Mes: junio 2019

What would it be like to fly over the asteroid Vesta? Animators from the German Aerospace Center took actual images and height data from NASA’s Dawn mission when it visited asteroid Vesta a few years ago and generated a virtual movie. The featured video begins with a sequence above Divalia Fossa, an unusual pair of troughs running parallel over heavily cratered terrain. Next, the virtual spaceship explores Vesta’s 60-km Marcia Crater, showing numerous vivid details. Last, Dawn images were digitally recast with exaggerated height to better reveal Vesta’s 5-km high mountain Aricia Tholus. The second largest object in the Solar System’s asteroid belt, Vesta is the brightest asteroid visible from Earth and can be found with binoculars. Using Vesta Trek, you can explore all over Vesta yourself. [via NASA] https://ift.tt/2IYbQIw

Big, bright, and beautiful, spiral galaxy M83 lies a mere twelve million light-years away, near the southeastern tip of the very long constellation Hydra. Prominent spiral arms traced by dark dust lanes and blue star clusters lend this galaxy its popular name, The Southern Pinwheel. But reddish star forming regions that dot the sweeping arms highlighted in this sparkling color composite also suggest another nickname, The Thousand-Ruby Galaxy. About 40,000 light-years across, M83 is a member of a group of galaxies that includes active galaxy Centaurus A. In fact, the core of M83 itself is bright at x-ray energies, showing a high concentration of neutron stars and black holes left from an intense burst of star formation. This sharp composite color image also features spiky foreground Milky Way stars and distant background galaxies. The image data was taken from the Subaru Telescope, the European Southern Observatory’s Wide Field Imager camera, and the Hubble Legacy Archive. [via NASA] https://ift.tt/2KMtX6K

The night of June 21 was the shortest night for planet Earth’s northern latitudes, so at latitude 48.9 degrees north, Paris was no exception. Still, the City of Light had an exceptionally luminous evening. Its skies were flooded with silvery night shining or noctilucent clouds after the solstice sunset. Hovering at the edge of space, the icy condensations on meteoric dust or volcanic ash are still in full sunlight at the extreme altitudes of the mesophere. Seen at high latitudes in summer months, stunning, wide spread displays of northern noctilucent clouds are now being reported. [via NASA] https://ift.tt/2X5OaWD

This persistent six month long exposure compresses the time from solstice to solstice (December 21, 2018 to June 16, 2019) into a single point of view. Dubbed a solargraph, the unconventional picture was recorded with a tall, tube-shaped pinhole camera using a piece of photographic paper. Fixed to a single spot at Casarano, Italy for the entire exposure, the simple camera continuously records the Sun’s daily path as a glowing trail burned into the photosensitive paper. Breaks and gaps in the trails are caused by cloud cover. At the end of the exposure, the paper was scanned to create the digital image. Of course, starting in December the Sun trails peak lower in the sky, near the northern hemisphere’s winter solstice. The trails trails climb higher as the days grow longer and the June 21st summer solstice approaches. [via NASA] https://ift.tt/2Lm3xb9

Sometimes it’s night on the ground but day in the air. As the Earth rotates to eclipse the Sun, sunset rises up from the ground. Therefore, at sunset on the ground, sunlight still shines on clouds above. Under usual circumstances, a pretty sunset might be visible, but unusual noctilucent clouds float so high up they can be seen well after dark. Normally too dim to be seen, they may become visible just after sunset during the summer when illuminated by sunlight from below. Noctilucent clouds are the highest clouds known and thought to be part of polar mesospheric clouds. Featured here as they appeared two weeks ago, a network of noctilucent clouds was captured not only in the distant sky but in reflection from a small lake just north of Zwolle, Netherlands, with trees in stark silhouette across the horizon. Unusually bright noctilucent clouds continue to appear over much of northern Europe. Much about noctilucent clouds has been discovered only over the past decade, while how they form and evolve remains a topic of active research. [via NASA] https://ift.tt/2J0jhha

Do you know the names of some of the brightest stars? It’s likely that you do, even though some bright stars have names so old they date back to near the beginning of written language. Many world cultures have their own names for the brightest stars, and it is culturally and historically important to remember them. In the interest of clear global communication, however, the International Astronomical Union (IAU) has begun to designate standardized star names. Featured above in true color are the 25 brightest stars in the night sky, currently as seen by humans, coupled with their IAU-recognized names. Some star names have interesting meanings, including Sirius («the scorcher» in Latin), Vega («falling» in Arabic), and Antares («rival to Mars» in Greek). It’s also likely that other of these bright star names are not familiar to you, even though familiar Polaris is too dim to make this list. [via NASA] https://go.nasa.gov/2FI27Ez

How do violent stars affect their surroundings? To help find out, astronomers created a 48-frame high-resolution, controlled-color panorama of the center of the Carina Nebula, one of the largest star forming regions on the night sky. The featured image, taken in 2007, was the most detailed image of the Carina Nebula yet taken. Cataloged as NGC 3372, the Carina Nebula is home to streams of hot gas, pools of cool gas, knots of dark globules, and pillars of dense dusty interstellar matter. The Keyhole Nebula, visible left of center, houses several of the most massive stars known. These large and violent stars likely formed in dark globules and continually reshape the nebula with their energetic light, outflowing stellar winds, and ultimately by ending their lives in supernova explosions. Visible to the unaided eye, the entire Carina Nebula spans over 450 light years and lies about 8,500 light-years away toward the constellation of Ship’s Keel (Carina). [via NASA] https://go.nasa.gov/2N5te2s

Today, the solstice is at 15:54 Universal Time, the Sun reaching the northernmost declination in its yearly journey through planet Earth’s sky. A June solstice marks the astronomical beginning of summer in the northern hemisphere and winter in the south. It also brings the north’s longest day, the longest period between sunrise and sunset. In fact the June solstice sun is near the top, at the most northern point in the analemma or figure 8 curve traced by the position of the Sun in this composite photo. The analemma was created (video) from images taken every 10 days at the same time from June 21, 2018 and June 7, 2019. The time was chosen to be the year’s earliest sunset near the December solstice, so the analemma’s lowest point just kisses the unobstructed sea horizon at the left. Sunsets arranged along the horizon toward the right (north) are centered on the sunset at the September equinox and end with sunset at the June solstice. [via NASA] https://go.nasa.gov/2NaEZV0

Big, bright, beautiful spiral, Messier 106 dominates this cosmic vista. The nearly two degree wide telescopic field of view looks toward the well-trained constellation Canes Venatici, near the handle of the Big Dipper. Also known as NGC 4258, M106 is about 80,000 light-years across and 23.5 million light-years away, the largest member of the Canes II galaxy group. For a far away galaxy, the distance to M106 is well-known in part because it can be directly measured by tracking this galaxy’s remarkable maser, or microwave laser emission. Very rare but naturally occurring, the maser emission is produced by water molecules in molecular clouds orbiting its active galactic nucleus. Another prominent spiral galaxy on the scene, viewed nearly edge-on, is NGC 4217 below and right of M106. The distance to NGC 4217 is much less well-known, estimated to be about 60 million light-years. [via NASA] https://go.nasa.gov/2Y3W18C

What’s the magnetic field like in the center of our Milky Way Galaxy? To help find out, NASA’s SOFIA — an observatory flying in a modified 747 — imaged the central region with an instrument known as HAWC+. HAWC+ maps magnetism by observing polarized infrared light emitted by elongated dust grains rotating in alignment with the local magnetic field. Now at our Milky Way’s center is a supermassive black hole with a hobby of absorbing gas from stars it has recently destroyed. Our galaxy’s black hole, though, is relatively quiet compared to the absorption rate of the central black holes in active galaxies. The featured image gives a clue as to why — a surrounding magnetic field may either channel gas into the black hole — which lights up its exterior, or forces gas into an accretion-disk holding pattern, causing it to be less active — at least temporarily. Inspection of the featured image — appearing perhaps like a surreal mashup of impasto art and gravitational astrophysics — brings out this telling clue by detailing the magnetic field in and around a dusty ring surrounding Sagittarius A*, the black hole in our Milky Way’s center. [via NASA] https://go.nasa.gov/2Iq6CFx