Free Astronomy Magazine

DWARF PLANETS between 1.5 and 2 hours; a sufficiently adequate strategy for detecting the movement of di- stant objects up to 300 astronomical units (or AU) and even more. Pictures taken on November 5 confirmed the exi- stence of an object of magnitude 23, whose movement was slow enough to place it well beyond any known body in orbit around the Sun: that is to say, 80 AU. To that ob- ject was given the provisional name (still in use) of 2012 VP 113 . In order to de- termine the orbit of 2012 VP 113 and in- vestigate its surface properties, Trujillo and Sheppard studied it for about a year with the Magellan tele- scope (6.5 m diameter) of the Las Campanas Observatory. By combining the apparent mag- nitude with an albedo estimated between 0.1 and 0.4, the two researchers concluded that 2012 VP 113 has a diameter of about 450 km, while the spectral analysis of the light re- flected from it suggest that it may have for- A comparison on different scales of Sedna and 2012 VP 113 ’s orbits with those of the planets, the asteroids belts and the in- ner Oort Cloud. 2012 VP 113 is cur- rently the plane- tary body with the furthest peri- helion, but Sed- na’s aphelion is more than double that reachable by 2012 VP 113 . [NASA/JPL- Cal- tech/R. Hurt (SSC- Caltech)] Below: an animation showing the vastness of 2012 VP 113 ‘s orbit. [Seth Jarvis, Clark Planetarium] Let's see why by taking a small step back in time. It is the autumn of 2012, Chadwick Trujillo (Gemini Observatory) and Scott Sheppard (Carnegie Institution for Science) are keeping under control 52 square de- grees of sky with the telescope Blanco (4 m diameter) of the Cerro Tololo Inter-Ameri- can Observatory, located about 80 km East of La Serena, Chile. The purpose of the re- search is to find objects in slow motion which could belong to the inner part of the Oort Cloud, an environment where until then only one planetary body with known orbit appeared to exist, Sedna, a dwarf plan- et approximately 1500 km in diameter, to whose discovery, occurred in 2003, contri- buted the same Trujillo. For their new observing campaign started with the Blanco telescope, Trujillo and Shep- pard used the most powerful CCD camera in the world, the DECam, which had recently come into service (see l’Astrofilo , Oct 2012 issue). Every single region of the sky framed by the powerful 570-megapixel sensor was photographed three times, at intervals of