Brought to you by Hubble Space Telescope

Okay, let’s get back to exploring the cosmos here for a while.  Astronomers using the Hubble Space Telescope’s infrared capabilities took another look at one of the most iconic objects in the sky — the Horsehead Nebula. This cloud of gas and dust is one of my many favorites because its shape makes it look familiar, and at the same time, mysterious.  It’s a favorite target for amateur astronomers, and presents a fascinating look into nebula formation and dissolution for professional astronomers.

The Horsehead is part of the Orion Molecular Cloud, a part of the sky where massive stars are being formed. It lies about 1,500 light-years away from us in the direction of the constellation Orion. The OMC is huge, and has several fascinating regions such as the Great Orion Nebula, the Flame Nebula, and Barnard’s Loop.

Another of the space observatories, the Spitzer Space Telescope, has also peered into this region of space to study evidence of star formation in the nebula. So, it’s a popular place to explore, no matter what kind of telescope you use.

If you look at the Horsehead in optical light, the head of the horse stands out in sharp relief against the lighted-up clouds surrounding and behind it. The head of the horse itself is a dark cloud of gas and dust that appears murky to us.

Look at the same scene in infrared light, and it changes dramatically. Objects that emit light and heat in infrared wavelengths stand out, even though in visible light they are hidden.

In this lovely new Hubble image, the backlit wisps along the Horsehead’s upper ridge are being lit by a nearby star system called Sigma Orionis. It’s a collection of five young stars that are just out of the field of view here.  Along the nebula’s top ridge, two fledgling stars peek out from their now-exposed nurseries.

While the glare from nearby stars helps illuminate the cloud of gas and dust in this region, the ultraviolet radiation from those stars is also going to destroy the cloud and alter the familiar shape of the Horsehead.

The gas clouds surrounding the Horsehead already have dissipated, but the tip of the jutting pillar  in the center (that forms the neck of the Horse) is rich in hydrogen and helium and laced with dusty material.  That makes it more dense than the surrounding region and the pillar’s shadow works to protect material behind it from being eaten away by the intense radiation that is  evaporating the hydrogen cloud.  The best estimates from scientists give the Horsehead another five million years before it disintegrates completely.

There’s more in this picture than the Horsehead. If you click on the image above you’ll get a larger version of the same picture.  Examine it closely and you’ll some distant galaxies in the backdrop against which the Horsehead appears. Spend some time exploring this lovely image, which presents the Horsehead Nebula to us in a whole new light.  Read more about Hubble’s exploration of it here. 

Also, check out the lovely video visualization of the Horsehead, created by Greg Bacon, T. Davis, Lisa Frattare, Zolt Levay, and Frank Summers at the Space Telescope Science Institute. These guys are first-rate science visualizers!