Astronomical News

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[Astronomy]

Astronomers Using NASA's Hubble Discover Quasars Acting as Gravitational Lenses

Astronomers using NASA's Hubble Space Telescope have found several examples of galaxies containing quasars, which act as gravitational lenses, amplifying and distorting images of galaxies aligned behind them.






Quasars are among the brightest objects in the universe, far outshining the total starlight of their host galaxies. Quasars are powered by supermassive black holes. To find these rare cases of galaxy-quasar combinations acting as lenses, a team of astronomers selected 23,000 quasar spectra in the Sloan Digital Sky Survey (SDSS). They looked for the spectral imprint of galaxies at much greater distances that happened to align with foreground galaxies. Once candidates were identified, Hubble's sharp view was used to look for gravitational arcs and rings (indicated by the arrows in these three Hubble photos) that would be produced by gravitational lensing.


Fast Facts: http://hubblesite.org/newscenter/arc.../14/fastfacts/


Release Images: http://hubblesite.org/newscenter/arc...2012/14/image/


Related Links: http://hubblesite.org/newscenter/arc...12/14/related/


From: http://hubblesite.org/

[رخساره روشنی]

In honor of 1,000 days in orbit, the NASA Lunar Reconnaissance Orbiter (LRO) team at NASA Goddard Space Flight Center in Greenbelt Md. has released two new videos.

One video takes viewers through the moon's evolutionary history, and reveals how it came to appear the way it does today. Another video gives viewers a guided tour of prominent locations on the moon's surface, compiled by the spacecraft's observations of the moon.

"Evolution of the Moon" explains why the moon did not always look like it does now. The moon likely started as a giant ball of magma formed from the remains of a collision by a Mars sized object with the Earth about four and a half billion years ago. After the magma cooled, the moon's crust formed. Then between 4.5 and 4.3 billion years ago, a giant object hit near the moon's South Pole, forming the South Pole-Aitken Basin, one of the two largest proven impact basins in the solar system. This marked the beginning of collisions that would cause large scale changes to the moon's surface, such as the formation of large basins.

Because the moon had not entirely cooled on the inside, magma began to seep through cracks caused by impacts. Around one billion years ago, it's thought that volcanic activity ended on the near side of the moon as the last of the large impacts made their mark on the surface. The moon continued to be battered by smaller impacts. Some of the best-known impacts from this period include the Tycho, Copernicus, and Aristarchus craters. So, while the moon today may seem to be an unchanging world, its appearance is the result of billions of years of violent activity.

The two-and-a-half minute video is available for viewing and downloading at: http://svs.gsfc.nasa.gov/goto?10930

for see movie of this tour go to this link I suggest that see them they wonderfull :
http://www.nasa.gov/mission_pages/LR.../vid-tour.html

[آریا برزن]

CELESTIAL TRIANGLE

They're at it again. Venus, Jupiter and the crescent Moon are in conjunction, forming a bright triangle in the sunset sky. On Sunday evening, March 25th, Alexandre Croisier photographed the trio from the Pointe of Dinan in Brittany, France:
"They are easy to see with the naked eye," says Croisier, "and they look great through a telescope, too."

The triangle will appear again on Monday evening, March 26th, although the vertices will be shifted as the Moon glides from Jupiter to Venus. Observing tip: Look before the sky fades completely black. Bright planets are extra-beautiful when they are framed by twilight blue

Source : http://spaceweather.com/

[Emil Sola]

Hubble's panoramic view of a turbulent star-making region

30 Doradus is the brightest star-forming region in our galactic neighborhood and home to the most massive stars ever seen. The nebula resides 170,000 light-years away in the Large Magellanic Cloud, a small, satellite galaxy of our Milky Way. No known star-forming region in our galaxy is as large or as prolific as 30 Doradus. 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, combined with observations from the European Southern Observatory's MPG/ESO 2.2-metre telescope which trace the location of glowing hydrogen and oxygen. The image is being released to celebrate Hubble's 22nd anniversary. Credit: NASA, ESA, ESO, D. Lennon and E. Sabbi (ESA/STScI), J. Anderson, S.E. de Mink, R. van der Marel, T. Sohn, and N. Walborn (STScI), L. Bedin (INAF, Padua), C. Evans (STFC), H. Sana (Amsterdam), N. Langer (Bonn), P. Crowther (Sheffield), A. Herrero (IAC, Tenerife), N. Bastian (USM, Munich), and E. Bressert (ESO)


30 Doradus is the brightest star-forming region in our galactic neighbourhood and home to the most massive stars ever seen. The nebula resides 170 000 light-years away in the Large Magellanic Clouds, a small, satellite galaxy of our Milky Way. No known star-forming region in our galaxy is as large or as prolific as 30 Doradus.
The image comprises one of the largest mosaics ever assembled from Hubble photos and consists of observations taken by Hubble's Wide Field camera 3 and Advanced Camera for Surveys, combined with observations from the European Southern Observatory's MPG/ESO 2.2-metre telescope that trace the location of glowing hydrogen and oxygen.
The image is being released to celebrate Hubble's 22nd anniversary.
The stars in this image add up to a total mass millions of times bigger than that of our Sun. The image is roughly 650 light-years across and contains some rambunctious stars, from one of the fastest rotating stars to the speediest and most massive runaway star.
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 partly fueled by its close proximity to its companion galaxy , the small Magellanic clouds.
The image reveals the stages of star birth, from embryonic stars a few thousand years old still wrapped in dark cocoons of dust and gas to behemoths that die young in supernova explosions. 30 Doradus is a star-forming factory, churning out stars at a furious pace over millions of years. The Hubble image shows star clusters of various ages, from about 2 million to about 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 RMC 136, 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 etching away the enveloping hydrogen gas cloud in which the stars were born. The image reveals a fantasy landscape of pillars, ridges, and valleys. Besides sculpting the gaseous terrain, the brilliant stars also may be triggering a successive generation of offspring.
When the radiation hits dense walls of gas, it creates shocks, which may be generating a new wave of star birth.
The colours come from the glowing hot gas that dominates regions of the image. Red signifies hydrogen gas and blue, oxygen.
The image was made from 30 separate fields, 15 from each camera. Hubble made the observations in October 2011. Both cameras were making observations at the same time.

[Emil Sola]

Some stars capture rogue planets

New research suggests that billions of stars in our galaxy have captured rogue planets that once roamed interstellar space. The nomad worlds, which were kicked out of the star systems in which they formed, occasionally find a new home with a different sun. This finding could explain the existence of some planets that orbit surprisingly far from their stars, and even the existence of a double-planet system.


"Stars trade planets just like baseball teams trade players," said Hagai Perets of the Harvard-Smithsonian Center for Astrophysics.
The study, co-authored by Perets and Thijs Kouwenhoven of Peking University, China, will appear in the April 20th issue of The Astrophysical Journal.
To reach their conclusion, Perets and Kouwenhoven simulated young star clusters containing free-floating planets. They found that if the number of rogue planets equaled the number of stars, then 3 to 6 percent of the stars would grab a planet over time. The more massive a star, the more likely it is to snag a planet drifting by.
They studied young star clusters because capture is more likely when stars and free-floating planets are crowded together in a small space. Over time, the clusters disperse due to close interactions between their star, so any planet-star encounters have to happen early in the cluster's history.
Rogue planets are a natural consequence of star formation. Newborn star systems often contain multiple planets. If two planets interact, one can be ejected and become an interstellar traveler. If it later encounters a different star moving in the same direction at the same speed, it can hitch a ride.
A captured planet tends to end up hundreds or thousands of times farther from its star than Earth is from the Sun. It's also likely to have a orbit that's tilted relative to any native planets, and may even revolve around its star backward.
Astronomers haven't detected any clear-cut cases of captured planets yet. Imposters can be difficult to rule out. Gravitational interactions within a planetary system can throw a planet into a wide, tilted orbit that mimics the signature of a captured world.
Finding a planet in a distant orbit around a low-mass star would be a good sign of capture, because the star's disk wouldn't have had enough material to form the planet so far out.
The best evidence to date in support of planetary capture comes from the European Southern Observatory, which announced in 2006 the discovery of two planets (weighing 14 and 7 times Jupiter) orbiting each other without a star.
"The rogue double-planet system is the closest thing we have to a 'smoking gun' right now," said Perets. "To get more proof, we'll have to build up statistics by studying a lot of planetary systems."
Could our solar system harbor an alien world far beyond Pluto? Astronomers have looked, and haven't found anything yet.
"There's no evidence that the Sun captured a planet," said Perets. "We can rule out large planets. But there's a non-zero chance that a small world might lurk on the fringes of our solar system."

[Emil Sola]

Space shuttle Discovery salutes nation's capital

The space shuttle Discovery soared over the Washington Monument, the White House and the Capitol in a high-flying salute to the nation's capital Tuesday.


The world's most traveled spaceship, hitching a ride on top a Boeing 747 jet, took a couple of leisurely spins at an easy-to-spot 1,500 feet around Washington after a flight from Cape Canaveral, Fla.
Thousands packed the National Mall to watch the pair swoop by.
"Look at that - that thing is mammoth," said Terri Jacobsen of Bethesda, Md. She brought her 12-year-old home-schooled son to the mall to watch the flyover
The shuttle-jet combo was set to land at Dulles International Airport. On Thursday, it will be towed to its permanent installation at the Smithsonian's annex in northern Virginia.
Discovery departed Florida's Kennedy space center at daybreak. Nearly 2,000 people - former shuttle workers, VIPs, tourists and journalists - gathered along the old shuttle landing strip to see Discovery off. A cheer went up as the plane taxied down the runway and soared into a clear sky.

[Astronomy]

Hubble's 22nd Anniversary Image Shows Turbulent Star-making Region





Several million young stars are vying for attention in this NASA Hubble Space Telescope image of a raucous stellar breeding ground in 30 Doradus, located in the heart of the Tarantula Nebula.
30 Doradus is the brightest star-forming region visible in a neighboring galaxy and home to the most massive stars ever seen. The nebula resides 170,000 light-years away in the Large Magellanic Cloud, a small, satellite galaxy of our Milky Way. No known star-forming region that is inside our Milky Way is as large or as prolific as 30 Doradus.
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.



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[Astronomy]

Hubble Spots Aurorae on the Planet Uranus



These are among the first clear images, taken from the distance of Earth, to show aurorae on the planet Uranus. This composite image combines 2011 Hubble observations of the aurorae in visible and ultraviolet light, 1986 Voyager 2 photos of the cyan disk of Uranus as seen in visible light, and 2011 Gemini Observatory observations of the faint ring system as seen in infrared light.

For more information, visit http://www.agu.org/news/press/pr_arc.../2012-19.shtml

From: http://hubblesite.org/

[رخساره روشنی]

NASA Mission Wants Amateur Astronomers to Target Asteroids

A new NASA outreach project will enlist the help of amateur astronomers to discover near-Earth objects (NEOs) and study their characteristics. NEOs are asteroids with orbits that occasionally bring them close to the Earth.

Starting today, a new citizen science project called "Target Asteroids!" will support NASA's Origins Spectral Interpretation Resource Identification Security - Regolith Explorer (OSIRIS-REx) mission objectives to improve basic scientific understanding of NEOs. OSIRIS-Rex is scheduled for launch in 2016 and will study material from an asteroid.

Amateur astronomers will help better characterize the population of NEOs, including their position, motion, rotation and changes in the intensity of light they emit. Professional astronomers will use this information to refine theoretical models of asteroids, improving their understanding about asteroids similar to the one OSIRIS-Rex will encounter in 2019, designated 1999 RQ36.
for read more go to this link:http://www.nasa.gov/topics/solarsyst...ex-update.html

[COLDFIRE]

North star loses mass but still shines bright




This sequence of images taken by the Hubble Space Telescope shows that the North Star, Polaris, is a triple star system. New research also confirms the main North Star is a Cepheid variable.



Credit:
NASA, ESA, N. Evans (Harvard-Smithsonian CfA), and H. Bond (STScI)








The North Star, the Pole Star, the Guiding Star, Polaris: Its many names reflect the many centuries humans have gazed northward to it for guidance. Because Earth’s North Pole is aligned with Polaris’ position in the sky, the star appears motionless, providing a steadfast beacon for early sailors and adventurers alike. But the star itself is far from motionless. In fact, Polaris is a specific type of star known as a Cepheid variable, which pulsates, varying in size and luminosity over a period of days and, according to recent observations, also ejects large amounts of mass into space. Now, combining 170 years worth of observational data on Polaris’ pulsation rates with state-of-the-art stellar evolution models, a team of scientists suggests that Polaris is losing mass at a significant rate. But this does not mean Polaris will vanish from the night sky anytime soon.
When Polaris was first suspected as a variable star in the mid-19th century, its pulsation period was shorter than it is today. Each year, the star’s time between pulses has lengthened by an average of eight seconds, and it’s this change in period that got Hilding Neilson of Argelander Institute for Astronomy at University of Bonn in Germany and his colleagues thinking about the inherent relationship between the rate of period change and mass loss.
“The question is, ‘What drives enhanced mass loss [in Cepheid variables]?’” Neilson says. “There are ideas that the Cepheid pulsation itself will generate waves in the interior and as those waves move outward, they turn into shocks. And those shocks help drive enhanced mass loss.”
Although it is unknown whether this process takes placea on Polaris, Neilson and his colleagues have measured the rate of mass loss. Polaris has been the subject of study for many years, so its parameters, such as distance from Earth, stellar radius and temperature, are known to within a small percentage of error, Neilson says.
Neilson and colleagues input these parameters, along with many others, into computer models to predict the rate that Polaris’ pulsation period is changing. When they compared their rates with those from observations over the past 170 years, they found a discrepancy. Basically, the theory disagreed with the observations.
However, when the researchers tweaked Polaris’ rate of mass loss, they found they could fix the discrepancy. If Polaris were ejecting mass equal to approximately the mass of Earth each year, then the predictions of Polaris’ rate of period change closely resembled the observational data, the team reported in the Astrophysical Journal Letters.
Although Neilson and his colleagues attribute the model discrepancy in the rate of period change between observational data and theoretical modeling to mass loss, some scientists say it may not be the only answer.“They get this result that the period change is doing a particular thing and they give one particular explanation, but it’s probably not the only explanation,” says Pauline Barmby, of Western University in Ontario, Canada, who was not involved with the study. For example, Barmby says, another possible explanation — put forth by Richard B. Strothers of the NASA Goddard Institute for Space Studies in a 2009 paper in the Astrophysical Journal — could be that a slow change in the star’s magnetic field is affecting convection and hence periodicity.
Still, even if the debate cannot be rectified, Barmby says, there are several advantages to studying mass loss in Cepheid variables. First, Cepheid variables represent a short phase in certain stars’ lifetimes (lasting about 10 million years) when the star is no longer a main-sequence star like our sun, nor is it a red giant or supergiant — the next evolutionary step initiated by helium burning in a star’s core. During this stage of stellar evolution, stars expand and contract, and the physics behind these pulses is considered to be well understood. So Cepheid variables provide a diagnostic for the structure of stars as they evolve off of the main sequence, which can improve stellar evolution modeling.
Second, knowing their period allows for fairly accurate distance measurements, which are important in cosmology. Measuring the distance to Cepheids in other galaxies is a way for cosmologists to determine how fast the universe is expanding, Neilson says. Therefore, determining the mass loss rate of Cepheid variables is important because it can affect the stars’ luminosity and hence distance calibrations, he adds.
“If you can understand Cepheids better from a theoretical point of view,” Barmby says, “that might help make calibration more solid for using them for finding distance, which would have quite a wide impact on astronomy in general.”
source:
http://www.earthmagazine.org/article...-shines-bright