O
The wild and woolly
menagerie of ghost worlds
that once haunted the halls of
astronomical history. by John Wenz
Phantom
planets
Phantom
planets
ur galaxy is lousy with planets. NASA’s
exoplanet archive lists more than
3,400 confirmed planets outside
our solar system, with more added
every day. Nearly 4,500 planetary
candidates from NASA’s Kepler
spacecraft await confirmation, mean-
ing thousands more could make the list
in the near future.
Before 1995, there were only 11 known planets.
There were the nine classical planets in our solar sys-
tem, from Mercury through Pluto (then still a planet),
and two bizarre objects that had been found around
a distant pulsar.
But in 1995, we discovered 51 Pegasi b, the first
confirmed planet around a Sun-like star. It was a
weird one. It circled its star every four days and was
eight times more massive than Jupiter. At the time, it
received a lukewarm reception.
“In 1995, 51 Pegasi b was found, and about 50
percent of the astronomers or fewer believed it was
an exoplanet,” says Debra Fischer, a professor ofastronomy at Yale University.
Why did it take so long to find a world circling
another star in the first place?
“You have to picture the size and the mass of the
star and then a little planet like the Earth. And if you
set them side by side, Earth has a diameter that’s
1/100th the size of the Sun and [a fraction of] the
mass,” Fischer says. Thus, astronomers can’t directly
see exoplanets, as even at “the edge of [their] solar
system, [they] are drowned out by the light of the
star.” To find planets, astronomers must employ
other methods, many of which have only just come
into their own.
With that in mind, it was a long road to get to
51 Pegasi b. The right technology had to reach matu-
rity at the right time. But it wasn’t the first planetary
claim. In fact, the history of claims of planets outside
our solar system stretches back more than a century
and involves outsized personalities, outright fraud-
sters, befuddled scientists, brown dwarfs, numerous
retractions, bitter back-and-forths, and more.
Here are the tales of the planets that never were.