NASA Astronomy Picture of the Day:

Massive stars in our Milky Way Galaxy live spectacular lives. Collapsing from vast cosmic clouds, their nuclear furnaces ignite and create heavy elements in their cores. After only a few million years for the most massive stars, the enriched material is blasted back into interstellar space where star formation can begin anew. The expanding debris cloud known as Cassiopeia A is an example of this final phase of the stellar life cycle. Light from the supernova explosion that created this remnant would have been first seen in planet Earth's sky about 350 years ago, although it took that light 11,000 years to reach us. This sharp NIRCam image from the James Webb Space Telescope shows the still hot filaments and knots in the supernova remnant. The whitish, smoke-like outer shell of the expanding blast wave is about 20 light-years across. Light echoes from the massive star's cataclysmic explosion are also identified in Webb's detailed image of supernova remnant Cassiopeia A. Tonight watch: The Geminids

NASA Astronomy Picture of the Day:

What excites the Heart Nebula? First, the large emission nebula on the left, catalogued as IC 1805, looks somewhat like a human heart. The nebula glows brightly in red light emitted by its most prominent element, hydrogen, but this long-exposure image was also blended with light emitted by silicon (yellow) and oxygen (blue). In the center of the Heart Nebula are young stars from the open star cluster Melotte 15 that are eroding away several picturesque dust pillars with their atom-exciting energetic light and winds. The Heart Nebula is located about 7,500 light years away toward the constellation of Cassiopeia. At the bottom right of the Heart Nebula is the companion Fishhead Nebula. This wide and deep image clearly shows, though, that glowing gas surrounds the Heart Nebula in all directions. Tonight watch: The Geminids

Photo by William Ostling, Telescope Live

NASA Astronomy Picture of the Day:

What are these two giant arches across the sky? Perhaps the more familiar one, on the left, is the central band of our Milky Way Galaxy. This grand disk of stars and nebulas here appears to encircle much of the southern sky. Visible below the stellar arch is the rusty-orange planet Mars and the extended Andromeda galaxy. But this night had more! For a few minutes during this cold arctic night, a second giant arch appeared encircling part of the northern sky: an aurora. Auroras are much closer than stars as they are composed of glowing air high in Earth's atmosphere. Visible outside the green auroral arch is the group of stars popularly known as the Big Dipper. The featured digital composite of 20 images was captured in mid-November 2022 over the Lofoten Islands in Norway. APOD Year in Review (2023): RJN's Night Sky Network Lecture

Photo by Giulio Cobianchi

NASA Astronomy Picture of the Day:

The surface of our Sun is constantly changing. Some years it is quiet, showing relatively few sunspots and active regions. Other years it is churning, showing many sunspots and throwing frequent Coronal Mass Ejections (CMEs) and flares. Reacting to magnetism, our Sun's surface goes through periods of relative calm, called Solar Minimum and relative unrest, called Solar Maximum, every 11 years. The featured video shows on the left a month in late 2019 when the Sun was near Solar Minimum, while on the right a month in 2014 when near Solar Maximum. The video was taken by NASA's Solar Dynamic Observatory in far ultraviolet light. Our Sun is progressing again toward Solar Maximum in 2025, but displaying even now a surface with a surprisingly high amount of activity. Night Sky Network webinar: APOD editor to review coolest space images of 2023

NASA Astronomy Picture of the Day:

When did you first learn to identify this group of stars? Although they are familiar to many people around the world, different cultures have associated this asterism with different icons and folklore. Known in the USA as the Big Dipper, the stars are part of a constellation designated by the International Astronomical Union in 1922 as the Great Bear (Ursa Major). The recognized star names of these stars are (left to right) Alkaid, Mizar/Alcor, Alioth, Megrez, Phecda, Merak, and Dubhe. Of course, stars in any given constellation are unlikely to be physically related. But surprisingly, most of the Big Dipper stars do seem to be headed in the same direction as they plough through space, a property they share with other stars spread out over an even larger area across the sky. Their measured common motion suggests that they all belong to a loose, nearby star cluster, thought to be on average only about 75 light-years away and up to 30 light-years across. The cluster is more properly known as the Ursa Major Moving Group. The featured image captured the iconic stars in 2017 above Pyramid Mountain in Alberta, Canada. Night Sky Network webinar: APOD editor to review coolest space images of 2023

Photo by Steve Cullen

NASA Astronomy Picture of the Day:

Near dawn on November 19 the Pleiades stood in still dark skies over the French Pyrenees. But just before sunrise a serendipitous moment was captured in this single 3 second exposure; a bright meteor streak appeared to pierce the heart of the galactic star cluster. From the camera's perspective, star cluster and meteor were poised directly above the mountain top observatory on the Pic du Midi de Bigorre. And though astronomers might consider the Pleiades to be relatively close by, the grain of dust vaporizing as it plowed through planet Earth's upper atmosphere actually missed the cluster's tight grouping of young stars by about 400 light-years. While recording a night sky timelapse series, the camera and telephoto lens were fixed to a tripod on the Tour-de-France-cycled slopes of the Col du Tourmalet about 5 kilometers from the Pic du Midi.

Photo by Jean-Francois Graffand

NASA Astronomy Picture of the Day:

On December 4, periodic Comet 12P/Pons-Brooks shared this telescopic field of view with Vega, alpha star of the northern constellation Lyra. Fifth brightest star in planet Earth's night, Vega is some 25 light-years distant while the much fainter comet was about 21 light-minutes away. In recent months, outbursts have caused dramatic increases in brightness for Pons-Brooks though. Nicknamed the Devil Comet for its hornlike appearance, fans of interstellar spaceflight have also suggested the distorted shape of this comet's large coma looks like the Millenium Falcon. A Halley-type comet, 12P/Pons-Brooks last visited the inner Solar System in 1954. Its next perihelion passage or closest approach to the Sun will be April 21, 2024. That's just two weeks after the April 8 total solar eclipse path crosses North America. But, highly inclined to the Solar System's ecliptic plane, the orbit of periodic Comet 12P/Pons-Brooks will never cross the orbit of planet Earth.

Photo by Dan Bartlett

NASA Astronomy Picture of the Day:

On December 5, 2022, a camera on board the uncrewed Orion spacecraft captured this view as Orion approached its return powered flyby of the Moon. Beyond one of Orion's extended solar arrays lies dark, smooth, terrain along the western edge of the Oceanus Procellarum. Prominent on the lunar nearside Oceanus Procellarum, the Ocean of Storms, is the largest of the Moon's lava-flooded maria. The lunar terminator, shadow line between lunar night and day, runs along the left of this frame. The 41 kilometer diameter crater Marius is top center, with ray crater Kepler peeking in at the edge, just right of the solar array wing. Kepler's bright rays extend to the north and west, reaching the dark-floored Marius. By December 11, 2022 the Orion spacecraft had reached its home world. The historic Artemis 1 mission ended with Orion's successful splashdown in planet Earth's water-flooded Pacific Ocean.

NASA Astronomy Picture of the Day:

It's stars versus dust in the Carina Nebula and the stars are winning. More precisely, the energetic light and winds from massive newly formed stars are evaporating and dispersing the dusty stellar nurseries in which they formed. Located in the Carina Nebula and inside a region known informally as Mystic Mountain, these pillars' appearance is dominated by opaque brown dust even though it is composed mostly of clear hydrogen gas. Even though some of the dust pillars look like torches, their ends are not on fire -- rather, they are illuminated by nearby stars. About 7,500 light-years distant, the featured image was taken with the Hubble Space Telescope and highlights an interior region of Carina known as HH1066 which spans nearly a light year. Within a few million years, the stars will likely win out completely and the dust torches will completely evaporate.

NASA Astronomy Picture of the Day:

It was one of the most energetic particles ever known to strike the Earth -- but where did it come from? Dubbed Amaterasu after the Shinto sun goddess, this particle, as do all cosmic rays that strike the Earth's atmosphere, caused an air shower of electrons, protons, and other elementary particles to spray down onto the Earth below. In the featured illustration, a cosmic ray air shower is pictured striking the Telescope Array in Utah, USA, which recorded the Amaterasu event in 2021 May. Cosmic ray air showers are common enough that you likely have been in a particle spray yourself, although you likely wouldn't have noticed. The origin of this energetic particle, likely the nucleus of an atom, remains a mystery in two ways. First, it is not known how any single particle or atomic nucleus can practically acquire so much energy, and second, attempts to trace the particle back to where it originated did not indicate any likely potential source. Open Science: Browse 3,200+ codes in the Astrophysics Source Code Library

NASA Astronomy Picture of the Day:

No, the Moon is not a bow, and no, it did not shoot out a plane like an arrow. What is pictured is a chance superposition. The plane's contrail would normally appear white, but the large volume of air toward the rising Sun preferentially knocked away blue light, not only making the sky blue, but giving the reflected trail a bright red hue. Far in the distance, well behind the plane, the crescent Moon also appears slightly reddened. Captured early last month from Bolton, UK, the featured image was taken so soon after sunrise that the plane was sunlit from below, as was its contrail. Within minutes, unfortunately, the impromptu sky show ended. The plane moved out of sight. The Moon kept rising but became harder to see through a brightening sky. And the contrail gradually dispersed.

Photo by Juned Patel

NASA Astronomy Picture of the Day:

These people are not in danger. What is coming down from the left is just the Moon, far in the distance. Luna appears so large here because she is being photographed through a telescopic lens. What is moving is mostly the Earth, whose spin causes the Moon to slowly disappear behind Mount Teide, a volcano in the Canary Islands off the northwest coast of Africa. The people pictured are 16 kilometers away and many are facing the camera because they are watching the Sun rise behind the photographer. It is not a coincidence that a full moon rises just when the Sun sets because the Sun is always on the opposite side of the sky from a full moon. The featured video was made in 2018 during the full Milk Moon. The video is not time-lapse -- this was really how fast the Moon was setting.

Video by El Cielo de Canarias