Tag Archives: NASA

M27 Not a Comet

While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his now famous not-a-comet list. In fact, 21st century astronomers would identify it as a planetary nebula, but it’s not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star’s outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star’s intense but invisible ultraviolet light. Known by the popular name of the Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the constellation Vulpecula. This spectacular color image incorporates broad and narrowband observations recorded by the 8.2 meter Subaru telescope. via NASA

Firefall by Moonlight

On certain dates in February, an elusive firefall can be spotted at sunset in Yosemite National Park, when the weather cooperates and the direction to the setting Sun is just right. Often photographed from vantage points below, at the right moment the park’s seasonal Horsetail Fall is isolated in the shadows of the steep walls of El Capitan but still illuminated with rays of sunlight reflected by the angled rockface directly behind the flow, briefly giving the waterfall a dramatic fiery appearance. The Horsetail firefall is more rarely photographed at moonset under a starry night sky, though. Even more elusive by moonlight, the firefall effect can also be seen when skies are clear and a bright Moon sets at the right direction along the western horizon. Skies were clear and stars were shining for this well-planned photograph of the Horsetail firefall lit by a gibbous Moon setting in the early morning hours of May 9. via NASA

The Case of the Missing Star

What’s happened to giant star N6946-BH1? It was there just a few years ago — Hubble imaged it. Now there’s only a faint glow. What’s curiouser, no bright supernova occurred — although the star did brightened significantly for a few months. The leading theory is that, at about 25 times the mass of our Sun, N6946-BH1’s great gravity held much of the star together during its final tumultuous death throes, after which most the star sunk into a black hole of its own making. If so, then what remained outside of the black hole likely then formed an accretion disk that emits comparatively faint infrared light as it swirls around, before falling in. If this mode of star death is confirmed with other stars, it gives direct evidence that a very massive star can end its life with a whimper rather than a bang. via NASA

Highlights of the Summer Sky

What’s up in the sky this summer? The featured graphic gives a few highlights for Earth’s northern hemisphere. Viewed as a clock face centered at the bottom, early summer sky events fan out toward the left, while late summer events are projected toward the right. Objects relatively close to Earth are illustrated, in general, as nearer to the cartoon figure with the telescope at the bottom center — although almost everything pictured can be seen without a telescope. Highlights of this summer’s sky include that Jupiter will be visible after sunset during June, while Saturn will be visible after sunset during August. A close grouping of the Moon, Venus and the bright star Aldebaran will occur during mid-July. In early August, the Perseids meteor shower peaks. Surely the most famous pending astronomical event occurring this summer, though, will be a total eclipse of the Sun visible over a thin cloud-free swath across the USA on 21 August. via NASA

Orion: Belt, Flame, and Horsehead

What surrounds the famous belt stars of Orion? A deep exposure shows everything from dark nebula to star clusters, all embedded in an extended patch of gaseous wisps in the greater Orion Molecular Cloud Complex. The brightest three stars, appearing diagonally on the left of the featured image are indeed the famous three stars that make up the belt of Orion. Just below Alnitak, the lowest of the three belt stars, is the Flame Nebula, glowing with excited hydrogen gas and immersed in filaments of dark brown dust. Just to the right of Alnitak lies the Horsehead Nebula, a dark indentation of dense dust that has perhaps the most recognized nebular shapes on the sky. The dark molecular cloud, roughly 1,500 light years distant, is cataloged as Barnard 33 and is seen primarily because it is backlit by the nearby massive star Sigma Orionis. The Horsehead Nebula will slowly shift its apparent shape over the next few million years and will eventually be destroyed by the high-energy starlight. via NASA

Perijove Passage

On May 19, the Juno spacecraft once again swung by Jupiter in its looping 53 day orbit around the Solar System’s ruling gas gaint. Beginning at the top, this vertical 14 frame sequence of enhanced-color JunoCam images follows the spacecraft’s rapidly changing perspective during its two hour passage. They look down on Jupiter’s north polar region, equatorial, and south polar region (bottom images). With the field-of-view shrinking, the seventh and eighth images in the sequence are close-up. Taken only 4 minutes apart above Jupiter’s equator they were captured just before the spacecraft reached perijove 6, its closest approach to Jupiter on this orbit. Final images in the sequence pick up white oval storm systems, Jupiter’s “String of Pearls”, and the south polar region from the outward bound spacecraft. via NASA

Black Holes of Known Mass

Add GW170104 to the chart of black holes with known mass. The extremely energetic merger of two smaller black holes corresponds to the Laser Interferometer Gravitational-wave Observatory’s (LIGO) third detection of gravitational waves. The newfound black hole has a mass about 49 times that of the Sun, filling a gap between the masses of the two merged black holes detected previously by LIGO, with solar masses of 62 (GW150914) and 21 (GW151216). In all three cases, the signal in each of the twin LIGO detectors was unambiguously identified as coming from black hole mergers while a fourth case (LVT151012) resulted in a lower confidence detection. GW170104 is estimated to be some 3 billion light-years away, more distant than present estimates for GW150914 and GW151216. The ripples in spacetime were discovered during LIGO’s current observing run, which began November 30, 2016 and will continue through the summer. via NASA

Beneath Jupiter

Jupiter is stranger than we knew. NASA’s Juno spacecraft has now completed its sixth swoop past Jupiter as it moves around its highly elliptical orbit. Pictured, Jupiter is seen from below where, surprisingly, the horizontal bands that cover most of the planet disappear into swirls and complex patterns. A line of white oval clouds is visible nearer to the equator. Recent results from Juno show that Jupiter’s weather phenomena can extend deep below its cloud tops, and that Jupiter’s magnetic field varies greatly with location. Juno is scheduled to orbit Jupiter 37 times with each orbit taking about six weeks. via NASA

Comet Clark is near the Edge.

Sweeping through this stunning field of view, Comet 71P/Clark really is in the foreground of these cosmic clouds. The 2 panel telescopic mosaic is color enhanced and is about 5 degrees (10 full moons) across. It captures the faint comet’s position on the night of May 23/24 over 5 light-minutes from Earth, very near the line-of-sight to bright star Antares and the Rho Ophiuchi cloud complex. In the frame Antares, also known as Alpha Scorpii, is at bottom center surrounded by a dusty cosmic cloud reflecting the cool giant star’s yellowish light. Globular star cluster M4 shines just right of Antares, but M4 lies some 7,000 light-years away compared to Antares’ 500 light-year distance. Slightly closer than Antares, Rho Ophiuchi’s bluish starlight is reflected by the dust in molecular clouds toward the top. You can spot the small coma and short tail of the comet as a faint smudge near the center of the left edge of the frame. Just look for the comet’s striking greenish color, produced as diatomic carbon molecules fluoresce in sunlight. via NASA

Spiral Galaxy NGC 6744

Big, beautiful spiral galaxy NGC 6744 is nearly 175,000 light-years across, larger than our own Milky Way. It lies some 30 million light-years distant in the southern constellation Pavo appearing as a faint, extended object in small telescopes. We see the disk of the nearby island universe tilted towards our line of sight. This remarkably distinct and detailed galaxy portrait covers an area about the angular size of the full moon. In it, the giant galaxy’s yellowish core is dominated by the light from old, cool stars. Beyond the core, spiral arms filled with young blue star clusters and pinkish star forming regions sweep past a smaller satellite galaxy at the lower left, reminiscent of the Milky Way’s satellite galaxy the Large Magellanic Cloud. via NASA