M1: The Crab Nebula from Hubble
This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The featured image, taken by the Hubble Space Telescope, is presented in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second. Discovery + Outreach: Graduate student research position open for APOD
Perihelion Sun 2023
Perihelion for 2023, Earth's closest approach to the Sun, was on January 4 at 16:17 UTC. That was less than 24 hours after this sharp image of the Sun's disk was recorded with telescope and H-alpha filter from Sidney, Australia, planet Earth. An H-alpha filter transmits a characteristic red light from hydrogen atoms. In views of the Sun it emphasizes the Sun's chromosphere, a region just above the solar photosphere or normally visible solar surface. In this H-alpha image of the increasingly active Sun planet-sized sunspot regions are dominated by bright splotches called plages. Dark filaments of plasma snaking across the solar disk transition to bright prominences when seen above the solar limb.
Young Star Cluster NGC 346
The most massive young star cluster in the Small Magellanic Cloud is NGC 346, embedded in our small satellite galaxy's largest star forming region some 210,000 light-years distant. Of course the massive stars of NGC 346 are short lived, but very energetic. Their winds and radiation sculpt the edges of the region's dusty molecular cloud triggering star-formation within. The star forming region also appears to contain a large population of infant stars. A mere 3 to 5 million years old and not yet burning hydrogen in their cores, the infant stars are strewn about the embedded star cluster. This spectacular infrared view of NGC 346 is from the James Webb Space Telescope's NIRcam. Emission from atomic hydrogen ionized by the massive stars' energetic radiation as well as and molecular hydrogen and dust in the star-forming molecular cloud is detailed in pink and orange hues. Webb's sharp image of the young star-forming region spans 240 light-years at the distance of the Small Magellanic Cloud.
Stardust in Perseus
This cosmic expanse of dust, gas, and stars covers some 6 degrees on the sky in the heroic constellation Perseus. At upper left in the gorgeous skyscape is the intriguing young star cluster IC 348 and neighboring Flying Ghost Nebula with clouds of obscuring interstellar dust cataloged as Barnard 3 and 4. At right, another active star forming region NGC 1333 is connected by dark and dusty tendrils on the outskirts of the giant Perseus Molecular Cloud, about 850 light-years away. Other dusty nebulae are scattered around the field of view, along with the faint reddish glow of hydrogen gas. In fact, the cosmic dust tends to hide the newly formed stars and young stellar objects or protostars from prying optical telescopes. Collapsing due to self-gravity, the protostars form from the dense cores embedded in the molecular cloud. At the molecular cloud's estimated distance, this field of view would span over 90 light-years.
Spiral Aurora over Iceland
The scene may look like a fantasy, but it's really Iceland. The rock arch is named Gatklettur and located on the island's northwest coast. Some of the larger rocks in the foreground span a meter across. The fog over the rocks is really moving waves averaged over long exposures. The featured image is a composite of several foreground and background shots taken with the same camera and from the same location on the same night last November. The location was picked for its picturesque foreground, but the timing was planned for its colorful background: aurora. The spiral aurora, far behind the arch, was one of the brightest seen in the astrophotographer's life. The coiled pattern was fleeting, though, as auroral patterns waved and danced for hours during the cold night. Far in the background were the unchanging stars, with Earth's rotation causing them to appear to slowly circle the sky's northernmost point near Polaris. Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)
NGC 2264: The Cone Nebula
Stars are forming in the gigantic dust pillar called the Cone Nebula. Cones, pillars, and majestic flowing shapes abound in stellar nurseries where clouds of gas and dust are sculpted by energetic winds from newborn stars. The Cone Nebula, a well-known example, lies within the bright galactic star-forming region NGC 2264. The featured image of the Cone was captured recently combining 24-hours of exposure with a half-meter telescope at the El Sauce Observatory in Chile. Located about 2,500 light-years away toward the constellation of the Unicorn (Monoceros), the Cone Nebula's conical pillar extends about 7 light-years. The massive star NGC 2264 IRS, is the likely source of the wind sculpting the Cone Nebula and lies off the top of the image. The Cone Nebula's reddish veil is produced by glowing hydrogen gas. Discovery + Outreach: Graduate student research position open for APOD
Tails of Comet ZTF
Comet ZTF may become visible to the unaided eye. Discovered early last year, this massive snowball has been brightening as it approaches the Sun and the Earth. C/2022 E3 (ZTF) will be closest to the Sun later this week, at which time it may become visible even without binoculars to northern observers with a clear and dark sky. As they near the Sun, comet brightnesses are notoriously hard to predict, though. In the featured image taken last week in front of a picturesque star field, three blue ion tails extend to the upper right, likely the result of a variable solar wind on ions ejected by the icy comet nucleus. The comet's white dust tail is visible to the upper left and much shorter. The green glow is the comet's coma, caused by glowing carbon gas. Comet ZTF is expected to pass nearest the Earth in early February, after which it should dim dramatically. Discovery + Outreach: Graduate student research position open for APOD
Where Your Elements Came From
The hydrogen in your body, present in every molecule of water, came from the Big Bang. There are no other appreciable sources of hydrogen in the universe. The carbon in your body was made by nuclear fusion in the interior of stars, as was the oxygen. Much of the iron in your body was made during supernovas of stars that occurred long ago and far away. The gold in your jewelry was likely made from neutron stars during collisions that may have been visible as short-duration gamma-ray bursts or gravitational wave events. Elements like phosphorus and copper are present in our bodies in only small amounts but are essential to the functioning of all known life. The featured periodic table is color coded to indicate humanity's best guess as to the nuclear origin of all known elements. The sites of nuclear creation of some elements, such as copper, are not really well known and are continuing topics of observational and computational research. Discovery + Outreach: Graduate student research position open for APOD
Space Stations in Low Earth Orbit
On January 3, two space stations already illuminated by sunlight in low Earth orbit crossed this dark predawn sky. Moving west to east (left to right) across the composited timelapse image China's Tiangong Space Station traced the upper trail captured more than an hour before the local sunrise. Seen against a starry background Tiangong passes just below the inverted Big Dipper asterism of Ursa Major near the peak of its bright arc, and above north pole star Polaris. But less than five minutes before, the International Space Station had traced its own sunlit streak across the dark sky. Its trail begins just above the W-shape outlined by the bright stars of Cassiopeia near the northern horizon. The dramatic foreground spans an abandoned mine at Achada do Gamo in southeastern Portugal.
Moon O'Clock 2022
The first Full Moon of 2023 is in the sky tonight opposite the Sun at 23:08 UTC. Big and beautiful, the Moon at its brightest phase should be easy to spot. Still, for quick reference images captured near the times of all the full moons of 2022 are aranged in this dedicated astro-imaging project from Sri Lanka, planet Earth. The day, month, and a traditional popular name for 2022's twelve full moons are given in the chart. The apparent size of each full moon depends on how close the full lunar phase is to perigee or apogee, the closest or farthest point in the Moon's elliptical orbit. Like the 2022 Wolf Moon at the 1 o'clock position, tonight's Full Moon occurs within a about two days of apogee. But unlike in 2022, the year 2023 will have 13 full moons that won't all fit nicely on the twelve hour clock.
Messier 45: The Daughters of Atlas and Pleione
Hurtling through a cosmic dust cloud a mere 400 light-years away, the lovely Pleiades or Seven Sisters open star cluster is well-known for its striking blue reflection nebulae. It lies in the night sky toward the constellation Taurus and the Orion Arm of our Milky Way galaxy. The sister stars are not related to the dusty cloud though. They just happen to be passing through the same region of space. Known since antiquity as a compact grouping of stars, Galileo first sketched the star cluster viewed through his telescope with stars too faint to be seen by eye. Charles Messier recorded the position of the cluster as the 45th entry in his famous catalog of things which are not comets. In Greek myth, the Pleiades were seven daughters of the astronomical titan Atlas and sea-nymph Pleione. Their parents names are included in the cluster's nine brightest stars. This well-processed, color-calibrated telescopic image features pin-point stars and detailed filaments of interstellar dust captured in over 9 hours of exposure. It spans more than 20 light-years across the Pleiades star cluster.
CG4: The Globule and the Galaxy
Can a gas cloud eat a galaxy? It's not even close. The "claw" of this odd looking "creature" in the featured photo is a gas cloud known as a cometary globule. This globule, however, has ruptured. Cometary globules are typically characterized by dusty heads and elongated tails. These features cause cometary globules to have visual similarities to comets, but in reality they are very much different. Globules are frequently the birthplaces of stars, and many show very young stars in their heads. The reason for the rupture in the head of this object is not yet known. The galaxy to the left of the globule is huge, very far in the distance, and only placed near CG4 by chance superposition. Discovery + Outreach: Graduate student research position open for APOD
Kemble’s Cascade of Stars
This line of stars is real. A little too faint to see with the unaided eye, Kemble’s Cascade of stars inspires awe when seen with binoculars. Like the Big Dipper though, Kemble’s Cascade is an asterism, not a constellation. The asterism is visible in the northern sky toward the long-necked constellation of the Giraffe (Camelopardalis). This string of about 20 unrelated stars, each of similar brightness, spans over five times the angular width of the full moon. Stretching diagonally from the upper left to the lower right, Kemble's Cascade was popularized last century by astronomy enthusiast Lucian Kemble. The bright object near the top left of the image is the relatively compact Jolly Roger open cluster of stars, officially designated as NGC 1502.
After Sunset Planet Parade
Look up tonight and see a whole bunch of planets. Just after sunset, looking west, planets Venus, Saturn, Jupiter and Mars will all be simultaneously visible. Listed west to east, this planetary lineup will have Venus nearest the horizon, but setting shortly after the Sun. It doesn't matter where on Earth you live because this early evening planet parade will be visible through clear skies all around the globe. Taken late last month, the featured image captured all of these planets and more: the Moon and planet Mercury were also simultaneously visible. Below visibility were the planets Neptune and Uranus, making this a nearly all-planet panorama. In the foreground are hills around the small village of Gökçeören, Kaş, Turkey, near the Mediterranean coast. Bright stars Altair, Fomalhaut, and Aldebaran are also prominent, as well as the Pleiades star cluster. Venus will rise higher in the sky at sunset as January continues, but Saturn will descend.
The Largest Rock in our Solar System
There, that dot on the right, that's the largest rock known in our Solar System. It is larger than every known asteroid, moon, and comet nucleus. It is larger than any other local rocky planet. This rock is so large its gravity makes it into a large ball that holds heavy gases near its surface. (It used to be the largest known rock of any type until the recent discoveries of large dense planets orbiting other stars.) The Voyager 1 spacecraft took the featured picture -- famously called Pale Blue Dot -- of this giant space rock in 1990 from the outer Solar System. Today, this rock starts another orbit around its parent star, for roughly the 5 billionth time, spinning over 350 times during each trip. Happy Gregorian Calendar New Year to all inhabitants of this rock we call Earth.
