ASTRONOMY - Messier 99

 2021 June 24

Messier 99
Image Credit: NASA, ESA, Hubble, Janice Lee; Processing & Copyright: Leo Shatz

Explanation: Grand design spiral galaxy Messier 99 looks majestic on a truly cosmic scale. This recently processed full galaxy portrait stretches over 70,000 light-years across M99. The sharp view is a combination of ultraviolet, visible, and infrared image data from the Hubble Space Telescope. About 50 million light-years distant toward the well-groomed constellation Coma Bernices, the face-on spiral is a member of the nearby Virgo Galaxy Cluster. Also cataloged as NGC 4254, a close encounter with another Virgo cluster member has likely influenced the shape of its well-defined, blue spiral arms.

ASTRONOMY - HD 163296: Jet from a Star in Formation

 2021 June 22

HD 163296: Jet from a Star in Formation
Image Credit: Visible: VLT/MUSE (ESO); Radio: ALMA (ESO/NAOJ/NRAO)

Explanation: How are jets created during star formation? No one is sure, although recent images of the young star system HD 163296 are quite illuminating. The central star in the featured image is still forming but seen already surrounded by a rotating disk and an outward moving jet. The disk is shown in radio waves taken by the Atacama Large Millimeter Array (ALMA) in Chile, and show gaps likely created by the gravity of very-young planets. The jet, shown in visible light taken by the Very Large Telescope (VLT, also in Chile), expels fast-moving gas -- mostly hydrogen -- from the disk center. The system spans hundreds of times the Earth-Sun distance (au). Details of these new observations are being interpreted to bolster conjectures that the jets are generated and shaped, at least in part, by magnetic fields in the rotating disk. Future observations of HD 163296 and other similar star-forming systems may help fill in details.

AERONAUTIQUE - Le F-8 Crusader

"F-8 Crusader"

ASTRONOMY - Northern Summer Twilight

 2021 June 19

Northern Summer Twilight
Image Credit & Copyright: Justin Anderson

Explanation: Nights grow shorter and days grow longer as the summer solstice approaches in the north. Usually seen at high latitudes in summer months, noctilucent or night shining clouds begin to make their appearance. Drifting near the edge of space about 80 kilometers above the Earth's surface, these icy clouds were still reflecting the sunlight on June 14. Though the Sun was below the horizon as seen north of Forrest, Manitoba, Canada, they were caught in a single exposure of a near midnight twilight sky. Multiple exposures of the foreground track the lower altitude flash of fireflies, another fleeting apparition shining in the summer night.

ASTRONOMY - Devil Horns from a Ring of Fire

 2021 June 18

Devil Horns from a Ring of Fire
Image Credit & Copyright: Madhup Rathi

Explanation: Atmospheric refraction flattened the solar disk and distorted its appearance in this telescopic view of an Atlantic sunrise on June 10. From Belmar, New Jersey on the US east coast, the scene was recorded at New Moon during this season's annular solar eclipse. The Moon in partial silhouette gives the rising Sun its crescent shape reminding some of the horns of the devil (or maybe a flying canoe ...). But at its full annular phase this eclipsed Sun looked like a ring of fire in the heavens. June's annular solar eclipse followed on the heels of the total lunar eclipse of late May's Full Moon. Of course, that total lunar eclipse was a dramatic red Blood Moon eclipse.

ASTRONOMY - NGC 6888: The Crescent Nebula

 2021 June 17

NGC 6888: The Crescent Nebula
Image Credit & Copyright: Joe Navara, Glenn Clouder, Russell Discombe

Explanation: NGC 6888, also known as the Crescent Nebula, is a about 25 light-years across blown by winds from its central, bright, massive star. A triumvirate of astroimagers ( Joe, Glenn, Russell) created this sharp portrait of the cosmic bubble. Their telescopic collaboration collected over 30 hours of narrow band image data isolating light from hydrogen and oxygen atoms. The oxygen atoms produce the blue-green hue that seems to enshroud the detailed folds and filaments. Visible within the nebula, NGC 6888's central star is classified as a Wolf-Rayet star (WR 136). The star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun's mass every 10,000 years. The nebula's complex structures are likely the result of this strong wind interacting with material ejected in an earlier phase. Burning fuel at a prodigious rate and near the end of its stellar life this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.

PRATIQUE/POURQUOI - Pourquoi y a-t-il des "trous d'air" en avion ?

L'air qui nous entoure n'est pas homogène. Il y a des masses chaudes (qui ont tendance à monter) et des masses froides (qui ont tendance à descendre). Elles évoluent en permanence.

Un avion qui vole relativement vite par rapport aux masses d'air rencontre donc dans sa trajectoire des masses d'air qui montent ou qui descendent. Ses passagers ressentent donc les évolutions vers le haut ou le bas de l'appareil (communément appelées ''trous d'air'').

Ces phénomènes se rencontrent surtout près et dans les complexes orageux et c'est pourquoi il est recommandé par l'équipage d'attacher sa ceinture de sécurité alors qu'on est loin de l'arrivée afin de ne pas finir son sandwitch collé au plafond.

ASTRONOMY - Scorpius Enhanced

 2021 June 16

Scorpius Enhanced
Image Credit & Copyright: Stefan Lenz

Explanation: If Scorpius looked this good to the unaided eye, humans might remember it better. Scorpius more typically appears as a few bright stars in a well-known but rarely pointed out zodiacal constellation. To get a spectacular image like this, though, one needs a good camera, a dark sky, and some sophisticated image processing. The resulting digitally-enhanced image shows many breathtaking features. Diagonal across the image right is part of the plane of our Milky Way Galaxy. Visible there are vast clouds of bright stars and long filaments of dark and intricate dust. Rising vertically on the image left are dark dust bands known as the Dark River. Several of the bright stars on the left are part of Scorpius' head and claws, and include the bright star Antares. Numerous red emission nebulas, blue reflection nebulas, and dark filaments became visible as the deep 17-hour expo image developed. Scorpius appears prominently in southern skies after sunset during the middle of the year.

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ASTRONOMY - Zhurong: New Rover on Mars

 2021 June 15

Zhurong: New Rover on Mars
Image Credit: China National Space Administration

Explanation: There's a new rover on Mars. In mid-May, China's Tianwen-1 mission delivered the Zhurong rover onto the red planet. As Mars means Planet of Fire in Chinese, the Zhurong rover's name means, roughly, God of Fire in Chinese mythology. Zhurong landed in northern Utopia Planitia, the largest known impact basin in the Solar System, and an area reported to have much underground ice. Among many other scientific instruments, Zhurong carries ground-penetrating radar that can detect ice buried even 100-meters deep. Car-sized Zhurong is pictured here next to its landing base. The image was snapped by a remote camera deployed by the rolling rover. Zhurong's planned 90-day mission includes studying the geology, soil, and atmosphere of Mars in Utopia Planitia.