In this new Hubble Space Telescope view, the nebula appears in a new light, as seen in infrared wavelengths. The nebula, shadowy in optical light, appears transparent and ethereal when seen in the infrared, represented here with visible shades. The rich tapestry of the Horsehead Nebula pops out against the backdrop of Milky Way stars and distant galaxies that are easily seen in infrared light.
The Horsehead was photographed in celebration of the 23rd anniversary of the launch of Hubble aboard the space shuttle Discovery.
The backlit wisps along the Horsehead’s upper ridge are being illuminated by Sigma Orionis, a young five-star system just off the top of the Hubble image. A harsh ultraviolet glare from one of these bright stars is slowly evaporating the nebula. Along the nebula’s top ridge, two fledgling stars peek out from their now-exposed nurseries.
Gas clouds surrounding the Horsehead have already 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 photo-evaporated, and a pillar structure forms. Astronomers estimate that the Horsehead formation has about five million years left before it too disintegrates.
Oceanic phytoplankton blooms imaged from space by Envisat. Plankton blooms occur in regions of the ocean that have optimal temperature, sunlight, and nutrient supply for marine algae to grow exponentially. Most blooms are composed of coccolithophores, single celled organisms which grow disk-like exoskeletons of calcium carbonate. Trillions of these disks color the water white, showing the phytoplankton density and beautiful fluid dynamics of ocean currents.