The Orion Nebula -Messier 42 (M42/M43, NGC1976)

Credits: NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team

Believed to be the cosmic fire of creation by the Maya of Mesoamerica, M42 blazes brightly in the constellation Orion. Popularly called the Orion Nebula, this stellar nursery has been known to many different cultures throughout human history. The nebula is only 1,500 light-years away, making it the closest large star-forming region to Earth and giving it a relatively bright apparent magnitude of 4. Because of its brightness and prominent location just below Orion’s belt, M42 can be spotted with the naked eye, while offering an excellent peek at stellar birth for those with telescopes. It is best observed during January.

The Mayan culture’s likening of the Orion Nebula to a cosmic fire of creation is very apt. The nebula is an enormous cloud of dust and gas where vast numbers of new stars are being forged. Its bright, central region is the home of four massive, young stars that shape the nebula. The four hefty stars are called the Trapezium because they are arranged in a trapezoidal pattern. Ultraviolet light unleashed by these stars is carving a cavity in the nebula and disrupting the growth of hundreds of smaller stars.

This stunning Hubble image offers the sharpest view of the Orion Nebula ever obtained. Created using 520 different Hubble exposures taken in multiple wavelengths of light, this mosaic contains over one billion pixels. Hubble imaged most of the nebula, but ground-based images were used to fill in the gaps in its observations. The orange color in the image can be attributed to hydrogen, green represents oxygen, and the red represents both sulfur and observations made in infrared light.

This star chart for M42 represents the view from mid-northern latitudes for the given month and time.

Credits: Image courtesy of Stellarium

M42 is our closest example of an HII region, being composed mainly of ionized hydrogen which gives off the red glow so dominant in every picture of the nebula. Deep photographs such as this one show that it is nearly a degree across, larger than the full Moon (although the Moon is so bright that it looks much larger). The energy to keep the nebula glowing comes from the very hot young stars in a formation called the Trapezium, embedded in the brightest part of the nebula and not visible in this photograph. The nebula and the brighter stars are very young indeed by astronomical standards, at about 30000 years. Compare this to our own Sun, which is considered to be a middle-aged star at over four billion years! M42 probably contains several hundred stars younger than a million years, still bursting with the energy of youth. Stars are still being born in a dense cloud behind the nebula, but they are hidden from our view by a concentration of dust which reduces their light to only a million-millionth of its original intensity. Fortunately, astronomers have developed special cameras and other detectors which are sensitive to infra-red radiation, more popularly known as heat, which penetrates the dust and reveals to us this stellar nursery.

Although M42 is mostly hydrogen, in both neutral and ionized states, with a fair quantity of dust, it does contain significant amounts of other elements, especially oxygen. The green glow of doubly-ionized oxygen is strongest near the intense ultraviolet starlight at the middle of the nebula. To the north-east (the upper left in this picture) is a feature called the Dark Bay, which is a thick cloud of neutral gas which has not yet been ionized.

About The Object
Object Name	Orion Nebula , M42, NGC 1976
Object Description	Emission Nebula
R.A. Position	05h 35m 17.0s
Dec. Position	-5° 23' 27.99"
Distance	The distance to the Orion Nebula is 1,500 light-years (460 parsecs).
Dimensions	The image is 30 arcminutes (13 light-years or 4.0 parsecs) square.
About The Data
Data Description	The Hubble image was created from HST data from proposal 10246: M. Robberto (STScI/ESA), C.R. O'Dell (Vanderbilt University), L.A. Hillenbrand (Caltech), M. Simon (SUNY Stony Brook), P. McCullough (STScI), J. Krist (Jet Propulsion Laboratory), F. Palla (Osservatorio Astrofisico di Arcetri), M. Romaniello (ESO – Germany), J. Najita (NOAO/AURA), E.D. Feigelson (The Pennsylvania State University), R. Makidon (STScI), J. Stauffer (Jet Propulsion Laboratory); N. Panagia, I.N. Reid, D.R. Soderblom, and E. Bergeron (STScI); and K.G. Stassun (Vanderbilt University). The Hubble data was superimposed onto a ground-based image taken from the 2.2-meter telescope at the European Southern Observatory – La Silla.
Instrument	HST>ACS and ESO-La Silla >2.2 meter telescope/WFI
Exposure Dates	October 2004 - April 2005 (ACS), and December 11, 2001 (WFI)
Filters	ACS: F435W (B), F555W (V), F658N (Halpha), F775W (i), and F850LP (z) ESO: BB#B/99_ESO842 B, NB#OIII/8_ESO859 [O III], ESO NB#Halpha/7_ESO856, and ESO NB#SIIr/8_ESO857 [S II]
About The Image
Color Info	This image is a composite mosaic of many separate exposures made by the ACS instrument on the Hubble Space Telescope and the ESO La Silla 2.2 meter telescope using several different filters isolating the light of specific elements or of specific broad wavelength ranges. The colo r arises by assigning different hues (colors), to each monochromatic image. In this case, the colors are: Blue: ACS F435W (B) + ESO BB#B/99_ESO842 B Green: ACS F555W (V) + ESO NB#OIII/8_ESO859 [O III] Red-orange: ACS F658N (Halpha) Red: ACS F775W (i) + F850LP (z) + ESO NB#Halpha/7_ESO856 + ESO NB#SIIr/8_ESO857 [S II]