Astronomy Picture of the Day [ko]

CG 30: Cometary Globules

2026-04-28T03:00:00+00:00

Explanation: They're like mountain peaks, but they are forming stars. Bright-rimmed, flowing shapes gather near the center of this rich starfield toward the borders of the nautical southern constellations Puppis and Vela. Composed of interstellar gas and dust, the grouping of light-year sized cometary globules is about 1300 light-years distant. Energetic ultraviolet light from nearby hot stars has molded the globules and ionized their bright rims. The globules also stream away from the Vela supernova remnant which may have influenced their swept-back shapes. Within them, cores of cold gas and dust are likely collapsing to form low mass stars whose formation will ultimately cause the globules to disperse. In fact, cometary globule CG 30 (upper right in the group) sports a small reddish glow inside its head, a telltale sign of energetic jets from a star in the early stages of formation.

Comet R3 PanSTARRS Behind Satellite Trails

2026-04-27T03:00:00+00:00

Explanation: Can you find the comet? Somewhere through this web of satellite trails is Comet C/2025 R3 (PanSTARRS), a bright visitor passing through the inner Solar System. Now, the orbiting satellites themselves only appear as streaks because of the long camera exposure, over 10 minutes in this case. On the contrary, to the eye, satellites appear as points that drift slowly across the night sky and shine by reflecting sunlight -- primarily just after sunset and before sunrise. The featured image was taken just before sunrise two weeks ago from Bavaria, Germany. Presently, Comet R3 PanSTARRS is hard to see for even another reason -- because it is so (angularly) close to the Sun. As the comet rounds the Sun, it will be best seen in coming weeks from southern hemispheree skies, although then it will be heading out to interstellar space and fading. If you haven't yet found the comet, don't despair; please take a closer look just above the image center.

Mystic Mountain Monster being Destroyed

2026-04-26T03:00:00+00:00

Explanation: Inside the head of this interstellar monster is a star that is slowly destroying it. The huge monster, actually an inanimate series of pillars of gas and dust, measures light years in length. The in-head star is not itself visible through the opaque interstellar dust but is bursting out partly by ejecting opposing beams of energetic particles called Herbig-Haro jets. Located about 7,500 light years away in the Carina Nebula and known informally as Mystic Mountain, the appearance of these pillars is dominated by dark dust even though they are composed mostly of clear hydrogen gas. The featured image was taken with the Hubble Space Telescope. All over these pillars, the energetic light and winds from massive newly formed stars are evaporating and dispersing the dusty stellar nurseries in which they formed. Within a few million years, the head of this giant, as well as most of its body, will have been completely evaporated by internal and surrounding stars.

The Persistence of Sunlight

2026-04-25T03:00:00+00:00

Explanation: This seaside sunset offered a surreal experience, captured in a sea and skyscape from the west coast of Sardinia, Italy, planet Earth. The Daliesque scene is a composition of sequential exposures made with a camera and long telephoto lens. The Sun is not melting, though. Its shifting and fluid appearance as it nears the horizon is caused as refraction along the line of sight changes and creates distorted images or mirages of the reddened solar disk. The changes in atmospheric refraction correspond to atmospheric layers with sharply different temperatures and densities. Another famous but fleeting effect of atmospheric refraction produced by a long sight-line to the setting (or rising) Sun is often called the green flash.

Young Moon and Sister Stars

2026-04-24T03:00:00+00:00

Explanation: Sunlit arms of a crescent moon seem to embrace the faint lunar night side in this dramatic celestial view from planet Earth. The single telephoto exposure tracking the sky was captured on the night of April 19, when a two day old Moon was near perigee in its elliptical orbit. On that date, the young Moon was also close on the sky to the lovely Pleiades Star Cluster. With the moonlight dimmed by clouds the Pleiades sister stars gather below the Moon's bright crescent, seen through a faint but colorful lunar corona. The lunar night side is illuminated by earthshine, sunlight reflected from the Earth itself. The Moon's ashen glow, also known as the "old moon in the young moon's arms," tends to be bright in the northern hemisphere spring. And for now, the Moon's orbit takes it near the Pleiades stars each month in planet Earth's sky, though their close conjunctions are easiest to see when the Moon is near a crescent phase.

Large Scale Structure of the Universe

2026-04-23T03:00:00+00:00

Explanation: This is a map of the universe. The Dark Energy Spectroscopic Instrument (DESI) at Kitt Peak National Observatory, Arizona, has finished its five-year survey. It observed more than 47 million galaxies and quasars and created a 3D map centered on the Earth. Today's featured image shows a thin slice of these data: the black gaps indicate where our Galaxy obscures distant objects. The feathery web in the inset shows the large scale structure of the universe. Light of the most distant galaxies shown here travelled for 11 billion years to reach the Earth. Galaxies cluster throughout cosmic history under the competing influences of gravity and dark energy, responsible for the accelerated expansion of the universe. Analysis of early DESI results hinted at the possibility that dark energy, described as a cosmological constant by Albert Einstein, may not be constant after all. But we still have to wait for the analysis of the now complete dataset. The nature of dark energy is the biggest mystery of cosmology.

Earthset with an iPhone

2026-04-22T03:00:00+00:00

Explanation: What does it mean for the Earth to set? Artemis II Commander Reid Wiseman gave us another spectacular view of Earth from their historic flyby of the Moon. Commander Wiseman's video, taken with an iPhone at 8x zoom, shows our entire planet gradually blocked from view by the Moon. On the Earth, the 24-hour planetary rotation causes the Sun to set below your horizon every night. However, on Artemis II the Earthset was caused not by the Moon’s rotation but by the spacecraft moving behind the Moon (at about 55 seconds in this video). Once rare, views of Earth are now taken many times a day from many spacecraft, including NASA’s SWOT (Surface Water and Ocean Topography) satellite tracking freshwater resources and USGS Landsat 8 and 9 satellites supporting water management for farmers, for example. Space agencies around our home planet now work together to provide unique and ever-improving views of our Earth.