Something doesn’t add up about the ages of “blue straggler” stars. And Hubble takes a picture of the star that revealed the true nature of the universe.

• NASA's Hubble Finds Rare Blue Straggler Stars in the Milky Way's Hub
• Hubble Views Star that Changed the Universe

Theophilus crater on the Moon, as seen by Apollo 16. Credit: NASA

The Earth-Moon system has been studied in great detail and for many years. It has been theorized that the presence of the Moon has had a stabilizing effect on the spin of the Earth. This also has stabilized the atmosphere of the Earth because the tilt of the Earth’s axis does not wobble much relative to the orbit of the Earth around the Sun. In contrast, the tilt of Mars has likely wobbled nearly sixty degrees, leaving that planet desert-like with a thin atmosphere.

• Science magazine on the need for a Moon.

The Andromeda Galaxy and its revelatory star.

In 1920, the nature of spiral nebulae, now known as spiral galaxies, was unknown. The scale and expansion of the universe were unknown as well. Astronomers debated whether the spiral objects they could see in the sky were within our galaxy or outside it. The astronomer Edwin Hubble devoted considerable time to observing stars in Andromeda, the largest known spiral nebula of the time. He found a variable star that demonstrated that Andromeda was far away — and thus a separate galaxy. The first variable that Hubble found, known simply as “V1,” has been observed with the Hubble Space Telescope almost 90 years after the first observations of the object.

• HubbleSite news release.

An artist's concept of the Mars Exploration Rover Credit: NASA/JPL

Though NASA’s Mars rover, Spirit, is now officially proclaimed dead, it won’t be soon forgotten. NASA announced in May that it was ceasing any further attempts to raise Spirit. The spacecraft hasn’t been heard from since March 2010. In its six-plus years operating on the Martian surface, Spirit and its twin rover, Opportunity, revolutionized our view of the Red Planet.

• Bad Astronomy reports on NASA's farewell to Spirit.
• The Mars Rovers website.

Abell 383

A giant cluster of elliptical galaxies, called Abell 383, contains a large amount of matter, including dark matter. It has formed what is called a gravitational lens. This lens distorts and magnifies light from the more distant objects behind it. This process helped astronomers observe a young galaxy that formed early in the universe. The characteristics of this new object help explain what happened at the very beginning of the universe, not very long after the Big Bang.

• HubbleSite news release.
• The Spitzer mission gives an annotated version of the image.

Apollo 12 Commander Charles Conrad Jr. examines the Surveyor III spacecraft.

Some Apollo Moon landing folklore appears to have bitten the dust. The Apollo 12 Moon landing mission brought back the camera from the Surveyor 3 spacecraft, which had landed on the Moon two and a half years earlier. NASA discovered Earthly microbes that had seemingly survived several years in the Moon’s harsh environment. But now, new research indicates otherwise.

• NASA on the original puzzle.

Arp 273

Interacting pairs and groups of galaxies seem to be common in the universe. For 21 years, the Hubble Space Telescope has been providing beautiful images of such encounters along with amazing images of all kinds of other objects. Hubble took an anniversary image of interacting galaxy Arp 273, showing the beautiful but disturbed spiral structure of the main galaxy. The star formation and distortion apparent is most likely due to interaction with at least one, and possibly two, smaller galaxies in the vicinity.

• HubbleSite news release on the image.

Planets and dwarf planets of our solar system.

Four planets line up in space in May’s predawn sky. Mercury, Venus, Mars and Jupiter all appear as the sky brightens before dawn. Southern hemisphere residents have the best view, but northerners will need to find a low, clear horizon to see them all.

• EarthSky on the planets' appearance.