The northern hemisphere winter is upon us, and Orion the Hunter dominates the evening sky in the east. It's easy to spot, just look for 3 bright stars in an almost vertical line: these are Orion's belt; and his sword is the cluster of stars below and to the south of the belt. They may be just stars to the naked eye - but in fact the belt and sword region is a seething cauldron of of star-forming activity, swathed in massive dark clouds of gas and dust particles, .
My small telescope reveals the ghostly white cloud of the famous Orion Nebula around the stars of the sword, giving a hint that there is something interesting going on; but for the true story of what is happening, it pays to take a closer look.
Room to grow
The Hubble Telescope image above shows the wafting clouds of dense gas and dust that make up the nebula, with a number of small red stars peeping through, but at the bottom left we can also see a bright white star which has managed to open its own personal space. This bright star , LL Ori, has grown powerful enough to produce a fast out-flowing wind, carving a cavity in the clouds around it, and even producing a bow-wave in the clouds, like a ship forging through the sea.
Powerful jets
Stars are formed when a gas and dust cloud collapses in on itself, creating a very dense central core that then heats up enough to become one or more stars. In the early stages these 'protostars' are invisible to us, embedded deep within the thick gas and dust. They are busy gathering up material from the cloud, forming a disk around their middle, but at the same time they are losing material in the form of high speed jets from both poles. These jets smash into the surrounding clouds and the energy from the shock lights up the gas like a Christmas tree – revealing the location of the star even though the star is itself hidden.
This recently released image from the Gemini Observatory shows an astounding set of at least 6 jets all mixed up, which researchers believe are created by a tight cluster of young stars embedded deep in the Orion B cloud. This really is a stellar nursery!
Baby stars may be buried deep in dust and gas but astronomers have found a way of peering through the murk to get a peek.
Last year researchers using the ALMA telescope managed to get a view of the disks around two young stars in a binary system in another star-forming region – as you can see in this unusual image, one is viewed sideways with the disc across the sun; the other is viewed from above, with the disk around it like a halo. The dust in these disks can't be seen at visible wavelengths, but is detectable at the longer, sub-millimetre wavelengths that ALMA is specially designed for.
And there is more: astronomers believe that these disks around newly forming planets will eventually become planetary systems, and that our own solar system originated in a disk just like this. Studying young stars with disks like these ones could well open the door to greater understanding of how our own solar system came to be, and perhaps provide clues in the search for Earth-like planets orbiting other stars.
Star formation, including video clip of simulated cloud collapse and star birth
http://lasp.colorado.edu/education/outerplanets/solsys_star.php
1. NASA, ESA and the Hubble Heritage Team www.nasa.gov/multimedia/imagegallery/image_feature_2442.html
2. Gemini Observatory/AURA/B. Reipurth, C. Aspin, T. Rector www.gemini.edu/node/12429
3. R. Hurt (NASA/JPL-Caltech/IPAC) www.eso.org/public/news/eso1423/