Perseids from Perseus

Where are all these meteors coming from? In terms of direction on the sky, the pointed answer is the constellation of Perseus. That is why the meteor shower that peaks tomorrow night is known as the Perseids — the meteors all appear to came from a radiant toward Perseus. In terms of parent body, though, the sand-sized debris that makes up the Perseids meteors come from Comet Swift-Tuttle. The comet follows a well-defined orbit around our Sun, and the part of the orbit that approaches Earth is superposed in front of the Perseus. Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Perseus. Featured here, a composite image taken over eight nights and containing over 400 meteors from last August’s Perseids meteor shower shows many bright meteors that streaked over Kolonica Observatory in Slovakia. This year’s Perseids holds promise to be one of the best meteor showers of the year. [via NASA]

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]

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]

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]

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]

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]

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]

Did the Earth part to show us this comet? Of course not, even if this image makes it seem that way. Pictured far in the background is Comet NEOWISE as it appeared about two weeks ago over northern Greece. Above the comet are many stars including the bright stars of the Big Dipper (also the Sorcerer, in Aztec mythology), an asterism that many people around the world used to find the naked-eye comet as it hovered in the northern sky over the past month. In the foreground is Vikos Gorge, the deepest gorge on Earth, relative to its width. The gorge was slowly created by erosion from the Voidomatis River over the past few million years. Capturing this image took a lot of planning, waiting, luck, braving high winds, and avoiding local wolves. Comet C/2020 F3 (NEOWISE) continues to fade and is now best visible through binoculars as it coasts back to the outer Solar System. [via NASA]

How different does sunset appear from Mars than from Earth? For comparison, two images of our common star were taken at sunset, one from Earth and one from Mars. These images were scaled to have same angular width and featured here side-by-side. A quick inspection will reveal that the Sun appears slightly smaller from Mars than from Earth. This makes sense since Mars is 50% further from the Sun than Earth. More striking, perhaps, is that the Martian sunset is noticeably bluer near the Sun than the typically orange colors near the setting Sun from Earth. The reason for the blue hues from Mars is not fully understood, but thought to be related to forward scattering properties of Martian dust. The terrestrial sunset was taken in 2012 March from Marseille, France, while the Martian sunset was captured in 2015 by NASA’s robotic Curiosity rover from Gale crater on Mars. Last week a new rover and a helicopter — onboard Mars 2020 — launched for Mars. [via NASA]

The Elephant’s Trunk Nebula in Cepheus

Like an illustration in a galactic Just So Story, the Elephant’s Trunk Nebula winds through the emission nebula and young star cluster complex IC 1396, in the high and far off constellation of Cepheus. Also known as vdB 142, the cosmic elephant’s trunk is over 20 light-years long. This detailed close-up view was recorded through narrow band filters that transmit the light from ionized hydrogen and oxygen atoms in the region. The resulting composite highlights the bright swept-back ridges that outline pockets of cool interstellar dust and gas. Such embedded, dark, tendril-shaped clouds contain the raw material for star formation and hide protostars within. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a large region on the sky, spanning over 5 degrees. This dramatic scene spans a 1 degree wide field of view though, about the size of 2 Full Moons. [via NASA]