This is another great astroimage by Rogelio Bernal Andreo.
The picture is a great portrait of a relatively massive galaxy cluster. Typically, the great majority of the galaxies are ellipticals. Rogelio Bernal Andreo has put M87 in the center of his image, which is fitting, since this supermassive elliptical galaxy with its relativistic jet is the dominant member of the entire Virgo Cluster.
Note how the biggest elliptical galaxies, M87, M86, M84 and M89 are surrounded by huge diffuse haloes. This is in sharp contrast to the few spiral galaxies here.
You can easily find the spiral galaxies by looking out for their blue disks. In reality, though, the spiral galaxies in this image are not so blue. Or rather, the spiral galaxies here are certainly blue compared with the elliptical galaxies in the cluster, so Rogelio's image does the color difference between the ellipticals and the spirals full justice.
But the spirals here are not so blue compared with typical spirals that are not located in big galaxy clusters. That's because the large galaxy cluster environment clearly impairs star formation. M90, for example, the bluest-looking of the galaxies in today's APOD, is an "anemic" galaxy with a large population of A-type stars, but very few B- or O-type stars. This image by Adam Block shows the true nature of M90:
The galaxy has a large yellow bulge, surrounded by a dusty ring with some, but not a lot of, star formation. Outside this ring there are smooth rather neutral-colored mostly dust-free broad arms whose light comes mainly from A-, F- and G-type stars. The presence of a large population of A-type stars does give this part of the galaxy a bluish tinge.
Interestingly, the Hubble Telescope recently took an image of a galaxy that resembles M90 in that it is situated in a large galaxy cluster, has broad smooth arms and has mostly shut down its star formation. The galaxy in question is NGC 4921 in the Coma Cluster:
The filters used by Hubble to produce the image don't bring out the color difference between the yellow bulge of NGC 4921 and its slightly bluish but fairly neutral-colored arms. But here is another image that does just that:
This former APOD does show you the slightly enhanced color difference between the arms and the bulge of NGC 4921. The galaxy is on the far left in this image.
Ann
This is another great astroimage by Rogelio Bernal Andreo.
The picture is a great portrait of a relatively massive galaxy cluster. Typically, the great majority of the galaxies are ellipticals. Rogelio Bernal Andreo has put M87 in the center of his image, which is fitting, since this supermassive elliptical galaxy with its relativistic jet is the dominant member of the entire Virgo Cluster.
Note how the biggest elliptical galaxies, M87, M86, M84 and M89 are surrounded by huge diffuse haloes. This is in sharp contrast to the few spiral galaxies here.
You can easily find the spiral galaxies by looking out for their blue disks. In reality, though, the spiral galaxies in this image are not so blue. Or rather, the spiral galaxies here are certainly blue compared with the elliptical galaxies in the cluster, so Rogelio's image does the color difference between the ellipticals and the spirals full justice.
But the spirals here are not so blue compared with typical spirals that are not located in big galaxy clusters. That's because the large galaxy cluster environment clearly impairs star formation. M90, for example, the bluest-looking of the galaxies in today's APOD, is an "anemic" galaxy with a large population of A-type stars, but very few B- or O-type stars. This image by Adam Block shows the true nature of M90:
[img2]http://farm3.static.flickr.com/2051/1655069817_e932feedc4.jpg[/img2]
The galaxy has a large yellow bulge, surrounded by a dusty ring with some, but not a lot of, star formation. Outside this ring there are smooth rather neutral-colored mostly dust-free broad arms whose light comes mainly from A-, F- and G-type stars. The presence of a large population of A-type stars does give this part of the galaxy a bluish tinge.
Interestingly, the Hubble Telescope recently took an image of a galaxy that resembles M90 in that it is situated in a large galaxy cluster, has broad smooth arms and has mostly shut down its star formation. The galaxy in question is NGC 4921 in the Coma Cluster:
[img2]http://newswatch.nationalgeographic.com/files/2009/02/hubble-anemic.jpg[/img2]
The filters used by Hubble to produce the image don't bring out the color difference between the yellow bulge of NGC 4921 and its slightly bluish but fairly neutral-colored arms. But here is another image that does just that:
[img2]http://apod.nasa.gov/apod/image/1005/comacluster_rowe.jpg[/img2]
This former APOD does show you the slightly enhanced color difference between the arms and the bulge of NGC 4921. The galaxy is on the far left in this image.
Ann