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Explanation: Beautiful and bright spiral galaxy M83 lies a some twelve million light-years away, near the southeastern tip of the very long constellation Hydra. Prominent spiral arms traced by dark dust lanes and blue star clusters lend this galaxy its popular name, The Southern Pinwheel. Still, reddish star forming regions that dot this cosmic pinwheel's spiral arms have suggested another nickname, the Thousand-Ruby Galaxy. A mere 40,000 light-years across, smaller than the Milky Way, M83 is a member of a group of galaxies that includes active galaxy Centaurus A. In fact, the core of M83 itself is bright at x-ray...

Explanation: Does the Moon ever engulf Mars? Yes, but only in the sense that it moves in front, which happens on rare occasions. This happened just yesterday, though, as seen from some locations in North America and western Africa. This occultation was notable not only because the Moon was a fully lit Wolf Moon, but because Mars was near its largest and brightest, moving to opposition -- the closest to the Earth in its orbit -- only tomorrow. The engulfing, more formally called an occultation, typically lasting about an hour. The featured image was taken from near Chicago, Illinois, USA...

Explanation: Why is Polaris called the North Star? First, Polaris is the nearest bright star toward the north spin axis of the Earth. Therefore, as the Earth turns, stars appear to revolve around Polaris, but Polaris itself always stays in the same northerly direction -- making it the North Star. Since no bright star is near the south spin axis of the Earth, there is currently no bright South Star. Thousands of years ago, Earth's spin axis pointed in a slightly different direction so that Vega was the North Star. Although Polaris is not the brightest star on the sky,...

Explanation: Comet ATLAS is really bright now, but also really close to the Sun. Outside the glow of the Sun, Comet C/2024 G3 (ATLAS) would be one of the more remarkable comet sights of recent years, reflecting about as much sunlight to Earth as Comet Tsuchinshan-ATLAS did in October, and now rivaling even planet Venus. But the giant snowball is now so close to the Sun that it can only be seen through the light of the early morning dawn or the early evening dusk. Today, Comet ATLAS is at perihelion -- its closest ever to the Sun. Although the...

Explanation: Whatever hit Mimas nearly destroyed it. What remains is one of the largest impact craters on one of Saturn's smallest round moons. Analysis indicates that a slightly larger impact would have destroyed Mimas entirely. The huge crater, named Herschel after the 1789 discoverer of Mimas, Sir William Herschel, spans about 130 kilometers and is featured here. Mimas' low mass produces a surface gravity just strong enough to create a spherical body but weak enough to allow such relatively large surface features. Mimas is made of mostly water ice with a smattering of rock - so it is accurately described...

Explanation: Only Mercury is missing from a Solar System parade of planets in this early evening skyscape. Rising nearly opposite the Sun, bright Mars is at the far left. The other naked-eye planets Jupiter, Saturn, and Venus, can also be spotted, with the positions of too-faint Uranus and Neptune marked near the arcing trace of the ecliptic plane. On the far right and close to the western horizon after sunset is a young crescent Moon whose surface is partly illuminated by earthshine. In the foreground of the composite panorama captured on 2 January, planet Earth is represented by Mount Etna's...

Explanation: An unassuming region in the constellation Taurus holds these dark and dusty nebulae. Scattered through the scene, stars in multiple star systems are forming within their natal Taurus molecular cloud complex some 450 light-years away. Millions of years young and still going through stellar adolescence, the stars are variable in brightness and in the late phases of their gravitational collapse. Known as T-Tauri class stars they tend to be faint and take on a yellowish hue in the image. One of the brightest T-Tauri stars in Taurus, V773 (aka HD283447) is near the center of the telescopic frame that...

Explanation: The colorful, spiky stars are in the foreground of this image taken with a small telescope on planet Earth. They lie well within our own Milky Way Galaxy. But the two eye-catching galaxies in the frame lie far beyond the Milky Way, at a distance of over 300 million light-years. The galaxies' twisted and distorted appearance is due to mutual gravitational tides as the pair engage in close encounters. Cataloged as Arp 273 (also as UGC 1810), these galaxies do look peculiar, but interacting galaxies are now understood to be common in the universe. Closer to home, the large...

Explanation: What happens after a star explodes? A huge fireball of hot gas shoots out in all directions. When this gas slams into the existing interstellar medium, it heats up so much it glows. Two different supernova remnants (SNRs) are visible in the featured image, taken at the Oukaïmeden Observatory in Morocco. The blue soccer ball-looking nebula toward the upper left is SNR G179.0+02.6, which appears to be the smaller one. This supernova, about 11,000 light years distant, detonated about 50,000 years ago. Although composed mostly of hydrogen gas, the blue light is emitted by a trace amount of oxygen....

Explanation: It was a new year, and the sky was doubly red. The new year meant that the Earth had returned to its usual place in its orbit on January 1, a place a few days before its closest approach to the Sun. The first of the two red skyglows, on the left, was a red aurora, complete with vertical rays, caused by a blast from the Sun pushing charged particles into Earth's atmosphere. The second red glow, most prominent on the far right, was possibly a SAR arc caused by a river of charged particles flowing across Earth's atmosphere....

Explanation: Billions of years from now, only one of these two galaxies will remain. Until then, spiral galaxies NGC 2207 and IC 2163 will slowly pull each other apart, creating tides of matter, sheets of shocked gas, lanes of dark dust, bursts of star formation, and streams of cast-away stars. The featured image in scientifically assigned colors is a composite of Hubble exposures in visible light and Webb exposures in infrared light. Astronomers predict that NGC 2207, the larger galaxy on the right, will eventually incorporate IC 2163, the smaller galaxy on the left. In the most recent encounter that...

Explanation: Have you ever seen a rocket launch -- from space? A close inspection of the featured time-lapse video will reveal a rocket rising to Earth orbit as seen from the International Space Station (ISS). The Russian Soyuz-FG rocket was launched in November 2018 from the Baikonur Cosmodrome in Kazakhstan, carrying a Progress MS-10 (also 71P) module to bring needed supplies to the ISS. Highlights in the 90-second video (condensing about 15-minutes) include city lights and clouds visible on the Earth on the lower left, blue and gold bands of atmospheric airglow running diagonally across the center, and distant stars...

Explanation: Earth's orbit around the Sun is not a circle, it's an ellipse. The point along its elliptical orbit where our fair planet is closest to the Sun is called perihelion. This year perihelion is today, January 4, at 13:28 UTC, with the Earth about 147 million kilometers from the Sun. For comparison, at aphelion on last July 3 Earth was at its farthest distance from the Sun, some 152 million kilometers away. But distance from the Sun doesn't determine Earth's seasons. It's only by coincidence that the beginning of southern summer (northern winter) on the December solstice - when...

Explanation: Eclipses tend to come in pairs. Twice a year, during an eclipse season that lasts about 34 days, Sun, Moon, and Earth can nearly align. Then the full and new phases of the Moon, separated by just over 14 days, create a lunar and a solar eclipse. But only rarely is the alignment at both new moon and full moon phases during a single eclipse season close enough to produce a pair with both total (or a total and an annular) lunar and solar eclipses. More often, partial eclipses are part of any eclipse season. In fact, the last...

Explanation: Recorded during 2024, this year-spanning series of images reveals a pattern in the seasonal drift of the Sun's daily motion through planet Earth's sky. Known to some as an analemma, the figure-eight curve was captured in exposures taken only at 1pm local time on clear days from Kayseri, Turkiye. Of course the Sun's position on the 2024 solstice dates was at the top and bottom of the curve. They correspond to the astronomical beginning of summer and winter in the north. The points along the curve half-way between the solstices, but not the figure-eight curve crossing point, mark the...

Explanation: The closest star system to the Sun is the Alpha Centauri system. Of the three stars in the system, the dimmest -- called Proxima Centauri -- is actually the nearest star. The bright stars Alpha Centauri A and B form a close binary as they are separated by only 23 times the Earth- Sun distance - slightly greater than the distance between Uranus and the Sun. The Alphasystem is not visible in much of the northern hemisphere. Alpha Centauri A, also known as Rigil Kentaurus, is the brightest star in the constellation of Centaurus and is the fourth brightest...

Explanation: What do you think this is? Here’s a clue: it's bigger than a bread box. Much bigger. The answer is that pictured NGC 4753 is a twisted disk galaxy, where unusual dark dust filaments provide clues about its history. No one is sure what happened, but a leading model holds that a relatively normal disk galaxy gravitationally ripped apart a dusty satellite galaxy while its precession distorted the plane of the accreted debris as it rotated. The cosmic collision is hypothesized to have started about a billion years ago. NGC 4753 is seen from the side, and possibly would...

Explanation: Is this what will become of our Sun? Quite possibly. The first hint of our Sun's future was discovered inadvertently in 1764. At that time, Charles Messier was compiling a list of diffuse objects not to be confused with comets. The 27th object on Messier's list, now known as M27 or the Dumbbell Nebula, is a planetary nebula, one of the brightest planetary nebulas on the sky and visible with binoculars toward the constellation of the Fox (Vulpecula). It takes light about 1000 years to reach us from M27, featured here in colors emitted by sulfur (red), hydrogen (green)...

Explanation: What are these bubbles frozen into Lake Baikal? Methane. Lake Baikal, a UNESCO World Heritage Site in Russia, is the world's largest (by volume), oldest, and deepest lake, containing over 20% of the world's fresh water. The lake is also a vast storehouse of methane, a greenhouse gas that, if released, could potentially increase the amount of infrared light absorbed by Earth's atmosphere, and so increase the average temperature of the entire planet. Fortunately, the amount of methane currently bubbling out is not climatologically important. It is not clear what would happen, though, were temperatures to significantly increase in...

Explanation: Orion seems to come up sideways, climbing over a distant mountain range in this deep skyscape. The wintry scene was captured from southern Poland on the northern hemisphere's long solstice night. Otherwise unseen nebulae hang in the sky, revealed by the camera modified to record red hydrogen-alpha light. The nebulae lie near the edge of the Orion molecular cloud and join the Hunter's familiar belt stars and bright giants Betelgeuse and Rigel. Eye of Taurus the Bull, yellowish Aldebaran anchors the V-shaped Hyades star cluster near top center. Still, near opposition in planet Earth's sky, the Solar System's ruling...