Friday, December 5, 2014

ESA Hubble Image: Cat's Eye Nebula Scanned

An ESA HST image of the Cat's Eye nebula taken with the ACS/WFC (integration time 1.2 h; north is up and east is left). 

The scale of the image is ~1 by ~1 arcminute. 
Middle: the ~84,000 Gaia detections that were made in this area from 25 July to 21 August 2014. 

A superposition of the two images, showing that Gaia is actually able to detect not only stars but also high surface brightness filamentary structures.

HST image credit: NASA, ESA, HEIC, The Hubble Heritage Team (STScI/AURA)

Gaia image credit: ESA/Gaia/DPAC/UB/IEEC

The top image shows a Hubble Space Telescope exposure of the Cat's Eye Nebula, also known as NGC 6543.

This 1000-year old planetary nebula hosts a central, roughly one solar-mass star at a distance of about 1 kpc.

The Cat's Eye Nebula is coincidentally located very close to the north ecliptic pole, which is one of the two areas on the sky which was scanned some 222 times by Gaia during the 4-week period between 25 July and 21 August 2014 (commonly known as the "28 days undisturbed ecliptic-pole scanning law" phase at the beginning of Gaia's nominal life).

In this period, Gaia's on-board detection algorithms registered more than 84,000 detections in the nebula, depicted in the centre image above.

During Operations Rehearsal 5, which is currently being conducted by the Data Processing and Analysis Consortium (DPAC), these on-board detections were mapped on the sky during the cross-matching process at the Data Processing Centre in Barcelona (DPCB), somewhat surprisingly revealing that they accurately trace out gaseous filaments in the nebula (right image).

Various details in the structure of the nebula, as well as the unexplained presence of hard X rays, suggest that the central star may be a double-star system with an accretion disk and precessing jets.

Gaia will carefully monitor this object until 2019 and the end-of-mission micro-arcsecond astrometry may well reveal the binary nature of this enigmatic system.

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