sible signatures of biological activity, such as carbon dioxide
and ozone, or oxygen in combination with methane. Though
not a biomarker in itself, water would also be required for a
planet to support life — as least as it is known on Earth, notes
Lisa Kaltenegger of Harvard-Smithsonian.
A mission capable of detecting these chemical fingerprints
in a planet’s atmosphere wouldn’t be ready for launch for
another decade. Such a mission might also manage to take a
blurry picture of an Earthlike planet by using advanced techniques to blot out the blinding light from the parent star.
An exoplanet task force that included Boss and Lunine
recently noted, however, that there could be a shortcut to
looking for habitable exoplanets. Instead of looking for
Earth-mass planets orbiting sunlike stars, scientists could
focus on superEarths — planets five to 10 times as massive
as Earth — orbiting light weight, cooler stars called M dwarfs.
Because M dwarfs aren’t as hot as sunlike stars, the habitable zone lies relatively closer to these low-mass stars. That
makes a habitable planet easier to detect. And it’s more likely
that such a close-in planet will pass in front of its star as seen
from Earth, allowing the starlight to filter through the distant planet’s atmosphere and reveal whether the composition
might be compatible with life. The James Webb Space Telescope, scheduled for launch in 2013, could examine superEarths, determining which might be the best candidates for
the search for extraterrestrial life.
The universe has no dearth of oddball objects. But the
JWST and a slew of other powerful telescopes now in the
planning stages are likely to reveal even more exotic beasts
that the cosmos has kept under wraps.
Astronomers have long known about neutron stars, the
ultracompact cinders left behind by supernovas. These cin-
ders are so dense that they squeeze electrons and protons
into giant balls of neutrons. And for more than two centuries
researchers have theorized about black holes, which capture
all matter and light that enter them.
But even stranger stuff may exist. For instance, particularly
massive neutron stars may squeeze neutrons so tightly that
they break down into quarks. By measuring the size and radius
of neutron stars, researchers are attempting to find evidence
for such “strange stars” or “quark stars.”
Another novel space oddity would be a wormhole — a black
hole’s distant cousin. In 1935, Einstein and Nathan Rosen realized that general relativity allows such tunnels, which would
directly connect two vastly distant regions of spacetime, or
even locales in different universes.
Theorists once believed that these proposed portals could
exist only for a fraction of a second. But calculations suggest
that “exotic matter” — material endowed with a special property called negative energy — could prop a wormhole open
“There are mathematical solutions, but whether or not they
correspond to something in reality remains to be seen,” says
cosmologist Michael Turner of the University of Chicago.
Perhaps the strangest notion about the cosmos is that the
observed universe is only one among many other universes,
each residing in a pocket disconnected from the others.
Inflation — the early epoch of rapid expansion — could allow
for an infinity of separate bubble universes. And string theory,
which envisions each elementary particle as a string rather
than a point, also suggests the existence of a vast ensemble of
different universes, each with its own physical laws.
The notion of such a multiverse is the ultimate in the revolution begun by Copernicus nearly five centuries ago, Turner
says. Not only is Earth not the center of the solar system or
the galaxy, but our universe may be just one of many.
Four hundred years from now, says
Turner, inflation may be remembered as
the theory that drastically changed people’s
vie w of the cosmos. “It may be infinitely bigger than we imagined,” he says. Much bigger
than Galileo could have realized when he
first peered at the sky through a crude set
of magnifying lenses in 1609. s
s For several papers highlighting recent
progress and enduring riddles in astrophysics, cosmology and planetary science, see: www7.nationalacademies.
A wormhole, as depicted by an artist in
this illustration, would form a portal into a
remote region of space or perhaps even into