AstronomyPicture of the Day—20181221

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2018December 21

ARainbow Geminid Meteor

ImageCredit & Copyright: Dean Rowe

Explanation:Meteors can be colorful. While the human eye usually cannot discern manycolors, cameras often can. Pictured is a Geminid captured by camera during lastweek's meteor shower that was not only impressively bright, but colorful. Theradiant grit cast off by asteroid 3200 Phaethon blazed a path across Earth's atmospherelonger than 60 times the angular diameter of the Moon. Colors in meteorsusually originate from ionized elements released as the meteor disintegrates,with blue-green typically originating from magnesium, calcium radiating violet,and nickel glowing green. Red, however, typically originates from energizednitrogen and oxygen in the Earth's atmosphere. This bright meteoric fireballwas gone in a flash -- less than a second -- but it left a wind-blownionization trail that remained visible for several minutes, the start of whichcan be seen here.