N90.Name

A volcano onKrakatoais still erupting.Perhaps most famous for the powerfully explosiveeruption in 1883 that killed tens of thousands of people, ash from aviolent eruption might also have temporarily altered Earth’s climate as long as 1500 years ago.In 1927, eruptions caused smallerAnak Krakatau to rise from the sea, and theemerging volcanic island continues to grow at an average rate of 2 cm per day. The latesteruption of Anak Krakatau started in 2008 April and continues today. In this picture,Anak Krakatau is seen erupting fromRakata, the main island of the Krakatoai group. High above, stars including the Big Dipper are clearly apparent.

Beautiful island universeM94 liesa mere 15 million light-yearsdistant in the northern constellation of the hunting dogs,Canes Venatici.A popular target forearth-based astronomers,the face-onspiralgalaxy is about 30,000 light-years across.Its remarkable features include prominent dust lanes,a bright, point-like nucleus, and a bright,bluish ring dominated by the light of young, massive stars.The massive stars in the ring are all likely less than 10 million years old, indicating the galaxy experienced a well-definedera of rapid star formation.As a result, while the small, bright nucleus is typical ofthe Seyfert class of active galaxies,M94 is also known as astarburst galaxy.Because M94 is relatively nearby, astronomers can explorein detailreasons for the galaxy’s burst of star formation.

These are galaxies of theHerculesCluster, an archipelago ofisland universes a mere500 million light-years away.Also known asAbell 2151,this cluster is loaded with gas and dust rich,star-forming spiral galaxiesbut has relatively few elliptical galaxies,which lack gas and dust and the associated newborn stars.The colors inthis remarkablydeep composite imageclearly show the star forming galaxies with a blue tint andgalaxies with older stellar populations with a yellowish cast.The sharp picture spans about 3/4 degree across thecluster center, corresponding to over 6 million light-years at thecluster’s estimated distance.In the cosmic vista many galaxies seem to becolliding ormergingwhile others seemdistorted – clear evidence thatcluster galaxiescommonly interact.In fact, the Hercules Cluster itself may be seen as the result ofongoing mergers of smaller galaxy clusters and is thought to besimilar to young galaxy clusters inthe much more distant,early Universe