Dec 10

New Zooniverse site: The Milky Way Project

Galaxy Zoo has launched a brand new site: The Milky Way Project (http://www.milkywayproject.org). The Milky Way Project aims to sort and measure our galaxy, the Milky Way. Their asking people to help find and draw bubbles in beautiful infrared data from the Spitzer Space Telescope. Understanding the cold, dusty material that can be seen in those images might help scientists to learn how stars form and how our galaxy changes and evolves with time.

As well as drawing out bubbles in our galaxy, they are also asking people to mark other objects such as star clusters, galaxies and ghostly red 'fuzzy' objects. People are invited to help to map star formation in the Galaxy.(read more)

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Dec 10

A Swarm of Ancient Stars

Source: ESO Photo Release eso1048

Globular cluster Messier 107, also known as NGC 6171, located about 21 000 light-years away in the constellation of Ophiuchus.
Image credit: ESO/ESO Imaging Survey

About 150 of the rich collections of old stars called globular clusters are known to orbit our galaxy, the Milky Way. This sharp new image of Messier 107, captured by the Wide Field Imager on the 2.2-meter telescope at ESO’s La Silla Observatory in Chile, displays the structure of one such globular cluster in exquisite detail. Studying these stellar swarms has revealed much about the history of our galaxy and how stars evolve. (read more)

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Dec 10

Messenger's countdown for Mercury orbit insertion

Source: Messenger Mission

One hundred days from now, MESSENGER will execute a 15-minute maneuver that will place the spacecraft into orbit about Mercury, making it the first craft ever to do so, and initiating a one-year science campaign to understand the innermost planet.

Artist's impression about the Mercury orbit insertion.
Image credits: NASA/JPL/Messenger

It has already been 14 years since this mission was first proposed to NASA, more than 10 years since the project officially began, and over six years since the spacecraft was launched.

A multitude of milestones have been passed on the way toward the primary science phase of the mission, including six planetary flybys and five deep-space maneuvers. This week the team has completed a milestone of a different sort: the orbital readiness review.

Today’s review was the culmination of more than one year of major reviews designed to confirm the readiness of all mission elements to achieve orbit about Mercury next March and to begin orbital operations shortly thereafter.

“For this and many reviews before it we have called on a number of experts outside the MESSENGER project, from both APL and outside institutions, to review our plans to see where there are gaps or weak spots,” explains MESSENGER Project Manager Peter Bedini of the Johns Hopkins University Applied Physics Laboratory. “The intent is to tap the knowledge-base of those who have lived through similar challenges, and to make any adjustments that promise to improve the chances of success in our prime mission.”

“There is still work to do in preparation for orbit insertion next March, and those preparations will also be reviewed, but today’s review was the last in a long series laid out more than a year ago,” Bedini adds.

“MESSENGER has been on a long journey,” adds MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington, “but the promised land lies ahead.  All of the preparations for orbit insertion and orbital operations by the project team and the mission’s many review panels have served to maximize the likelihood that the intensive exploration of the innermost planet will begin smoothly and efficiently 100 days from now.”

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Dec 10

Geminid Meteors not yet completely explained

Source: NASA Science News

The Geminid meteor shower, which peaks this year on Dec. 13th and 14th, is the most intense meteor shower of the year. It lasts for days, is rich in fireballs, and can be seen from almost any point on Earth.


It's also NASA astronomer Bill Cooke's favorite meteor shower—but not for any of the reasons listed above.

"The Geminids are my favorite," he explains, "because they defy explanation."

Most meteor showers come from comets, which spew ample meteoroids for a night of 'shooting stars.' The Geminids are different. The parent is not a comet but a weird rocky object named 3200 Phaethon that sheds very little dusty debris—not nearly enough to explain the Geminids.

A geminid fireball over Bratislava.
Image credit: Roman Piffl

"Of all the debris streams Earth passes through every year, the Geminids' is by far the most massive," says Cooke. "When we add up the amount of dust in the Geminid stream, it outweighs other streams by factors of 5 to 500."

This makes the Geminids the 900-lb gorilla of meteor showers. Yet 3200 Phaethon is more of a 98-lb weakling.

3200 Phaethon was discovered in 1983 by NASA's IRAS satellite and promptly classified as an asteroid. What else could it be? It did not have a tail; its orbit intersected the main asteroid belt; and its colors strongly resembled that of other asteroids. Indeed, 3200 Phaethon resembles main belt asteroid Pallas so much, it might be a 5-kilometer chip off that 544 km block.

"If 3200 Phaethon broke apart from asteroid Pallas, as some researchers believe, then Geminid meteoroids might be debris from the breakup," speculates Cooke. "But that doesn't agree with other things we know."

Researchers have looked carefully at the orbits of Geminid meteoroids and concluded that they were ejected from 3200 Phaethon when Phaethon was close to the sun—not when it was out in the asteroid belt breaking up with Pallas. The eccentric orbit of 3200 Phaethon brings it well inside the orbit of Mercury every 1.4 years. The rocky body thus receives a regular blast of solar heating that might boil jets of dust into the Geminid stream.

Could this be the answer?

A Geminid fireball over the Mojave Desert.
Image credit: Wally Pacholka.

To test the hypothesis, researchers turned to NASA's twin STEREO spacecraft, which are designed to study solar activity. Coronagraphs onboard STEREO can detect sungrazing asteroids and comets, and in June 2009 they detected 3200 Phaethon only 15 solar diameters from the sun's surface.

What happened next surprised UCLA planetary scientists David Jewitt and Jing Li, who analyzed the data. "3200 Phaethon unexpectedly brightened by a factor of two," they wrote. "The most likely explanation is that Phaethon ejected dust, perhaps in response to a break-down of surface rocks (through thermal fracture and decomposition cracking of hydrated minerals) in the intense heat of the Sun."

Jewett and Li's "rock comet" hypothesis is compelling, but they point out a problem: The amount of dust 3200 Phaethon ejected during its 2009 sun-encounter added a mere 0.01% to the mass of the Geminid debris stream—not nearly enough to keep the stream replenished over time. Perhaps the rock comet was more active in the past …?

"We just don't know," says Cooke. "Every new thing we learn about the Geminids seems to deepen the mystery."

This month Earth will pass through the Geminid debris stream, producing as many as 120 meteors per hour over dark-sky sites. The best time to look is probably between local midnight and sunrise on Tuesday, Dec. 14th, when the Moon is low and the constellation Gemini is high overhead, spitting bright Geminids across a sparkling starry sky.

Bundle up, go outside, and savor the mystery.

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Dec 10

Comparison of dark energy models: A perspective from the latest observational data

Physicists at the Institute of Theoretical Physics, Chinese Academy of Sciences and the Department of Physics at Northeastern University have made a comparison of a number of competing dark energy models. They have tested and compared nine popular dark energy models using the latest observational data. The study is reported in Issue 9 (Volume 53) of SCIENCE CHINA Physics, Mechanics & Astronomy because of its significant research value.

Web-like structure of  'superclusters' of galaxies, leaving ever larger voids behind.
The greater rate of expansion in the voids may account for the observations usually attributed to dark energy.(Illustration credit: Center for Cosmological Physics/U Chicago)

Over the past decade, cosmologists around the world have accumulated conclusive evidence for the fact that the cosmic expansion is accelerating. Within the framework of the standard cosmological model, this implies that about two-thirds of the cosmos is composed of an exotic component, “dark energy”, which, unlike any known form of matter or energy, is gravitationally repulsive. To explain the gravitationally repulsive dark energy, physicists and cosmologists have proposed a variety of theoretical models. However, none of them are commonly accepted as the convincing theoretical explanation for dark energy. Understanding the nature of dark energy continues to be one of the major missions for fundamental physics.

In the absence of clear theoretical guidance, the physics community is reliant on comparison to observational data in selecting a correct dark energy model. In this work, nine popular dark energy models are tested and compared using the latest observational data, which includes type Ia supernovae, baryon acoustic oscillation, and cosmic microwave background. The models under consideration are the cosmological constant (CC) model, two equation of state parameterization models, the generalized Chaplygin gas model, two Dvali-Gabadadze-Porrati models, and three holographic dark energy models. All of these models are well-known dark energy candidates and have attracted considerable attention in the past.

The dark energy models have been fitted to the observational data. In this procedure, each model is assessed with a number called the IC value. Statistically, a model with fewer parameters and with a better fit to the data has a lower IC value. The models under consideration have been compared and ranked according to their IC values.

Consequently, it has been found that the CC model fits the observational data best. In addition to the CC model, five other models also provide a good fit to the current data, while the remaining three models, a Dvali-Gabadadze-Porrati model and two holographic models, clearly do not fit the observational data well. (For simplicity, we call them the five good models and the three bad models.) It is interesting to note that four of the five good models are closely related to the CC model, which may be the reason they fit the data so well, while none of the bad models can be reduced to the CC model.

Furthermore, it is interesting to note that there is one holographic dark energy model, which is not reducible to the CC model, yet it still provides a good fit to the current observational data. This model was proposed by Professor Miao Li, one of the authors of this work. As the name implies, this holographic dark energy model arises from the holographic principle of quantum gravity. The holographic principle determines the range of validity for a local effective quantum field theory to be an accurate description of the world involving dark energy by imposing a relationship between the ultraviolet and infrared cut-offs. In his well-known article, “A Model of Holographic Dark Energy”, Li has shown that a form of holographic dark energy emerges if the future event horizon size of the universe is chosen as the infrared cut-off scale in the effective quantum field theory.

In summary, the CC model is still the best candidate for dark energy, according to the results from fitting models to current observational data. The authors concluded that “Given the current quality of the observational data, and with the assumption of a flat universe, information criteria indicate that the cosmological constant model is still the best one and there is no reason to prefer any more complex model”. However, as new observations are made, it is possible that the preferred model could change. It is important to keep in mind that there are limitations associated with the current observational data. To precisely determine the nature of dark energy, an improvement in the accuracy of data is of essential importance. “We look forward to seeing whether this conclusion [that the CC model is the best candidate for dark energy] can be changed by future more accurate data,” said the authors in the final statement of the paper.

Reference: Li M, Li X.D. and Zhang X. SCIENCE CHINA Physics, Mechanics & Astronomy 2010; 53: 1631-1645

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Dec 10

Project Moonwalkers - Total Lunar Eclipse Observations

Project Moonwalkers intends to be a project by which the schools can help students to learn more about the Moon. This month it brings a new  challenge to school teachers and to all educators in general.

Lunar Eclipse - September 2007

On December 21st there will be a lunar eclipse that will be visible at moonset in most western Europe. This eclipse's maximum will occur at 08h17min (UTC) which means it will be early in the morning.

Students and teachers are invited to share every kind of observations of the Moon that make and we will present your reports  on our webpage with due credit.

You can have your own personal projecs. It might be just to take pictures of the Moon, write poems about the Moon or anything else. Send us your layout to the OBservations Archive (eaae.moon@gmail.com) and we will be glad to present it on the projects webpage.

The Moon Eclipse on December 21st.
Credits: Wikipedia

To know what time 08h17 (UTC) is in your country consider that Coordinated Universal Time is more or less the same as GMT (Greenwich Meridian Time).

To make it easier we present bellow information about  local and Coordinated Universal Time for all Europe.

Time zones of Europe:

blue Western European Time (UTC+0)
Western European Summer Time  (UTC+1)
red Central European Time (UTC+1)
Central European Summer Time  (UTC+2)
yellow Eastern European Time  (UTC+2)
Eastern European Summer Time  (UTC+3)
green Moscow Time (UTC+3)
Moscow Summer Time(UTC+4)

Information and image credits: Wikipedia

This project is coordinated by Veselka Radeva, a long time member of the EAAE.

Link: Project Moonwalkers

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Dec 10

Recent birth of baby stars in old galaxy

Source: HubbleSite News Release STScI-2010-38

A galaxy thought to be over the hill is apparently still hard at work creating baby stars, a new study finds. Elliptical galaxies were once thought to be aging star cities whose star-making heyday was billions of years ago. But new observations with NASA's Hubble Space Telescope are helping to show that elliptical galaxies still have some youthful vigor left, thanks to encounters with smaller galaxies.

Hubble photo of the elliptical galaxy NGC 4150, once thought to be over the hill, but now revealed to be still forming new stars. Credit: NASA, ESA, R.M. Crockett (University of Oxford, U.K.), S. Kaviraj (Imperial College London and University of Oxford, U.K.), J. Silk (University of Oxford), M. Mutchler (Space Telescope Science Institute, Baltimore), R. O'Connell (University of Virginia, Charlottesville), and the WFC3 Scientific Oversight Committee.

Photos taken by the Hubble Space Telescope show the core of an elliptical galaxy known as NGC 4150,  which was thought to be beyond its fertile years for star formation, awash in streamers of dust, gas and clumps of young, blue stars that are significantly less than 1 billion years old. (read more)

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Dec 10

Discovery of "Arsenic-bug" Expands Definition of Life

Source: NASA Science

NASA-supported researchers have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism, which lives in California's Mono Lake, substitutes arsenic for phosphorus in the backbone of its DNA and other cellular components.

The newly discovered microbe, strain GFAJ-1, is a member of a common group of bacteria, the Gammaproteobacteria. In the laboratory, the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus, but included generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.

A microscopic image of GFAJ-1 grown on arsenic. Credit: NASA

"The definition of life has just expanded," said Ed Weiler, NASA's associate administrator for the Science Mission Directorate at the agency's Headquarters in Washington. "As we pursue our efforts to seek signs of life in the solar system, we have to think more broadly, more diversely and consider life as we do not know it."

This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search for life beyond Earth. The research is published in this week's edition of Science Express.

Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur are the six basic building blocks of all known forms of life on Earth. Phosphorus is part of the chemical backbone of DNA and RNA, the structures that carry genetic instructions for life, and is considered an essential element for all living cells.

Phosphorus is a central component of the energy-carrying molecule in all cells (adenosine triphosphate) and also the phospholipids that form all cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.

"We know that some microbes can breathe arsenic, but what we've found is a microbe doing something new -- building parts of itself out of arsenic," said Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in residence at the U.S. Geological Survey in Menlo Park, Calif., and the research team's lead scientist. "If something here on Earth can do something so unexpected, what else can life do that we haven't seen yet?" (read more)

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Dec 10

Red Dwarfs give new clues about the Universe's structure

Source: Harvard-Smithsonian Center for Astrophysics - Press Release 2010-26

The biggest galaxies in the universe are elliptical galaxies like the one in this artist's conception.
Image credit: David A. Aguilar (CfA)

The biggest galaxies in the universe are elliptical galaxies. The largest of these hold over one trillion stars according to astronomical census takers, compared to 400 billion in our Milky Way. However, new research shows that elliptical galaxies actually hold five to ten times as many stars as previously believed. This means that the total number of stars in the universe is likely three times bigger than realized.(read more)

The hidden stars are known as red dwarfs for their color and small size. Because red dwarfs are small and dim compared to stars like the Sun, astronomers hadn't been able to detect them in galaxies beyond the Milky Way before now. As such, they didn't know how many stars in the universe were red dwarfs.

Scientists used powerful instruments on the Keck Observatory in Hawaii to detect the faint signature of red dwarfs in the cores of eight elliptical galaxies, which are located between about 50 million and 300 million light-years away. They discovered that the red dwarfs, which are only between 10 and 30 percent as massive as the Sun, were much more bountiful than expected.

"As it turns out, the universe thinks small, at least when it comes to star size," said Harvard astronomer Charlie Conroy. "Our stellar inventory has changed dramatically."

"No one knew how many of these stars there were," said Pieter van Dokkum, a Yale University astronomer who led the research. "Different theoretical models predicted a wide range of possibilities, so this answers a long-standing question about just how abundant these stars are."

Their results imply that stellar population counts depend on what type of galaxy astronomers examine, just as a census of the city of New York and the town of Derby, Kansas will find very different population numbers.

"We usually assume other galaxies look like our own. But this suggests other conditions are possible in other galaxies," Conroy stated. "This discovery could have a major impact on our understanding of galaxy formation and evolution."

In particular, galaxies might contain less dark matter - a mysterious substance only detectable due to its gravitational effects - than previous measurements of their masses indicated. Instead, the abundant red dwarfs might contribute more mass than previously calculated.

Their findings appear in the Dec. 1st online issue of the journal Nature.

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Dec 10

First Super-Earth Atmosphere Analysed

Source: ESO Science Release eso1047

Artist’s impression about the super-Earth exoplanet orbiting the nearby star GJ 1214.
Image credit: ESO/L.Calçada

The atmosphere around a super-Earth exoplanet has been analysed for the first time by an international team of astronomers using ESO’s Very Large Telescope. The planet, which is known as GJ 1214b, was studied as it passed in front of its parent star and some of the starlight passed through the planet’s atmosphere. We now know that the atmosphere is either mostly water in the form of steam or is dominated by thick clouds or hazes. The results will appear in the 2 December 2010 issue of the journal Nature.(read more)

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Dec 10

Cassini Finds Warm Cracks on Enceladus

Source: NASA/Cassini

New images and data from NASA's Cassini spacecraft give scientists a unique Saturn-lit view of active fissures through the south polar region of Saturn's moon Enceladus. They reveal a more complicated web of warm fractures than previously thought.

Small water ice particles fly from fissures in the south polar region of Saturn's
moon Enceladus in this image taken during the Aug. 13, 2010,
flyby of the moon by NASA's Cassini spacecraft.
Image credit: NASA/JPL/SSI

Scientists working jointly with Cassini's composite infrared spectrometer and its high-resolution imaging camera have constructed the highest-resolution heat intensity maps yet of the hottest part of a region of long fissures spraying water vapor and icy particles from Enceladus. These fissures have been nicknamed "tiger stripes." Additional high-resolution spectrometer maps of one end of the tiger stripes Alexandria Sulcus and Cairo Sulcus reveal never-before-seen warm fractures that branch off like split ends from the main tiger stripe trenches. They also show an intriguing warm spot isolated from other active surface fissures.

"The ends of the tiger stripes may be the places where the activity is just getting started, or is winding down, so the complex patterns of heat we see there may give us clues to the life cycle of tiger stripes," said John Spencer, a Cassini team scientist based at Southwest Research Institute in Boulder, Colo.

The images and maps come from the Aug. 13, 2010, Enceladus flyby, Cassini's last remote sensing flyby of the moon until 2015. The geometry of the many flybys between now and 2015 will not allow Cassini to do thermal scans like these, because the spacecraft will be too close to scan the surface and will not view the south pole. This Enceladus flyby, the 11th of Cassini's tour, also gave Cassini its last look at any part of the active south polar region in sunlight. (read more)

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