Have you seen Orion lately? The next few months will be the best for seeing this familiar constellation as it rises continually earlier in the night. However, Orion’s stars and nebulas won’t look quite as colorful to the eye as they do in this fantastic camera image. In the featured image, Orion was captured by camera showing its full colors last month over a Brazilian copal tree from Brazil‘s Central-West Region. Here the cool red giant Betelgeuse takes on a strong orange hue as the brightest star on the far left. Otherwise, Orion’s hot blue stars are numerous, with supergiant Rigel balancing Betelgeuse at the upper right, Bellatrix at the upper left, and Saiph at the lower right. Lined up in Orion’s belt (bottom to top) are Alnitak, Alnilam, and Mintaka all about 1,500 light-years away, born of the constellation’s well studied interstellar clouds. And if a “star” toward the upper right Orion’s sword looks reddish and fuzzy to you, it should. It’s the stellar nursery known as the Great Nebula of Orion.
The center of our Milky Way galaxy can be found some 26,000 light-years away toward the constellation Sagittarius. Even on a dark night, you can’t really see it though. Gaze in that direction, and your sight-line is quickly obscured by intervening interstellar dust. In fact, dark dust clouds, glowing nebulae, and crowded starfieds are packed along the fertile galactic plane and central regions of our galaxy. This annotated view, a mosaic of dark sky images, highlights some favorites, particularly for small telescope or binocular equipped skygazers. The cropped version puts the direction to the galactic center on the far right. It identifies well-known Messier objects like the Lagoon nebula (M8), the Trifid (M20), star cloud M24, and some of E.E. Barnard’s dark markings on the sky. A full version extends the view to the right toward the constellation Scorpius, in all covering over 20 degrees across the center of the Milky Way.
An old Moon rose this morning, its waning sunlit crescent shining just above the eastern horizon before sunrise. But earthshine, light reflected from a bright planet Earth, lit the shadowed portion of the lunar disk and revealed most of a familiar lunar near side to early morning risers. In fact, a description of earthshine in terms of sunlight reflected by Earth’s oceans illuminating the Moon’s dark surface was written over 500 years ago by Leonardo da Vinci. One lunation ago this old Moon also rose above the eastern horizon. Its sunlit crescent and da Vinci glow were captured in stacked exposures from the Badain Jilin Desert of Inner Mongolia, China on August 29, 2019. This year marks the 500th anniversary of Leondardo da Vinci’s death.
The Pelican Nebula is slowly being transformed. IC 5070, the official designation, is divided from the larger North America Nebula by a molecular cloud filled with dark dust. The Pelican, however, receives much study because it is a particularly active mix of star formation and evolving gas clouds. The featured picture was produced in three specific colors — light emitted by sulfur, hydrogen, and oxygen — that can help us to better understand these interactions. The light from young energetic stars is slowly transforming the cold gas to hot gas, with the advancing boundary between the two, known as an ionization front, visible in bright orange on the right. Particularly dense tentacles of cold gas remain. Millions of years from now this nebula might no longer be known as the Pelican, as the balance and placement of stars and gas will surely leave something that appears completely different.
What are these strange shapes on Mars? Defrosting sand dunes. As spring dawned on the Northern Hemisphere of Mars, dunes of sand near the pole, as pictured here in late May by ESA’s ExoMars Trace Gas Orbiter, began to thaw. The carbon dioxide and water ice actually sublime in the thin atmosphere directly to gas. Thinner regions of ice typically defrost first revealing sand whose darkness soaks in sunlight and accelerates the thaw. The process might even involve sandy jets exploding through the thinning ice. By summer, spots will expand to encompass the entire dunes. The Martian North Pole is ringed by many similar fields of barchan sand dunes, whose strange, smooth arcs are shaped by persistent Martian winds.
Today is an equinox, a date when day and night are equal. Tomorrow, and every day until the next equinox, the night will be longer than the day in Earth’s northern hemisphere, and the day will be longer than the night in Earth’s southern hemisphere. An equinox occurs midway between the two solstices, when the days and nights are the least equal. The featured picture is a composite of hourly images taken of the Sun above Bursa, Turkey on key days from solstice to equinox to solstice. The bottom Sun band was taken during the north’s winter solstice in 2007 December, when the Sun could not rise very high in the sky nor stay above the horizon very long. This lack of Sun caused winter. The top Sun band was taken during the northern summer solstice in 2008 June, when the Sun rose highest in the sky and stayed above the horizon for more than 12 hours. This abundance of Sun caused summer. The middle band was taken during an equinox in 2008 March, but it is the same sun band that Earthlings see today, the day of the most recent equinox.
Still bright in planet Earth’s night skies, good telescopic views of Saturn and its beautiful rings often make it a star at star parties. But this stunning view of Saturn’s rings and night side just isn’t possible from telescopes closer to the Sun than the outer planet. They can only bring Saturn’s day into view. In fact, this image of Saturn’s slender sunlit crescent with night’s shadow cast across its broad and complex ring system was captured by the Cassini spacecraft. A robot spacecraft from planet Earth, Cassini called Saturn orbit home for 13 years before it was directed to dive into the atmosphere of the gas giant on September 15, 2017. This magnificent mosaic is composed of frames recorded by Cassini’s wide-angle camera only two days before its grand final plunge. Saturn’s night will not be seen again until another spaceship from Earth calls.