Eris’ moon has also been given a name – Dysnomia. In mythology, Dysnomia was the daughter of Eris and was known as the spirit of lawlessness. I love the appropriateness of both names.

Our dwarf planet (the largest discovered so far) now has a name! It has been named Eris. The name, Eris, comes from the Greek goddess of chaos and strife, which is an appropriate name, since our dwarf planet caused so much havoc in the astronomical community. In mythology, Eris caused a quarrel among goddesses that sparked the Trojan War. In real life, the discovery of Eris caused astronomers to demote Pluto to a dwarf planet and change the entire definition of what a planet is.

Our nickname, Xena, is now history, and Eris is the formal name.

According to Space Daily, the IAU definitions of objects in our solar system can be best described this way:

The International Astronomical Union has decided that, to be called a planet, an object must have three traits. It must orbit the sun, be massive enough that its own gravity pulls it into a nearly round shape, and be dominant enough to clear away objects in its neighborhood.

To be admitted to the dwarf planet category, an object must have only two of those traits — it must orbit the sun and have a nearly round shape. And no, moons don’t count as dwarf planets. In addition to Pluto, Ceres and 2003 UB313, the astronomical union has a dozen potential “dwarf planets” on its watchlist.

What’s to become of the other objects in our solar system neighborhood, the ones that are not planets, not dwarf planets and not moons? The organization has decided that most asteroids, comets and other small objects will be called “small solar-system bodies.”

So, although Xena is not a planet, it is a dwarf planet. Maybe they should officially name it with one of the Seven Dwarfs names. Of those names (Bashful, Doc, Dopey, Grumpy, Happy, Sleepy and Sneezy), I’d choose Bashful, since it is hiding so far away.

The IAU decided today that our beloved tenth planet will not be defined as a planet. In fact, Pluto has been stripped of its planetary title as well. It’s a sad day here.

The IAU is proposing the following definition of a planet, which would make our beloved tenth planet, really the 12th planet!

A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet.

Under this definition, Pluto would remain the 9th planet, but its moon, Charon, would be reclassified as the 10th planet. In addition, Ceres, an asteroid would also be reclassified as a planet, making it the 11th planet. Finally, to confuse matters further, all of these would also be called plutons to distinquish them from the eight “classic” planets.

If this definition is accepted, and it may not be, we could end up with 53 planets immediately, and possibly hundreds as more are discovered in the outer reaches of the solar system.

IAU members will vote on this definition on August 24th, 2006. Confusing times for our 2003 UB313 planet. Is it a planet? Is it the tenth planet? Is it the twelfth planet? Is it also a pluton? And what name will it be given? We won’t have to wait long for the answers.

The IAU (International Astronomical Union) will propose a definiton of a planet on August 18, 2006, and a vote on that proposed definiton will take place on August 24, 2006. Such a definition holds the fate of the tenth planet, as well as possibly the fate of Pluto. Are either of them a planet? One, but not the other? We will know soon. If the new definition of a planet matches with that of 2003 UB313 (what we call the tenth planet), then we can finally get to the point of having a name assigned to it.

For the first time, NASA’s Hubble Space Telescope has seen distinctly the “tenth planet,” currently nicknamed “Xena,” and found that it’s only slightly larger than Pluto.

Though previous ground-based observations suggested that Xena’s diameter was about 30 percent greater than Pluto, Hubble observations taken Dec. 9 and 10, 2005, showed Xena’s diameter as 1,490 miles (with an uncertainty of 60 miles).

Pluto’s diameter, as measured by Hubble, is 1,422 miles.

credit: NASA

A group of amateur astronomers has used the 2.1-meter (82-inch) Otto Struve Telescope at McDonald Observatory to make the first ‘through-the-eyepiece’ sighting of so-called the tenth planet, an object orbiting the Sun in the Kuiper Belt, far beyond Pluto. The group includes members of the St. Louis and Rockland Astronomical Societies, and a few others.

The object’s official designation is 2003UB313. Its discoverers, led by Dr. Michael Brown of Caltech, have nicknamed it ‘Xena.’ The actual discovery and confirmation of the object were made by mining images taken by sensitive electronic imagers mounted on a telescope, called CCDs (charge-coupled devices).

According to Louis Berman of the St. Louis Astronomical Society, Brown confirmed to the group of amateur astronomers before their attempt that, to his knowledge, they were the only people in the world attempting to see ‘Xena’ through the eyepiece of a telescope.

In terms of brightness, ‘Xena’ is what astronomers would call a 19th magnitude object. That means that it’s about five million times dimmer than Polaris, the North Star, which is sometimes difficult to see with the unaided eye. ‘Xena’ is just at the limit of what can be seen with the human eye through the Struve Telescope.

The sighting took place on October 9, 2005, at 1:08 a.m. CDT. The first sighting was made by Keith Murdock of the St. Louis Astronomical Society. Confirmation occurred at 1:15 a.m. when Louis Berman, also of the St. Louis group, located the object. Eight more members of the group saw ‘Xena,’ in addition to two McDonald Observatory staffers, Kevin Mace and Frank Cianciolo. The observers followed a strict protocol and kept detailed records to verify their observations.

McDonald Observatory’s Frank Cianciolo recalls the event:

‘Since UB313 would not be high enough to observe until roughly 1:30 a.m. or so, the group planned to observe a number of other object prior to the ‘Xena’ attempt. The views of these other objects indicated that while we had reasonable conditions, we didn’t have the excellent conditions the group had thought we may need to acquire UB313, so there was a bit of tension as the viewing window approached.

‘At the proper time, the guys from St. Louis worked with Kevin [Mace] to get the telescope pointed to the coordinates where they had calculated UB313 should be at that precise time. Fortunately, there were no bright stars in the field of view that would cause glare and possibly ruin any chance of seeing the object. Due to some confusion about sky orientation in the eyepiece, Keith [Murdock] spent several long minutes not recognizing the field he expected to see. Once that confusion was cleared up and a small correction to the telescope’s point were made, however, it didn’t take long for Keith to announce that he believed he could identify, conclusively, UB313.

‘After Keith’s sighting, it took each observer several minutes to properly understand the orientation of the field and then to hop from brighter stars to fainter stars and finally to see ‘Xena.’ At the staggering distance of roughly 90 AU [that is, 90 times the Earth-Sun distance], an object the size of UB313 essentially displays no measurable size. Due to this, it was no easy task to actually identify the incredibly faint fuzzy dot as anything but a star at the very limit of visibility through the 82-inch [Struve Telescope].’

The object, Berman says, ‘was a very dim, pointlike source that could only be seen through averted vision. If you looked straight at it, you’d never see it.’

McDonald Observatory’s Mace agrees. ‘It looked like a faint star,’ he said. ‘A little difficult to pick out against the field stars. It’s not visually stunning.’

However, Mace continued, ‘how many people on the planet have seen this? Pretty much just our group.’

Cianciolo credits the sighting with the group’s early preparations. ‘Had it not been for the excellent charts and CCD images which the St. Louis group spent weeks preparing, there would have been no way to conclusively identify UB313,’ Cianciolo said. ‘It is a testament to the incredible skill and dedication some amateurs show to their passion of astronomy that the folks on the dome floor that night are, to anyone’s knowledge, the only humans on the planet to have seen UB313 at an eyepiece.

‘Truly this has to go down as ‘extreme astronomy,” he said.

These days, it is unusual for large telescopes at professional observatories to even have eyepieces. The astronomers at McDonald don’t use the eyepieces for their observations ‘ images are recorded onto computers. But the eyepiece capability makes three of McDonald’s research-grade telescopes accessible to the public a few nights each month. The Struve, as well as the 2.7-meter (107-inch)Harlan J. Smith Telescope, may be the largest telescopes in the world available for public observing sessions. McDonald’s smaller 0.9-meter (36-inch) telescope is also used for special public viewing programs.

*press release courtesy of McDonald Observatory

Although the IAU determined in late 2005 that an object can be considered a planet if it is at least the size of Pluto, it decided to ask the Division of Planetary Sciences (DPS) of the American Astronomical Society for its recommendation as well. The IAU will be meeting in Prague in August, 2006, where a final decision should be made. Hopefully, at that time, we will have official confirmation that the tenth planet really is the tenth planet!

The University of Bonn, using a 30-meter IRAM telescope, have determined that 2003 UB313 has a diameter of 3000 +/- 400 km. Like Spitzer, IRAM measures the heat given off from the object, but IRAM is a much larger telescope than Spitzer. Due to its size, it was able to measure the heat output in a region of the spectrum where much less heat is given off. This new measurement is right in line with the Spitzer measurement, making the tenth planet approximately 125% of the size of Pluto.