Thursday, August 31, 2006

Moons -

Pictures available at this page are showing mostly "planetary satellites". Some of these satellites are bigger than Mercury (the smallest "planet"). Because they are called "moons" and not planets, they are never featured preminently in any astronomy encyclopedia. Yet, if they were not orbiting other planets, they would not be called moons but rocky planets or ice planets.


Sunday, August 27, 2006

Will the hobbit argument ever be resolved? - Nature

Published online: 25 August 2006; | doi:10.1038/news060821-12

Debate over tiny human's evolutionary status is set to rage on.

Michael Hopkin

Only one hobbit skull has ever been found, a fact that fuels the row over its evolutionary status.

P. Brown
For the past two years, researchers have been hotly debating (and coming dangerously close to fighting over) whether the fossils of a diminutive hominin found in Indonesia are those of a previously unknown species. The publication this week of some long-standing doubts over the 'hobbit' fossils show the debate is far from over.

The dispute over the bones of Homo floresiensis has involved allegations of name-calling, nationalistic motives, and wilfully damaging specimens. One camp insists that the tiny inhabitants of the Indonesian island of Flores were a unique species; the other claims that the bones are of a diseased Homo sapiens pygmy. As the debate rages, set out to find whether there will ever be an end to the conflict.

The latest instalment came on Monday, with the publication in Proceedings of the National Academy of Sciences1 of doubts first raised by Indonesia's leading anthropologist, Teuku Jacob, of Gadjah Mada University, shortly after the finds were first published in 2004.

Jacob and his colleagues cite a range of evidence that the 'hobbit' bones bear similarities to features found in various modern pygmies, including a Rampasasa pygmy from Flores who has a receding chin (the single complete hobbit skull features a jaw with no chin at all).

Deformed by disease

The one complete hobbit skull found so far has additional 'deformities' not present in any modern Homo sapiens — but these, Jacob's team argues, have been caused by disease. In their paper, they divide the iconic photograph of the hobbit skull down the middle and create mirror images of the two halves. The two halves look distinctly different — evidence, the team argues, for developmental abnormality.

Peter Brown of the University of New England in Armidale, Australia, one of the team members who unveiled the findings in Nature2,3, retorts that this type of analysis is very prone to bias. "Depending on the camera angle you can produce anything you want from mirror imaging," says Brown. Particularly for a fossil that has been buried and squashed for thousands of years.

Accusations are also flying on both sides of bad conduct. Jacob has been accused of acting out of nationalistic pride and frustration at not having been the one to discover the bones. Meanwhile, authors of the new critique argue that this accusation is motivated by bitterness. "We have been introducing some scientific ideas and there has been quite a bit of name-calling in return," says Jacob's colleague Robert Eckhardt of Pennsylvania State University in University Park.

Bone hunt

The bitter argument over different aspects of the bones' appearance begs the question of whether debates based on morphology will ever come to a definitive conclusion.

Brown remains convinced that definitive evidence of the hobbits' unique evolutionary provenance will emerge by studying further specimens: more skulls with the same features will make it more unlikely that the shape is caused by illness. "I think the issue will be resolved by fossils," says Brown.

The prospects for finding any more fossils look bleak, however. Political wranglings have led to a ban, for the time being, on excavations at Liang Bua, the cave where the hobbits were uncovered. Negotiations to reopen the site next year are ongoing.

Written in code

Some anthropologists have suggested that preserved DNA might provide a more definitive answer. If the Flores remains belong to H. sapiens, its DNA should fall within the range of modern human variation — if it is a unique species, its DNA should be unlike anything seen in modern humans.

But excavation, cleaning and washing of the original specimens, done in part to harden and preserve them, almost certainly destroyed any DNA that might have been present. Attempts to obtain DNA samples (primarily from teeth, in which it should be best preserved) have so far been unsuccessful.

Brown's colleague Mike Morwood remains confident that, if more specimens can be found, they will yield DNA. "Given that DNA has been recovered from 8,000-year-old pig teeth from the site, there is an excellent chance of getting H. floresiensis DNA from future excavated remains," he says.

Brown is less hopeful, however. The hobbits are thought to have died out around 12,000 years ago, and although older DNA has been recovered from Neanderthals and mammoths in Europe, the damp, tropical Indonesian climate degrades DNA far more quickly. "It's a long way from ideal for preserving DNA," he says. "I would be surprised if DNA [from these samples] lasts even 2,000 years."

Probing the past

Dating the bones should provide more clues. Hominin tools have been found on Flores dating back to 880,000 years ago, leading Brown's team to speculate that the ancestors of H. floresiensis arrived then, surviving until perhaps 12,000 years ago (the various bones have been dated as 12,000 to 90,000 years old).

That comes with its own problems. "It is hard to see how the founding populations would have been large enough to survive for 40,000 generations," says Eckhardt. It is also difficult to imagine the population remaining unchallenged for that long, particularly as sea-level rises and falls to create land bridges between islands. Perhaps instead Homo erectus was responsible for the tools, and H. sapiens, arriving much later, for the Liang Bua bones.

But that pushes back the date of H. sapiens in Indonesia — by quite a lot. H. sapiens is thought to have appeared in nearby Australia no more than 60,000 years ago.

Brown says an independent anthropological analysis soon to be published in the Journal of Human Evolution4 suggests that his story is correct: H. floresiensis is a unique species. Although he admits that the idea that the creatures developed their pygmy size while living on the island, as suggested in the original theory, may not be correct. "Now we think they arrived small."

Whatever the truth, the story of the Flores hominins is not over yet.

Visit our newsblog to read and post comments about this story.

  1. Jacob T., et al. Proc Natl Acad. Sci. USA, doi:10.1073/pnas.0605563103 (2006).
  2. Brown P., et al. Nature, 431. 1055 - 1061 (2004). | Article | PubMed | ISI | ChemPort |
  3. Morwood M. J., et al. Nature, 431. 1087 - 1091 (2004). | Article | PubMed | ISI | ChemPort |
  4. Argue D., Donlon D., Groves C.& Groves R. . J. Hum. Evol., doi:10.1016/j.jhevol.2006.04.013 (2006).

Friday, August 25, 2006

Pluto vote 'hijacked' in revolt - BBC

Last Updated: Friday, 25 August 2006, 07:31 GMT 08:31 UK

By Paul Rincon
Science reporter, BBC News

Pluto pictured by the HST (Nasa)
Pluto (L), pictured with its largest moon, Charon, is now a dwarf planet

A fierce backlash has begun against the decision by astronomers to strip Pluto of its status as a planet.

On Thursday, experts approved a definition of a planet that demoted Pluto to a lesser category of object.

But the lead scientist on Nasa's robotic mission to Pluto has lambasted the ruling, calling it "embarrassing".

And the chair of the committee set up to oversee agreement on a definition implied that the vote had effectively been "hijacked".

I have nothing but ridicule for this decision
Alan Stern, Southwest Research Institute

The vote took place at the International Astronomical Union's (IAU) 10-day General Assembly in Prague. The IAU has been the official naming body for astronomy since 1919.

Only 424 astronomers who remained in Prague for the last day of the meeting took part.

An initial proposal by the IAU to add three new planets to the Solar System - the asteroid Ceres, Pluto's moon Charon and the distant world known as 2003 UB313 - met with considerable opposition at the meeting. Days of heated debate followed during which four separate proposals were tabled.

Eventually, the scientists adopted historic guidelines that see Pluto relegated to a secondary category of "dwarf planets".

Drawing the line

Dr Alan Stern, who leads the US space agency's New Horizons mission to Pluto and did not vote in Prague, told BBC News: "It's an awful definition; it's sloppy science and it would never pass peer review - for two reasons.

Pluto discoverer Clyde Tombaugh pictured in 1980 (AP)
Pluto was discovered in 1930 by the American Clyde Tombaugh
"Firstly, it is impossible and contrived to put a dividing line between dwarf planets and planets. It's as if we declared people not people for some arbitrary reason, like 'they tend to live in groups'.

"Secondly, the actual definition is even worse, because it's inconsistent."

One of the three criteria for planethood states that a planet must have "cleared the neighbourhood around its orbit". The largest objects in the Solar System will either aggregate material in their path or fling it out of the way with a gravitational swipe.

Pluto was disqualified because its highly elliptical orbit overlaps with that of Neptune.

But Dr Stern pointed out that Earth, Mars, Jupiter and Neptune have also not fully cleared their orbital zones. Earth orbits with 10,000 near-Earth asteroids. Jupiter, meanwhile, is accompanied by 100,000 Trojan asteroids on its orbital path.

These rocks are all essentially chunks of rubble left over from the formation of the Solar System more than four billion years ago.

"If Neptune had cleared its zone, Pluto wouldn't be there," he added.

Stern said like-minded astronomers had begun a petition to get Pluto reinstated. Car bumper stickers compelling motorists to "Honk if Pluto is still a planet" have gone on sale over the internet and e-mails circulating about the decision have been describing the IAU as the "Irrelevant Astronomical Union".

'Inconvenient arrangements'

Owen Gingerich chaired the IAU's planet definition committee and helped draft an initial proposal raising the number of planets from nine to 12.

The Harvard professor emeritus blamed the outcome in large part on a "revolt" by dynamicists - astronomers who study the motion and gravitational effects of celestial objects.

Artist's impression of New Horizons probe, Nasa
Named after underworld god
Average of 5.9bn km to Sun
Orbits Sun every 248 years
Diameter of 2,360km
Has at least three moons
Rotates every 6.8 days
Gravity about 6% of Earth's
Surface temperature -233C
US probe (above) visits in 2015
"In our initial proposal we took the definition of a planet that the planetary geologists would like. The dynamicists felt terribly insulted that we had not consulted with them to get their views. Somehow, there were enough of them to raise a big hue and cry," Professor Gingerich said.

"Their revolt raised enough of a fuss to destroy the scientific integrity and subtlety of the [earlier] resolution."

He added: "There were 2,700 astronomers in Prague during that 10-day period. But only 10% of them voted this afternoon. Those who disagreed and were determined to block the other resolution showed up in larger numbers than those who felt 'oh well, this is just one of those things the IAU is working on'."


Professor Gingerich, who had to return home to the US and therefore could not vote himself, said he would like to see electronic ballots introduced in future.

Alan Stern agreed: "I was not allowed to vote because I was not in a room in Prague on Thursday 24th. Of 10,000 astronomers, 4% were in that room - you can't even claim consensus.

"If everyone had to travel to Washington DC every time we wanted to vote for President, we would have very different results because no one would vote. In today's world that is idiotic. I have nothing but ridicule for this decision."

He added that he could not see the resolution standing for very long and did not plan to change any of the astronomy textbook he was currently writing.

But other astronomers were happy to see Pluto cast from the official roster of planets. Professor Iwan Williams, the IAU's president of planetary systems science, commented: "Pluto has lots and lots of friends; we're not so keen to have Pluto and all his friends in the club because it gets crowded.

"By the end of the decade, we would have had 100 planets, and I think people would have said 'my goodness, what a mess they made back in 2006'."

Shaking hands

Robin Catchpole, of the Institute of Astronomy in Cambridge, UK, said: "My own personal opinion was to leave things as they were. I met Clyde Tombaugh, who discovered Pluto, and thought, it's nice to shake hands with someone who discovered a planet.

Mike Brown (AP)
Mike Brown's discovery precipitated the Pluto crisis
"But since the IAU brought out the first draft resolution, I was rather against that because I thought it was going to be very confusing. So the best of the alternatives was to keep the eight planets as they are, and then demote Pluto. I think this is a far superior solution."

The need for a strict definition was deemed necessary after new telescope technologies began to reveal far-off objects that rivalled Pluto in size.

The critical blow for Pluto came with the discovery three years ago of an object currently designated 2003 UB313. Discovered by Mike Brown and colleagues at the California Institute of Technology, 2003 UB313 has been lauded by some as the "10th Planet".

Measurements by the Hubble Space Telescope show it to have a diameter of 3,000km (1,864 miles), a few hundred km more than Pluto. 2003 UB313 will now join Pluto in the dwarf planet category.

Mike Brown seemed happy with Pluto's demotion. "Eight is enough," he told the Associated Press, jokingly adding: "I may go down in history as the guy who killed Pluto."

The New Solar System (BBC)

Bill Harnett doesn't plan to change the name of its website "The Nine Planets"

Here is his new message:

"The IAU has changed the definition of "planet" so that Pluto no longer qualifies. There are now officially only eight planets in our solar system. Of course this change in terminology does not affect what's actually out there.

This site will continue to be known as "The Nine Planets"; for me Pluto is an honorary planet or maybe a planet emeritus!"

Given the quality of the material available on this website, it's another reminder that the planet definition will not be easily accepted by a large part of the scientific community.


Thursday, August 24, 2006

Pluto loses planet status - Nature

The quote of the day is the recent newsrelease by Nature:
"Dwarf stars are stars. Dwarves are people," reasons Donald Lubowich, coordinator of astronomy outreach for Hofstra College of Liberal Arts and Sciences in Hempstead, New York. So as far as he is concerned, Pluto — the 'dwarf' planet — is still a planet. (Nature)

It makes me feel a bit better to hear this... Unfortunately, that's not what IAU explained after their vote.
Did anyone notice how the media is confused about how to present the news in simple words?
I still haven't heard a single good news report either on TV or on the Radio.
There has never been so much confusion!


Published online: 24 August 2006; | doi:10.1038/news060821-11

Pluto loses planet status

Tense debate ends with a definition of 'planet'.

Jenny Hogan

Pluto's a dwarf planet, but not a planet... confused yet?

Pluto has been kicked out of our Sun's planetary family by astronomers who voted today to define a planet by three criteria. It failed on one of them.

Astronomers have been battling over the concept of what defines a planet all week at the general assembly of the International Astronomical Union (IAU) in Prague (see our conference newsblog for a blow-by-blow account).

In the end it was decided that to qualify as a planet in orbit around our Sun, a chunk of rock must have been made round by its own gravity; have cleared its neighbourhood of other debris; and not be a satellite of another planetary body.

Mercury, Venus, Earth, Mars, Jupiter, Uranus and Neptune all fulfil these criteria. But Pluto is just one of many bits of icy debris in orbit at the edge of our Solar System, known as trans-neptunian objects. Pluto's membership of the trans-neptunians disqualifies it from being a fully fledged planet because it has not 'cleared its orbit'.


Instead, Pluto is one of a new category of object to be known as 'dwarf' planets (which, not to be confusing, don't fall under an umbrella term of 'planets', and must, by definition, be written with single quote marks around 'dwarf'). These objects satisfy the other criteria, in being round and not a satellite. Ceres, which lies in the asteroid belt between Mars and Jupiter, is also now a 'dwarf' planet.

'Dwarf' planets in Pluto's neighbourhood, including the object nicknamed Xena (UB313), will be given a category of their own. But the IAU's most recent suggestion, that these be named 'plutonian objects', was narrowly voted down, by 186 votes to 183.

This move had been intended to soften the blow of Pluto's demotion. "There is a large Pluto fan club out there that is going to be incensed by our actions," Owen Gingerich, chair of the planetary definition committee, had warned earlier in the week. The rejection of 'plutonian objects' not only disappoints Pluto fans, it also means the category remains nameless.


That astronomers would reach any consensus at all on the concept of a planet looked unlikely earlier this week.

A draft definition issued on 16 August (see 'Planets are round. Will that do?') had received a hostile reaction: it was debated in lively sessions in which astronomers accused IAU officials of keeping them in the dark, and proposing something "silly".

The resolution had to be changed many times before astronomers were even happy voting on it.

But despite the successful vote and the IAU's best efforts at clarity, it seems there is still scope for some confusion. Already at the conference there are hints of problems.

"Dwarf stars are stars. Dwarves are people," reasons Donald Lubowich, coordinator of astronomy outreach for Hofstra College of Liberal Arts and Sciences in Hempstead, New York. So as far as he is concerned, Pluto — the 'dwarf' planet — is still a planet.

Follow the debate on our newsblog.

Pluto loses status as a planet - BBC

Here is the decision of the IAU.
They made the most conservative decision of preserving the appearance of the classic planets line-up... minus Pluto.
The final decision is based on the orbit-related argument that a planet must be the leader of its neighbourhood. If it is not a leader, it will be a new category of object.
Here are my first comments:

1. The definition will have to be rewritten in the next couple of years as more objects are discovered far away at the edge of the solar system. Bigger objects will be found. An object bigger than Mercury will eventually be found. This object may have an unstable orbit.
2. If, eventually, a small object is found to have a stable orbit (because it is truly the biggest one in the neighboorhood), its small size compared with other objects will make its planet-status sound ridiculous (and indeed it will be).
3. More extra-solar planets will be found... showing how orbit-based definition contradict common sense attitude to classify objects by their own characterists only

In the long run, the biggest casualty is science education, the IAU had a chance to show to the non-scientific world that our universe is very diverse. Stars have very diverse characteristics and very diverse environments, yet they are all called stars... no matter what and how they are orbiting.
Asteroids are called asteroids no matter what and how they are orbiting. The so-called Kuiper-Belt Objects will remain mysterious to most people as they are neither planets nor asteroids.

To summarize, the IAU has chosen to narrow down the definition of a planet instead of widening it and including more sub-groups to the current distinction between rocky planets and gas planets.

The main gain of the discussion was a genuine search for the common characteristics of planetary objects. Given the diversity of the universe, it's an impossible task.

A great merit of the new discussion is that it has become empirically easier to identify a planet from... something else. It will not change anything to the work of thousands of scientists who know that each object is unique and cannot easily fit one category or another.

The main casualty is education. We will have a "dull" narrow-minded vision of a simple solar system.

This is not the end of the story. Let us just wait and see.


Pluto loses status as a planet
Artist's impression of Pluto, BBC
Pluto's status has been contested for many years
Astronomers meeting in the Czech capital have voted to strip Pluto of its status as a planet.

About 2,500 experts were in Prague for the International Astronomical Union's (IAU) general assembly.

Astronomers rejected a proposal that would have retained Pluto as a planet and brought three other objects into the cosmic club.

Pluto has been considered a planet since its discovery in 1930 by the American Clyde Tombaugh.

The vote effectively means the ninth planet will now be airbrushed out of school and university textbooks.

The decision was made at a meeting of the International Astronomical Union (IAU) in the Czech capital Prague.

Pluto's status has been contested for many years as it is further away and considerably smaller than the eight other planets in our Solar System.

Since the early 1990s, astronomers have found several other objects of comparable size to Pluto in an outer region of the Solar System called the Kuiper Belt.

Some astronomers believe Pluto belongs with this population of small, icy "Trans-Neptunians", not with the objects we call planets.

Allowances were once made for Pluto on account of its size. At just 2,360km (1,467 miles) across, Pluto is significantly smaller than the other planets. But until recently, it was still the biggest known object in the Kuiper Belt.

That changed with the discovery of 2003 UB313 by Professor Mike Brown and colleagues at the California Institute of Technology (Caltech). After being measured with the Hubble Space Telescope, it was shown to be some 3,000km (1,864 miles) in diameter, making it larger than the ninth planet.

Tuesday, August 22, 2006

Dark matter spied in galactic collision - Nature

Published online: 22 August 2006; | doi:10.1038/news060821-6

Galactic crash reveals mysterious particles.

Geoff Brumfiel

The centers of mass of these galactic clusters (blue) are offset from the massive gas clouds (red). Dark matter might be the cause.

Astronomers have found the strongest evidence so far that mysterious particles that don't interact with light are lurking throughout the Universe.

Doug Clowe from the University of Arizona in Tuscon and his collegaues have spied a cluster of galaxies in which the centre of mass is shifted to the side of the bulk of observable material, in a relatively empty patch of sky. This implies that there must be some 'dark matter' filling up the empty space.

Decades ago, researchers found from watching distant galaxies that their gravitational properties cannot be explained by the visible material: they posited that some 'dark matter' must make up the difference. Dark matter is thought to account for roughly a third of the mass in the Universe, although it has never been directly detected.

But not everyone agrees. Some researchers have questioned whether dark matter exists at all; perhaps, they suggest, the discrepancy seen in the mass of distant galaxies is due to a modification in gravity rather than a mysterious set of particles.

The new observation argues against that.

Mass merger

Clowe and collegaues used NASA's Chandra X-ray satellite to spy on a cluster of galaxies known as 1E 0657-56, which is thought to have been born from the recent merger of two other galactic clusters.

The great thing about this, is that you can say that dark matter does exist.

Sean Carroll
University of Chicago
At visible wavelengths, 1E 0657-56 looks like an average jumble of galaxies. But in the X-ray spectrum, scientists were able to see two massive clouds of dust in between the galaxy clusters, left over from the explosive collision of the original two clusters. These clouds of dust are ten times more massive than the galaxies themselves.

Yet, by observing the way that light from background galaxies is bent by the strong gravitational field of the dust and galaxies in the foreground, the team has concluded that the centre of mass for 1E 0657-56 is shifted out towards the smaller galaxies rather than lying within the more massive dust clouds. So there must be something, they say, filling up the dark patches of these galaxies to lend them extra weight.

"The great thing about this is that you can say that dark matter does exist," says Sean Carroll, a theoretical astrophysicist at the University of Chicago, Illinois.

But not everyone is convinced. A paper accepted by the Monthly Notices of the Royal Astronomical Society1 suggests that modified versions of gravity could still account for the discrepancy.

Visit our newsblog to read and post comments about this story.

  1. Angus G. W., Famaey B.& Zhao H. S. ArXiv, preprint (2006).