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Hubble got the lion’s share of the credit for this discovery, but Lowell Observatory astronomer Vesto Slipher, who noticed the same phenomenon but didn’t publish his data, also anticipated that result.

The most important thing you'll need to know where to look and have a good view of the horizon, according to Nick Moscowitz, an astronomer at Lowell Observatory in Flagstaff, Arizona.

"If Eris and Makemake hosted, or perhaps could still host warm, or even hot, geochemistry in their rocky cores, cryovolcanic processes could then deliver methane to the surfaces of these planets, perhaps in geologically recent times," said Dr. Will Grundy, an astronomer at Lowell Observatory, one of Glein's co-authors and lead author of a companion paper.

The authors came to their conclusion after first comparing images of the ice giant to measurements of its brightness, which were recorded by the Lowell Observatory in Arizona from 1950 -- 2016 at blue and green wavelengths.

"It's amazing to see this object so well preserved that its shape directly reveals these details of its assembly from a set of building blocks all very similar to one another," said Lowell Observatory's Dr. Will Grundy, co-investigator of the New Horizons mission.