The Large Magellanic Cloud (LMC) is an irregular dwarf galaxy and a companion to our own Milky Way Galaxy. Unlike spiral and elliptical galaxies, irregular galaxies lack any appearance of organized structure. Like its neighboring Small Magellanic Cloud (SMC), the LMC appears as a huge and diffuse cloud in the southern nighttime sky. Both of these galaxies are named in honor of the explorer Ferdinand Magellan, who noted their presence in becoming the first to sail around the world nearly 500 years ago.
To fully appreciate the grandeur of the LMC, you should note that the field of view of the images in this gallery is 4.5 degrees on a side, or nine times the diameter of a full Moon. While considered dwarf galaxies, their close proximity means that the Magellanic Clouds subtend a large angle on the sky. The Magellanic Clouds and the Milky Way are members of the Local Group, a collection of about 30 galaxies loosely bound by their mutual gravitation.
Visible: DSS, Visible: AAO/Malin and Near-Infrared: 2MASS
The visible-light images (above, left and center) reveal the diffuse and fuzzy nature of the LMC. In neither case can you define a clear center to the galaxy. The color image is a composite of three images (using B, V and R filters) taken with long exposures of 40-60 minutes. The color image is obviously more sensitive then the black-and-white DSS image. Moreover, the red filter easily identifies the supergiant H II regions, regions where the hydrogen is ionized by the ultraviolet and visible light from newborn stars. The most prominent of these regions is known as 30 Doradus, or the Tarantula Nebula, located to the east and north (left and top) of the image center. The near-infrared photograph (above right) is a short exposure, and bears a resemblance to the DSS visible-light image. At these wavelengths, we are seeing primarily the older and redder stars in the LMC. The core of the Tarantula Nebula can barely be discerned.
Mid-Infrared: MSX, and Far-Infrared: IRAS
These infrared images (above) were obtained at longer IR wavelengths. The mid-infrared photo was obtained at 6-11 microns, or about ten times the wavelengths of visible light. The photos were taken by the Midcourse Space Experiment (MSX), a military satellite. The small infrared telescope aboard this 1996-1997 satellite spent most of time its time studying infrared backgrounds near the limb of the Earth, but also devoted roughly ten percent of its observing time to mapping the plane of the Milky Way Galaxy and other selected regions of astronomical interest. In addition to the Tarantula Nebula, numerous other regions of glowing gas can be seen in the mid-infrared. These are areas of ongoing and future star formation. The far-infrared mosaic is composed of images obtained at 12, 25, and 60 microns by the Infrared Astronomical Satellite (IRAS) in 1983. This spectacular image has been mathematically enhanced to improve the effective spatial resolution. The redder colors represent longer wavelength emission, and show infrared emission from interstellar dust. The bluer colors correspond to shorter wavelengths and help to identify individual stars. The streaks emanating in a radial pattern from the bright Tarantula Nebula are an artifact of data processing.
Radio: Parkes, and Far-Infrared: IRAS
This pair of images contrasts the radio emission from the LMC (above left) with the previously studied far-infrared mosaic. The image was obtained at a wavelength of 21.4 cm using the 64-m diameter Parkes Radio Telescope in Australia. The dominant feature in this low-resolution image, false-colored as red, is again the Tarantula Nebula. The distribution of far-infrared and radio emission in galaxies is often similar, since they portray different evolutionary phases of the same stellar population: massive stars. The infrared light results from heating of dust grains by young stars, while the radio luminosity results from synchrotron emission resulting from supernova explosions. You should be able to discern similarities between the pattern of red knots in the radio image and the brightest regions of infrared image in the IRAS mosaic.
UV: Sounding Rocket and Mid-Infrared: MSX
In this pairing, we compare the ultraviolet photograph (above left) with the previously examined mid-infrared data. The UV data were obtained in a sounding rocket experiment, in which a small rocket carried the science payload to an altitude of 50-160 km for about 5 minutes, before it returns to Earth. Such low-cost rockets are useful for exploring the Universe at altitudes that cannot be reached by balloon-based experiments. In the UV image, the Tarantula Nebula is located within the yellow box. Newborn stars emit large amounts of ultraviolet light, and hence the UV image nicely traces the distribution of star-forming regions in the LMC. Many of these areas are also bright in the mid-infrared, where the UV light has been absorbed and re-radiated by dust grains.
X-Ray: ROSAT and Radio: Parkes
Finally, we compare the x-ray image with the previously examined radio wave photograph. Both are of relatively low spatial resolution. The Tarantula Nebula is buried within a broad region of extended x-ray emission denoting very hot interstellar gas within the LMC. X-ray emission is also seen from discrete point sources, many of which are supernova remnants. Another phenomena that can account for some of the point sources are X-ray binaries. These are a special class of binary star system, where one of the members is a neutron star. The intense gravity of the neutron star sucks gaseous material off of the companion star and heats it to millions of degrees, thereby creating x-rays. For additional information about x-ray binaries, please visit this site.