The Tarantula Zone
The Tarantula Nebula, also known as 30 Doradus, is more than a thousand light-years in diameter, a giant star forming region within nearby satellite galaxy the Large Magellanic Cloud. About 180 thousand light-years away, it's the largest, most violent star forming region known in the whole Local Group of galaxies. The cosmic arachnid sprawls across this magnificent view, an assembly of image data from large space- and ground-based telescopes. Within the Tarantula (NGC 2070), intense radiation, stellar winds, and supernova shocks from the central young cluster of massive stars cataloged as R136 energize the nebular glow and shape the spidery filaments. Around the Tarantula are other star forming regions with young star clusters, filaments, and blown-out bubble-shaped clouds. In fact, the frame includes the site of the closest supernova in modern times, SN 1987A, at lower right. The rich field of view spans about 2 degrees or 4 full moons in the southern constellation Dorado. But were the Tarantula Nebula closer, say 1,500 light-years distant like the Milky Way's own star forming Orion Nebula, it would take up half the sky.
The Crew-8 Nebula
Not the James Webb Space Telescope's latest view of a distant galactic nebula, this cloud of gas and dust dazzled spacecoast skygazers on March 3. The telephoto snapshot was taken minutes after the launch of a Falcon 9 rocket on the SpaceX Crew-8 mission, to the International Space Station. It captures plumes and exhaust from the separated first and second stage, a drifting Rorschach pattern in dark evening skies. The bright spot near bottom center within the stunning terrestrial nebulosity is the second stage engine firing to carry 4 humans to space in the Crew Dragon spacecraft Endeavour. In sharp silhouette just above it is the Falcon 9 first stage booster orienting itself for return to a landing zone at Cape Canaveral, planet Earth. This reuseable first stage booster was making its first flight. But the Crew Dragon Endeavour capsule has flown humans to low Earth orbit and back again 4 times before. Endeavour, as a name for a spacecraft, has also seen reuse, christening retired Space Shuttle Endeavour and the Apollo 15 command module.
M102: Edge-on Disk Galaxy
What kind of celestial object is this? A relatively normal galaxy -- but seen from its edge. Many disk galaxies are actually just as thin as NGC 5866, the Spindle galaxy, pictured here, but are not seen edge-on from our vantage point. A perhaps more familiar galaxy seen edge-on is our own Milky Way galaxy. Also cataloged as M102, the Spindle galaxy has numerous and complex dust lanes appearing dark and red, while many of the bright stars in the disk give it a more blue underlying hue. The blue disk of young stars can be seen in this Hubble image extending past the dust in the extremely thin galactic plane. There is evidence that the Spindle galaxy has cannibalized smaller galaxies over the past billion years or so, including multiple streams of faint stars, dark dust that extends away from the main galactic plane, and a surrounding group of galaxies (not shown). In general, many disk galaxies become thin because the gas that forms them collides with itself as it rotates about the gravitational center. The Spindle galaxy lies about 50 million light years distant toward the constellation of the Dragon (Draco).
NGC 2170: Angel Nebula Abstract Art
Is this a painting or a photograph? In this celestial abstract art composed with a cosmic brush, dusty nebula NGC 2170, also known as the Angel Nebula, shines just above the image center. Reflecting the light of nearby hot stars, NGC 2170 is joined by other bluish reflection nebulae, a red emission region, many dark absorption nebulae, and a backdrop of colorful stars. Like the common household items that abstract painters often choose for their subjects, the clouds of gas, dust, and hot stars featured here are also commonly found in a setting like this one -- a massive, star-forming molecular cloud in the constellation of the Unicorn (Monoceros). The giant molecular cloud, Mon R2, is impressively close, estimated to be only 2,400 light-years or so away. At that distance, this canvas would be over 60 light-years across.
Light Pillars Over Inner Mongolia
What's happening across that field? Pictured here are not auroras but nearby light pillars, a phenomenon typically much closer. In most places on Earth, a lucky viewer can see a Sun pillar, a column of light appearing to extend up from the Sun caused by flat fluttering ice-crystals reflecting sunlight from the upper atmosphere. Usually, these ice crystals evaporate before reaching the ground. During freezing temperatures, however, flat fluttering ice crystals may form near the ground in a form of light snow sometimes known as a crystal fog. These ice crystals may then reflect ground lights in columns not unlike a Sun pillar. The featured image was taken last month across the Wulan Butong Grasslands in Inner Mongolia, China.
Odysseus on the Moon
Methalox rocket engine firing, Odysseus' landing legs absorb first contact with the lunar surface in this wide-angle snapshot from a camera on board the robotic Intuitive Machines Nova-C moon lander. Following the landing on February 22, broken landing legs, visible in the image, ultimately left the lander at rest but tilted. Odysseus' gentle lean into a sloping lunar surface preserved the phone booth-sized lander's ability to operate, collect solar power, and return images and data to Earth. Its exact landing site in the Moon's far south polar region was imaged by NASA's Lunar Reconnaissance Orbiter. Donated by NASA, the American flag seen on the lander's central panel is 1970 Apollo program flight hardware.
Julius Caesar and Leap Days
In 46 BC Julius Caesar reformed the calendar system. Based on advice by astronomer Sosigenes of Alexandria, the Julian calendar included one leap day every four years to account for the fact that an Earth year is slightly more than 365 days long. In modern terms, the time it takes for the planet to orbit the Sun once is 365.24219 mean solar days. So if calendar years contained exactly 365 days they would drift from the Earth's year by about 1 day every 4 years and eventually July (named for Julius Caesar himself) would occur during the northern hemisphere winter. By adopting a leap year with an extra day every four years, the Julian calendar year would drift much less. In 1582 Pope Gregory XIII provided the further fine-tuning that leap days should not occur in years ending in 00, unless divisible by 400. This Gregorian Calendar system is the one in wide use today. Of course, tidal friction in the Earth-Moon system slows Earth's rotation and gradually lengthens the day by about 1.4 milliseconds per century. That means that leap days like today will not be necessary, about 4 million years from now. This Roman silver coin, a denarius, depicts Julius Caesar (left) and Venus, Roman goddess of love.
Shades of Night
How does the sky turn dark at night? In stages, and with different characteristic colors rising from the horizon. The featured image shows, left to right, increasingly late twilight times after sunset in 20 different vertical bands. The picture was taken last month in Syracuse, Sicily, Italy, in the direction opposite the Sun. On the far left is the pre-sunset upper sky. Toward the right, prominent bands include the Belt of Venus, the Blue Band, the Horizon Band, and the Red Band. As the dark shadow of the Earth rises, the colors in these bands are caused by direct sunlight reflecting from air and aerosols in the Earth's atmosphere, multiple reflections sometimes involving a reddened sunset, and refraction. In practice, these bands can be diffuse and hard to discern, and their colors can depend on colors near the setting Sun. Finally, the Sun completely sets and the sky becomes dark. Don't despair -- the whole thing will happen in reverse when the Sun rises again in the morning.
Supernova Remnant Simeis 147
It's easy to get lost following the intricate, looping, and twisting filaments of supernova remnant Simeis 147. Also cataloged as Sharpless 2-240, the filamentary nebula goes by the popular nickname the Spaghetti Nebula. Seen toward the boundary of the constellations of the Bull (Taurus) and the Charioteer (Auriga), the impressive gas structure covers nearly 3 degrees on the sky, equivalent to 6 full moons. That's about 150 light-years at the stellar debris cloud's estimated distance of 3,000 light-years. This composite image includes data taken through narrow-band filters isolating emission from hydrogen (red) and oxygen (blue) glowing gas. The supernova remnant has an estimated age of about 40,000 years, meaning light from this massive stellar explosion first reached the Earth when woolly mammoths roamed free. Besides the expanding remnant, this cosmic catastrophe left behind a pulsar: a spinning neutron star that is the remnant of the original star's core.
A Phoenix Aurora over Iceland
All of the other aurora watchers had gone home. By 3:30 am in Iceland, on a quiet September night, much of that night's auroras had died down. Suddenly, unexpectedly, a new burst of particles streamed down from space, lighting up the Earth's atmosphere once again. This time, surprisingly, pareidoliacally, the night lit up with an amazing shape reminiscent of a giant phoenix. With camera equipment at the ready, two quick sky images were taken, followed immediately by a third of the land. The mountain in the background is Helgafell, while the small foreground river is called Kaldá, both located about 30 kilometers north of Iceland's capital Reykjavík. Seasoned skywatchers will note that just above the mountain, toward the left, is the constellation of Orion, while the Pleiades star cluster is also visible just above the frame center. The 2016 aurora, which lasted only a minute and was soon gone forever -- would possibly be dismissed as a fanciful fable -- were it not captured in the featured, digitally-composed, image mosaic.
The Pencil Nebula Supernova Shock Wave
This supernova shock wave plows through interstellar space at over 500,000 kilometers per hour. Centered and moving upward in the sharply detailed color composite its thin, bright, braided filaments are actually long ripples in a cosmic sheet of glowing gas seen almost edge-on. Discovered in the 1840s by Sir John Herschel, the narrow-looking nebula is sometimes known as Herschel's Ray. Cataloged as NGC 2736, its pointed appearance suggests its modern popular name, the Pencil Nebula. The Pencil Nebula is about 800 light-years away. Nearly 5 light-years long it represents only a small part of the Vela supernova remnant though. The enormous Vela remnant itself is around 100 light-years in diameter, the expanding debris cloud of a star that was seen to explode about 11,000 years ago. Initially, the section of the shock wave seen as the Pencil nebula was moving at millions of kilometers per hour but has slowed considerably, sweeping up surrounding interstellar material.
A View Toward M106
Big, bright, beautiful spiral, Messier 106 dominates this cosmic vista. The nearly two degree wide telescopic field of view looks toward the well-trained constellation Canes Venatici, near the handle of the Big Dipper. Also known as NGC 4258, M106 is about 80,000 light-years across and 23.5 million light-years away, the largest member of the Canes II galaxy group. For a far far away galaxy, the distance to M106 is well-known in part because it can be directly measured by tracking this galaxy's remarkable maser, or microwave laser emission. Very rare but naturally occurring, the maser emission is produced by water molecules in molecular clouds orbiting its active galactic nucleus. Another prominent spiral galaxy on the scene, viewed nearly edge-on, is NGC 4217 below and right of M106. The distance to NGC 4217 is much less well-known, estimated to be about 60 million light-years, but the bright spiky stars are in the foreground, well inside our own Milky Way galaxy.
Seagull Nebula over Pinnacles' Peak
The bird is bigger than the peak. Nicknamed for its avian shape, the Seagull Nebula is an emission nebula on the night sky that is vast, spanning an angle over five times the diameter of the full moon and over 200 light years. The head of the nebula is catalogued as IC 2177, and the star cluster under its right wing is catalogued as NGC 2343. Consisting of mostly red-glowing hydrogen gas, the Seagull Nebula incorporates some dust lanes and is forming stars. The peak over which this Seagull seems to soar occurs at Pinnacles National Park in California, USA. The featured image is a composite of long exposure images of the background sky and short exposure images of the foreground, all taken consecutively with the same camera and from the same location.
Hoag's Object: A Nearly Perfect Ring Galaxy
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 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.
Meteor over the Bay of Naples
A cosmic dust grain plowing through the upper atmosphere much faster than a falling leaf created this brilliant meteor streak. In a serendipitous moment, the sublime night sky view was captured from the resort island of Capri, in the Bay of Naples, on the evening of February 8. Looking across the bay, the camera faces northeast toward the lights of Naples and surrounding cities. Pointing toward the horizon, the meteor streak by chance ends above the silhouette of Mount Vesuvius. One of planet Earth's most famous volcanos, an eruption of Mount Vesuvius destroyed the city of Pompeii in 79 AD.
