This sky looked delicious. Double auroral ovals were captured above the town
lights of Östersund, Sweden, last week. Pictured above, the green ovals
occurred lower to the ground than violet aurora rays above, making the whole
display look a bit like a cupcake. To top it off, far in the distance, the
central band or our Milky Way Galaxy slants down from the upper left. The
auroras were caused by our Sun ejecting plasma clouds into the Solar System
just a few days before, ionized particles that subsequently impacted the
magnetosphere of the Earth. Aurora displays may continue this week as an active
sunspot group rotated into view just a few days ago.
در تاریخ سیاره ی زمین ، گونه ی انسان دیر ، - بسیار دیر- پدید آمد؛ اما در همین زمان کوتاهی که بر روی زمین بوده است ، " دست آدمی" ، تغییرات ژرفی در هوا، در آب و خاک ، در دیگر موجودات زنده و در همه ی نظامی که بخش های گونه گون آن در پیوند بهم فشرده با یکدیگر ، بر هم کنش دارند و محیط زندگی او را می سازند، پدید آورده است . همه ی این ها در آخرین لحظه ی " زمان زمین شناسی " ، روی داده است .
۱۳۹۳ مهر ۲۰, یکشنبه
Laniakea: Our Home Supercluster of Galaxies
It is not only one of the largest structures known -- it is our home. The
just-identified Laniakea Supercluster of galaxies contains thousands of
galaxies that includes our Milky Way Galaxy, the Local Group of galaxies, and
the entire nearby Virgo Cluster of Galaxies. The colossal supercluster is shown
in the above computer-generated visualization, where green areas are rich with
white-dot galaxies and white lines indicate motion towards the supercluster
center. An outline of Laniakea is given in orange, while the blue dot shows our
location. Outside the orange line, galaxies flow into other galatic
concentrations. The Laniakea Supercluster spans about 500 million light years
and contains about 100,000 times the mass of our Milky Way Galaxy. The
discoverers of Laniakea gave it a name that means "immense heaven" in
Hawaiian.
, Salar de Atacama
The photo above showing the largest salt flat in
Chile, Salar de Atacama, was taken 34 mi (55 km) south of San Pedro de Atacama,
on April 13, 2009. Salar de Atacama is the largest source of lithium active in
the world today and is the lightest elemental metal in the periodic table.
Lithium is used in the production of batteries as well as in soldering and for
lubrication. At the horizon, the Licancabur volcano (19,400 ft or 5,913 m) can
be seen
Two-Armed Spiral Milky Way
Explanation: Gazing out from within the Milky Way,
our own galaxy's true structure is difficult to discern. But an ambitious
survey effort with the Spitzer Space Telescope now offers convincing evidence
that we live in a large galaxy distinguished by two main spiral arms (the
Scutum-Centaurus and Perseus arms) emerging from the ends of a large central
bar. In fact, from a vantage point that viewed our galaxy face-on, astronomers
in distant galaxies would likely see the Milky Way as a two-armed barred spiral
similar to this artist's illustration. Previous investigations have identified
a smaller central barred structure and four spiral arms. Astronomers still
place the Sun about a third of the way in from the Milky Way's outer edge, in a
minor arm called the Orion Spur. To locate the Sun and identify the Milky Way's
newly mapped features, just place your cursor over the image
Aurora over Maine
Explanation:
It has been a good week for auroras. Earlier this month active sunspot region
2158 rotated into view and unleashed a series of flares and plasma ejections
into the Solar System during its journey across the Sun's disk. In particular,
a pair of Coronal Mass Ejections (CMEs) impacted the Earth's magnetosphere
toward the end of last week, creating the most intense geomagnetic storm so far
this year. Although power outages were feared by some, the most dramatic
effects of these impacting plasma clouds were auroras seen as far south as
Wisconsin, USA. In the featured image taken last Friday night, rays and sheets
of multicolored auroras were captured over Acadia National Park, in Maine, USA.
Since another CME plasma cloud is currently approaching the Earth, tonight
offers another good chance to see an impressive auroral display.
largest volcanoes.
This map shows the
locations of the world's largest volcanoes. Tamu Massif on the Shatsky Rise in
the northwest Pacific Ocean has the greatest mass and the largest footprint.
Mauna Kea on the island of Hawaii has the greatest height from base to summit.
Ojos del Salado in the Andes mountain range on the border between Argentina and
Chile has the highest summit elevation.
World of Change
In
the 1960s, the Soviet Union undertook a major water diversion project on the
arid plains of Kazakhstan, Uzbekistan, and Turkmenistan. The region’s two major
rivers, fed by snowmelt and precipitation in faraway mountains, were used to
transform the desert into farms for cotton and other crops. Before the project,
the Syr Darya and the Amu Darya rivers flowed down from the mountains, cut
northwest through the Kyzylkum Desert, and finally pooled together in the
lowest part of the basin. The lake they made, the Aral Sea, was once the fourth
largest in the world.
Although
irrigation made the desert bloom, it devastated the Aral Sea. This series of
images from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s
Terra satellite documents the changes. At the start of the series in 2000, the
lake was already a fraction of its 1960 extent (black line). The Northern Aral
Sea (sometimes called the Small Aral Sea) had separated from the Southern (Large)
Aral Sea. The Southern Aral Sea had split into eastern and western lobes that
remained tenuously connected at both ends.
By
2001, the southern connection had been severed, and the shallower eastern part
retreated rapidly over the next several years. Especially large retreats in the
eastern lobe of the Southern Sea appear to have occurred between 2005 and 2009,
when drought limited and then cut off the flow of the Amu Darya. Water levels
then fluctuated annually between 2009 and 2014 in alternately dry and wet
years. Dry conditions in 2014 caused the Southern Sea’s eastern lobe to
completely dry up for the first time in modern times.
As
the lake dried up, fisheries and the communities that depended on them
collapsed. The increasingly salty water became polluted with fertilizer and
pesticides. The blowing dust from the exposed lakebed, contaminated with
agricultural chemicals, became a public health hazard. The salty dust blew off
the lakebed and settled onto fields, degrading the soil. Croplands had to be flushed
with larger and larger volumes of river water. The loss of the moderating
influence of such a large body of water made winters colder and summers hotter
and drier.
In
a last-ditch effort to save some of the lake, Kazakhstan built a dam between
the northern and southern parts of the Aral Sea. Completed in 2005, the dam was
basically a death sentence for the southern Aral Sea, which was judged to be
beyond saving. All of the water flowing into the desert basin from the Syr
Darya now stays in the Northern Aral Sea. Between 2005 and 2006, the water
levels in that part of the lake rebounded significantly and very small
increases are visible throughout the rest of the time period. The differences
in water color are due to changes in sediment.
Iceland is a creation of plate tectonics.
Iceland is a creation of
plate tectonics. The North American and European plates are spreading apart
here at the rate of about 1 in (2.5 cm) each year. The island abounds with
visual evidence of this movement. Most recently, a new fissure has erupted in the
Holuhraun lava field just north of Dyngjujokull, part of the larger Vatnajokull
(jokull is Icelandic for glacier). The photo above shows the eastern lava field
of the Holuhraun fissure eruption as the lava meets the Jokulsa a Fjollum,
Iceland’s second longest river. Jokulsa a Fjollum carries meltwater from
glaciers near its source to the sea more than 125 mi (200 km) distant. At the
time the photo was taken the lava was flowing at a rate of about 328 ft (100 m)
per hour and covered 7 sq mi (19 sq km) making it the largest such flow Iceland
has seen since 1875. Photo taken September 8, 2014.
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