Sky and Telescope - October 2015 - 4

Peter Tyson
Spectrum
Founded in 1941
by Charles A. Federer, Jr.
and Helen Spence Federer

The Essential Guide
to Astronomy

A Super Hubble

Hed.GillSans.30

In early July, a group of astronomers released a report championing
a single bold idea. It's a proposal that, in my opinion, ranks up there with
President Kennedy's 1961 challenge to put a man on the Moon "before the
decade is out."
The notion is to build a space telescope so big, so sensitive, and so technologically advanced that it might enable astronomers to answer some of
the grandest questions we've ever asked: Are we alone? Do Earth-like planets with breathable air exist elsewhere? Are they, in fact, common? How did
life emerge in the cosmos in the ﬁrst place?
The group that wrote the report knows whereof it speaks. It is the Association of Universities for Research in Astronomy, or AURA. A consortium
of 40 U.S. institutions and four international aﬃ liates, AURA, among
many other things, conducts science
operations for the Hubble Space
Telescope (HST) and for the upcoming James Webb Space Telescope.
In short, AURA's study calls for
a High Deﬁnition Space Telescope,
a sort of "super Hubble." With
its 12-meter (39-foot) segmented
primary mirror, the HDST would
be 100 times more sensitive to faint
Hubble JWST
HDST
light than HST is and provide views
2.4m
6.5m
11.7m
ﬁve times as sharp. You can downHow the primary mirror of the HDST stacks
load the AURA report here: hdstviup against those of Hubble and James Webb
sion.org/report.
C. GODFREY (STSCI)
Parked a million miles from Earth
in a gravitationally stable location, the HDST would also have devices - a
coronagraph and perhaps also a star shade - that would so eﬀectively block
a star's blinding glare as to allow astronomers to directly image exoplanets
orbiting that star. (See page 16 for our story on where such direct imaging of
extrasolar planets stands today.)
More importantly, such a telescope could, in principle, characterize the
atmospheres of nearby exoplanets. Detecting an abundance of water vapor,
oxygen, methane, and other organic compounds sheathing an exoplanet
might very well signal an active biosphere on its surface.
I think the HDST idea merits serious consideration. The hurdles are
many and huge: For this project to reach fruition would take decades of
painstaking eﬀort, the development or perfection of entirely new technologies, sustained political will, and many billions of dollars.
But just imagine knowing, with a high degree of certainty, that another
Earth exists out there, perhaps with beings as or more intelligent than we
are. What would that understanding do to our worldview? To our sense of
self as human beings? To our hubris? ✦

EDITORIAL

Editor in Chief Peter Tyson
Senior Editors J. Kelly Beatty, Alan M. MacRobert
Equipment Editor Sean Walker
Science Editor Camille M. Carlisle
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Observing Editor Susan N. Johnson-Roehr
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Contributing Editors Jim Bell, Trudy Bell, John E. Bortle, Greg Bryant,
Thomas A. Dobbins, Alan Dyer, Tom Field, Tony Flanders, Ted Forte, Sue
French, Steve Gottlieb, David Grinspoon, Ken Hewitt-White, Johnny Horne,
Emily Lakdawalla, Jerry Lodriguss, Rod Mollise, Donald W. Olson, Joe Rao,
Dean Regas, Fred Schaaf, Govert Schilling, Gary Seronik, William Sheehan,
Mike Simmons, Alan Whitman, Charles A. Wood, Robert Zimmerman
Contributing Photographers P. K. Chen, Akira Fujii, Robert Gendler,
Babak Tafreshi
ART & DESIGN

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Editor
d
in Chief
h f
4

October 2015 sky & telescope

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Sky and Telescope - October 2015

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