WWW.ASTRONOMY.COM 49and big cities. These lights confine them-
selves to a small band of the electromag-
netic spectrum that astronomers easily can
remove. In contrast, LEDs leave a large
footprint across the spectrum. The now
common blue bulbs are the worst offender.
Their light falls in what University of
Hawaii astronomer Richard Wainscoat
calls the “nightmare spectrum.”
In lighting, color temperatures above
5,000 kelvin are considered “cool colors,”
like blue. “Warm colors” such as yellow fall
around 3,000 K. Cities are turning to
LEDs because of the large poten-
tial cost savings; how-
ever, the average
5,000 K street-
light emits a
large amount of
light in the band-
width around 450
nanometers, where astronomers com-
monly observe. The light might not be
an affront to the eye in an already well-lit
area, but for the sensitive CCD cameras
used by astronomers around the world,
it’s blinding.
“The blue light really has to be sup-
pressed; otherwise our view of the night in
the future is going to be suppressed,”
Wa i nscoat s ay s.
Like other communities around the
world, Hawaiian cities are converting to
LEDs. On the Hawaiian island of Maui,
Wainscoat is worried new city lights might
jeopardize the dark skies needed by the
instrument he heads, Pan-STARRS.
The wide-angle telescope has the
world’s largest CCD camera and rapidly
scans the entire visible sky in search of
asteroids and comets in Earth’s vicinity.
A recent record-breaking night netted 19
asteroids — two that approach our orbit
— in one run.
And, like Chile, it’s not just science
at risk. An economic impact study by the
University of Hawaii estimated that about
$168 million was spent on astronomy in the
islands in 2012, creating some 1,400 jobs.Laws not enforced
Hope lies across the water on
Hawaii’s Big Island, home to
the world-famous dark skies
of Mauna Kea, where officials
plan to update their lighting
ordinance this year. New LED street-
lights there have filters that remove the
blue light. Full-cutoff light shields make
sure the light points at the ground instead
of up and out, which spreads light pollu-
tion. Warmer amber-filtered LEDs would
be better for astronomy, but the technology
is still far too expensive.
“On the positive side, retrofits with
LEDs present the opportunity to replace
poorly shielded lights with fully shielded
lights,” Wainscoat says. “Anyone with any
interest in astronomy should stay very vig-
ilant about this — to make sure that only
fully shielded LEDs are installed.”
That’s not happening now outside the
public sector. “Enforcement of the ordi-
nance is quite lax,” Wainscoat says.“A Jack In The Box [restaurant] on the Big
Island is treated like a Jack In The Box
anywhere else.”
The problem is worse away from the
major dark-sky sites, where relatively few
residents are pushing cities to shield new
LEDs and cities aren’t enforcing existing
laws. Even many astronomers are not yet
on the bandwagon. At the most recent
American Astronomical Society meeting in
Seattle — the so-called “Super Bowl of
astronomy” — a session on light pollution
drew mostly empty chairs.
Daniel Caton, director of observatories
at Appalachian State University in North
Carolina, told those in attendance that he’s
generally disappointed at the lack of protest
by astronomers in their hometowns.
“It’s fine to go off to Mauna Kea or
Cerro Tololo, but when you get home,
you have to live with it,” Caton says.
“Eventually, these orange bubbles of
sodium vapor light are going to overlap.”A white-light night
In 2010, German researchers found that
light pollution’s global reach is expanding
by 6 percent each year with understudied
but very real impacts on biology. Some 30
percent of vertebrates are nocturnal, and
that number doubles for invertebrates.
Ecologists worry about species like moths
and bats — nighttime pollinators that
many plants depend on.
Other scientists think entire ecosys-
tems could be at risk. Recent studies with
light traps in New Zealand found insectsNew York City, once at the forefront of electricity,
is again playing a leading role adopting LEDs. NASA
Light pollution spreads out below Mauna Kea on the Big Island of Hawaii, which will soon be home to
the more than $1 billion Thirty Meter Telescope. ANDREW COOPER/W. M. KECK OBSERVATORY