Look Up! The Southern Delta Aquariids Meteor Shower Is Here
Wake a few hours before sunrise tomorrow and you can start your day with some shooting stars. The Southern Delta Aquariid meteor shower is peaking this week, and while it's not the brightest show of the year, conditions are good and the moonlight is minimal. Provided you live in an area lacking light pollution, you might be in for quite a treat.
Consider this shower to be the big warmup for the Perseids next month. You might even see a Perseid or two tonight (though it's not like they're labeled; just stick with probability when you tell everyone what you saw). So where did these meteors come from, and what's going on up there?
BUZZING THE SUN
The Delta Aquariids are suspected to be the debris of 96P/Machholz, a sungrazing comet that orbits the Sun every 5.3 years. Sungrazers are the fighter pilots of the comet world, buzzing perilously close to the face of the Sun as they go about an orbit. Machholz is their Chuck Yeager. The comet's perihelion—that is, its point closest to the Sun in its orbit—is 0.1 astronomical unit. This puts it far closer to the Sun than Mercury, whose perihelion is 0.3 AU. (Earth is 1 AU.) When Machholz is at aphelion—its maximum distance away from the Sun—it reaches 5.9 AU, which is beyond even Jupiter's orbit.
It gets weirder yet. The comet's orbital inclination is 58 degrees. Rather than circle the Sun along the orbital plane of most planets (think of the light bulb and marble-on-wires model of the solar system from grade school), it is swooping up and away pretty dramatically. This adds up to a comet without fear, and as it goes about its orbit, it leaves behind a debris field of dust and sand-sized particles. That's where the Earth comes in. Every year as we travel our orbit, we cross through Machholz's trail, slamming into those particles at tens of thousands of miles per hour. When they burn up in our atmosphere, we get the stunning light show we call a meteor shower.
As the shower's name implies, its radius—the seeming point of origin in our night sky—is the constellation Aquarius. Don't limit yourself to looking specifically in that area, though; all the sky is a meteor's canvas. You should give your eyes 30 minutes to adjust to the darkness. Bring a blanket and scan about 45 degrees up from the horizon. That's where the most action will begin to be apparent. Good news if you live in the southern hemisphere (or if you live near the equator in the northern hemisphere): You will get the best viewing of anyone on Earth.
The meteors should be visible until sunrise. If you oversleep or the weather is bad, try again tomorrow night. This shower doesn't have a pronounced peak like others, and you have a fair chance of catching something if you stick with it in the days ahead. The next big meteor shower will be the Perseids, which will peak on the night of August 12.