Jena's Rants
2001-08-14 14:48:01 (UTC)

That's what's wrong with these plantets today, NO PARENTING!

New evidence offered for planets without parent stars

A pair of British astronomers revealed new evidence Tuesday
to support their controversial discovery of a group
of "free-floating" planets in a distant nebula that do not
orbit any star.

Philip Lucas of the University of Hertfordshire and Patrick
Roche of Oxford University said Tuesday that new studies of
the Orion Nebula had confirmed the existence of a number of
bodies too small to be stars. The results were released in
Cambridge, England at the annual National Astronomy

Lucas and Roche first announced a year ago that they had
spotted 13 new objects in infrared images of the nebula,
taken by a new camera at the United Kingdom Infrared
Telescope (UKIRT) in Hawaii, that were too faint to be
ordinary stars or less massive brown dwarfs. They called
these objects "free-floating planets" since they were
smaller than 13 times the mass of Jupiter, a widely
accepted boundary between planets and brown dwarfs.

These findings were treated rather skeptically by
astronomers, some of whom argued that the planets could be
more distant stars that are not part of the nebula, but are
aligned with it as viewed from the Earth. To test this
possibility, Lucas and Roche took infrared spectra of the
putative planets to measure their temperatures, from which
they could derive their masses.

Twenty of the objects that they studied had the
characteristic absorption spectrum of water vapor, key
evidence that the objects are too cool to be more distant
stars. Using theoretical work on the atmospheres of giant
bodies performed by scientists in France and the US they
calculated that the planets have masses 5 to 13 times that
of Jupiter.

"It's exciting to find these planet-sized objects floating
around in space," said Lucas. "Our new results provide the
first steps in the exploration of their physical

The two astronomers acknowledge that the term "planet" may
be inappropriate for these objects, even those they have
masses similar to extrasolar planets recently discovered
orbiting other stars. Roche noted in an interview last
year, when the discovery was first announced, that these
objects likely developed independently, rather than form
around a star like an ordinary planet and later escape
through gravitational interactions.

Keeping this in mind this distinction, Lucas and Roche
suggested Tuesday that a new designation be given to these
objects: "planetars", playing on existing names for two
other types of stars, pulsars and magnetars. A committee of
the International Astronomical Union recently suggested an
alternative term, "sub-brown dwarfs."

Regardless of their name, these small objects -- runts of
the litter of stellar formation -- may help astronomers
better understand how stars are created. "The
identification and study of these objects is extremely
interesting in itself," said Roche, "but it can also aid
our understanding of the star formation process, which is
one of the major mysteries in astronomy."