Rosetta hits yet another milestone; witnesses Comet 67P’s perihelion moment

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Rosetta hits yet another milestone; witnesses Comet 67P's perihelion moment
This single frame Rosetta navigation camera image was acquired at 01:04 GMT on 13 August 2015, just one hour before Comet 67P/Churyumov–Gerasimenko reached perihelion. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

The European Space Agency’s Rosetta mission has hit yet another milestone as it witnessed Comet 67P/Churyumov–Gerasimenko make its closest approach to the Sun at 02:03 GMT on August 13.

ESA said that at exact moment of perihelion, the comet was at a distance of 186 million km from Sun.

Rosetta spacecraft managed to take a string of images as Comet 67P was on its way to the perihelion and from the images it is quite evident that the amount of activity was at its peak. One image taken by Rosetta’s navigation camera was acquired at 01:04 GMT, just an hour before the moment of perihelion, from a distance of around 327 km, the ESA announced.

“Activity will remain high like this for many weeks, and we’re certainly looking forward to seeing how many more jets and outburst events we catch in the act, as we have already witnessed in the last few weeks,” says Nicolas Altobelli, acting Rosetta project scientist.

This series of images of Comet 67P/Churyumov–Gerasimenko was captured by Rosetta’s OSIRIS narrow-angle camera on 12 August 2015, just a few hours before the comet reached the closest point to the Sun along its 6.5-year orbit, or perihelion. The images were taken from a distance of about 330 km from the comet. The comet’s activity, at its peak intensity around perihelion and in the weeks that follow, is clearly visible in these spectacular images. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
This series of images of Comet 67P/Churyumov–Gerasimenko was captured by Rosetta’s OSIRIS narrow-angle camera on 12 August 2015, just a few hours before the comet reached the closest point to the Sun along its 6.5-year orbit, or perihelion.
The images were taken from a distance of about 330 km from the comet. The comet’s activity, at its peak intensity around perihelion and in the weeks that follow, is clearly visible in these spectacular images. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

According to some measurements made by Rosetta, the comet is spewing out up to 300 kg of water vapour per second – about 1000 times more as compared to same time around last year when it was spewing out just 300 grams of water vapour per second.

Along with gas, the nucleus is also estimated to be shedding up to 1000 kg of dust per second, creating dangerous working conditions for Rosetta.

Though the event is quite exciting, Rosetta mission scientists are making sure that the spacecraft is at a safe distance from the comet. Mission scientists had to reposition the spacecraft at a distance of between 325 km and 340 km so as to ensure that Rosetta’s startrackers can operate without being confused by excessive dust levels.

One of the primary science goals of Rosetta is to monitor the comet’s changing environment in the lead up to, during and after perihelion. With the perihelion now gone, mission scientists will have enough data to work with and find answers to lot of questions about the comet.

The comet’s average temperature has also been on the increase. Not long after arriving, surface temperatures of around –70ºC were recorded. By April–May 2015, this had risen to only a few degrees below zero celsius, and now highs of a few tens of degrees above zero are forecast for the next month.

Meanwhile, astronomers back on Earth have been following the comet’s evolution from afar. Rosetta is far too close to the comet to see its growing tail, but images collected over the past few months with telescopes across the world show that it already extends more than 120,000 km.

A lop-sided coma, with a notable high-density region away from the main tail, was revealed in various images, including some taken last week from the Gemini-North telescope on Mauna Kea, Hawaii.

Patrick Martin, ESA’s Rosetta mission manager remarks: “It’s exciting to reach the milestone of perihelion, and we look forward to seeing how this amazing comet behaves as we move away from the Sun with it over the coming year.”