Sky & Telescope - September 2023 - 7

Another advance comes via NASA's
Lunar Reconnaissance Orbiter (LRO).
The LRO has been imaging the lunar
surface for over a decade, and by
comparing images over time, scientists
have detected more than 220 new
impact craters.
Shawn Dilles
Editor of the Journal of the ALPO
Vienna, Virginia
Earth Cam
Seeing Earth from space is one of the
great perspective-shifting marvels
of our age, so I endorse Gary Deatsman's
proposal in " Lunar Live Feed "
(S&T: May 2023, p. 7) to install a
high-resolution, continuous-feed video
camera on the lunar surface that's
permanently directed at our planet.
As Deatsman suggests, the feed would
capture fascinating images of Earth
going through different phases and the
planet's Sun-ringed fall of darkness
during lunar eclipses.
Yet another new vision of our place
in the cosmos. Let's do it!
Ken Kalfus
Philadelphia, Pennsylvania
Embracing the Night
Regarding Howard Banich's " Darkness
Audible " (S&T: June 2023, p. 84),
I would like to share the following
quote from Sarah Williams' " The Old
Astronomer " with him:
Though my soul may set in darkness,
it will rise in perfect light;
I have loved the stars too truly to be
fearful of the night.
Bob Anderson
Green Bank, West Virginia
I absolutely identify with Howard Banich's
nighttime paranoia in " Darkness
Audible " in S&T's June issue. The dark
skies of Nebraska, where I live, offer
abundant opportunities for observation.
But every time this city girl participates
in a club gathering or attends
the Nebraska Star Party, I imagine all
sorts of creepy crawlers encroaching
onto the telescope pad. Nevertheless,
the drive to seek out deep-sky objects,
solar system gems, and aurorae lessens
my anxiety of nighttime intruders
enough for me to relish the sights.
Howard Banich's personal account
reminded me that I'm not alone!
Sharon McLean
Omaha, Nebraska
The art department usually plays a
supporting role in Sky & Telescope. But
Leah Tiscione's evocative cartoon about
fearing the dark on the last page of the
June edition stole the issue. Bravo!
Alan Whitman
Okanagan Falls, Canada
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75, 50 & 25 YEARS AGO by Roger W. Sinnott
1948
1973
º September 1948
Shooting Comets " Dr. Fred L.
Whipple, Harvard College Observatory,
prefers to associate generically
all or nearly all of the brighter
visual meteors, and those bright
enough to be photographed, with
comets rather than with meteorites
and asteroids. [He reports] that the
orbits of 45 photographic meteors
have been determined with considerable
precision by Harvard's twostation
rotating-shutter method. . . .
" He believes that bright meteors
1998
are the debris of comets rather than
that they are simply small meteorites
or asteroids. His preference is
based upon many cases of obvious
association; similarities in orbital
characteristics among sporadic
meteors, shower meteors, and
short-period comets; the fact that
meteorite falls suggest little or no
shower association; and the selective
elimination of small asteroidal
particles as time passes. "
º September 1973
Gamma Rays " Short, powerful
bursts of gamma radiation originating
outside the solar system are
reported by three scientists at the
Los Alamos Scientific Laboratory in
New Mexico. Approximately 20 of
these events have been recorded
since July, 1969. . . .
" Ray Klebesadel, Ian Strong,
and Roy Olson made this discovery
while analyzing data from the
four most recent Vela satellites,
which . . . act as 'watchdogs' over
the limited nuclear test-ban treaty
signed in 1963. [Normally] all four
of them 'see' each burst of gamma
rays. As the blast, traveling at
the speed of light, passes each
satellite, the time is recorded to an
accuracy of about 0.05 second.
From the differences between the
arrival times . . . it is possible to
deduce the direction from which a
given burst has come. In this way
it has been found that the radiation
does not come from the earth,
moon, sun, or other planets. "
What astronomers didn't know
then is that all known gamma-ray
bursts have originated outside our
galaxy. Sometimes they signal the
collision of two neutron stars and in
other cases a supernova explosion.
º September 1998
Gravity Boost " You might think
a 10-meter telescope would be
big enough for the routine task of
obtaining a star's spectrum. But
when that star is a 19th-magnitude
mote, every photon counts. That's
why Dante Minniti (Lawrence
Livermore National Laboratory) and
four colleagues are lucky that an
otherwise unseen object happened
to skirt their sightline to [a] mainsequence
star in our Milky Way's
bulge. [The] interloper's gravity
focused the bulge star's light, nearly
tripling its intensity as seen on
Earth. This temporarily turned the
Keck I reflector into the equivalent of
a 16-meter telescope, enabling the
team to measure the star's lithium
content - an important chemical
clue to our galaxy's history. "
sk yand tele scope .o r g * SEPTEMBER 2023
7

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Sky & Telescope - September 2023

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