Any mention of Pluto among astronomy buffs, around water coolers and in comments sections, is enough to spark controversy. When the diminutive world officially became known as a dwarf planet in 2006, many took the “demotion” personally. But an announcement today from the SETI Institute might just be cool enough to bring everyone together.
The discoverers of Pluto’s two smallest moons are reaching out to the world for help in naming them. Currently designated P4 and P5, these tiny satellites were discovered in 2011 and 2012, respectively, using Hubble Space Telescope data. These were always temporary labels, though, and the time has come to select their official names. There might be even more moons lurking around the former planet, but the thing about Pluto is it’s really, really far, and even for Hubble the entire system registers as little more than dots. Plus, these moons are really small, only about 20 miles across max, making others like them extra hard to spot.
Pluto’s dinky diameter wasn’t the official reason it was demoted from the planetary club back in 2006, but symbolically, size was the last straw. When Caltech astronomer Mike Brown spotted the object we now call Eris back in 2005 and astronomers figured it to be larger than Pluto, the former ninth planet’s fate was sealed. Now Pluto’s reclassification as a “dwarf planet” and the subsequent public outcry is behind us, but new research suggests that the former planet’s symbolic death knell—Eris’ size advantage—was wrong.
The argument has been rekindled by astronomers who just completed detailed viewings of Eris from observatories high in the Chilean Andes. According to Bruno Sicardy of the Paris Observatory, Eris must be no wider than 1,454 miles, while the accepted value for Pluto’s diameter is 1,456.5 miles. And because of the uncertainty of measuring diameter of such a distant object, Kelly Beatty at Sky & Telescope says, Eris’ official size could decease another 30 miles or more after astronomers analyze more of this data.
Images taken in December 2005 by Brown and others with the Hubble Space Telescope indicated a diameter of 1,500 miles (2,400 km), just 5% larger than Pluto’s. But the true size remained uncertain because even Hubble’s supersharp gaze is only barely able to resolve Eris’s disk. (Remember: it’s some 9 billion miles from the Sun, twice as far away as Pluto.) [Sky & Telescope]
This month, however, the window of opportunity opened for astronomers. Eris passed directly in front of a star, which allowed them to more accurately gauge its size.
A cold and sterile chunk of rock orbiting the sun in the vicinity of Neptune and Pluto has been officially named Makemake, after a Polynesian god. The International Astronomical Union (IAU) has also designated Makemake the solar system‘s fourth dwarf planet and third “plutoid,” as researchers’ new aptitude for locating small orbital bodies has required a new and controversial system of classification.
Astronomers discovered Makemake (pronounced MAH-keh MAH-keh)… in 2005 and believe its surface is covered by a layer of frozen methane. It is bright enough to be seen by a high-end amateur telescope [SPACE.com]. Researchers say it’s about two-thirds the size of Pluto.
It’s been nearly two years since the International Astronomical Union (IAU) voted to remove poor Pluto from the list of our solar system’s true planets, putting the lie to what generations of kids learned in science class. Pluto was demoted to a “dwarf planet,” making it just one of many cold chunks of rock scattered at the fringe of the solar system.
Maybe the astronomers felt a little guilty about about kicking Pluto out of the planetary club, so they’ve come up with a gesture to make amends. From now on Pluto won’t just be any dwarf planet, it will be a ‘plutoid’ [New Scientist]. The category name will apply to all dwarf planets beyond the orbit of Neptune, which sounds like quite an honor until you realize that there’s only one other such object, a dwarf planet named Eris that was discovered in 2005.