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See also Mike Brown’s Sedna page, Wikipedia, Universe Today, Nine Planets, NASA and here, SEN•Com, New (Dwarf) Planets okay, Plutoids, Eris, Sedna, Centaurs & Kuiper Belt Objects
And Mike Brown’s Planets, and his book How I Killed Pluto and Why It Had It Coming, “Snow White” (2007 OR10) and Petition to name 2007 OR10 as “Gebeleizis”
Dwarf planets are Ceres, Eris, Haumea, Makemake and Pluto; probable dwarf planets are (225088) 2007 OR10, Sedna, Quaoar, (55565) 2002 AW197, Orcus and 2012 VP113.
Discovery images of Sedna
On 15th March 2004, astronomers from Caltech, Gemini Observatory, and Yale University announced the discovery of the coldest, most distant object known to orbit the sun. The discovery was made on the Samuel Oschin Telescope at the Palomar Observatory east of San Diego on 14th November 2003 by the team of Mike Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale). See the discovery paper.
Because of its frigid temperatures, the team named the object Sedna, after the Inuit goddess of the sea from whom all sea creatures were created.
Officially known as 2003 VB12, this object is the most distant body known that orbits our Sun. It is at present over 90 AUs away, three times as far as Pluto. Sedna is about 1800 km in diameter, slightly smaller than Pluto. Perhaps the most interesting aspect of Sedna is its orbit. Though it is not yet known to a high precision it is clear that Sedna’s orbit is highly elliptical with a perihelion of about 75 AU and an orbital period of about 10,500 years. This puts it well beyond the Kuiper Belt and yet well inside what was thought to be the inner edge of the Oort Cloud.
Sedna’s physical composition is a bit of a mystery. You would expect it to be mostly ices but apparently that’s not the case. About all that’s known at this time is that it is very red and that water and methane ices seem to be absent from the surface.
Sedna is definitely not the Planet X that many astronomers anticipated before the discovery of Pluto. Planet X was supposed to be a much larger object. Sedna is not even officially a planet at all. That classification decision is up to the IAU and they are not likely to decide to do so.
When the first announcment of the discovery of Sedna, there was circumstantial evidence that there is a moon around Sedna. Soon after, images were taken by the Hubble Space Telescope. Much to the discoverer’s surprise no moon was visible!
Artist’s impression of the view from Sedna, with its supposed moon
The evidence for the existence of a moon is circumstantial, but nonetheless compelling. The story is a little complicated, though, and it goes like this:
We have found that Sedna systematically gets a little brighter and a little fainter every 20 days or so. We think this is because there are bright and dark spots on the surface of Sedna and Sedna is rotating once every 20 days or so.
Most planets and asteroids rotate much more quickly. The earth rotates in 24 hours, Jupiter and Saturn rotate in about 10 hours, and many asteroids rotate in just a handful of hours. Why is Sedna so different?
The answer perhaps can be found by thinking about Pluto. Pluto, too, has an unusually slow rotation: about six days. For many years this slow rotation was a mystery until it was realized that Pluto has a large moon, Charon, which revolves around Pluto once every six days. We now understand that Pluto once rotated more quickly, but Charon’s tug on Pluto has, over time, slowed the rotation of Pluto until now Pluto finally rotates as slowly as Charon revolves around it.
The same process could explain why Sedna rotates unusually slowly. If Sedna has a large moon which revolves around it with a 20-day or so orbital period that moon would have slowed Sedna’s initially faster rotation and given the unusually slow rotation seen today. (As an interesting aside, this also happens on the earth! The moon is gradually slowing the earth’s rotation over time. Over a typical person’s lifetime, the earth day gets longer by about one one-thousandth of a second.)
We can think of four possibilities for why we do not see a moon around Sedna.
Perhaps the brightening and dimming that we think we see are not real. Measurements in science are never perfect, and perhaps some of these imperfections have, by bad luck, led us to believe that we are measuring Sedna’s rotation when we are really not. From our understanding of the measurements, we can estimate that there is about a 1 in 20 chance of this type of bad luck. We thus think it is unlikely, but, again, we can’t rule it out.
Perhaps the measurement is real, but we are being fooled. Imagine that you look at a clock once every twenty-five hours. How fast would you think the hands were turning? The first day the clock would say noon. The second day 1pm. The third day 2pm. You might think the clock only moved 1 hour per twenty-five hours. Perhaps the same thing is happening with Sedna: Our measurements were made approximately every 24 hours, so if Sedna rotates every 25 hours, then every time we look it appears to have only rotated a little, and we think it takes 24 days to make a full rotation. This possibility cannot be ruled out with the current data, though it would require the unusual coincidence that Sedna’s rotation period would have to be unusually close to the earth’s rotation period!
Understanding which of these possibilities is correct will be possible from additional observations of Sedna. The two types of observations that we would most like to see are:
Here is an image of the orbit and position compared to all the known solar system objects. The sun is in the middle of the swarm of solar system objects. You can see that Sedna is at 90 AU (1 AU is an Astronomical Unit, the distance between the earth and the Sun, about 150 million kilometres, or 93 million miles).
Don’t miss the video, put together by Robert Hurt at the Spitzer Science Center, showing a zoom out from the earth to Sedna to the Oort cloud.
No. Sedna never enters the region of the Kuiper belt. The Kuiper belt is an icy asteroid belt just beyond Neptune. Extremely strong evidence shows that it has a rather sharp edge at 50 AU. Sedna never comes close than 76 AU. Calling Sedna an inner Oort cloud object makes much more sense.
There are some KBOs that go very far from the sun like Sedna does, but they all have closest approach at about 35 to 45 AU. Sedna is special because it doesn’t come any closer than 75 AU to the sun. This is probably because of the effects of passing stars.
A second speculative explanation for Sedna’s orbit is that a larger body, perhaps Mars-sized or larger could exist at around 70 AU in a circular orbit and could have caused Sedna to get thrown into its strange orbit. If such a planet existed, the discovery team would likely have already found it in their survey, though there are still a few places left to hide.
The Oort cloud is a hypothetical shell of icy proto-comets in very loose orbits around the sun, that extends to a distance of almost halfway to the nearest star. Occasionaly, passing stars cause a slight change in the orbit of one of these proto-comets which causes them to come streaking in to the inner solar system where we see them as comets. Though the Oort Cloud has never been seen directly, the comets that we do see are very strong evidence of its existence. As can be seen in the graphic above, though, the Oort cloud is expected to be much much further out than the orbit of Sedna. So why do we think Sedna is a member of the Oort cloud? We believe that the existence of Sedna is evidence that the Oort cloud actually extends much further in towards the sun than previously thought. This “inner Oort cloud” was formed in the same manner as the previously known “outer Oort cloud”. Early in the history of the solar system many many small icy bodies were orbiting the sun and getting sling-shot out by close encounters with planets. As they were travelling further and further from the sun, the orbits of these bodies were affected by distant stars, causing them to slow down and stay attached to the sun. Sedna probably suffered a similar fate, except the stars which affected it must have been much much closer than previously expected. We believe that this is evidence that the sun formed in a tight-knit group along with many other stars.
Technology is the reason. Clyde Tombaugh discovered Pluto in 1930 using photographic plates, which let you look at a very wide piece of the sky, but they are not nearly as sensitive as the CCDs that we use now. (A CCD is what you will find inside most digital cameras.) The new, large objects listed above tend to be just faint enough that they would be out of range of all the older surveys for moving objects done after Tombaugh’s. Today, CCDs are getting large enough and computers are getting fast enough that it is significantly easier to find these types of planetoids than it was even five years ago. The discovery team used a 172-megapixel camera mounted on a robotic telescope to find these things. Even about five years before, such cameras were not available, and the computing power to analyze these cameras was not quite there either.
It is very likely that there are more inner Oort cloud objects like Sedna. The team looked at only 15% of the sky before finding Sedna. As they continue to look, they may find a few more objects like Sedna. But this is only the beginning. Kepler’s law states that an object on a very elliptical orbit like Sedna spends most of its time farthest from the Sun. Thus, for every Sedna we find near closest approach, there should be many more very far from the Sun that we can’t see because they are so far away and faint. Also, Sedna is rather large, about 1/2 to 3/4 the size of Pluto. Most solar system populations like the Kuiper belt objects and the asteroids actually have many more smaller objects than large objects. So, for every Sedna we find that is large, there should be many more that are small that were missed because they were faint. Although it is very difficult to make predictions from one object, it seems very likely that the inner Oort cloud will have thousands of times more objects than just Sedna. It is likely that there is more mass in the inner Oort cloud than in the Kuiper belt and the asteroid belt combined.
2003 VB12 was the official temporary designation of the International Astronomical Union (IAU) Minor Planet Center, based on the year (2003) and date (14th November is the 22nd 2-week period of the year – thus V, the 22nd letter of the alphabet; after that it is sequentially lettered) based on the announcement of discovery. Once the orbit of 2003 VB12 is known well enough (usually after about a year), the discoverers recommended to the IAU Committee on Small Body Nomenclature – which is responsible for solar system names – that it be permanently called Sedna (this has now happened). This newly discovered object is the coldest most distant place known in the solar system, so they felt it was appropriate to name it in honor of Sedna, the Inuit goddess of the sea, who is said to live at the bottom of the frigid Arctic Ocean. They furthermore suggested to the IAU that newly discoverd objects in this inner Oort cloud all be named after entities in Arctic mythologies.
Sedna is the most distant solar system object yet discovered. It is twice as far from the sun as any other solar system object and three times farther than Pluto or Neptune. Standing on the surface of Sedna, you could block the entire sun with the head of a pin held at arm’s length. Even more interestingly, the orbit of Sedna is extremely elliptical, in contrast to all of the much closer planets, and it takes 10,500 years to circle the sun.
In the discovery images, we see only a point of light. We can’t directly measure the size of Sedna from this point. The light that we see has travelled from the sun, been reflected off the surface of Sedna, and come back to us where we can see it in the images like the discovery images at the top of this page. So a small icy object and a large coal-covered object, for example, would both look about the same brightness in the discovery images, because both objects could reflect about the same amount of sunlight.
We can measure Sedna’s size using a thermal telescope, which measures the heat coming from the surface. We know how far away Sedna is, so we know that the surface temperature is about 400 degrees below zero Fahrenheit (some 30 K). A large object of that temperature will give off much more heat than a small object of that temperature. (A lighted match and a bonfire are the same temperature, but a bonfire keeps you much warmer at night because it is so much bigger). In collaboration with Frank Bertoldi at the MPIfR Bonn, the discovery team used the 30-metre diameter IRAM telescope, and in collaboration with John Stansberry at the University of Arizona and Bill Reach at the Spitzer Science Certer, they used the Spitzer Space Telescope. Sedna was too small to be detected in either. This tells us that Sedna is at most about 1800 km in diameter: about halfway in size between Pluto and the largest known Kuiper belt object, Quaoar. Even though all we know for certain is that Sedna is smaller than 1800 km, we have evidence which suggests that the size might be pretty close to this number. We are virtually certain that the size is larger than the 1250 km size of Quaoar, though this object has shown many unexpected characteristics, so we can’t completely rule out a smaller size.
The team that discovered Sedna have been conducting an ongoing survey of the outer solar system using the Palomar QUEST camera and the Samuel Oschin Telescope at Palomar Observatory in Southern California. This survey has been operating since the autumn of 2001, with the switch to the QUEST camera happening in the summer of 2003. To date they have found around 40 bright Kuiper belt objects.
To find objects, they take three pictures of a small region of the night sky over three hours and look for something that moves. The many billions of stars and galaxies visible in the sky appear stationary, while satellites, planets, asteroids, and comets appear to move. Objects in the inner Oort cloud are extremely distant and so move extremely slowly.
Sedna is moving quite slowly and is faint, much slower and fainter than the recently discovered 2004 DW, which they also found. Vast areas of the sky have to be searched before something this unusual is found. The search for new objects will continue for the next few years.
Sedna is about 20.5 magnitudes in R (based on observations at a wavelength of 680 nanometers), considerably fainter than 2004 DW and Quaoar. It is beyond the reach of almost all amateurs astronomers (though, interestingly, the first confirmation of the existence of Sedna was made at Tenagra Observatory, an extremely high-end amateur telescope run by Michael Schwartz in southern Arizona).
For orbital elements suitable for your telescope, planetarium, or sky software, please see the Minor Planet Center page for Sedna.
We don’t know. Because its surface is relatively bright, from the thermal observations, we might expect it to have water ice or methane ice like Charon and Pluto have. But observations from the Gemini Telescope and (in collaboration with Chris Koresko at JPL) the Keck telescope suggest that this is not true. From observations at the 1.3-m SMARTS telescope in Chile, we do know that Sedna is one of the reddest objects in the solar system – almost as red as Mars. Why? We’re currently baffled.
Artist Adolf Schaller’s impression of the view from Sedna, with points of interest labelled on the enlarged version
Mike Brown of the discovery team had expected the moon to pop up as a companion “dot” in Hubble’s images, but the object is simply not there. There is a chance it might have been behind Sedna or transiting in front of it, so it could not be seen separately from Sedna in the HST images. But the chance of that is very low.
Brown’s estimate of Sedna’s 40-day rotation period comes from observations of apparent periodic changes in light reflecting from Sedna’s mottled surface. Sedna appears to be the slowest rotating object in the solar system after Mercury and Venus, whose slow rotation rates are due to the tidal influence of the sun. One easy way out of this dilemma is the possibility the rotation period is not as slow as astronomers thought. But even with a careful reanalysis, the team remains convinced the period is correct.
Brown admits, “I’m completely lost for an explanation as to why the object rotates so slowly”.
The discovery team know the orbit fairly well. After finding Sedna in November 2003, they were able to trace it back in archival data to 2001. With this nearly 3-year arc, they know that the perihelion (closest approach distance) is most likely to be within about 7 AU of our 76 AU perihelion estimate. With a perihelion of 76 AU, Sedna has a 60% farther closest approach than any other solar system object. They expect that the orbit will be improved as people search though archival data.
(225088) 2007 OR10 is a very large trans-Neptunian object. It is the largest known body in the Solar System without a name, believed to be about the size of Haumea, and appears to be a dwarf planet. It was discovered by California Institute of Technology astronomers M. E. Schwamb, M. E. Brown, D. L. Rabinowitz at Palomar Observatory on 17th July 2007, though it was not announced until 7th January 2009.
2007 OR10 came to perihelion (its closest to the Sun, 33.62 AU) around 1856. It is currently 86.5 AU from the Sun which makes it the third-farthest known large body in the Solar System, after Eris (97 AU) and Sedna (87 AU). It was farther from the Sun than Sedna in 2013. It will be more remote than both Sedna and Eris by 2045, and will reach aphelion (farthest from the Sun, 100.79 AU) in 2130; its orbit’s semi-major axis is 67.21 AU with an eccentricity of 0.500. It takes 550.98 years to orbit the Sun. The Deep Ecliptic Survey (DES) shows the orbit to be in a 3:10 resonance with Neptune. Its mean anomaly is 101.0°, its inclination is 30.70°, the longitude of ascending node is 336.86° and the argument of perihelion is 207.18°.
The Minor Planet Center lists 2007 OR10 as a scattered-disc object. It was discovered when searching for objects in the region of Sedna. It has been observed 46 times over seven oppositions with a precovery image from 1985.
The size of an object can be calculated from its absolute magnitude (H, 1.9) [its apparent magnitude is 21.3] and the albedo (the amount of light it reflects, 0.185+0.076−0.052). 2007 OR10 has an absolute magnitude of 1.92, which makes it the fifth-brightest TNO known, a little less bright than Sedna (H=1.6; diameter=1,000 km) and brighter than Orcus (H=2.3; diameter≈800 km). Its diameter is 1280±210 km, but certainly more than 552 km. 2007 OR10 is among the reddest objects known. This is probably in part due to methane frosts, which turn red when bombarded by sunlight and cosmic rays.
The spectrum of 2007 OR10 shows signatures for both water ice and methane, which makes it similar in composition to Quaoar. The presence of red methane frost on the surfaces of both 2007 OR10 and Quaoar implies the existence of a tenuous methane atmosphere on both objects, slowly evaporating into space. Although 2007 OR10 comes closer to the Sun than Quaoar, and is thus warm enough that a methane atmosphere should evaporate, its larger mass makes retention of an atmosphere just possible. The presence of water ice on the surface of 2007 OR10 implies a brief period of cryovolcanism in its distant past.
One of the discoverers, Mike Brown, states that 2007 OR10 “must be a dwarf planet even if predominantly rocky”; other astronomers believe it is likely to be one, based on its minimum possible diameter (552 km) and what is understood of the conditions for hydrostatic equilibrium in cold icy and rocky bodies. However, the IAU has not classified it as a dwarf planet. It has not been proven that a TNO of 552 km will necessarily be in equilibrium. It is too distant to resolve its diameter directly; Brown’s estimate of 1,000–1,500 km is based on calculating the albedo that is the best fit in his model, though this agrees with the 1,070–1,490 km determined from observations by the Herschel space observatory. 2007 OR10 has no known satellite, and without a satellite with a well-determined orbit its mass cannot be calculated directly; mass is also a factor in hydrostatic equilibrium.
Here is the technical paper published in The Astrophysical Journal on 10th September 2011 by The American Astronomical Society. It’s title is The Surface Composition of Large Kuiper Belt Object 2007 OR10 by M E Brown, A J Burgasser and W C Fraser.
NASA featured this dwarf planet in their May 2016 newsletter: 2007 OR10: Largest Unnamed World in the Solar System.
A new dwarf planet has been discovered in the inner Oort cloud, about 250 times farther away from the Sun than Earth. The lump of ice and rock circles the Sun at a greater distance than any known object, and never gets closer than 12bn km – 80 times the distance from Earth to the Sun. “This object has the most distant orbit known,” Scott Sheppard of the Carnegie Institution for Science said. “It extends the known boundary of the observable solar system.” It has the largest perihelion known of any object in the Solar System.
The solar system has three distinct regions. Closest to the sun are the rocky planets, such as Venus, Earth and Mars. Farther out are the gas giants, such as Saturn and Jupiter. More distant still, beyond the orbit of Neptune, is a band of icy objects called the Kuiper belt.
In 2003, astronomers found an object beyond the Kuiper belt, which they called Sedna. For more than a decade, the object was a loner, an anomaly in the solar system. But the new body, 2012 VP113, lurks in the same no-man’s land of space, leading astronomers to believe there could be thousands of similar bodies waiting to be discovered there. The object’s orbit brings it as close as 12bn km from the sun, and swings out as far as 67bn km. There are comets that come from even farther out, but they pass much closer to our home planet.
It is about 450 km in diameter and has a highly eccentric orbit, of the same type as Sedna. If its size is confirmed it could qualify as a dwarf planet in the same category as Pluto. Researchers said the discovery proves the existence of the inner Oort cloud, a region of icy bodies that lies far beyond the orbit of Neptune – which at 4.5bn km from the sun is the most remote planet in the solar system. 2012 VP113 (nicknamed “Biden” after another “VP”, US Vice President Joe Biden) orbits roughly 1.29 billion km from the sun, some 83 AU away.
It has a pink tinge that comes from radiation damage that alters the make-up of frozen water, methane and carbon dioxide on the surface.
Based on the swath of sky that needed to be surveyed to turn up the discovery (the width of about 50 full moons), the astronomers estimate that perhaps 900 of these frozen dwarf planet worlds, ones more than 1,000 km wide, may orbit beyond Pluto, alongside thousands more smaller objects. “To all intents and purposes, in the current architecture of the solar system, Sedna and 2012 VP113 should not be there,” says astronomer Megan Schwamb of Taiwan’s Academia Sinica, in a commentary accompanying the study. “This suggests that Sedna and 2012 VP113 are the tip of the iceberg,” she concludes.
Along with eleven other objects orbiting beyond Pluto (including Sedna), the finding suggests that these icy dwarf planets – rounded by gravity but smaller than Mercury – swarm the far reaches of the solar system. They matter, astronomers say, because their orbits preserve the fingerprints of planetary migrations seen after the Sun’s birth in a stellar nursery more than 4.5 billion years ago.
Pluto is often considered the king of the Kuiper Belt, objects seen out to about 50 AUs from the sun. There is an absence of objects beyond that outer edge of this belt, creating a gap stretching from 50 to 75 AUs from the sun, where Sedna and 2012 VP113 are found.
“The discovery does make Sedna look like part of a cluster,” says astronomer Harold Levison of the Southwest Research Institute in Boulder, Colorado, who was not part of the study. “And when you see that number of objects, 12, all similar, it suggests something interesting.”
The latest work has already thrown up an intriguing possibility. The angle of the orbits of 2012 VP113 and Sedna’s are strikingly similar, an effect most likely caused by the gravitational tug of another, unseen body. One possibility is a “Super Earth” that traces so large an orbit around the sun that it has never been seen. “If you took a Super Earth and put it a few hundred astronomical units out, the gravity could shepherd these two objects into the orbits they have,” said Sheppard.
Earlier in March 2014, NASA’s Wide-Field Infrared Survey Explorer (WISE) reported the results from its search for “Planet X”, a hypothesised planet far out in the solar system. It found no evidence for a new planet larger than Saturn within 10,000 AU of the sun. But Saturn is 95 times more massive than Earth, so a smaller Super Earth could go undetected in that region.
This orbital coincidence is what statistically suggests that a bigger planet tugged either long ago or continuously now at these smaller worlds’ orbits to keep them clustered together. If the putative bigger planet is still there and is only a few times bigger than Earth, it would circle the sun about 250 times farther away than our planet does. A bigger one would circle even farther away.
Although 2012 VP113’s discovery looks solid, Levison expressed caution about the notion of the planet theorized by the study authors. “There may be another explanation we just haven’t seen yet,” he says.
Either way, objects such as Sedna and 2012 VP113 are part of the Oort cloud of comets, believed to exist as far as 1,000 AUs from the sun.
Dwarf planets such as 2012 VP113 and Sedna, which travels as far as 949 AUs away from the sun on its 11,400-year orbit, form a placid ‘inner’ Oort Cloud distinct from the outer one, the study suggests. Comets that plunge into the inner solar system are thought to be dispatched from the outer Oort Cloud by gravitational nudges from stars passing near our solar system.
Dwarf worlds like 2012 VP113, which doesn’t orbit as far away from the sun, wouldn’t feel those nudges from passing stars. They instead retain ‘primordial’ orbits unchanged from the early days of the solar system, Schwamb says. In that epoch, the giant planets Jupiter, Saturn, Uranus, and Neptune migrated closer into the solar system, causing a bombardment of the inner solar system by comets.
The same mystery planet, perhaps two to ten times heavier than the Earth, may have stretched out the orbit of Sedna, also orbiting far beyond Pluto.
“A rogue planet could have been ejected from our solar system and perturbed their orbits,” says astronomer Scott Sheppard, who coauthored the discovery report in the journal Nature. “Definitely, it could still be out there.”
Three images of the newly discovered dwarf planet 2012 VP113 taken about two hours apart on 5th November 2012. Photograph: Scott S Sheppard/Carnegie Institution for Science
Astronomers found 2012 VP113 by taking snapshots of the night sky an hour or so apart with an instrument called the Dark Energy Camera on the US National Optical Astronomy Observatory telescope in Chile. When they turned the images into a time-lapse movie of the sky, they could see the new body moving against the background of stationary stars.
The dwarf planet (coloured dots). Three images, each taken about two hours apart, were combined into one. The first was artificially coloured red, the second green and the third blue. The background stars and galaxies did not move and so their red, green and blue images combine to show up as white sources. Photograph: Scott S Sheppard/Carnegie Institution for Science
The orbits of Sedna (orange) and dwarf planet 2012 VP113 (red). Also shown are the orbits of the giant planets (purple). The Kuiper belt is the dotted light blue region. Illustration: Scott S Sheppard/Carnegie Institution for Science
The International Astronomical Union now officially recognizes five worlds as dwarf planets. They are the largest asteroid, Ceres, and four small, distant, icy worlds: Pluto, Eris, Makemake, and Haumea. The last three were discovered in the past decade.
Sedna is not officially a dwarf planet, despite its estimated width of 995 km. It has a long, elongated orbit similar to that of 2012 VP113, but even more stretched out. Both worlds, and the ten smaller trans-Neptunian objects pinpointed in the study that reside farther from the sun than Pluto does, on the outer edge of the Kuiper Belt, follow similar elongated orbits.
Remarkably, they all have orbits whose point of closest approach to the sun, their perihelions, cluster together on the same side of the solar system. For example, 2012 VP113 comes within 80 AUs of the sun at its closest point of approach to our star. Sedna comes within 76 AUs, a perihelion that will occur in 2076 and on the same side of the sun.
The region of space where Sedna and 2012 VP113 were found is called the inner Oort cloud. Astronomers are unsure how this remote cloud of objects formed, but there are three competing theories. One is that a rogue planet was flung out of the early solar system and dragged the Oort cloud material with it. Another is that the material was pulled out of the inner solar system by a passing star. The third option has the same job done by planets orbiting stars born in the same cluster as the sun.
“What is exciting about this work is that we know the inner Oort cloud is there. This is the second object we know of, and it’s a smoking gun,” said Meg Schwamb. By studying the objects, astronomers hope to confirm how the inner Oort cloud formed.
More information from National Geographic, The Guardian and Wikipedia.
(55565) 2002 AW197 is a classical Kuiper belt object (cubewano). Measurements with the Spitzer Space Telescope have confirmed (55565) 2002 AW197 as a probable dwarf planet, although it has not been officially classified as such by the IAU. Light-curve-amplitude analysis shows only small deviations, which suggests that (55565) 2002 AW197 is a spheroid with small albedo spots. Gonzalo Tancredi of the Departamento Astronomía, Facultad de Ciencias, Montevideo, Uruguay and Observatorio Astronómico Los Molinos, Ministerio de Educación y Cultura, Uruguay (2010) accepts it as a dwarf planet; see also his 2009 paper Physical and dynamical characteristics of icy “dwarf planets” (plutoids). Mike Brown’s website – “How many dwarf planets are there in the outer solar system? (updates daily)” – lists it as a highly likely dwarf planet.
These infrared images from NASA’s Spitzer Space Telescope show 24 micron and 70 micron data for Kuiper Belt object (55565) 2002 AW197
[NASA/JPL–Caltech/J.Stansberry (Univ. of Arizona); ssc2004-21a]
(55565) 2002 AW197 was discovered on 10th January 2002, by Michael E. Brown and Chad Trujillo, Eleanor F. Helin, Michael Hicks, Kenneth J. Lawrence and Steven H. Pravdo at the Palomar Observatory. It is located near the Kuiper cliff and is a cubewano. (The 1:2 resonance orbit with Neptune appears to be an edge beyond which few objects are known, and is called the Kuiper cliff.) It has no known moon.
Observations of thermal emissions by the Spitzer Space Telescope in 2007 give a diameter of 734+116-108 km and an albedo of 0.117+.04−.03. The lower size estimate for a dwarf planet is about 400 km. The European Southern Observatory (ESO) analysis of spectra reveals a strong red slope and no presence of water ice (in contrast to Quaoar, also red) suggesting organic material – see comparison of colours and typical composition inferred from spectra of the trans-Neptunian objects (TNOs) in the technical literature cited above.
It is currently 46.2 AU from the Sun. It will come to perihelion around 2079. Its aphelion is 53.503 AU (8.0040 Tm), perihelion 41.066 AU (6.1433 Tm), semi-major axis 47.284 AU (7.0736 Tm), eccentricity 0.132, orbital period 325.15 years (118,761 days), average orbital speed 4.31 km/s, mean anomaly 281.945°, inclination 24.410°, longitude of ascending node 297.513° and argument of perihelion 295.307°.
Its dimensions are 734+116-108 km or 700±50 km, its sidereal rotation period is 8.86 hours, and its albedo is 0.117+.04-.03 or 0.17±0.03. (These different figures reflect how the data is interpreted.) Its temperature is about 39 to 40 K, its spectral type (moderately red) is B-V=0.91, V-R=0.56, its apparent magnitude at opposition is 20.0, and its absolute magnitude (H) is 3.26.
See also Wikipedia, Beginner Astronomy, Science Direct, Smithsonian/NASA Astrophysics Data System, Planetpedia.
As well as the dwarf planets listed here and elsewhere in this web-site, there are likely to be 100 or more falling into that category. These are the likeliest of the others (listed in Wikipedia):
