Monday, January 18, 2021

A Lunar Corona with Jupiter and Saturn

Why does a cloudy moon sometimes appear colorful? The effect, called a lunar corona, is created by the quantum mechanical diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud. Since light of different colors has different wavelengths, each color diffracts differently. Lunar Coronae are one of the few quantum mechanical color effects that can be easily seen with the unaided eye. Solar coronae are also sometimes evident. The featured composite image was captured a few days before the close Great Conjunction between Saturn and Jupiter last month. In the foreground, the Italian village of Pieve di Cadore is visible in front of the Sfornioi Mountains. via NASA

Sunday, January 17, 2021

The Medulla Nebula Supernova Remnant

What powers this unusual nebula? CTB-1 is the expanding gas shell that was left when a massive star toward the constellation of Cassiopeia exploded about 10,000 years ago. The star likely detonated when it ran out of elements, near its core, that could create stabilizing pressure with nuclear fusion. The resulting supernova remnant, nicknamed the Medulla Nebula for its brain-like shape, still glows in visible light by the heat generated by its collision with confining interstellar gas. Why the nebula also glows in X-ray light, though, remains a mystery. One hypothesis holds that an energetic pulsar was co-created that powers the nebula with a fast outwardly moving wind. Following this lead, a pulsar has recently been found in radio waves that appears to have been expelled by the supernova explosion at over 1000 kilometers per second. Although the Medulla Nebula appears as large as a full moon, it is so faint that it took 130-hours of exposure with two small telescopes in New Mexico, USA, to create the featured image. via NASA

Saturday, January 16, 2021

Jets from Unusual Galaxy Centaurus A

The jets emanating from Centaurus A are over a million light years long. These jets of streaming plasma, expelled by a giant black hole in the center of this spiral galaxy, light up this composite image of Cen A. Exactly how the central black hole expels infalling matter remains unknown. After clearing the galaxy, however, the jets inflate large radio bubbles that likely glow for millions of years. If energized by a passing gas cloud, the radio bubbles can even light up again after billions of years. X-ray light is depicted in the featured composite image in blue, while microwave light is colored orange. The base of the jet in radio light shows details of the innermost light year of the central jet. via NASA

Friday, January 15, 2021

The Mountains of NGC 2174

This fantastic skyscape lies near the edge of NGC 2174 a star forming region about 6,400 light-years away in the nebula-rich constellation of Orion. It follows mountainous clouds of gas and dust carved by winds and radiation from the region's newborn stars, now found scattered in open star clusters embedded around the center of NGC 2174, off the top of the frame. Though star formation continues within these dusty cosmic clouds they will likely be dispersed by the energetic newborn stars within a few million years. Recorded at infrared wavelengths by the Hubble Space Telescope in 2014, the interstellar scene spans about 6 light-years. Scheduled for launch in 2021, the James Webb Space Telescope is optimized for exploring the Universe at infrared wavelengths. via NASA

Thursday, January 14, 2021

A Plutonian Landscape

This shadowy landscape of majestic mountains and icy plains stretches toward the horizon on a small, distant world. It was captured from a range of about 18,000 kilometers when New Horizons looked back toward Pluto, 15 minutes after the spacecraft's closest approach on July 14. The dramatic, low-angle, near-twilight scene follows rugged mountains formally known as Norgay Montes from foreground left, and Hillary Montes along the horizon, giving way to smooth Sputnik Planum at right. Layers of Pluto's tenuous atmosphere are also revealed in the backlit view. With a strangely familiar appearance, the frigid terrain likely includes ices of nitrogen and carbon monoxide with water-ice mountains rising up to 3,500 meters (11,000 feet). That's comparable in height to the majestic mountains of planet Earth. The Plutonian landscape is 380 kilometers (230 miles) across. via NASA

Wednesday, January 13, 2021

Aurora Slathers Up the Sky

Like salsa verde on your favorite burrito, a green aurora slathers up the sky in this 2017 June 25 snapshot from the International Space Station. About 400 kilometers (250 miles) above Earth, the orbiting station is itself within the upper realm of the auroral displays. Aurorae have the signature colors of excited molecules and atoms at the low densities found at extreme altitudes. Emission from atomic oxygen dominates this view. The tantalizing glow is green at lower altitudes, but rarer reddish bands extend above the space station's horizon. The orbital scene was captured while passing over a point south and east of Australia, with stars above the horizon at the right belonging to the constellation Canis Major, Orion's big dog. Sirius, alpha star of Canis Major, is the brightest star near the Earth's limb. via NASA

Tuesday, January 12, 2021

Arches Across an Arctic Sky

What are these two giant arches across the sky? Perhaps the more familiar one, on the left, is the central band of our Milky Way Galaxy. This grand disk of stars and nebulas here appears to encircle much of the southern sky. Visible below the stellar arch is the rusty-orange planet Mars and the extended Andromeda galaxy. For a few minutes during this cold artic night, a second giant arch appeared to the right, encircling part of the northern sky: an aurora. Auroras are much closer than stars as they are composed of glowing air high in Earth's atmosphere. Visible outside the green auroral arch is the group of stars popularly known as the Big Dipper. The featured digital composite of 18 images was captured in mid-December over the in Norway. via NASA