Explanation: On the first planetary defense test mission from planet Earth, the DART spacecraft captured this close-up on 26 September 2022, three seconds before slamming into the surface of asteroid moonlet Dimorphos. The spacecraft's outline with two long solar panels is traced at its projected point of impact between two boulders. The larger boulder is about 6.5 meters across. While the DART (Double Asteroid Redirection Test) spacecraft had a mass of some 570 kilograms, the estimated mass of Dimorphos, the smaller member of a near-Earth binary asteroid system, was about 5 billion kilograms. The direct kinetic impact of the spacecraft measurably altered the speed of Dimorphos by a fraction of a percent, reducing its 12 hour orbital period around its larger companion asteroid 65803 Didymos by about 33 minutes. Beyond successfully demonstrating a technique to change an asteroid's orbit that can prevent future asteroid strikes on planet Earth, the planetary-scale impact experiment has given the 150-meter-sized Dimorphos a comet-like tail of material.

Explanation: Where have all the dim stars gone? From many places on the Earth including major cities, the night sky has been reduced from a fascinating display of thousands of stars to a diffuse glow through which only a few stars are visible. The featured map indicates the relative amount of light pollution that occurs across the Earth. The cause of the pollution is artificial light reflecting off molecules and aerosols in the atmosphere. Parts of the Eastern United States and Western Europe colored red, for example, have an artificial night sky glow over ten times that of the natural sky. In any area marked orange or red, the central band of our Milky Way Galaxy is no longer visible. The International Dark Sky Association suggests common types of fixtures that provide relatively little amounts of light pollution.

Explanation: Is this a spiral galaxy? No. Actually, it is the Large Magellanic Cloud (LMC), the largest satellite galaxy of our own Milky Way Galaxy. The LMC is classified as a dwarf irregular galaxy because of its normally chaotic appearance. In this deep and wide exposure, however, the full extent of the LMC becomes visible. Surprisingly, during longer exposures, the LMC begins to resemble a barred spiral galaxy. The Large Magellanic Cloud lies only about 180,000 light-years distant towards the constellation of the Dolphinfish (Dorado). Spanning about 15,000 light-years, the LMC was the site of SN1987A, the brightest and closest supernova in modern times. Together with the Small Magellanic Cloud (SMC), the LMC can be seen in Earth's southern hemisphere with the unaided eye.

Explanation: It was visible around the world. The sunset conjunction of Jupiter and Venus in 2012 was visible almost no matter where you lived on Earth. Anyone on the planet with a clear western horizon at sunset could see them. Pictured here in 2012, a creative photographer traveled away from the town lights of Szubin, Poland to image a near closest approach of the two planets. The bright planets were then separated only by three degrees and his daughter struck a humorous pose. A faint red sunset still glowed in the background. Jupiter and Venus are together again this month after sunset, passing within a degree of each other about a week ago.

Explanation: What are those two bright spots? Planets. A few days ago, the two brightest planets in the night sky passed within a single degree of each other in what is termed a conjunction. Visible just after sunset in much of the world, the two bright spots were Jupiter (left) and Venus (right). The featured image was taken near closest approach from Cirica, Sicily, Italy. The week before, Venus was rising higher in the sunset sky to meet the dropping Jupiter. Now they have switched places. Of course, Venus remains much closer to both the Sun and the Earth than Jupiter -- the apparent closeness between the planets in the sky of Earth was only angular. You can still see the popular pair for an hour or so after sunset this month although they continue to separate, and Jupiter continues to set earlier each night.

Explanation: Venus and Jupiter may have caught your attention lately. The impending close conjunction of the two brightest planets visible in clear evening skies has been hard to miss. With Jupiter at the top, starting on February 21 and ending on March 2, their close approach is chronicled daily, left to right, in these panels recorded from Dhanbad, India. Near the western horizon, the evening sky colors and exposures used for each panel depend on the local conditions near sunset. On February 22, Jupiter and Venus were joined by the young crescent Moon. The celestial pair appeared to be only the width of a full moon apart by March 2. Of course on that date the two planets were physically separated by over 600 million kilometers in their orbits around the Sun. In the coming days Jupiter will slowly settle into the glare at sunset, but Venus will continue to move farther from the Sun in the western sky to excel in its current role as the brilliant evening star.

Explanation: In 185 AD, Chinese astronomers recorded the appearance of a new star in the Nanmen asterism. That part of the sky is identified with Alpha and Beta Centauri on modern star charts. The new star was visible to the naked-eye for months, and is now thought to be the earliest recorded supernova. This deep telescopic view reveals the wispy outlines of emission nebula RCW 86, just visible against the starry background, understood to be the remnant of that stellar explosion. Captured by the wide-field Dark Energy Camera operating at Cerro Tololo Inter-American Observatory in Chile, the image traces the full extent of a ragged shell of gas ionized by the still expanding shock wave. Space-based images indicate an abundance of the element iron in RCW 86 and the absence of a neutron star or pulsar within the remnant, suggesting that the original supernova was Type Ia. Unlike the core collapse supernova explosion of a massive star, a Type Ia supernova is a thermonuclear detonation on a white dwarf star that accretes material from a companion in a binary star system. Near the plane of our Milky Way galaxy and larger than the full moon on the sky this supernova remnant is too faint to be seen by eye though. RCW 86 is some 8,000 light-years distant and around 100 light-years across.

Explanation: Spiral galaxy NGC 3169 looks to be unraveling like a ball of cosmic yarn. It lies some 70 million light-years away, south of bright star Regulus toward the faint constellation Sextans. Wound up spiral arms are pulled out into sweeping tidal tails as NGC 3169 (left) and neighboring NGC 3166 interact gravitationally. Eventually the galaxies will merge into one, a common fate even for bright galaxies in the local universe. Drawn out stellar arcs and plumes are clear indications of the ongoing gravitational interactions across the deep and colorful galaxy group photo. The telescopic frame spans about 20 arc minutes or about 400,000 light-years at the group's estimated distance, and includes smaller, bluish NGC 3165 at the right. NGC 3169 is also known to shine across the spectrum from radio to X-rays, harboring an active galactic nucleus that is the site of a supermassive black hole

Explanation: Why is a thin crescent moon never seen far from a horizon? Because the only geometry that gives a thin crescent lunar phase occurs when the Moon appears close to the Sun in the sky. The crescent is not caused by the shadow of the Earth, but by seeing only a small part of the Moon directly illuminated by the Sun. Moreover, the thickest part of the crescent always occurs in the direction of the Sun. In the evening, a thin crescent Moon will set shortly after the Sun and not be seen for the rest of the night. Alternatively, in the morning, a crescent Moon will rise shortly before the Sun after not being seen for most of the night. Pictured two weeks ago, a crescent moon was captured near the horizon, just before sunrise, far behind remnants of the ancient Temple of Poseidon in Greece.

Explanation: What's causing that unusual ray of light extending from the horizon? Dust orbiting the Sun. At certain times of the year, a band of sun-reflecting dust from the inner Solar System appears prominently after sunset or before sunrise and is called zodiacal light. The dust was emitted mostly from faint Jupiter-family comets and slowly spirals into the Sun. The featured HDR image, acquired in mid-February from the Sierra Nevada National Park in Spain, captures the glowing band of zodiacal light going right in front of the bright evening planets Jupiter (upper) and Venus (lower). Emitted from well behind the zodiacal light is a dark night sky that prominently includes the Pleiades star cluster. Jupiter and Venus are slowly switching places in the evening sky, and just in the next few days nearing their closest angular approach.

Explanation: Planetary nebula Jones-Emberson 1 is the death shroud of a dying Sun-like star. It lies some 1,600 light-years from Earth toward the sharp-eyed constellation Lynx. About 4 light-years across, the expanding remnant of the dying star's atmosphere was shrugged off into interstellar space, as the star's central supply of hydrogen and then helium for fusion was finally depleted after billions of years. Visible near the center of the planetary nebula is what remains of the stellar core, a blue-hot white dwarf star. Also known as PK 164 +31.1, the nebula is faint and very difficult to glimpse at a telescope's eyepiece. But this deep broadband image combining 22 hours of exposure time does show it off in exceptional detail. Stars within our own Milky Way galaxy as well as background galaxies across the universe are scattered through the clear field of view. Ephemeral on the cosmic stage, Jones-Emberson 1 will fade away over the next few thousand years. Its hot, central white dwarf star will take billions of years to cool.

Explanation: Our Sun is becoming a busy place. Only two years ago, the Sun was emerging from a solar minimum so quiet that months would go by without even a single sunspot. In contrast, already this year and well ahead of schedule, our Sun is unusually active, already nearing solar activity levels seen a decade ago during the last solar maximum. Our increasingly active Sun was captured two weeks ago sporting numerous interesting features. The image was recorded in a single color of light called Hydrogen Alpha, color-inverted, and false colored. Spicules carpet much of the Sun's face. The brightening towards the Sun's edges is caused by increased absorption of relatively cool solar gas and called limb darkening. Just outside the Sun's disk, several scintillating prominences protrude, while prominences on the Sun's face are known as filaments and show as light streaks. Magnetically tangled active regions are both dark and light and contain cool sunspots. As our Sun's magnetic field winds toward solar maximum over the next few years, whether the Sun's high activity will continue to increase is unknown.

Explanation: There is nothing like this ball of stars in our Milky Way Galaxy. This is surprising because, at first glance, this featured image by the Hubble Space Telescope suggests that star cluster NGC 1850's size and shape are reminiscent of the many ancient globular star clusters which roam our own Milky Way Galaxy's halo. But NGC 1850's stars are all too young, making it a type of star cluster with no known counterpart in the Milky Way. Moreover, NGC 1850 is also a double star cluster, with a second, compact cluster of stars visible here just to the right of the large cluster's center. Stars in the large cluster are estimated to be 50 million years young, while stars in the compact cluster are younger still, with an age of about 4 million years. A mere 168,000 light-years distant, NGC 1850 is located near the outskirts of the Large Magellanic Cloud galaxy. The glowing gas filaments across the image left, like supernova remnants in our own galaxy, testify to violent stellar explosions and indicate that short-lived massive stars have recently been present in the region.

Explanation: A mere 56 million light-years distant toward the southern constellation Fornax, NGC 1365 is an enormous barred spiral galaxy about 200,000 light-years in diameter. That's twice the size of our own barred spiral Milky Way. This sharp image from the James Webb Space Telescope's Mid-Infrared Instrument (MIRI) reveals stunning details of this magnificent spiral in infrared light. Webb's field of view stretches about 60,000 light-years across NGC 1365, exploring the galaxy's core and bright newborn star clusters. The intricate network of dusty filaments and bubbles is created by young stars along spiral arms winding from the galaxy's central bar. Astronomers suspect the gravity field of NGC 1365's bar plays a crucial role in the galaxy's evolution, funneling gas and dust into a star-forming maelstrom and ultimately feeding material into the active galaxy's central, supermassive black hole.

Explanation: While scanning the skies for near earth objects Hungarian astronomer Krisztián Sárneczky first imaged the meter-sized space rock now cataloged as 2023 CX1 on 12 February 2023 at 20:18:07 UTC. That was about 7 hours before it impacted planet Earth's atmosphere. Its predicted trajectory created a rare opportunity for meteor observers and a last minute plan resulted in this spectacular image of the fireball, captured from the Netherlands as 2023 CX1 vaporized and broke up over northern France. Remarkably it was Sárneczky's second discovery of an impacting asteroid, while 2023 CX1 is only the seventh asteroid to be detected before being successfully predicted to impact Earth. It has recently become the third such object from which meteorites have been recovered. This fireball was witnessed almost 10 years to the day following the infamous Chelyabinsk Meteor flash.

Explanation: This unusual sky was both familiar and unfamiliar. The photographer's mission was to capture the arch of the familiar central band of our Milky Way Galaxy over a picturesque medieval manor. The surprise was that on this January evening, the foreground sky was found glowing in a beautiful but unfamiliar manner. The striped bands are called airglow and they result from air high in Earth's atmosphere being excited by the Sun's light and emitting a faint light of its own. The bands cross the entire sky -- their curved appearance is due to the extremely wide angle of the camera lens. In the foreground lies Château de Losse in southwest France. Other familiar sky delights dot the distant background including the bright white star Sirius, the orange planet Mars, the blue Pleiades star cluster, the red California Nebula, and, on the far right, the extended Andromeda Galaxy. The initial mission was also successful: across the top of the frame is the arching band of our Milky Way.

Explanation: When do cloud bottoms appear like bubbles? Normally, cloud bottoms are flat. This is because moist warm air that rises and cools will condense into water droplets at a specific temperature, which usually corresponds to a very specific height. As water droplets grow, an opaque cloud forms. Under some conditions, however, cloud pockets can develop that contain large droplets of water or ice that fall into clear air as they evaporate. Such pockets may occur in turbulent air near a thunderstorm. Resulting mammatus clouds can appear especially dramatic if sunlit from the side. The mammatus clouds pictured here were photographed over Hastings, Nebraska during 2004 June.

Explanation: Fading as it races across planet Earth's northern skies comet C/2022 E3 (ZTF) shares this telescopic frame with comet C/2022 U2 (ATLAS). Captured on the night of February 6 from a garden observatory in Germany's Bavarian Forest, the starry field of view toward the constellation Auriga spans about 2.5 degrees. Discovered by sky survey projects in 2022 (the Zwicky Transient Facility and the Asteroid Terrestrial-impact Last Alert System) these long-period comets are outbound, reaching perihelion just last month. The much fainter comet ATLAS made its closest approach to our fair planet on January 29 at a distance of about 4.6 light-minutes, compared to a mere 2.4 light-minutes for comet ZTF on February 2. This comet ATLAS lacks the well-developed tails of the formerly naked-eye comet ZTF. But both comets sport greenish tinted comas, emission from diatomic carbon molecules fluorescing in sunlight. Continuing its dash across planet Earth's sky, the good-binocular comet ZTF will appear close to bright planet Mars tonight.

Explanation: Vivid and lustrous, wafting iridescent waves of color wash across this skyscape from Kilpisjärvi, Finland. Known as nacreous clouds or mother-of-pearl clouds, they are rare. But their unforgettable appearance was captured looking south at 69 degrees north latitude at sunset on January 24. 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 even after sunset and just before the dawn.

Explanation: Imagine traveling to a star about 100 times as massive as our Sun, a million times more luminous, and with 30 times the surface temperature. Such stars exist, and some are known as Wolf Rayet (WR) stars, named after French astronomers Charles Wolf and Georges Rayet. The central star in this image is WR 40 which is located toward the constellation of Carina. Stars like WR 40 live fast and die young in comparison with the Sun. They quickly exhaust their core hydrogen supply, move on to fusing heavier core elements, and expand while ejecting their outer layers via high stellar winds. In this case, the central star WR 40 ejects the atmosphere at a speed of nearly 100 kilometers per second, and these outer layers have become the expanding oval-shaped nebula RCW 58.

Explanation: Can you still see the comet? Yes. Even as C/2022 E3 (ZTF) fades, there is still time to see it if you know where and when to look. Geometrically, Comet ZTF has passed its closest to both the Sun and the Earth and is now headed back to the outer Solar System. Its orbit around the Sun has it gliding across the northern sky all month, after passing near Polaris and both the Big and Little Dippers last month. Pictured, Comet ZTF was photographed between the two dippers in late January while sporting an ion tail that extended over 10 degrees. Now below naked-eye visibility, Comet ZTF can be found with binoculars or a small telescope and a good sky map. A good time to see the comet over the next week is after the Sun sets -- but before the Moon rises. The comet will move nearly in front of Mars in a few day

Explanation: The 1970s are sometimes ignored by astronomers, like this beautiful grouping of reflection nebulae in Orion - NGC 1977, NGC 1975, and NGC 1973 - usually overlooked in favor of the substantial glow from the nearby stellar nursery better known as the Orion Nebula. Found along Orion's sword just north of the bright Orion Nebula complex, these reflection nebulae are also associated with Orion's giant molecular cloud about 1,500 light-years away, but are dominated by the characteristic blue color of interstellar dust reflecting light from hot young stars. In this sharp color image a portion of the Orion Nebula appears along the bottom border with the cluster of reflection nebulae at picture center. NGC 1977 stretches across the field just below center, separated from NGC 1973 (above right) and NGC 1975 (above left) by dark regions laced with faint red emission from hydrogen atoms. Taken together, the dark regions suggest the region's popular moniker, the Running Man Nebula. At the estimated distance of Orion's dusty molecular cloud this running man would be about 15 light-years across.

Explanation: Comet ZTF has a distinctive shape. The now bright comet visiting the inner Solar System has been showing not only a common dust tail, ion tail, and green gas coma, but also an uncommonly distinctive antitail. The antitail does not actually lead the comet -- it is just that the head of the comet is seen superposed on part of the fanned-out and trailing dust tail. The giant dirty snowball that is Comet C/2022 E3 (ZTF) has now passed its closest to the Sun and tomorrow will pass its closest to the Earth. The main panel of the featured triple image shows how Comet ZTF looked last week to the unaided eye under a dark and clear sky over Cáceres, Spain. The top inset image shows how the comet looked through binoculars, while the lower inset shows how the comet looked through a small telescope. The comet is now visible all night long from northern latitudes but will surely fade from easy observation during the next few weeks.

Explanation: To some, the dark shape looks like a mythical boogeyman. Scientifically, Lynds' Dark Nebula (LDN) 1622 appears against a faint background of glowing hydrogen gas only visible in long telescopic exposures of the region. In contrast, the brighter reflection nebula vdB 62 is more easily seen just above and to the right of center in the featured image. 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. With swept-back outlines, the obscuring dust of LDN 1622 is thought to lie at a similar distance, perhaps 1,500 light-years away. At that distance, this 2-degree wide field of view would span about 60 light-years. Young stars do lie hidden within the dark expanse and have been revealed in Spitzer Space Telescope infrared images

Explanation: The two dominant galaxies near center are far far away, 12 million light-years distant toward the northern constellation of the Great Bear. On the right, with grand spiral arms and bright yellow core is spiral galaxy M81. Also known as Bode's galaxy, M81 spans some 100,000 light-years. On the left is cigar-shaped irregular galaxy M82. The pair have been locked in gravitational combat for a billion years. Gravity from each galaxy has profoundly affected the other during a series of cosmic close encounters. Their last go-round lasted about 100 million years and likely raised density waves rippling around M81, resulting in the richness of M81's spiral arms. M82 was left with violent star forming regions and colliding gas clouds so energetic that the galaxy glows in X-rays. In the next few billion years, their continuing gravitational encounters will result in a merger, and a single galaxy will remain. This extragalactic scenario also includes other members of the interacting M81 galaxy group with NGC 3077 below and right of the large spiral, and NGC 2976 at upper right in the frame. Captured under dark night skies in the Austrian Alps, the foreground of the wide-field image is filled with integrated flux nebulae. Those faint, dusty interstellar clouds reflect starlight above the plane of our own Milky Way galaxy.

Explanation: A broad expanse of glowing gas and dust presents a bird-like visage to astronomers from planet Earth, suggesting its popular moniker - The Seagull Nebula. Using narrowband image data, this 3-panel mosaic of the cosmic bird covers a 2.5 degree swath across the plane of the Milky Way, near the direction of Sirius, alpha star of the constellation Canis Major. Likely part of a larger shell structure swept up by successive supernova explosions, the broad Seagull Nebula is cataloged as Sh2-296 and IC 2177. The prominent bluish arc below and right of center is a bow shock from runaway star FN Canis Majoris. This complex of gas and dust clouds with other stars of the Canis Majoris OB1 association spans over 200 light-years at the Seagull Nebula's estimated 3,800 light-year distance

Explanation: Gravitational lensing by the galaxy cluster MACS0647 -- in which the massive foreground cluster distorts and lenses the light emitted by distant background galaxies along the line of sight — is on vivid display here in this recent multi-color infrared image from the James Webb Space Telescope (JWST). In particular, the background source MACS0647-JD is seen to be lensed three times by the cluster. When first discovered with the Hubble Space Telescope, MACS0647-JD was observed as an amorphous blob. With Webb though, this single source is revealed to be a pair or small group of galaxies. The colors of the MACS0647-JD objects are different as well -- indicating differences potentially in the age or dust content of these galaxies. These new images provide rare examples of galaxies in an era only a few 100 million years after the Big Bang.

Explanation: Why are there oxygen-emitting arcs near the direction of the Andromeda galaxy? No one is sure. The gas arcs, shown in blue, were discovered and first confirmed by amateur astronomers just last year. The two main origin hypotheses for the arcs are that they really are close to Andromeda (M31), or that they are just coincidentally placed gas filaments in our Milky Way galaxy. Adding to the mystery is that arcs were not seen in previous deep images of M31 taken primarily in light emitted by hydrogen, and that other, more distant galaxies have not been generally noted as showing similar oxygen-emitting structures. Dedicated amateurs using commercial telescopes made this discovery because, in part, professional telescopes usually investigate angularly small patches of the night sky, whereas these arcs span several times the angular size of the full moon. Future observations -- both in light emitted by oxygen and by other elements -- are sure to follow.

Explanation: Our Moon doesn't really look like this. Earth's Moon, Luna, doesn't naturally show this rich texture, and its colors are more subtle. But this digital creation is based on reality. The featured image is a composite of multiple images and enhanced to bring up real surface features. The enhancements, for example, show more clearly craters that illustrate the tremendous bombardment our Moon has been through during its 4.6-billion-year history. The dark areas, called maria, have fewer craters and were once seas of molten lava. Additionally, the image colors, although based on the moon's real composition, are changed and exaggerated. Here, a blue hue indicates a region that is iron rich, while orange indicates a slight excess of aluminum. Although the Moon has shown the same side to the Earth for billions of years, modern technology is allowing humanity to learn much more about it -- and how it affects the Earth.