Sky & Telescope - December 2018 - 21

in space and on the ground, have the potential to answer
these questions."

N ASA / ESA / HUBBLE HERITAG E TE A M (STSCI / AUR A) /
ESA HUBBLE COLL A BOR ATION

Solar System Science
While the study of other planetary systems remains a challenge, even for 30-meter-class telescopes, our own solar
system presents many opportunities for new discoveries with
the next generation of astronomical instruments. Obviously,
ground-based telescopes will never be able to compete with
spacecraft visiting other worlds, but except for NASA's Juno
orbiter at Jupiter, at present there are no planetary explorers
observing the giant planets at close range. With their unprecedented resolution - thanks to adaptive optics - the giant
telescopes of the future will be able to regularly observe cloud
patterns in the atmospheres of Uranus and Neptune, study
the seasonal cycles of Saturn's giant moon Titan, and monitor
volcanic activity on Jupiter's Io, which will measure hundreds
of pixels across in the upcoming cameras.
Because of their huge light-gathering power, the megascopes will also be able to spectroscopically study the surface
composition of countless faint asteroids and Kuiper Belt
objects and even detect thousands of small outer solar system
bodies, out to distances beyond 5 billion kilometers (about
30 astronomical units). Thus, astronomers will gain detailed
insight into the dynamical history of our own solar system,
which, in turn, will help us understand the formation and
evolution of planetary systems in general. Most likely, the
GMT, TMT, and ELT will carry out many follow-up observations on small bodies discovered by the future Large Synoptic
Survey Telescope, which will scan the heavens twice a week
(S&T: Sept. 2016, p. 14).
Finally, the giant telescopes will study transient phenomena like novae and supernovae, tidal disruption events created when supermassive black holes tear apart stars in other
galaxies, gamma-ray burst afterglows, and, hopefully, the
optical and near-infrared counterparts of gravitational-wave
detections and the still-mysterious fast radio bursts (S&T: July
2016, p. 24). "We're designing the TMT's WFOS instrument
in such a way that rapid follow-up observations will be possible," says Bundy.
It's impossible to do full justice to the scientiﬁc potential
of the monster scopes of the future in just one magazine
article, and many exciting research areas haven't been mentioned here. But from this superﬁcial overview, it will become
clear that there's no lack of astronomical topics to explore.
And these are just the known unknowns: As has always been
the case, completely unexpected discoveries may well turn
out to await us. As Szentgyorgyi says: "That's what makes it
science, as opposed to engineering." Little wonder that the
astronomical community can't wait for the new telescopes to
achieve ﬁrst light.
So assuming that all three of the megascopes will indeed
be built according to the current speciﬁcations, which one
will yield the most revolutionary results? That's hard to say.
The Giant Magellan Telescope will probably be the ﬁrst one

to be completed, in early 2024 (albeit with only a subset of its
seven mirrors, as described in last month's issue), so it may
well pick some exciting low-hanging fruit. The Extremely
Large Telescope (2024) has the obvious advantage of being the
largest by far, and it's also the only one with a true mid-infrared imager/spectrometer (METIS) among its ﬁrst-light instruments. The Thirty Meter Telescope will come last (2028), but
it has the best near-ultraviolet wavelength coverage, and as
the only Northern Hemisphere project it will have at least
part of the celestial sky to itself. Moreover, the TMT may
proﬁt from the experience gained by the GMT and the ELT.
While universities, institutes, and industries all over the
world are preparing for the construction of the ﬁrst-light
instruments for the three giant telescopes, scientists and
engineers are already thinking about a second generation of
cameras and spectrographs. As for the distant future, some
astronomers are dreaming about a 15- to 20-meter space-

p STAR FORMATION The star-forming region LH 95 in the Large Magellanic Cloud, in visible and infrared light. The bluish nebula is made of
hydrogen that's been ionized by the winds and radiation from the region's
massive stars.

based observatory, covering the ultraviolet, visible, and infrared parts of the electromagnetic spectrum.
Surprisingly, almost no one is making a strong case
for yet another aperture leap in ground-based astronomy.
Does that mean that, with the future extremely large telescopes, we may really have reached the limits of what can
be achieved in optical and near-infrared astronomy from
Earth's surface? Perhaps. Then again, we thought the same
thing half a century ago. It is difﬁcult to make predictions,
especially about the future.

¢ S&T Contributing Editor GOVERT SCHILLING lives in the
Netherlands, where the very first telescopes were built just
over four centuries ago. He can't wait to visit the Extremely
Large Telescope in Chile after its completion in 2024.
sk yandtelescope.com * DECE MBE R 2 018

http://www.skyandtelescope.com

Sky & Telescope - December 2018

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