Earth Weather / Space Weather

Happy 22nd Birthday, Hubble!

By: Susie77, 8:18 PM GMT on April 17, 2012

Hubble's Panoramic View of a Turbulent Star-Making Region

The image comprises one of the largest mosaics ever assembled from Hubble photos and includes observations taken by Hubble's Wide Field Camera 3 and Advanced Camera for Surveys.
Credit: ESA/Hubble & NASA

The image comprises one of the largest mosaics ever assembled from Hubble photos and includes observations taken by Hubble's Wide Field Camera 3 and Advanced Camera for Surveys. Hubble made the observations in October 2011. NASA and the Space Telescope Science Institute are releasing the image to celebrate Hubble's 22nd anniversary. Credit: NASA, ESA, D. Lennon and E. Sabbi (ESA/STScI), J. Anderson, S. E. de Mink, R. van der Marel, T. Sohn, and N. Walborn (STScI), N. Bastian (Excellence Cluster, Munich), L. Bedin (INAF, Padua), E. Bressert (ESO), P. Crowther (University of Sheffield), A. de Koter (University of Amsterdam), C. Evans (UKATC/STFC, Edinburgh), A. Herrero (IAC, Tenerife), N. Langer (AifA, Bonn), I. Platais (JHU), and H. Sana (University of Amsterdam)

Several million young stars are vying for attention in a new NASA Hubble Space Telescope image of a raucous stellar breeding ground in 30 Doradus, a star-forming complex located in the heart of the Tarantula nebula.

The new image comprises one of the largest mosaics ever assembled from Hubble photos and includes observations taken by Hubble's Wide Field Camera 3 and Advanced Camera for Surveys. NASA and the Space Telescope Science Institute (STScI) in Baltimore released the image today in celebration of Hubble's 22nd anniversary.

"Hubble is the world's premiere science instrument for making celestial observations, which allow us to unravel the mysteries of the universe," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington and three-time Hubble repair astronaut. "In recognition of Hubble's 22nd birthday, the new image of the 30 Doradus region, the birth place for new stars, is more than a fitting anniversary image."

30 Doradus is the brightest star-forming region in our galactic neighborhood and home to the most massive stars ever seen. The nebula is 170,000 light-years away in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way. No known star-forming region in our galaxy is as large or as prolific as 30 Doradus.

Collectively, the stars in the image are millions of times more massive than our sun. The image is roughly 650 light-years across and contains some rambunctious stars, including one of the fastest rotating stars and the highest velocity stars ever observed by astronomers.

The nebula is close enough to Earth that Hubble can resolve individual stars, giving astronomers important information about the stars' birth and evolution. Many small galaxies have more spectacular starbursts, but the Large Magellanic Cloud's 30 Doradus is one of the only star-forming regions that astronomers can study in detail. The star-birthing frenzy in 30 Doradus may be fueled partly by its close proximity to its companion galaxy, the Small Magellanic Cloud.

The image reveals the stages of star birth, from embryonic stars a few thousand years old and still wrapped in cocoons of dark gas, to behemoths that die young in supernova explosions. 30 Doradus churns out stars at a furious pace over millions of years. Hubble shows star clusters of various ages, from about 2 million to 25 million years old.

The region's sparkling centerpiece is a giant, young star cluster named NGC 2070, only 2 million to 3 million years old. Its stellar inhabitants number roughly 500,000. The cluster is a hotbed for young, massive stars. Its dense core, known as R136, is packed with some of the heftiest stars found in the nearby universe, weighing more than 100 times the mass of our sun.

The massive stars are carving deep cavities in the surrounding material by unleashing a torrent of ultraviolet light, which is winnowing away the enveloping hydrogen gas cloud in which the stars were born. The image reveals a fantastic landscape of pillars, ridges and valleys. Besides sculpting the gaseous terrain, the brilliant stars may be triggering a successive generation of offspring. When the ultraviolet radiation hits dense walls of gas, it creates shocks, which may generate a new wave of star birth.

The image was made using 30 separate fields, 15 from each camera. Both cameras made these observations simultaneously in October 2011. The colors in the image represent the hot gas that dominates regions of the image. Red signifies hydrogen gas and blue represents oxygen.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. STScI conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc., in Washington.

Updated: 11:51 AM GMT on April 19, 2012


Lyrid Meteor Shower

By: Susie77, 7:47 PM GMT on April 14, 2012

From: Space Weather

Every year in late April Earth passes through the dusty tail of Comet Thatcher (C/1861 G1), and the encounter causes a meteor shower--the Lyrids. This year the shower peaks on Saturday night, April 21st. Forecasters expect 10 to 20 meteors per hour, although outbursts as high as 100 meteors per hour are possible.

Lyrid meteors appear to stream from the bright star Vega in the constellation Lyra:

In fact, Lyrids have nothing to do with Vega. The true source of the shower is Comet Thatcher. Every year in April, Earth plows through Thatcher's dusty tail. Flakes of comet dust, most no bigger than grains of sand, strike Earth's atmosphere traveling 49 km/s (110,000 mph) and disintegrate as streaks of light.

Lyrid meteors are typically as bright as the stars in the Big Dipper, which is to say of middling brightness. But some are more intense, even brighter than Venus. These "Lyrid fireballs" cast shadows for a split second and leave behind smokey debris trails that linger for minutes.

Occasionally, the shower intensifies. Most years in April there are no more than 5 to 20 meteors per hour during the shower's peak. But sometimes, when Earth glides through an unusually dense clump of comet debris, the rate increases. Sky watchers in 1982, for instance, counted 90 Lyrids per hour. An even more impressive outburst was documented in 1803 by a journalist in Richmond, Virginia, who wrote:

"Shooting stars. This electrical [sic] phenomenon was observed on Wednesday morning last at Richmond and its vicinity, in a manner that alarmed many, and astonished every person that beheld it. From one until three in the morning, those starry meteors seemed to fall from every point in the heavens, in such numbers as to resemble a shower of sky rockets..." [ref]

What will the Lyrids do this year? The only way to know for sure is to go outside and look.

Experienced meteor watchers suggest the following viewing strategy: Dress warmly. Bring a reclining chair, or spread a thick blanket over a flat spot of ground. Lie down and look up somewhat toward the east. Meteors can appear in any part of the sky, although their trails will tend to point back toward the radiant--i.e., toward Vega.

Vega is a brilliant blue-white star about three times wider than our Sun and 25 light years away. You might have seen Vega in Carl Sagan's movie Contact. It was the source of alien radio transmissions to Earth.


Venus and the Pleiades

By: Susie77, 12:18 AM GMT on April 03, 2012

Venus Invades the Pleiades

April 2, 2012: Watch out Seven Sisters, Venus is coming.

This week the second planet from the sun will pass directly in front of the Pleiades star cluster. It's a rare sunset conjunction that's easy to find with the unaided eye, but best seen through binoculars or a small telescope.

The action begins on Monday evening, April 2nd, when Venus enters the outskirts of the little dipper-shaped asterism. Look west at sunset for Venus--it's the brightest thing around--then scan the area using binoculars. The conjunction will be immediately clear. The best evening to look is Tuesday, April 3rd, when the brilliant planet glides just south of the dipper's bowl. Venus exits by the handle on Wednesday, April 4th. Venus passes through the Pleiades in this way about once every 8 years.

To say this is a mixture of dissimilar things would be an understatement.

The Pleiades are elusive. You rarely find them on purpose. They're best seen out of the corner of your eye, a pretty little surprise that pops out of the night sky when you're staring elsewhere.

Venus is just the opposite. Dazzling, bright enough to cast faint shadows, it beams down from the heavens and grabs you when you're not even looking.

The Pleiades, also known as the "Seven Sisters," are a cluster of young stars. They formed barely 100 million years ago during the age of dinosaurs on Earth from a collapsing cloud of interstellar gas. The biggest and brightest members are blue-white and about five times wider than our own sun.

Because of their distance, about 400 light years away, the Pleiades are near the limit of naked-eye visibility. When Venus joins them in conjunction, it will look like a supernova has gone off inside the cluster. Venus's thick clouds reflect so much sunlight, the planet outshines every thing in the night sky except the Moon. Strangely, though, the Pleiades do not look puny in comparison, just delicately beautiful.

Look west just after sunset, and see for yourself.

Author:Dr. Tony Phillips| Production editor: Dr. Tony Phillips | Credit: Science@NASA


Lightning Sprite Season -- Early This Year

By: Susie77, 10:22 PM GMT on April 01, 2012

From Space Weather

SPRITE SEASON BEGINS: The first sprites of summer are starting to appear in the skies of North America. The strange thing is, summer is almost three months away. "Sprite season is beginning early this year," says Thomas Ashcraft, who photographed these specimens on March 30th from his observatory in New Mexico:

"At precisely two minutes and twenty-six seconds after midnight March 30, 2012 there was an incredibly powerful bolt of lightning in the vicinity of Woodward, Oklahoma that spawned these red sprites," says Ashcraft. "I could see them from two states away!" He also recorded VLF and shortwave radio emissions from the cluster, which you can hear as the soundtrack to this video.

Sprites are electrical discharges that come out of the top of thunderclouds, opposite ordinary lightning bolts which plunge toward Earth. Sprites can tower as high as 90 km above ground. That makes them a form of space weather as they overlap the zone of auroras, meteors, and noctilucent clouds.

Because they are associated with lightning, sprites are most often seen in summer months, "but in the past few days sprites have been reported in Texas (particularly near the Mexican border) as well as here in New Mexico," notes Ashcraft.

Updated: 12:42 AM GMT on April 02, 2012


About Susie77

Sometimes I complain about the earthly weather, but mostly I like to post about astronomy and space events. Hope you enjoy the articles.

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