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Day of remembrance: Space Shuttle Challenger disaster

January 28, 1986. On today’s date 30 years ago, the Space Shuttle Challenger (mission STS-51-L) exploded and broke apart 73 seconds into its flight, after an O-ring seal in its right solid rocket booster (SRB) failed at liftoff. The explosion led to the deaths of all seven Challenger crew members.

Mars will be awesome in 2016

EarthSky News with Deborah Byrd for January 28, 2016. Mars will be awesome in 2016. The loneliest exoplanet. Dark matter linked to galaxy clusters’ internal structure. A tribute to fallen NASA heroes.

Corona around the moon

View larger. | Photo by Sergio Emilio Montúfar Codoñer of Argentina who runs the popular Facebook page MilkyWayAddicted.

Photo by Sergio Emilio Montúfar Codoñer of Argentina.

These colorful rings of a lunar corona appear when we see the moon through a very thin cloud of similarly-sized water droplets.

Greatest-ever debris flow video

Dave Petley at the blog of the American Geophysical Union (AGU) nominates this landslide footage as the greatest-ever debris flow video. He wrote:

It starts slowly, but hang in there!

Dark matter linked to galaxy clusters’ internal structure

View larger. | This image from NASA's Hubble Space Telescope shows the inner region of Abell 1689, an immense cluster of galaxies. Scientists say the galaxy clusters we see today have resulted from fluctuations in the density of matter in the early universe. Image via NASA/ESA/JPL-Caltech/Yale/CNRS

View larger. | Hubble Space Telescope image of the inner region of Abell 1689, an giant cluster of galaxies. Image via NASA/ESA/JPL-Caltech/Yale/CNRS

A new study published this week in Physical Review Letters suggests that a galaxy’s cluster’s internal structure is linked to its dark matter environment. It’s the first time that a property besides the mass of a galaxy cluster has been linked with surrounding dark matter.

Why Planet Nine might be for real

Image credit: Image editor/Flickr

Image credit: Image editor/Flickr

Claims about new planets that turned out to be wrong – and why ‘Planet Nine’ may be different.

And now … a real ISS transit of Saturn

An apparently fake image ran in APOD a few days ago, but this video of an ISS transit across the face of Saturn looks real.

X-ray view of Earth’s aurora

X-ray aurora caught by ESA's Integral space observatory on November 10, 2015.

X-ray aurora caught by ESA’s Integral space observatory.

Did you know that auroras emit X-rays? This new image from ESA, released January 26, 2016, shows the X-ray component of an aurora caught by accident by the Integral space observatory in late 2015.

Daylight meteor over southeastern U.S.

View larger. | A portion of a heat map and ground trajectory of January 24, 2016 daylight meteor via the American Meteor Society.

Portion of a ‘heat map’ – showing location of witnesses or observers, and ground trajectory – of January 24, 2016, daylight meteor via the American Meteor Society.

The American Meteor Society has over 100 reports of a bright meteor seen in broad daylight over southeastern U.S. on Sunday. How to report it, if you saw it, here.

Loneliest known exoplanet and its star

The exoplanet labeled 2MASS J2126 has the widest orbit of any planet ever found. Its “year” is nearly 1 million Earth-years long.