The universe is full of cosmic masterpieces, none more so than this stunningly evocative vista of the Chamaeleon I dark cloud.
Chamaeleon I is part of the closest star-forming complex to us, the Chamaeleon Complex, and is depicted here with inky black dabs of interstellar dust mixed with the brushstrokes of bright reflection nebulae illuminated by young stars.
Located about 500 light years away, the Chamaeleon Complex is a giant molecular gas cloud, within which stars form when pockets of cool molecular gas, mostly hydrogen, undergo gravitational contraction and condense, thus birthing a star.
These molecular clouds are often very dusty, so much so that patches of them become impenetrable to visible light, as we can see in this image of Chamaeleon I, taken by the 570-megapixel Dark Energy Camera (DECam) on the Victor M. Blanco Telescope at the Cerro-Tololo Inter-American Observatory in Chile. The brighter regions in the image are reflection nebulae: pockets of dust close to the forming stars, off which the light of those young stars is reflected and scattered.
Chamaeleon I is home to three reflection nebulae, in particular Cederblad 111, which is the bright area located in the centre of the image. Above it is the smaller Cederblad 110, notable for its distinct C-shape.
Above Cederblad 110 is the Chamaeleon Infrared Nebula, which is a window into the star-forming region opened by streams of matter emitted from the poles of a young, low-m*** star within. In this image, the Chamaeleon Infrared Nebula appears orange-tinted.
These outflows are typical of young stars found within star-forming regions such as Chamaeleon I.
After a molecular cloud has fragmented and collapsed to form a young star, that star can then grow further by its gravity pulling in streams of gas from the cloud that surrounds it.
Sometimes, though, the young star is fed a little too well, and it can’t encomp*** all the m*** that falls onto it. Some excess material is therefore spat away, channelled by the star’s nascent magnetic field into beams of matter that spurt from the young star’s magnetic poles.
It’s one of these beams that has dug a tunnel through the molecular gas to form the Chamaeleon Infrared Nebula. Other jets from other young stars can also be seen plowing into the gas of Chamaeleon I, causing that gas to glow as what astronomers refer to as Herbig–Haro objects. Examples can be seen as small red patches all across this view of Chamaeleon I.
The most recent census of Chamaeleon I, by Penn State University astronomer Kevin Luhman in 2017, found about 50 new stars and brown dwarfs, bringing the total population of Chamaeleon I up to 226 members.
These stars are split into two clusters, north and south, within Chamaeleon I, and based on the ages of their stars, these clusters began active star formation 5 to 6 million and 3 to 4 million years ago, respectively. That star formation continues today, but at a declining rate.
Those stars are mostly small, low-m*** red dwarf stars. Luhman’s studies concluded that the Chamaeleon’s initial m*** function, which describes the initial m***es at which stars form when they condense out of a molecular cloud, is only 0.1 to 0.15 solar m***es.
Such low-m*** stars are at the bottom end of the red dwarf m*** scale, yet such stars are the most common stars in the universe, so it is no surprise to see them so dominant in Chamaeleon I. It takes a far more intense star-forming region to produce higher-m*** stars.
It’s possible to understand Chamaeleon I’s properties a little better by understanding its location.
Our Sun and solar system are currently p***ing through a region of space called the Local Bubble. This is an area of space where gas in the interstellar medium is relatively sparse, with an overall low density.
This region was evacuated within the past 20 million years by numerous supernovae explosions, the shockwaves of which blew away much of the molecular gas in their vicinity, creating a bubble in the interstellar medium with a lower density than its surroundings.
The Chamaeleon Complex sits on the surface of this bubble, where the supernova shockwaves have buffeted its denser gas and prompted it to eventually begin forming stars.
There’s also the Chamaeleon II and III dark clouds, but these currently show little active star birth and no active star formation, respectively. They therefore remain dark and inert.
It seems all the artistry is to be found in Chamaeleon I.
