As the pace of discoveries outside our solar system increases, weird worlds are starting to crop up. At a recent meeting of astrophysicists in Aspen, Colorado, researchers described some strange new orbs:
Pint-size planetoid: The smallest extrasolar object yet found, only one-fifth the mass of Pluto, has been spied in an oddball solar system 1,500 light-years from Earth. Unlike other known extrasolar planets—gassy giants at least as big as Neptune and usually Jupiter’s size or larger—this tiny orbiter and its three companion worlds (which were discovered in 1992) are undoubtedly rocky, like Earth, and form a scaled-down version of our own solar system. The objects are not, however, Earth-like: They circle a pulsar, the rapidly spinning core of an exploded star, and are bathed in a scorching bath of radiation that renders life impossible.
Dazzling diamonds: These have not yet been discovered, but astrophysicist Marc Kuchner theorizes that some planets might be built from carbon-rich minerals like graphite and diamond and not from the silicate minerals used to construct Earth. If they exist, the objects would have some unusual properties: little or no water, because free oxygen would combine with carbon to make carbon monoxide, and perhaps surfaces covered in gooey tar or layers of superhard carbide compounds. Under intense pressure and heat, pure carbon would form thick diamond layers only a few miles under the planet’s surface, layers that could become exposed through erosion.
Brown-dwarf buddies: Astronomers still can’t agree on what to call brown dwarfs: Are they failed stars, without enough mass to kick-start the nuclear reactions of typical stars, or are they supersize planets? Astrophysicists speculate that even the smallest of the dwarfs might have planets. Using the Spitzer Space Telescope, researchers have located a protoplanetary disk, the ring of gas and dust from which planets are built, in orbit around a small brown dwarf, 15 times as massive as Jupiter. In that disk, astrophysicists say, a collection of small worlds will probably begin to form soon. Even smaller bodies might also form disks and then planets—planets around planets.