Sometimes falling ice crystals make the atmosphere into a giant lens causing arcs and halos to appear around the Sun or Moon. One Saturday night in 2012 was just such a time near Madrid, Spain, where a winter sky displayed not only a bright Moon but four rare lunar halos. The brightest object, near the top of the featured image, is the Moon. Light from the Moon refracts through tumbling hexagonal ice crystals into a somewhat rare 22-degree halo seen surrounding the Moon. Elongating the 22-degree arc horizontally is a more rare circumscribed halo caused by column ice crystals. Even more rare, some moonlight refracts through more distant tumbling ice crystals to form a (third) rainbow-like arc 46 degrees from the Moon and appearing here just above a picturesque winter landscape. Furthermore, part of a whole 46-degree circular halo is also visible, so that an extremely rare — especially for the Moon — quadruple halo was captured. Far in the background is a famous winter skyscape that includes Sirius, the belt of Orion, and Betelgeuse — visible between the inner and outer arcs. Halos and arcs typically last for minutes to hours, so if you do see one there should be time to invite family, friends or neighbors to share your unusual lensed vista of the sky.
Every Full Moon of 2021 shines in this year-spanning astrophoto project, a composite portrait of the familiar lunar nearside at each brightest lunar phase. Arranged by moonth, the year progresses in stripes beginning at the top. Taken with the same camera and lens the stripes are from Full Moon images all combined at the same pixel scale. The stripes still looked mismatched, but they show that the Full Moon’s angular size changes throughout the year depending on its distance from Kolkata, India, planet Earth. The calendar month, a full moon name, distance in kilometers, and angular size is indicated for each stripe. Angular size is given in minutes of arc corresponding to 1/60th of a degree. The largest Full Moon is near a perigee or closest approach in May. The smallest is near an apogee, the most distant Full Moon in December. Of course the full moons of May and November also slid into Earth’s shadow during 2021’s two lunar eclipses.
This timelapse gif tracks the James Webb Space Telescope as it streaks across the stars of Orion on its journey to a destination beyond the Moon. Recorded on December 28, 12 consecutive exposures each 10 minutes long were aligned and combined with a subsequent color image of the background stars to create the animation. About 2.5 days after its December 25 launch, JWST cruised past the altitude of the Moon’s orbit as it climbed up the gravity ridge from Earth to reach a halo orbit around L2, an Earth-Sun Lagrange point. Lagrange points are convenient locations in space where the combined gravitational attraction of one massive body (Earth) orbiting another massive body (Sun) is in balance with the centripetal force needed to move along with them. So much smaller masses, like spacecraft, will tend to stay there. One of 5 Lagrange points, L2 is about 1.5 million kilometers from Earth directly along the Earth-Sun line. JWST will arrive at L2 on January 23, 29 days after launch. While relaxing in Earth’s surface gravity you can follow the James Webb Space Telescope’s progress and complicated deployment online.
Comet Leonard, brightest comet of 2021, is at the lower left of these two panels captured on December 29 in dark Atacama desert skies. Heading for its perihelion on January 3 Comet Leonard’s visible tail has grown. Stacked exposures with a wide angle lens (also displayed in a reversed B/W scheme for contrast), trace the complicated ion tail for an amazing 60 degrees, with bright Jupiter shining near the horizon at lower right. Material vaporizing from Comet Leonard’s nucleus, a mass of dust, rock, and ices about 1 kilometer across, has produced the long tail of ionized gas fluorescing in the sunlight. Likely flares on the comet’s nucleus and buffeting by magnetic fields and the solar wind in recent weeks have resulted in the tail’s irregular pinched and twisted appearance. Still days from its closest approach to the Sun, Comet Leonard’s activity should continue. The comet is south of the Solar System’s ecliptic plane as it sweeps through the southern constellation Microscopium.
What and where are these large ovals? They are rotating storm clouds on Jupiter imaged last month by NASA’s Juno spacecraft. In general, higher clouds are lighter in color, and the lightest clouds visible are the relatively small clouds that dot the lower oval. At 50 kilometers across, however, even these light clouds are not small. They are so high up that they cast shadows on the swirling oval below. The featured image has been processed to enhance color and contrast. Large ovals are usually regions of high pressure that span over 1000 kilometers and can last for years. The largest oval on Jupiter is the Great Red Spot (not pictured), which has lasted for at least hundreds of years. Studying cloud dynamics on Jupiter with Juno images enables a better understanding of dangerous typhoons and hurricanes on Earth.
What’s happened to the Sun? Sometimes it looks like the Sun is being viewed through a giant lens. In the featured video, however, there are actually millions of tiny lenses: ice crystals. Water may freeze in the atmosphere into small, flat, six-sided, ice crystals. As these crystals flutter to the ground, much time is spent with their faces flat and parallel to the ground. An observer may find themselves in the same plane as many of the falling ice crystals near sunrise or sunset. During this alignment, each crystal can act like a miniature lens, refracting sunlight into our view and creating phenomena like parhelia, the technical term for sundogs. The featured video was taken in late 2017 on the side of a ski hill at the Vemdalen Ski Resort in central Sweden. Visible in the center is the most direct image of the Sun, while two bright sundogs glow prominently from both the left and the right. Also visible is the bright 22 degree halo — as well as the rarer and much fainter 46 degree halo — also created by sunlight refracting through atmospheric ice crystals.
Which one of these two streaks is a comet? Although they both have comet-like features, the lower streak is the only real comet. This lower streak shows the coma and tail of Comet Leonard, a city-sized block of rocky ice that is passing through the inner Solar System as it continues its looping orbit around the Sun. Comet Leonard has recently passed its closest to both the Earth and Venus and will round the Sun next week. The comet, still visible to the unaided eye, has developed a long and changing tail in recent weeks. In contrast, the upper streak is the launch plume of the Ariane V rocket that lifted the James Webb Space Telescope (JWST) off the Earth two days ago. The featured single-exposure image was taken from Thailand, and the foreground spire is atop a pagoda in Doi Inthanon National Park. JWST, NASA’s largest and most powerful space telescope so far, will orbit the Sun near the Earth-Sun L2 point and is scheduled to start science observations in the summer of 2022.
There’s a big new telescope in space. This one, the James Webb Space Telescope (JWST), not only has a mirror over five times larger than Hubble‘s in area, but can see better in infrared light. The featured picture shows JWST high above the Earth just after being released by the upper stage of an Ariane V rocket, launched yesterday from French Guiana. Over the next month, JWST will move out near the Sun-Earth L2 point where it will co-orbit the Sun with the Earth. During this time and for the next five months, JWST will unravel its segmented mirror and an array of sophisticated scientific instruments — and test them. If all goes well, JWST will start examining galaxies across the universe and planets orbiting stars across our Milky Way Galaxy in the summer of 2022.
The tail of a comet streams across this three degree wide telescopic field of view captured under dark Namibian skies on December 21. In outburst only a few days ago and just reaching naked eye visibility Comet Leonard (C/2021 A1) is this year’s brightest comet. Binoculars will make the diffuse comet easier to spot though, close to the western horizon after sunset. Details revealed in the sharp image show the comet’s coma with a greenish tinge, and follow the interaction of the comet’s ion tail with magnetic fields in the solar wind. After passing closest to Earth on December 12 and Venus on December 18, Comet Leonard is heading toward perihelion, its closest approach to the Sun on January 3rd. Appearing in late December’s beautiful evening skies after sunset, Comet Leonard has also become known as 2021’s Christmas Comet.
The Crab Nebula is cataloged as M1, the first object on Charles Messier’s famous 18th century list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, debris from the death explosion of a massive star, witnessed by astronomers in the year 1054. This sharp, ground-based telescopic view combines broadband color data with narrowband data that tracks emission from ionized sulfur, hydrogen, and oxygen atoms to explore the tangled filaments within the still expanding cloud. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is visible as a bright spot near the nebula’s center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab’s emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is a mere 6,500 light-years away in the constellation Taurus.