There is a Possible Super Earth in the Outer Solar System

Out there, way beyond the Sun's family, astronomers have discovered thousands of planets orbiting other stars. Among these alien planets, we have discovered a significant number of "Super Earths" -- planets more massive than our Earth but less massive than the smallest giants in our solar system, Uranus and Neptune. Our solar system has no such Super Earths, but many other systems do; they may be quite common.

Now, Michael Brown and Konstantin Batygin at Caltech, propose that we might just have a Super Earth in our solar system, but so far from the Sun, it takes between 10,000 and 20,000 years to make one orbit! (Pluto, for comparison, takes about 250 years.)

Brown and Batygin have been examining the orbits of icy chunks way beyond Pluto, in the region we call the Kuiper Belt. There are several chunks out there, including one Brown discovered in 2003, called Sedna, that move in an oddly aligned way. After testing many computer models to explain their odd orbit, their best model indicates there could be a planet 10 times the mass of our own Earth, whose stronger gravity is affecting the motions of many objects out where it orbits. Just a few of the affected chunks have been discovered so far and the planet itself has NOT be seen.

So this is a somewhat daring hypothesis, which the two astronomers explain in this brief video: https://www.youtube.com/watch?v=6poHQ2h00ZA

Please note that our image is a painting that Caltech commissioned. No one knows what this Planet Nine looks like.

Now here is the human side of the story. Michael Brown led the team that discovered Eris, the dwarf planet that is the same size as Pluto, in 2005. When he discovered it, he told his wife that he had just discovered a tenth planet and she had made a good decision in marrying him. Alas, instead of being acknowledged as the 10th planet, Eris caused astronomers to rethink the status of Pluto, and remove it from being the 9th planet. Brown was gracious about it, but you can imagine how disappointing it all was for him.

So now Brown may have "discovered" (or at least predicted) a real new planet. He is already nicknaming it "Planet Nine" and it's so big, no one will be able to call it a dwarf! If it is confirmed one day, he can go back to his wife and tell her, "Well, maybe I only discovered a dwarf planet before, but now I have discovered a real planet at last." Not a bad thing to discuss over dinner!

You can see a video where Brown discusses his role in the Pluto and Eris story at: https://www.youtube.com/watch?v=7pbj_llmiMg

Brown and Batygin

Two Major Discoveries about Our Solar System

Two major finds were announced yesterday: the first rings found around an asteroid, and the most distant object -- a dwarf planet -- ever seen in our solar system. Let me fill you in on the details.

The unexpected rings were found around the asteroid Chariklo, a 150-mile wide chunk that orbits between Saturn and Uranus. A group of South American astronomers observed Chariklo moving in front of a star, and glimpsed two thin rings around it. The rings are roughly 4 and 2 miles wide and are separated by a gap of some 5 1/2 miles. In the past, when we have found distinct thin rings like this, they have been kept thin by the presence of small "shepherding moons." The analogy is the shepherds keep a flock of sheep in a thin line, and these moons keep the particles of the rings from drifting away from their formation. So we expect that one or more such moons will eventually be found around Chariklo.

How did an asteroid get itself a set of rings -- which we have previously seen only around giant planets? Our best guess is that Chariklo was involved in some sort of cosmic accident and the rings are left-over debris from that event.

By the way, Harry Potter fans and mythology buffs will appreciate the name of the asteroid. In classical mythology, Chariklo was the wife of Chiron, the best known of the Centaurs -- creatures that were half human and half horse. In the same way, the Centaurs in our solar system are also half-breeds -- they have some characteristics of asteroids and some of comets.

The second discovery was of a dwarf planet orbiting so far away from the Earth and the Sun that it is the most distant world we have seen in our solar system. The small, frozen world, estimated to be about 250 miles wide, is called 2012 VP113, a boring provisional name that includes the date of its first sighting and letters and numbers that give a code for what its order is in the discovery of small objects that year. But because the letter code happens to be VP, the discoverers have nicknamed it Biden (but that will not be its final official name.)

I can't resist noting, in case you were not aware of this, that each vice president of the U.S. already has a direct connection to the world of astronomy, since the vice-president's residence is on the grounds of the U.S. Naval Observatory. Many vice-presidents brings guests to the observatory and even have parties there.

Little "Biden" (the world) is really, really out there, beyond what we think are the borders of the Kuiper Belt -- the zone of Pluto, other dwarf planets, and small icy chunks that make a belt outside the orbit of Neptune. The conventional wisdom has been that this belt should end at 50 times the distance between the Earth and the Sun (which we call 50 astronomical units), or about 4 1/2 billion miles from the Sun.

Biden, on the other hand, makes a looping orbit further out, and never gets closer to the Sun than 80 astronomical units or 7 1/2 billion miles. And most of the time is is even further out. (Another object found earlier, now called Sedna, is also out there.) The presence of such "far-out" members of our solar system, while not impossible, is surprising enough that astronomers are now set to pondering what got them out there.

Our image shows an artist's conception (no one has a photo of it) of what Chariklo and its two rings might look like out there, provided by the European Southern Observatory.