[meteorite-list] John Hopkins Astronomers React to Pluto's Planetary 'Demotion'

[Ron Baalke]

THE JOHNS HOPKINS UNIVERSITY
OFFICE OF NEWS AND INFORMATION
901 S. Bond Street, Suite 540
Baltimore, MD 21231
Phone: (443) 287-9960 / Fax: (443) 287-9920

August 24, 2006
FOR IMMEDIATE RELEASE
CONTACT: Dennis O'Shea, dro at jhu.edu,
  or Phil Sneiderman, prs at jhu.edu
(443) 287-9960

JOHNS HOPKINS ASTRONOMERS REACT TO PLUTO'S PLANETARY 'DEMOTION'

Several Johns Hopkins University astronomers described a decision Thursday 
to strip Pluto of its planetary status as a "muddled" ruling that is 
unlikely to settle ongoing debates over how to define a planet and whether 
the term should apply to Pluto. In an informal poll, only one astronomer 
was pleased to hear about Pluto's new status.

Their reactions came after a vote by the International Astronomical Union, 
meeting in Prague, that defined a planet as "a celestial body that is in 
orbit around the sun, has sufficient mass for its self-gravity to overcome 
rigid body forces so that it assumes a  nearly round shape, and has 
cleared the neighborhood around its orbit."  Because Pluto does not meet 
the last criterion, the IAU demoted it to "dwarf planet" status.

The decision leaves the solar system with only eight planets. Since its 
discovery in 1930, Pluto has been considered the system's ninth planet.

Following are some comments about the IAU decision from astronomers at the 
Henry A. Rowland Department of Physics and Astronomy at the Johns Hopkins 
University's Krieger School of Arts and Sciences and The Johns Hopkins 
University Applied Physics Laboratory. The Applied Physics Laboratory is 
managing the mission of NASA's New Horizons spacecraft, which was launched 
earlier this year on 9 1/2-year journey to explore the distant region that 
includes Pluto.

* Andrew Cheng, Johns Hopkins University Applied Physics Laboratory:
"I think the IAU vote is a muddled compromise that will not settle the 
question of 'What is a planet?' Pluto is not a 'planet' according to 
resolution 1, but it is a 'dwarf planet' by resolution 2. So is it a 
'planet?' I thought so before and still think so now -- but those who did 
not think so before can now point to the IAU definition and say that Pluto 
is really not a planet but a sort of second-class citizen.
"Actually, that is the same situation that has prevailed with Ceres, other 
asteroids, and comets for many years (centuries in the case of some of 
these objects). Those objects were known as minor planets before, but now a 
few of the minor planets have been promoted to 'dwarf planets.'

"So I suppose I should be happy that Pluto wasn't demoted all the way into 
the minor planet category."

* Harold (Hal) Weaver, Johns Hopkins University Applied Physics Laboratory 
and New Horizons project scientist:
"I don't expect the hoopla over the demotion of Pluto from the realm of 
'classical planets' to have any effect on the conduct of the New Horizons 
mission. The scientific investigation of Pluto remains an important 
component of our effort to understand the processes that shaped the outer 
solar system, even if some of the objects in that region defy our efforts 
to categorize them. The New Horizons mission remains as viable as ever 
because it will provide the initial reconnaissance of one of the solar 
system's newly discovered frontiers.
	
"Regarding the resolution itself, I'm with Andy Cheng in concluding that 
the situation is still somewhat muddled. What exactly is meant by a planet 
'clearing its neighborhood?' Since many 'plutinos' - (including Pluto) - 
cross Neptune's orbit, I'd say Neptune's neighborhood still needs some 
clearing!  It just seems a bit risky to me to base a definition on a 
theoretical construct ('dynamically cleared regions') that's only 
approximate at best and may change significantly as our understanding of 
planet formation evolves over time.
	
"I further note that there have been particularly large swings in the 
theories of outer solar system dynamical evolution during the past decade. 
What was 'conventional wisdom' five years ago has been replaced with the 
latest fad, and I don't expect that situation to change any time soon."
	
* Karl Glazebrook, professor in the Department of Physics and Astronomy:
"What is meant by 'clearing its orbit?' How does this relate to having an 
orbit overlapping Neptune? Clearly Neptune has not cleared its orbit.

"They should have gone with something clean like a size criterion. Seems to 
me like a muddled compromise which will just cause more problems (what 
about some of the weird orbits extra-solar planets have?) and the issue 
will have to be revisited again."

* William P. Blair, research professor in the Department of Physics and 
Astronomy and chief of observatory operations for NASA's Far Ultraviolet 
Spectroscopic Explorer Satellite, operated by Johns Hopkins:
"I think the demotion of Pluto into the realm of other minor objects 
outside the orbit of Neptune is the most consistent thing to do to 
straighten out the nomenclature of our solar system.  However, I don't find 
the wording of the official planet definition to be very clear, and hence 
it will continue to be open to interpretation.

"I find it comforting to know, though, that Pluto hasn't changed just 
because of our nomenclature.  It is the same today as it was yesterday, and 
as it has been for thousands of years.  It is still the most accessible of 
the objects beyond Neptune that we can study, and studying it should reveal 
much new information about the outer solar system."

* Richard Conn Henry, professor in the Department of Physics and Astronomy:
"I am delighted that rationality has prevailed!  Keep in mind that our own 
Sun is a dwarf star ... and Pluto is now a dwarf planet!  Pluto is an 
extremely interesting and important object, and I am overjoyed that NASA's 
New Horizons mission is on its way to Pluto!  Hurrah for Pluto, first dwarf 
planet to be visited by a NASA mission!"

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