The survey also yielded the new planet and two other objects only slightly smaller than Pluto, which Brown kept quiet as he analysed the survey data and made new observations to learn more about UB The survey first spotted the new planet in October , but it was not until 8 January that Brown realised the object was so distant that its brightness meant it had to be very big.
Calculations showed it was near the most distant point of its year orbit — in years it will be only 36 times as far from the Sun as the Earth is.
A graphic of its orbit can be viewed here. Infrared observations could provide that information, but the planet was too faint and cold for the Spitzer Space Telescope to spot.
But Spanish astronomers independently discovered one of the two other big new Kuiper Belt objects, and on 28 July the Minor Planet Center at the Harvard-Smithsonian Center for Astrophysics in Massachusetts published an orbit based on their data for the object it designated EL Like Sedna, however, Quaoar is smaller than Pluto. The object detected by the Spanish astronomers is about 52 times the Earth-sun distance at its farthest point from the sun.
It is different from the previously discovered Kuiper bodies in that it has a moon that circles it every 49 days in a highly elliptical orbit. That moon has about 1 percent of the mass of the parent body. Brown had also been tracking EL61 and was surprised when the Spanish astronomers made their announcement Thursday. He said he has also been tracking another object, about the same size and distance from the sun as EL61, but brighter still.
Brown said UB can easily be observed by amateurs with good telescopes. Since there was no naturally-occurring guide star sufficiently bright enough with which to study Xena, astronomers used the Keck Laser Guide Star system to create an artificial star instead. Brown and Antonin H. Campbell, Jason C. Chin, Al Conrad, Scott K. Hartman, Erik M. Johansson, Robert E.
Lafon, Paul J. Stomski Jr. Summers and Peter L. 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. Thereby the apparent brightness depends on their size as well as on the surface reflectivity.
The temperature can be well estimated from the distance to the sun, and thus the observed 1. Altenhoff exclaims, who has researched minor planets and comets for decades. 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.
Altenhoff made the pioneering discovery of heat radiation from Pluto in with a predecessor of the current detector at the IRAM meter telescope. The size measurement of UB is published in the 2 February issue of Nature. The research team includes Prof. Karl M. Frank Bertoldi Tel.
Wilhelm Altenhoff Tel. Menten Tel. Note added Measuring the size of such a tiny and moving object is a very difficult task. We were pleased to learn that our claim that UB is larger than Pluto, was confirmed. However, we were surprised by the smaller diameter implied by the new measurements and the implied high albedo reflectivity. Claims that the Solar System has a tenth planet are bolstered by the finding by a group lead by Bonn astrophysicists that this putative planet, announced last summer and tentatively named UB, is bigger than Pluto.
Ernst Kreysa.
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