A multihued aurora ripples across the night sky over Tromsø, Norway, on January 19. Auroras happen when high-energy particles from the sun slam into Earth's atmosphere, exciting gas molecules in the air and causing them to emit light. The colors seen depend on the type of molecules involved and the altitude at which the most interactions are happening. Green is the most common shade for auroras and is produced by oxygen molecules at relatively low altitudes—between 62 and 186 miles. (Photo courtesy of Jessica Holle via Flickr)
Since the Rosetta spacecraft's historic arrival at Comet 67P/Churyumov–Gerasimenko last August, mission scientists have been hard at work deciphering clues from the probe's suite of cameras. As part of a suite of studies released on January 22, the team revealed that the comet has a rather prominent crack in its neck. The 1,640-foot fracture runs roughly parallel to the midsection that connects the two lobes of the duck-shaped comet. The scientists aren't yet sure what caused the crack, although they think other fractures elsewhere on the object are created due to the rapid heating and cooling experienced during the comet's 12.4-hour day. (ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)
The UN has named 2015 the International Year of Light, and to mark the occasion NASA's Chandra X-Ray Observatory has released a new batch of images that use multiple kinds of light to truly illuminate cosmic wonders. This shot shows the complex structure of the radio galaxy Cygnus A, which lies about 700 million light-years from Earth. Chandra's x-ray eye captured the bubble of hot gases seen in blue, while radio data from the NSF's Very Large Array reveal two red jets of radiation spurting from the black hole at the galaxy's heart. The background of golden stars was provided by visible light images from the Hubble Space Telescope and the Digitized Sky Survey. (X-ray: NASA/CXC/SAO; Optical: NASA/STScI; Radio: NSF/NRAO/AUI/VLA)
This surreal view of a cratered landscape is the latest high-resolution release from the European probe Mars Express, which has been studying the red planet's geology and atmosphere since 2003. The image, posted on January 22, shows a region called Nili Fossae, which contains a network of troughs likely formed after a major impact. Nili Fossae is intriguing to scientists because it contains a wide diversity of minerals, such as clays and opals, that can help geologists trace the planet's history. (ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO)
Europe's Venus Express orbiter may be dead, but it's still offering up intriguing views of Earth's "evil twin" from beyond the grave. This ethereal image released on January 19 shows the planet's south polar vortex, a turbulent mass of atmospheric gases about 37 miles above the planet's surface. Data from Venus Express suggests that the cyclone-like storm is a long-lived feature on Venus, but one that is constantly changing its structure. Studying the shape-shifting vortex may offer clues to a lingering mystery: why Venus's thick atmosphere rotates about 60 times faster than the solid planet below. (ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Univ. Oxford)
Italian astronaut Samantha Cristoforetti captured this shot of Cyclone Bansi with its eye aglow on January 17. From her perch aboard the International Space Station, Cristoforetti was able to see the bulk of the storm swirling over the south Indian Ocean, illuminated by intense lightning. The green band along Earth's limb is a phenomenon called airglow. During the day, ultraviolet light from the sun knocks electrons off gas atoms in Earth's atmosphere. At night the ionized atoms and free electrons re-combine, a process that creates a subtle glow often seen in images of nighttime Earth from space. (Samantha Cristoforetti, via Twitter)
On January 19, NASA unveiled this shot of the sun—the 100 millionth picture snapped by the Atmospheric Imaging Assembly instrument onboard the Solar Dynamics Observatory. This sun-watching satellite has been gathering high-resolution data in multiple wavelengths since 2010, revealing details about solar activity and Earth-sun interactions. This milestone image shows plasma in the turbulent upper atmosphere, or corona, undulating around two dark coronal holes, regions where the sun has lost material, making the gas less dense. (NASA/SDO/AIA/LMSAL)

These Celestial Highlights Include Flowing Auroras and a Cracked Comet

Catch up on the week’s best space images, from a cyclone’s glowing eye to a surreal Martian vista

smithsonian.com

A ribbon of auroral light shines in Norway, a European comet-chaser gives up some of its early surprises, a galaxy shows off its radio jets and more in the best space-related photos released this week.

About Victoria Jaggard

Victoria Jaggard is the science editor for Smithsonian.com. Her writing has appeared in Chemical & Engineering News, National Geographic, New Scientist and elsewhere.

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