First off, astronomers have found the first of Sedna’s buddies — another dwarf planet out in the extreme edges of the solar system, 2012 VP113. The team is provisionally calling it “Biden” after our own Vice President, but it will surely get a different name when the time comes. (Remember, Eris was once called Xena!) It’s 280 miles across and orbits 7 1/2 billion miles away — or about 80.6 astronomical units*. It’s smaller and paler than Sedna, but provides more evidence that the Oort Cloud exists, as these bodies orbit where the inner Oort cloud is proposed to exist. There could be many, many more objects out there, just waiting for luck and improved instruments to detect them.
Second, 10199 Chariklo turns out to have a rather surprising feature for a small world. At 160 miles in (estimated) diameter, it is the largest of the Centaurs, a class of icy small bodies that orbit among the gas giants. This one ranges between Saturn and Uranus, coming closest to Uranus, and is thus very cold. But astronomers studying it discovered it has one feature that makes it more like Saturn — it has a ring system. So does Uranus, but Uranus’ rings are dark and dusty. Chariklo’s rings appear to be made of larger particles densely packed, probably icy. They were discovered completely by chance by astronomers probing the tiny world by observing a stellar occultation — when the object passes in front of a star, eclipsing it. They noticed the star eclipsed several times, and from their data were able to deduce there are two complete rings around the planet, fairly large and dense. Little more is known of this tiny world; it might qualify as a dwarf planet, if it turns out to have pulled itself into enough of a sphere.
It just goes to show: as much as we learn about minor planets, there’s always so much more out there. 😉
* 1 astronomical unit is the average distance from the Sun to the Earth