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2009.06.15: Streaming Dark Nebulas near B44

Credit & Copyright: Thomas V. Davis (tvdavisastropix.com)

Dark dust lit by the bright yellow star Antares highlight this photogenic starscape of the southern sky. A wider angle image shows the central band of our Milky Way Galaxy connected to Antares by streams of dust knows as the Dark River. At the head of the Dark River the dust appears in dense knots. One of the densest knots is B44, pictured near the bottom of the above image. Off to the left of the above image lies Antares, a star so bright that the pictured dust reflects its light, giving it a distinct yellow hue. Light from the blue star on the image left creates a surrounding blue reflection nebula named IC 4605. B44 and IC 4605 lies about 500 light years distant toward the constellation of the Scorpion.

2009.06.16: Moonrise Over Turkey

Credit & Copyright: Tahir Sisman

Is the Moon larger when near the horizon? No — as shown above, the Moon appears to be very nearly the same size no matter its location on the sky. Oddly, the cause or causes for the common Moon Illusion are still being debated. Two leading explanations both hinge on the illusion that foreground objects make a horizon Moon seem farther in the distance. The historically most popular explanation then holds that the mind interprets more distant objects as wider, while a more recent explanation adds that the distance illusion may actually make the eye focus differently. Either way, the angular diameter of the Moon is always about 0.5 degrees. In the above time-lapse sequence of the Moon taken in 2007, with one exposure taken to bring up the foreground of Izmit Bay in Turkey. On the occasion of our 14th anniversary, the APOD editors thank all of our contributors and mirror site operators whose volunteer efforts help bring the wonders of astronomy to millions of people around the world. Additional thanks also go to our Turkish mirror site operators for submitting the above mouseover image.

2009.06.17: M13: A Great Globular Cluster of Stars

Credit & Copyright: Danny Lee Russell

M13 is one of the most prominent and best known globular clusters. Visible with binoculars in the constellation of Hercules, M13 is frequently one of the first objects found by curious sky gazers seeking celestials wonders beyond normal human vision. M13 is a colossal home to over 100,000 stars, spans over 150 light years across, lies over 20,000 light years distant, and is over 12 billion years old. At the 1974 dedication of Arecibo Observatory, a radio message about Earth was sent in the direction of M13. The reason for the low abundance of unusual blue straggler stars in M13 remains unknown.

2009.06.18: NGC 6240: Merging Galaxies

Credit: NASA / JPL-Caltech / STScI-ESA / S. Bush, et al. (Harvard-Smithsonian CfA)

NGC 6240 offers a rare glimpse of a cosmic catastrophe in its final throes. The titanic galaxy-galaxy collision is located a mere 400 million light-years away in the constellation Ophiuchus. One of the brightest sources in the infrared sky, the merging galaxies spew distorted tidal tails of stars, gas, and dust and undergo frantic bursts of star formation. The two supermassive black holes in the original galactic cores will also coalesce into a single, even more massive black hole. Soon, only one large galaxy will remain. This dramatic image of the scene is a multiwavelength composite; red colors trace infrared emission from dust recorded by the Spitzer Space Telescope, with Hubble visible light images of stars and gas in green and blue hues. The view spans over 300,000 light-years at the estimated distance of NGC 6240.

2009.06.19: Dunhuang Star Atlas

Credit and Copyright: J.-M. Bonnet-Bidaud (CEA, Saclay), F. Praderie (Obs. Paris) S. Whitfield (British Library)

This ancient Chinese map of planet Earth’s northern sky is part of the Dunhuang Star Atlas, one of the most impressive documents in the history of astronomy. The oldest complete star atlas known, it dates to the years 649 to 684, discovered at the Silk Road town of Dunhuang in 1907. A recent analysis that examines the accuracy and projections used to make it notes the atlas marks positions of over 1,300 stars and outlines 257 Chinese star groups or asterisms. The star positions in the hand drawn atlas were found to be accurate to within a few degrees. In this example showing the north polar region, a very recognizable Big Dipper, part of the modern constellation Ursa Major, lies along the bottom of the chart. An additional 12 charts depict equatorial regions in 30 degree sections and also include a grouping resembling the modern constellation Orion. The atlas is on display at the British Library in London to celebrate the International Year of Astronomy.

2009.06.20: Seaside Moon Mirage

Credit & Copyright: Jean-Marc Audrin

This surprising view of the Full Moon rising on June 7 was captured with a telephoto lens from a seaside balcony near Nice, France. The orange Moon’s dark markings and odd shape put the photographer in mind of an alien creature’s face staring down at the passing ship. Of course, the Moon’s distorted appearance is due to the unusual bending (refraction) of light rays creating multiple images or mirages, similar to sunset and sunrise mirages. The effects are most pronounced when temperature layers in the atmosphere produce sharp changes in air density and refractive index. Acting over long sight-lines to the rising and setting Sun or Moon, the refraction significantly alters the path of light rays creating merged, distorted images. Such mirages are also associated with the Green Flash.

2009.06.21: Sunrise over the Parthenon

Credit & Copyright: Anthony Ayiomamitis (TWAN)

Today, the sun will stay in the sky longer than any other day of the year, as seen from the northern hemisphere of Earth. Named the Summer Solstice, today’s maximum daylight is indicative of the high amount of sunlight this time of year that is primarily responsible for the heat of the summer season. At the north pole and for all places above the arctic circle, there will be no night — the entire day today will be lit by sunlight. The situation is reversed in Earth’s southern hemisphere, where today has the least sunlight of any day. Today’s solstice is commemorated above by a well-planned picture of our five billion year old Sun rising behind the 2,500 year old Parthenon in Greece. Trees and birds occupy the foreground, while a modern crane is shown restoring parts of this historic symbol of a cultural civilization.

2009.06.22: Atlas 5 Rocket Launches to the Moon

Credit: NASA

This rocket is headed for the Moon. Pictured above, a huge Altas V rocket roared off the launch pad last week to start NASA’s first missions to Earth’s Moon in 10 years. The rocket is carrying two robotic spacecraft. The Lunar Reconnaissance Orbiter (LRO) is scheduled to orbit and better map the Moon, search for buried and hidden ice, and return many high resolution images. Some images will be below one-meter in resolution and include images of historic Apollo landing sites. Exploratory data and images should allow a more informed choice of possible future astronaut landing sites. The Lunar CRater Observation and Sensing Satellite (LCROSS) is scheduled to monitor the controlled impact of the rocket’s upper stage into a permanently shadowed crater near the Moon’s south pole. This impact, which should occur in about three months, might be visible on Earth through small telescopes.

2009.06.16: Calliandra eriophylla

Plant Family / Families: Fabaceae
Scientific Name and Author: Calliandra eriophylla Benth.
Institution: University of California at Berkeley Botanical Garden
Name Location: Berkeley, California

Calliandra eriophylla, commonly known as fairy duster, is a low spreading shrub which is native to deserts and arid grasslands in California, Arizona, New Mexico and Texas and Mexico.

The flowers, which appear between late winter and late spring, have dense clusters of pale to deep pink stamens and are about 5 cm wide. The shrub is usually between 20 and 50 cm high and has bipinnate leaves.

Alternative common names for this species include Mock Mesquite and Mesquitella.

2009.06.17: Euphorbia griffithii ‘Fireglow’

Plant Family / Families: Euphorbiaceae
Scientific Name and Author: Euphorbia griffithii ‘Fireglow’ Hook. f.
Institution: UBC Botanical Garden
Name Location: Vancouver, British Columbia, Canada

Euphorbiaceae (the spurge family), which consists of around 300 genera and 7500 species, is native to both the temperate and tropical climate zones. Euphorbia griffithii is a metre-high herbaceous perennial that hails from the eastern Himalayas to the mountains of Myanmar (Burma) and western China. It ignites into bloom in early summer. The cultivar ‘Fireglow’, which is more deeply coloured than the species, welcomes visitors at the entrance to UBC Botanical Garden with a series of chromatic juxtapositions simultaneously subtle and strong: on its floral bracts, rich reds mix with searing yellows and oranges as if on the palette of an Old Master, while the dark burgundy of the stem and the green of the waxy leaves lend further contrast and contribute to the intensity of the blazing blooms above. This intensity culminates in the fall, when the floral apparatus turns brick red.

The vividness of the bloom, which to some suggests a measure of resilience and assertion, is indeed matched by the vigour with which ‘Fireglow’ confronts its surroundings. The species is robust enough to withstand both hostile pollutants and the vast spectrum of weather conditions associated with Zones 4 through 9; E. griffithii tends toward the invasive, however, at least in garden situations. Paraphrasing renowned gardener and garden writer Christopher Lloyd, the species is aggressive, and its sustained struggles when matched with a similarly dominant species leave the gardener only to referee. In addition to these somewhat bellicose tendencies, ‘Fireglow’ has another menacing trick up its sleeve. While the plant’s capacity to repel the onslaughts of deer and other animals is undoubtedly a benefit in the garden, gardeners beware, for the milky sap that fills the stems of this beautiful spurge is toxic.

For those wishing to explore the plants of the Himalayas, Laboritoire d’Ecologie Alpine has a searchable database, Flora Himalayan Database, which provides links to other Himalayan flora resources (Original French).

2009.06.18: Rodgersia sambucifolia

Plant Family / Families: Saxifragaceae
Scientific Name and Author: Rodgersia sambucifolia Hemsley
Institution: UBC Botanical Garden
Name Location: Vancouver, British Columbia, Canada

Rodgersia, a genus of five herbaceous perennial species from the moist valleys and forests of East Asia (Himalayas, China, Korea, and Japan), is known for its large, pinnately or palmately compound leaves, its spreading underground stems, and its sizable paniculate inflorescences (up to 2 m long), which are studded with numerous white or pink star-shaped flowers. The genus is named for the distinguished mid-19th Century United States Admiral John Rodgers, whose exploring and surveying expedition contributed significantly to early American knowledge of the eastern and northern waters of the Pacific Ocean and included the first scientific collection of a Rodgersia species.

The smallest and reportedly least hardy of the rodgersias, R. sambucifolia was first collected by British plant hunter Ernest Henry Wilson on his 1904 expedition to China. The species is native to the provinces of Guizhou, Sichuan, and Yunnan, but is not as well known as most other species. The specific epithet recalls Sambucus, the elderberry, which R. sambucifolia‘s elegant, deep green leaves resemble quite closely. The species, like all rodgersias, thrives in semi-shade and moist soil, looking well when sited near water. In June, R. sambucifolia‘s creamy blooms glow; do not wait to take in this refulgent drama, however, for the initial whites and pinks of June soon turn to weaker browns and greens. Fortunately, the handsome foliage more than makes up for any late floral indiscretion, and the plants continue to look fine through the summer with shade and moisture. In winter, the plants die back to the ground cleanly and completely. In the Vancouver area, the species is completely hardy (Zone 7), and a skiff of leaf-mould in the fall is all that the gardener needs in order to maintain a colony; the leaves both feed the plants and protect the ground from the pounding of the coming winter rain.

2009.06.19: Livistona chinensis

Plant Family / Families: Arecaceae
Scientific Name and Author: Livistona chinensis (Jacq.) R. Br. ex Mart.
Institution: South China Botanical Garden
Name Location: Guangzhou, Guangdong, China

In its native tropical, sub-tropical, and warm temperate habitats of coastal Asia (China, Taiwan, and southern Japan), Livistona chinensis—the Chinese fan palm—often reaches upwards of 15 metres (45 feet). At the trunk’s apex, the characteristically costapalmate (and scroll down here ) green leaves (which can grow to a diameter of 5 metres) collapse back toward the earth like layers of fountain water cascading softly downward from the peak of their trajectory. For this reason, many happily refer to the species as the fountain palm, and just as the figure of its namesake evokes a sense of sweet respite and replenishment, the species itself produces raw materials for human nourishment and raiment, and it forms a cool canopy through which only cracks of sunlight can penetrate. While it does indeed provide humans and animals with a measure of protection from the heat of the tropical sun, L. chinensis guards itself against the baleful consequences of drought by way of a long tap root that generally extends to the cool, moist depths of 2 metres. Of course, today the palm is a popular domestic and commercial plant that rarely confronts the adverse soil and climate conditions against which it is so hardy: in the warmer parts of North America, it is generally sited in shopping mall pots and alongside manicured highways or caring homes.

Botanical gardens contain multitudes in several senses: beyond the heterogeneity of visible and invisible life forms that inhabit or make use of this land, that is, the garden is by nature home to a broad spectrum of mood and ambience. Odd moments find one immersed in a tour group or a research party, while others are steeped in the tranquility and solitude of an isolated corner or an often overlooked path. Though it was taken in the South China Botanical Garden, which, as a rule, hums with the frantic energy of practical human endeavor and association, this photo seems to suggest the latter form of experience—of leaving the heat, light, and din of the highway and the beaten path behind for the serene terrain of whispers, shadows, and the unexpected.

2009.06.20: Elaeocarpus hainanensis

Plant Family / Families: Elaeocarpaceae
Scientific Name and Author: Elaeocarpus hainanensis Oliver
Institution: South China Botanical Garden
Name Location: Guangzhou, Guangdong, China

Douglas Justice:

As a person fascinated with plants of all kinds—though admittedly, I’m more familiar with temperate plants—I couldn’t help but be impressed with the range of tropical and subtropical plants at the South China Botanical Garden, where I attended the Second International Magnolia Symposium this past May. I should confess, too, that woody plants, especially trees, are my great passion. Leaving magnolias aside, one of the most beautiful groups I saw in the garden was the Elaeocarpus collection. The tree pictured is about 5 m tall and about as wide. Each and every branch was festooned with sweetly scented cream and white flowers. The overall effect of the fringed blooms against the glossy, deep green leaves was exceptionally beautiful. In all, I saw some five distinct species, though there were probably many more in the collection.

The name hainanensis indicates that this species is found on Hainan Island, off the south coast of China (it also occurs on the adjacent mainland and in Indochina). Although unlabeled, the species resembled other trees of E. hainanensis, so this is the name I’ve provisionally given to it; as there are about 350 species in the genus, however, I’m just as likely to be wrong about the identification. I strongly suspect that many species are grown as ornamentals because of their clean, evergreen foliage and their great beauty when in flower.

2009.06.22: Eremurus x isabellinus

Plant Family / Families: Asphodelaceae
Scientific Name and Author: Eremurus x isabellinus P. L. Vilm.
Institution: UBC Botanical Garden
Name Location: Vancouver, British Columbia, Canada

Pictured are two Eremurus × isabellinus hybrids: first, dressed in peach-coloured flowers, ‘Cleopatra’; second, an unknown yellow-flowered cultivar, probably ‘Image’, which only arose this year (in the second year) from amongst the stems of ‘Cleopatra’. There are several group names for hybrid foxtail lilies, each referring to a particular place or breeder. For example, the best-known is the Shelford hybrid strain of foxtail lilies, developed by Sir Michael Foster (1836-1907) of Great Shelford, Cambridge, England. Foster was an eminent professor of physiology at Cambridge University, and he served as Secretary of the Royal Society as well. He was perhaps best known as an iris collector, and is remembered for his suggestion that, „horticulture is a pious occupation,“ substantiating his claim with the assertion that, „the gods rejoice when they see a good man struggling with adversity“. Foster was among the first to receive the Victoria Medal of Honour from the RHS. In the popular literature, Eremurus × isabellinus hybrids are known as Shelford Hybrids—often even listed as E. × shelfordii—but ‘Cleopatra’ is actually a Highdown Hybrid, and ‘Image’ belongs to an increasingly popular group called the Ruiter Hybrids. Unfortunately, I couldn’t find any substantial historical information on either of these two hybrid groups.

Foxtail lilies are challenging subjects, especially in Vancouver’s wet winter climate. Their octopus-like, sprawling, fleshy rhizomes require perfect drainage, and the plants need maximum sun exposure to flower well; nevertheless, the hybrids are somewhat easier both to establish and to maintain than the wild species. I once heard the renowned gardener (and garden writer) Christopher Lloyd describe his method for cultivating foxtail lilies. He would dig a large hole in a well-drained, sunny spot, and pour builder’s sand into the hole so that it would form a cone (the top of which was approximately 10 to 15 cm below the ground level); he would then lay the rhizome over the cone and backfill with the native garden soil. This would position the crown and arms of the rhizome appropriately and ensure that the rot-vulnerable underside of the rhizome would stay dry. Today’s photograph was taken in the plaza at the entrance to the Botanical Garden. The soil here is relatively sandy, infertile and well-drained. The spring-flowering Koelreuteria paniculata (golden rain tree)—which prefers similar dry, sunny conditions—provides the background.

Parašė DarkSkyGhost, 2009 06 23, 11:57
Kategorijos: Dienos vaizdai, Gamta, Visata | Žymos: APOD, Augalai, BPOD, Visata
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