Researchers suggest that
huge unseen object orbits on fringe of solar system.
This diagram, produced by NASA's Jet Propulsion Laboratory, shows the nine
planets as a small inset within the much larger Oort Cloud, extending
trillions of miles out from the sun. The hypothetical planet or brown dwarf
would lie about halfway out from the center of the cloud.
Oct. 7, 1999 — Two teams of researchers have proposed the existence of an
unseen planet or a failed star circling the sun at a distance of more than 2
trillion miles, far beyond the orbits of the nine known planets. The theory,
which seeks to explain patterns in comets’ paths, has been put forward in
research accepted for publication in two separate journals.
SPECULATION ABOUT the existence of unseen celestial companions dates back
far before the discovery of Pluto in 1929 — and even figures in more recent
fringe phenomena such as the 1997 “Heaven’s Gate” tragedy and talk of a new
“Planet X.” This latest hypothesis, however, is aimed at answering nagging
scientific questions about how particular types of comets make their way
into the inner solar system.
Some comets, like Halley’s Comet, follow relatively short-period orbits —
circling the sun in less than two hundred years. These comets are thought to
originate in the Kuiper Belt, a disk of cosmic debris that lies beyond
The best way to think of the distances involved is in terms of Astronomical
Units. One AU is the distance from Earth to the sun (93 million miles or
149.6 million kilometers). Pluto, the most distant of the planets, is at 39
AU. The Kuiper Belt extends from 30 AU to perhaps 1,000 AU.
Even further out is the Oort Cloud,
a spherical haze of comets surrounding the solar system at
distances between 10,000 AU and more than 50,000 AU.
That’s where long-period comets such as Hale-Bopp are thought to come from.
For some time, astronomers have noticed that the directional patterns of
these comets are not completely random. And after years of study, some
researchers are reporting that the patterns hint at something big out there
perturbing the cometary paths.
WHAT COULD IT BE?
No telescope has yet detected this object. But on the basis of its
gravitational effect, John B. Murray, a planetary scientist at Britain’s
Open University, speculates that the object could be a planet larger than
Jupiter, the biggest of the solar system’s known planets. Murray puts the
object’s orbit at 32,000 AU, or 2.98 trillion miles from the sun. His
proposal appears in the Oct. 11 issue of the Monthly Notices of the Royal
Meanwhile, researchers at the University of Louisiana at Lafayette say the
object could be a planet or brown dwarf — that is, a dark, failed star —
roughly three times the size of Jupiter and orbiting at 25,000 AU. The
researchers, led by physicist John Matese, say their paper is to be
published by the journal Icarus.
Both studies acknowledge that other factors could influence the pattern seen
in long-period comets: for example, the Milky Way’s gravitational tidal
effects. But the Louisiana researchers say the cometary patterns are best
explained by the existence of “a perturber, acting in concert with the
Matese said the proposed object should make one orbit around the sun every 4
million to 5 million years. Murray said the object he had in mind would make
one orbit every 6 million years, circling the sun in a direction counter to
that followed by the nine traditional planets.
The two researchers said they were familiar with each other’s work but
hadn’t taken a close look at each other’s studies.
They acknowledged that
their estimates for the mass and orbit of a mysterious object were similar,
but couldn’t say whether they were talking about the same object.
How could such a massive object exist so far from the sun? The researchers
say a planet or dark star could have coalesced during the formation of the
solar system billions of years ago, but more probably would be a passing
celestial body that was captured by the sun’s subtle gravitational pull.
Another question: Why hasn’t such an object been seen? Murray says that even
a Jupiter-scale planet could not be observed at the immense distances
involved. Matese and his colleagues say that their hypothetical brown dwarf
wouldn’t have been detected even by the Infrared Astronomical Satellite,
which surveyed the heavens in 1983 — but that the yet-to-be-launched Space
Infrared Telescope Facility just might be able to pick it up.
All this may sound like science fiction, but an expert in the field notes
that the hypothesis has been a subject of serious speculation for years.
“We’ve all wondered whether there was something out there,” said
Brian Marsden, who heads the International Astronomical Union’s Central Bureau for
Astronomical Telegrams as well as the Minor Planet Center at the Smithsonian
However, Marsden also expressed some skepticism about the evidence behind
the latest research.
“I’m not convinced it is not due to chance,” he told
MSNBC in an e-mail
message. “In any case, the data may not be as good as one would like.”
If the research holds up, it could open the door for renewed speculation on
even spookier questions: Some theorists have proposed that the gravitational
effect of a massive unseen object in a distant orbit — nicknamed “Nemesis” or the “Death Star” — could set off periodic cometary storms, which would
increase the chances of a catastrophic impact with Earth. Indeed, physicist
Daniel Whitmire, a colleague of Matese’s who is a co-author of the new
research, laid out just such a scenario in 1985 to explain mass extinctions
on Earth, such as the demise of the dinosaurs.
Matese also speculated back then about such an effect, but he emphasized
that the newly detected object didn’t fit the doomsday profile.
“This object is not a Nemesis,” he told MSNBC. “It does not create comet
He said his proposed object appeared to have an influence on about 25
percent of the long-period comets coming in from the Oort Cloud.
Matese noted that theories proposing a correlation between extinctions on
Earth and celestial orbits had fallen out of scientific favor in recent
years. But he said there could be a “much more gentle” effect that links
periodic changes in cratering to the solar system’s oscillating motion
through the galactic plane.
As the solar system moves around the Milky Way’s center, it bobs slowly up
and down through the galactic disk, Matese explained. The gravitational
effects could cause changes in the number of comets sent into the inner
solar system, he said.
“We don’t know the precise period of that motion” through the plane of the
galaxy, he said. “If we discover that it’s closer to a 35-million-year
period, then a case can be made that it causes periodic changes in