Polar Ice

These pictures show the distribution of surface ice at the Moon’s south pole (left) and north pole (right) as detected by thes Moon Mineralogy Mapper instrument. The blue areas are the icy regions plotted over images of the lunar surface with the gray scale corresponding to surface temperature (darker representing colder areas and lighter shades indicating warmer zones). As expected, the ice is concentrated at the darkest and coldest locations, the shadows of craters. This data is the first direct, definitive evidence of water ice on the Moon’s surface.

Image Credits: NASA

Lopsided M96

A galactic maelstromThis is Messier 96, a spiral galaxy a bit more than 35 million light-years away in the constellation of Leo (The Lion). It is roughly the same mass and size as the Milky Way, but unlike our more or less symmetrical galaxy, M96 is lopsided. Its dust and gas are unevenly spread throughout its weak spiral arms, and its core is not exactly at the apparent galactic center. Its arms are also asymmetrical, perhaps because of the gravitational pull of other galaxies within the same group as Messier 96.

Image Credit: ESA / NASA

The Evolving Universe

Astronomers have assembled one of the most comprehensive portraits yet of the universe’s evolutionary history. It’s based on a broad spectrum of observations by the Hubble Space Telescope and other space and ground-based telescopes. In particular, Hubble’s ultraviolet vision has been used to track the birth of stars over the last 11 billion years, going all the way back to the cosmos’ busiest star-forming period about 3 billion years after the big bang. This composite image encompasses a sea of around 15,000 galaxies widely distributed in time and space. About 12,000 of them are undergoing star formation. This mosaic is 14 times the area of the Hubble Ultra Violet Ultra Deep Field released in 2014. Right click on the image to embiggen it.

Image Credits: NASA / ESA / P. Oesch (University of Geneva) / M. Montes (University of New South Wales)

You Can’t See This From Here

Crescent SaturnThis is a view of Saturn partially lit in crescent phase, a view that can only be seen when the object is between the observer and the Sun. From the Earth, we can only see Mercury and Venus in varying crescent phases and Mars and the other outer planets fully lit. Because the Moon can be either between the Earth and the Sun or farther away, we see it go through all the phases from New to Full to New again.

This picture of Saturn was made by the Cassini spacecraft.

Image Credit: NASA

Translucent Rings

Saturn’s rings are mostly water ice in chunks that range in size from smaller than a grain of sand to mountains. The ring system extends 282,000 km from the planet, but it’s only about 10 m thick in most places. Looking from some angles, it’s possible to see through the rings—as in this that looks from south to north. The Cassini spacecraft took the images stitched together in this natural-color mosaic in April, 2007, when it was about 725,000 kim from Saturn.

Image Credit: NASA

The Backward Galaxy

backward galaxyThe Backward Galaxy (aka NGC4622) lies 111 million light years away in the constellation Centaurus. NGC 4622 is an example of a galaxy with leading spiral arms. In most spiral galaxies, the spiral arms trail; that is, the tips of the spiral arms are winding away from the center of the galaxy in the direction of the disk’s orbital rotation. In NGC4622, however, the outer arms are leading spiral arms; the tips of the spiral arms point towards the direction of disk rotation. This may be the result of a gravitational interaction between NGC 4622 and another galaxy or the result of a merger between NGC 4622 and a smaller object.

Image Credit: NASA