Highlights of the North Spring Sky


What can you see in the night sky this season? The featured graphic gives a few highlights for Earth‘s northern hemisphere. Viewed as a clock face centered at the bottom, early (northern) spring sky events fan out toward the left, while late spring 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, as usual, the Lyrids meteor shower will peak in mid-April. Also as usual, the International Space Station (ISS) can be seen, at times, as a bright spot drifting across the sky after sunset. After the Vernal Equinox next week, the length of daytime will be greater than the length of nighttime in Earth’s northern hemisphere, an inequality that will escalate as the spring season develops. Also as spring ages, Jupiter becomes visible increasingly earlier in the night. As spring draws to a close, the month of May will feature two full moons, the second of which is called a Blue Moon.

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The Central Magnetic Field of the Cigar Galaxy


Are galaxies giant magnets? Yes, but the magnetic fields in galaxies are typically much weaker than on Earth’s surface, as well as more complex and harder to measure. Recently, though, the HAWC+ instrument onboard the airborne (747) SOFIA observatory has been successful in detailing distant magnetic fields by observing infrared light polarized by reflection from dust grains. Featured here, HAWC+ observations of the M82, the Cigar galaxy, show that the central magnetic field is perpendicular to the disk and parallel to the strong supergalactic wind. This observation bolsters the hypothesis that M82’s central magnetic field helps its wind transport the mass of millions of stars out from the central star-burst region. The featured image shows magnetic field lines superposed on top of an optical light (gray) and hydrogen gas (red) image from Kitt Peak National Observatory, further combined with infrared images (yellow) from SOFIA and the Spitzer Space Telescope. The Cigar Galaxy is about 12 million light years distant and visible with binoculars towards the constellation of the Great Bear.

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Moonrise Through Mauna Keas Shadow


How can the Moon rise through a mountain? It cannot — what was photographed here is a moonrise through the shadow of a large volcano. The volcano is Mauna Kea, Hawai’i, USA, a frequent spot for spectacular photographs since it is one of the premier observing locations on planet Earth. The Sun has just set in the opposite direction, behind the camera. Additionally, the Moon has just passed full phase — were it precisely at full phase it would rise, possibly eclipsed, at the very peak of the shadow. The Moon is actually rising in the triangular shadow cone of the volcano, a corridor of darkness that tapers off in the distance like converging train tracks. The Moon is too large and too far away to be affected by the shadow of the volcano. Refraction of moonlight through the Earth’s atmosphere makes the Moon appear slightly oval. Cinder cones from old volcanic eruptions are visible in the foreground.

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Crescent Enceladus


Peering from the shadows, the Saturn-facing hemisphere of tantalizing inner moon Enceladus poses in this Cassini spacecraft image. North is up in the dramatic scene captured during November 2016 as Cassini’s camera was pointed in a nearly sunward direction about 130,000 kilometers from the moon’s bright crescent. In fact, the distant world reflects over 90 percent of the sunlight it receives, giving its surface about the same reflectivity as fresh snow. A mere 500 kilometers in diameter, Enceladus is a surprisingly active moon. Data collected during Cassini’s flybys and years of images have revealed the presence of remarkable south polar geysers and a possible global ocean of liquid water beneath an icy crust.

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Stardust and Starlight in M78


Interstellar dust clouds and bright nebulae abound in the fertile constellation of Orion. One of the brightest, M78, is near the center in this colorful telescopic view, covering an area north of Orion’s belt. At a distance of about 1,500 light-years, the bluish nebula itself is about 5 light-years across. Its blue tint is due to dust preferentially reflecting the blue light of hot, young stars in the region. Dark dust lanes and other nebulae can easily be traced through the gorgeous skyscape that includes many Herbig- Haro objects, energetic jets from stars in the process of formation. But missing from this image is McNeil’s nebula. A major discovery only recognized in 2004, the enigmatic, variable nebula was found along the dark lane of dust above and right of larger M78. McNeil’s nebula is associated with a protostar and seen to be sometimes present and sometimes absent in photos of the well-imaged region. McNeil’s nebula faded from view late last year and is still absent in this deep image recorded in February 2019.

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