Perseid Meteor Outburst

Every year in August, Earth passes through a stream of debris from Comet Swift-Tuttle, source of the annual Perseid meteor shower. The shower is beloved by sky watchers. It is rich in fireballs and plays out over a two-week period of warm, starry summer nights.

This year’s display is going to be even better than usual. “Our models predict an outburst on Aug. 11-12 with peak rates greater than 200 meteors/hour under ideally dark skies,” explains Bill Cooke of NASA’s Meteoroid Environment Office. “That’s about twice as many Perseids as usual.”

Perseids in Aug. 2015, a composite image by Petr Horalek of Kolonica, Slovakia [more]

In ordinary years, Earth grazes the edge of Swift-Tuttle’s debris zone. Occasionally, though, Jupiter’s gravity tugs the huge network of dust trails closer, and Earth plows through closer to the middle. This appears to be one of those years. Experts at NASA and elsewhere agree that three or more streams are on a collision course with Earth–hence the outburst.

Observing tips: Go outside between midnight and dawn on the morning of Aug. 12th. Allow about 45 minutes for your eyes to adjust to the dark. Lie on your back and look straight up. Perseids can appear anywhere in the sky, but their tails will point back to a single point in the constellation Perseus: sky map. Increased activity may also be seen on the morning of Aug. 13th.

Got clouds? NASA is planning a live broadcast of the Perseid meteor shower overnight on Aug. 11-12 and Aug. 12-13, beginning at 10 p.m. EDT. You can also listen to radar echoes from the Perseids on Space Weather Radio. More webcasts: from Israel, from Alabama.

Realtime Perseid Photo Gallery

Green Comet Approaches Earth

On March 21st, Comet 252P/LINEAR will make a close approach to Earth–only 0.036 AU (5.4 million km) away. This is the fifth closest cometary approach on record and, as a result, the normally dim comet has become an easy target for backyard telescopes. Indeed, it is brightening much faster than expected.

“Comet 252P/LINEAR has surpassed expectations and is now bordering on naked eye visibility for southern observers,” reports Michael Mattiazzo of Swan Hill, Australia. “At the moment it is near magnitude +6,” Observing from Brisbane, Australia, Tom Harradine didn’t even need a telescope to photograph 252P/LINEAR. On March 17th, he caught the green comet (circled) passing by the Tarantula Nebula using just a digital camera:

“This image is a stack of 140 four second exposures I made using a Canon EOS 70D set at f/4.0, ISO 12800, and 200mm,” he says.

The comet is green because its vaporizing nucleus emits diatomic carbon, C2, a gas which glows green in the near-vacuum of space. The verdant color will become more intense in the nights ahead as 252P/LINEAR approaches Earth.

In recent days, astronomers have realized that Comet 252P/LINEAR might have a companion. A smaller and much dimmer comet named “P/2016 BA14” will buzz Earth even closer than 252P/LINEAR on March 22nd. P/2016 BA14 appears to be a fragment of 252P/LINEAR. Unlike its parent, however, P/2016 BA14 is “pitifully faint” and difficult to observe. Sky and Telescope has the full story.

There is a chance that the comet’s approach could cause a minor meteor shower. According to the International Meteor Organization, “[modeling by forecaster] Mikhail Maslov indicates that there might be a weak episode of faint, very slow meteors (15.5 km/s) on March 28–30 from a radiant near the star μ Leporis.” Little is known about meteors from this comet, so estimates of the meteor rate are very uncertain. Maslov’s models suggest no more than 5 to 10 per hour.

This is a southern hemisphere event. At closest approach on March 21st, 252P/LINEAR will speed through the constellations Triangulum Australis and Apus, far south of the celestial equator. Observers can use this ephemeris to point their cameras and telescopes.

Meteor Balloon in the Stratosphere

When the Geminid meteor shower peaked on Dec. 14th, a snowstorm was in progress over the mountains of central California. No stars? No problem. Using a helium balloon, the students of Earth to Sky Calculus launched a low-light camera to photograph the shower high above the obscuring clouds. Their experimental payload ascended to 91,000 feet where the night sky looked like this:

The big white object at the top of the frame is the balloon, surrounded by some of the bright stars and planets of the pre-dawn sky. From the lower stratosphere, the freezing camera was able to see stars as dim as 2nd magnitude. This wasn’t as sensitive as the students had hoped, but it was good enough to record several Geminid fireballs. Here are a couple of movies showing Geminids emerging from behind the balloon: fireball #1, fireball #2. In the movies, stars and planets move in a lazy circle around the balloon–a result of the payload’s gentle spin–while Geminids streak in straight lines. The camera also recorded the balloon exploding at the apex of the flight, and the payload parachuting back to Earth.

The students plan to observe more meteor showers in the future with even better results. They believe they can boost the sensitivity of the camera by, e.g., warming the payload bay during the flight and improving the camera’s focus, pre-launch. If their improvements succeed, they could establish ballooning as a practical and fun way to monitor meteor showers in all kinds of weather. Stay tuned for updates.