount of damage. This most recent meteor explosion was probably four to five times more powerful than the 2009 event, Cooke said.

    By coincidence, the Russian fireball exploded on the same day that the 150-foot-wide (45 m) asteroid 2012 DA14 cruised within 17,200 miles (27,000 km) of Earth. 2012 DA14's flyby was the closest by such a large asteroid that scientists have ever known about in advance. The two space rocks that made big news today are completely separate bodies, Cooke and Chodas stressed.

    Follow Miriam Kramer on Twitter @mirikramer or SPACE.com @Spacedotcom. We're also on Facebook & Google+. 

    Copyright 2013 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

  • Russia gets rude welcome to 'fireball month'

    EUMETSAT

    The meteor that exploded over the Urals of central Russia was seen by Meteosat-9, at the edge of the satellite view. This image was taken on Friday.

    By Tanya Lewis
    Space.com

    It's fireball season on Earth, and it is starkly clear for residents in eastern Russia where a bright fireball exploded in the atmosphere early Friday.

    For reasons scientists don't quite understand, there appears to be an increase in the number of bright meteors visible blazing through the night sky during the month of February. The notion hit home today when a meteor exploded over Russia's Ural Mountains, injuring more than 900 people and damaging thousands of buildings, according to news reports. (Another space rock, the asteroid 2012 DA14, is on course to pass very close to Earth Friday evening, but will not hit the planet.)

    On a typical night of the year, stargazers might see about 10 "sporadic" fireballs, created by fragments of asteroids or comets that burn up in the Earth's atmosphere. But that number spikes by 10 to 30 percent during the spring. The fireballs come from the asteroid belt, but their exact source remains unknown.

    Meteor enthusiasts have known about the "Fireballs of February" since the 1960s and 70s, when amateur astronomers noticed many more bright, sound-producing streaks than usual. Follow-up studies during the 1980s failed to show any increase in the rate of fireballs, but a 1990 study suggested otherwise.

    Astronomer Ian Holliday studied photographic records of roughly a thousand fireballs from the 1970s and 80s, finding what looked like a fireball stream crossing Earth's orbit during February, late summer and fall. Halliday's results are somewhat controversial, but the phenomenon appears real.

    The February fireball increase is somewhat puzzling because the number of ordinary meteors normally peaks during autumn in the Northern Hemisphere, according to researchers at NASA's Meteoroid Environment Center. The two most visible meteor showers most years, the Perseid meteor shower and the Leonid meteor shower, peak in mid-August and mid-November.

    Scientists are probing the mystery of the spring surge in fireballs using NASA's All-Sky Fireball Network, a slew of cameras designed to observe meteors brighter than the planet Venus. The data collected could reveal where these fireballs come from, scientists say. Modeling the meteoroid environment will also benefit spacecraft designers.

    Follow Space.com on Twitter @Spacedotcom. We're also on Facebook  and Google+.

    Copyright 2013 Space.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.