AstronomyPicture of the Day—20190105

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.

2019 January 5

Ultimaand Thule

ImageCredit: NASA, Johns Hopkins University APL, Southwest Research Institute

Explanation:On January 1 New Horizons encountered the Kuiper Belt object nicknamed UltimaThule. Some 6.5 billion kilometers from the Sun, Ultima Thule is the mostdistant world ever explored by a spacecraft from Earth. This historic image,the highest resolution image released so far, was made at a range of about28,000 kilometers only 30 minutes before the New Horizons closest approach.Likely the result of a gentle collision shortly after the birth of the SolarSystem, Ultima Thule is revealed to be a contact binary, two connectedsphere-like shapes held in contact by mutual gravity. Dubbed separately by thescience team Ultima and Thule, the larger lobe Ultima is about 19 kilometers indiameter. Smaller Thule is 14 kilometers across.