Fresh Tiger Stripes on Saturn's Enceladus - Astronomy picture of the day - 2018 July 1

Fresh Tiger Stripes on Saturn's Enceladus 
Image Credit: NASA, ESA, JPL, SSI, Cassini Imaging Team

Explanation: Do underground oceans vent through the tiger stripes on Saturn's moon Enceladus? Long features dubbed tiger stripes are known to be spewing ice from the moon's icy interior into space, creating a cloud of fine ice particles over the moon's South Pole and creating Saturn's mysterious E-ring. Evidence for this has come from the robot Cassini spacecraft that orbited Saturn from 2004 to 2017. Pictured here, a high resolution image of Enceladus is shown from a close flyby. The unusual surface features dubbed tiger stripes are visible in false-color blue. Why Enceladus is active remains a mystery, as the neighboring moon Mimas,approximately the same size, appears quite dead. Arecent analysis of ejected ice grains has yielded evidence that complex organic molecules exist inside Enceladus. These large carbon-rich molecules bolster -- but do not prove -- that oceans under Enceladus' surface could contain life.

Curiosity's Dusty Self - Astronomy picture of the day - 2018 June 28

Curiosity's Dusty Self 
Image Credit: NASA, JPL-Caltech, MSSS, Curiosity Mars Rover

Explanation: Winds on Mars can't actually blow spacecraft over. But in the low gravity, martian winds can loft fine dust particles in planet-wide storms, like the dust storm now raging on the Red Planet. From the martian surface on sol 2082 (June 15), this self-portrait from the Curiosity rover shows the effects of the dust storm, reducing sunlight and visibility at the rover's location in Gale crater. Made with the Mars Hand Lens Imager, its mechanical arm is edited out of the mosaicked images. Curiosity's recent drill site Duluth can be seen on the rock just in front of the rover on the left. The east-northeast Gale crater rim fading into the background is about 30 kilometers away. Curiosity is powered by a radioisotope thermoelectric generator and is expected to be unaffected by the increase in dust at Gale crater. On the other side of Mars, the solar-powered Opportunity rover has ceased its operations due to the even more severe lack of sunlight at its location on the west rim of Endeavour crater.

Highlights of the Summer Sky - Astronomy picture of the day - 2018 June 27

Highlights of the Summer Sky 
Illustration Credit & Copyright: Universe2go.com

Explanation: What can you see in the night sky this summer? The featured graphic gives a few highlights for Earth's northern hemisphere. Viewed as a clock face centered at the bottom, early (northern) summer sky events fan out toward the left, while late summer events are projected toward the right. Objects relatively close to Earth are illustrated, in general, as nearer to the cartoon figure with the telescope at the bottom center -- although almost everything pictured can be seen without a telescope. As happens during any season, constellations appear the same year to year, and meteor showers occur on or near the same dates. For example, like last year, the stars of the Summer Trianglewill be nighttime icons for most the season, while the Perseids meteor shower will peak in mid-August, as usual. Highlights specific to this summer's sky include that Jupiter will be visible after sunset during June, and Venus will shine brightly in the evening sky during July and August. Saturn and Mars should be visible during much of this season's night, with Saturn appearing in the direction opposite the Sun in late June, and Mars at opposition in late July. Finally, atotal lunar eclipse should be visible to anyone who can see the Moon in late July.

Dark Nebulas across Taurus - Astronomy picture of the day - 2018 June 26

Dark Nebulas across Taurus 
Image Processing & Copyright: Oliver Czernetz - Data: Digitized Sky Survey (POSS-II)

Explanation: Sometimes even the dark dust of interstellar space has a serene beauty. One such place occurs toward the constellation of Taurus. The filaments featured here can be found on the sky between the Pleiades star clusterand the California Nebula. This dust is not known not for its bright glow but for its absorption and opaqueness. Several bright stars are visible with their blue light seen reflecting off the brown dust. Other stars appear unusually red as their light barely peaks through a column of dark dust, with red the color that remains after the blue is scattered away. Yet other stars are behind dust pillars so thick they are not visible here. Although appearing serene, the scene is actually an ongoing loop of tumult and rebirth. This is because massive enough knots of gas and dust will gravitationally collapse to form new stars -- stars that both create new dust in their atmospheres and destroy old dust with their energetic light and winds.

Antonio Vivaldi - "L'estate" - Slides - Musica

"L'estate"

Galaxy in a Crystal Ball - Astronomy picture of the day - 2018 June 22

Galaxy in a Crystal Ball 
Image Credit & Copyright: Juan Carlos Munoz

Explanation: A small crystal ball seems to hold a whole galaxy in this creative snapshot. Of course, the galaxy is our own Milky Way. Its luminous central bulge marked by rifts of interstellar dust spans thousands of light-years. On this long southern hemisphere night it filled dark Chilean skies over Paranal Observatory. The single exposure image did not require a Very Large Telescope, though. Experiments with a digital camera on a tripod and crystal ball perched on a handrail outside the Paranal Residencia produced the evocative, cosmic marble portrait of our home galaxy.

Northern Lights and Noctilucent Clouds - Astronomy picture of the day - 2018 June 21

Northern Lights and Noctilucent Clouds 
Image Credit & Copyright: Adrien Mauduit

Explanation: Luminous 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. Formed near the edge of space, the icy apparitions are condensations on meteoric dust or volcanic ash still in sunlight at extreme altitudes. Also near the edge of space on this short northern night, solar activity triggered the lovely apparition of aurora borealis or northern lights.

Pillars of the Eagle Nebula in Infrared - Astronomy picture of the day - 2018 June 20

Pillars of the Eagle Nebula in Infrared 
Image Credit: NASA, ESA, Hubble, HLA; Processing: Lluís Romero

Explanation: Newborn stars are forming in the Eagle Nebula. Gravitationally contracting in pillars of dense gas and dust, the intense radiation of these newly-formed bright stars is causing surrounding material to boil away. This image, taken with the Hubble Space Telescope in near infrared light, allows the viewer to see through much of the thick dust that makes the pillars opaque in visible light. The giant structures are light years in length and dubbed informally thePillars of Creation. Associated with the open star cluster M16, the Eagle Nebula lies about 6,500 light years away. The Eagle Nebula is an easy target for small telescopes in a nebula-rich part of the sky toward the split constellationSerpens Cauda (the tail of the snake).

Ancients of Sea and Sky - Astronomy picture of the day - 2018 June 19

Ancients of Sea and Sky 
Image Credit & Copyright: Jingyi Zhang

Explanation: They may look like round rocks, but they're alive. Moreover, they are modern versions of one of the oldest known forms of life: stromatolites. Fossils indicate that stromatolites appeared on Earth about 3.7 billion years ago -- even before many of the familiar stars in the modern night sky were formed. In the featured image taken in Western Australia, only the ancient central arch of our Milky Way Galaxy formed earlier. Even the Magellanic Clouds, satellite galaxies of our Milky Way and visible in the featured image below the Milky Way's arch, didn't exist in their current form when stromatolites first grew on Earth. Stromatolites are accreting biofilms of billions of microorganismsthat can slowly move toward light. Using this light to liberate oxygen into the air, ancient stromatolites helped make Earth hospitable to other life forms including, eventually, humans.

An Active Prominence on the Sun - Astronomy picture of the day - 2018 June 18

An Active Prominence on the Sun 
Video Credit: Chuck Ayoub (Chuck's Astrophotography)

Explanation: Sometimes the Sun's surface becomes a whirlwind of activity. Pictured is a time-lapse video of the Sun's surface taken over a two hour period in early May, run both forwards and backwards. The Sun's surface was blocked out so that details over the edge could be imaged in greater detail. Hot plasma is seen swirling over the solar limb in an ongoing battle between changing magnetic fields and constant gravity. The featured prominence rises about one Earth-diameter over the Sun's surface. Energetic events like this are becoming less common as the Sun nears a minimum in its 11-year activity cycle.