IC 4996 is thought to form a double cluster with the P Cygni Cluster, which has the bright star 34 Cygni at its eastern edge.
The cluster takes its name from its brightest star, P Cygni, which is an alternative moniker for 34 Cygni.
P Cygni and its associated clusters are approximately 7,500 light-years away.
NGC 6819 Open cluster 7.3 5' NGC 6888 Bright nebula 8.8 18' x 8' O[summation] 401 Double star 7.3, 10.6 13.0" Fairy Ring Asterism -- 22' IC 4996 Open cluster 7.3 5' [beta]422 Aa Double star 9.7, 10.8 4.2" P Cygni Cluster Open cluster -- 5' P Cygni Variable star 4.8 var.
A Milky Way star called P Cygni
, which brightened and shed a tenth of a solar mass in 1600, may have undergone even fiercer outbursts over the past few thousand years, Smith and others note.
At first glance, P Cygni in the heart of the Northern Cross might look like a run-of-the-mill variable star.
Astronomers suspect that P Cygni ejected gaseous shells during its recent eruptions.
MOMI's images clearly show P Cygni's two previously known expanding shells of circumstellar gas - a bright inner one about 20 arcseconds in diameter and a fainter, outer shell approximately 1.5 arcminutes wide.
In analyzing recent and historical observations of a star called P Cygni, however, scientists have found that this Milky Way resident has increased steadily in brightness over the past 300 years -- indicating it has aged significantly in the twinkling of an astronomical eye.
That celestial object, a blue supergiant called P Cygni, lies some 6,000 light-years from Earth in the constellation Cygnus (the Swan) and is about 30 times as massives as the sun.
P Cygni has been visible to the naked eye ever since Dutch cartographer Willem Janszoon Blaeu first spotted it on Aug.
Start from Gamma ([Gamma]) Cygni in the center of the Northern Cross, move 2.5 [degrees] south-southwest along the neck of Cygnus to 34 or P Cygni
, then another 1.3 [degrees] on to 29 Cygni.