Comets are known to have a temper. As they swoop in from the outer edges of our solar system, these icy bodies begin spewing gas and dust as they venture closer to the sun. Their luminous outbursts can result in spectacular sights that grace the night sky for days, weeks or even months.
But comets aren't born that way, and their pathway from their original formation location toward the inner solar system has been debated for a long time. Comets are of great interest to planetary scientists because they are likely to be the most pristine remnants of material left over from the birth of our solar system.
In a study published inThe Astrophysical Journal Letters, a team of researchers including Kathryn Volk and Walter Harris at the University of Arizona Lunar and Planetary Laboratory report the discovery of an orbital region just beyond Jupiter that acts as a "comet gateway." This pathway funnels icy bodies called centaurs from the region of the giant planets Jupiter, Saturn, Uranus and Neptune into the inner solar system, where they can become regular visitors of Earth's neighborhood, cosmically speaking.
Roughly shaped like an imaginary donut encircling the area, the gateway was uncovered as part of a simulation of centaurs, small icy bodies traveling on chaotic orbits between Jupiter and Neptune.
Centaurs: Icy Rogues on Haphazard Trails
Centaurs are believed to originate in the Kuiper belt, a region populated by icy objects beyond Neptune and extending out to about 50 Astronomical Units, or 50 times the average distance between the sun and the Earth. Close encounters with Neptune nudge some of them onto inward trajectories, and they become centaurs, which act as the source population of the roughly 1,000 short-period comets that zip around the inner solar system. These comets, also known as Jupiter-family comets, or JFCs, include comets visited by spacecraft missions such as Tempel 1 (Deep Impact), Wild 2 (Stardust) and 67P/Churyumov-Gerasimenko (Rosetta).
"The chaotic nature of their orbits obscures the exact pathways these centaurs follow on their way to becoming JFCs," said Volk, a co-author on the paper and an associate staff scientist who studies Kuiper belt objects, planetary dynamics and planets outside our solar system. "This makes it difficult to figure out where exactly they came from and where they might go in the future."
Jostled by the gravitational fields of several nearby giant planets Jupiter, Saturn and Neptune centaurs dont tend to stick around, making for a high-turnover neighborhood, Harris said.
"They rattle around for a few million years, perhaps a few tens of millions of years, but none of them were there even close to the time when the solar system formed," he said.
"We know of 300 centaurs that we can see through telescopes, but that's only the tip of an iceberg of an estimated 10 million such objects," Harris added.
"Most centaurs we know of weren't discovered until CCD's became available, plus you need the help of a computer to search for these objects," Volk said. "But there is a large bias in observations because the small objects simply aren't bright enough to be detected."
Where Comets Go to Die
Every pass around the sun inflicts more wear and tear on a comet until it eventually breaks apart,has a close encounter with a planet that ejects it from the inner solar system, or its volatiles mostly gas and water are depleted.
"Often, much of the dust remains and coats the surface, so the comet doesn't heat up much anymore and it goes dormant," Harris said.
By some mechanism, a steady supply of "baby comets" must replace those that have run their course, "but until now, we didn't know where they were coming from," he added.
To better understand how centaurs become JFCs, the research team focused on creating computer simulations that could reproduce the orbit of 29P/Schwassmann-Wachmann 1, or SW1, a centaur discovered in 1927 and thought to be about 40 miles across.
SW1 has long puzzled astronomers with its high activity and frequent explosive outbursts despite the fact that is too far from the sun for water ice to melt. Both its orbit and activity put SW1 in an evolutionary middle ground between the other centaurs and the JFCs, and the original goal of the investigation was to explore whether SW1s current circumstances were consistent with the orbital progression of the other centaurs.
To accomplish this, the team modeled the evolution of bodies from beyond Neptunes orbit, through the giant planets region and inside Jupiters orbit.
"The results of our simulation included several findings that fundamentally alter our understanding of comet evolution," Harris said. "Of the new centaurs tracked by the simulation, more than one in five were found to enter an orbit similar to that of SW1 at some point in their evolution."
In other words, even though SW1 appears to be the only large centaur of the handful of objects currently known to occupy the "cradle of comets," it is not the outlier it was thought to be, but rather ordinary for a centaur, according to Harris.
In addition to the commonplace nature of SW1s orbit, the simulations led to an even more surprising discovery.
"Centaurs passing through this region are the source of more than two-thirds of all Jupiter-family comets," Harris said, "making this the primary gateway through which these comets are produced."
"Historically, our assumption has been that the region around Jupiter is fairly empty, cleaned out by the giant planet's gravity, but our results teach us that there is a region that is constantly being fed," Volk says.
This constant source of new objects may help explain the surprising rate of icy body impacts with Jupiter, such as the famous Shoemaker-Levy 9 event in 1994.
A Comet Worthy of Worship
Based on estimates and calculations of the number and size of objects entering, inhabiting and leaving the gateway region, the study predicted it should sustain an average population of about 1,000 Jupiter-family objects, not too far off the 500 that astronomers have found so far.
The results also showed that the gateway region triggers a rapid transition: once a centaur has entered it, it is very likely to become a JFC within a few thousand years, a blink of an eye in solar system timeframes.
The calculations suggest that an object of SW1's size should enter the region every 50,000 years, making it likely that SW1 is the largest centaur to begin this transition in all of recorded human history, Harris and Volk suggest. In fact, SW1 could be on its way to becoming a "super comet" within a few thousand years.
Comparable in size and activity to comet Hale-Bopp, one of the brightest comets of the 20thcentury, SW1 has a 70% chance of becomingwhat could potentially amount to the most spectacular comet humankind has ever seen, the authors suggest.
"Our descendants could be seeing a comet 10 to 100 times more active than the famous Halley comet," Harris said, "except SW1 would be returningevery six to 10 years instead of every 75."
"If there had been a comet this bright in the last 10,000 years we would know about it," Volk said.
"We take this as strong evidence that a similar event has not happened at least since then," Harris said, "because ancient civilizations would not only have recorded the comet, they may have worshiped it!"
The study was co-authored by Gal Sarid and Maria Womack, both of the Florida Space Institute and the University of Central Florida; Jordan Steckloff of the Planetary Science Institute and the University of Texas at Austin; and Laura Woodney of California State University.
More here:
Beyond Jupiter, Researchers Discovered a 'Cradle of Comets' - UANews
- Comet - Wikipedia, the free encyclopedia - November 21st, 2013 [November 21st, 2013]
- Comets - The Nine Planets - November 21st, 2013 [November 21st, 2013]
- Comets - Astronomy For Kids - KidsAstronomy.com - November 21st, 2013 [November 21st, 2013]
- Views of the Solar System: Comets - November 21st, 2013 [November 21st, 2013]
- Comets (extra footage) - Video - November 21st, 2013 [November 21st, 2013]
- Solar flare update. 6 comets! Nov 28th ISON perihelion! - Video - November 21st, 2013 [November 21st, 2013]
- Comets game 2end goal - Video - November 21st, 2013 [November 21st, 2013]
- Missouri Comets vs. Milwaukee Wave - Video - November 21st, 2013 [November 21st, 2013]
- Football: Comets Advance Past Momence - Video - November 21st, 2013 [November 21st, 2013]
- Caliber Cheer Comets Nov 9 2013 - Video - November 21st, 2013 [November 21st, 2013]
- Two Comets Are About to Fly By Mercury | NASA Space Science HD Video - Video - November 21st, 2013 [November 21st, 2013]
- Comets win on tiebreaker - December 20th, 2013 [December 20th, 2013]
- Comets fend off Wildcat attack - December 20th, 2013 [December 20th, 2013]
- Free throws bring Comets down - December 20th, 2013 [December 20th, 2013]
- Comets continue solid play on their home ice - December 20th, 2013 [December 20th, 2013]
- Comets Beat Heat 4-2 - December 20th, 2013 [December 20th, 2013]
- Comets in the Community - December 20th, 2013 [December 20th, 2013]
- Comets pick up third straight win over Heat - December 20th, 2013 [December 20th, 2013]
- Comets Welcome Back Old Rival - December 20th, 2013 [December 20th, 2013]
- Comets Cool Abbotsford 4-2 - December 20th, 2013 [December 20th, 2013]
- Comets – Facts and Information about Comets | Space.com - December 20th, 2013 [December 20th, 2013]
- Comets v Wave 121313 Highlights - Video - December 20th, 2013 [December 20th, 2013]
- Highlights - Comets vs. Monsters 12/15/13 - Video - December 20th, 2013 [December 20th, 2013]
- Weekly Space Hangout - Preventing Asteroids, More Comets, Worldview Balloon - Video - December 20th, 2013 [December 20th, 2013]
- Pens 1 - Comets 0 - Video - December 20th, 2013 [December 20th, 2013]
- Milwaukee Waves Cheap Shot Vs. Missouri Comets - 12.13.13 - Video - December 20th, 2013 [December 20th, 2013]
- Hometown Nights - Tarso Miller and the Wild Comets - Video - December 20th, 2013 [December 20th, 2013]
- Hangout with Comets Nova and Deathlyhall - Video - December 20th, 2013 [December 20th, 2013]
- Comets vs St. Louis Ambush - Video - December 20th, 2013 [December 20th, 2013]
- Shake, Rattle and Roll Bill Haley and His Comets - Sheet Music - Easy Alto Sax Version - Video - December 20th, 2013 [December 20th, 2013]
- Comets Shut Out Heat 3-0 - December 21st, 2013 [December 21st, 2013]
- Administration - December 21st, 2013 [December 21st, 2013]
- Bill Haley And His Comets ' R-O-C-K' 78 rpm - Video - December 21st, 2013 [December 21st, 2013]
- Bill Haley And His Comets ' The Saints Rock 'N Roll' 78 rpm - Video - December 21st, 2013 [December 21st, 2013]
- Nicklas Jensen's Shootout Winning Deke 12-15-13 - Video - December 21st, 2013 [December 21st, 2013]
- Missouri Comets Night with Miles - 12.13.13 - Video - December 21st, 2013 [December 21st, 2013]
- 12/13/13 Comets 5 vs. Senators 2 - Video - December 21st, 2013 [December 21st, 2013]
- Comets rock Bulldogs for first win - December 22nd, 2013 [December 22nd, 2013]
- Comets Deposit Life's Building Blocks Across the Cosmos!(Dr.Ruehl) - Video - December 22nd, 2013 [December 22nd, 2013]
- Comets beat AHL rival Abbotsford again with shutout - December 23rd, 2013 [December 23rd, 2013]
- Comets Win Streak Grows to Four Games - December 23rd, 2013 [December 23rd, 2013]
- Comets Corner: On the Mask - December 23rd, 2013 [December 23rd, 2013]
- 'Comets of the Centuries': 500 Years of the Greatest Comets Ever Seen - December 23rd, 2013 [December 23rd, 2013]
- Hackensack High School (NJ) Football Home - MaxPreps.com - December 23rd, 2013 [December 23rd, 2013]
- Little Comets - Isles (Music Video) - Video - December 23rd, 2013 [December 23rd, 2013]
- Comets Have Two Players on MISL Team of Week - December 25th, 2013 [December 25th, 2013]
- ONE FOR THE RECORD DECEMBER 20 2013 21 FUKUSHIMA COMETS EARTHQUAKES NMR GZ PAUL AND BP - Video - December 25th, 2013 [December 25th, 2013]
- Comets in the Community: Christmas at St. Luke's - December 26th, 2013 [December 26th, 2013]
- Best comets of last 500 years - December 26th, 2013 [December 26th, 2013]
- STRANGE EVENTS In 2013 Earthquakes, Mass Animal Deaths, Extreme Weather, OORT Cloud Comets - Video - December 26th, 2013 [December 26th, 2013]
- Utica Comets " 'Twas the Night" - Video - December 26th, 2013 [December 26th, 2013]
- Missouri Comets vs. Rochester Lancers - Video - December 26th, 2013 [December 26th, 2013]
- Chasing Comets: In search of secrets about our origins - Video - December 26th, 2013 [December 26th, 2013]
- DREAM X2 COMETS/STARS FLYING OVERHEAD, MASSIVE SONIC BOOMS EARTH HIT POSSIBLY. - Video - December 26th, 2013 [December 26th, 2013]
- What are comets? - Video - December 26th, 2013 [December 26th, 2013]
- Game Preview: Syracuse Silver Knights at Missouri Comets and St. Louis Ambush - December 27th, 2013 [December 27th, 2013]
- Clark's performance boosts Clayton over Moss Point - December 27th, 2013 [December 27th, 2013]
- Gameday: Comets vs. Binghamton - December 27th, 2013 [December 27th, 2013]
- Comets Battle for First Place - December 27th, 2013 [December 27th, 2013]
- Gameday: Comets vs. Hamilton - December 28th, 2013 [December 28th, 2013]
- Comets fall to Senators - December 28th, 2013 [December 28th, 2013]
- Comets end winning streak - December 28th, 2013 [December 28th, 2013]
- Comets vs Syracuse Silver Knights - Video - December 28th, 2013 [December 28th, 2013]
- Winning Comets Soccer - Video - December 28th, 2013 [December 28th, 2013]
- Comets Lose in Final Minutes - December 29th, 2013 [December 29th, 2013]
- CometsTV: 12-27-13 Utica Comets vs. Binghamton Senators Highlights - Video - December 29th, 2013 [December 29th, 2013]
- Comets knock off Aquin for second time this season - December 31st, 2013 [December 31st, 2013]
- Comets fall after late rally - December 31st, 2013 [December 31st, 2013]
- CometsTV: 12-28-13 Utica Comets vs. Hamilton Bulldogs Highlights - Video - December 31st, 2013 [December 31st, 2013]
- Comets Corner: Kellan Lain - January 1st, 2014 [January 1st, 2014]
- Comets Welcome New Year - January 1st, 2014 [January 1st, 2014]
- Comets Media Game 2013 - Video - January 1st, 2014 [January 1st, 2014]
- 1957 AMI H200 playing Bill Haley and his Comets Rock Around The Clock. - Video - January 1st, 2014 [January 1st, 2014]
- 7 Amazing Christmas Kinder Surprise Eggs SMURFS cars, comets Unwrapping Review Chocolate Easter Toys - Video - January 1st, 2014 [January 1st, 2014]
- Shootout - Dogs @ Comets - 12/2813 - END - Video - January 1st, 2014 [January 1st, 2014]
- Shootout - Dogs @ Comets - 12/2813 - Video - January 1st, 2014 [January 1st, 2014]
- Catonsville girls basketball shows promise for another strong season - January 2nd, 2014 [January 2nd, 2014]
- Gameday: Comets vs. Lake Erie - January 2nd, 2014 [January 2nd, 2014]
- Comets Kick off New Year with Exciting Win - January 2nd, 2014 [January 2nd, 2014]
- Comets Remain Hot at Home with 3-2 Decision over Lake Erie - January 2nd, 2014 [January 2nd, 2014]