M97, also known as the Owl Nebula, is a famous planetary nebula located in the constellation of Ursa Major. It was discovered by Pierre Mechain on February 16, 1781 and is one of only four planetary nebulae listed in the Messier catalogue. Although not particularly bright at magnitude +9.9, it’s a superb object and regarded as one of the most complex examples of its type. The name Owl Nebula was first coined in 1848 by William Parsons the 3rd Earl of Rosse, who noticed owl-like “eyes”.
The ages of individual stars in the Milky Way can be estimated by measuring the abundance of long-lived radioactive elements such as thorium-232 and uranium-238, then comparing the results to estimates of their original abundance, a technique called nucleocosmochronology.Continue reading “nucleocosmochronology”
[Deneb]…it is estimated to be somewhere between 55,000 and 196,000 times as luminous as the Sun…’
Deneb is the brightest star in the constellation of Cygnus. It is one of the vertices of the asterism known as the Summer Triangle and forms the ‘head’ of the Northern Cross.
It is the 19th brightest star in the night sky, with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous stars.
However, its exact distance (and hence luminosity) has been difficult to calculate; it is estimated to be somewhere between 55,000 and 196,000 times as luminous as the Sun.
Finding the stars with the naked eye – astronomy starts by looking up at the sky without any optical prejudice.
Sagitta is a dim but distinctive constellation in the northern sky. Its name is Latin for “arrow”, and it should not be confused with the larger constellation Sagittarius, the archer. Although Sagitta is an ancient constellation, it has no star brighter than 3rd magnitude and has the third-smallest area of all constellations (only Equuleus and Crux are smaller). It was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations defined by the International Astronomical Union. Located to the north of the equator, Sagitta can be seen from every location on Earth except within the Antarctic circle.
Globular clusters are among the oldest objects in the Milky Way Galaxy, which thus set a lower limit on the age of the galaxy. Age estimates of the oldest of these clusters gives a best fit estimate of 12.6 billion years, and a 95% confidence upper limit of 16 billion years.
Galaxy does not suffer from crows feet in its selfie images ever.
The Milky Way began as one or several small overdensities in the mass distribution in the Universe shortly after the Big Bang. Some of these overdensities were the seeds of globular clusters in which the oldest remaining stars in what is now the Milky Way formed. These stars and clusters now comprise the stellar halo of the Galaxy.
Choose Dates Carefully
When to be psychic and or telepathic – and still get it wrong.
Orbital ATK’s robotic Cygnus cargo spacecraft is scheduled to launch toward the International Space Station (ISS) Tuesday atop a United Launch Alliance Atlas V rocket at 11:11 a.m. EDT (1511 GMT) from Florida’s Cape Canaveral Air Force Station. You can watch it live here at Space.com, courtesy of NASA TV, or directly at the space agency’s YouTube channel.
Cygnus has flown a number of such resupply runs in the past, but this liftoff will be special, from a viewer’s perspective at least: You’ll be able to get a pad’s-eye view, in 360 degrees.
“To view in 360, use a mouse or move a personal device to look up and down, back and forth, for a 360-degree view around Space Launch Complex-41 at Cape Canaveral Air Force Station, Florida,” NASA officials wrote in a statement. “Those who own virtual reality headsets will be able to look around and experience the view as if they were actually standing on the launch pad.”
The Cygnus is packed with more than 7,600 lbs. (3,450 kilograms) of scientific gear, hardware and supplies for the ISS crew — so much cargo that the mission will employ an Atlas V rather than Orbital’s own Antares booster, which is not quite as powerful. (An Antares is slated to loft the next Cygnus mission, which will lift off this summer.)
The marine iguana is an iguana found only on the Galápagos Islands that has the ability, unique among modern lizards, to forage in the sea, making it a marine reptile. The iguana can dive over 9 m (30 ft) into the water.
It has spread to all the islands in the archipelago, and is sometimes called the Galápagos marine iguana. It mainly lives on the rocky Galápagos shore to warm from the comparatively cold water, but can also be spotted in marshes and mangrove beaches.
Galapagos Marine Iguana
Marine iguanas are medium-sized lizards (200–340 mm (7.9–13.4 in), adult snout–vent length) and are unique as they are marine reptiles due to their foraging on inter-
and subtidal algae only. These iguanas forage exclusively in the cold sea, which leads them to behavioral adaptations for thermoregulation.
On his visit to the islands, despite making extensive observations on the creatures, Charles Darwin was revolted by the animals’ appearance, writing:
The black Lava rocks on the beach are frequented by large (2–3 ft [0.6–0.9 m]), disgusting clumsy Lizards. They are as black as the porous rocks over which they crawl
& seek their prey from the Sea. I call them ‘imps of darkness’. They assuredly well-become the land they inhabit.
Researchers theorize that land iguanas and marine iguanas evolved from a common ancestor since arriving on the islands from South America, presumably by rafting.
The marine iguana diverged from the land iguana some 8 million years ago, which is older than any of the extant Galapagos islands. It is therefore thought that the ancestral species inhabited parts of the volcanic archipelago that are now submerged.
The two species remain mutually fertile in spite of being assigned to distinct
genera, and they occasionally hybridize where their ranges overlap.
Although the marine iguana resembles a lizard, it has developed several adaptations that set it apart. These include blunt noses for efficiently grazing seaweed, powerful limbs and claws for climbing and holding onto rocks, and laterally flattened tails for improved swimming.
Compared to the land iguana its limb bones, especially those from the front limbs, have become more heavy and compact (osteosclerosis), providing ballast to help with diving.
The marine iguana has no evolved defences against introduced predators. These include rats, which tend to feed on the eggs, cats, which can feed on juveniles, and dogs
which may threaten adults.
Amblyrhynchus cristatus is not always black; the young have a lighter coloured dorsal stripe, and some adult specimens are grey, and adult males vary in colour with
the season. Dark tones allow the lizards to rapidly absorb heat to minimize the period of lethargy after emerging from the water. The marine iguana lacks agility on
land but is a graceful swimmer. Its laterally flattened tail and spiky dorsal fin aid in propulsion, while its long, sharp claws allow it to hold onto rocks in strong
currents.
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