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See Astonishing Milky Way Mosaic Image That Took 12 Years to Create

A Finnish astrophotographer created the 1.7 gigapixel image by stitching together photos with a total exposure time of roughly 1,250 hours

A mosaic image of our Milky Way galaxy created over the course of nearly 12 years. (J-P Metsavainio)
smithsonianmag.com

Finnish astrophotographer J.P. Metsavainio spent nearly 12 years capturing and piecing together the undulating sweep of our very own Milky Way galaxy in astonishing detail. After all those years of work, Metsavainio has now posted the image and some of its more captivating sub-sections on his website.

Mosaic image of Milky Way galaxy
A mosaic image of our Milky Way galaxy created over the course of nearly 12 years. (J-P Metsavainio)

The final image is a 100,000-pixel-wide, 1.7-gigapixel mosaic made up of 234 individual panels that Metsavainio painstakingly stitched together in Photoshop, using the location of stars to align the individual exposures, reports Michael Zhang for PetaPixel. Metsavainio shot the photos that went into his galactic mosaic using modified camera lenses and telescopes from his observatory in northern Finland, close to the Arctic Circle, reports Eoin McSweeney for CNN.

Spanning 125 degrees of the night sky, the mosaic encompasses swirling clouds of luminous gases and some 20 million stars from the constellation Taurus all the way to Cygnus.

Milky Way galaxy
The orientation of the final mosaic within the night sky. (J-P Metsavainio)

“I think this is the first image ever showing the Milky Way in this resolution and depth at all three color channels (H-a, S-II, and O-III),” Metsavainio tells PetaPixel.

Achieving such depth and color when photographing particularly distant or dim interstellar subjects required extra-long exposures. For example, Metsavainio writes on his blog that a supernova remnant called the Cygnus Shell required roughly 100 hours with the camera’s shutter open to capture enough light to render the image. Another faint supernova remnant in Cygnus took more than 60 exposure hours, he writes. The project’s total exposure time comes in at a whopping 1,250 hours.

The California Nebula (NGC 1499)
The California Nebula (NGC 1499) section of the mosaic. (J-P Metsavainio)

The glowing colors in the composition come from ionized gases, with hydrogen in green, sulfur in red and oxygen in blue, reports Michelle Starr for Science Alert. Prints of Metsavainio’s artwork are available for purchase online.

Of course, even in the fantastic detail provided by this new image, we can’t see the Milky Way in its totality from Earth. For instance, the 20 million stars in Metsavainio’s work may seem like a lot but they’re just a fraction of the estimated 100 billion balls of hot gas lighting up our galaxy.

Under ideal conditions, we see the Milky Way as an ethereal band in the sky, but the Milky Way is actually what is known as a barred spiral galaxy, meaning it’s a swirling, multi-armed disc with a bar-shaped center. So, when we are looking up, our position inside one of the disc’s arms means we’re just glimpsing the leading edge of a grand galactic spiral that measures approximately 100,000 light years across.

Unless space travel at the speed of light becomes a thing, we’re unlikely to ever get a top-down image of the whole galaxy. But, in the meantime, Metsavainio’s 100,000-pixel-wide epic still offers plenty to gape at.

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