jun 272013

June 27, 2013

The Grasshopper, a pair of interacting galaxies in Lynx

UGC 4881, Arp 55

Image Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

The Grasshopper (designated UGC 4881 or Arp 55) is a bright pair of interacting galaxies, located about 527 million light-years away from Earth in the northern constellation of Lynx. The galaxies are speeding away from us at some 11,782 kilometers per second.

The colliding galaxies are thought to be halfway through a merger: the cores of the parent galaxies are still clearly separated, but their disks are overlapping. The Grasshopper has a bright curly tail containing a remarkable number of star clusters, and a vigorous burst of star formation may have just started.

A Type II or Ib/c supernova called SN 1999gw was discovered in The Grasshopper on December 16, 1999. This discovery was obtained by an infrared monitoring campaign, aimed at detecting obscured supernovae. Finding SN 1999gw in the infrared indicates that optical surveys probably miss a significant fraction of supernovae, especially in obscured systems such as starburst galaxies.

A supernova is a phenomenon in which a star explodes in the final phase of its life. There are two types: Type I and Type II. The Type I does not show hydrogen in the spectra. The Type I category is sub-divided into Type Ia, Type Ib and Type Ic supernovae. Among these, Type Ia are explosions of white dwarf stars. Types Ib and Ic supernovae are caused by the core collapse of massive stars (initially more than 8 times the mass of the Sun) and are usually referred to as stripped core-collapse supernovae. The other group, Type II, are also explosions of massive stars, but they do show hydrogen in their spectra.

This image was taken on December 4, 2001 with the Wide Field Channel of the Advanced Camera for Surveys on the Hubble Space Telescope, using two different color filters.

Share this post