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Current Affairs

Ultra-violet Aurora

Date: 24 September 2020 Tags: Space

Issue

The space around Comet 67P Churyumov-Gerasimenko (67P/C-G) has been observed glowing with far-ultraviolet auroral radiation.

 

Background

Aurora is not unique to our planet. The phenomenon has been spotted shining in the atmospheres of every other planet except Mercury.

 

Details

  • Auroras are generated by the excitation of charged particles in an atmosphere.

  • Here on Earth, for instance, the solar wind blows into the magnetosphere and interacts with charged particles there.

  • These particles rain down into the upper atmosphere and are funnelled up the magnetic field lines to the poles, where they manifest as rippling curtains of light.

  • It works differently on different bodies, though. The auroras of Ganymede and Europa are generated by interactions with Jupiter's magnetic field.

  • Venus doesn't have a magnetic field of its own, but interactions with the solar wind create one strong enough to trigger auroras.

  • Mars' atmosphere is extremely thin, but its weak magnetic field can support auroras.

  • Comet 67P/C-G doesn't even have a borrowed magnetic field. But it does have an atmosphere of gas called a coma that surrounds the nucleus of an active comet when it draws close enough to the Sun for ices trapped therein to sublimate.

  • It was in this coma that the far-ultraviolet (FUV) spectrograph on the Alice instrument aboard the Rosetta spacecraft detected a glow in far ultraviolet light.

  • The combination of the acceleration process and the excitation process make Comet 67P/C-G's aurora unique so far in the Solar System.

  • The discovery could offer new clues to understanding how auroras are generated throughout the Solar System.

  • But cometary auroras can be used as a tool for understanding space weather. By probing the glow at various distances from the Sun, astronomers could learn a lot about electron variability in the solar wind.