Page 11 - Astronomy - October 2017 USA

ASTROLETTERS The best $299

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M16 Eagle Nebula
Fourth time’s the charm think there are a trillion galaxies, leav-
8” Celestron Evolution
There’s one astronomy event I latched ing the reader to think that we don’t need Metropolitan Skies
onto when I got my 58x telescope in the dark matter because there is much more
spring of 1980. About every 15 years, regular matter out there than we thought. REVOLUTION IMAGER
Earth’s viewpoint crosses Saturn’s Conselice is careful to point out that
RevolutionImager.com
rings, and they appear edge-on, or even the number of galaxies is greater than
disappear. we thought, but that the early ones were
Oceanside Photo & Telescope
I am 65 now and have seen this three small and numerous and the total mass
Woodland Hills Telescope
times in a row. The second time was remains the same. His explanation of why
High Point Scientific
January 25, 1996, using the same tele- the sky looks dark to us between galaxies
Agena AstroProducts
scope. That time, the rings appeared as a is concise and easily understood. Skies Unlimited
thin, misty line. Anyway, thanks for this article. I found Camera Concepts & Telescope
The third time was April 4, 2009, at a it both clear and fun as the author also
public gathering on the grounds of the injects a bit of humor here and there. That
U.S. Naval Observatory. On that occasion, is why I also enjoy Bob Berman’s writing
the rings looked like a thick, bright line. so much. — Robert Walty, Stephens City, VA
I recently emailed Geoff Chester at the
observatory and he said the next Earth
crossing will be March 23, 2025, when I A perfect ellipse
will be 73. Four times in a row — it beats Just a quick response to Bob Berman’s
waiting for Halley’s Comet. “A perfect circle” article in the May 2017
— John Lockwood, Washington, DC issue. The universe prefers ellipses. Most
planets are “squished” due to their rota-
tion. Also, most orbits of planets and
The concise explanation moons are ellipses. Sorry, but the universe
I wanted you to know how much I is happy with imperfect circles, aka ellips-
enjoyed the article “Our trillion-galaxy es! — Douglas Kaupa, Council Bluffs, IA
universe” in the June issue. Christopher
Conselice is a very good writer who puts Bob Berman responds
important ideas across to us armchair Hey Douglas, maybe you were excessively
astronomers clearly. Sometimes articles speed-reading my column because your
in Astronomy have cloudy spots in them letter oddly says, “Sorry, but” followed by a
where the writer seems to know the “correction” that essentially says the same
issue but does not give us, the reader, things I wrote!
quite enough information to understand My article said: “Reality ultimately
fully. Some writers might say we now intruded. As it turned out, only Venus’
orbit would look circular to an alien study-
We welcome your comments at ing it from a distance, with other planets
Astronomy Letters, P. O. Box 1612, displaying varying degrees of elliptical
Waukesha, WI 53187; or email to letters@ shapes. And fair enough: Ellipses rule . . . ”
astronomy.com. Please include your Indeed, your letter says that “most plan-
name, city, state, and country. Letters ets and moons” have elliptical orbits.
may be edited for space and clarity. In fact, all of them do. — Bob Berman,
contributing editor

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