Astronomy – September 2019

8 ASTRONOMY • SEPTEMBER 2019

ASTRO LETTERS

Debunking COSTAR

It was with great interest that I read Jeff Hester’s col-

umn in the May issue regarding the overhyped role of

COSTAR in saving the Hubble Space Telescope from

eternal scorn and ridicule. The NOVA episode mentioned

in his column certainly did imply that COSTAR was

almost single-handedly responsible for saving Hubble.

While COSTAR did play an important role, and Jeff does

give some credit to it, COSTAR was completely removed

from Hubble in the final shuttle servicing mission in

2009. All optical corrections have since been done by
      other equipment, making COSTAR obsolete and putting
      its contributions to science since 2009 at about zero.
      Regardless, I think most people can agree that Hubble
      has truly become, through the efforts of many different
      individuals, one of the most valuable instruments ever
      created for the advancement of science and astronomy.
      Good luck, James Webb, but you’ve got a tough act to
      follow. — Dave Vavak, Nevada City, CA

Asteroid or alien?

‘Oumuamua is back in the news and still a mystery,

according to Bob Berman’s column in the May issue.

Bob reports that it unexplainably picked up speed as it

rounded the Sun and headed out of the solar system to

parts unknown. This reminds me of Arthur C. Clarke’s

book Rendezvous With Rama. Clarke’s uncanny tale,

about an alien ship mistaken for an asteroid, could be

unfolding before our eyes! — Dmitri Tumin, Andover, NJ

Molecule mistakes

I found “Where did Earth's water come from?” in the

May issue to be extremely fascinating and informative. I

did notice a minor error in the diagram of the structures

of water and deuterium oxide (page 25) which did NOT

detract from the high quality of the article. Each mol-

ecule is missing two electrons. The diagram shows single

electrons at the interfaces of the hydrogen (or deute-

rium) and oxygen atoms; in reality, it should have shown

pairs of electrons at these locations (forming covalent

bonds). — Peter Conigliaro, Greendale, WI

From the editors: You’re correct, Peter — there were

two electrons each missing from our diagrams of D 2 O

and H 2 O. Our apologies for the error, and thanks for

catching that!

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