THE SOUTHWORTH PLANETARIUM
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Founded January 1970
              "A proud part of Portland's underground."




THE DAILY ASTRONOMER
Thursday, January 21, 2016
New World


Oh, no, not again!

So despaired the descending bowl of Petunias in Douglas Adams' "The
Hitchhiker's Guide to the Galaxy."   We can relate to the petunia's
lament as we are confronted, yet again, with the possibility that the
solar system's planet census number might need to change.  For the
benefit of those few afflicted with rich lives devoid of pointless
diversions, we should offer some background.  In August 2006, that
coterie of sinister intelligences, the International Astronomical
Union, convened its triennial meeting in Prague.  During the last part
of this conference, the remaining members (approximately 450) voted a
motion to reclassify the term "planet."     They specified three
different criteria.   One, a planet has to revolve around the Sun.
Two, its has to be massive enough so that its internal gravity will
mold it into a spherical shape.  Third, it has to also be
gravitationally powerful enough to have incorporated all nearby
material into it.  Pluto doesn't fulfill this third requirement, as it
travels close to the Kuiper Belt, a region from which short period
comets originate.     Pluto, being only 0.2% as massive as Earth, is
unable to attract many of these proximate Kuiper Belt Objects and thus
hasn't cleared its debris field.


Consequently, the IAU has officially declared that our solar system
contains only eight planets.    They have remained steadfast in this
contention despite the widespread condemnations that followed Pluto's
demotion.      Many people insist that the solar system harbors nine
planets, not eight.          Now, astronomers at Cal Tech have found
evidence of what they believe is a highly massive planet well beyond
Neptune.  If their estimates are accurate, this large body could be
ten times more massive than Earth and 20 times farther from the Sun
than Pluto.   At such a distance, its orbital period would be between
10,000 - 20,000 years!    Compare this time period with Pluto's
comparatively brief 248 year period.

The researchers haven't yet observed this planet.   Instead, they have
inferred its existence through observations of some Kuiper Belt
Objects.     Many of these bodies  describe orbits directed toward one
particular direction.    The orientation of so many KBO's toward one
direction suggests the presence of a gravitationally powerful body in
the general vicinity.     Were there no such body, the Kuiper Belt
objects should follow various orbits without any disproportionate
favoritism toward any specific direction.     Computer models based on
these observations have yielded an estimation of the unseen planet's
mass and distance.

What is not yet know is its present location.    The announcement of
the planet's existence will undoubtedly prompt many astronomers to
find it.   Such a search will prove quite challenging.  First, such a
distant planet will be quite faint, as it would only shine through
reflected light.   Secondly, the search field is vast.    This
planet's orbit is not only hundreds of billions of miles long, but it
could, like Pluto, be highly inclined relative to Earth's orbit,
called the ecliptic.      The greater the inclination angle, the wider
the area the planet could occupy.


The "Ninth" planet, as people are now calling it, hasn't yet been
found.    If and when astronomers do locate it, the International
Astronomical Union might be compelled to designate it as a major solar
system planets.     Then, of course, we'll have nine planets again.
Unless, of course, astronomers happen to find yet another planet, in
which case we'll have ten, and, well, let's not discuss it now.


Written by Edward Gleason