by Ann » Sun Feb 16, 2020 7:22 am
Ah, NGC 2392, I thought when I saw the NGC designation of today's 24 hours' of APOD fame, that is one of my absolutely favorite clusters...yes?
No!
The cluster I was thinking of is NGC 23
62, a magnificent cluster in Canis Major with a fantastic central star, Tau Canis Majoris!
Jim Kaler wrote about Tau Canis Majoris (Tau CMa):
Almost fifth magnitude (4.40), and needing reasonably dark conditions to see, it is one of the sky's rare very hot and blue class O (O9) supergiants, its modest apparent brightness the result of its huge distance of 4800 light years, the light you see having left the star around 2800 BC!
It is so far away that we would not have a good handle on its distance at all except for the fact that Tau is the premier member (or so most believe) of a star cluster called NGC (for New General Catalogue) 2362. Since we can easily compare the brightnesses of stars within such a cluster with those of clusters whose distances we do know, we can find NGC 2362's distance quite accurately.
More important, Tau CMa is a massive multiple star, having at least five components...
The brilliance of these stars reveals their huge masses, the inner four together shining with the light of half a million Suns, which suggests average masses around 20 times solar...
We speculate that the stars were not born in this configuration, but that the bright quartet was formed when two doubles within the cluster passed too close together and merged to create this remarkable system.
Such a complex high-mass multiple star reminds me of the Trapezium Cluster in the Orion Nebula and also the star Iota Orionis:
- Trapezium Cluster in M42. Image: NASA; K.L. Luhman (Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.); and G. Schneider, E. Young, G. Rieke, A. Cotera, H. Chen, M. Rieke, R. Thompson (Steward Observatory, University of Arizona, Tucson, Ariz.)
Jim Kaler wrote about Iota Orionis (Na'ir al Saif) and the Trapzieum cluster:
Na'ir al Saif and its close companion help reveal the power of gravity and stellar dynamics. Twenty-six degrees to the south lies fourth magnitude Mu Columbae (in Columba, the Dove); 40 degrees to the north in Auriga lies the variable star AE Aurigae. The two, with spectral classes nearly identical to that of Na'ir al Saif, are hurtling away from each other in opposite directions at 200 kilometers per second. Called "runaway stars," they appear to have been shot out of Orion. Na'ir al Saif still lingers near the Orion Nebula, marking the place of the violent event.
Recent calculations of the movements of the stars explain the two runaways and Na'ir al Saif as well, showing that they were all kicked out of the Trapezium Cluster. Some 2.5 million years ago, the Trapezium region held a pair of tightly-knit double stars. In a very close encounter between the two binaries, two of the four stars were ejected, while the remaining two, instead of being evicted, stayed more or less behind in highly eccentric embrace.
[float=right][img3="NGC 2362. Placid for now. Photo: Sergio Eguivar."]https://lh3.googleusercontent.com/proxy/YXnkyRiOfRaJEubxbTWKeSDKn45JWUeiw9oKqvE41PkcYbI4P6tx47jJWQLdetqxl_c7DvmCka7PrOpYYJYNfp99XEvgxIYlq-g5VRiR4ZS1hbrvNid8Yxglfmmy1Vro4qw[/img3][/float]Ah, NGC 2392, I thought when I saw the NGC designation of today's 24 hours' of APOD fame, that is one of my absolutely favorite clusters...yes?
No! :( The cluster I was thinking of is NGC 23[b][size=110]6[/size][/b]2, a magnificent cluster in Canis Major with a fantastic central star, Tau Canis Majoris!
[quote][url=http://stars.astro.illinois.edu/sow/taucma.html]Jim Kaler[/url] wrote about Tau Canis Majoris (Tau CMa):
Almost fifth magnitude (4.40), and needing reasonably dark conditions to see, it is one of the sky's rare very hot and blue class O (O9) supergiants, its modest apparent brightness the result of its huge distance of 4800 light years, the light you see having left the star around 2800 BC!
It is so far away that we would not have a good handle on its distance at all except for the fact that Tau is the premier member (or so most believe) of a star cluster called NGC (for New General Catalogue) 2362. Since we can easily compare the brightnesses of stars within such a cluster with those of clusters whose distances we do know, we can find NGC 2362's distance quite accurately.
More important, Tau CMa is a massive multiple star, having at least five components...
The brilliance of these stars reveals their huge masses, the inner four together shining with the light of half a million Suns, which suggests average masses around 20 times solar...
We speculate that the stars were not born in this configuration, but that the bright quartet was formed when two doubles within the cluster passed too close together and merged to create this remarkable system.[/quote]
Such a complex high-mass multiple star reminds me of the Trapezium Cluster in the Orion Nebula and also the star Iota Orionis:
[float=left][img3="Trapezium Cluster in M42. Image: NASA; K.L. Luhman (Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.); and G. Schneider, E. Young, G. Rieke, A. Cotera, H. Chen, M. Rieke, R. Thompson (Steward Observatory, University of Arizona, Tucson, Ariz.)"]https://www.messier-objects.com/wp-content/uploads/2015/05/Trapezium-Cluster.jpg[/img3][/float] [float=right][img3="Deept-sky objects in Orion, including the Orion Nebula with the Trapezium cluster (overexposed here) and the star Iota Orionis. Photo: Bob King."]https://s22380.pcdn.co/wp-content/uploads/Neglected-Orion-Belt-and-Nebula-M42-ANNO-SouthUp_S.jpg[/img3][/float]
[float=left][quote]Jim Kaler wrote about Iota Orionis (Na'ir al Saif) and the Trapzieum cluster:
Na'ir al Saif and its close companion help reveal the power of gravity and stellar dynamics. Twenty-six degrees to the south lies fourth magnitude Mu Columbae (in Columba, the Dove); 40 degrees to the north in Auriga lies the variable star AE Aurigae. The two, with spectral classes nearly identical to that of Na'ir al Saif, are hurtling away from each other in opposite directions at 200 kilometers per second. Called "runaway stars," they appear to have been shot out of Orion. Na'ir al Saif still lingers near the Orion Nebula, marking the place of the violent event.
Recent calculations of the movements of the stars explain the two runaways and Na'ir al Saif as well, showing that they were all kicked out of the Trapezium Cluster. Some 2.5 million years ago, the Trapezium region held a pair of tightly-knit double stars. In a very close encounter between the two binaries, two of the four stars were ejected, while the remaining two, instead of being evicted, stayed more or less behind in highly eccentric embrace.[/quote][/float]
[float=right][img3="AE Aurigae, plowing through and ionizing the Flaming Star Nebula after having been kicked out of the Trapezium region. Image Credit & Copyright: Martin Pugh."]https://science.nasa.gov/files/science-pink/s3fs-public/styles/image_gallery_scale_960w/public/atoms/flamingstar_pugh_960.jpg?itok=o3GikXLL[/img3][/float]