from the NY times, astronomy

Interesting..... (enough so that I'm sending this without making you jump
through the hoop of going to NYT and getting an ID and password etc. -
pain
in the butt, that is) - I figure an infringement I make by posting this
here is made up for by their intrusive questioning and mandatory fields in the
account registration.
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SAN DIEGO, Jan. 9 - Astronomers have discovered two more planetary
systems in the universe, and they appear to bear little or no resemblance to
each other or to the solar system.
In one of the systems, a Sun-like star is accompanied by a massive
planet and an even larger object 17 times as massive as Jupiter. If this
whopper is a planet, it is the largest ever detected, defying current theory.
Scientists suspect that it could be a dim failed star or a type of
astronomical object that has never been observed before. In the other system,
two planets of more normal size are orbiting a small star. But their orbits
are anything but normal. The pair of planets are locked in resonant orbits,
moving in synchrony around the star with orbital periods of 61 and 30 days;
the inner planet goes around twice for each orbit of the outer one. "They are
unique and frightening," the discovery team's leader, Dr.Geoffrey W. Marcy of
the University of California at Berkeley, said of the newfound planetary
systems. "We thought we understood the mass ranges of planets of other stars.
We thought we understood the full diversity of planets." The two systems are
indeed unlike anything observed before, and this makes astronomers wonder,
What is a typical congregation of planets orbiting a central star? Are the Sun
and its planets the oddball system? Are there more kinds of planets in the
heavens than scientists have dreamed of? In announcing the findings here today
at a meeting of the American Astronomical Society, Dr.Marcy confessed that in
particular the system with
the unusually enormous planet - the one with 17 times the mass of
Jupiter,
largest companion of the Sun - called into question the very meaning of
the term "planet." Another team member, Dr.R. Paul Butler of the Carnegie
Institution of Washington, said: "This massive planetary object defies our
expectations for the largest planets. But it's right there next to another
planet. We never expected nature would make such gargantuan planets, and
indeed maybe they aren't planets at all." Dr.Marcy, Dr.Butler and an
associate, Dr.Debra Fischer of Berkeley, sidestepped interpretations of the
formation and evolution of such bizarre planetary families. "I can't wait
until the theorists explain these things to us," Dr.Butler remarked at a news
conference. Dr.Douglas N. C. Lin, a theorist of planetary systems at the
University of California at Santa Cruz, who is not a team member, seemed ready
to accept the challenge. "I'm so excited by these observations," Dr.Lin said.
The discovery compounded the perplexity and confusion raised by earlier
detection of planets beyond the Sun's family, beginning in 1995. Of more than
1,000 stars observed, over 50, all relatively nearby Earth, have so far been
found to be accompanied by single planets.
The first multiplanet system to have been discovered - and until now the
only one - was found two years ago, and its three Jupiter-class planets
are orbiting much closer to their star, Upsilon Andromedae, than Jupiter is to
the Sun. The most recent observations, in research financed by the National
Aeronautics and Space Administration and the National Science Foundation, were
made at the Keck telescope atop Mauna Kea in Hawaii and at the Lick
Observatory near San Jose, Calif. The objects could not be seen in the
telescopes, but the effects of their gravitational pull could be detected in
the distinct wobbles of their stars. Astronomers tracked these perturbations
for at least two years before determining that they signaled the presence of
the two planetary systems. (Page 2 of 2)
Around the Sun-like star HD 168443, which is 123 light-years away in the
constellation Serpens, the astronomers detected one planet orbiting at a
distance comparable to that from the Sun to a point between Mercury and Venus.
Its mass is estimated to be more than seven times Jupiter's, which is toward
the high end of the sizes of previously detected planets outside our solar
system. Farther out, at a distance equivalent to that from the Sun to the
asteroid belt between Mars and Jupiter, the astronomers found what they call
"the mystery object," the object with 17 times Jupiter's mass.
> From previous research, Dr. Marcy and Dr. Butler had concluded that
If it is considered a planet, astronomers said, then there is much about
planetary formation that scientists have yet to learn. Or it could be a brown
dwarf, a starlike object that failed to achieve a mass sufficient to ignite
nuclear fusion and thus shine like a true star. Besides size, the main
difference between a brown dwarf and a planet is their formation. A brown
dwarf, like a star, is formed by the gravitational collapse of a cloud of gas.
A planet is created by the accretion of a core and gases from the disk of gas
and dust surrounding a new star. Dr.Lin, the theorist, said that at present it
was "not possible to rule out one versus the other" explanation for the
mystery object. But he suggested that gravitational instabilities might have
made it difficult for a brown dwarf to emerge as close to a true star as in
this case. No one ruled out the possibility that the object was neither a
brown dwarf nor a planet but instead something new to astronomy. The other
discovery was made around Gliese 876, a red dwarf star only
one-third the mass of the Sun. No planets had previously been found
around so small a star.
The star is only 15 light-years away, in the constellation Aquarius. Its
two planets are of modest size; one is about half the mass of Jupiter, the
other nearly twice Jupiter's. But their fascination is the gravitational lock
step of their orbits. Astronomers had known for more than two years that there
was something there tugging on the star, but the observations were puzzling.
"We were fooled," said another team member, Dr.Steven Vogt, an astronomer
at Santa Cruz. "The synchrony allowed one planet - the smaller, inner
planet
- to hide in the wobble of the other."
Orbiting objects linked in this way are not unheard of. Three of Jupiter's
large satellites - Io, Europa and Ganymede - travel in such a
configuration, as do some of the small satellites of Saturn. Dr.Hal Levison, a
planetary scientist at the Southwest Research Institute in Boulder, Colo.,
noted that in recent computer simulations of
extra-solar
planetary motions, "25 percent of the cases produced planets in
near-resonant orbits."