1. Star behind Uranus’s rings
Eclipse
Transit
Occultation

2. Stellar Occultation Observation by Airborne Platform

3. SOFIA’s predecessor, the Kuiper Airborne Observatory (KAO)

4. Star behind Uranus and rings
The rings of Uranus – discovered via occultation observations by the KAO.
Star behind Uranus and rings
Data record shows ‘dropouts’ in brightness of the star as it was occulted by each ring.

5. An atmosphere
gives an object a “soft edge”
observable
via occultation.

6. Image of
<= Pluto
merged with image of background star.

7. 2015 occultation light curve

8. 2011 Pluto
occultation
light curve
observed by
SOFIA.
*** SEEMS TO SHOW LESS ATMOSPHERE THAN IN 2015.

9. Large regions of Pluto are craterless, with folded mountain belts at their edges …
signs of tectonic activity! Internal activity could be what sustains Pluto’s atmosphere.

10. ■ Figure Because Neptune’s equator is inclined almost 29° in its orbit, it experiences seasons. Because of the planet’s orbital period, each season lasts about 40 years. Since Voyager 2 visited in 1989, spring has come to the southern hemisphere, and the weather has clearly changed, which is surprising because sunlight on Neptune is 900 times dimmer than on Earth.
Figure 24-13a p550

11. ■ Figure Nereid has a large, elliptical orbit around Neptune, but Triton follows a small, circular, retrograde orbit. At a distance of 30 AU from Earth, Triton is never seen farther than 16 arc seconds from the center of Neptune.
Figure p551

12. Voyage 2 images of Triton showing signs of geologic activity.
Black smoke plumes
from cyro-volcanoes
Voyage 2 images of Triton showing
signs of geologic
activity.
■ Figure (a) Triton’s south pole (bottom) had been in sunlight for 30 years when Voyager 2 flew past in The frozen nitrogen in the polar cap appears to be vaporizing, perhaps to refreeze in the darkness at the planet’s north pole. The dark smudges are produced when liquid nitrogen in the crust vaporizes and drives nitrogen geysers. (b) Roughly round basins on Triton may be old impact basins flooded repeatedly by liquids from the interior. Notice the small number of craters on Triton, a clue that it is a partially active world.
Smooth surfaces
covered by flows
of water “lava”.

13. Triton
shadow path
5 Oct 2017