Top Space Pictures of the Week, From a Hubble Icon to Hungry Black Holes

The Hubble Space Telescope got off to a rocky start when it launched in 1990—a flaw in its main mirror was causing the telescope to send back frustratingly blurry images. But with some corrective surgery thanks to an astronaut-helmed servicing mission, the observatory soon awed the world with stunning images of star clusters, galaxies, nebulas and other colorful objects across the cosmos. No image is perhaps more iconic than Hubble's 1995 shot of a star-forming region in the Eagle Nebula that was given the grandiose nickname the "Pillars of Creation".

Now, for the 25th anniversary of Hubble's launch, the team has released an even sharper image of the pillars (left), taken with an updated camera that was installed in 2009. The telescope team also unveiled a ghostly infrared image of the famous structures (right) that allows astronomers to peer though the thick dust of the nebula and see the newborn stars inside.

Space is big, so why not travel across the cosmos with friends? This image from the Gemini observatory in Hawaii shows a galactic herd called VV 166, which lies about 300 million light-years away. Similar galaxy groups exist across the universe—our own Milky Way is part of a "local group" that includes the Andromeda galaxy, the Triangulum galaxy and the Magellanic Clouds, among others.

This image of VV 166 clearly shows the diverse types of galaxies that can coexist in such groups. The prominent spiral galaxy NGC 70, near the top of the image, glows blue with new star formation in its shapely arms. By contrast, the two small galaxies below the spiral look wan and pale, showing signs that they are no longer giving birth to many new stars. The one to the left, NGC 71, is actually a strange beast called a lenticular galaxy, a lens-shaped object that looks like a spiral galaxy that is missing the telltale arms. The one to the right is a much older elliptical galaxy called NGC 68, a proper blob of old stars. Such detailed portraits of galactic groups can help astronomers figure out how galaxies get their different shapes, and whether galaxies form together in groups or if they pick up new companions as they move through the universe. 

In an act of cosmic voyeurism, the Hubble Space Telescope captured this detailed close-up of our biggest neighbor, the Andromeda galaxy. The enormous image spans just part of Andromeda's disk, but it shows more than 100 million stars across 40,000 light-years of space. The view is actually a mosaic of more than 400 Hubble pictures, stitched together to create an unprecedented panoramic.

Like the Milky Way, Andromeda is a spiral galaxy, with sweeping arms of stars that form a disk around a bright central bulge. The galaxy is the closest big spiral to our home turf, sitting a mere 2.5 million light-years away. Astronomers predict that the Milky Way and Andromeda are on a collision course and will merge in about 4 billion years.

When telescopes stare at a patch of the night sky, they usually see that space is full of stars and colorful clouds of gas. But sometimes, a strange blob interrupts the glittering backdrop, as if someone has poured ink on the sky. Perhaps surprisingly, such "dark nebulae" are where stars are born.

This image, from a European Southern Observatory telescope in Chile, shows the dark nebula LDN 483, a cloud of interstellar gas and dust that is so dense it obscures visible light. Inside, cool balls of gas are collapsing under their own gravity to form protostars, fledgling stars that shine in wavelengths we can't see without optical aids. As the temperature and pressure increase in the stellar cores, the stars will get brighter, eventually becoming visible to human eyes. In enough time, the entire dark nebula will give way to a group of brilliant newborn stars.

Black holes are, by definition, difficult to see. The best visual clues we have to their existence are when the massive objects feast on surrounding debris. Then the disks of hot matter falling into their maws release a bright glow of high-energy radiation that gives away the black hole's position. That's why astronomers turned to the Nuclear Spectroscopic Telescope Array (NuSTAR) to solve a black hole puzzle.

Based on visible-light images, astronomers knew that the object called Arp 299 is actually a pair of galaxies in the process of colliding. Each galaxy harbors a supermassive black hole at its center, but the scientists couldn't be sure whether one or both was actively feeding. Combining a Hubble Space Telescope image with high-energy x-ray data from NuSTAR, a NASA team was able to pinpoint the hungriest monster—only the black hole in the galaxy on the right glows brightly as it feeds. The data should help astronomers better understand how galaxy collisions can trigger black holes to start eating with gusto.

Compared with other big galaxies, our Milky Way is a quiet place. The supermassive black hole that sits at the galactic center is not very active, munching lightly on the occasional star or gas cloud and putting out a relatively gentle x-ray glow. But every now and then, our black hole fires off a huge burp of radiation. In September 2013, astronomers using NASA's Chandra X-ray Observatory saw the biggest belch yet—a huge x-ray flare that was 400 times brighter than usual.

The team thinks the flare may have been triggered when an asteroid got too close to the black hole and was ripped apart and devoured. The debris would have been intensely heated as it fell into the black hole, creating the x-ray burst. But it's also possible that the outburst happened when tangled magnetic field lines around the black hole snapped into a new configuration and released energy. Keeping track of future flares could help astronomers figure out what causes them, refining our picture of the ways physics work around these extreme objects.

Thanks to countless beauty shots from NASA's Cassini mission, the ringed planet Saturn is a solar system icon. But even with oodles of pictures, astronomers didn't have the best maps for figuring out where Saturn and its moons truly are at any given time. Now a team of scientists has created the most precise map of the Saturn system yet, using data from the National Science Foundation's Very Long Baseline Array.

The VLBA is a network of 10 radio telescopes that spans from Hawaii, across North America and into the Virgin Islands. The array effectively acts like a telescope as wide as Earth's diameter. Using this powerful eye, the astronomers tracked the radio signals from Cassini as it toured the Saturn system for the past decade. That data helped them pinpoint the positions of the planet and its moons to within about a mile—measurements that are 50 to 100 times more precise than previously available. The new and improved road map should help astronomers with a variety of tasks, from navigating spacecraft to weighing other objects in the solar system.