NASA’s New Horizons spacecraft has beamed back new images of Ultima Thule, which show that the most distant world ever explored is much flatter than previously thought. The images of the KBO — officially named 2014 MU69 — were captured by the New Horizons as it raced away at over 50,000 kilometers per hour on January 1.
The images were taken nearly 10 minutes after New Horizons crossed its closest approach point.
 
What
  1. NASA's New Horizons mission sent home close-up images of Ultima Thule, a 20-mile-long space rock in the uncharted heart of the Kuiper Belt. Chris Dignam has more.
  2. The newly released images also contain important scientific information about the shape of Ultima Thule, which is turning out to be one of the major discoveries from the flyby.
  3. At left is a composite of two images taken by New Horizons’ high-resolution Long-Range Reconnaissance Imager (LORRI), which provides the best indication of Ultima Thule’s size and shape so far. 
  4. Preliminary measurements of this Kuiper Belt object suggest it is approximately 20 miles long by 10 miles wide (32 kilometers by 16 kilometers). 
  5. An artist’s impression at right illustrates one possible appearance of Ultima Thule, based on the actual image at left. The direction of Ultima’s spin axis is indicated by the arrows. (Image source: NASA/JHUAPL/SwRI; Sketch: James Tuttle Keane)
  6. The first close-up images of Ultima Thule — with its two distinct and, apparently, spherical segments — had observers calling it a “snowman.”
  7. However, more analysis of approach images and these new departure images have changed that view, in part by revealing an outline of the portion of the KBO that was not illuminated by the Sun, but could be “traced out” as it blocked the view to background stars.
  8. Stringing 14 of these images into a short departure movie, New Horizons scientists can confirm that the two sections (or “lobes”) of Ultima Thule are not spherical.
  9. The larger lobe, nicknamed “Ultima,” more closely resembles a giant pancake and the smaller lobe, nicknamed “Thule,” is shaped like a dented walnut.
Flashback
  1. Ultima Thule is a trans-Neptunian object located in the Kuiper belt. It is a contact binary 31 km (19 mi) long, composed of two joined bodies 19 km (12 mi) and 14 km (9 mi) across that are nicknamed "Ultima" and "Thule", respectively. 
  2. With an orbital period of 298 years and a low inclination and eccentricity, it is classified as a classical Kuiper belt object. 
  3. With the New Horizons space probe's flyby at 05:33 on 1 January 2019 (UTC time), 2014 MU69 became the farthest and most primitive object in the Solar System visited by a spacecraft, both bodies being planetesimal aggregates of much smaller building blocks.

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