Messier 46 (M46) and NGC 2438 Planetary Nebula

Also Known as: NGC 2437 (M46), Collinder 159 (M46)

Object Type: Open Cluster (M46), Planetary Nebula (NGC 2438)

Constellation: Puppis

Distance from Earth: 5,400 light years (M46), 1370 light years (NGC 2438)

Apparent Magnitude: 6.1 (M46), 10.8 (NGC 2438)

Coordinates: RA 07H 41.8M 0S DEC -14 deg 49 min 0 sec

Actual Size: 30 light years in diameter (M46)

Apparent Dimensions: 27 arc-minutes (M46), 1.1 arc-minutes (NGC 2438)

Discovered by: Messier 46 was one of Charles Messier’s original discoveries.
Messier first observed the cluster in 1771, after he had already published the first edition of his catalogue. He added M46, M47, M48 and M49 to the list on February 19, 1771, only three days after presenting his catalogue to the academy.
Messier described M46 as a “cluster of very small stars, between the head of the Great Dog [Canis Major] and the two hind feet of the Unicorn [Monoceros], [its position] determined by comparing this cluster with the star 2 Navis, of 6th-magnitude, according to Flamsteed; one cannot see these stars but with a good refractor; the cluster contains a bit of nebulosity.”
NGC 2438 was discovered by William Herschel on March 19, 1786.

Description: Messier 46 (M46) is an open star cluster located in the constellation Puppis.
Messier 46 is a relatively bright, large cluster containing about 500 stars. Messier 46 is a densely populated cluster. About 150 of its members are of magnitude 10 to 13 and the brightest stars belong to the spectral class A0.
These stars are about 100 times more luminous than the Sun. The single brightest star in M46 has a visual magnitude of 8.7.
The cluster is classified as Trumpler type II,2,r, which means that it is detached from the surrounding field, but its stars are not very concentrated toward the center(II), the stars have a moderate range of brightness, and the cluster is richly populated (r), with more than 100 confirmed members.
The cluster’s estimated age is 300 million years. M46 is moving away from us at 41.4 km/s.
The planetary nebula NGC 2438 appears superimposed on M46 and is located about 7 arc minutes northeast of the cluster’s center.
The nebula is believed to lie in the foreground, at a distance of about 2,900 light years from Earth.
It is receding from us at 77 km/s and, as it doesn’t share the cluster’s radial velocity, it is most likely not physically related to it
NGC 2438 is a multi-shell planetary nebula with a bright inner nebula with a diameter of 60″, consisting of two somewhat detached shells.
NHC 2438 is expanding with a velocity of 37 km/s.
The structure of NGC 2438 is surrounded by a fainter, mostly circular halo that is more visible on the western half, and has a diameter of 130″. The mass of the main nebula is estimated at 0.45 of the mass of our Sun.
The nebula consists of material ejected from the central star during the asymptotic giant branch stage, beginning some 8,500 years ago. The main nebula was formed at about half that age.
The central star of this planetary nebula is a 17.7-magnitude white dwarf, with surface temperature of about 75,000 K (74,700 °C).[10] It is one of the hottest stars known.

Click Below Image(s) for Full Size:

Messier 46 is easy to see in binoculars and small telescopes.
It can be found using Sirius, the brightest star in the night.
In 10×50 binoculars, the cluster appears hazy and almost like a nebula, but larger binoculars reveal a large open cluster with about 50 dim stars. Larger telescopes show a field of faint stars that are very similar in brightness.
M46 is best seen from southern and equatorial latitudes during the months of December, January and February.

Platesolve

M46 Open Cluster and NGC 2438 Planetary Nebula

Imaging Details
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