Astronomers using the United Kingdom Infrared Telescope (UKIRT) in
Hawaii, the IRAM Millimeter-wave Telescope in Spain, and the Spitzer
Space Telescope in orbit above the Earth, have completed the most
wide-ranging census ever produced of dynamical star formation in and
around the well-known Great Nebula of Orion. They have found this
stellar nursery to be a lively and somewhat overcrowded place, with
young stars emitting gas jets in all directions, creating quite a
chaotic picture. There is much more going on in Orion than previously
thought.

The research team comprises more than a dozen astronomers from the US,
the UK and a number of other European countries. The project thus has
a truly international flavor, representing a collaboration of minds
from across the globe. A number of them are in Hertfordshire in the UK
this week to share their discoveries with colleagues at this year’s
annual National Astronomy Meeting of the UK (NAM 2009).

Take a look at the constellation of Orion at night. With the naked eye
you see only the brightest stars, like Betelgeuse and Rigel at the
shoulder and knee of the constellation, or perhaps the Orion Nebula as
a vaguely fuzzy patch around the sword. What your eye does not see is
an enormous cloud of molecules and dust particles that hide a vast
region where young stars are currently being born. On the sky, the
region — known to astronomers as the Orion Molecular Cloud — is more
than 20 times the angular size of the full moon, spanning from far
above the hunter’s head to far below his feet. It is one of the most
intense regions of star formation in the local Milky Way and has been
the subject of many small-scale studies over the years. However, the
current work is the first to present such a complete study of the
young stars, the cloud of gas and dust from which they are being born,
and the spectacular supersonic jets of hydrogen molecules being
launched from the poles of each star.

This spectacular image combines observations from the United Kingdom Infrared Telescope and the Spitzer Space Telescope. It shows just a small portion of the region surveyed. In this figure, parts of the Orion Molecular cloud are illuminated by nearby stars and therefore glow an eerie green colour. The jets punch through the cloud and can be seen as a multitude of tiny pink-purple arcs, knots and filaments. The young stars that drive the jets are usually found along each jet and are coloured golden orange. Credit: UKIRT/JAC, Spitzer Telescope.

Most of the “action” is hidden from view in visible light, because the
molecular cloud is very thick and opaque. Only the Orion nebula, which
is really just a blister on the surface of the cloud, gives an
indication of what is really happening within. To see through the
cloud, we need to observe at wavelengths beyond the reach of the human
eye. The longer (or “redder”) the wavelength, the better! Thus, the
team have used UKIRT on Mauna Kea, the Spitzer Space Telescope, which
works at even longer “mid-infrared” wavelengths, and the IRAM radio
telescope, which operates beyond the infrared at short radio
wavelengths.

The key to the success of this project was the combination of data
from all three facilities. Inspired by the richness of his images from
UKIRT, Chris Davis contacted colleagues in Europe and on the U.S.
Mainland. Tom Megeath, an astronomer from the University of Toledo,
provided a catalogue of the positions of the very youngest stars –
sources revealed only recently by the Spitzer Space Telescope. Thomas
Stanke, a researcher based at the European Southern Observatory in
Garching, Germany, then provided extensive IRAM maps of the molecular
gas and dust across the Orion cloud. Dirk Froebrich, a lecturer at the
University of Kent, later used archival images from the Calar Alto
Observatory in Spain (data acquired by Stanke some 10 years ago) to
measure the speeds and directions of a large number of jets by
comparing them with their positions in the new images. Armed with
these data, Davis was able to match the jets up to the young stars
that drive them, as well as to density peaks within the cloud – the
natal cores from which each star is being created.

A close-up view of a spectacular jet (seen in red) popping out of a busy region of star formation in Orion. All of the red wisps, knots and filaments are in fact associated with jets from young stars, which in this figure are coloured orange. These data were acquired with the Wide Field Camera (WFCAM) at the United Kingdom Infrared Telescope. Credit: UKIRT/JAC.

Dr Davis says, “regions like this are usually referred to as stellar
nurseries, but we have shown that this one is not being well run: it
is chaotic and seriously overcrowded. Using UKIRT’s wide field camera
(WFCAM), we now know of more than 110 individual jets from this one
region of the Milky Way. Each jet is traveling at tens or even
hundreds of miles per second; the jets extend across many trillions of
miles of interstellar space. Even so, we have been able to pinpoint
the young stars that drive most of them.”

Dr Froebrich mentions that, “measuring the speeds and directions of
the jets is essential to pinpoint the driving sources, especially in
such crowded regions as M42 in Orion.”

Dr Megeath adds, “with such a large number of young stars, we can
study the “demographics” of star birth. This study will give us an
idea of how long it takes baby stars to bulk up by pulling in gas from
the surrounding cloud, what ultimately stops a star from growing
bigger, and how a star’s birth is influenced by other stars in the
stellar nursery.”

Dr Stanke notes, “Star formation research is fundamental to our
understanding of how our own sun, and the planets that orbit it, were
created. Many of the stars currently being born in Orion will evolve
to be just like the sun. Some may even have earth-like planets
associated with them.”

Dr Andy Adamson, Associate Director at the UKIRT, says, “This
spectacular dataset demonstrates the power of survey telescopes like
UKIRT. With on-line access to data from other telescopes around the
world, and the ease with which one can communicate with collaborators
across the globe, massive projects like the Orion study are very much
the future of astronomy.”

Professor Gary Davis, Director UKIRT, and Dr Adamson will present this
and other UKIRT science results at the European Week of Astronomy and
Space Science (NAM 2009) at the University of Hertfordshire today.