October 31, 2014

Astro-Event of the Week: 05.18.09: Spot a Hubble Classic!

Eagle Nebula.

A close up shot of one of the pillars. (Credit: APOD/NASA/Hubble Hertitage Team/STS.I/AURA). 

As all eyes are now in orbit following the intrepid crew of the shuttle Atlantis as they carry out the final repairs to the Hubble Space Telescope, now is a good time to track down one of its classic targets. One of Hubble’s most enduring photographs is that of the Eagle Nebula. Our challenge to you is to try and spy this illusive nebula. A broad, emission nebula in the constellation Serpens, this also has the multiple designations of M16 in the messier catalog and NGC 6611. Many folks, even seasoned amateurs, have never viewed this extraordinary object. It is embedded in a rich star field along the galactic plane, and will begin riding high to the south around mid-summer evenings for northern hemisphere observers. Currently, it rises in the east around midnight, so early mornings are your best bet. As the Moon wanes out of the morning sky, an astronomers’ fancy frequently turns towards deep sky objects such as M16. And the darker, less light polluted your site, the better! M16 is a fine target for apertures of 6″ or greater; also allow for a generous amount of field of view to see the surrounding nebulosity. Try this target with an assortment of filters, and long exposure photography will bring out more detail. Don’t expect your view to equal Hubble’s: at a distance of 7,000 light years, it’s a churning cradle of active stellar birth. Some debate has ensued as of late as to whether these “pillars of creation” exist any longer or have since been dissipated. Never the less, the view provides a fascinating snapshot into early star formation! Coordinates for the Eagle Nebula are:

Declination: -13° 49′

Right Ascension: 18Hours 18′ 48″

This week’s Astro-term of the Week is  emission nebula. Emission nebulae (plural) are clouds of dust and gas that are being lit from within, like a paper lantern. The diffuse gases associated with these nebulae are becoming ionized, causing them to glow. Some are lit by the death throes of stars, such as the Ring Nebula (M57) in Lyra, others, such as M16 or the Pleiades, are being illuminated by new, upstart stars. Compare these to dusky Bok globules or the dark lanes mottling the summer Milky Way. Incidentally, the surface brightness of emission nebula can be somewhat misleading. For example, the magnitude of the Eagle Nebula is usually given as +6, about the limit of the naked eye under dark skies. Keep in mind, however, that this is spread out over a surface area about 7 arc minutes across. Needless to say, the Eagle nebula is a tougher target visually than a +6 magnitude star, but as with much of astronomy, part of the essence of “coolness” is knowledge of what you’re looking at. Good luck and dark skies!

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