Saturday, August 8, 2020

The Origin of Elements

The hydrogen in your body, present in every molecule of water, came from the Big Bang. There are no other appreciable sources of hydrogen in the universe. The carbon in your body was made by nuclear fusion in the interior of stars, as was the oxygen. Much of the iron in your body was made during supernovas of stars that occurred long ago and far away. The gold in your jewelry was likely made from neutron stars during collisions that may have been visible as short-duration gamma-ray bursts or gravitational wave events. Elements like phosphorus and copper are present in our bodies in only small amounts but are essential to the functioning of all known life. The featured periodic table is color coded to indicate humanity's best guess as to the nuclear origin of all known elements. The sites of nuclear creation of some elements, such as copper, are not really well known and are continuing topics of observational and computational research. via NASA

Friday, August 7, 2020

Crescent Saturn

From Earth, Saturn never shows a crescent phase. But when viewed from a spacecraft the majestic giant planet can show just a sunlit slice. This image of crescent Saturn in natural color was taken by the robotic Cassini spacecraft in 2007. It captures Saturn's rings from the side of the ring plane opposite the Sun -- the unilluminated side -- another vista not visible from Earth. Visible are subtle colors of cloud bands, the complex shadows of the rings on the planet, and the shadow of the planet on the rings. The moons Mimas, at 2 o'clock, and Janus 4 o'clock, can be seen as specks of light, but the real challenge is to find Pandora (8 o'clock). From Earth, Saturn's disk is nearly full now and opposite the Sun. Along with bright fellow giant planet Jupiter it rises in the early evening. via NASA

Thursday, August 6, 2020

The Pipe Nebula

East of Antares, dark markings sprawl through crowded star fields toward the center of our Milky Way Galaxy. Cataloged in the early 20th century by astronomer E. E. Barnard, the obscuring interstellar dust clouds include B59, B72, B77 and B78, seen in against the starry background. Here, their combined shape suggests a pipe stem and bowl, and so the dark nebula's popular name is the Pipe Nebula. The deep and expansive view covers a full 10 by 10 degree field in the pronounceable constellation Ophiuchus. The Pipe Nebula is part of the Ophiuchus dark cloud complex located at a distance of about 450 light-years. Dense cores of gas and dust within the Pipe Nebula are collapsing to form stars. via NASA

NASA’s MAVEN Observes Martian Night Sky Pulsing in Ultraviolet Light

Vast areas of the Martian night sky pulse in ultraviolet light, according to images from NASA’s MAVEN spacecraft. The results are being used to illuminate complex circulation patterns in the Martian atmosphere. via

Wednesday, August 5, 2020

Messier 20 and 21

The beautiful Trifid Nebula, also known as Messier 20, is easy to find with a small telescope in the nebula rich constellation Sagittarius. About 5,000 light-years away, the colorful study in cosmic contrasts shares this well-composed, nearly 1 degree wide field with open star cluster Messier 21 (right). Trisected by dust lanes the Trifid itself is about 40 light-years across and a mere 300,000 years old. That makes it one of the youngest star forming regions in our sky, with newborn and embryonic stars embedded in its natal dust and gas clouds. Estimates of the distance to open star cluster M21 are similar to M20's, but though they share this gorgeous telescopic skyscape there is no apparent connection between the two. In fact, M21's stars are much older, about 8 million years old. via NASA

Tuesday, August 4, 2020

Ancient sun daggers will not hurt you, but they may tell you the time.  A sun dagger is a dagger-shaped gap in a shadow created by sunlight streaming through a crevice in a nearby rock. Starting over a thousand year ago, native people of the American southwest carved spiral petroglyphs into rocks that became illuminated by sun daggers in different ways as the Sun shifts in the sky. A type of sundial, where the end of the sundagger points in the spiral at high noon (for example) indicates a time of year, possibly illuminating a solstice or equinox.  Sun daggers are thought to have been used by Sun Priests during lone vigils with prayers and offerings.  Of the few known, the featured video discusses the historic Picture Rocks Sun Dagger near Tucson, Arizona, USA, likely created by a Hohokam Sun Priest around 1000 AD.  via NASA

Monday, August 3, 2020

Distorted galaxy NGC 2442 can be found in the southern constellation of the flying fish, (Piscis) Volans. Located about 50 million light-years away, the galaxy's two spiral arms extending from a pronounced central bar have a hook-like appearance in wide-field images. But this mosaicked close-up, constructed from Hubble Space Telescope and European Southern Observatory data, follows the galaxy's structure in amazing detail. Obscuring dust lanes, young blue star clusters and reddish star forming regions surround a core of yellowish light from an older population of stars. The sharp image data also reveal more distant background galaxies seen right through NGC 2442's star clusters and nebulae. The image spans about 75,000 light-years at the estimated distance of NGC 2442. via NASA