It is called the Horsehead Nebula because of its distinctive shape, but now scientists have viewed it in a completely different light.
Astronomers have used Nasa’s Hubble Space Telescope to photograph the iconic nebula in a new, infrared light to mark the 23rd anniversary of the famous observatory’s launch aboard the space shuttle Discovery on April 24, 1990.
Looking like an apparition rising from whitecaps of interstellar foam, the iconic Horsehead Nebula has graced astronomy books ever since its discovery more than a century ago.
The nebula is a favorite target for amateur and professional astronomers.
It appears shadowy in optical light, but appears transparent and ethereal when seen at infrared wavelengths. The rich tapestry of the Horsehead Nebula pops out against the backdrop of Milky Way stars and distant galaxies that are easily visible in infrared light.
Hubble has been exploring space for more than two decades. During that time, it has benefited from a slew of upgrades from space shuttle missions, including the 2009 addition of a new imaging workhorse, the high-resolution Wide Field Camera 3 that took the new portrait of the Horsehead.
The nebula is part of the Orion Molecular Cloud, located about 1500 light-years away in the constellation Orion. The cloud also contains other well-known objects such as the Great Orion Nebula (M42), the Flame Nebula, and Barnard’s Loop.
It is one of the nearest and most easily photographed regions in which massive stars are being formed.
In the Hubble image, the backlit wisps along the Horsehead’s upper ridge are being illuminated by Sigma Orionis, a young five-star system just out of view. Along the nebula’s top ridge, two fledgling stars peek out from their now-exposed nurseries.
Scientists know a harsh ultraviolet glare from one of these bright stars is slowly evaporating the nebula. Gas clouds surrounding the Horsehead already have dissipated, but the tip of the jutting pillar contains a slightly higher density of hydrogen and helium, laced with dust. This casts a shadow that protects material behind it from being stripped away by intense stellar radiation evaporating the hydrogen cloud, and a pillar structure forms.
The Hubble Space Telescope is a project of international co-operation between NASA and the European Space Agency.
Nasa’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope.
In addition to Hubble’s view, the European Herschel space observatory also imaged the region surrounding the Horsehead Nebula in the far-infrared spectrum.
It shows in spectacular detail the scene playing out around the Horsehead Nebula at the right-hand side of the image, where it seems to surf like a “white horse” in the waves of turbulent star-forming clouds.
It appears to be riding towards another favourite stopping point for astrophotographers: NGC 2024, also known as the Flame Nebula. This star-forming region appears obscured by dark dust lanes in visible light images, but blazes in full glory in the far-infrared Herschel view.
Intense radiation streaming away from newborn stars heats up the surrounding dust and gas, making it shine brightly to Herschel’s infrared-sensitive eyes.
The panoramic view also covers two prominent sites of massive star formation to the northeast (left-hand side of this image), known as NGC 2068 (or M78) and NGC 2071. These take on the appearance of beautifully patterned butterfly wings, with long tails of colder gas and dust streaming away.
Both are reflection nebulas, so called because they reflect the light of nearby stars, revealing them even at visible wavelengths.