Astronomy Picture of the Day (APOD)

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Cartwheel of Fortune

Explanation: By chance, a collision of two galaxies has created a surprisingly recognizable shape on a cosmic scale, The Cartwheel Galaxy. The Cartwheel is part of a group of galaxies about 500 million light years away in the constellation Sculptor. Two smaller galaxies in the group are visible on the right. The Cartwheel Galaxy's rim is an immense ring-like structure 150,000 light years in diameter composed of newly formed, extremely bright, massive stars. When galaxies collide they pass through each other, their individual stars rarely coming into contact. Still, the galaxies' gravitational fields are seriously distorted by the collision. In fact, the ring-like shape is the result of the gravitational disruption caused by a small intruder galaxy passing through a large one, compressing the interstellar gas and dust and causing a a star formation wave to move out from the impact point like a ripple across the surface of a pond. In this case the large galaxy may have originally been a spiral, not unlike our own Milky Way, transformed into the wheel shape by the collision. But ... what happened to the small intruder galaxy?

Source: APOD, 2018 January 25

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Laguna Starry Sky

Explanation: Staring toward the heavens, one of the many lagunas in the Atacama Desert salt flat calmly reflects a starry night sky near San Pedro de Atacama, Chile, planet Earth. Cosmic rifts of dust, star clouds, and nebulae of the central Milky Way galaxy are rising in the east, beyond a volcanic horizon. Caught in the six frame panorama serenely recorded in the early morning hours of January 15, planets Jupiter and Mars are close. Near the ecliptic, the bright planets are immersed in the Solar System's visible band of Zodiacal light extending up and left from the galactic center. Above the horizon to the south (right) are the Large and Small clouds of Magellan, satellite galaxies of the Milky Way.  

Source: APOD, 2018 January 27

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Source: APOD, 2018 January 28

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Venus at Night in Infrared from Akatsuki

Explanation: Why is Venus so different from Earth? To help find out, Japan launched the robotic Akatsuki spacecraft which entered orbit around Venus late in 2015 after an unplanned five-year adventure around the inner Solar System. Even though Akatsuki was past its original planned lifetime, the spacecraft and instruments were operating so well that much of its original mission was reinstated. Also known as the Venus Climate Orbiter, Akatsuki's instruments investigated unknowns about Earth's sister planet, including whether volcanoes are still active, whether lightning occurs in the dense atmosphere, and why wind speeds greatly exceed the planet's rotation speed. In the featured image taken by Akatsuki's IR2 camera, Venus's night side shows a jagged-edged equatorial band of high dark clouds absorbing infrared light from hotter layers deeper in Venus' atmosphere. The bright orange and black stripe on the upper right is a false digital artifact that covers part of the much brighter day side of Venus. Analyses of Akatsuki images and data has shown that Venus has equatorial jet similar to Earth's jet stream.  

Source: APOD, 2018 January 30

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Moonset Eclipse



Source: APOD, 2018 February 01

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Moonrise Eclipse



Source: APOD, 2018 February 02

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Venus and the Triply Ultraviolet Sun

Explanation: An unusual type of solar eclipse occurred in 2012. Usually it is the Earth's Moon that eclipses the Sun. That year, most unusually, the planet Venus took a turn. Like a solar eclipse by the Moon, the phase of Venus became a continually thinner crescent as Venus became increasingly better aligned with the Sun. Eventually the alignment became perfect and the phase of Venus dropped to zero. The dark spot of Venus crossed our parent star. The situation could technically be labeled a Venusian annular eclipse with an extraordinarily large ring of fire. Pictured here during the occultation, the Sun was imaged in three colors of ultraviolet light by the Earth-orbiting Solar Dynamics Observatory, with the dark region toward the right corresponding to a coronal hole. Hours later, as Venus continued in its orbit, a slight crescent phase appeared again. The next Venusian transit across the Sun will occur in 2117.

Source: APOD, 2018 February 04

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NGC 7635: The Bubble Nebula Expanding



Source: APOD, 2018 February 05

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Galaxy NGC 474: Shells and Star Streams

Explanation: What's happening to galaxy NGC 474? The multiple layers of emission appear strangely complex and unexpected given the relatively featureless appearance of the elliptical galaxy in less deep images. The cause of the shells is currently unknown, but possibly tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years. Alternatively the shells may be like ripples in a pond, where the ongoing collision with the spiral galaxy just above NGC 474 is causing density waves to ripple through the galactic giant. Regardless of the actual cause, the featured image dramatically highlights the increasing consensus that at least some elliptical galaxies have formed in the recent past, and that the outer halos of most large galaxies are not really smooth but have complexities induced by frequent interactions with -- and accretions of -- smaller nearby galaxies. The halo of our own Milky Way Galaxy is one example of such unexpected complexity. NGC 474 spans about 250,000 light years and lies about 100 million light years distant toward the constellation of the Fish (Pisces).

Source: APOD, 2018 February 06

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NGC 7331 Close-Up



Source: APOD, 2018 February 07

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Total Solar Lunar Eclipse

Explanation: This digitally processed and composited picture creatively compares two famous eclipses in one; the total lunar eclipse (left) of January 31, and the total solar eclipse of August 21, 2017. The Moon appears near mid-totality in both the back-to-back total eclipses. In the lunar eclipse, its surface remains faintly illuminated in Earth's dark reddened shadow. But in the solar eclipse the Moon is in silhouette against the Sun's bright disk, where the otherwise dark lunar surface is just visible due to earthshine. Also seen in the lunar-aligned image pair are faint stars in the night sky surrounding the eclipsed Moon. Stunning details of prominences and coronal streamers surround the eclipsed Sun. The total phase of the Great American Eclipse of August 21 lasted about 2 minutes or less for locations along the Moon's shadow path. From planet Earth's night side, totality for the Super Blue Blood Moon of January 31 lasted well over an hour.

Source: APOD, 2018 February 09

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In the Heart of the Heart Nebula



Source: APOD, 2018 February 14

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Comet PanSTARRS is near the Edge

Explanation: The comet PanSTARRS, also known as the blue comet (C/2016 R2), really is near the lower left edge of this stunning, wide field view recorded on January 13. Spanning nearly 20 degrees on the sky, the cosmic landscape is explored by well-exposed and processed frames from a sensitive digital camera. It consists of colorful clouds and dusty dark nebulae otherwise too faint for your eye to see, though. At top right, the California Nebula (aka NGC 1499) does have a familiar shape. Its coastline is over 60 light-years long and lies some 1,500 light-years away. The nebula's pronounced reddish glow is from hydrogen atoms ionized by luminous blue star Xi Persei just below it. Near bottom center, the famous Pleiades star cluster is some 400 light-years distant and around 15 light-years across. Its spectacular blue color is due to the reflection of starlight by interstellar dust. In between are hot stars of the Perseus OB2 association and dusty, dark nebulae along the edge of the nearby, massive Taurus and Perseus molecular clouds. Emission from unusually abundant ionized carbon monoxide (CO+) molecules fluorescing in sunlight is largely responsible for the telltale blue tint of the remarkable comet's tail. The comet was about 17 light minutes from Earth. ?

Source: APOD, 2018 February 16

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Estimated first "legit" photo of a city and its lights on Proxima Centauri b, camera technology by CCP games.

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Estimated EM static echo between Columbia and Ecuador from wind power generation, was supposed to be a 5th category hurricane, local use of wind power seemed to turn it into that, seems a echo artifact of the war they had in the 1860's, locals treat it like a party float, have no problem approaching to within meters of its core. Nice pictures in series.

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Jupiter’s Swirling Cloud Formations



Source: NASA Image of the Day, 2018 February 16

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LL Ori and the Orion Nebula

Explanation: Stars can make waves in the Orion Nebula's sea of gas and dust. This esthetic close-up of cosmic clouds and stellar winds features LL Orionis, interacting with the Orion Nebula flow. Adrift in Orion's stellar nursery and still in its formative years, variable star LL Orionis produces a wind more energetic than the wind from our own middle-aged Sun. As the fast stellar wind runs into slow moving gas a shock front is formed, analogous to the bow wave of a boat moving through water or a plane traveling at supersonic speed. The small, arcing, graceful structure just above and left of center is LL Ori's cosmic bow shock, measuring about half a light-year across. The slower gas is flowing away from the Orion Nebula's hot central star cluster, the Trapezium, located off the upper left corner of the picture. In three dimensions, LL Ori's wrap-around shock front is shaped like a bowl that appears brightest when viewed along the "bottom" edge. This beautiful painting-like photograph is part of a large mosaic view of the complex stellar nursery in Orion, filled with a myriad of fluid shapes associated with star formation.

Source: APOD, 2018 February 18

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Galaxy Formation in a Magnetic Universe

Explanation: How did we get here? We know that we live on a planet orbiting a star orbiting a galaxy, but how did all of this form? To understand details better, astrophysicists upgraded the famous Illustris Simulation into IllustrisTNG -- now the most sophisticated computer model of how galaxies evolved in our universe. Specifically, this featured video tracks magnetic fields from the early universe (redshift 5) until today (redshift 0). Here blue represents relatively weak magnetic fields, while white depicts strong. These B fields are closely matched with galaxies and galaxy clusters. As the simulation begins, a virtual camera circles the virtual IllustrisTNG universe showing a young region -- 30-million light years across -- to be quite filamentary. Gravity causes galaxies to form and merge as the universe expands and evolves. At the end, the simulated IllustrisTNG universe is a good statistical match to our present real universe, although some interesting differences arise -- for example a discrepancy involving the power in radio waves emitted by rapidly moving charged particles.

Source: APOD, 2018 February 19

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When Roses Aren't Red

Explanation: Not all roses are red of course, but they can still be very pretty. Likewise, the beautiful Rosette Nebula and other star forming regions are often shown in astronomical images with a predominately red hue, in part because the dominant emission in the nebula is from hydrogen atoms. Hydrogen's strongest optical emission line, known as H-alpha, is in the red region of the spectrum, but the beauty of an emission nebula need not be appreciated in red light alone. Other atoms in the nebula are also excited by energetic starlight and produce narrow emission lines as well. In this gorgeous view of the Rosette Nebula, narrowband images are combined to show emission from sulfur atoms in red, hydrogen in blue, and oxygen in green. In fact, the scheme of mapping these narrow atomic emission lines into broader colors is adopted in many Hubble images of stellar nurseries. The image spans about 100 light-years in the constellation Monoceros, at the 3,000 light-year estimated distance of the Rosette Nebula. To make the Rosette red, just follow this link.

Source: APOD, 2018 February 22

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Facing NGC 6946



Source: APOD, 2018 February 24


AE Aurigae and the Flaming Star Nebula



Source: APOD, 2018 February 25

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Dueling Bands in the Night

Explanation: What are these two bands in the sky? The more commonly seen band is the one on the right and is the central band of our Milky Way galaxy. Our Sun orbits in the disk of this spiral galaxy, so that from inside, this disk appears as a band of comparable brightness all the way around the sky. The Milky Way band can also be seen all year -- if out away from city lights. The less commonly seem band, on the left, is zodiacal light -- sunlight reflected from dust orbiting the Sun in our Solar System. Zodiacal light is brightest near the Sun and so is best seen just before sunrise or just after sunset. On some evenings in the north, particularly during the months of March and April, this ribbon of zodiacal light can appear quite prominent after sunset. It has recently been determined that zodiacal dust was mostly expelled by comets that have passed near Jupiter. Only on certain times of the year will the two bands be seen side by side, in parts of the sky, like this. Here the two streaks of light appear like the continuation of the banks of the Liver River into the sky. The featured panorama of consecutive exposures was recorded about three weeks ago in North Jutland, Denmark.

Source: APOD, 2018 February 27

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Clouds, Birds, Moon, Venus



Source: APOD, 2018 March 04

The Hubble Ultra-Deep Field in Light and Sound (listen to the sounds at the APOD page directly)

Explanation: Have you heard about the Hubble Ultra-Deep Field? Either way, you've likely not heard about it like this -- please run your pointer over the featured image and listen! The Hubble Ultra-Deep Field (HUDF) was created in 2003-2004 with the Hubble Space Telescope staring for a long time toward near-empty space so that distant, faint galaxies would become visible. One of the most famous images in astronomy, the HUDF is featured here in a vibrant way -- with sonified distances. Pointing to a galaxy will play a note that indicates its approximate redshift. Because redshifts shift light toward the red end of the spectrum of light, they are depicted here by a shift of tone toward the low end of the spectrum of sound. The further the galaxy, the greater its cosmological redshift (even if it appears blue), and the lower the tone that will be played. The average galaxy in the HUDF is about 10.6 billion light years away and sounds like an F#. What's the most distant galaxy you can find? This Astronomy Picture of the Day (APOD) is based on an entry of new site called Astronomy Sound of the Month (AstroSoM).

Source: APOD, 2018 March 05

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Cyclones at Jupiter's North Pole



Source: APOD, 2018 March 08

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Horsehead: A Wider View



Source: APOD, 2018 March 09

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Dual Particle Beams in Herbig-Haro 24

Explanation: This might look like a double-bladed lightsaber, but these two cosmic jets actually beam outward from a newborn star in a galaxy near you. Constructed from Hubble Space Telescope image data, the stunning scene spans about half a light-year across Herbig-Haro 24 (HH 24), some 1,300 light-years away in the stellar nurseries of the Orion B molecular cloud complex. Hidden from direct view, HH 24's central protostar is surrounded by cold dust and gas flattened into a rotating accretion disk. As material from the disk falls toward the young stellar object it heats up. Opposing jets are blasted out along the system's rotation axis. Cutting through the region's interstellar matter, the narrow, energetic jets produce a series of glowing shock fronts along their path.

Source: APOD, 2018 March 11

Flying over the Earth at Night II

Source: APOD, 2018 March 12

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The Complete Galactic Plane: Up and Down

Explanation: Is it possible to capture the entire plane of our galaxy in a single image? Yes, but not in one exposure -- and it took some planning to do it in two. The top part of the featured image is the night sky above Lebanon, north of the equator, taken in 2017 June. The image was taken at a time when the central band of the Milky Way Galaxy passed directly overhead. The bottom half was similarly captured six months later in latitude-opposite Chile, south of Earth's equator. Each image therefore captured the night sky in exactly the opposite direction of the other, when fully half the Galactic plane was visible. The southern half was then inverted -- car and all -- and digitally appended to the top half to show the entire central band of our Galaxy, as a circle, in a single image. Many stars and nebulas are visible, with the Large Magellanic Cloud being particularly notable inside the lower half of the complete galactic circle.

Source: APOD, 2018 March 13

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The Crab from Space

Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, expanding debris from the death explosion of a massive star. This intriguing false-color image combines data from space-based observatories, Chandra, Hubble, and Spitzer, to explore the debris cloud in X-rays (blue-white), optical (purple), and infrared (pink) light. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is the bright spot near picture center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is 6,500 light-years away in the constellation Taurus.  

Source: APOD, 2018 March 17

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Going for Atmospheric GOLD

In late January 2018, NASA’s Global-scale Observations of the Limb and Disk (GOLD) instrument was launched into space aboard a commercial satellite. GOLD is novel in two ways: it marks the first time that a NASA science mission is flying an instrument as a commercially hosted payload, and it is the first time scientists will monitor the daily and hourly weather of the uppermost parts of Earth’s atmosphere where it meets the edge of space.

The instrument was launched on January 25 on an Ariane 5 rocket attached to SES-14, a communication satellite. On January 28, GOLD was briefly powered on to make sure it was working, then shut back down for the transit to orbit. The satellite and instrument are now moving toward their final position in a geostationary orbit. The mission is being led by the University of Central Florida.

Space is not completely empty: It is teeming with fast-moving, charged particles and with electric and magnetic fields that guide their motion. At the boundary between Earth’s atmosphere and space, the charged particles of the ionosphere co-exist with the upper reaches of the neutral atmosphere, or thermosphere. The two commingle and influence one another constantly. This interplay is the focus of the GOLD mission.

“The upper atmosphere is far more variable than previously imagined, but we don’t understand the interactions between all the factors involved,” said Richard Eastes, mission principal investigator at the University of Colorado. “That’s where GOLD comes in: For the first time, the mission gives us the big picture of how different drivers meet and influence each other.”

Source: NASA Earth Observatory Image of the Day, 2018 March 18

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Hubble’s Exquisite View of a Stellar Nursery

The exquisite sharpness of this 2005 image from NASA/ESA's Hubble Space Telescope has plucked out an underlying population of infant stars embedded in the nebula NGC 346 that are still forming from gravitationally collapsing gas clouds. They have not yet ignited their hydrogen fuel to sustain nuclear fusion. The smallest of these infant stars is only half the mass of our Sun.

Source: NASA Image of the Day, 2018 March 23