See the Eta Aquarid Meteor Shower

Here's the Eta Aquarid's radiant as seen from latitude 30° north
(Houston, Cairo, Delhi, Shanghai) 90 minutes before sunrise. Farther
north, the radiant is even lower when the sky starts to get light. But
Eta Aquarids are occasionally seen as far north as the Mid-Atlantic
States.

The Eta Aquarids might be the best meteor shower that you've never heard of. This shower is caused by flecks of dust released from the nucleus of Halley's Comet. It stays near full strength for five days — longer than any comparably intense shower — and its meteors are bright and plentiful.

So why isn't it better known?

If you live in the Southern Hemisphere, where this is arguably the year's best meteor shower, you've very likely heard of it. But relatively few Eta Aquarids are visible from mid-northern latitudes, where the lion's share of amateur astronomers live. Still, this shower puts on quite a respectable show in the southernmost tier of the United States. And because the meteors are so bright, they're occasionally seen much farther north than that during morning twilight — and even broad daylight.

Conditions are ideal for the Eta Aquarids this year, because the Moon is absent from the sky during the predawn hours. The shower is forecast to peak on the morning of Friday, May 6th, with good activity from the 4th through the 8th.

As the name Eta Aquarids suggests, all of this shower's meteors appear to radiate from a spot near the northeastern corner of the constellation Aquarius. The higher a shower's radiant is in the sky, the more meteors you can see, and you won't see any meteors at all when the radiant is significantly below the horizon.

In the case of the Eta Aquarids, the radiant doesn't rise until long after midnight, and it reaches its highest in the sky well after sunrise. So the best time to watch for meteors is anywhere from one to two hours before sunrise. Earlier than that, the radiant is too low — any later, the sky is too bright.

So-So Prospects for Comet Elenin

Comet Elenin on March 14, 2011

Last December, comet-lovers got a bit of an adrenaline rush when they learned that a new object, Comet Elenin (C/2010 X1), might reach naked-eye brightness a week or so after it reaches perihelion on September 10th.

It's still early in the game, but reports from visual and photographic observers over the past few weeks have tempered expectations somewhat.

Those looking for Comet Elenin by eye have found it elusive. Only two observers — Jakub Koukal, using a 9½-inch (24-cm) reflector in the Czech Republic; and Juan José González Suárez, using an 8-inch Schmidt-Cassegrain in Spain — feel certain they glimpsed it by eye in early April. But it was a no-show for comet-hunter Alan Hale, who had a larger telescope at a pitch-black site 7200 feet (2200 m) up.

Another consideration is that the visual estimates (magnitude 15.3 and 14.9, respectively) are at odds with CCD observations suggesting something no brighter than magnitude 16. Such differences would make sense if Comet Elenin were somewhat diffuse, but everyone agrees that it's strongly condensed and almost stellar in appearance.

Koukal and González are veteran observers who carefully checked their sightings against faint nearby stars. Even so, former S&T columnist John Bortle, who's watched comets come and go for more than 50 years, is skeptical of visual sightings made at the hairy edge of a telescope's capability. "I can cite many instances of 'positive' observations turning out to be spurious, even when made by experienced observers," he notes.

For now, who can or can't see it doesn't matter much, as the interloper is still heading inward and won't get seriously worked up for several months. But the comet cognoscenti have already started calling it "intrinsically faint," and it's becoming clear that hopes for a nice eyeball-easy showing have dimmed considerably.

Best guesstimates now suggest that Comet Elenin's total brightness might peak near magnitude 6 in mid-September — a nice binocular object — presuming that it survives its dash through perihelion just 45 million miles (0.48 astronomical unit) from the Sun.

Meanwhile, you have my permission to ignore or refute any of the wacky postings about the supposed danger posed by Comet Elenin. All this nonsense seems to have started back in January, when edge-of-reality blogger Laura Knight Jadczyk made provocative warnings — all based on information from a member of her research team who's "an astronomer at a large observatory". (Yea, right.) It's not even worth giving you a link to her ramblings.

MESSENGER: Mercury Surface,

Click on image to enlarge.

Early this morning, at 5:20 am EDT, MESSENGER captured this historic image of Mercury. This image is the first ever obtained from a spacecraft in orbit about the Solar System's innermost planet. Over the subsequent six hours, MESSENGER acquired an additional 363 images before downlinking some of the data to Earth. The MESSENGER team is currently looking over the newly returned data, which are still continuing to come down. Tomorrow, March 30, at 2 pm EDT, attend the NASA media telecon to view more images from MESSENGER's first look at Mercury from orbit.

The dominant rayed crater in the upper portion of the image is Debussy. The smaller crater Matabei with its unusual dark rays is visible to the west of Debussy. The bottom portion of this image is near Mercury's south pole and includes a region of Mercury's surface not previously seen by spacecraft. Compare this image to the planned image footprint to see the region of newly imaged terrain, south of Debussy. Over the next three days, MESSENGER will acquire 1185 additional images in support of MDIS commissioning-phase activities. The year-long primary science phase of the mission will begin on April 4, and the orbital observation plan calls for MDIS to acquire more than 75,000 images in support of MESSENGER's science goals.

On March 17, 2011 (March 18, 2011, UTC), MESSENGER became the first spacecraft to orbit the planet Mercury. The mission is currently in its commissioning phase, during which spacecraft and instrument performance are verified through a series of specially designed checkout activities. In the course of the one-year primary mission, the spacecraft's seven scientific instruments and radio science investigation will unravel the history and evolution of the Solar System's innermost planet. Visit the Why Mercury? section of this website to learn more about the science questions that the MESSENGER mission has set out to answer.