Archives de catégorie : Picture

Windblown NGC 3199

NGC 3199 lies about 12,000 light-years away, a glowing cosmic cloud in the nautical southern constellation of Carina. The nebula is about 75 light-years across in this narrowband, false-color view. Though the deep image reveals a more or less complete bubble shape, it does look very lopsided with a much brighter edge along the top. Near the center is a Wolf-Rayet star, a massive, hot, short-lived star that generates an intense stellar wind. In fact, Wolf-Rayet stars are known to create nebulae with interesting shapes as their powerful winds sweep up surrounding interstellar material. In this case, the bright edge was thought to indicate a bow shock produced as the star plowed through a uniform medium, like a boat through water. But measurements have shown the star is not really moving directly toward the bright edge. So a more likely explanation is that the material surrounding the star is not uniform, but clumped and denser near the bright edge of windblown NGC 3199. via NASA https://ift.tt/3nQ2kKB

STEVE over Copper Harbor

What creates STEVEs? Strong Thermal Emission Velocity Enhancements (STEVEs) have likely been seen since antiquity, but only in the past five years has it been realized that their colors and shapes make them different from auroras. Seen as single bright streaks of pink and purple, the origin of STEVEs remain an active topic of research. STEVEs may be related to subauroral ion drifts (SAIDs), a supersonic river of hot atmospheric ions. For reasons currently unknown, STEVEs are frequently accompanied by green « picket-fence » auroras. The featured STEVE image is a combination of foreground and background exposures taken consecutively in mid-March from Copper Harbor, Michigan, USA. This bright STEVE lasted several minutes, spanned from horizon to horizon, and appeared in between times of normal auroras. via NASA https://ift.tt/33dti5i

Space Station, Solar Prominences, Sun

That’s no sunspot. It’s the International Space Station (ISS) caught passing in front of the Sun. Sunspots, individually, have a dark central umbra, a lighter surrounding penumbra, and no Dragon capsules attached. By contrast, the ISS is a complex and multi-spired mechanism, one of the largest and most complicated spacecraft ever created by humanity. Also, sunspots circle the Sun, whereas the ISS orbits the Earth. Transiting the Sun is not very unusual for the ISS, which orbits the Earth about every 90 minutes, but getting one’s location, timing and equipment just right for a great image is rare. The featured picture combined three images all taken from the same location and at nearly the same time. One image — overexposed — captured the faint prominences seen across the top of the Sun, a second image — underexposed — captured the complex texture of the Sun’s chromosphere, while the third image — the hardest to get — captured the space station as it shot across the Sun in a fraction of a second. Close inspection of the space station’s silhouette even reveals a docked Dragon Crew capsule. via NASA https://ift.tt/33bXUnF

Apollo 11: Earth, Moon, Spaceship

After the most famous voyage of modern times, it was time to go home. After proving that humanity has the ability to go beyond the confines of planet Earth, the first humans to walk on another world — Neil Armstrong and Buzz Aldrin — flew the ascent stage of their Lunar Module back to meet Michael Collins in the moon-orbiting Command and Service Module. Pictured here on 1969 July 21 and recently digitally restored, the ascending spaceship was captured by Collins making its approach, with the Moon below, and Earth far in the distance. The smooth, dark area on the lunar surface is Mare Smythii located just below the equator on the extreme eastern edge of the Moon’s near side. It is said of this iconic image that every person but one was in front of the camera. via NASA https://ift.tt/2RnvuEv

Clouds of the Carina Nebula

What forms lurk in the mists of the Carina Nebula? The dark ominous figures are actually molecular clouds, knots of molecular gas and dust so thick they have become opaque. In comparison, however, these clouds are typically much less dense than Earth’s atmosphere. Featured here is a detailed image of the core of the Carina Nebula, a part where both dark and colorful clouds of gas and dust are particularly prominent. The image was captured in mid-2016 from Siding Spring Observatory in Australia. Although the nebula is predominantly composed of hydrogen gas — here colored green, the image was assigned colors so that light emitted by trace amounts of sulfur and oxygen appear red and blue, respectively. The entire Carina Nebula, cataloged as NGC 3372, spans over 300 light years and lies about 7,500 light-years away in the constellation of Carina. Eta Carinae, the most energetic star in the nebula, was one of the brightest stars in the sky in the 1830s, but then faded dramatically. via NASA https://ift.tt/3xAJKe1

Perseverance from Ingenuity

Flying at an altitude of 5 meters (just over 16 feet), on April 25 the Ingenuity helicopter snapped this sharp image. On its second flight above the surface of Mars, its color camera was looking back toward Ingenuity’s current base at Wright Brothers Field and Octavia E. Butler Landing marked by the tracks of the Perseverance rover at the top of the frame. Perseverance itself looks on from the upper left corner about 85 meters away. Tips of Ingenuity’s landing legs just peek over the left and right edges of the camera’s field of view. Its record setting fourth flight completed on April 30, Ingenuity collected images of a potential new landing zone before returning to Wright Brothers Field. Ingenuity’s fifth flight would be one-way though as the Mars aircraft moves on to the new airfield, anticipating a new phase of operational demonstration flights. via NASA https://ift.tt/3vxrekD

Pink and the Perigee Moon

On April 25 a nearly full moon rose just before sunset. Welcomed in a clear blue sky and framed by cherry blossoms, its familiar face was captured in this snapshot from Leith, Edinburgh, Scotland. Known to some as a Pink Moon, April’s full lunar phase occurred with the moon near perigee. That’s the closest point in its not-quite-circular orbit around planet Earth, making this Pink Moon one of the closest and brightest full moons of the year. If you missed it, don’t worry. Your next chance to see a full perigee moon will be on May 26. Known to some as a Flower Moon, May’s full moon will actually be closer to you than April’s by about 98 miles (158 kilometers), or about 0.04% the distance from the Earth to the Moon at perigee. via NASA https://ift.tt/3xBploX

Apollo 17: The Crescent Earth

Our fair planet sports a curved, sunlit crescent against the black backdrop of space in this stunning photograph. From the unfamiliar perspective, the Earth is small and, like a telescopic image of a distant planet, the entire horizon is completely within the field of view. Enjoyed by crews on board the International Space Station, only much closer views of the planet are possible from low Earth orbit. Orbiting the planet once every 90 minutes, a spectacle of clouds, oceans, and continents scrolls beneath them with the partial arc of the planet’s edge in the distance. But this digitally restored image presents a view so far only achieved by 24 humans, Apollo astronauts who traveled to the Moon and back again between 1968 and 1972. The original photograph, AS17-152-23420, was taken by the homeward bound crew of Apollo 17, on December 17, 1972. For now it’s the last picture of Earth from this planetary perspective taken by human hands. via NASA https://ift.tt/3e36g7e

North Star: Polaris and Surrounding Dust

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 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, it is easily located because it is nearly aligned with two stars in the cup of the Big Dipper. Polaris is near the center of the eight-degree wide featured image, an image that has been digitally manipulated to suppress surrounding dim stars but accentuate the faint gas and dust of the Intergalactic Flux Nebula (IFN). The surface of Cepheid Polaris slowly pulsates, causing the star to change its brightness by a few percent over the course of a few days. via NASA https://ift.tt/3tZG4QI

Animation: Black Hole Star Shredder

What happens if a star gets too close to a black hole? The black hole can rip it apart — but how? It’s not the high gravitational attraction itself that’s the problem — it’s the difference in gravitational pull across the star that creates the destruction. In the featured animated video illustrating this disintegration, you first see a star approaching the black hole. Increasing in orbital speed, the star’s outer atmosphere is ripped away during closest approach. Much of the star’s atmosphere disperses into deep space, but some continues to orbit the black hole and forms an accretion disk. The animation then takes you into the accretion disk while looking toward the black hole. Including the strange visual effects of gravitational lensing, you can even see the far side of the disk. Finally, you look along one of the jets being expelled along the spin axis. Theoretical models indicate that these jets not only expel energetic gas, but create energetic neutrinos — one of which may have been seen recently on Earth. via NASA https://ift.tt/3tXelQr