Sky & Telescope News Bulletin - September 12, 2003

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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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