Constellation of the Month – Chamaeleontis
Constellation of the Month – Chamaeleontis – The Chameleon
Chamaeleon is one of the faintest constellations in the sky. It is a small, obscure group of stars close to the south celestial pole at between declinations 85° south and 93° south or lying between Carina and Octans.
So, for those of us in the Southern Hemisphere it is reasonably well placed for viewing all the year. The constellation spreads through 90° round the pole; as a result the constellation is at its highest in the sky at 11pm AEST between mid March and mid June. In February when Pictor is at its highest, Chamaeleon is lower and somewhat to the left.
Chamaeleon first appeared in Bayer’s Uranometria of 1603. Chameleons are family of lizards found in Europe, Africa, and Asia. Madagascar seems particularly blest with them (about 35 species), and it may be these to which the constellation refers. Chameleons can change color, and have toes fused into groups of two and three, teeth attached to the edge of the jaw, and a long tongue. Like its namesake in the animal kingdom, this constellation does not stand out.
Since Musca the Fly, is on its eastern boundary some early astronomers joined the two constellations, showing the chameleon as trying to eat Musca, the Fly. Like many of the constellations introduced in this era, has little to offer the amateur. The proximity to the pole also makes it difficult to observe – particularly if you have a fork-mounted telescope but since I have a Dobsonsian also it is a bit of good fun to go and star hop through the constellation. The suggested path to Chamaeleon is to imagine a line starting at ‘the top star in the Southern Cross’, γCrux, passing through αCrux, ‘the bottom star in the Southern Cross’, and continuing toward the South Celestial Pole to a point which is approximately 2.6 times the distance, between γCrux and αCrux, beyond αCrux. When looking south from the Southern Cross toward Chamaeleon, βCha will be just to the left of the end of the line.
There are no stars that are brighter than 4th magnitude with Chamaeleon. The brightest is the star Gamma Chamaeleontis, at magnitude 4.1. Alpha and Theta Cha form a wide double pair easily able to be seen with the naked eye. They have contrasting colors of white and orange. Chameleon also contains two close double stars. Delta, which has two yellow components separated by 0.6 arcseconds and Epsilon which has two components both of which are blue-white in color with a separation of 0.9 arcseconds.
Alpha Chamaeleontis’ spectrum shows that it is a relatively rare, white giant of spectral class F5 III. However it has an uncertain surface temperature of 6770 K. This leads to the conflict that both its temperature and luminosity would seem to indicate that the star is not actually a giant, but rather an advanced hydrogen-fusing main-sequence star of 1.55 solar masses.
Situated halfway between eta and iota Chamaeleontis is the asterism Streicher 21. This consists of a handful of magnitude 9 stars in a well-formed line from north-west to south-east that stands out beautifully against the background ground star-field. The shape of the stars resembles a snake to me, complete with a tail pointing to the south.
NGC 3195 is a 12th magnitude planetary nebula located in Chameleon, but it will require at least a 10-inch telescope to identify it. It is a bright and prominent planetary nebula that is well worth searching out. The colour is white and all I could see was a uniform fuzzy patch although photographs do show some structure reminiscent of the dumbbell nebula.
NGC 3149 is a spiral galaxy of apparent size 2′ x 1.9′ located about 30′ to the NNW of NGC 3195 and situated 1.3 degree north-east of the magnitude 5 zeta Chamaeleontis. This faint, slightly oval, hazy glow in an east-to-west direction is barely visible, with just a glimpse of a brighter middle area. It can be difficult to observe however.
Between these two deep-sky objects is a beautiful double star of around magnitude 9.5, displaying colours of yellow and orange.
ESO 37-01 also known as E3 is a relatively unknown globular cluster with a magnitude of 43 arc-minutes south of the galaxy NGC 2915. Due to loss of stars resulting from tidal effects, E3 is a very loose, star-poor globular, one of the faintest known thus far.
IC 2631 is a fairly bright patch of reflection nebulosity about 2′ across surrounding a 9th magnitude star.
NGC3620 is an edge on spiral galaxy situated just 32 arc minutes north of IC 2631 and 32 arc minutes off the border with the Carina constellation. Only with averted vision can the thin, soft and faint substance of the galaxy be seen. This extremely faint galaxy appears in an east-to-west direction, and reveals a spotless surface without any outstanding features. A nice circle of faint field stars starts at the western side of the galaxy, extending around south.
The constellation Chamaeleon is also home to a dark nebula which has been listed as Sa 156 in Sandqvist’s Catalogue of Dark Nebulae, published in 1977. Within an imaginary triangle, consisting of NGC 3620, beta Chamaeleontis and the border of Musca, this dark area can be looked for. It is a rather large dark patch around 3×2 degrees in area, lying in a roughly north-to-south direction, and is worth a search with the naked eye.
Mamajek 1: The stars around eta Chamaeleontis, 1.8 degrees south-east of theta Chamaeleontis, have been identified only as recently as 1999 as a brand-new open cluster. The cluster contains approximately ten super-white members that display the same proper motion through space. This now well-known cluster was only discovered in 1999 and has proved to be situated just 329 light years away and formed about 10 million years ago. Being, as far as we know, the fourth closest cluster to us, three of its members are visible in binoculars. It is located approximately 316 light years distant and believed to be around eight million years old.
What is more, there is an extremely faint galaxy, PGC 24516/ESO 18-G13, less than two arc-minutes east of eta Chamaeleontis, sharing this new cluster’s territory.
HD63454: A 9.37 magnitude K4V spectral type star is located at a distance of 116.76 Light Years from our Solar system. It has a planetary system which has a confirmed planet believed to be a Dark Hot Jupiter. The planet is positioned out side of the habitability zone at a mean orbital distance of 0.036 AU. The planet orbits around the star every 2.81782 ± 0.000095 days and was discovered in 2005.
Refs: Wikipaedia; http://www.constellation-guide.com/constellation-list/, Simbad, NGC/IC Catalogue, Uranometria and transitplanets.org.