Hubble, Spitzer Space Telescope

Universe Lego Blocks Found

By Joshua S. Hill

Monday, September 10, 2007

The model most widely accepted for the evolution of our universe, and the galaxies that populate it, is that they formed from smaller galaxies which eventually coalesced, to form larger combined galaxies. We have seen recently reports of one galaxy eating another, and for a day or so we were led to believe that Earth was indeed from another galaxy all together.

This model has once again been confirmed, as nine galaxies -- termed as "Lego-like" -- have been found through a joint effort of the Hubble Telescope and its cousin observatory, NASA's Spitzer Space Telescope.

First identified by James Rhoads of Arizona State University, USA, and Chun Xu of the Shanghai Institute of Technical Physics in Shanghai, China, the nine galaxies are believed to be "…among the lowest mass galaxies ever directly observed in the early Universe," according to Nor Pirzkal of the European Space Agency/STScI.

Distanced so far away that we are observing them when they were only a billion years old, these galaxies contain sapphire blue stars within, and are only a few million years old. They are so young, that they are still in the process of turning elements from the formative years of the Big Bang in to heavier elements.

"While blue light seen by Hubble shows the presence of young stars, it is the absence of infrared light in the sensitive Spitzer images that was conclusive in showing that these are truly young galaxies without an earlier generation of stars," says Sangeeta Malhotra of Arizona State University in Tempe, USA, one of the investigators.

One of the indicators that has added substance to the coalescing theory of a galaxies evolution are the tadpole shape that three of the galaxies have formed. Rather than being rounded blobs as many galaxies are in their early years, these three have begun to stretch outwards. This, according to researchers, is a sign that they are interacting and merging with galaxies nearby, and may be in the process of forming larger more cohesive structures.

Observed originally in the Hubble Ultra Deep Field (HUDF) -- a Hubble Space Telescope composite image taken of a small region of space from amidst the Fornax constellation, between September 3, 2003 and January 16, 2004 -- the data surprised Pirzkal, who did not expect such low estimations for their masses.

The combination of Hubble's Advanced Camera for Surveys and the Near Infrared Camera and Multi-Object Spectrometer which took the initial images, was later back up by Spitzer's Infrared Array Camera and the European Southern Observatory's Infrared Spectrometer and Array Camera to produce the data in question.

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