Clusters Nebulae Galaxies

Double Cluster in Perseus on October evenings

Star chart of constellation Cassiopeia with an arrow pointing to 2 tiny dotted circles, labeled Perseus Double Cluster.
Here’s an easy way to use the prominent M or W shape of Cassiopeia to locate the Double Cluster in Perseus.

Double Cluster in Perseus

The Double Cluster in Perseus consists of two open star clusters near each other on the sky’s dome. Amateur astronomers know them as h Persei and chi Persei. The two clusters reside in the northern part of the constellation Perseus, quite close to the constellation Cassiopeia the Queen. If you have a dark sky and find Cassiopeia – which is easy, because the constellation has a distinctive M or W shape – be sure to look for Perseus, too. Then just scan between the two constellations with your binoculars for two glittering groups of stars. The Double Cluster – a breathtaking pair of open clusters, each containing supergiant suns – will be there.

These two star clusters are located about 7,500 light-years away. It’s amazing that we can see these stars at all across this great span of space. Plus, we know they must be bright stars, intrinsically, or we wouldn’t be able to see them. Each cluster contains a few hundred stars, and, indeed, these stars are young, hot supergiant suns that are many thousands of times more luminous than our sun.

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Astronomers tell us that the Double Cluster lies within the Perseus arm of the Milky Way galaxy. However, our solar system resides in the inner part of the Orion arm. Therefore, looking at the Double Cluster, we are looking through our local spiral arm and all the way to the next spiral arm outward from the galactic center.

How to find the Double Cluster in Perseus

To locate the Double Cluster, find the W- or M-shaped constellation Cassiopeia the Queen. If your sky is dark enough, you will be able to see the graceful pattern of Perseus the Hero nearby. Then scan between them with binoculars to find the Double Cluster.

Star chart showing location of the Perseus Double Cluster between constellations Cassiopeia and Perseus.
The Perseus Double Cluster is located between Cassiopeia and Perseus. Scan the area between them with binoculars and you’ll find the 2 glittering star clusters. Image via Stellarium.org. Used with permission.

Starting at mid-northern latitudes, the Double Cluster is circumpolar, so it’s above the horizon every night of the year at any hour of the night. If you are farther south (but still in the Northern Hemisphere), try looking for the Double Cluster on any clear autumn or winter night.

But remember, the Double Cluster is harder to see when it’s close to the horizon. If you can’t spot it between Cassiopeia and Perseus, wait until later at night. Or look later in the year, when it’s higher in the sky.

For general reference, the Double Cluster is high in the sky when the Big Dipper is low, and vice versa. Because the Big Dipper is lowest in the northern sky on late autumn and early winter evenings, the Double Cluster is highest in the northern sky at these times. As a matter of fact, the Double Cluster is pretty much always visible in the evening except in late spring and summer.

The Double Cluster in Perseus is visible to the unaided eye

The Double Cluster rates among the most magnificent deep-sky objects not to be included in the famous Messier catalog. Of course, Charles Messier (1730-1817) was looking for deep-sky objects that could be mistaken for comets. Maybe he thought nobody would see this pair of glittery clusters as a comet in the sky.

Although considered a deep-sky jewel, the Double Cluster is visible to the unaided eye in a dark country sky.

If you zoom in on them with binoculars or a wide view telescope, you’ll see them as two glorious star clusters. Also they’re an easy target through a telescope and will wow your friends!

The position of h Persei is Right Ascension: 2h 19m; Declination: 57o 9′ north

The position of chi Persei is Right Ascension: 2h 22.4m; Declination: 57o 7′ north

The Double Cluster from our EarthSky Community

Two large star groups each with many bright blue stars in field of thousands of faint stars.
View at EarthSky Community Photos. | Jeremy Likness in Newport Oregon, captured this telescopic view of the Double Cluster in the constellation Perseus on November 24, 2023. Jeremy wrote: “The Double Cluster is the beautiful pair of NGC 869 (h Persei) and NGC 884 (chi Persei), containing over 300 blue-white supergiants and a scattering of red supergiants. The cluster is also blue-shifted as it inches its way 24 miles [39 km] closer to earth every second. It is visible to the unaided eye and lurks near the distinct ‘W’ of Cassiopeia.” Thank you, Jeremy!
Two large but loose groupings of many bright stars in dense starfield.
View at EarthSky Community Photos. | Mario Rana in Hampton, Virginia, captured this telescopic view of the Double Cluster in Perseus (NGC 869 and NGC 884) on September 18, 2023. Mario explained this could be his favorite deep-sky object. Thank you, Mario!

Bottom line: On any autumn or winter evening, scan between Cassiopeia and Perseus for the magnificent Double Cluster in Perseus. The stars in these two clusters are young, hot supergiant suns that are many thousands of times more luminous than our sun.

Posted 
October 4, 2024
 in 
Clusters Nebulae Galaxies

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