- Astronomical detective work led to the stunning discovery
of a large new world beyond Pluto and hiding in plain sight. The object
could be the biggest in the Kuiper belt of rocky objects that orbit the
outer reaches of the solar system.
-
- The first data made public about the object suggested
the object could be up to twice the size of Pluto, but newly revealed observations
indicate the object is about 70% Pluto's diameter.
-
- The find suggests more such objects are waiting to be
discovered and is likely to reignite the fierce debate about what constitutes
a planet.
-
- On Thursday, an email with the subject, "Big TNO
discovery, urgent" was sent to a popular astronomy mailing list. The
message described the discovery of a "very bright" object that
was creeping along slowly beyond the orbit of Neptune - making it a Trans-Neptunian
Object, or TNO.
-
- If the reflectivity is as dim as most other distant,
rocky objects that have been studied, the object "would be larger
than Pluto," Jose-Luis Ortiz, an astronomer at the Sierra Nevada Observatory
in Spain, wrote in the email. Pluto is about 2300 kilometres across. Sleepless
night
-
- Ortiz and colleagues discovered the object when they
re-analysed observations they had made in 2003. Then, they scoured older
archives and found the object in images dating back to 1955.
-
- Based on these so-called "precoveries", they
calculated the object's orbit and sent urgent emails asking people around
the globe to observe the new find.
-
- Amateur observers Salvador Sanchez, Reiner Stoss, and
Jaime Nomen found it on Thursday using a 30-centimetre telescope in Mallorca,
Spain. "I am not going to sleep tonight," said Stoss, a mechanical
engineering student in Darmstadt, Germany. "To find an object bigger
than Pluto - it's like the X Prize," he said, referring to the $10
million prize for private spaceflight won in 2004.
-
- The observations were then verified by the International
Astronomical Union's Minor Planet Center (MPC) in Cambridge, Massachusetts,
US, which designated the object 2003 EL61.
-
- Estimates of the object's brightness posted by the MPC
on Friday at 0027 GMT suggested the object could be as large as twice Pluto's
diameter if it was relatively non-reflective object. In the hours since,
another team of astronomers revealed independent data on the object taken
with some of the world's most powerful telescopes. They give the object's
size at about 70% Pluto's diameter, in line with estimates for a relatively
reflective object in the first MPC notice. They say also say the object
is orbited by a tiny moon. Time to move
-
- The MPC reports the object is about 51 Astronomical Units
from the Sun - 1 AU is the distance between the Earth and the Sun. Its
orbit brings it comes as close to the Sun as 35 AU, while Pluto maintains
an average distance of about 39 AU. "Someone should have found this
before," Brian Marsden, director of the MPC, told New Scientist.
-
- One reason they did not is the object's speed, suggests
Stoss. Many surveys of Near Earth Objects take a trio of images spaced
20 minutes apart to search for telltale movement in relation to background
stars.
-
- But 2003 EL61 is too far away to detect its progress
in that time. Ortiz's survey compares images taken a day apart. "They
give the object time to move," Stoss says.
-
- Another reason may be the plane of the object's orbit,
says Tommy Grav, an astronomer at the University of Hawaii in Manoa, US.
That plane is tilted by 28° with respect to the orbital plane of most
planets, where surveys tend to scan the skies for Near Earth Objects. Off
kilter
-
- 2003 EL61 is even more off-kilter than Pluto, which orbits
in a plane tilted by 17°. "Pluto was pushed out of the plane of
the solar system when Neptune moved outwards" soon after the solar
system formed, Grav told New Scientist. "It's possible this object
has suffered something similar."
-
- The discovery, coupled with other recent finds such as
Sedna and Quaoar, suggests other large objects may lurk in the murky region
beyond Neptune.
-
- "Some people have claimed we'd never find something
as bright as this out there," says Grav. "But there may be something
even further out that's moving so slowly we haven't seen it yet."
-
- And the discovery is likely to revive previous fierce
debates about what constitutes a planet and even how astronomical objects
are named. "But don't even start that discussion," Stoss jokes.
He says future observations of the object's colour and brightness could
reveal its true size, shape and rotation period.
-
- © Copyright Reed Business Information Ltd.
-
- http://www.newscientistspace.com/article.ns?id=dn7751
|