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Universe Today wrote:The New 10th Planet Is Larger than Pluto

Summary - (Wed, 01 Feb 2006) Astronomers have confirmed that the newly discovered 10th planet is larger than Pluto. Nicknamed 2003 UB313 for now, the new planet has a diameter of 3,000 km (1,850 miles) which is 700 km (435 miles) larger than Pluto. These new observations were made using a sensitive sensor on the IRAM 30-m telescope that measured the heat emitted by the new object, and found it had a similar reflectivity to Pluto. This allowed them to calculate its size.

Full Story -
Claims that the Solar System has a tenth planet are bolstered by the finding by a group lead by Bonn astrophysicists that this alleged planet, announced last summer and tentatively named 2003 UB313, is bigger than Pluto. By measuring its thermal emission, the scientists were able to determine a diameter of about 3000 km, which makes it 700 km larger than Pluto and thereby marks it as the largest solar system object found since the discovery of Neptune in 1846 (Nature, 2 February 2006).

Like Pluto, 2003 UB313 is one of the icy bodies in the so-called Kuiper belt that exists beyond Neptune. It is the most distant object ever seen in the Solar System. Its very elongated orbit takes it up to 97 times farther from the Sun than is the Earth - almost twice as far as the most distant point of Pluto's orbit - so that it takes twice as long as Pluto to orbit the Sun. When it was first seen, UB313 appeared to be at least as big as Pluto. But an accurate estimate of its size was not possible without knowing how reflective it is. A team lead by Prof. Frank Bertoldi from the University of Bonn and the Max Planck Institute for Radio Astronomy (MPIfR) and the MPIfR's Dr. Wilhelm Altenhoff has now resolved this problem by using measurements of the amount of heat UB313 radiates to determine its size, which when combined with the optical observations also allowed them to determine its reflectivity. "Since UB313 is decidedly larger than Pluto," Frank Bertoldi remarks, "it is now increasingly hard to justify calling Pluto a planet if UB313 is not also given this status."

UB313 was discovered in January 2005 by Prof. Mike Brown and his colleagues from the Californian Institute of Technology in a sky survey using a wide field digital camera that searches for distant minor planets at visible wavelengths. They discovered a slowly moving, spatially unresolved source, the apparent speed of which allowed them to determine its distance and orbital shape. However, they were not able to determine the size of the object, although from its optical brightness it was believed to be larger than Pluto.

Astronomers have found small planetary objects beyond the orbits of Neptune and Pluto since 1992, confirming a then 40-year old prediction by astronomers Kenneth Edgeworth (1880-1972) and Gerard P. Kuiper (1905-1973) that a belt of smaller planetary objects beyond Neptune exists. The so-called Kuiper Belt contains objects left from the formation of our planetary system some 4.5 billion years ago. In their distant orbits they were able to survive the gravitational clean-up of similar objects by the large planets in the inner solar system. Some Kuiper Belt objects are still occasionally deflected to then enter the inner solar system and may appear as short period comets.

In optically visible light, the solar system objects are visible through the light they reflect from the Sun. Thus, the apparent brightness depends on their size as well as on the surface reflectivity. Latter is known to vary between 4% for most comets to over 50% for Pluto, which makes any accurate size determination from the optical light alone impossible.

The Bonn group therefore used the IRAM 30-meter telescope in Spain, equipped with the sensitive Max-Planck Millimeter Bolometer (MAMBO) detector developed and built at the MPIfR, to measure the heat radiation of UB313 at a wavelength of 1.2 mm, where reflected sunlight is negligible and the object brightness only depends on the surface temperature and the object size. The temperature can be well estimated from the distance to the sun, and thus the observed 1.2 mm brightness allows a good size measurement. One can further conclude that the UB313 surface is such that it reflects about 60% of the incident solar light, which is very similar to the reflectivity of Pluto.

"The discovery of a solar system object larger than Pluto is very exciting," Dr. Altenhoff exclaims, who has researched minor planets and comets for decades. "It tells us that Pluto, which should properly also be counted to the Kuiper Belt, is not such an unusual object. Maybe we can find even other small planets out there, which could teach us more about how the solar system formed and evolved. The Kuiper Belt objects are the debris from its formation, an archeological site containing pristine remnants of the solar nebula from which the sun and the planets formed." Dr. Altenhoff made the pioneering discovery of heat radiation from Pluto in 1988 with a predecessor of the current detector at the IRAM 30-meter telescope.

The size measurement of 2003 UB313 is published in the 2 February 2006 issue of Nature. The research team includes Prof. Dr. Frank Bertoldi (Bonn University and MPIfR), Dr. Wilhelm Altenhoff (MPIfR), Dr. Axel Weiss (MPIfR), Prof. Dr. Karl M. Menten (MPIfR), and Dr. Clemens Thum (IRAM).

UB313 is a members of a ring of some 100,000 objects on the outskirts of the solar system, beyond Neptune at distances over 4 billion km from the sun, over 30 times the distance between Earth and Sun. The objects in this "Kuiper belt" circle the sun in stable orbits with periods of about 300 years. In the middle of the last century, the existence of a ring of small planetary objects was first suggested by the astronomers Kenneth Edgeworth (1880-1972) and Gerard P. Kuiper (1905-1973), but the first discovery of a "Kuiper belt object" was not until 1992. By now, over 700 such objects are known. UB313 is somewhat different from the normal Kuiper belt in that its orbit is highly excentric and 45 degrees inclined to the ecliptic plane of the planets and Kuiper Belt. It is likely that is originated in the Kuiper Belt and was deflected to its inclined orbit by Neptune.

Original Source: Max Planck Society

Cynical Cat wrote:Good to see you back Erica.

*Smothers Brattty in fuzzy-wuzzy kittens*

I had extra left over from Caz.

Petrosjko wrote:Pluto is very much of the opinion that it is a planet.

Hubble Finds Xena's Only a Little Bigger Than Pluto

Wed, 12 Apr 2006 - The powerful Hubble Space Telescope has finally been brought to bear on the newly discovered 10th planet (aka Xena), to help answer the question: is it really bigger than Pluto? Hubble is the only instrument that can make an actual visible light observation of Xena's diameter. Hubble found that Xena is is about 2400 km (1,490 miles) across, which makes it only 113 km (70 miles) larger than Pluto. This makes the 10th planet unusually bright, probably covered in brilliant white methane snow.


For the first time, NASA's Hubble Space Telescope has seen distinctly the "tenth planet," currently nicknamed "Xena," and has found that it is 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.

"Hubble is the only telescope capable of getting a clean visible-light measurement of the actual diameter of Xena," said Mike Brown, planetary scientist at the California Institute of Technology in Pasadena, Calif. Brown's research team discovered Xena, officially cataloged as 2003 UB313, and its results have been accepted for publication in the Astrophysical Journal.

Only a handful of images were required to determine Xena's diameter. Located 10 billion miles from Earth with a diameter a little more than half the width of the United States, the object is 1.5 pixels across in Hubble's view. That's enough to make a precise size measurement.

Because Xena is smaller than previously thought, but comparatively bright, it must be one of the most reflective objects in the solar system. The only object more reflective is Enceladus, a geologically active moon of Saturn whose surface is continuously recoated with highly reflective ice by active geysers.

Xena's bright reflectivity is possibly due to fresh methane frost on its surface. The object may have had an atmosphere when it was closer to the sun, but as it moved to its current location farther away this atmosphere would have "frozen out," settling on the surface as frost.

Another possibility is that Xena leaks methane gas continuously from its warmer interior. When this methane reaches the cold surface, it immediately freezes solid, covering craters and other features to make it uniformly bright to Hubble's telescopic eye.

Xena's takes about 560 years to orbit the sun, and it is now very close to aphelion (the point on its orbit that is farthest from the sun).Brown next plans to use Hubble and other telescopes to study other recently discovered Kuiper Belt objects that are almost as large as Pluto and Xena. The Kuiper Belt is a vast ring of primordial icy comets and larger bodies encircling Neptune's orbit.

Finding that the largest known Kuiper Belt object is a virtual twin to Pluto may only further complicate the debate about whether to categorize the large icy worlds that populate the belt as planets. If Pluto were considered to be the minimum size for a planet, then Xena would fulfill this criterion, too. In time, the International Astronomical Union will designate the official name.

The Hubble Space Telescope is an international cooperative project between NASA and the European Space Agency. The Space Telescope Science Institute in Baltimore conducts Hubble science operations. The Institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc., Washington

Cpl Kendall wrote:They nicknamed it Xena? Will they call it's soon to be discovered moon Gabriel? *snicker*
What? I thought it was funny.

Batman wrote:

Cpl Kendall wrote:They nicknamed it Xena? Will they call it's soon to be discovered moon Gabriel? *snicker*
What? I thought it was funny.

For whatever it's worth so did I, and while I still think they should call it 'Bob' it wouldn't surprise me if the Xena moniker stuck and/or if they called whatever moon it might have 'Gabrielle'. Scientists can be surprisingly silly sometimes. Quark flavours, anyone?

Gabrielle, a moon of Xena, was discovered on September 10, 2005. The discovery was made using the Laser Guide Star Adaptive Optics (LGS AO) system at the W.M. Keck Observatory. Images were taken at infrared wavelengths (2.1 microns) using the NIRC2 imaging camera over a period of 40 minutes. Gabrielle is located to the right of Xena in the picture.

Xena moves across the sky at a different rate to distant stars, as all planets do. We know that the object is the moon of Xena because it follows Xena across the sky. By contrast, a star would appear to remain fixed. When the images are processed, the background stars appear to streak across the sky while Xena's companion does not. From these observations, we can say that Xena is 60 times brighter than Gabrielle. More observations are planned to calculate the orbit of Gabrielle around Xena, which appears to have an orbital period of about 14 days. From the orbital period and semi-major axis (approximately the average distance between Xena and Gabrielle), it is possible to determine the mass of Xena and confirm that it is more massive than Pluto, as we suspect, and hence a tenth planet. However, it is up to the International Astronomical Union to decide whether to confer planet status to Xena, which depends on the definition they decide upon for what is a planet.

Cpl Kendall wrote:Mind if I post this at SDN Mayabird?