'Amateur Astronomy'. Sedna, The First Object Discovered In the Oort Cloud

A Caltech team dedicated to the search of faraway solar system objects (it is this team which found Quaoar in 2002) found a new body last November 2003. But as all 40 bright objects found until now by this team has been ascribed to Kuiper Belt, this one is thought to belong to what is termed "inner Oort Cloud". New object, which is 2003 VB12, has been temporarily dubbed "Sedna", from the Inuit sea goddess

Oort Cloud is a cloud of solar system formation leftovers extending about 1 or maybe 2 light-years from Sun. Kuiper Belt is another leftover zone, closer to Sun, lying beyond Neptune orbit and ending about 500 AU with a sharp decrease at 50 AU (an astronomical unit -AU- is distance Sun-Earth i.e. 93 million miles (150 million km)). Some of the Kuiper Belt Objects found until now have orbits taking them as far or more than farthest point of Sedna orbit but all have their nearest point to Sun inside Kuiper Belt, about 35 AU. What makes Sedna special is that its nearest to Sun is outside Kuiper Belt 50 AU boundary: Sedna never comes to Sun closer than about 76 AU. This characteristic has led discoverers to think that Sedna might be the first of Oort Cloud objects. Although well inside presumed Oort Cloud location, such objects would point to a partition of the latter due to early Sun interaction with nearby sister-stars. Oort Cloud since would be parted into an inner and an outer region. Sedna would be first object of inner Oort Cloud. Quaoar, 20034 WD or Sedna have all been discovered by a Caltech team led by Mike Brown. This team is dedicated to such objects. In the same way that Kuiper Belt Objects are still to discover, other Oort Cloud Objects would await discovery. Orbits of such objects would be more regular than Sedna's and directly located inside the cloud

Some Objects Compared to Sedna
	Distance from Sun in mi (in km, in AU)	Diameter in mi (and km)	Orbital period (in years)	Rotation	Additional data
Sedna	7-84 billion mi (11.4-137 billion km, 76 AU-867 AU)	800-1100 (1290-1770 km)	10,500	40 days	highly elliptical orbit; coolest object in solar system; might have a moon;
Pluto	2.7-4.5 billion mi (4.3-7.2 billion km, 29-48 AU)	1485 (2390 km)	248	6.3	eccentricity 0.244; inclination to the ecliptic: 17.2°; one moon (Charon, 737 mi (1186 km))
Quaoar	3.9 billion mi (6.300 billion km, 42 AU)	800 (1290 km)	285	?	eccentricity less than 0.04; inclination to the ecliptic: 8°; found in June 2002
2004 DW	4.2 billion mi (6,7 billion km, 45 AU)	990 (1600 km)	?	?	found February 2004

Sedna is a very faint object at magnitude 20.5 and at boundary of high-end amateur instruments. It is now interestingly east of the line Mars-Venus in western evening twilight. Sedna is in closing phase of its orbit. It will reach perihelion (nearest to Sun) 72 years from now before heading back to solar system far reaches. Quaoar is magnitude 18.6 as 2004 DW 18.5