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Ärende: S&T's Weekly News B 01/0
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 * * * SKY & TELESCOPE's WEEKLY NEWS BULLETIN - September 17, 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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THE FIRST EXOPLANET IMAGE?

Astronomers have unveiled the best candidate yet for the first direct
image of an extrasolar planet. If confirmed, the object will also be the
first planet-mass body found orbiting a brown dwarf rather than a true
star.

Last April, a team led by Gael Chauvin (European Southern Observatory)
used adaptive optics on one of the 8.2-meter Very Large Telescope (VLT)
reflectors in Chile to make an exceptionally sharp infrared picture of a
faint brown dwarf.... The new, much better image revealed a second object
only a hundredth as bright just 0.78 arcsecond to the southeast.

The excitement stems from the companion's inferred mass. The pair seems to
be part of the TW Hydrae Association, a nearby, wide-scattered group of
young stars. The pair's distance of 230 light-years, along with the
observed brightnesses and temperatures of the two objects, gives their
true luminosities. All the stars of the TW Hydrae Association were born
together about 8 million years ago. Knowing this, astronomers can compare
the luminosity and temperature of each member of the pair with models of
how substellar bodies of various masses should cool down in 8 million
years.

The result: the two weigh about 25 and 5 Jupiters. This puts the faint one
squarely in the realm of planet-mass objects rather than brown dwarfs....

> http://SkyandTelescope.com/news/article_1351_1.asp

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LOFAR: A GIANT RADIO TELESCOPE TAKES SHAPE

Radio astronomers can't wait for their new toy. It's 350 kilometers
across. It has no moving parts. It can be pointed in many different
directions at once. It can even take snapshots of the whole sky almost
continuously. And it's currently under construction in the rural
northeastern part of the Netherlands. When completed in a few years, the
Low Frequency Array, or LOFAR, will consist of some 15,000 small radio
antennas linked by fiber optics to a new-generation supercomputer. The
computer will process huge amounts of raw signals to observe distant
galaxies and pre-galaxies, gas in the Milky Way, solar flares, cosmic
rays, gamma-ray bursts, and much else.

Each cheap antenna -- consisting of little more than four copper wires in
protective PVC tubing -- will pick up low-frequency radio waves (between
10 and 250 megahertz) from the entire sky. To "aim" the telescope toward
the Crab Nebula, for example, the LOFAR software inserts the appropriate
signal delay for each antenna, so that radio waves from the direction of
the Crab arrive in phase and can be added interferometrically. "We have
full control over our directional sensitivity," says Harvey R. Butcher of
ASTRON, the Netherlands Foundation for Research in Astronomy....


> http://SkyandTelescope.com/news/article_1334_1.asp

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HIGHLIGHTS OF THIS WEEK'S SKY

* First-quarter Moon on Tuesday September 21st.
* Venus (magnitude -4.1, in Cancer) is the "Morning Star" shining brightly
high in the east before and during dawn.
* The equinox occurs at 12:30 p.m. EDT on September 22nd. This is when the
Sun crosses the equator heading south for the year -- marking the start of
fall in the Northern Hemisphere and spring in the Southern Hemisphere.
* Mercury (magnitude -1) is very low in the east in bright dawn. Look for
it very far to the lower left of brilliant Venus about 30 or 40 minutes
before sunrise.

For more details, see This Week's Sky at a Glance and Planet Round up:

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

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SAVE THE DATE (Advertisement)

Get ready for another great year of stargazing!

Celestial Wonders 2005 Calendar
> http://SkyandTelescope.com/campaigns.asp?id=398
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