Latest look beyond Orion's clouds forces star birth model rethink
An international team of astronomers
has succeeded in capturing the most comprehensive infrared view of
the famous Orion Nebula to date, highlighting a surprising amount of
failed stars and small planetary bodies. The image was
snapped using the European Southern Observatory's (ESO) Very Large Telescope (VLT) in conjunction with the infrared capabilities of the
observatory's High Acuity Wide-field K-band Imager (HAWK-I)
The Orion Nebula is located roughly 1,350 light-years from Earth, forming a part of the "sword" of the Orion constellation, and can be viewed by the naked eye as a small fuzzy patch on a clear night. We are able to observe the nebula without the aide of a telescope thanks to the large quantity of ultraviolet light thrown out by the stars embedded within it, which works to illuminate the surrounding clouds of gas and dust.
The HAWK-I mounted on the VLT operates in the near-infrared spectrum range, which allows the telescope to look past the nebula's choking clouds of interstellar material, and observe the stars and planetoids that are being created within. The ability to obtain an accurate count of these bodies represents a vital step towards gleaning an insight regarding the star formation processes that are thought to be taking place inside the 24 light-year wide Nebula.
It took the HAWK-I-augmented VLT several exposures to collect the light necessary to produce the stunning image. An analysis of the data indicated the presence of 10 times the amount of brown dwarfs and very-low-mass planetary objects than would be expected in line with current theories on star formation in the nebula.
Brown dwarfs are essentially substellar bodies that failed to gather enough mass during their formative period to sustain the nuclear fusion process raging at the heart of other main sequence stars.
The overabundance of these failed stars and low-mass planetary bodies has led the team to believe that there may be fewer active star formation regions at work within the Orion Nebula than had previously been believed. The discovery may help to constrain theories explaining how star formation unfolds within the stellar nursery.
One of the methods used to understand star creation is to observe nebulae such as Orion, and create a tally of the number of different bodies that are formed within via their masses. This cosmic inventory is known as an Initial Mass Function. By calculating the IMF of a star formation region, scientists are provided a solid basis on which to begin formulating theories regarding what processes could have occurred to create this ratio of bodies.
Due to the Orion Nebula's relative proximity to Earth, it has become a valuable proving ground used by astronomers to develop and test their star formation theories. The overabundance of brown dwarfs and low-mass planetary bodies skewing the IMF for the nebula will surely refine these models further, and by understanding how nearby nebulae form stars, we can gain a better comprehension of how their distant cousins do the same.
Unfortunately, present day observatories lack the ability to directly image the low-mass isolated planetoids. However, the completion of the ESO's planned European Extremely Large Telescope (E-ELT) will allow astronomers to further explore the enigmatic nebula-shrouded bodies.
The video below highlights the impressive depth of the new infrared image.