1. Introduction

Chamaeleon, a constellation in the southern celestial hemisphere, is known for its diminutive size and inconspicuous appearance. Situated near the celestial South Pole, Chamaeleon occupies a relatively small area of the night sky but holds significance for astronomers due to its proximity to the southern celestial pole and its role in studying star formation and stellar evolution. Characterized by its distinctive shape resembling the chameleon, a lizard renowned for its ability to change color and blend into its surroundings, Chamaeleon is one of the 88 recognized constellations in the celestial sphere. Its celestial coordinates place it between approximately right ascension 10h and 13h, and declination between approximately -78° and -90°, positioning it in a prime location for observation from southern latitudes (Figure 1).

Figure 1. IAU chart of Chamaeleon. Source: https://www.iau.org/static/archives/images/screen/cha.jpg. Credit: IAU and Sky & Telescope. Reproduced under CC BY 4.0 license.

Despite its modest size and lack of bright stars, Chamaeleon has captured the attention of astronomers for its association with young stellar objects and star-forming regions. The constellation is home to several molecular clouds, dust lanes, and nebulae, providing fertile ground for the birth and evolution of stars. Chamaeleon's proximity to the southern celestial pole also makes it a valuable reference point for celestial navigation and mapping of the night sky.

2. Historical Background and Mythology

The constellation Chamaeleon, while lacking in prominent mythology from ancient civilizations, still holds significance in the realm of astronomy. Its name derives from the Greek word "chamai," meaning "on the ground," and "leon," meaning "lion," suggesting a connection to the mythical creature but not prominently featured in ancient mythology like other constellations.

Chamaeleon was first introduced in the late 16th century by Dutch navigators and cartographers, who charted the southern skies during their explorations. It was later incorporated into Johann Bayer's Uranometria in 1603, becoming one of the 88 modern constellations officially recognized by the International Astronomical Union (IAU). While Chamaeleon lacks ancient mythological associations, its placement in the southern celestial hemisphere makes it an important reference point for modern astronomers. Due to its proximity to the southern celestial pole, Chamaeleon is visible primarily from the southern hemisphere and serves as a guide for navigation and observation in that region of the sky.

The modern constellation Chamaeleon is not included in the Three Enclosures and Twenty-Eight Mansions system of traditional Chinese uranography because its stars are too far south for observers in China to know about them prior to the introduction of Western star charts. Based on the work of Xu Guangqi and the German Jesuit missionary Johann Adam Schall von Bell, this constellation has been classified as one of the 23 Southern Asterisms under the name Little Dipper.

3. Notable Stars

α Chamaeleontis (Alpha Chamaeleontis): Alpha Chamaeleontis is the brightest star in the constellation, but it is still relatively faint with an apparent magnitude of around 4.06. It is a binary star system composed of two main-sequence stars, both of which are orange dwarf stars. The primary star is slightly larger and more massive than the Sun, while the secondary star is smaller and cooler. The system is located approximately 63 light-years away from Earth.

β Chamaeleontis (Beta Chamaeleontis): Beta Chamaeleontis is another binary star system in the constellation, consisting of two stars designated as Beta-1 and Beta-2 Chamaeleontis. Beta-1 Chamaeleontis is a main-sequence star with a spectral type of K4V, while Beta-2 Chamaeleontis is a red dwarf star with a spectral type of M2. The system is located approximately 27 light-years away from Earth.

γ Chamaeleontis (Gamma Chamaeleontis): Gamma Chamaeleontis is a multiple star system located in the constellation. It consists of three stars designated as Gamma-1, Gamma-2, and Gamma-3 Chamaeleontis. Gamma-1 Chamaeleontis is a binary star system, while Gamma-2 and Gamma-3 Chamaeleontis are single stars. The system is located approximately 163 light-years away from Earth.

δ Chamaeleontis (Delta Chamaeleontis):  Delta Chamaeleontis is a wide double star. The brighter star is Delta² Chamaeleontis, a blue-hued star of magnitude 4.4. Because of its moderate brightness, δ2 Chamaeleontis should be easily visible from locations with dark skies. Delta¹ Chamaeleontis, the dimmer component, is an orange-hued giant star of magnitude 5.5. They both lie about 350 light years away.

4. Deep-Sky Objects

Chamaeleon I Dark Cloud: The Chamaeleon I dark cloud is a large molecular cloud complex located in the constellation. It is one of the closest regions of active star formation to Earth, making it a valuable target for studies of stellar birth and evolution. Within the Chamaeleon I dark cloud, astronomers have identified numerous young stellar objects, protostars, and protoplanetary disks, providing insights into the early stages of planetary system formation.

Chamaeleon II Dark Cloud: Similar to Chamaeleon I, the Chamaeleon II dark cloud is another molecular cloud complex in the constellation associated with ongoing star formation activity. It is located slightly to the southeast of Chamaeleon I and contains a diverse population of young stars and protostellar objects. Observations of Chamaeleon II have revealed the presence of accretion disks, outflows, and other features characteristic of regions undergoing active star formation.

NGC 3195: NGC 3195 is a planetary nebula located in the constellation Chamaeleon. It is notable for its distinctive shape, resembling a butterfly or hourglass when viewed in certain images. Planetary nebulae like NGC 3195 are formed when a star reaches the end of its life cycle and sheds its outer layers, creating a glowing shell of ionized gas. NGC 3195 serves as a valuable target for studies of stellar evolution and the late stages of stellar life.

Chamaeleon Molecular Cloud Complex: The Chamaeleon molecular cloud complex is a large region of interstellar gas and dust located in the constellation. It is one of the closest star-forming regions to Earth and contains several dark nebulae, reflection nebulae, and young stellar objects. The Chamaeleon molecular cloud complex has been extensively studied by astronomers using ground-based observatories and space telescopes, providing valuable insights into the processes of star formation and the structure of the interstellar medium.