[meteorite-list] Comet Could Brighten Night Skies Next Spring

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:25:40 2004
Message-ID: <200305161654.JAA09029_at_zagami.jpl.nasa.gov>

http://space.com/spacewatch/comet_NEAT_2004_030516.html

Comet Could Brighten Night Skies Next Spring
By Joe Rao
SPACE.com
16 May 2003

Mark your calendars for this time next year, when a rare, bright naked-eye
comet might grace the spring evening sky. Then again, maybe not.

Back on Aug. 28, 2001, the International Astronomical Union (IAU) announced
the discovery of a new comet spotted by Near Earth Asteroid Tracking team at
Palomar Observatory in southern California. Like several other comets, this
one has come to be called NEAT, the acronym for the discovery program.

The comet should not be confused with another that recently looped around
the Sun and that also bore a NEAT moniker. That comet NEAT was designated
C/2002 V1. The comet NEAT anticipated for next year has been designated as
C/2001 Q4.

The potential

The potential for a bright comet show for the spring of 2004 is based on an
improved orbit that places the new comet NEAT's closest point to the Sun, or
perihelion, at a distance of 89.4 million miles (143.9 million kilometers)
on May 15, 2004.

The comet was nearly a billion miles (1.6 billion kilometers) from the Sun
when it was discovered. At that time it was shining at magnitude 20, or more
than 398,000 times dimmer than the faintest star visible to the unaided eye.
Most comets would be completely invisible at such a tremendous distance,
even to the telescope that found it, so the implication is that Comet NEAT
C/2001 Q4 may be an unusually large and active object.

The comet has brightened noticeably since its discovery, but is still very
faint -- only about magnitude 14, still some 1,600 times fainter than the
threshold of naked-eye visibility. It is located within the faint
constellation of Fornax, the Furnace. It cannot be observed at the present
time, since this part of the sky is only above the horizon during the
daytime.

Sizzle of fizzle?

Most new comets are notoriously unpredictable, and there is no guarantee
that comet NEAT won't fizzle. The big question is whether this activity is
the sign of a truly great comet or just a temporary flare-up of an ordinary
one.

A "new" comet in a parabolic orbit - that is, a comet that has never passed
near the Sun before - may be covered with very volatile material, such as
frozen carbon dioxide, nitrogen, and carbon monoxide. These ices tend to
vaporize far from the Sun, giving a distant comet a surge in brightness that
can raise unrealistic expectations. Several such flops appeared last
century.

If you are at least 35 years old, you might remember the big build-up - and
subsequent letdown - for comet Kohoutek during the Christmas season of 1973.

Kohoutek was discovered more than nine months before it was due to sweep
around the Sun. At the time of its discovery in March 1973 it appeared
unusually bright for a comet so far out from the Sun (more than half a
billion miles). Some touted it as potentially the "Comet of the Century."
Most astronomers hoped that if it was so bright and unusual at its
discovery, that it would keep on being bright and unusual as it neared the
Sun.

But it merely remained unusual rather than getting very bright.

In fact, except at the time of its perihelion, when astronauts on board the
Skylab Space Station caught a glimpse of it shining brilliantly next to the
Sun, to earthbound observers Kohoutek hardly appeared very bright at all.
Many who looked skyward - often through light polluted city skies - could
barely perceive the object without binoculars or telescopes.

Comet Cunningham in 1940-41 and Comet Austin in 1990 proved similarly
disappointing.

Not-so-NEAT calculations

On the other hand, a comet that is in an elliptical orbit and returning to
the Sun from the distant past has probably shed its highly volatile
materials, so what we would be seeing is the true underlying level of its
activity. Comet Hale-Bopp, which brightened the night sky during the late
winter and spring of 1997, fell into this class.

Unfortunately, as of this writing, calculations by orbital experts suggests
that Comet NEAT may be traveling in a parabolic orbit, hinting that it may
indeed be a new comet, like Kohoutek. This however, doesn't automatically
mean that Comet NEAT will fizzle-out, since not all-new comets become duds.
Comet Arend-Roland is an outstanding exception, a first-timer that put on a
spectacular show in April 1957.

If it indeed stays on its current prescribed path, Comet NEAT will pass
closest to the Earth on May 7, 2004 at a distance of just under 30 million
miles (48.3 million kilometers). It will appear to rise out of the evening
twilight during the first week of May 2004 and move northward from Canis
Major, through Cancer by midmonth and on into Ursa Major by month's end.

And another thing?

If the prospects for one bright comet doesn't excite you, how about two?

On Oct. 29, 2002, The IAU announced the discovery by the LINEAR survey of a
comet that may also become a bright naked-eye object in May 2004.

Designated C/2002 T7 (LINEAR), the comet is currently shining at around 15th
magnitude. The latest orbit suggests that it will come closest to the Sun on
April 23, 2004 at a distance of about 57 million miles (91 million
kilometers). Comet LINEAR, however, appears to be on projected May 2004
track that would take it eastward through the constellations of Pisces,
Cetus, Eridanus, Lepus and Canis Major. This would be too low in the sky and
too close to the Sun, except perhaps for those at far-southerly latitudes
such as Australia, South Africa.

Should either comet evolve into a bright first-magnitude object as some
forecasts suggest, either or both could end up becoming striking sights one
year from now, with NEAT adorning our evening sky soon after sunset and
LINEAR appearing first in the morning and then later in the evening.

But if either or both turns out to be duds, they will appear as nothing more
than fuzz-balls in small telescopes.

We'll just have to wait and see. One thing is for sure: the countdown is on!
Received on Fri 16 May 2003 12:54:51 PM PDT