Starship Asterisk*

SPHERE reveals earliest stage of planetary nebula formation

[imghover=http://cdn.eso.org/images/large/eso1523a.jpg]http://cdn.eso.org/images/large/eso1523b.jpg[/imghover][c]Credit: ESO/P. Kervella[hr][/hr][/c]

Some of the sharpest images ever made with ESO’s Very Large Telescope (VLT) have, for the first time, revealed what appears to be an ageing star giving birth to a butterfly-like planetary nebula. These observations of the red giant star L2 Puppis, from the ZIMPOL mode of the newly installed SPHERE instrument, also clearly showed a close companion. The dying stages of stars continue to pose astronomers with many riddles, and the origin of such bipolar nebulae, with their complex and alluring hourglass figures, doubly so. This new imaging mode means that the VLT is currently the sharpest astronomical direct imaging instrument in existence.

At about 200 light-years away, L2 Puppis is one of the closest red giants to Earth known to be entering its final stages of life. The new observations with the ZIMPOL mode of SPHERE were made in visible light using extreme adaptive optics, which corrects images to a much higher degree than standard adaptive optics, allowing faint objects and structures close to bright sources of light to be seen in greater detail. They are the first published results from this mode and the most detailed of such a star.

ZIMPOL can produce images that are three times sharper than those from the NASA/ESA Hubble Space Telescope, and the new observations show the dust that surrounds L2 Puppis in exquisite detail [1]. They confirm earlier findings, made using NACO, of the dust being arranged in a disc, which from Earth is seen almost completely edge-on, but provide a much more detailed view. The polarisation information from ZIMPOL also allowed the team to construct a three dimensional model of the dust structures [2].

The astronomers found the dust disc to begin about 900 million kilometres from the star — slightly farther than the distance from the Sun to Jupiter — and discovered that it flares outwards, creating a symmetrical, funnel-like shape surrounding the star. The team also observed a second source of light about 300 million kilometres — twice the distance from Earth to the Sun — from L2 Puppis. This very close companion star is likely to be another red giant of slightly lower mass, but less evolved. ...

• Astronomy & Astrophysics 578 A77 (June 2015) DOI: 10.1051/0004-6361/201526194 (pdf)

• Astronomy & Astrophysics 576 A46 (April 2015) DOI: 10.1051/0004-6361/201322828
  arXiv.org > astro-ph > arXiv:1503.05031 > 17 Mar 2015