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.
On July 27, 2011, scientists announced the discovery of a small asteroid that shares its orbit with Earth: 2010 TK7, a 1,000-foot-wide asteroid, precedes our planet within the same path we take around the Sun. It’s currently located about 50 million miles away in a position known as a Lagrange point (L4, to be exact) where the pull from the Earth, Sun and Moon even out to create a stable gravitational region.
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This mesmerizing animation by Scott Manley illustrates the procession of asteroid discoveries from 1980 – 2010, illuminating each as they were spotted and categorized. The colors indicate how closely the asteroids come to the inner solar system… Earth-orbit-crossers are red, Earth-approachers are yellow and all the others are green.
The date counter runs in the lower left of the video.
A couple of interesting things to notice: one, most discoveries occur in groups as the asteroids are on the opposite side of the Earth from the Sun (which makes sense considering the lighting achieved) and two, as new methods of locating asteroids are developed (such as automated scanning systems in the 90s and the WISE infrared telescope in early 2010) the incidence of new discoveries rises dramatically.
The video runs at a scale of 60 days per second, and at 1080p resolution it corresponds to about 1 million km per pixel.
This shows that there are quite a lot of smaller worlds in our solar system…over half a million at current count! And it’s estimated that there may be a billion asteroids larger than 100 meters orbiting the Sun between Mars and Jupiter. Still, the image of the sci-fi “asteroid belt” filled with tumbling rocks in space isn’t accurate… these worlds are still very far apart, and although they do occasionally collide with each other it’s very likely that if you were to stand on the surface of an asteroid you wouldn’t even be able to see the next closest one!
As NASA’s Dawn spacecraft closes in on the asteroid Vesta – the second-largest one in the entire belt – we are getting a better look at these ancient worlds, each a new discovery in itself! And as this animation shows, there’s lots to be discovered.
Credit: Scott Manley. Orbital elements were taken from the ‘astorb.dat’ data created by Ted Bowell and associates at ftp://ftp.lowell.edu/pub/elgb/astorb.html. Music is ‘Transgenic’ by Trifonic.
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.
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.
NASA’s Wide-field Infrared Survey Explorer – WISE – has recently finished a survey of small bodies in our solar system. The survey mission, called NEOWISE (for Near Earth Objects), used WISE’s infrared-imaging capabilities to identify 20 new comets and more than 33,000 main-belt asteroids. WISE also spotted 134 near-Earth objects – asteroids or comets that come within 28 million miles of Earth’s orbit.