[meteorite-list] New World May Be Double Pluto's Size

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Jul 29 10:50:17 2005
Message-ID: <200507291449.j6TEnML04542_at_zagami.jpl.nasa.gov>

http://www.newscientistspace.com/article/dn7751

New world may be double Pluto's size
Maggie McKee
New Scientist
29 July 2005

An object possibly twice the size of Pluto has been found - hiding in
plain sight. The discovery could be the biggest world in the Kuiper belt
of rocky objects that orbit the outer reaches of the solar system.

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.

Its exact size cannot be determined because the reflectivity of its
surface is not known. But if the reflectivity is as dim as most other
distant, rocky objects that have been studied, it could be twice as wide
as Pluto, which is about 2300 kilometres across.
          
Sleepless night

Jose-Luis Ortiz, an astronomer at the Sierra Nevada Observatory in
Spain, and colleagues discovered the object
<http://www.iaa.es/~ortiz/brighttno.html> 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.

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, rotation period, and any companion moons.

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http://news.bbc.co.uk/1/hi/sci/tech/4726733.stm

Distant object found orbiting Sun
By Dr David Whitehouse
BBC News website

Astronomers have found a large object in the Solar System's outer
reaches. It is being hailed as "a great discovery".

Details of the object are still sketchy. It never comes closer to the
Sun than Neptune and spends most of its time much further out than Pluto.

It is one of the largest objects ever found in the outer Solar System
and is almost certainly made of ice and rock.

It is at least 1,500km (930 miles) across and may be larger than Pluto,
which is 2,274km (1,400 miles) across.

The uncertainty in estimates of its size is due to errors in its
reflectivity.

It might be a large, dim object, or a smaller, brighter object. Whatever
it is, astronomers consider it a major discovery.

In 2004 scientists discovered Sedna, a remote world that is 1,700 km
across.

Frantic checking

Two groups of scientists will be claiming the latest discovery.

It was picked up by astronomers of the Institute of Astrophysics in
Andalusia as part of a survey of the outer solar system for new objects
that they have been carrying out since 2002.

"We found a bright, slow moving object while checking some older images
of our survey for Trans-Neptunian Objects," Jose-Luis Ortiz, one of the
objects co-discoverers, told the BBC News website.

It was subsequently designated 2003 EL61.

However, American astronomers also appear to have detected it.

The same team that found Sedna have designated it K40506A after it was
picked up by the Gemini telescope and one of the twin Keck telescopes in
Hawaii.

They are due to present their findings at a conference in Cambridge in
September.

Because the object is relatively bright, astronomers are frantically
checking other observations that may have picked it up, particularly
robotic sky surveys.
Received on Fri 29 Jul 2005 10:49:21 AM PDT