What spooky planet is this? Planet Earth of course, on a dark and stormy night in 2013 at Hverir, a geothermally active area along the volcanic landscape in northeastern Iceland. Geomagnetic storms produced the auroral display in the starry night sky while ghostly towers of steam and gas venting from fumaroles danced against the eerie greenish light. Tonight, there is also a chance for geomagnetic storms triggered by recent solar activity, so high-latitude skygazers should beware. Ghostly shapes may dance in your neighborhood pretty soon, too.
Wraithlike NGC 6369 is a faint apparition in night skies popularly known as the Little Ghost Nebula. It was discovered by 18th century astronomer Sir William Herschel as he used a telescope to explore the medicinal constellation Ophiucus. Herschel historically classified the round and planet-shaped nebula as a Planetary Nebula. But planetary nebulae in general are not at all related to planets. Instead they are gaseous shrouds created at the end of a sun-like star’s life, the dying star’s outer layers expanding into space while its core shrinks to become a white dwarf. The transformed white dwarf star, seen near the center, radiates strongly at ultraviolet wavelengths and powers the expanding nebula’s glow. Surprisingly complex details and structures of NGC 6369 are revealed in this tantalizing image composed from Hubble Space Telescope data. The nebula’s main round structure is about a light-year across and the glow from ionized oxygen, hydrogen, and nitrogen atoms are colored blue, green, and red respectively. Over 2,000 light-years away, the Little Ghost Nebula offers a glimpse of the fate of our Sun, which could produce its own planetary nebula about 5 billion years from now.
As far as ghosts go, Mirach’s Ghost isn’t really that scary. Mirach’s Ghost is just a faint, fuzzy galaxy, well known to astronomers, that happens to be seen nearly along the line-of-sight to Mirach, a bright star. Centered in this star field, Mirach is also called Beta Andromedae. About 200 light-years distant, Mirach is a red giant star, cooler than the Sun but much larger and so intrinsically much brighter than our parent star. In most telescopic views, glare and diffraction spikes tend to hide things that lie near Mirach and make the faint, fuzzy galaxy look like a ghostly internal reflection of the almost overwhelming starlight. Still, appearing in this sharp image just above and to the left of Mirach, Mirach’s Ghost is cataloged as galaxy NGC 404 and is estimated to be some 10 million light-years away.
Adrift in a cosmic sea of stars and glowing gas the delicate, floating apparition left of center in this widefield view is cataloged as NGC 7635, the Bubble Nebula. A mere 10 light-years wide, the tiny Bubble Nebula was blown by the winds of a massive star. It lies within a larger complex of interstellar gas and dust clouds found about 11,000 light-years distant, straddling the boundary between the parental constellations Cepheus and Cassiopeia. Included in the breathtaking vista is open star cluster M52 (lower left), some 5,000 light-years away. Above and right of the Bubble Nebula is an emission region identified as Sh2-157, also known as the Claw Nebula. Constructed from 47 hours of narrow-band and broad-band exposures, this image spans about 3 degrees on the sky. That corresponds to a width of 500 light-years at the estimated distance of the Bubble Nebula.
Could humans live beneath the surface of the Moon? This intriguing possibility was bolstered in 2009 when Japan’s Moon-orbiting SELENE spacecraft imaged a curious hole beneath the Marius Hills region on the Moon, possibly a skylight to an underground lava tube. Follow-up observations by NASA’s Lunar Reconnaissance Orbiter (LRO) indicated that the Marius Hills Hole (MHH) visually extends down nearly 100 meters and is several hundred meters wide. Most recently, ground penetrating radar data from SELENE has been re-analyzed to reveal a series of intriguing second echoes — indicators that the extensive lava tubes exist under Marius Hills might extend down even kilometers and be large enough to house cities. Such tubes could shelter a future Moon colony from large temperature swings, micro-meteor impacts, and harmful solar radiation. Potentially, underground lava tubes might even be sealed to contain breathable air. These lava tubes likely formed when lunar volcanos were active billions of years ago. Pictured, the surface of Marius Hills region was captured in the 1960s by NASA’s Lunar Orbiter 2 mission, while an inset image of the MHH is shown from NASA’s continuing LRO. Several volcanic domes are visible, while Marius Crater is visible on the upper right.
The hydrogen in your body, present in every molecule of water, came from the Big Bang. There are no other appreciable sources of hydrogen in the universe. The carbon in your body was made by nuclear fusion in the interior of stars, as was the oxygen. Much of the iron in your body was made during supernovas of stars that occurred long ago and far away. The gold in your jewelry was likely made from neutron stars during collisions that may have been visible as short-duration gamma-ray bursts or gravitational wave events. Elements like phosphorus and copper are present in our bodies in only small amounts but are essential to the functioning of all known life. The featured periodic table is color coded to indicate humanity‘s best guess as to the nuclear origin of all known elements. The sites of nuclear creation of some elements, such as copper, are not really well known and are continuing topics of observational and computational research.
What’s happening at the center of active galaxy 3C 75? The two bright sources at the center of this composite x-ray (blue)/ radio (pink) image are co-orbiting supermassive black holes powering the giant radio source 3C 75. Surrounded by multimillion degree x-ray emitting gas, and blasting out jets of relativistic particles the supermassive black holes are separated by 25,000 light-years. At the cores of two merging galaxies in the Abell 400 galaxy cluster they are some 300 million light-years away. Astronomers conclude that these two supermassive black holes are bound together by gravity in a binary system in part because the jets’ consistent swept back appearance is most likely due to their common motion as they speed through the hot cluster gas at 1200 kilometers per second. Such spectacular cosmic mergers are thought to be common in crowded galaxy cluster environments in the distant universe. In their final stages the mergers are expected to be intense sources of gravitational waves.