[NYT] For the record, Upsilon Andromedae...

Rohit Khare (rohit@uci.edu)
Fri, 16 Apr 1999 11:47:32 -0700

[This kind of momentous story seems odd in a daily newspaper
alongside the ephemera of our age. Reminds me of what initially
strikes one as the 'stilted' style of the Wall Street Journal Year
1000 issue. (Drat! the January 11, 1999 year-1000 issue was free
on-line and quite a stunning exhibit, but its public link has
vanished from wsj.com. Any interactive-journal subscribers have
access to find out? Also, enough students on FoRK to set up a group
educational buy? (req. sponsoring professor; $88/year including
online access)]

Funny, the NYT's 'front pages on this day in history' two days ago
had the first report of trouble aboard Apollo 13... also by John
Noble Wilford. I wonder when we, as a species, will have the courage
to launch 200-year scientific experiments by hurling a satellite in
its direction to relay back some real data... RK]

April 16, 1999
At Long Last, Another Sun With a Family of Planets

The solar system is not alone as an array of planets orbiting in the
gravitational embrace of a shining star.
Laying to rest any lingering notion of the Sun's family being a
singular phenomenon in the universe, astronomers announced on
Thursday the detection of three large planets around Upsilon
Andromedae, a solar-type star 44 light-years away.

Solitary planets had been observed around several other stars in the
last four years, but this is the first clear evidence showing another
star accompanied by multiple planets in a stable system bearing some
resemblance to the Sun's.

Two of the planets are several times more massive than Jupiter, the
solar system's giant, which is 318 times heftier than Earth. The
third planet, with at least three-quarters the Jovian mass, is so
close to the star that it completes a full orbit -- its year -- every
4.6 Earth days. Astronomers said that they would not be surprised if
they eventually find other, more distant objects around the star.

Other astronomers greeted the discovery with unbridled enthusiasm.
They called it a major milestone in planetary science. Here, finally,
was what they had eagerly been seeking: another planetary system to
compare with their own. They expected further study of the Upsilon
Andromedae system to challenge some theories of planet formation and
evolution, and probably hatch new ones.

Of even greater philosophical as well as scientific importance, the
discovery encouraged astronomers in their growing belief that the
universe abounds in stars with planetary systems. This, in turn,
increased the probability that some of them include habitable worlds,
scientists said, though no such claim is being made for the newly
discovered system.

"The single planets we found around other stars was a glorious
discovery, but the architecture of other planetary systems had been
missing," Dr. Geoffrey Marcy, a leader of the discovery team, said in
an interview. "Here for the first time, we can see a kinship between
these planets and our own solar system."

Dr. Alan P. Boss, a theorist of planetary systems at the Carnegie
Institution of Washington, who must come to grips with the
implications of the findings, said simply, "This is exciting stuff."

The discovery was made independently by two teams, one from San
Francisco State University and the other from the Harvard-Smithsonian
Center for Astrophysics in Cambridge, Mass., and the National Center
for Atmospheric Research in Boulder, Colo. They joined in announcing
the results at a news conference in San Francisco.

A full report, which has already been reviewed by more than a dozen
independent astronomers, has been submitted for publication in The
Astrophysical Journal.

"Having two completely independent sets of observations gives us
confidence in this detection," said Dr. Debra Fischer, of the San
Francisco team. And Marcy, the team leader and most prolific
discoverer of extra-solar planets, said, "I would bet my house on it."

Although Upsilon Andromedae is a nearby bright star visible to the
unaided eye, the three planets cannot be seen even with the most
powerful telescopes. Astronomers infer their existence, orbits and
minimum masses from years of careful study of their gravitational
effects, characterized as reflex motions, on the host star. In their
orbital courses, the planets tug first one way and then the other on
the star, causing ever-so-slight changes in the star's velocity.

This observational technique has been responsible for the detection
of 18 Jupiter-class extra-solar planets since 1995, when Swiss
astronomers found the first planet around another normal star, 51

Dr. Robert Noyes, a Harvard-Smithsonian astronomer, said the new
observations should dispel any doubts that these objects are true

"A nagging question was whether the massive bodies orbiting in
apparent isolation around stars really are planets," Noyes said in a
statement. "But now that we see three around the same star, it is
hard to imagine anything else."

Dr. Douglas Lin, a theorist at the University of California at Santa
Cruz who has sought to explain how such huge planets could exist so
close to their stars, much closer than Jupiter is to the Sun, said
the new detections should enable scientists to evaluate their various
theories. They are struggling to understand if systems with several
super-Jupiter planets, traveling eccentric orbits close to their
stars, are more typical than the solar system, with its gaseous giant
planets all traveling circular orbits at great distance from the Sun.

"This is a very, very important discovery," Lin said in an interview.
"It tells us that planetary systems are quite ubiquitous, and some of
them are quite stable. It also tells us that the existence of
habitable planets is highly probable."

Although Earth-size planets could exist in the Upsilon Andromedae
system, astronomers said, they would be undetectable with current
search methods. In any event, they would be unlikely to exist in what
astronomers think of as the habitable zone of a planetary system,
close enough to be warmed by the star, like Earth, but not so close
as to be baked like Mercury and Venus. Also, the gravitational forces
of Jupiter class objects in that vicinity would more than likely have
cleared it any small planets.

The discovery teams calculated that the middle planet in the Upsilon
Andromedae system is in an orbit corresponding to the distance of
Venus from the Sun. It is at least twice the mass of Jupiter, making
the complete circuit every 242 days. The outermost known planet, at
least four times more massive than Jupiter, orbits the star about
once every four earth years at a distance comparable to the region
between Mars and Jupiter.

Astronomers suspect that these giant planets are, like Jupiter and
Saturn, huge spheres of gas without a solid surface. But, also like
Jupiter and Saturn, they could have many large moons. Possibly, Lin
speculated, on one of these moons there could be liquid water, and
atmosphere and other conditions conducive to life.
"Who knows," Lin remarked, "on one of those satellites, I would
probably have a beach-front property."

The planet closest to Upsilon Andromedae had already been discovered
by Marcy and Dr. R. Paul Butler in 1996. At the time, they detected
additional motions of the star suggesting other companions, but only
with repeated observations and careful analysis could they be sure.

Astronomers were less surprised by the discovery than relieved. For
several months, they had generally assumed the existence of
extra-solar planetary systems. After all, the Sun is a common type of
star, one of 200 billion in the Milky Way alone, and beyond lie more
than 80 billion other galaxies. It hardly seemed likely that the
Sun's planets were unique.

The latest discovery is expected to tax the ingenuity of theorists.
It had been thought that such giant gas bodies could only form at
great distances from a star, out where temperatures are low enough
for ice to condense and begin the process of planetary formation as
gaseous spheres. Finding the single Jupiter-class object near stars
had forced scientists to invent migration theories, explaining how
the planets might have formed at greater distances and then worked
their way in closer to the star.

"I am mystified at how such a system of Jupiter-like planets might
have been created," Marcy said of the Upsilon Andromedae system.
"This will shake up the theory of planetary formation."
Boss of the Carnegie Institution said the discovery could upset
conventional ideas explaining giant Jupiter-class planets. "Maybe
nature has many ways of making giant planets," he said.

The next milestone, astronomers said, would be finding evidence of
another system with a Jupiter-class planet out at a distance from its
star corresponding to Jupiter's from the Sun.

"Until we do," Marcy said, "there will always be the question of
whether the solar system is a cosmic freak."

Other members of the Harvard-Smithsonian team were Dr. Sylvain
Korzennik, Dr. Peter Nisenson and Adam Contos, a graduate student.
Dr. Timothy Brown of the National Center for Atmospheric Research
worked with them. Their observations were made at the Whipple
Observatory near Tucson, Ariz. The San Francisco team used the Lick
Observatory near San Jose, Calif. Butler, formerly at San Francisco
State and now at the Anglo-Australian Observatory near Sydney, is the
lead author of the journal report on the detections.

It may be a decade or more before spacecraft are in place to look for
Earth-size planets of other stars.
After years of searching and speculation, both fanciful and educated,
the discovery of multiple objects orbiting Upsilon Andromedae marked
the beginning of the science of comparative planetary systems.