Free Astronomy Magazine September-October 2020

49 R esembling a butterfly with its symmetrical structure, beauti- ful colours, and intricate pat- terns, this striking bubble of gas — known as NGC 2899 — appears to float and flutter across the sky in this new picture from ESO’s Very Large Telescope (VLT). This object has never before been imaged in such striking detail, with even the faint outer edges of the planetary nebula glowing over the background stars. NGC 2899’s vast swathes of gas ex- tend up to a maximum of two light- years from its centre, glowing brightly in front of the stars of the Milky Way as the gas reaches tem- peratures upwards of ten thousand degrees. The high temperatures are due to the large amount of radia- tion from the nebula’s parent star, which causes the hydrogen gas in the nebula to glow in a reddish halo around the oxygen gas, in blue. This object, located between 3000 and 6500 light-years away in the Southern constellation of Vela (The Sails), has two central stars, which are believed to give it its nearly sym- metric appearance. After one star reached the end of its life and cast off its outer layers, the other star by ESO now interferes with the flow of gas, forming the two-lobed shape seen here. Only about 10–20% of plane- tary nebulae display this type of bipolar shape. Astronomers were able to capture this highly detailed image of NGC 2899 using the FORS instrument installed on UT1 (Antu), one of the four 8.2-metre telescopes that make up ESO’s VLT in Chile. Standing for FOcal Reducer and low dispersion Spectrograph, this high- resolution instrument was one of the first to be installed on ESO’s VLT and is behind numerous beautiful images and discoveries from ESO. FORS has contributed to observa- tions of light from a gravitational wave source, has researched the first known interstellar asteroid, and has been used to study in depth the physics behind the formation of complex planetary nebulae. This image was created under the ESO Cosmic Gems programme, an out- reach initiative to produce images of interesting, intriguing or visually at- tractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that can- not be used for science observations. All data collected may also be suit- able for scientific purposes, and are made available to astronomers through ESO’s science archive. Stunning space butterfly captured by VLT !