* Astronomy

Ephemeris:  	

2003 UB313               a,e,i = 67.71, 0.44, 44                 q = 37.808
 Date       UT      R.A. (J2000) Decl.    Delta     r     El.    Ph.   V      Sky Motion
            h m s                                                            "/min    P.A.
2006 08 25 000000 01 39 32.1 -05 08 56  96.219  96.858  129.0   0.5  18.7    0.016   235.4
2006 08 26 000000 01 39 30.9 -05 09 09  96.207  96.858  129.9   0.5  18.7    0.016   235.9
2006 08 27 000000 01 39 29.6 -05 09 22  96.194  96.858  130.8   0.5  18.7    0.016   236.4
2006 08 28 000000 01 39 28.3 -05 09 35  96.182  96.857  131.7   0.4  18.7    0.017   236.9
2006 08 29 000000 01 39 26.9 -05 09 48  96.171  96.857  132.6   0.4  18.7    0.017   237.4
2006 08 30 000000 01 39 25.5 -05 10 01  96.159  96.857  133.5   0.4  18.7    0.017   237.8
2006 08 31 000000 01 39 24.1 -05 10 14  96.147  96.857  134.4   0.4  18.7    0.017   238.2
2006 09 01 000000 01 39 22.7 -05 10 28  96.136  96.857  135.4   0.4  18.7    0.018   238.7
2006 09 02 000000 01 39 21.2 -05 10 41  96.125  96.857  136.3   0.4  18.7    0.018   239.1
2006 09 03 000000 01 39 19.7 -05 10 54  96.114  96.857  137.2   0.4  18.7    0.018   239.5
2006 09 04 000000 01 39 18.2 -05 11 08  96.104  96.856  138.1   0.4  18.7    0.019   239.8
2006 09 05 000000 01 39 16.6 -05 11 21  96.093  96.856  139.0   0.4  18.7    0.019   240.2
2006 09 06 000000 01 39 15.0 -05 11 34  96.083  96.856  139.9   0.4  18.7    0.019   240.6
2006 09 07 000000 01 39 13.4 -05 11 48  96.073  96.856  140.8   0.4  18.7    0.019   240.9
2006 09 08 000000 01 39 11.8 -05 12 01  96.063  96.856  141.7   0.4  18.7    0.020   241.3
2006 09 09 000000 01 39 10.1 -05 12 15  96.054  96.856  142.6   0.4  18.7    0.020   241.6
2006 09 10 000000 01 39 08.4 -05 12 28  96.045  96.856  143.5   0.4  18.7    0.020   241.9
2006 09 11 000000 01 39 06.7 -05 12 42  96.036  96.856  144.4   0.3  18.7    0.020   242.3
2006 09 12 000000 01 39 05.0 -05 12 56  96.027  96.855  145.2   0.3  18.7    0.020   242.6
2006 09 13 000000 01 39 03.2 -05 13 09  96.018  96.855  146.1   0.3  18.7    0.021   242.9
2006 09 14 000000 01 39 01.4 -05 13 23  96.010  96.855  147.0   0.3  18.7    0.021   243.2 

The International Astronomical Union (IAU) today downgraded the status of Pluto to that of a "dwarf planet," a designation that will also be applied to the spherical body discovered last year by California Institute of Technology planetary scientist Mike Brown and his colleagues. The decision means that only the rocky worlds of the inner solar system and the gas giants of the outer system will hereafter be designated as planets.

The ruling effectively settles a year-long controversy about whether the spherical body announced last year and informally named "Xena" would rise to planetary status. Somewhat larger than Pluto, the body has been informally known as Xena since the formal announcement of its discovery on July 29, 2005, by Brown and his co-discoverers, Chad Trujillo of the Gemini Observatory and David Rabinowitz of Yale University. Xena will now be known as the largest dwarf planet.

"I'm of course disappointed that Xena will not be the tenth planet, but I definitely support the IAU in this difficult and courageous decision. It is scientifically the right thing to do, and is a great step forward in astronomy. Pluto would never be considered a planet if it were discovered today, and I think the fact that we've now found one Kuiper-belt object bigger than Pluto underscores its shaky status" - Mike Brown.

Pluto was discovered in 1930. Because of its size and distance from Earth, astronomers had no idea of its composition or other characteristics at the time. But having no reason to think that many other similar bodies would eventually be found in the outer reaches of the solar system--or that a new type of body even existed in the region--they assumed that designating the new discover as the ninth planet was a scientifically accurate decision.
However, about two decades later, the famed astronomer Gerard Kuiper postulated that a region in the outer solar system could house a gigantic number of comet-like objects too faint to be seen with the telescopes of the day. The Kuiper belt, as it came to be called, was demonstrated to exist in the 1990s, and astronomers have been finding objects of varying size in the region ever since.
Few if any astronomers had previously called for the Kuiper-belt objects to be called planets, because most were significantly smaller than Pluto. But the announcement of Xena's discovery raised a new need for a more precise definition of which objects are planets and which are not.
According to Brown, the decision will pose a difficulty for a public that has been accustomed to thinking for the last 75 years that the solar system has nine planets.

"It's going to be a difficult thing to accept at first, but we will accept it eventually, and that's the right scientific and cultural thing to do" - Mike Brown .

In fact, the public has had some experience with the demotion of a planet in the past, although not in living memory. Astronomers discovered the asteroid Ceres on January 1, 1801--literally at the turn of the 19th century. Having no reason to suspect that a new class of celestial object had been found, scientists designated it the eighth planet (Uranus having been discovered some 20 years earlier).
Soon several other asteroids were discovered, and these, too, were summarily designated as newly found planets. But when astronomers continued finding numerous other asteroids in the region (there are thought to be hundreds of thousands), the astronomical community in the early 1850s demoted Ceres and the others and coined the new term "asteroid."

Xena was discovered on January 8, 2005, at Palomar Observatory with the NASA-funded 48-inch Samuel Oschin Telescope. Xena is about 2,400 kilometres in diameter. A Kuiper-belt object like Pluto, but slightly less reddish-yellow, Xena is currently visible in the constellation Cetus to anyone with a top-quality amateur telescope.
Brown and his colleagues in late September announced that Xena has at least one moon. This body has been nicknamed Gabrielle, after Xena's sidekick on the television series.
Xena is currently about 97 astronomical units from the sun (an astronomical unit is the distance between the sun and Earth), which means that it is some nine billion miles away at present. Xena is on a highly elliptical 560-year orbit, sweeping in as close to the sun as 38 astronomical units. Currently, however, it is nearly as far away as it ever gets.

Pluto's own elliptical orbit takes it as far away as 50 astronomical units from the sun during its 250-year revolution. This means that Xena is sometimes much closer to Earth than Pluto--although never closer than Neptune.
Gabrielle is about 250 kilometres in diameter and reflects only about 1 percent of the sunlight that its parent reflects. Because of its small size, Gabrielle could be oddly shaped.
Brown says that the study of Gabrielle's orbit around Xena hasn't yet been fully completed. But once it is, the researchers will be able to derive the mass of Xena itself from Gabrielle's orbit. This information will lead to new insights on Xena's composition.
Based on spectral data, the researchers think Xena is covered with a layer of methane that has seeped from the interior and frozen on the surface. As in the case of Pluto, the methane has undergone chemical transformations, probably due to the faint solar radiation, that have caused the methane layer to redden. But the methane surface on Xena is somewhat more yellowish than the reddish-yellow surface of Pluto, perhaps because Xena is farther from the sun.

Brown and Trujillo first photographed Xena with the 48-inch Samuel Oschin Telescope on October 31, 2003. However, the object was so far away that its motion was not detected until they reanalysed the data in January of 2005.

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According to the new draft definition, by the International Astronomical Union (IAU), two conditions must be satisfied for an object to be called a "planet." First, the object must be in orbit around a star, while not being itself a star. Second, the object must be large enough (or more technically correct, massive enough) for its own gravity to pull it into a nearly spherical shape. The shape of objects with mass above 5 x 10^20 kg and diameter greater than 800 km would normally be determined by self-gravity, but all borderline cases would have to be established by observation.

If the proposed Resolution is passed, there will be 12 planets in our Solar System; Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon and 2003 UB313. The name 2003 UB313 is provisional, as a "real" name has not yet been assigned to this object. A decision and announcement of a new name are likely not to be made during the IAU General Assembly in Prague, but at a later time. The naming procedures depend on the outcome of the Resolution vote. There will most likely be more planets announced by the IAU in the future. Currently a dozen "candidate planets" are listed on IAU's "watchlist" which keeps changing as new objects are found and the physics of the existing candidates becomes better known.

The draft "Planet Definition" Resolution will be discussed and refined during the General Assembly and then it (plus four other Resolutions) will be presented for voting at the 2nd session of the GA 24 August between 14:00 and 17:30 CEST.

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Astronomers are expected to add at least one new planet to the nine already known to exist in our solar system.

The new body, provisionally named Xena, is nine billion miles from the Sun, about 100 times more distant than the Earth and well beyond Pluto.
Its diameter is 1,490 miles, 70 miles greater than that of Pluto, the smallest and most distant planet, which may qualify it for planetary status.
The decision will be taken next month at a meeting of the International Astronomical Union (IAU) in Prague when 2,000 astronomers will be asked to vote on the “expansion” of the solar system.

Xena is the largest of many similar bodies recently found in orbits beyond Pluto. Some astronomers argue that declaring them all planets will devalue the term. Others warn that a scientifically “purist” approach would mean stripping Pluto of its planetary status — which could be deeply unpopular with the public.

"We have been seeking a compromise solution" - Iwan Williams, professor of mathematics and astronomy at Queen Mary, University of London, who chairs a committee set up by the IAU to define what a planet is.

Its report will be presented to the IAU next month. Williams has not disclosed his precise proposals but said:

"We had to decide whether to stick to a purely scientific approach or to consider other aspects such as culture and history"

Some astronomers believe that the term “planet”should be limited to the four rocky orbs, Mercury, Venus, Earth and Mars, and the four gas giants, Jupiter, Saturn, Uranus and Neptune.
Pluto was accepted as the ninth planet only because Clyde Tombaugh, who discovered it in 1930, misjudged its size, claiming that it was larger than Earth. Its actual mass is 400 times less.
By the time the mistake had been corrected, Pluto had entered the textbooks as the only planet to have been discovered by an American. Any attempt to question its status since then has been fiercely opposed by American scientists.
Professor Brian Marsden, a Briton who directs the minor planet centre at the Harvard Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, says US astronomers threatened to throw him into a hotel swimming pool after a 1980 conference where he called for Pluto to be reclassified as an asteroid.

"This issue has been overlooked for far too long. The term planet should have a proper scientific definition" - Professor Brian Marsden.

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