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NASA Gets WISE to Long-Period Comets

Infrared data from WISE was used to identify the clouds of vaporized material around comets’ nuclei and then estimate their sizes. (NASA/JPL-Caltech)

Comets are the icy remnants left over from the formation of the Solar System. They circle the Sun in highly elliptical orbits that can range in length from several years to several million years, depending on their origin, and while they are usually quiet and dark when they get close enough to the Sun they are briefly heated enough to melt—technically sublimate—some of their frozen material, forming a cloud of gas and dust and a long tail sometimes big and bright enough to be visible from Earth.

But for the majority of their travels most comets are dark and difficult to spot, especially those originating from the Oort Cloud, an enormous spherical zone of icy debris surrounding our Solar System 186 billion miles away. Now, using infrared data from NASA’s WISE spacecraft, researchers have concluded that there are many more so-called “long period” comets visiting from the Oort Cloud than previously suspected—at least seven times more—and that they’re larger than we thought, too…many over half a mile across.

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Our Five-Trillion-Mile Close Call: the Star(s) That Skimmed the Solar System

Artist's rendering of two stars that made a close pass by the Sun 70,000 years ago. (Michael Osadciw/University of Rochester)

Artist’s rendering of two stars, a red dwarf and a brown dwarf, that made a close pass by the Sun 70,000 years ago. (Michael Osadciw/University of Rochester)

It’s like something out of a Hollywood film or a science fiction novel: a dark star sneaks up on Earth from just outside the Solar System, discovered too late to do anything about it (and really, what could we do?) and plows through the cloud of comets that surrounds the Sun like a haze of icy gnats, sending them flying everywhere… including on collision courses with Earth. Mass hysteria ensues.

Except that this isn’t just a story concept – scientists think this is actually something that happened 70,000 years ago! Minus the mass hysteria, of course… our ancestors were just beginning to settle down in the fertile lands of the Middle East after wandering out of Africa and would have had no idea what was happening at the edges of the Solar System (besides maybe a bright star occasionally flaring up in the night sky.)

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Tyche: Have We Marked the Spot of Planet X?

Is there giant hiding in the outer reaches of the solar system?

There’s been a lot of buzz lately about the existence of a “new” planet in our solar system, a gas giant that has eluded discovery by astronomers thus far because of its purported incredibly distant orbit – over 350 times farther from the Sun than Pluto, or a whopping 15,000 times farther from the Sun than Earth. The theory is that there’s something out there in the reaches of space that is sending comets into the inner solar system, knocking them out of the outer Oort Cloud with its massive gravity. See, not only is this “mystery planet” very, very far away, it is also theoretically very, very big – nearly four times the mass of Jupiter! Now considering that Jupiter is more massive than all of the other planets in our solar system combined….well, that would make this a very big – or at least, very massive – planet indeed. So if this is the case and there is something out there that is that big and is tossing comets at the rest of the planets like some oversized schoolyard bully, why haven’t astronomers seen it yet?

The short answer: it may not exist.

After an article published on Sunday, February 13 made public the hypothesis of this far-flung world – dubbed “Tyche” – astronomers everywhere have been quick to point out that no, there is no proof of this planet and never has been. The article stated that two scientists from the University of Louisiana at Lafayette believe that evidence for Tyche’s existence has already been gathered by NASA’s WISE infrared telescope, and the data just needs to be found. Now, while the WISE mission has captured literally millions of images of the sky in infrared over the course of its mission, identifying many deep-space objects as well as closer asteroids and comets, it has yet to locate any giant planets at the edges of our own solar system. And, according to many astronomers, it most likely will not.

In fact this concept is not new. The same two scientists had previously speculated that there was perhaps a small, dim star in distant orbit around the Sun, making our Sun one in a binary system. They called this dwarf star Nemesis, which was easily picked up by the media and doomsday sites as a harbinger of an Earth-ending apocalypse. When Nemesis didn’t materialize in any scientific observations, the idea got shelved until last year when they published another idea, this one about a large-mass planet far out beyond Pluto, within the giant cloud of icy worlds that, on occasion, fall inwards toward the Sun and become comets. (This planet they dubbed Tyche, who, in Greek mythology, was the much-more-pleasant sister of Nemesis.) While the concept is sound, considering the small amount of data available about the Oort Cloud, there is still no direct evidence that there is in fact anything so large out there. But, if there is, the scientists at the University of Louisiana will “be doing cartwheels.” One can imagine!

“Many people have speculated about such possibilities for a long time. It’s an intriguing idea because, well, it would be fun, to say the least.”

– Astronomer Mike Brown, self-confessed “planet killer”

Perhaps something will be found in the vast amounts of WISE data. Perhaps not. But this is how science works…something is observed, questions arise, hypotheses are made, followed by more focused observations to prove or refute said hypotheses…rinse, lather and repeat. Getting too excited about the hypotheses can distract from the actual process of discovery, which is a lot of hard work and doesn’t always lead to the desired “eureka” moment…and the media is awfully good at getting people excited about things (but not very good at actual science.) For now we’ll all just have to sit tight and see what comes of this, and even if it’s nothing it will undoubtedly lead to more of the right kind of questioning that makes real science happen.

Read more about this on Universe Today and Bad Astronomy.

Image above, by the way, is not Tyche or Nemesis or Planet X…it’s Jupiter in methane light, as seen by Cassini on its way to Saturn in 2000. I just added some grain and pixelization and removed the signature Great Red Spot. Credit: NASA / JPL / SSI. Edited by J. Major.

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