The Horsehead Nebula in Infrared

Sometimes a horse of a different color hardly seems to be a horse at all, as, for example, in this newly released image from NASA's Spitzer Space Telescope. The famous Horsehead nebula makes a ghostly appearance on the far right side of the image, but is almost unrecognizable in this infrared view. In visible-light images, the nebula has a distinctively dark and dusty horse-shaped silhouette, but when viewed in infrared light, dust becomes transparent and the nebula appears as a wispy arc.

The Horsehead is only one small feature in the Orion Molecular Cloud Complex, dominated in the center of this view by the brilliant Flame nebula (NGC 2024). The smaller, glowing cavity falling between the Flame nebula and the Horsehead is called NGC 2023. These regions are about 1,200 light-years away.

The two carved-out cavities of the Flame nebula and NGC 2023 were created by the destructive glare of recently formed massive stars within their confines. They can be seen tracing a spine of glowing dust that runs through the image.

The Flame nebula sits adjacent to the star Alnitak, the westernmost star in Orion's belt, seen here as the bright blue dot near the top of the nebula.

In this infrared image from Spitzer, blue represents light emitted at a wavelength of 3.6-microns, and cyan (blue-green) represents 4.5-microns, both of which come mainly from hot stars. Green represents 8-micron light and red represents 24-micron light. Relatively cooler objects, such as the dust of the nebulae, appear green and red. Some regions along the top and bottom of the image extending beyond Spitzer's observations were filled in using data from NASA's Wide-field Infrared Survey Explorer, or WISE, which covered similar wavelengths across the whole sky.

Image credit: NASA/JPL-Caltech

Note: For more information, see Horsehead of a Different Color.

Star Formation in Messier 78

Astronomers have discovered some of the youngest stars ever seen thanks to the Herschel space observatory, a European Space Agency mission with important NASA contributions. Dense envelopes of gas and dust surround the fledging stars known as protostars, making their detection difficult until now. The discovery gives scientists a window into the earliest and least understood phases of star formation.

The new results come from the Herschel Orion Protostar Survey (HOPS), led by the University of Toledo. HOPS has looked at the vast stellar nursery in the Orion Molecular Cloud Complex, the biggest site of star formation near our solar system, located in the constellation of Orion.

A portion of the survey is shown here in two side-by-side images of the same region around the nebula Messier 78 where several of 15 new protostars were found. Herschel detected the extremely young protostars -- indicated in the image by the four circles -- that were too cold to be picked up in previous scans of the area by NASA's Spitzer Space Telescope. Radio wave observations from the Atacama Pathfinder Experiment (APEX) telescope in Chile, a collaboration between the Max Planck Institute for Radio Astronomy in Germany, the Onsala Space Observatory in Sweden and the European Southern Observatory in Germany, further confirmed the newfound protostars' presence.

On the left, the nebula Messier 78 is shown in a three-color composite from the three telescopes just mentioned. In green is the 160-micron, far-infrared light collected by Herschel's Photodetector Array Camera and Spectrometer (PACS). Appearing in blue is 24-micron light from Spitzer. Finally, 870-micron radio wave light gathered by APEX glows red.

On the right the same region appears in a separate three-color composite that shows infrared observations from two instruments aboard NASA's Spitzer Space Telescope. Blue represents 3.6- and 4.5-micron light and green shows light of 5.8 and 8 microns, both captured by Spitzer's Infrared Array Camera (IRAC). Red is 24-micron light detected by Spitzer's Multiband Imaging Photometer (MIPS).

Image credit: NASA/ESA/ESO/JPL-Caltech/Max-Planck Institute for Astronomy

Note: For more information, see Herschel Discovers Some of the Youngest Stars Ever Seen.

Messier 42 - The Orion Nebula

The Orion nebula is featured in this sweeping image from NASA's Wide-field Infrared Survey Explorer, or WISE. The constellation of Orion is prominent in the evening sky throughout the world from about December through April of each year. The nebula (also cataloged as Messier 42) is located in the sword of Orion, hanging from his famous belt of three stars. The star cluster embedded in the nebula is visible to the unaided human eye as a single star, with some fuzziness apparent to the most keen-eyed observers. Because of its prominence, cultures all around the world have given special significance to Orion. The Maya of Mesoamerica envision the lower portion of Orion, his belt and feet (the stars Saiph and Rigel), as being the hearthstones of creation, similar to the triangular three-stone hearth that is at the center of all traditional Maya homes. The Orion nebula, lying at the center of the triangle, is interpreted by the Maya as the cosmic fire of creation surrounded by smoke.

This metaphor of a cosmic fire of creation is apt. The Orion nebula is an enormous cloud of dust and gas where vast numbers of new stars are being forged. It is one of the closest sites of star formation to Earth and therefore provides astronomers with the best view of stellar birth in action. Many other telescopes have been used to study the nebula in detail, finding wonders such as planet-forming disks forming around newly forming stars. WISE was an all-sky survey giving it the ability to see these sites of star formation in a larger context. This view spans more than six times the width of the full moon, covering a region nearly 100 light-years across. In it, we see the Orion nebula surrounded by large amounts of interstellar dust, colored green.

Astronomers now realize that the Orion nebula is part of the larger Orion molecular cloud complex, which also includes the Flame nebula. This complex in our Milky Way galaxy is actively making new stars. It is filled with dust warmed by the light of the new stars within, making the dust glow in infrared light.

Color in this image represents specific infrared wavelengths. Blue represents light emitted at 3.4-micron wavelengths and cyan (blue-green) represents 4.6 microns, both of which come mainly from hot stars. Relatively cooler objects, such as the dust of the nebulae, appear green and red. Green represents 12-micron light and red represents 22-micron light.

Image credit: NASA/JPL-Caltech/UCLA

Note: For more information, see WISE Feels the Heat from Orion's Sword.

Herbig-Haro Objects in the Orion Complex

This image from the Kitt Peak National Observatory (KPNO) 4-meter telescope shows a roughly 1/2-degree square region of the sky in the constellation of Orion (about the same size as the diameter of the full Moon). This is a small part of the Orion Molecular Cloud Complex, a giant region of gas and dust undergoing active star formation some 1,500 light-years away.

Numerous small knots known as Herbig-Haro Objects, labeled here in white, are signatures of recently formed stars ejecting material into space. The three HH objects labeled in green have been subjects of intense study by the NASA/ESA Hubble Space Telescope over several years, resulting in a better understanding of how the material ejected from stars interacts with the surrounding medium.

Photo credit: Z. Levay (STScI), T.A. Rector (University of Alaska Anchorage), and H. Schweiker (NOAO/AURA/NSF)

Nebulae in Orion

This mosaic image taken by NASA's Wide-field Infrared Survey Explorer, or WISE, features three nebulae that are part of the giant Orion Molecular Cloud. The image covers an area of the sky about three times as high and wide as the full moon (1.5 by 1.8 degrees). Included in this view are the Flame Nebula, the Horsehead Nebula and NGC 2023.

Despite its name, there is no fire roaring in the Flame Nebula. What makes this nebula shine is the bright blue star seen to the right of the central cloud. This star, Alnitak, is the easternmost star in Orion's belt. Wind and radiation from Alnitak blasts away electrons from the gas in the Flame Nebula, causing it to become ionized and glow in visible light. The infrared glow seen by WISE is from dust warmed by Alnitak's radiation. Also known as NGC 2024 and Orion B, this nebula is classified as a molecular cloud.

The famous Horsehead Nebula appears in this image as a faint bump on the lower right side of the vertical dust ridge. In visible light, this nebula is easily recognizable as a dramatic silhouette in the shape of a horse's head. It is classified as a dark nebula because the dense cloud blocks out the visible light of the glowing gas behind it. WISE's infrared detectors can peer into the cloud to see the glow of the dust itself.

A third nebula, called NGC 2023, can be seen as a bright circle in the lower half of the image. NGC 2023 is classified as a reflection nebula, meaning that the dust is reflecting the visible light of nearby stars. But here WISE sees the infrared glow of the warmed dust itself.

Color in this image represents specific infrared wavelengths. Blue represents light emitted at 3.4-micron wavelengths, mainly from hot stars. Relatively cooler objects, such as the dust of the nebulae, appear green and red. Green represents 4.6-micron light and red represents 12-micron light.

This image was made from data collected after WISE began to run out of its supply of solid hydrogen cryogen in August 2010. Cryogen is a coolant used to make infrared detectors more sensitive. WISE mapped the entire sky by July using four infrared detectors, but during the period from August to October, 2010, while the cryogen was depleting, WISE had only three detectors operational, and the 12-micron detector was less sensitive. This turned out to be a good thing in the case of this image, because the less-sensitive detector reduced the glare of the Flame portion of the nebula enough to bring out details of the rest of the nebula.

Photo credit: NASA/JPL-Caltech/UCLA

The Planck Microwave Sky with Highlighted Galaxies

Emission from gas and dust in the plane of the Milky Way dominates this multi-color all-sky image of the microwave sky, synthesized using data spanning the full frequency range of Planck, which covers the electromagnetic spectrum from 30 to 857 GHz.

Other galactic features recognizable in the image are the Galactic Center and the giant molecular clouds of Perseus and Orion, both of which are extremely active regions of star formation.

The Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC), two small satellite galaxies of the Milky Way which are also among our Galaxy's closest neighbors are clearly visible, as is the spiral galaxy M31, or Andromeda, the largest galactic neighbor of the Milky Way. The LMC lies at a distance of about 160,000 light-years from the Sun, the SMC at about 200,000 light-years and M31 at about 2.5 million light-years. All three objects, along with the Milky Way and several other galaxies, belong to the Local Group of galaxies.

In addition, Planck's ability to detect hundreds of extragalactic radio sources, both nearby and distant, is clearly evident in this image - two examples are highlighted in the northern hemisphere. Centaurus A, the most nearby giant elliptical galaxy, located about 12 million light-years away from us, is visible just above the Galactic Plane; this galaxy has an active galactic nucleus, with intense radio emission arising from jets of plasma and lobes of high-energy particles emanating from its central, supermassive black hole. Also, 3C 273, a bright radio source located at redshift z~0.15 (corresponding to a distance of about 2 thousand million light-years away) can be seen towards the northern Galactic Pole.

Photo credit: ESA, HFI and LFI consortia