Get the scoop at Astronomers at Palomar Observatory Discover a 10th Planet Beyond Pluto; more at Gemini Observatory Shows That "10th Planet" Has a Pluto-Like Surface; and graze on over to the NEO Program's 2003 UB313 site for the orbital animation.
How do we know it's bigger than Pluto? As Dave Jewitt explains:
Measurement of the size of a KBO is difficult. The apparent optical brightness, corrected to a standard distance from the sun and Earth, is called the "absolute magnitude", H. Absolute magnitude provides a measure of the product of the albedo of the KBO with the square of its diameter.
Looking at the handy table he provides, we find Pluto at H = -1 and p = 0.6 having a diameter of 2,320 km. So if 2003 UB313 has H = 0.4, at a given distance it would be 3.6 times as faint as Pluto if it had the same diameter and albedo. What this means, in turn, is that if its albedo is only 1/3.6 of Pluto's (very bright) albedo of 0.6, or around 0.17, it would be at least as large as Pluto. An albedo of 0.17 is greater than that of any other large KBO, with the possible exception of Sedna, so it is likely that 2003 UB313 is at least (say) 2,500 kilometers across, or about 70% the size of Earth's Moon.
(The Royal Astronomical Society of New Zealand has a useful comparison of various trans-Neptunian objects.)
So if it's bigger than Pluto, why not call it a planet? Here's why not:
UPDATE: Previously unknown, or at least unacknowledged, reader Kenneth Chang directs my attention to MPEC 2005-O41, which clearly states that H = -1.1 for 2003 UB313; even if it were reflecting 100% of the sunlight hitting it, it would still have to be larger than Pluto.
I don't expect to be able to attend this event, but thanks to David Neuenschwander of the ASKC, I've been made aware of it and thought I'd pass it along for my relatively local readers:
Dr. Kevin Evans, Southwest Missouri State University geologist, will be in St. Clair County on Saturday, July 30 to lead a field trip for anyone interested in the Weaubleau-Osceola Meteor Impact Site.
The Weaubleau-Osceola structure is thought to be a meteorite impact site in western Missouri near the towns of Osceola and Weaubleau.
... [it] is one of a series of known or suspected impact sites along the 38th parallel in the states of Illinois, Missouri, and Kansas. These 38th parallel structures are thought to possibly be the result of a serial impact, similar to that of comet Shoemaker-Levy 9 on Jupiter, an extremely unlikely event on Earth. The argument for a serial strike would be greatly strengthened if the ages of the other 38th parallel structures could be constrained to the same period as the Weaubleau-Osceola structure.
The Weaubleau-Osceola structure is one of the fifty largest known impact craters on Earth and the fourth largest in the United States.
The upcoming field trip was initiated by the Crater Critter Community Council, an informal collection of people with a common interest in knowing and caring for the local area.
Anyone wishing to participate in the July 30 field trip is asked to meet at 8:30 a.m. in Collins at Peggy's Restaurant. The field trip will last approximately four hours. Everyone needs to bring their own drinking water, wear shoes suitable for hiking and climbing, and wear clothing appropriate for the weather. Car-pooling is recommended.
Collins is less than 2 hours southeast of Kansas City, MO, via US highway 71 and Missouri highways 7 and 13.
Just in time for another anniversary, Randy McDonald sends word of the latest installment in his series on space colonization, which he characterizes as "pessimistic," though it sounds merely measured to me; he concludes: "What reason could possibly justify the expense of venturing off-Earth to found offshoot societies, absent direct threat or a compelling need? Ideology of some sort would seem to be required, that or obvious and immediate economic benefit."
RTWT; I can only add that another reason does occur to me, which might be called "anti-ideology," or the desire to manage the risks created by ideological conflict on Earth. Most such conflicts at present seem to revolve around particular locales -- while south and southwest Asia get a lot of attention, there are others -- and we should remember that plenty of immigrants to North America in times past were escaping wars in Europe.
In this connection, back in November 2003, I speculated:
Obviously, the Type 0.5 civilization could essentially ignore Earth's economic struggles and sectarian conflicts, thinking no more of them than we think of a clash between Stone Age tribes over a few square miles of the Amazon Basin. We may therefore expect those with vested interests in regulating human activities or propagating territorial conflicts on Earth's surface to violently resist the creation of a Type 0.5 civilization.
To see what I mean by "Type 0.5," you'll have to wade through that entire post.
(Randy also issued a standing invitation for me to visit if I'm ever in Toronto; Randy, same to you if you're ever in KC!)
The proprietor of Post-atomic, whose (presumably) real name appears in his e-mail but who goes by "Mutant," writes: "I read this and thought of your weblog right away." I can't help but be flattered. Language warning re: final line. But it's so true.
Previously unknown reader (the best kind) Terry Stickel, who works at W.M. Keck Observatory (making him, if possible, even cooler than my other previously unknown readers), sent this offer, which as he notes poses some logistical difficulties:
... I tried to forward you an email I got from my facility manager here at Keck. It said that the old aluminum done for the UH 24" telescope on Mauna Kea is up for grabs. It's an aluminum dome about 20' in diameter. I thought of you & [Arcturus] because I know you're involved with some serious amateur stuff in KS [and MO, actually -- JDM]. Then I thought better of it. Hauling it down from where it's at now (9,500' up Mauna Kea) to Hilo or Kawaihae and then shipping it across the Pacific, and then from Long Beach to Kansas would have to cost more than the dome is worth. Ah, well, someone will probably haul it to down to Puna and use it for a chicken coop.
crazydedicated amateurs are advised that a 20' dome awaits you if you can figure out how to transport it a quarter of the way around the planet.
Lots of maintenance still to do, but welcome Bill Tammeus, previously mentioned here, though more substantively in Excellent Analysis in KCStar and US as Incubator of Islamic Reformation (and, yes, critically in one of the earliest posts on this blog, Slamming Bill Tammeus).
(Yeah, I know I said I wouldn't post any more until I got back.)
-- go outside, right now, now being a bit before 10 PM Central Daylight Time, and look west. An absolutely gorgeous, delicate fingernail of crescent Moon, thirty-eight hours old, is setting in the west.
Blogging will be light -- nonexistent, actually -- while I spend a week in the Boundary Waters Canoe Area Wilderness, so I'll leave you with this. Previously unknown reader (the best kind) Rich Tyler asks: "Do you know of any companies that are trying to currently detect and/or destroy potential asteroids on a collision course with Earth?"
Lots of detection efforts are underway (Powell Observatory was the #2 site in the world for this at one time), though I know of none by for-profit organizations. There's tons of great stuff at Lists and Plots: Minor Planets, perhaps most notably this list of PHAs.
I have speculated on more comprehensive methods at A Modest Proposal for an Asteroid Warning System and Asteroid Detection, Again. My speculations were aimed at managing the geopolitical risk of misinterpretation of a kiloton-to-megaton-range impact as a nuclear explosion, especially in the Indian subcontinent (see also Asteroids - Running the Numbers Again).
Destroying potential impactors would rarely be necessary -- a much smaller amount of energy could be used to alter their orbit slightly and cause them to miss Earth entirely. If it were too late to do this, attempting to destroy them could result in several slightly smaller impacts rather than one big one. Only objects in a narrow range of size and trajectory would be amenable to outright destruction, presumably by thermonuclear warhead, and even then the damage of impact would have to be weighed against damage from EMP; this source notes that "a single high-altitude burst 200 miles above Kansas could propagate an EMP enveloping the entire United States."
How a for-profit organization could carry out impactor-detection or -mitigation efforts is not immediately obvious, though as a veteran of commercial space efforts myself I am intrigued by the notion.
(See also Stealth Killer Comets for some more math on this.)
The comet is a 10th-magnitude object, making it that much more difficult to observe during the impact itself from anyplace as far east as KC. For my more distant (and westerly) readers, courtesy of the ASKC's James Pageau, this *.gif showing its position relative to Jupiter and Spica.
Details gleaned from various postings on the ASKC e-group. Acknowledgements to Scott Kranz and Dave Dembinski, in particular.
From Powell Observatory, this coming Sunday night at 10 PM CDT (civil twilight ends at 9:18 PM CDT at Louisburg, per the US Naval Observatory, the comet will be 35° above the southwestern horizon (azimuth 214°).
The "light arrival time" of the impact event will be 12:52 AM CDT Mon 4 Jul, at which time the comet will be only 8° above the horizon in the west-southwest (azimuth 250°). I am not optimistic about being able to view it from this far east.
Furthermore, any brightening of the comet is likely to occur not as an immediate result of the impact but over a period of hours, even days, as material ejected during the event expands into space and becomes part of the coma. Therefore, the way to observe the "event" will be to look at the comet before impact, on Sunday evening when it's still well above the horizon, and compare that view to how it looks 24 hours later.
In spite of all of the above, I intend to turn up at Powell late Sunday night (11:30 PM) to help with crowd control -- and show off my new laser pointer. ;^)