2019-05-01_Discover

72 DISCOVERMAGAZINE.COM

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so large, in B) such a comparatively close orbit that
was C) extremely lopsided, raised serious doubts —
especially given the high-profile exoplanet retractions
in the past. Ultimately, the trio decided to classify the
world as a brown dwarf rather than a planet,
though the paper noted it could be either.
“It had three strikes against it,” says
Latham. “Three strikes and you’re out.”

SECOND CHANCE TO BE FIRST
But times have changed. Now that we’ve
found nearly 4,000 exoplanets and count-
ing, astronomers no longer consider close-
orbiting gas giants unusual. And it turns out
our solar system is itself a bit of an outlier,
since its circular orbits are fairly rare. That
negates two of the three strikes the team had
against classifying HD 114762b as an exo-
planet, leaving only the third: its uncertain
(but too big for most planets) mass.
That’s where the European Space
Agency’s Gaia observatory could help.
The orbiting spacecraft has made extremely precise
measurements of the motion of over a billion stars
since launching in 2013. It scans the entire sky every
six months, so by the end of its mission this year, it
will have studied — briefly — each of those billion
stars 70 to 80 times.

In its next data release, scheduled for mid-2021,

Gaia should reveal the precise motion of the

star HD 114762. That knowledge would finally

allow researchers to measure a precise mass for

HD 114762b and determine its true nature.

Latham and his crew are confident in the outcome.

Many astronomers already recognize HD 114762b

as a planet rather than a brown dwarf, based on its

estimated mass from the original paper and its likely

formation. It’s even already listed in NASA’s official

exoplanet catalog, and many astronomers have unof-

ficially named the world “Latham’s planet.”

Though the scientific community has opened its

arms to the idea that this is a true exoplanet, they still

need the hard evidence. After all, should it turn out

HD 114762b was the first detected exoplanet, it would

dethrone the pulsar planets as No. 1 — the history

books, and our outlooks, would need updating.

Beyond that, though, Latham just wants Gaia’s

solid measurements. He and Mazeh are looking

forward to putting the issue to rest in 2021, even if it

takes a bit more patience.

“I’ve waited [over 30] years,” Latham says. “I can

wait another few.”^ D

Nola Taylor Redd is a freelance science journalist

with a focus on space and astronomy. Find her or

on Twitter: @NolaTRedd

OUT THERE

David Latham

co-discovered

HD 114762b,

possibly the first

known exoplanet.

The Gaia satellite

maps the stars

in the Milky Way

precisely enough

to finally determine

the truth about

HD 114762b.