Does Mars have a north star? In long exposures of Earth’s night sky, star trails make concentric arcs around the north celestial pole, the direction of our fair planet’s axis of rotation. Bright star Polaris is presently the Earth’s North Star, close on the sky to Earth’s north celestial pole. But long exposures on Mars show star trails too, concentric arcs about a celestial pole determined by Mars’ axis of rotation. Tilted like planet Earth’s, the martian axis of rotation points in a different direction in space though. It points to a place on the sky between stars in Cygnus and Cepheus with no bright star comparable to Earth’s north star Polaris nearby. So even though this ruddy, weathered landscape is remarkably reminiscent of terrain in images from the martian surface, the view must be from planet Earth, with north star Polaris near the center of concentric star trails. The landforms in the foreground are found in Qinghai Province in northwestern China.
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Looping through the Jovian system in the late 1990s, the Galileo spacecraft recorded stunning views of Europa and uncovered evidence that the moon’s icy surface likely hides a deep, global ocean. Galileo’s Europa image data has been remastered here, using improved new calibrations to produce a color image approximating what the human eye might see. Europa’s long curving fractures hint at the subsurface liquid water. The tidal flexing the large moon experiences in its elliptical orbit around Jupiter supplies the energy to keep the ocean liquid. But more tantalizing is the possibility that even in the absence of sunlight that process could also supply the energy to support life, making Europa one of the best places to look for life beyond Earth. What kind of life could thrive in a deep, dark, subsurface ocean? Consider planet Earth’s own extreme shrimp.
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Is this one galaxy or two? This question came to light in 1950 when astronomer Arthur Hoag chanced upon this unusual extragalactic object. On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older. Between the two is a gap that appears almost completely dark. How Hoag’s Object formed, including its nearly perfectly round ring of stars and gas, remains unknown. Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished. The featured photo was taken by the Hubble Space Telescope and recently reprocessed using an artificially intelligent de-noising algorithm. Observations in radio waves indicate that Hoag’s Object has not accreted a smaller galaxy in the past billion years. Hoag’s Object spans about 100,000 light years and lies about 600 million light years away toward the constellation of the Snake (Serpens). Many galaxies far in the distance are visible toward the right, while coincidentally, visible in the gap at about seven o’clock, is another but more distant ring galaxy.
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What are those two bright objects on the horizon? Venus and Jupiter. The two brightest planets in the night sky passed very close together — angularly — just two days ago. In real space, they were just about as far apart as usual, since Jupiter (on the right) orbits the Sun around seven times farther out than Venus. The planetary duo were captured together two days ago in a picturesque sunset sky from Llers, Catalonia, Spain between a tree and the astrophotographer’s daughter. These two planets will continue to stand out in the evening sky, toward the west, for the next few days, with a sliver of a crescent Moon and a fainter Saturn also visible nearby. As November ends, Jupiter will sink lower into the sunset horizon with each subsequent night, while Venus will rise higher. The next Jupiter-Venus conjunction will occur in early 2021.
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Do you see the bat? It haunts this cosmic close-up of the eastern Veil Nebula. The Veil Nebula itself is a large supernova remnant, the expanding debris cloud from the death explosion of a massive star. While the Veil is roughly circular in shape and covers nearly 3 degrees on the sky toward the constellation of the Swan (Cygnus), the Bat Nebula, NGC 6995, spans only 1/2 degree, about the apparent size of the Moon. That translates to 12 light-years at the Veil’s estimated distance, a reassuring 1,400 light-years from planet Earth. In the composite of image data recorded through broad and narrow band filters, emission from hydrogen atoms in the remnant is shown in red with strong emission from oxygen and nitrogen atoms shown in hues of blue. Of course, in the western part of the Veil lies another seasonal apparition: the Witch’s Broom Nebula.
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Put on your red/blue glasses and gaze across the western Ocean of Storms on the surface of the Moon. The 3D view features Apollo 12 astronaut Pete Conrad visiting the Surveyor 3 spacecraft 50 years ago in November of 1969. Surveyor 3 had landed at the site on the inside slope of a small crater about 2 1/2 years earlier in April of 1967. Visible on the horizon beyond the far crater wall, Apollo 12’s Lunar Module Intrepid touched down less than 200 meters (650 feet) away, easy moonwalking distance from the robotic Surveyor spacecraft. The stereo image was carefully created from two separate pictures (AS12-48-7133, AS12-48-7134) taken on the lunar surface. They depict the scene from only slightly different viewpoints, approximating the separation between human eyes.
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Looking toward the east in the early hours of a September morning this single exposure made with tripod and camera captured a simple visual experience. Rising above the tree-lined slope are familiar stars in planet Earth’s northern night and the constellation Orion the Hunter. Brighter stars marking the celestial Hunter’s shoulder (Betelgeuse), foot (Rigel), belt, and sword are clearly reflected in the calm waters from northern Latvia’s Vitrupe river. Of course, winter is coming to planet Earth’s northern hemisphere. By then Orion and this beautiful starry vista will be seen rising in early evening skies.
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It’s easy to get lost following the intricate looping filaments in this detailed image of supernova remnant Simeis 147. Also cataloged as Sharpless 2-240 it goes by the popular nickname, the Spaghetti Nebula. Seen toward the boundary of the constellations Taurus and Auriga, it covers nearly 3 degrees or 6 full moons on the sky. That’s about 150 light-years at the stellar debris cloud’s estimated distance of 3,000 light-years. This composite includes image data taken through narrow-band filters where reddish emission from ionized hydrogen atoms and doubly ionized oxygen atoms in faint blue-green hues trace the shocked, glowing gas. The supernova remnant has an estimated age of about 40,000 years, meaning light from the massive stellar explosion first reached Earth 40,000 years ago. But the expanding remnant is not the only aftermath. The cosmic catastrophe also left behind a spinning neutron star or pulsar, all that remains of the original star’s core.
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Can a lighthouse illuminate a galaxy? No, but in the featured image, gaps in light emanating from the Jose Ignacio Lighthouse in Uruguay appear to match up nicely, although only momentarily and coincidently, with dark dust lanes of our Milky Way Galaxy. The bright dot on the right is the planet Jupiter. The central band of the Milky Way Galaxy is actually the central spiral disk seen from within the disk. The Milky Way band is not easily visible through city lights but can be quite spectacular to see in dark skies. The featured picture is actually the addition of ten consecutive images taken by the same camera from the same location. The images were well planned to exclude direct light from the famous lighthouse.
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What would it look like to pass asteroid Arrokoth? The robotic New Horizons spacecraft zoomed past Arrokoth in January, 3.5 years after the spacecraft passed Pluto. If this object’s name doesn’t sound familiar, that may be because the distant, double-lobed, Kuiper-belt object was unofficially dubbed Ultima Thule until recently receiving its official name: 486958 Arrokoth. The featured black and white video animates images of Arrokoth taken by New Horizons at different angles as it zoomed by. The video clearly shows Arrokoth’s two lobes, and even hints that the larger lobe is significantly flattened. New Horizons found that Arrokoth is different from any known asteroid in the inner Solar System and is likely composed of two joined planetesimals — the building blocks of planets as they existed billions of years ago. New Horizons continues to speed out of our Solar System gaining about three additional Earth-Sun separations every year.
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