Subject: Giant world detected in deep space
Tuesday, 3 July, 2001, 00:53 GMT 01:53 UK
Giant world detected in deep space
2001KX76 shows up as two coloured dots against the stars
By BBC News Online science editor Dr David Whitehouse
Astronomers have found one of the largest objects ever detected orbiting
the Sun.
It was seen in a deep space survey looking for bodies circling the Sun
out near Pluto, the most distant planet. Only planets are larger than
the new object, dubbed 2001 KX76.
The icy, reddish world is over a thousand kilometres in size and
astronomers say there may be even larger ones, bigger than planet Pluto
itself, awaiting discovery.
"What we have seen may be only the tip of the iceberg," co-discoverer Dr
Lawrence Wasserman told BBC News Online.
When we spotted it we just wrote 'wow' on the image, we knew right away
it was a big one
Lawrence Wasserman Lowell Observatory
The world, for it is big enough to be called a world, has a typical
reddish hue and is probably covered in ice. It orbits the Sun beyond
Neptune in the so-called Kuiper Belt - a region that extends far beyond
the known planets.
Since 1992, over 400 Kuiper Belt Objects (KBOs) have been detected.
Their discovery has revolutionised our view of the distant reaches of
our solar system.
It is the sheer size of 2001 KX76 that is exciting astronomers.
"When we spotted it we just wrote 'wow' on the image, we knew right away
it was a big one," Lawrence Wasserman, of the Lowell Observatory in
Arizona, told BBC News Online.
"This object is intrinsically the brightest Kuiper Belt Object found so
far," says Lowell Observatory Director Robert Millis.
"The exact diameter of 2001 KX76 depends on assumptions that astronomers
make about how its brightness relates to its size. Traditional
assumptions make it the biggest by a significant amount, while others
make it larger by at least 5%," he added.
2001 KX76 could be as large as 1270 km (788 miles), bigger than Ceres,
the largest known asteroid - an object that orbits the Sun between Mars
and Jupiter.
It is even larger than Pluto's moon Charon which has an estimated
diameter of 1200 km (744 miles).
Uncertain orbit
2001 KX76 was discovered in the course of the Deep Ecliptic Survey, a
Nasa-funded search for KBOs.
It was seen on 22 May in deep digital images of the southern sky taken
with the 4-metre Blanco Telescope at Cerro Tololo in Chile.
Astronomers estimate that 2001 KX76 is currently at a distance of just
over 6.4 billion km (4 billion miles) from the Sun. Its orbit is
inclined by approximately 20 degrees with respect to the major planets,
but the detailed shape of its orbit remains uncertain.
Available evidence suggests that the newly discovered KBO may be in an
orbital dance with Neptune, orbiting the Sun three times for each time
that Neptune completes four orbits.
"2001 KX76 is so exciting because it demonstrates that significant
bodies remain to be discovered in the Kuiper Belt," Robert Millis
explains.
Lawrence Wasserman agrees: "We have every reason to believe that objects
ranging up to planets as large or larger than Pluto are out there
waiting to be found."
Dr David Jewitt of the University of Hawaii who has discovered many
KBO's, including the first one ever seen, told BBC News Online: "We're
inching up to Pluto. It is just a matter of time until we see Pluto 2,
Pluto 3 and so on."
Robert Millis agrees: "Until the Kuiper Belt has been thoroughly
explored, we cannot pretend to know the extent or the content of the
Solar System."
The researchers hope that other astronomers who have access to large
telescopes over the next few weeks will be able to turn them on 2001
KX76 in the hope of gathering enough light to get a spectrum of the
object