A luminous Milky Way falls toward the horizon in this deep skyscape, starting at the top of the frame from the stars of the Southern Cross and the dark Coalsack Nebula. Captured in the dark predawn of February 2nd from Central Victoria, Australia, planet Earth, the 26 day old waning crescent Moon still shines brightly near the horizon. The second and third brightest celestial beacons are Venus and Jupiter along the lower part of the Milky Way’s central bulge. Almost in line with the brighter planets and Moon, Saturn is the pinprick of light just visible below and right of the lunar glow. Australia’s first astronomers saw the elongated, bulging shape of the familiar Milky Way as a great celestial Emu. The Moon and planets could almost be the Emu’s eggs on this starry night.
Clouds of glowing hydrogen gas fill this colorful skyscape in the faint but fanciful constellation Monoceros, the Unicorn. A star forming region cataloged as NGC 2264, the complex jumble of cosmic gas and dust is about 2,700 light-years distant and mixes reddish emission nebulae excited by energetic light from newborn stars with dark interstellar dust clouds. Where the otherwise obscuring dust clouds lie close to the hot, young stars they also reflect starlight, forming blue reflection nebulae. The telescopic image spans about 3/4 degree or nearly 1.5 full moons, covering 40 light-years at the distance of NGC 2264. Its cast of cosmic characters includes the the Fox Fur Nebula, whose dusty, convoluted pelt lies near the top, bright variable star S Monocerotis immersed in the blue-tinted haze near center, and the Cone Nebula pointing in from the right side of the frame. Of course, the stars of NGC 2264 are also known as the Christmas Tree star cluster. The triangular tree shape is seen on its side here. Traced by brighter stars it has its apex at the Cone Nebula. The tree’s broader base is centered near S Monocerotis.
Watch Juno zoom past Jupiter again. NASA‘s robotic spacecraft Juno is continuing on its 53-day, highly-elongated orbits around our Solar System’s largest planet. The featured video is from perijove 16, the sixteenth time that Juno has passed near Jupiter since it arrived in mid-2016. Each perijove passes near a slightly different part of Jupiter’s cloud tops. This color-enhanced video has been digitally composed from 21 JunoCam still images, resulting in a 125-fold time-lapse. The video begins with Jupiter rising as Juno approaches from the north. As Juno reaches its closest view — from about 3,500 kilometers over Jupiter’s cloud tops — the spacecraft captures the great planet in tremendous detail. Juno passes light zones and dark belt of clouds that circle the planet, as well as numerous swirling circular storms, many of which are larger than hurricanes on Earth. As Juno moves away, the remarkable dolphin-shaped cloud is visible. After the perijove, Jupiter recedes into the distance, now displaying the unusual clouds that appear over Jupiter’s south. To get desired science data, Juno swoops so close to Jupiter that its instruments are exposed to very high levels of radiation.
Massive stars profoundly affect their galactic environments. Churning and mixing interstellar clouds of gas and dust, stars — most notably those upwards of tens of times the mass of our Sun — leave their mark on the compositions and locations of future generations of stars. Dramatic evidence of this is illustrated in our neighboring galaxy, the Large Magellanic Cloud (LMC), by the featured nebula, Henize 70 (also known as N70 and DEM301). Henize 70 is actually a luminous superbubble of interstellar gas about 300 light-years in diameter, blown by winds from hot, massive stars and supernova explosions, with its interior filled with tenuous hot and expanding gas. Because superbubbles can expand through an entire galaxy, they offer humanity a chance to explore the connection between the lifecycles of stars and the evolution of galaxies.
Why would the sky look like a giant fan? Airglow. The featured intermittent green glow appeared to rise from a lake through the arch of our Milky Way Galaxy, as captured during 2015 next to Bryce Canyon in Utah, USA. The unusual pattern was created by atmospheric gravity waves, ripples of alternating air pressure that can grow with height as the air thins, in this case about 90 kilometers up. Unlike auroras powered by collisions with energetic charged particles and seen at high latitudes, airglow is due to chemiluminescence, the production of light in a chemical reaction. More typically seen near the horizon, airglow keeps the night sky from ever being completely dark.
The silhouette of an intriguing dark nebula inhabits this cosmic scene. Lynds’ Dark Nebula (LDN) 1622 appears against a faint background of glowing hydrogen gas only easily seen in long telescopic exposures of the region. LDN 1622 lies near the plane of our Milky Way Galaxy, close on the sky to Barnard’s Loop, a large cloud surrounding the rich complex of emission nebulae found in the Belt and Sword of Orion. But the obscuring dust of LDN 1622 is thought to be much closer than Orion’s more famous nebulae, perhaps only 500 light-years away. At that distance, this 1 degree wide field of view would span less than 10 light-years. Its foreboding appearance lends this dark expanse a popular name, the Boogeyman Nebula.
Spiral galaxy pair NGC 4567 and NGC 4568 share this sharp cosmic vista with lonely elliptical galaxy NGC 4564. All are members of the large Virgo Galaxy Cluster. With their classic spiral arms, dust lanes, and star clusters, the eye-catching spiral pair is also known as the Butterfly Galaxies or the Siamese Twins. Very close together, the galaxy twins don’t seem to be too distorted by gravitational tides. Their giant molecular clouds are known to be colliding though and are likely fueling the formation of massive star clusters. The galaxy twins are about 52 million light-years distant, while their bright cores appear separated by about 20,000 light-years. Of course, the spiky foreground stars lie within our own Milky Way.