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Daily Space: The North American Nebula

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Most of the time, when looking at item imaged by a telescope, the reaction is to assume that the item being viewed looks pretty small to the naked eye. Except the image above is actually about eight times as wide as the full Moon — and it’s not even capturing the whole nebula. The entirety of the North American Nebula spans an apparent space greater than 10 full Moons, and that’s before brining in the closely connected Pelican Nebula. These are enormous features that span huge swathes of the night sky.

So why don’t they dominate the view every time we look up? Well, they’re large, but dim. The brightest points of the nebula actually hit a magnitude of 4, making them fairly easy to spot for someone with good eyesight in dark conditions. However, most of the nebula is several times dimmer, with a magnitude of 11 or higher (for astronomy, high numbers mean a dimmer object). The full span of the nebula is invisible, even in the best conditions.

The North American Nebula is named for an appearance that is said to resemble a map of the continent which … maybe. It would take a lot of squinting. Keep in mind that the image above is just a part of the whole nebula and that more detail could be revealed by a longer exposure. It’s an emission nebula, a cloud of ionized gas about 2,600 light years away that’s being lit by the energy of an enormously hot star that itself is almost hidden by the nebula.

But it’s big, and it’s up there, and it has an interesting history.

It was in 1783 that William Herschel first spotted what he called “a milky luminosity” at in the area of this nebula. Nebula were something of a specialty of Hershel. Considering that he cataloged over 2,000 nebula, but his son John only added this one to the catalog in 1829,........

© Daily Kos

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