Magazine Posts

NASA Astronomy Picture of the Day:

Vivid and lustrous, wafting iridescent waves of color filled this mountain and skyscape near Tanndalen, Sweden on January 3. Known as nacreous clouds or mother-of-pearl clouds, they are rare. This northern winter season they have been making unforgettable appearances at high latitudes, though. A type of polar stratospheric cloud, they form when unusually cold temperatures in the usually cloudless lower stratosphere form ice crystals. Still sunlit at altitudes of around 15 to 25 kilometers the clouds can diffract sunlight after sunset and before the dawn.

Photo by Clear Skies

NASA Astronomy Picture of the Day:

Perihelion for 2020, the point in Earth's elliptical orbit when it is closest to the Sun, occurred on January 5th. The distance from the Sun doesn't determine the seasons, though. Those are governed by the tilt of Earth's axis of rotation, so January is still winter in the north and summer in southern hemisphere. But it does mean that on January 5 the Sun was at its largest apparent size. This composite neatly compares two pictures of the Sun, both taken from planet Earth with the same telescope and camera. The left half was captured on the date of the 2020 perihelion. The right was recorded only a week before the July 4 date of the 2019 aphelion, the farthest point in Earth's orbit. Otherwise difficult to notice, the change in the Sun's apparent diameter between perihelion and aphelion amounts to a little over 3 percent. The 2020 perihelion and the preceding 2019 aphelion correspond to the closest and farthest perihelion and aphelion of the 21st century.

Photo by Ian Griffin

NASA Astronomy Picture of the Day:

Large galaxies grow by eating small ones. Even our own galaxy engages in a sort of galactic cannibalism, absorbing small galaxies that are too close and are captured by the Milky Way's gravity. In fact, the practice is common in the universe and illustrated by this striking pair of interacting galaxies from the banks of the southern constellation Eridanus, The River. Located over 50 million light years away, the large, distorted spiral NGC 1532 is seen locked in a gravitational struggle with dwarf galaxy NGC 1531 (right of center), a struggle the smaller galaxy will eventually lose. Seen edge-on, spiral NGC 1532 spans about 100,000 light-years. Nicely detailed in this sharp image, the NGC 1532/1531 pair is thought to be similar to the well-studied system of face-on spiral and small companion known as M51.

Photo by Star Shadows Remote Observatory

NASA Astronomy Picture of the Day:

Rippling dust and gas lanes give the Flaming Star Nebula its name. The orange and purple colors of the nebula are present in different regions and are created by different processes. The bright star AE Aurigae, visible toward the image left, is so hot it is blue, emitting light so energetic it knocks electrons away from surrounding gas. When a proton recaptures an electron, red light is frequently emitted (depicted here in orange). The purple region's color is a mix of this red light and blue light emitted by AE Aurigae but reflected to us by surrounding dust. The two regions are referred to as emission nebula and reflection nebula, respectively. Pictured here in the Hubble color palette, the Flaming Star Nebula, officially known as IC 405, lies about 1500 light years distant, spans about 5 light years, and is visible with a small telescope toward the constellation of the Charioteer (Auriga).

Photo by Eric Coles

NASA Astronomy Picture of the Day:

Some cloud patterns on Jupiter are quite complex. The featured tumultuous clouds were captured in May by NASA's robotic Juno spacecraft currently orbiting our Solar System's largest planet. The image was taken when Juno was only about 15,000 kilometers over Jupiter's cloud tops, so close that less than half of the giant planet is visible. The rough white clouds on the far right are high altitude clouds known as pop-up clouds. Juno's mission, now extended into 2021, is to study Jupiter in new ways. Among many other things, Juno has been measuring Jupiter's gravitational field, finding surprising evidence that Jupiter may be mostly a liquid.

NASA Astronomy Picture of the Day:

On some nights, the sky is the best show in town. On this night, the sky was not only the best show in town, but a composite image of the sky won an international competition for landscape astrophotography. The featured winning image was taken in 2011 over Jökulsárlón, the largest glacial lake in Iceland. The photographer combined six exposures to capture not only two green auroral rings, but their reflections off the serene lake. Visible in the distant background sky is the band of our Milky Way Galaxy and the Andromeda galaxy. A powerful coronal mass ejection from the Sun caused auroras to be seen as far south as Wisconsin, USA. As the Sun progresses away from its current low in surface activity toward a solar maximum a few years away, many more spectacular images of aurora are expected.

Image Credit: Stephane Vetter (Nuits sacrees)

NASA Astronomy Picture of the Day:

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.

NASA Astronomy Picture of the Day:

Named for a forgotten constellation, the Quadrantid Meteor Shower is an annual event for planet Earth's northern hemisphere skygazers The shower's radiant on the sky lies within the old, astronomically obsolete constellation Quadrans Muralis. That location is not far from the Big Dipper, at the boundaries of the modern constellations Bootes and Draco. With the radiant out of the frame at the upper right, Quadrantid meteors streak through this night skyscape composed of digital frames recorded in the hours around the shower's peak on January 4, 2013. The last quarter moon illuminates rugged terrain and a section of the Great Wall in Hebei Province, China. A likely source of the dust stream that produces Quadrantid meteors was identified in 2003 as an asteroid. As usual, in 2020 the shower is expected to peak briefly on the night of January 3/4. Meteor fans in North America can anticpate a good show to celebrate the new year in moonless skies before tomorrow's dawn. Free Presentation: APOD Editor to show best astronomy images of 2019 -- and the decade -->tonight in NYC.

Photo by Cheng Luo

NASA Astronomy Picture of the Day:

Begirt with many a blazing star, Orion the Hunter is one of the most recognizable constellations. In this night skyscape the Hunter's stars rise in the northern hemisphere's winter sky on December 30, 2019, tangled in bare trees near Newnan, Georgia, USA. Red super giant star Betelgeuse stands out in yellowish hues at Orion's shoulder left of center, but it no longer so strongly rivals the blue supergiant star Rigel at the Hunter's foot. In fact, skygazers around planet Earth can see a strikingly fainter Betelgeuse now, its brightness fading by more than half in the final months of 2019. Betelgeuse has long been known to be a variable star, changing its brightness in multiple cycles with approximate short and long term periods of hundreds of days to many years. The star is now close to its faintest since photometric measurements in 1926/27, likely due in part to a near coincidence in the minimum of short and long term cycles. Betelgeuse is also recognized as a nearby red supergiant star that will end its life in a core collapse supernova explosion sometime in the next 1,000 years, though that cosmic cataclysm will take place a safe 700 light-years or so from our fair planet.

Photo by Jimmy Westlake

NASA Astronomy Picture of the Day:

Why is Betelgeuse fading? No one knows. Betelgeuse, one of the brightest and most recognized stars in the night sky, is only half as bright as it used to be only five months ago. Such variability is likely just normal behavior for this famously variable supergiant, but the recent dimming has rekindled discussion on how long it may be before Betelgeuse does go supernova. Known for its red color, Betelgeuse is one of the few stars to be resolved by modern telescopes, although only barely. The featured artist's illustration imagines how Betelgeuse might look up close. Betelgeuse is thought to have a complex and tumultuous surface that frequently throws impressive flares. Were it to replace the Sun (not recommended), its surface would extend out near the orbit of Jupiter, while gas plumes would bubble out past Neptune. Since Betelgeuse is about 700 light years away, its eventual supernova will not endanger life on Earth even though its brightness may rival that of a full Moon. Astronomers -- both amateur and professional -- will surely continue to monitor Betelgeuse as this new decade unfolds. Free Presentation: APOD Editor to show best astronomy images of 2019 -- and the decade -- in NYC on January 3

NASA Astronomy Picture of the Day:

The small, northern constellation Triangulum harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the Triangulum Galaxy. M33 is over 50,000 light-years in diameter, third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the Andromeda Galaxy and astronomers in these two galaxies would likely have spectacular views of each other's grand spiral star systems. As for the view from planet Earth, this sharp image shows off M33's blue star clusters and pinkish star forming regions along the galaxy's loosely wound spiral arms. In fact, the cavernous NGC 604 is the brightest star forming region, seen here at about the 7 o'clock position from the galaxy center. Like M31, M33's population of well-measured variable stars have helped make this nearby spiral a cosmic yardstick for establishing the distance scale of the Universe.

Photo by Rui Liao

NASA Astronomy Picture of the Day:

The beautiful Trifid Nebula, also known as Messier 20, is easy to find with a small telescope in the nebula rich constellation Sagittarius. About 5,000 light-years away, the colorful study in cosmic contrasts shares this well-composed, nearly 1 degree wide field with open star cluster Messier 21 (top left). Trisected by dust lanes the Trifid itself is about 40 light-years across and a mere 300,000 years old. That makes it one of the youngest star forming regions in our sky, with newborn and embryonic stars embedded in its natal dust and gas clouds. Estimates of the distance to open star cluster M21 are similar to M20's, but though they share this gorgeous telescopic skyscape there is no apparent connection between the two. In fact, M21's stars are much older, about 8 million years old.

Photo by Stanislav Volskiy