Have scientists found our first exomoon? Looks like they still
need more observations to be a hundred percent sure. The moons
in our solar system are very diverse, some with liquid water,
some that are potentially habitable, so being able to
observe moons in different solar systems would give us a whole
new treasure trove of interesting worlds to study. The
team of astronomers from Columbia University sifted
through data from 284 Kepler measurements of transiting
exoplanets. A transit happens when a planet passes directly
between us and its star and blocks out a small portion of
the star’s light, which produces a dip in the amount of light
coming from that star over time, called a light curve. Out of the
284 planets the team looked at. they found one planet with an
extra wobble in its light curve that might be a moon. The team
only had Kepler data from three transits of this exoplanet, so
they sent a proposal to the Hubble Space Telescope to
capture more data of this possible exomoon. Hubble can
measure light curves much more precisely than Kepler, so Hubble
can more definitively confirm or debunk the existence of this
exomoon once it gets multiple transits. So far, the team of
astronomers has collected Hubble observations of one transit of
exoplanet Kepler-1625b. The planet transited across the face
of its star for 19 hours, as expected. Then, about three and
a half hours later, a second smaller dip in the light curve
started. That right there is intriguing evidence of an
exomoon. The Hubble observation of this star unfortunately
concluded before the possible moon finished its transit, so
Hubble hasn’t yet observed a full transit. This
light curve appears like it shows an exomoon, but we can’t
say it’s a definitive detection until Hubble observes at least
one more transit. If this is actually a moon, what do we know
about it? The planet Kepler-1625b is likely several
times the mass of Jupiter. Its possible moon appears to be
about the mass and radius of Neptune. Neptune-sized moons are
obviously not something that exist in our own solar system,
and we’re not sure exactly how such a moon would form. Finding
planets and moons so different from the ones in our own solar
system gives us a lot more knowledge of the many diverse
ways planetary systems can exist. In the near future,
scientists hope to use the Hubble Space Telescope to try to
confirm the discovery of this exomoon, and they’ll use Hubble
for follow-up observations of other planetary systems
discovered by observatories like Kepler and the recently launched
Transiting Exoplanet Survey Satellite, TESS. So if you like
planets – and honestly, who doesn’t – stay tuned to learn
more about all sorts of fascinating new worlds.
www.nasa.gov/hubble @NASAHubble