[article] New "Large Object" beyond Pluto

mike65

From bbc online

Astronomers have found a large world of ice and rock circling the Sun beyond the most distant planet, Pluto.

Preliminary observations suggest it may be up to 1,800km (1,120 miles) across, making it the largest body other than a true planet to be discovered orbiting the Sun.

Designated 2004 DW, it was found on 17 February by an automated sky survey telescope in California.

Since 1992 about 800 bodies have been found in the outer Solar System; five could be larger than 1,000km (620 miles) across.

Large orbit

2004 DW was found by California Institute of Technology astronomers Chad Trujillo and Mike Brown, and David Rabinowitz of Yale University, the same team that discovered Quaoar in 2002.

With an estimated size of somewhere between 840km (520 miles) and 1,800km it may be larger that Quaoar, which is 1,000km and 1,400km (870 miles) across.

If it is at the upper end of the uncertainty range then 2004 DW is larger than any other object found circling the Sun since Pluto was discovered in 1930 (Pluto is 2,300km across - 1,430 miles).


2004 DW could even be larger than Pluto's moon, Charon which is 1,300km (810 miles) across. It has an orbit that is much larger than Pluto's, being, on average, 2.4 billion km (1.5 billion miles) further out.

Astronomers believe that there are many more so-called "Kuiper Belt Objects" awaiting discovery in the cold, dark, outer reaches of the Solar System.

The Kuiper Belt (KB) is a region inhabited by small worlds of rock and ice. It is similar in some ways to the Asteroid Belt - a region of rocky debris between Mars and Jupiter. However, the KB contains a hundred times more material than all the asteroids put together.

Not a planet

One thing astronomers want to stress is that 2004 DW is not a major planet. Although it is probably slightly larger than half the size of Pluto, there are other objects of a similar size out there which do not, by the current definition, qualify as a planet.

But that is not to say that a new planet could not be found. Experts say there could be a Pluto-sized object lurking in the darkness awaiting discovery.

2004 DW could be a type of object called a "Plutino." Such objects have an orbit related to Pluto's path around the Sun.

Looking back in their archives astronomers have already picked up the new object in images taken in 2002. They will use this observation, and any others they may find further back, to determine its orbit more accurately.

Mike.

LegacyUser

yea, seen it in the times today, 1200 miles diameter, i reckon that makes ten planets in the solar system, though some would say it aint big enough

simu

Originally posted by bananayoghurt
yea, seen it in the times today, 1200 miles diameter, i reckon that makes ten planets in the solar system, though some would say it aint big enough

Yeah, I saw that article too. The Times was hyping it up as being the 10th planet for sure but many astronomists wouldn't agree with that.

albertw

Press conference is tommorrow (Monday) at 1pm EST.

-- snip from Keithg's post on irishastronomy.org --
Graphics supporting this news briefing will be posted Monday on
the Internet by 1 p.m. EST:

http://www.spitzer.caltech.edu/Media/releases/ssc2004-05/telecon/

Images and information about this discovery will be on the
Internet at:

http://www.spitzer.caltech.edu/Media/releases/ssc2004-05
--

Cheers,
~Al

dudara

In all fairness, there's a lot of debate about whether Pluto itself qualifies as a planet. After all, it's less than a sixth of the earth's size, and some other moons in the solar system are larger, including our own and Europa. However, it is in orbit aoound the sun, which implies a planet. But this DW thing is 2 billion km further out again than Pluto, that must extend nearly into the Kuiper Belt surely?

albertw

Originally posted by dudara
In all fairness, there's a lot of debate about whether Pluto itself qualifies as a planet. After all, it's less than a sixth of the earth's size

Terry Mosely put it nicely in a mail to the IFAS earlier:

Some astronomers want to re-classify Pluto from being a planet to being a large EKBO, but the majority voted to retain its planetary status.
So is Sedna a planet or not? I always thought that the totally arbitrary figure of 1000 miles would be a reasonable dividing line between a planet & either an asteroid or an EKBO. It's a nice round figure, which I'm partial to, even if it is in the old imperial units! So I'll regard it as a planet until there's an official designation otherwise!

And sometimes tradition is as good a guide in these matters as anything - after all, we still refer to 'Planetary Nebulae', although they have nothing to do with planets! And we still retain the original constellations, with their weird boundaries (we even have one, Serpens, which is divided in two by another constellation, Ophiuchus!). So if we can put up with those anomalies, surely we can at least keep Pluto as a planet, even if Sedna is eventually classified as an EKBO!

To subscribe to Terrys mails see http://star.arm.ac.uk/nibulletin/ .

Cheers,
~Al

mike65

I belive that any body which can't be arsed to go round the sun in a nice round orbit with the rest of us should not be considered a planet!

Mike.

Dun

So is Sedna a planet or not? I always thought that the totally arbitrary figure of 1000 miles would be a reasonable dividing line between a planet & either an asteroid or an EKBO.

So the sun has no planets?

Are we an asteroid or an EKBO?

jArgHA

Originally posted by dudara
...However, it is in orbit aoound the sun, which implies a planet...

not strictly so, there are thousands of asteroids and comets which orbit the sun, these are certainly not planets.

tis an interesting debate, i guess they should just agree on a size at which anything larger is classified as a planet. By the way what's the 'E' in EKBO ?

jAH

albertw

Originally posted by jArgHA
By the way what's the 'E' in EKBO ?

E is for Edgeworth.

Edgeworth-Kuiper Belt Objects.

Born in 1880 in Westmeath and died in 1972 in Dublin. He worked with the Royal Engineers and later the Royal Signals, and worked in Sudan for a period, returning to Ireland in 1931.

His only paper published in the Journal of the BAA was entitled ' The Evolution of Our Planetary System' in July 1943. In this paper he made reference to a resevoir of comets beyond the planets which occasionally enter the inner solar system. This is the first reference to such a group of objects and was published seven years before the Oort cloud was proposed, and eight years before Kuiper presented the Kuiper belt.

His paper was forgotten and its significance only recognised in the past few years. In light of that we now refer to the collection of objects as Edgeworth-Kuiper Belt Objects.

A longer boigraphical note, from which I gleaned this brief summary is in the Journal of the British Astronomical Association, vol.106, no.6, p.354,
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996JBAA..106..354H

Cheers,
~Al

Gleanndún

Originally posted by Dun
So the sun has no planets?

Are we an asteroid or an EKBO?

ru trying to tell me u think jupiter is less than 1000mi. across? our moon is bigger than that!