APOD: The Double Cluster in Perseus (2023 Jul 07)

[APOD Robot]

The Double Cluster in Perseus

Explanation: This pretty starfield spans about three full moons (1.5 degrees) across the heroic northern constellation of Perseus. It holds the famous pair of open star clusters, h and Chi Persei. Also cataloged as NGC 869 (top) and NGC 884, both clusters are about 7,000 light-years away and contain stars much younger and hotter than the Sun. Separated by only a few hundred light-years, the clusters are both 13 million years young based on the ages of their individual stars, evidence that they were likely a product of the same star-forming region. Always a rewarding sight in binoculars, the Double Cluster is even visible to the unaided eye from dark locations.

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[Ann]

The Double Cluster in Perseus
Image Credit & Copyright: Mårten Frosth

By far the most interesting thing about this APOD is all the red nebulosity it reveals, mostly in the right-hand part of the image, but also "below" the two clusters. The Double Cluster in Perseus must have been born from a gigantic gas cloud, but the overwhelming majority of pictures of them reveals no trace of any gas surrounding them. In this APOD, however, we can indeed see remnants of this gas cloud as red ionized hydrogen.

I googled "Double Cluster in Perseus", and found so many pictures of the Double Cluster without any surrounding nebulosity. But lo and behold, there were indeed a few pictures that showed red gas surrounding the clusters. The best one I found is this one:

The Double Cluster and surrounding nebulosity.
Credit: WilliamsSeaAndSky.com

In the picture by WilliamsSeaAndSky.com (and you should really check out the full version of it here), you can see how the furious stellar winds and onslaught of ultraviolet photons from the massive hot stars have blown away the gas from within, away from stars. Barely any gas at all appears to reside in the clusters themselves, but there is gas - very thin and attenuated gas, to be sure - all around the clusters. This gas, this red nebulosity, is the remnant of the gas cloud that once gave birth to the two titanic clusters.

The red hydrogen alpha nebulosity surrounding the two giant clusters is slightly similar to the almost unthinkably hot gas surrounding "dead", non-starforming galaxy clusters. While the red hydrogen alpha nebulosity surrounding the Double Cluster has been ionized by ultraviolet radiation, the extremely hot gas surrounding galaxy clusters has been heated to millions of degrees by the enormous jets from the supermassive black holes in the largest of the galaxies in galaxy clusters.

The jet of matter is ejected from M87 at nearly the speed of light, and stretches 1.5 kpc (5,000 light-years) from the galactic core. Credit: NASA and The Hubble Heritage Team (STScI/AURA)

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In this X-ray (Chandra) and radio (VLA) composite image, hot matter (blue in X-ray) from the Virgo cluster falls toward the core of M87 and cools, where it is met by the relativistic jet (orange in radio), producing shock waves in the galaxy's interstellar medium. Credit: X-ray: NASA/CXC/KIPAC/N. Werner et al Radio: NSF/NRAO/AUI/W. Cotton

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Gas is driven out of the largest galaxies with the largest black holes, and this gas is heated to millions of degrees by the tremendous jets of the black holes. Large galaxy clusters are typically surrounded by this super-hot gas.

A massive, young galaxy cluster seen in X-rays (blue), visible light (green), and infrared light (red). Image: X-ray: NASA/CXC/Univ of Missouri/M.Brodwin et al.; optical: NASA/STScI; infrared: JPL/CalTech

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Can't resist showing you a picture of filaments in the cosmic web that I have posted before. Do note the long strands of light blue-colored gas that has been driven out of the golden-colored galaxies:

Clusters of galaxies line up in filaments. Note the light blue-colored gas that has been driven out of the galaxies. Image credit: TNG COLLABORATION.

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The fact that gas is driven out of star clusters and individual galaxies in galaxy clusters mostly prevents further star formation there.

Ann

[Chris Peterson]

By far the most interesting thing about this APOD is all the red nebulosity it reveals, mostly in the right-hand part of the image, but also "below" the two clusters. The Double Cluster in Perseus must have been born from a gigantic gas cloud, but the overwhelming majority of pictures of them reveals no trace of any gas surrounding them.

I've been pushing my own imaging deeper lately, with multiple hour exposures of fairly common, fairly bright objects, taking advantage of processing techniques that allow for pushing up the very low levels without completely blowing out the brighter parts. And I'm finding that there are a lot of clouds of glowing hydrogen out there (and faint dust, too) that we don't usually see.

[orin stepanek]

No; you're not seeing double; It is a beauty!

Dark secluded spot!

[oliviamoncrief]

Actually, the Double Cluster in Perseus is a beautiful and popular celestial object located in the constellation of Perseus. It is a pair of open star clusters, known as NGC 869 and NGC 884, that are located relatively close to each other in the night sky.
NGC 869 and NGC 884 are both young star clusters that are estimated to be around 12.8 million years old. They are located at a distance of approximately 7,500 light-years from Earth and are visible to the naked eye as a faint fuzzy patch in the night sky.

[johnnydeep]

Actually, the Double Cluster in Perseus is a beautiful and popular celestial object located in the constellation of Perseus. It is a pair of open star clusters, known as NGC 869 and NGC 884, that are located relatively close to each other in the night sky.
NGC 869 and NGC 884 are both young star clusters that are estimated to be around 12.8 million years old. They are located at a distance of approximately 7,500 light-years from Earth and are visible to the naked eye as a faint fuzzy patch in the night sky.

Ok, the numbers you provide differ a bit from the APOD text. Is that what you are pointing out, or is it something else I'm failing to see?

[mariahcarey]

Actually, the Double Cluster in Perseus is a beautiful and popular celestial object located in the constellation of Perseus. It is a pair of open star clusters, known as NGC 869 and NGC 884, that are located relativelywordle close to each other in the night sky.
NGC 869 and NGC 884 are both young star clusters that are estimated to be around 12.8 million years old. They are located at a distance of approximately 7,500 light-years from Earth and are visible to the naked eye as a faint fuzzy patch in the night sky.

The Double Cluster in Perseus is one of the most beautiful star clusters in the night sky and a personal favorite DSO I enjoy looking at through my telescope