Category Archives: Science

Behold: the curiously striped dunes of the Kunowsky crater – part of an image captured recently by the Mars Reconnaisance Orbiter’s HiRISE Camera.

But why do they look like that? No one knows. To wit:

Many Martian dunes are known to be covered unevenly with carbon dioxide (dry ice) frost, creating patterns of light and dark areas. Carbon dioxide doesn’t melt, but sublimates, turning directly into a gas. Carbon dioxide is also a greenhouse material even as a solid, so it can trap heat under the ice and sublimate from the bottom up, causing geyser-like eruptions. During Martian spring, these eruptions can cause a pattern of dark defrosting spots, where the darker sand is exposed. The featured image, though, was taken during Martian autumn, when the weather is getting colder – making these stripes particularly puzzling. One hypothesis is that they are caused by cracks in the ice that form from weaker eruptions or thermal stress as part of the day-night cycle, but research continues. Watching these dunes and others through more Martian seasons may give us more clues to solve this mystery.

(Image: HiRISE, MRO, LPL (U. Arizona), NASA; Processing: Włodek Głażewski; Text: Alex R. Howe (NASA/USRA, Reader’s History of SciFi Podcast)

apod

Behold: ghostly sprite lightning at 100,000 frames per second. But what is it?

Mysterious bursts of light in the sky that momentarily resemble gigantic jellyfish have been recorded for over 30 years, but apart from a general association with positive cloud-to-ground lightning, their root cause remains unknown. Some thunderstorms have them — most don’t. Recently, however, high speed videos are better detailing how sprites actually develop. The featured video, captured in mid-2019, is fast enough — at about 100,000 frames per second — to time-resolve several sprite “bombs” dropping and developing into the multi-pronged streamers that appear on still images. Unfortunately, the visual clues provided by videos like these do not fully resolve the sprite origins mystery. High speed vidoes do indicate to some researchers, though, that sprites are more likely to occur when plasma irregularities exist in the upper atmosphere.

(Video: Matthew G McHarg, Jacob L Harley, Thomas Ashcraft, Hans Nielsen)

Previously: No Sprite Is Safe

apod

Behold: the South Celestial Pole – the centre of all southern star trail arcs – one of two imaginary points in the sky where the Earth’s axis of rotation indefinitely extended, intersects the celestial sphere. To wit: 

In this starry panorama stretching about 60 degrees across deep southern skies the South Celestial Pole is somewhere near the middle though, flanked by bright galaxies and southern celestial gems. Across the top of the frame are the stars and nebulae along the plane of our own Milky Way Galaxy. Gamma Crucis, a yellowish giant star heads the Southern Cross near top center, with the dark expanse of the Coalsack nebula tucked under the cross arm on the left. Eta Carinae and the reddish glow of the Great Carina Nebula shine along the galactic plane near the right edge. At the bottom are the Large and Small Magellanic clouds, external galaxies in their own right and satellites of the mighty Milky Way. A line from Gamma Crucis through the blue star at the bottom of the southern cross, Alpha Crucis, points toward the South Celestial Pole, but where exactly is it? Just look for south pole star Sigma Octantis. Analog to Polaris the north pole star, Sigma Octantis is little over one degree fom the the South Celestial pole.

(Image: Petr Horalek, Josef Kujal)

apod

Behold: two gas giants passing in the night. What do you mean you missed it? To wit:

Two days ago Jupiter and Saturn passed a tenth of a degree from each other in what is known a Great Conjunction. Although the two planets pass each other on the sky every 20 years, this was the closest pass in nearly four centuries. Taken early in day of the Great Conjunction, the featured multiple-exposure combination captures not only both giant planets in a single frame, but also Jupiter’s four largest moons (left to right) Callisto, Ganymede, Io, and Europa — and Saturn’s largest moon Titan. If you look very closely, the clear Chilescope image even captures Jupiter’s Great Red Spot. The now-separating planets can still be seen remarkably close — within about a degree — as they set just after the Sun, toward the west, each night for the remainder of the year.

(Image: Damian Peach)

apod

Behold: Monty the space slug one of several dense, constantly eroding cosmic dust pillars in the Trifid Nebula (M20). To wit:

Visible in the featured picture is the end of a huge gas and dust pillar […] punctuated by a smaller pillar pointing up and an unusual jet pointing to the left. Many of the dots are newly formed low-mass stars. A star near the small pillar’s end is slowly being stripped of its accreting gas by radiation from a tremendously brighter star situated off the top of the image. The jet extends nearly a light-year and would not be visible without external illumination. As gas and dust evaporate from the pillars, the hidden stellar source of this jet will likely be uncovered, possibly over the next 20,000 years.

(Image: NASA, ESA, Hubble Space Telescope, HLA; Processing: Advait Mehla)

apod

Behold: the annual horizontal transit of the rising sun. To wit:

The featured image shows the direction of sunrise every month during 2019 as seen from near the city of Amman, Jordan. The camera in the image is always facing due east, with north toward the left and south toward the right. Although the Sun always rises in the east in general, it rises furthest to the south of east on the December solstice, and furthest north of east on the June solstice. Today is the December solstice, the day of least sunlight in the Northern Hemisphere and of most sunlight in the Southern Hemisphere. In many countries, the December Solstice is considered an official change in season: for example the first day of winter in the North. Solar heating and stored energy in the Earth’s surface and atmosphere are near their lowest during winter, making the winter months usually the coldest of the year. On the brighter side, in the north, daylight hours will now increase every day from until June.

(Image: Zaid M. Al-Abbadi)

apod

Behold: a spectacular 35 frame, hour-long exposure of the annual Gemenid meteor shower taken just after midnight last Sunday in the Italian Dolomites. To wit:

Sirius, alpha star of Canis Major and the brightest star in the night, is grazed by a meteor streak on the right. The Praesepe star cluster, also known as M44 or the Beehive cluster, itself contains about a thousand stars but appears as a smudge of light far above the southern alpine peaks near the top. The shower’s radiant is off the top of the frame though, near Castor and Pollux the twin stars of Gemini. The radiant effect is due to perspective as the parallel meteor tracks appear to converge in the distance. As Earth sweeps through the dust trail of asteroid 3200 Phaethon, the dust that creates Gemini’s meteors enters Earth’s atmosphere traveling at about 22 kilometres per second.

(Image: Stefano Pellegrini)

apod

Behold: the colliding galaxies of the Bullet Cluster, as you’ve never heard them before. To wit:

This massive cluster of galaxies (1E 0657-558) creates gravitational lens distortions of background galaxies in a way that has been interpreted as strong evidence for the leading theory: that dark matter exists within. Different analyses, though, indicate that a less popular alternative — modifying gravity– could explain cluster dynamics without dark matter, and provide a more likely progenitor scenario as well. Currently, the two scientific hypotheses are competing to explain the observations: it’s invisible matter versus amended gravity. The duel is dramatic as a clear Bullet-proof example of dark matter would shatter the simplicity of modified gravity theories. The featured sonified image is a Hubble/Chandra/Magellan composite with red depicting the X-rays emitted by hot gas, and blue depicting the suggested separated dark matter distribution. The sonification assigns low tones to dark matter, mid-range frequencies to visible light, and high tones to X-rays. The battle over the matter in the Bullet cluster is likely to continue as more observations, computer simulations, and analyses are completed.

(Image: X-ray: NASA/CXC/SAO; Optical: NASA/STScI, Magellan/U.Arizona; Lensing Map: NASA/STScI, ESO WFI, Magellan/U.Arizona; Sonification: NASA/CXC/SAO/K.Arcand, SYSTEM Sounds (M. Russo, A. Santaguida)

apod