The Hubble Ultra Deep Field (HUDF) peers deeper into the universe than any previous visible-light image. Multiple observations of the same small patch of sky were combined for an equivalent exposure time of more than 11 days. Revealed within the image are thousands of galaxies located many billions of light-years away. Many of these galaxies are too small and too faint to be otherwise seen. Most importantly, because the light from distant galaxies requires billions of years to cross the intervening space, astronomers get to see them as they were billions of years ago. Much of the history of galaxy development can be found within the HUDF image.

This scientific visualization flies through a 3D model of the HUDF galaxies. Each of the more than 5,000 galaxies in the model was cut out of the HUDF image and placed at its appropriate distance (as calculated from redshift measurements). The virtual camera flies through this long, thin galaxy dataset, showing how galaxy sizes, shapes, and colors change as one looks both out in space and back in time. Note that, in order to traverse the cosmos in a reasonable amount of time, the distance scale in the model was compressed by a factor of a few hundred.

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The dense star cluster called R136 is located within the Tarantula Nebula (also known as 30 Doradus), a giant star-forming region in a nearby dwarf galaxy. Astronomers suspect that the multiple clumps of stars within R136 are actually a pair of interacting star clusters. Supporting evidence for this idea comes from the large number of “runaway stars” — stars moving with unusually high velocity — that have been found within the nebula. A single, large star cluster would not produce as many runaway stars as two smaller interacting star clusters. In addition, some of these runaway stars are older than the estimated age of R136.

This computer simulation shows the gravitational interaction of two young star clusters. The 3.5 million years of the encounter have been compressed into just 27 seconds. The smaller star cluster approaches from the left, has its trajectory bent strongly as it swings by the larger cluster, and then returns for a second pass. The visualization then zooms in and dissolves to a Hubble Space Telescope image of star cluster R136. After a partial zoom out, the sequence continues forward in time to show the clusters merging into a single cluster.

At the start of the simulation, the smaller cluster is not gravitationally bound to the large cluster. After the first interaction, the pair of star clusters become gravitationally entwined and destined to merge together. A noticeable byproduct of the encounter is that interactions between stars efficiently eject massive stars from the smaller cluster. Some of these ejected stars would be considered runaways. Further, the stars in the smaller cluster are a million years older than those in the larger cluster, which would help explain the observed age discrepancies. Finally, note that while all the stars shown are initially hot and blue, some reach the end of their lives during the simulation and evolve into cooler red giant stars.

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