Shelf Cloud Over Saskatchewan
21.01.2008

Perhaps it's time to go inside. Such thoughts might occur to people witnessing the approach of an impressive shelf cloud. Shelf clouds are typically seen leading thunderstorms, although they may precede any well defined front of relatively cold air.

Clouds and the Moon Move to Block the Sun
18.06.2003

High above a small church near Vienna, Austria, clouds and the Moon vied for position in front of the Sun. Such was the case on the ground late last month during a partial eclipse of the Sun visible throughout Europe and Asia.

Molecular Clouds in the Carina Nebula
1.10.2019

They are not alive -- but they are dying. The unusual forms found in the Carina nebula, a few of which are featured here, might best be described as evaporating. Energetic light and winds from nearby stars are breaking apart the dark dust grains that make the iconic forms opaque.

A Galactic Mushroom Cloud
2.02.1999

Part of our Galaxy is exploding. Recent radio observations show new details of hot gas expanding rapidly from an energetic star-forming region in our Galactic disk out into our Galaxy's halo. The combined power of at least hundreds of supernovae is needed to drive this tremendous expansion.

A Roll Cloud Over Missouri
16.01.2006

What kind of cloud is this? A roll cloud. These rare long clouds may form near advancing cold fronts. In particular, a downdraft from an advancing storm front can cause moist warm air to rise, cool below its dew point, and so form a cloud.

Mammatus Clouds Over Olympic Valley
19.02.2011

What's happened to these clouds? Normal cloud bottoms are flat because moist warm air that rises and cools will condense into water droplets at a very specific temperature, which usually corresponds to a very specific height. After water droplets form that air becomes an opaque cloud.

Northern Lights and Noctilucent Clouds
20.06.2018

Skies after the near-solstice sunset on June 17 are reflected in this calm lake. The tranquil twilight scene was captured near Bashaw, Alberta, Canada, northern planet Earth. Usually spotted at high latitudes in summer months, night shining or noctilucent clouds hang just above the horizon, transfusing light into a darker sky.

Dark Cloud
25.02.1999

Ominously foreshadowing events to come, a dark cloud of obscuring dust stands out against a luminous star field in the Milky Way. Cataloged as Feitzinger and Stuwe object "1-457" this fuliginous interstellar nebula is relatively close - possibly only 1,000 light-years distant.

An Iridescent Cloud Over Colorado
24.11.2007

Why would a cloud appear to be different colors? A relatively rare phenomenon known as iridescent clouds can show unusual colors vividly or a whole spectrum of colors simultaneously. These clouds are formed of small water droplets of nearly uniform size.

Illuminated Cloud Trails Above Greece
14.03.2010

It may appear to be day, but it's night. Those wondrous orange streaks may appear to be rays from the setting Sun, but they're actually thin clouds illuminated by the Moon as they quickly streaked toward the distant horizon.