Largest Spiral Galaxy

Astronomers have crowned the universe's largest known spiral galaxy, a spectacular behemoth five times bigger than our own Milky Way.

The title-holder is now NGC 6872, a barred spiral found 212 million light-years away in the southern constellation Pavo, researchers announced today (Jan. 10). The distance between NGC 6872's two huge spiral arms is 522,000 light-years, compared to about 100,000 light-years for the Milky Way.

[Full Story: Largest Spiral Galaxy in Universe Revealed]

T. Rex of the Seas

Newfound fossils of a giant dolphin-shaped reptilian predator are now shedding light on how the world recovered after the most devastating mass extinction in history, researchers say.

This prehistoric sea monster could provide information on how the planet might deal with the mass extinction humans are causing now, scientists added.

[Full Story: 'T. Rex' of the Seas Called First Top Killer ]

Life on Exoplanet Moons?

In the search for an Earth-like alien world, astronomers have had their eyes set on planets beyond our solar system, but some moons orbiting some of these exoplanets may be just as likely to support life, scientists say.

Astronomers have discovered more than 800 exoplanets, with many more candidate worlds awaiting confirmation by follow-up observations. Most of them, however, are gas giants, similar to Jupiter, and only a handful have a solid surface and orbit their host stars in the habitable zone, the range where liquid water, and perhaps life as we know it, can exist.

[Full Story: Alien Life May Exist on Exoplanet Moons ]

Eerie Nightglow

The moon and stars may hog all the glory, but they’re not the only light in the sky at night. The air itself glows from chemical reactions between oxygen and nitrogen and other molecules in the atmosphere.

The Suomi NPP satellite caught a massive thunderstorm making waves in the nightglow above Texas and Oklahoma on April 15, 2012. While nightglow is a well-known phenomenon, scientists were surprised at Suomi NPP's ability to detect it, according to NASA's Earth Observatory. During the satellite's check-out procedures, scientists thought this light source was a problem with the sensor until they realized that they were seeing the faintest light in the darkness of night, the Earth Observatory reported.

[Full Story: Amazing Image: Eerie Nightglow Over Texas ]

Elusive Giant Squid

The notoriously elusive giant squid has been filmed for possibly the first time in its natural habitat after a Moby Dick-style hunt for the deep-sea beast.

A Japanese-led team filmed the silvery cephalopod last year off the Ogasawara Islands, about 620 miles (1,000 kilometers) south of Tokyo, according to news reports. The footage is to be broadcast in the United States this month.

[Full Story: Mysterious Giant Squid Finally Caught on Film]

Milky Way on Diet?

The Milky Way galaxy, home of Earth's solar system, may actually be only half as massive as currently thought, scientists say.

Stars in the far outer reaches of the Milky Way, between 260,000 and 490,000 light-years from the galactic center, are cruising around surprisingly slowly, researchers found. Galactic mass and star velocities are linked, so the results could have big implications.

[Full Story: Milky Way Galaxy May Be Less Massive Than Thought]

Shark Fetus Detects Predators:

Baby sharks still developing within leathery egg cases can sense the electric fields of predators and freeze in place to avoid detection, researchers say.

These findings could help in developing more effective shark repellents, scientists said.

[Full Story: Plugged In: Shark Fetuses Detect Predators' Electric Fields]

Alien Asteroid Belt

Astronomers have discovered a giant asteroid belt circling the bright star Vega, a find that may ultimately reveal an entire solar system of planets, scientists say.

Vega is one of the brightest stars in the night sky and located about 25 light-years from Earth. It gained fame as the fictional source of an alien signal in the science fiction novel “Contact” by famed astronomer Carl Sagan, which was adapted into a film starring Jodie Foster.

[Full Story: Alien Asteroid Belt Discovery Hints at Hidden Planets]

Stellar Explosion

A beautiful new image snapped by a NASA spacecraft captures the aftermath of a massive star explosion with unprecedented resolution.

The image — taken by NASA's NuSTAR spacecraft (short for Nuclear Spectroscopic Telescope Array) in X-ray light — shows Cassiopeia-A, a supernova remnant located about 11,000 light-years from Earth.

[Full Story: Massive Star Explosion Captured in Stunning Photo ]

Mysterious Black Holes

A NASA space telescope snapped a new view of two oddball black holes shining ultra-bright in X-ray light in a distant spiral galaxy.

NASA’s NuSTAR X-ray observatory spotted the bright black holes while observing the galaxy Caldwell 5, which is located 7 million light-years from Earth in the constellation Camelopardalis (the Giraffe).

[Full Story: Mysteriously Bright Black Holes Revealed by NASA Telescope ]

Penguins Get Human Visit

The existence of a 9,000-strong colony of emperor penguins in East Antarctica has been confirmed by three people who visited it for the first time.

Signs of the penguins were spotted by satellite, which took images of large stains on the snow in 2009 that scientists suspected were penguin feces. But it wasn't until early December 2012 that three people from Belgium's Princess Elisabeth Antarctica polar research station visited the colony to glimpse the penguins for themselves, according to a statement from the International Polar Foundation, which runs the station.

[Full Story: Humans Visit Huge Penguin Colony for First Time]

Best Science Photos of the Week

Date: 12 January 2013 Time: 01:32 PM ET
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