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To celebrate the 21st anniversary of the Hubble Space Telescope’s deployment into space, astronomers at the Space Telescope Science Institute in Baltimore, Md., pointed Hubble’s eye at an especially photogenic pair of interacting galaxies called Arp 273. Image: NASA/ESA/Hubble Heritage Team (STScI/AURA)

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The Hubble Space Telescope

In celebration of the anniversary of the Hubble Space Telescope’s 1990 deployment into space, astronomers at the Space Telescope Science Institute in Baltimore, Md., pointed Hubble’s eye to an especially photogenic group of interacting galaxies called Arp 273. The larger of the spiral galaxies, known as UGC 1810, has a disk that is tidally distorted into a rose-like shape by the gravitational tidal pull of the companion galaxy below it, known as UGC 1813. A swath of blue jewels across the top is the combined light from clusters of intensely bright and hot young blue stars. These massive stars glow fiercely in ultraviolet light. The smaller, nearly edge-on companion shows distinct signs of intense star formation at its nucleus, perhaps triggered by the encounter with the companion galaxy. A series of uncommon spiral patterns in the large galaxy is a tell-tale sign of interaction. The large, outer arm appears partially as a ring, a feature seen when interacting galaxies actually pass through one another.

Arp 273 lies in the constellation Andromeda and is roughly 300 million light-years away from Earth. The tenuous tidal bridge of material between the two galaxies are separated by tens of thousands of light-years.