Keyhole Nebula, Inside The Larger Carina Nebula

M63 // Sunflower Galaxy

NGC 1275 Multi-Wavelength

ESO 378-1

The Running Chicken Nebula.

Image Credit & Copyright: Andrew Campbell

Mercury is passing directly across the sun for the first time in nearly a decade.

The innermost planet of our solar system will look like a small, dark circle cutting across the sun’s disc. In the U.S., the transit began shortly after 7 a.m. ET on Monday and will continue for more than seven hours.

At least part of the transit, which only happens about 13 times every century, will be visible across the Americas, Europe, Africa and large portions of Asia.

If you’re hoping to watch it, eye protection is key. NASA stresses that “viewing this event safely requires a telescope or high-powered binoculars fitted with solar filters made of specially-coated glass or Mylar.”

You won’t be able to see the tiny dot of Mercury on its celestial crawl without magnification, NASA says.

Another option: Check out one of the multiple live-streaming events going on Monday. NASA says it will stream the transit here, here and here.

It’s not all about the show — transits like this one have historically been, and continue to be, important research opportunities for scientists. First observed in 1631, the transits were later used to “measure the distance between the Earth and the Sun,”NASA said.

Now, they provide scientists an opportunity to study the planets’ exospheres — the thin layer of gases that make up their atmosphere.

“When Mercury is in front of the sun, we can study the exosphere close to the planet,” NASA scientist Rosemary Killen said in a release from the Jet Propulsion Laboratory. “Sodium in the exosphere absorbs and re-emits a yellow-orange color from sunlight, and by measuring that absorption, we can learn about the density of gas there.”

Additionally, scientists have found that a transiting planet causes a drop in the sun’s brightness.

This phenomenon is “the main way we find planets outside the solar system,” NASA says.

The Kepler mission, which is searching for habitable planets, has found 1,041 planets to date using the transit method. The mission says it is able to determine the size of a planet by observing its transit.

Image Credit: NASA

TODAY IN HISTORY: The spectacular rings of Saturn, August 23, 1981, observed by the Voyager 2 space probe.

Comet Catalina Emerges : Comet Catalina is ready for its close-up. The giant snowball from the outer Solar System, known formally as C/2013 US10 tails, making it an impressive object for binoculars and long-exposure cameras. The featured image was taken last week from the Canary Islands, off the northwest coast of Africa. Sky enthusiasts around the world will surely be tracking the comet over the next few months to see how it evolves. via NASA

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Galaxy Ngc474

Just Another Milky Way Shot Taken From Death Valley, CA

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