when galaxies collide: hubble telescope catches sights of stars being born

Xinhai

PureInsight | July 22, 2002

After more than three years of inactivity, the Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) recently returned to normal activity. In early June this year, NASA released some very exciting images. One of them shows a titanic collision involving four galaxies in a tangled galactic system called IRAS 19297-0406. This collision of galaxies is creating a torrent of new stars, and the dust generated by the new stars glows fiercely in infrared light.

These infrared galaxy systems, called ultra-luminous infrared galaxies (ULIRG), are a class of galaxies with strange shapes and are characterized by their infrared radiation that is at least 100 times more powerful than their cousins in our Milky Way. Astronomers believe that the strong infrared emission is a consequence of the intense activity of stellar formation triggered by the collision of galaxies. The dust around the new stars absorbs their radiation and reemits the energy in the form of intense infrared light.

IRAS 19297-0406 is producing about 200 new sun-like stars every year — about 100 times more stars than our Milky Way creates. The galaxies in collision are so close to each other that eventually they will form one massive galaxy.

Astronomers believed ULIRGs only contained one pair of galaxies in the very beginning. However, the images from the Hubble telescope show the astonishing complexity in the galaxy structure. Astronomer Kirk Borne of the Goddard Space Flight Center of NASA, together with his coworkers, believed that the strange shape of ULIRGs was the result of the collisions of multiple galaxies. Images generated by complicated computer simulation of the multi-galaxy collisions were similar to those images taken by the Hubble telescope. Apparently some of them were involved in collisions that led to the fiery fusion of three, four or even five galaxies.

Using the Hubble to conduct a three-year survey of 123 ULIRGs within 3 billion light-years of Earth, Borne found that 30% of them showed strong visual evidence of multiple mergers.

"We are seeing the final stage of the hierarchical evolution of the universe, where small fragments coalesce to build ever bigger objects," says Borne. "We see matter ripped out of galaxies in the form of long tails of stars, and matter contracting in the form of multiple nuclei crowded together. In some we see a 'nest' of galaxies where they all coalesce."

These results offer a snapshot of what conditions were like in the early universe, when galaxy collisions were commonplace. In particular, recent observations of space reveal tremendous changes, and discoveries of the emergence of new stars are numerous, which indicates that the universe is undergoing a renewal process. The ancient Chinese believed that heaven and the human world are actually a unified entity and these observations may imply that our universe is returning to an early stage. During the course of Falun Dafa spreading around the world, heaven, earth and human society are changing accordingly.

References:

1. http://oposite.stsci.edu/pubinfo/pr/1999/45/

2. http://oposite.stsci.edu/pubinfo/PR/2002/13/pr-photos.html