Supernova on a bridge

A pair of interacting galaxies gives astronomers an environment to study supernovae.
By | Published: July 7, 2006
NGC 5917
NGC 5917 (top right) is pulling material away from MCG-01-39-003 (bottom right). Supernova 2005cf exploded in the vicinity of the bridging material, and the supernova’s progenitor star likely was born in one of the two galaxies.
July 7, 2006
Astronomers using the European Southern Observatory’s (ESO) Very Large Telescope (VLT) have imaged a pair of interacting galaxies 87 million light-years away. While the galaxies themselves make a beautiful sight, what astronomers are most interested in is what is happening within the bridge of matter connecting the two. A supernova — called SN 2005cf — exploded in the bridge’s vicinity in May 2005.

Spiral galaxy NGC 5917 appears to be pulling material away from the peculiar spiral galaxy MCG-01-39-003. “Curiously, the supernova appears to be outside of the tidal tail,” says Ferdinando Patat, a member of the ESO VLT team who made the observation. The supernova’s placement means it was “probably stripped out of one of the two galaxies and exploded far away from the place where it was born,” according to Patat.

After further analysis, astronomers determined the supernova is a type 1a — the type used to show that the universe’s expansion is accelerating. Scientists don’t understand the full workings of supernovae, but the more of these explosions the astronomers study, the better they will understand the mechanisms responsible.

Evidence suggests galaxy encounters may increase star formation. Where there are more young, massive stars, scientists expect an increase in the number of supernovae. Therefore, astronomers think interacting galaxies likely contain more supernovae than isolated galaxies.

Immediately after SN 2005cf was discovered, the European Supernova Collaboration (ESC) led by, Wolfgang Hillebrandt of the Max-Planck Institute in Garching, Germany, studied the supernova throughout almost its entire evolution. The astronomers used a number of telescopes around the world, from 10 days before the object reached its peak luminosity until more than a year after the explosion.

Near the end of the observations, in April and May 2006, when SN 2005cf was extremely faint, astronomers used the VLT. Scientists study a supernova’s late — and, therefore, faint — stages to observe the explosion’s innermost material.