Sky & Telescope's News Bulletin - Sep 12

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* * * SKY & TELESCOPE's WEEKLY NEWS BULLETIN - September 12, 2003 * * *

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Welcome to S&T's Weekly News Bulletin. Images, the full text of stories
abridged here, and other enhancements are available on our Web site,
SkyandTelescope.com, at the URLs provided below. (If the links don't work, just
manually type the URLs into your Web browser.) Clear skies!

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BLACK HOLE "SOUND" HEATS A GALAXY CLUSTER

The supermassive black hole at the heart of the Perseus A galaxy cluster is
singing a note with a voice as powerful as hundreds of million of supernovae,
astronomers declared this week at a NASA press conference. This announcement
made the news media sit up and take notice ("Black Hole Hums Deepest Note Ever
Detected," headlined CNN), but the description was a stretch; it would take a
very broad-minded physicist to consider the effect anything like a musical
tone. It may, however, solve a longstanding galaxy-cluster mystery....

http://SkyandTelescope.com/news/article_1046_1.asp

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NEPTUNE'S STOWAWAY

Neptune, it seems, likes harboring stowaways. Astronomers already knew that its
largest satellite, Triton, didn't form along with the planet's other moons. It
now appears that another body, Nereid, also jumped onboard.

Nereid has perplexed scientists since its discovery in 1949. The moon's highly
eccentric (non circular) orbit is inclined some 28 degree with respect to
Neptune's equatorial plane. Early this month at the American Astronomical
Society's Division of Planetary Sciences meeting in Monterey, California,
Anthony R. Dobrovolskis (NASA/Ames Research Center) showed evidence explaining
how Neptune's third largest moon got to be that way....

http://SkyandTelescope.com/news/article_1044_1.asp

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ASTRO NEWS BRIEFS

Halley's Comet Spotted

Most skywatchers lost interest in Halley's Comet soon after it swung through
the inner solar system in 1986, and professionals last sighted its bare nucleus
outside Saturn's orbit in 1994. But a team of European astronomers recently
tracked down Halley at a distance of 28.06 astronomical units from the Sun,
nearly at the distance of Neptune. Last March Olivier Hainaut (European
Southern Observatory) and several colleagues simultaneously used three of the
four 8.2-meter Very Large Telescope reflectors in Chile to image the comet's
predicted field near the head of Hydra. No trace of the nucleus was visible on
any single exposure. But when the astronomers stacked all 81 exposures
(totaling 9 hours) with offsets to keep Halley's predicted position fixed, the
comet barely emerged into definite view at magnitudfe 28.2. Hainaut believes
these exposures would have been good enough to record Halley even at its
aphelion distance of 35.3 a.u., its turnaround point farthest from the Sun,
which it will reach in 2023.

Mirror Chosen for Webb Telescope

It's been one year since NASA selected California-based TRW to build the James
Webb Space Telescope (JWST). And this week Northrop Grumman, which acquired TRW
in late 2002, announced that it will fabricate the JSWT's 6.5-meter primary
mirror out of beryllium, a strong but lightweight metal. A panel of industry
specialists opted for beryllium over the other candidate material,
ultralow-expansion glass, because it offered the better combination of low
mass, high stiffness, and the ability to withstand the extremes of outer space.
Production of the mirror's 18 hexagon-shaped segments will begin next year.
With its launch planned for 2011, JWST will ultimately replace the aging Hubble
Space Telescope. However, whether the two missions will overlap awaits a
decision by NASA officials. The Webb telescope will operate from the L2
Lagrangian point, a gravitationally stable location about 1.5 million
kilometers away on the anti-sunward side of Earth.

A New Moon for Neptune

The outer solar system just got a little more crowded, as astronomers have
discovered another small moon circling Neptune. The new find, designated S/2003
N1, travels in a distant and highly irregular orbit that averages nearly 50
million miles from the planet and takes 26.3 years to complete one revolution.
Observers David C. Jewitt, Jan Kleyna, and Scott S. Sheppard identified the
tiny object, about 40 kilometers across, as a 26th-magnitude blip in images
acquired on August 29th with the giant Subaru telescope atop Mauna Kea, Hawaii.
Based on orbital calculations by Brian G. Marsden (Minor Planet Center), its
motion was matched to that of an object first seen in August 2001 and two times
thereafter. S/2003 N1 is Neptune's 12th satellite.

Uranus's Lost-and-Found Moonlet

In 1999, while inspecting 13-year-old images taken of Uranus by Voyager 2,
planetary specialist Erich Karkoschka (University of Arizona) spotted a tiny
moonlet circling about 50,000 kilometers above the blue-hued planet. But
because it was so faint and small, no more than 40 km across, his find could
not be confirmed by telescopes back on Earth. Consequently, two years ago the
International Astronomical Union decided to remove S/1986 U10 from its official
list of Uranian satellites. But thanks to observations made August 25th using
the Hubble Space Telescope's new Advanced Camera for Surveys, Karkoschka's
claim has been verified. Mark R. Showwalter (Stanford University) and Jack J.
Lissauer (NASA/Ames Research Center) found the 24th-magnitude object about 48
degrees ahead of its predicted position. S/1986 U10 circles Uranus every 15.3
hours and is the planet's 22nd known moon.

http://SkyandTelescope.com/news/article_1045_1.asp

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HIGHLIGHTS OF THIS WEEK'S SKY

* Last-quarter Moon on September 18th.
* Mars blazes in the southeast to south during evening this week.
* By the end of this week, you may be able to spot Mercury just above the
eastern horizon about 40 minutes before sunrise, below brighter Jupiter.

For details, see This Week's Sky at a Glance and Planet Roundup:

http://SkyandTelescope.com/observing/ataglance/

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Copyright 2003 Sky Publishing Corp. S&T's Weekly News Bulletin is provided as a
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| Stuart Goldman |
* Associate Editor *
| Sky & Telescope |
* 49 Bay State Rd. Sky & Telescope: The Essential *
| Cambridge, MA 02138 Magazine of Astronomy |
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