UFO'S of UAP'S, ASTRONOMIE, RUIMTEVAART, ARCHEOLOGIE, OUDHEIDKUNDE, SF-SNUFJES EN ANDERE ESOTERISCHE WETENSCHAPPEN

This NASA animation depicts a comet as it enters the inner solar system, with light from the sun warming the comet to create its coma and tail.

Credit: NASA/JPL-Caltech

There are a lot more big, potentially dangerous comets zooming through deep space than scientists had thought, a new study suggests.

Astronomers have likely underestimated by a factor of seven the number of "long-period" comets — those that take at least 200 years to complete one lap around the sun — that are at least 0.6 miles (1 kilometer) wide, according to the study.

"Comets travel much faster than asteroids, and some of them are very big," co-author Amy Mainzer, of NASA's Jet Propulsion Laboratory in Pasadena, California, said in a statement. "Studies like this will help us define what kind of hazard long-period comets may pose." [Best Close Encounters of the Comet Kind]

The study team, led by University of Maryland professor James Bauer, analyzed data gathered by NASA's Wide-field Infrared Survey Explorer (WISE) spacecraft.

This illustration shows how scientists used data from NASA's WISE spacecraft to determine the nucleus sizes of comets. They subtracted a model of how dust and gas behave in comets in order to obtain the core size.

Credit: NASA/JPL-Caltech

The data set includes observations of long-period comets and Jupiter-family comets. Long-period comets are thought to arise in the distant Oort Cloud, a spherical shell of icy bodies that begins perhaps 186 billion miles (300 billion km) from the sun, researchers said. The long-period comets that WISE spotted were likely booted inward, toward the sun, by gravitational interactions with other Oort Cloud denizens millions of years ago, the researchers added.

Jupiter-family comets are quite different beasts. They lie relatively close to the sun, completing one lap around the star in less than 20 years. (They are so named because Jupiter's powerful gravity has shaped their orbits.)

The WISE data revealed an unexpected abundance of long-period comets, the researchers said. For example, over an eight-month stretch, three to five times more of these objects zoomed by the sun than scientists had predicted.

"The number of comets speaks to the amount of material left over from the solar system's formation," Bauer said in the same statement. "We now know that there are more relatively large chunks of ancient material coming from the Oort Cloud than we thought."

The study team also determined that long-period comets are up to twice as large, on average, as Jupiter-family comets. The size discrepancy is likely a consequence of the Jupiter-family comets' more frequent trips past the sun, the researchers said: Every time these icy wanderers get close to Earth's star, the sun's intense heat drives off water and other volatile substances, which drag dust with them as they jet into space.

"Our results mean there's an evolutionary difference between Jupiter-family and long-period comets," Bauer said.

The WISE spacecraft launched to Earth orbit in December 2009 and successfully carried out an all-sky survey in infrared light. NASA put WISE into hibernation in February 2011 but reactivated the spacecraft two years later to search for asteroids and other near-Earth objects. (Mainzer is the principal investigator for this new mission, which is called NEOWISE.)

The new study, which was published earlier this month in The Astronomical Journal, looked at data the spacecraft gathered during its prime mission, in 2010.

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

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“Getting into character” as a method actor has an extra level of challenge when the plot of your movie includes encounters with extraterrestrials. Do you spend time begging to get into Area 51 or some secret Air Force base with the promise of helping those who let you in meet Sigourney Weaver? Or do the film’s producers only hire actors who have had close encounters – thus giving all of the good parts to Dan Aykroyd? Fortunately for the makers of the original Alien movie, they got both in Yaphet Kotto.

“I’ve never talked to anyone about it man, this is the first time. I’ve only told my wife, my rabbi, and a psychologist. This is the first time I’m talking about it.”

Yaphet as Parker (Syfywire)

According to a new interview with Vice, the 77-year-old Kotto was well-prepared to play Parker, the chief engineer who eventually (spoiler alert – you REALLY haven’t seen the original Alien?) gets killed by the alien. He claims he’s been seeing 6-foot tall beings with “elongated heads” since he was nine and the visits, along with other strange experiences, occurred on a regular basis into adulthood.

“Every time I moved into a house, above it at some point, there would be a circle of what looked like smoke. I’d wonder where it came from because it sure as hell didn’t look like clouds. Those sightings continued for a good ten to 15 years. I’ve also had time loss. I have a big loss of time between some of these moments, and I’d often wonder if I was taken”

Kotto’s encounters weren’t limited to the U.S. – his most moving experience took place in the Philippines. It occurred after being told by his wife and others that they had seen a “a UFO as big as the Yankee Stadium turned upside down” followed by a circle of smoke.

“They were freaking out. Two or three nights later, I saw it. The thing blotted out the entire sky. The moon and everything, it was huge.”

Since Kotto says he’s never told anyone in the media before about his alien and UFO experiences, it didn’t play a part in helping get cast as Parker in Alien. However, it affected him during the shooting.

“Now, I’ll admit, there were things that I alone found on the set of Alien—the spaceship. That mechanism that Sigourney Weaver throws to put the Sulaco (fictional spacecraft) on automatic destruct. There were symbols there. Symbols that had nothing to do with the ship in the film and I kept finding these symbols. They were like Egyptian symbols and I started trying to decipher them, which I was able to do.”

Sigourney and Yaphet ( The Viewer’s Commentary)

Speaking of Sigourney Weaver, while it doesn’t come up in Kotto’s interview, the star of the movie said in an interview in 2011 that she believes in aliens too.

“I think there are extraterrestrial life forms in the cosmos. I think it’s more likely than not. The cosmos is a pretty big place.”

She also believes in conspiracies.

“I think there’s a department in our (the US) government which is exclusively dedicated to quashing reports about aliens. And that’s so unfair. It would be nice if we weren’t just able to read about it in the tabloids.”

Kotto feels the same way.

“The former Canadian defense minister Paul Hellyer came out and said America is playing around. He’s got some video tapes out there talking about a number of species that come here. He puts America down for not admitting the fact that aliens are a reality. That gave me a lot of comfort.”

Perhaps it’s time for Yaphet and Sigourney to get together again, this time to discuss real aliens.