A Tour of NGC 5813 (07-06-2015)
Galaxy groups are families of galaxies that are bound together by gravity. They are very similar to their larger cousins, galaxy clusters.

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Light Beyond the Bulb: Over and Beyond the Rainbow (07-01-2015)
While scientists and philosophers have tried to figure out exactly what light is for millennia, it's only been in the past several hundred years or so that we've really started to figure it out.

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--  Light Beyond the Bulb

A Tour of Circinus X-1 (06-25-2015)
These rings are light echoes, similar to sound echoes that we may experience here on Earth.

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--  X-ray Echoes Pinpoint Location of Distant Flaring Neutron Star

Light Beyond the Bulb: Intro to Light (06-04-2015)
The year 2015 has been declared to be the International Year of Light and Light-based Technologies by the United Nations.

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--  Light Beyond the Bulb

A Tour of Space-time Foam (05-29-2015)
Since space-time foam, as it is called, is so tiny, scientists cannot observe it directly.

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--  NASA Telescopes Set Limits on Space-time Quantum Foam