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Running Low On Planets?

For several months now, observers have been treated to an early evening night sky filled with four, and sometimes even five, naked-eye planets. This month is your last chance for a long time!


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Right after sunset, look low in the west for brilliant Venus. Just above and to the left of Venus is Mars, which will be a lot fainter but will display a faint reddish-orange color. And, just above and to the left of Mars is Saturn. Saturn will be much brighter than Mars, but not as bright as Venus. Watch the relative positions of these three planets throughout the month. Mars will move the quickest, appearing closer to Saturn each night. Watch closely on the night of the 21st and you'll also see a thin crescent Moon join the grouping. Then, over the next few days Mars will pass Saturn in the sky.

All three planets will set earlier each and every night. By the end of the month, Venus will be too close to the Sun to see, while Saturn and Mars will only be visible briefly before setting too. By the middle of June, they will all be gone. All we'll have left for company is mighty Jupiter, still shining prominently just beneath Leo the Lion.

Some of our planets will reappear for early morning observers, but our evening planet parade is almost over for now. Enjoy the show while you can!

Comets, Two-for-One!

This month will be another great one for skywatching. Not only are there four planets visible in the early evening sky, but there will be one, and maybe even two naked-eye comets. Naked-eye comets are extremely rare events to begin with. Two at the same time is, to put it mildly, astounding.

You do not need a telescope to see a bright comet - in fact, you don't want to use a telescope, because you'll just be magnifying something that's already too large to fit in the telescope's field of view. If the comets put on a good show, all you'll need will be your own two eyes and a clear, dark sky. Binoculars can really enhance the view and still allow you to see a large area of the sky.

Each comet may appear as a small hazy patch or fuzzy 'star'. If you can get away from the influence of city lights, you should also be able to see the tail of the comet. Because a comet tail points away from the Sun, look for the tail to stretch upward and slightly to the left in the sky. The darker the sky, the more you will be able to see. Use binoculars to follow the tail of the comet even further.

Every weekend in May, and the first weekend in June, Sudekum Planetarium and the Barnard-Seyfert Astronomical Society will host star parties to offer great views of the comets... and you're invited! Vist our star parties page for more information!

May begins with Comet C/2002 T7 (LINEAR) low in the east just before sunrise. It may be tricky to see unless you've got an eastern horizon clear of trees and other obstructions - and you'll probably need binoculars. It will only be visible for a few days before getting lost in the glow of sunrise. But don't worry, it'll be back and better in a few weeks.

Meanwhile, around May 4, you will want to start watching for Comet C/2001 Q4 (NEAT) low in the southwest after sunset. It is projected to be brightest between May 7 and 10 and then begin to slowly fade over the next several weeks. The good thing is that every night the comet will appear higher in the sky.

It is important to remember that comets do NOT go "whoosh" across the sky like a "shooting star" or "meteor". They appear stationary against the background stars. Their position may change from night to night, but usually not all that much.

While the comet will be visible for a good portion of May, astronomers are particularly looking forward to May 14 and 15, when Comet NEAT will be right next to the bright open star cluster called the Beehive in the constellation of Cancer the Crab. Lucky viewers in eastern Asia will even get to see the comet's tail pass right in front of the Beehive on the 15th. Expect to see some amazing photographs of this event!

During the last week of May, Comet LINEAR comes back for an encore appearance. Watch low in the southwest after sunset starting around May 26. LINEAR will appear higher in the sky each night, and for several days, LINEAR and NEAT will be in the sky at the same time. Both comets will quickly fade as June begins.

Update, 5/11/04: Comet NEAT so far hasn't become bright enough to see with the naked eye. It is visible with binoculars. Keep watching for it to get higher in the sky every night, and cross your fingers for Comet LINEAR!

What's With the Weird Names?

If you try to do an internet search for Comet NEAT or Comet LINEAR, you might end up getting very confused. That's because over the years, there have been several comets called NEAT or LINEAR. Comets are named after their discoverer. You'll hear about comets named Shoemaker or Levy or Hyakutake or West, or many other names. But NEAT and LINEAR aren't people, they're telescopes!

NEAT stands for Near Earth Asteroid Tracking, and LINEAR is the Lincoln Near Earth Asteroid Research project. Each program uses telescopes to detect asteroids that could potentially hit Earth. A side benefit is that they are excellent comet-catchers. As of this writing, NEAT has discovered 43 comets, and LINEAR 139. The undisputed king of comet discoveries remains the SOHO spacecraft observing the Sun. It's caught 630 comets - most of which were spotted just before they plunged into the Sun!

If it sounds a bit impersonal to name such beautiful celestial objects after a big telescope with an acronym for a name, keep in mind that the comets are really named for the teams of astronomers behind the 'scopes. All share credit for the discovery!

But back to that internet search that has you so confused. Since many comets end up having the same name, the International Astronomical Union also assigns each comet a unique (if somewhat boring) designation. The comet called NEAT that we're looking for this month is officially called Comet C/2001 Q4. Search for this name and you'll find the right comet. The letters and numbers indicate when the comet was discovered, and whether it's a periodic comet or if it will only make one pass, never to approach the Sun again. Both NEAT and LINEAR are non-periodic comets. This will be our only chance to see them ever!

Dirty Snowballs?

In addition to the Sun and planets and moons and asteroids, the Solar System also includes "dirty snowballs" astronomers call comets. These blobs of ice and bits of rock and dust are leftovers from the formation of the Solar System. They can orbit the Sun in as little as three years while others take tens of thousands of years to complete just one orbit.

When a comet is far from the Sun, out beyond the orbit of Jupiter where it is really cold, it remains frozen solid. This ball of material is called the "nucleus" of the comet. The nucleus of a comet is usually less than 10 miles across and is almost invisible at this distance.

As the comet gets closer to the Sun, heat from the Sun causes the ice to melt, but instead of becoming a liquid, it immediately turns into a gas. The gas and dust particles that come off the comet form an envelope that completely surrounds the nucleus. This gas cloud is called the "coma" of the comet and can grow to be as much as one hundred thousand miles across.

So now, we have a dirty snowball inside a ball of gas and dust continuing to move closer to the Sun. Sunlight reflecting off the coma makes it visible from Earth - even though it may be hundreds of millions of miles away. As the comet enters the inner Solar System, the solar wind begins to push on the gases of the coma.

The solar wind is NOT like the wind we experience here on Earth. It is NOT air rushing past the comet. The solar wind is a continuous stream of charged particles constantly given off by the Sun. The charged particles push the gases of the coma away from the Sun. As the comet gets closer to the Sun, there is more pressure, and the gases stretch out behind the head of the comet Ð forming the "tail" of the comet.

The tail of a comet can be tens of millions of miles long, however, while it appears to be made of a lot of material, astronomers describe the tail as being as close to nothing as you can get and still have something.

Transit of Venus: June 8

A historic astronomical event takes place on June 8. For the first time since 1882, the planet Venus will pass directly in front of the Sun! Visit www.transitofvenus.org for more information and how to view this event safely.

Astronomy Day: Thank you!

Special thanks to everyone who helped make our Astronomy Day event a success!

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