NASA Astronomy Picture of the Day:

What lies at the end of a rainbow? Something different for everyone. For the photographer taking this picture, for example, one end of the rainbow ended at a tree. Others nearby, though, would likely see the rainbow end somewhere else. The reason is because a rainbow's position depends on the observer. The center of a rainbow always appears in the direction opposite the Sun, but that direction lines up differently on the horizon from different locations. This rainbow's arc indicates that its center is about 40 degrees to the left and slightly below the horizon, while the Sun is well behind the camera and just above the horizon. Reflections and refractions of sunlight from raindrops in a distant storm in the direction of the rainbow are what causes the colorful bands of light. This single exposure image was captured in early January near Knight's Ferry, California, USA.

Photo by Eric Houck

NASA Astronomy Picture of the Day:

What lies at the bottom of Hyperion's strange craters? To help find out, the robot Cassini spacecraft that once orbited Saturn swooped past the sponge-textured moon and took images of unprecedented detail. A six-image mosaic from the 2005 pass, featured here in scientifically assigned colors, shows a remarkable world strewn with strange craters and an odd, sponge-like surface. At the bottom of most craters lies some type of unknown dark reddish material. This material appears similar to that covering part of another of Saturn's moons, Iapetus, and might sink into the ice moon as it better absorbs warming sunlight. Hyperion is about 250 kilometers across, rotates chaotically, and has a density so low that it likely houses a vast system of caverns inside.

NASA Astronomy Picture of the Day:

Put on your red/blue glasses and float next to asteroid 101955 Bennu. Shaped like a spinning toy top with boulders littering its rough surface, the tiny Solar System world is about one Empire State Building (less than 500 meters) across. Frames used to construct this 3D anaglyph were taken by PolyCam on the OSIRIS_REx spacecraft on December 3, 2018 from a distance of about 80 kilometers. With a sample from the asteroid's rocky surface on board, OSIRIS_REx departed Bennu's vicinity in May of 2021 and is now enroute to planet Earth. The robotic spacecraft is scheduled to return the sample to Earth this September.

NASA Astronomy Picture of the Day:

Few cosmic vistas excite the imagination like The Great Nebula in Orion. Visible as a faint celestial smudge to the naked-eye, the nearest large star-forming region sprawls across this sharp telescopic image, recorded on a cold January night in dark skies from West Virginia, planet Earth. Also known as M42, the Orion Nebula's glowing gas surrounds hot, young stars. About 40 light-years across, it lies at the edge of an immense interstellar molecular cloud only 1,500 light-years away within the same spiral arm of our Milky Way galaxy as the Sun. Along with dusty bluish reflection nebula NGC 1977 and friends near the top of the frame, the eye-catching nebulae represent only a small fraction of our galactic neighborhood's wealth of star-forming material. Within the well-studied stellar nursery, astronomers have also identified what appear to be numerous infant solar systems.

Photo by Abraham Jones

NASA Astronomy Picture of the Day:

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.

NASA Astronomy Picture of the Day:

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. Light Up Your Internal Night Sky: Random APOD Generator

NASA Astronomy Picture of the Day:

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. Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)

Photo by Yuri BeletskyCarnegieLas Campanas ObservatoryTWAN

NASA Astronomy Picture of the Day:

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. Jupiter & Venus Conjunction Gallery: Notable Submissions to APOD

Photo by Marek NikodemPPSAE

NASA Astronomy Picture of the Day:

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. Jupiter & Venus Conjunction Gallery: Notable Submissions to APOD

Photo by Giovanni Tumino

NASA Astronomy Picture of the Day:

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. Jupiter & Venus Conjunction Gallery: Notable Submissions to APOD

Photo by Soumyadeep Mukherjee

NASA Astronomy Picture of the Day:

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.

NASA Astronomy Picture of the Day:

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.

Photo by Mike Selby