Sky & Telescope's News Bulletin - Aug 27

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Date: 28 Aug 2004 03:06:39 GMT

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 * * * SKY & TELESCOPE's WEEKLY NEWS BULLETIN - August 27, 2004 * * *

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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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TINY TELESCOPE FINDS BIG PLANET

Until now, all of the 125 or so known extrasolar planets were discovered with
large telescopes equipped with cutting-edge detectors. But an international
team has identified a planet circling a distant star using mostly off-the-shelf
equipment and a 4-inch Schmidt telescope. In fact, team coleader Timothy Brown
(National Center for Atmospheric Research) assembled the discovery telescope
and fine-tuned its optics in the garage of his Colorado home....

> http://SkyandTelescope.com/news/article_1330_1.asp

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SEDNA'S ORIGIN SOLVED?

Last year astronomers discovered what's probably the biggest body found in the
solar system since Pluto in 1930, and they didn't know what to make of it.
Sedna, as 2003 VB12 was informally named, is about half the size of the Moon
and ranges from 75 to 985 astronomical units from the Sun in a highly
elliptical orbit. Neptune, by comparison, is 30 a.u. from the Sun, Pluto
averages 40 a.u., and the icy objects populating the Kuiper Belt drop off
sharply after 55.

So how did Sedna get way out there? It couldn't have formed in place; the Sun's
protoplanetary disk was too sparse that far out. Now Alessandro Morbidelli
(Cote d'Azur Observatory) and Harold F. Levison (Southwest Research Institute)
have analyzed various theories in detail....

> http://SkyandTelescope.com/news/article_1326_1.asp

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PERSEIDS PEAK AS PREDICTED

This is an exciting time to be a meteor observer. Scientists have long known
that a meteor shower occurs when the Earth passes through the trail of debris
strewn behind a comet as it orbits the Sun, but until a few years ago they
could only guess what would happen during any given shower. Skilled observers
would note unexpected outbursts and lulls, but nobody knew how to use that
data. Now, experts in orbital dynamics have started to analyze the fine
structure of these cometary debris trails and predict fluctuations in meteor
activity with extraordinary accuracy....

Now meteor prediction has scored another success. Esko Lyytinen of Finland and
Tom Van Flandern of Washington, DC, forecast an unusually brief and intense
peak in the 2004 Perseids due to a filament of debris cast off when Comet
Swift-Tuttle swept by the Sun in 1862. They also predicted that the normal peak
of this shower would be stronger than usual due to a 12-year resonance with
Jupiter's orbit.

Preliminary analysis of data from 107 observers in 27 countries by Rainer Arlt
of the International Meteor Organization confirm both of those predictions....

> http://SkyandTelescope.com/observing/objects/meteors/article_1329_1.asp

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ASTRO NEWS BRIEFS

Astronomers Find Lightweight Exoplanet

The European planet-hunting team led by Michel Mayor (Geneva Observatory,
Switzerland) has announced a low-mass planet orbiting the 5th-magnitude
southern star Mu Arae. The planet has a minimum mass of just 14 Earths, almost
identical to the mass of Uranus. It races around the solar-type star every 9.5
days at an average distance of just 0.09 astronomical unit. Because we do not
know the inclination of the planet's orbit, its most likely mass is actually
about 17 or 18 Earths, similar to Neptune. This object is the lightest planet
discovered outside the solar system other than the three terrestrial-mass
bodies orbiting the pulsar B1257+12. Mu Arae also has a previously discovered,
Jupiter-mass planet in a 650-day orbit, and there are strong indications of
another planet even farther out.

Like the vast majority of the 140 or so known extrasolar planets, astronomers
discovered this new object by tracking back-and-forth Doppler shifts in the
star's spectrum induced by the planet's gravitational pull. The detection
method does not reveal whether the planet is a large ball of rock and iron (a
so-called "super-Earth"), a gas giant like Jupiter and Saturn, or a hybrid
Uranus- or Neptune-like world with a massive rock/ice core and a moderate
gaseous envelope. Mayor's group discovered the planet with its new
super-high-resolution HARPS spectrograph on the 3.6-meter European Southern
Observatory telescope at La Silla, Chile.

Space Rock Buzzes Earth

Last March 31st, a small chunk of asteroid hurtled within 6,500 kilometers of
Earth's surface, according to an orbital analysis announced this week. Now
designated 2004 FU162, the object was spotted only hours before its close brush
by the LINEAR survey telescope in New Mexico. Unfortunately, LINEAR recorded
the speeding visitor on only four frames over a 44-minute period. By the time
astronomers were alerted to its existence, the little asteroid had moved into
the daylight sky. Despite these all-too-brief observations, dynamist Steven
Chesley (Jet Propulsion Laboratory) managed to derive a reliable orbit -- and
the near miss -- that was reported August 22nd by the Minor Planet Center in
Cambridge, Massachusetts.

With an estimated diameter of less than 10 meters, 2004 FU162 is small enough
that it would have exploded harmlessly had it collided with Earth's atmosphere.
Alan Harris (Space Science Institute) notes that an asteroidal fragment of this
size should pass just as close to Earth at least once per year. "This event is
not particularly rare," comments impact specialist David Morrison (NASA-Ames
Research Center), "except that LINEAR had the good fortune to notice it."

The closest known near-miss asteroid skimmed within 60 km of Earth on August
10, 1972, creating a dazzling daylight fireball seen along a 1,500-km-long
trajectory over the Rocky Mountains. Its estimated diameter was also about 10
meters.

Mars Odyssey Starts Extended Mission

After 23 months of scrutinizing the red planet's surface and atmosphere from
orbit, NASA's Mars Odyssey orbiter has officially completed its primary
mission. The spacecraft was launched on April 7, 2001, and reached Mars 6
months later on October 23rd. A full Martian year has passed since February
2002, when the orbiter began its scientific studies. In that time the
spacecraft confirmed that Mars has vast reserves of water ice just below its
surface, especially in and around the south pole, and its infrared spectrometer
has compiled a global map of mineral abundances and surface textures. From this
point forward Odyssey will carry out an extended scientific mission, as it
continues to relay 85 percent of the images and other data transmitted by the
twin rovers Spirit and Opportunity.

New Nebula's X-rays

Backyard observer Jay McNeil's discovery of a nebula in January generated much
excitement among amateur astronomers and considerable interest on the part of
professionals. The previously invisible nebula suddenly lit up when the star
embedded within it brightened, probably because of a sharp increase in the
amount of matter falling onto it from its circumstellar disk. Just a few weeks
after McNeil spotted the object in one of his CCD images, Joel H. Kastner
(Rochester Institute of Technology) and his collaborators realized that, by
chance, they had imaged the region with the Chandra X-ray Observatory in 2002,
before the outburst began. They have observed it twice since then, recording a
50-fold increase in the object's X-ray luminosity that mirrors the brightening
in optical and infrared wavelengths. X-ray emission is commonly seen in young
stars, but there is an ongoing debate about what causes it. The fact that this
X-ray outburst is occurring simultaneously with the optical and infrared
eruption demonstrates that in at least some cases, the X-ray emission is due to
matter accreting onto the star.

> http://SkyandTelescope.com/news/article_1327_1.asp

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HIGHLIGHTS OF THIS WEEK'S SKY

* Full Moon on Sunday, August 29th.
* Venus (magnitude -4.2, in Gemini) shines brightly high in the east before and
during dawn -- the bright Morning Star.
* Uranus is at opposition (opposite the Sun in our sky) on Friday, August 27th.

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

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

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   * Associate Editor StuartGoldman@aol.com *
   | Sky & Telescope |
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