NGC 2438 - April 2011

About the image…

Image Subject – NGC2438.
Location Taken – Teide Observatory (Canary Islands – Spain; 16º 30' 35" W, 28º 18' 00" N).
Telescope – IAC80.
Instrument – CCD E2V 42-40.
Focal Ratio –
Cassegrain f/11.3. Exposure – Halpha: 12 x 1,500s, OIII: 10 x 900s, SII: 7 x 900s.
Image Size –
2048 x 2048 pixels (10.4 x 10.4 arcminutes).
Image Type
Halpha-SII-OIII (RGB). Software –DSS, PhotoShop CS4.
Images taken and reduced by –
Daniel López.
Daniel López and Pablo Rodríguez-Gil.

About the object...

Object Type – Planetary Nebula.
J2000.0 Equatorial Coordinates – 07h 41m 50s; -14 º44’ 07’’.
Distance – 2,900 light-years.
Constellation – Puppis.

NGC 2438 was discovered by William Herschel in 1786. It's a planetary nebula in the constellation Puppis, at a distance of about 2,900 light years from Earth. Although this nebula appears to be within the M46 open cluster when viewed through a telescope, several studies have shown that it's actually closer to Earth, moving at a different speed than the cluster. Therefore, their proximity in the sky is only a coincidence, with both objects being in the same line of sight as viewed from our planet.

The use of narrow-band filters emphasizes a large halo-shaped structure around the main ring of the nebula. This halo is actually very difficult to detect and is especially visible with the H-alpha and [OIII] filters. This structure is very similar to that observed in M57, the Ring Nebula, which was revealed relatively recently when imaged through narrow band filters with long exposure times.

A planetary nebula is produced when a star with a mass similar to the Sun burns all the hydrogen available around its core for nuclear fusion. During this process the star's core collapses and heats up, allowing the nuclear fusion of heavier elements and ejecting its outer layers into the interstellar medium. These structures are very common in the universe, and the AIM have imaged some of the famous ones such as M27, M57 or M76.