Successful Close Encounter with a ‘Space Peanut’: EPOXI’s flyby to Comet Hartley 2
Just a few hours ago, NASA’s EPOXI mission spacecraft successfully flew past comet Hartley 2 at 6:59:47 a.m PDT (13:59:47 Universal Time) Thursday, Nov. 4.
The Deep Impact probe zoomed to within 435 miles (700 kilometers) of Hartley and it took incredible images of the comet’s solid nucleus. The close encounter marked just the fifth time that a spacecraft has ever visited a comet.
Experts say initial images from the flyby provide new information about the comet’s volume and material spewing from its surface. The small but active comet is full of surprises, with spinning jets, geysers of cyanide gas, and a strange, irregularly-shaped core. The nucleus is only about 2.2 km (1.4 miles) across, so there’s not much mass in it, which means that it has weak gravity. In fact, the round ends of the nucleus are bumpy and rough, indicating material is loosely aggregated there.
EPOXI is an extended mission that uses the already in-flight Deep Impact spacecraft. Its encounter phase with Hartley 2 began at 1 p.m. PDT (4 p.m. EDT) on Nov. 3, when the spacecraft began to point its two imagers at the comet’s nucleus. Imaging of the nucleus began one hour later.
I watched the coverage of this event through an online live steaming available at NASA TV. I was updating my Facebook and Twitter account as I was waiting for updates and images of the closest approach. After more than an hour since the webcast began, the first images that were taken many hours before close encounter were received. They depicted the comet nucleus as little more than a point of light, with the fuzzy coma surrounding it. I was saving screenshots every now and then as the images came in.
Moments later, a few of the close-approach images were finally shown. I was really amazed upon seeing its odd peanut-shaped body with an irregular and contoured surface. Images are available here and here. According to NASA EPOXI’s tweet, the 55 images taken about every 15 minutes were 256 x 256 subframes and the 5 close approach are full frames 1024 x 1024.
Those bright streamers of light are jets of gas shooting away from the comet, formed when frozen material on the comet surface gets heated by the Sun, expands, and shoots away.
These are medium-resolution; hi-res ones will be coming soon.
Scientists are interested in comets because they’re icy leftovers from the formation of the solar system about 4.5 billion years ago. Studying them could provide clues to how Earth and the planets formed and evolved.
Congratulations to the EPOXI team for a successful commetary encounter and for sending amazing images! 😀