[meteorite-list] New Comet Set for Live Internet Show - Comet C/2004 F4 (Bradfield)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:13 2004
Message-ID: <200404131734.KAA11570_at_zagami.jpl.nasa.gov>

http://space.com/spacewatch/comet_bradfield_040313.html

New Comet Set for Live Internet Show
By Joe Rao
space.com
13 April 2004

A newly discovered comet should soon be visible to armchair astronomers via
images posted to the Internet from the Solar and Heliospheric Observatory
(SOHO) spacecraft. Later this month, sharp-eyed observers may also spot the
comet in the morning sky. The comet, named Bradfield, is racing through the
inner solar system at a time when two other comets are expected to become
visible to the naked eye, providing a rare trio of opportunities this
spring.

However, comets are unpredictable and casual observers may find it
challenging to see any of the objects.

Retired but working

The newest comet was discovered by William Bradfield of Yankalilla, South
Australia, while the object was in the constellation Cetus. Bradfield first
spotted it low in the western evening sky with his 10-inch telescope on
March 23 and again on March 24. Then lost sight of it until April 8.

Daniel Green of the Central Bureau for Astronomical Telegrams announced the
find on Monday.

The 76-year-old Bradfield is credited with 17 other comet discoveries dating
back to his very first on March 12, 1972. Born in New Zealand, Bradfield
worked many years for the Australian government as a research scientist on
rocket-propulsion systems before retiring in the late 1980s.

All 18 of Bradfield's discoveries bear his name alone, which means he
spotted and reported them well ahead of any other observer. (Some comets are
found by two or more observers at roughly the same time.) By having access
to stars and constellations visible only at far southerly latitudes,
Bradfield can carefully examine regions of the sky that are unavailable to
Northern Hemisphere observers.

Eighteen comets over a 32-year time span comes out to an average of one new
discovery about every 21 months. But it has been nine years since Bradfield
made his last discovery (an object catalogued as C/1995 Q1).

What to expect

Green's calculations show that the comet will continue to approach the Sun
in the coming days. It should reach perihelion (its closest approach to the
Sun) on April 17, when it will be just 0.169 astronomical unit (15.7 million
miles, or 25.2 million kilometers) from the solar system's central star.
This is well inside the orbit of the planet Mercury.

The projected brightness of this comet is somewhat uncertain, although right
now predictions indicate that it could get as bright as 2nd magnitude. That
would be easily seen with the naked eye. However, because of its very close
proximity to the Sun, the comet will be impossible to observe for a week or
more.

As it dashes past the Sun however, comet Bradfield will be visible to those
using computers and accessing near-live images from the SOHO Web site
(http://sohowww.nascom.nasa.gov/data/realtime-images.html), primarily in
images from the LASCO C3 instrument.

The comet should be within range of the SOHO imagery from about April 17
through April 19. It will appear to pass closest to the Sun -- 2.6 degrees
from its center -- on April 18.

Last year, the public was captivated by a similar scenario when SOHO
photographed a comet rounding the Sun. Hundreds of otherwise unknown comets
have actually been first detected in SOHO imagery, generating a competition
among a handful of armchair astronomers. Just last week, SOHO officials
reported the 750th discovery of a comet using the spacecraft's imagery.

Skywatching opportunity

Because it will appea to move rapidly northward after perihelion, comet
Bradfield will ultimately emerge into the morning sky for observers in
mid-northern latitudes during the final week of April.

Beginning April 23rd, skywatchers should concentrate on the east-northeast
horizon beginning about 90 minutes before sunrise.

Unfortunately, the comet is expected to fade quickly down to 4th or 5th
magnitude as it recedes from both the Sun and Earth. On this astronomer's
scale, larger numbers represent dimmer objects. The brightest objects are
zero of first magnitude, with superbright objects such as Venus achieving
negative magnitudes.

Binoculars will aid observers in sighting comet Bradfield, as well as any
tail that might appear to protrude upwards from the horizon.
Received on Tue 13 Apr 2004 01:34:35 PM PDT