Osiris became the first discovered exoplanet with an atmosphere.
It was found to have a hydrogen-rich atmosphere.
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A conjunction of Sun, Mercury, Venus, Mars, Jupiter, Saturn, and the Moon occurred.
NASA's New Horizons space probe completed the first flyby of Pluto in the history of human spaceflight.
The Soviet Union's Vega 1 Space Probe began sending back images of Halley's Comet.
The New York Times published Edwin Hubble's discovery that the Andromeda 'nebula' is actually a galaxy.
Gliese 229B became the first brown dwarf to be seen and identified by astronomers.
