We all know that the Moon (with some help from the Sun) causes the tides on the Earth, but most people probably don’t realize that the Moon also becomes distorted by its gravitational interaction with the Earth. NASA scientists have been studying the distortion using NASA’s Lunar Reconnaissance Orbiter and Gravity Recovery and Interior Laboratory missions. The tidal effect on the Earth is most evident in the ocean tides, because water is easy to move around, but the effect on the Moon, which is mostly solid except for its small core, is to distort it into a slight egg shape. The force of the Earth’s gravitational tugging is sufficient to produce a bulge of about 20 inches on the surface of the Moon. The position of that bulge changes with time so that the Moon appears to wobble in the sky. Earth likewise appears to move around in the sky from the Moon’s point of view.
NASA’s Spitzer Space Telescope has captured several photos of the Serpens Cloud Core, where moderate-mass stars like our Sun are being born, and compiled them into the beautiful image above. The image is a combination of infrared light, which can penetrate through dust, and visible light, which is blocked by dust. The dark region to the left of the bright core is a region of dust so dense that not even infrared light could get through.