Posted on by Nancy Atkinson

Mysterious Giant Gas Ring Explained

he Leo ring: deep image in the optical domain with the distribution of the gas in HI in yellow-orange. The thumbnails on the right are a three of the dense areas of the ring with their optical counterparts. © CFHT/Astron - P.A. Duc

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From a Canada-France-Hawaii Telescope press release:

An international team unveiled the origin of the giant gas ring in the Leo group of galaxies. With the Canada-France-Hawaii Telescope, the scientists were able to detect an optical signature of the ring corresponding to star forming regions. This observation rules out the primordial nature of the gas, which is of galactic origin. Thanks to numerical simulations made at CEA, a scenario for the formation of this ring has been proposed: a violent collision between two galaxies, slightly more than one billion years ago. The results will be published in the Astrophysical Journal Letters.

In the current theories on galaxy formation, the accretion of cold primordial gas is a key-process in the early steps of galaxy growth. This primordial gas is characterized by two main features: it has never sojourned in any galaxy and it does not satisfy the conditions required to form stars. Is such an accretion process still ongoing in nearby galaxies? To answer the question, large sky surveys are undertaken attempting to detect the primordial gas.

The Leo ring, a giant ring of cold gas 650,000 light-years wide surrounding the galaxies of the Leo group, is one of the most dramatic and mysterious clouds of intergalactic gas. Since its discovery in the 80s, its origin and its nature were debated. Last year, studies of the metal abundances in the gas led to the belief that the ring was made of this famous primordial gas.

Thanks to the sensitivity of the Canada-France-Hawaii Telescope MegaCam camera, the international team observed for the first time the optical counterpart of the densest regions of the ring, in visible light instead of radio waves. Emitted by massive young stars, this light points to the fact that the ring gas is able to form stars.

A ring of gas and stars surrounding a galaxy immediately suggests another kind of ring: a so-called collisional ring, formed when two galaxies collide. Such a ring is seen in the famous Cartwheel galaxy. Would the Leo ring be a collisional ring too?

In order to secure this hypothesis, the team used numerical simulations (performed on supercomputers at CEA) to demonstrate that the ring was indeed the result of a giant collision between two galaxies more than 38 million light-years apart: at the time of the collision, the disk of gas of one of the galaxies is blown away and will eventually form a ring outside of the galaxy. The simulations allowed the identification of the two galaxies which collided: NGC 3384, one of the galaxies at the center of the Leo group, and M96, a massive spiral galaxy at the periphery of the group. They also gave the date of the collision: more than a billion years ago!

The gas in the Leo ring is definitely not primordial. The hunt for primordial gas is still open!

Posted on by Nancy Atkinson

Where In The Universe #110

It’s time once again for another Where In The Universe Challenge. Test your visual knowledge of the cosmos by naming where in the Universe this image was taken and give yourself extra points if you can name the spacecraft/telescope responsible for this picture. Post your guesses in the comments section, and check back on later at this same post to find the answer. To make this challenge fun for everyone, please don’t include links or extensive explanations with your answer. Good luck!

UPDATE: The answer has now been posted below.

This is a composite image from the Chandra X-Ray Telescope of one of the many star-forming regions in W3, called W3 Main. The green and blue represent lower and higher-energy X-rays, respectively, while red shows optical emission. There are hundreds of X-ray sources here, and these bright point-like objects are an extensive population of several hundred young stars, many of which were not found in earlier infrared studies.

Find out more about this image at the Chandra website.

Posted on by Nancy Atkinson

R Coronae Australis: A Cosmic Watercolor

The nearby star-forming region around the star R Coronae Australis imaged by the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile.

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From an ESO press release:

This magnificent view of the region around the star R Coronae Australis was created from images taken with the Wide Field Imager (WFI) at ESO’s La Silla Observatory in Chile. R Coronae Australis lies at the heart of a nearby star-forming region and is surrounded by a delicate bluish reflection nebula embedded in a huge dust cloud. The image reveals surprising new details in this dramatic area of sky.

The star R Coronae Australis lies in one of the nearest and most spectacular star-forming regions. This portrait was taken by the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. The image is a combination of twelve separate pictures taken through red, green and blue filters.

This image shows a section of sky that spans roughly the width of the full Moon. This is equivalent to about four light-years at the distance of the nebula, which is located some 420 light-years away in the small constellation of Corona Australis (the Southern Crown). The complex is named after the star R Coronae Australis, which lies at the centre of the image. It is one of several stars in this region that belong to the class of very young stars that vary in brightness and are still surrounded by the clouds of gas and dust from which they formed.

The intense radiation given off by these hot young stars interacts with the gas surrounding them and is either reflected or re-emitted at a different wavelength. These complex processes, determined by the physics of the interstellar medium and the properties of the stars, are responsible for the magnificent colours of nebulae. The light blue nebulosity seen in this picture is mostly due to the reflection of starlight off small dust particles. The young stars in the R Coronae Australis complex are similar in mass to the Sun and do not emit enough ultraviolet light to ionise a substantial fraction of the surrounding hydrogen. This means that the cloud does not glow with the characteristic red colour seen in many star-forming regions.

The huge dust cloud in which the reflection nebula is embedded is here shown in impressively fine detail. The subtle colours and varied textures of the dust clouds make this image resemble an impressionist painting. A prominent dark lane crosses the image from the centre to the bottom left. Here the visible light emitted by the stars that are forming inside the cloud is completely absorbed by the dust. These objects could only be detected by observing at longer wavelengths, by using a camera that can detect infrared radiation.

R Coronae Australis itself is not visible to the unaided eye, but the tiny, tiara-shaped constellation in which it lies is easily spotted from dark sites due to its proximity on the sky to the larger constellation of Sagittarius and the rich star clouds towards the centre of our own galaxy, the Milky Way.

For more images and videos see this ESO webpage.

Posted on by Nancy Atkinson

Red Bull Stratos Update: Breaking the Speed of Sound in Freefall

Baumgartner during a test flight. Credit: Red Bull Stratos

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Here’s an update on the Red Bull Stratos project, where skydiver Felix Baumgartner will attempt to break the speed of sound during freefall. (Read our preview article). Baumgartner and the project’s aeronautic’s experts recently conducted the latest round of high-altitude test jumps and step-off procedure tests. Baumgartner himself reports feeling both satisfaction and apprehension while the team prepares to move into a new phase of testing.

During the last week in May 2010, the Red Bull Stratos team conducted three important tests. In the capsule step-off test, conducted at Sage Cheshire Aerospace in Lancaster, California, the capsule dangled from a 40,000-ton crane to simulate its suspension from the balloon flight train, with Baumgartner practicing his movements inside, exiting and stepping off. The purpose was to determine how the vessel reacts to Baumgartner’s motion, and whether those reactions could compromise his descent. Even a relatively gentle tumble created by imprecise step-off could not only hinder Baumgartner’s ability to break the sound barrier but also suddenly devolve into a dangerously rapid “flat spin” once he encounters a level of increased air density.

Felix Baumgartner during a test flight. Credit: Red Bull Stratos

Next, a group of pre-eminent aerospace experts and test pilots – including Joe Kittinger, who holds the records Baumgartner will try to break – gathered in a deserted Palmdale fairground to witness something they’d never seen during all their combined years of experience: a bungee jump in a pressurized space suit and helmet. After multiple jumps from a crane basket suspended 200 feet above the ground, Baumgartner’s exit technique had evolved into something that one team member described as “perfect.”

The finale to the week of testing was a series of skydives over the desert in Perris, California, reaching approximately 26,000 feet. This test, conducted on May 27, 2010, was the first in a fully pressurized suit and was a follow-up to a similar day of flights in early spring. Baumgartner had been frustrated by the awkwardness of his equipment, especially by the way his chest pack – a vital technology hub for the descent – jammed his helmet and inhibited movement on descent and blocked his vision while landing. Objectives were to get a clean step-off from the rear-exit airplane; assess controllability and various body positions in the fully pressurized suit; experience suit deflation upon descent; and test a new chest pack system that allows one side to move out of Baumgartner’s line of sight so he can spot his landing. Baumgartner’s technique and the improved equipment worked so quite well, so the team was able to accomplish all objectives.

Source: Red Bull Stratos

Posted on by Nancy Atkinson

Finding the Origin of Milky Way’s Ancient Stars

Simulation showing a Milky Way-like galaxy around five billion years ago, when most satellite galaxy collisions were happening. Credit: Andrew Cooper, John Helly (Durham University)

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From the Royal Astronomical Society

Many of the Milky Way’s ancient stars are remnants of other smaller galaxies torn apart by violent galactic collisions around five billion years ago, according to researchers at Durham University, who publish their results in a new paper in the journal Monthly Notices of the Royal Astronomical Society.

Scientists at Durham’s Institute for Computational Cosmology and their collaborators at the Max Planck Institute for Astrophysics, in Germany, and Groningen University, in Holland, ran huge computer simulations to recreate the beginnings of our Galaxy.

The simulations revealed that the ancient stars, found in a stellar halo of debris surrounding the Milky Way, had been ripped from smaller galaxies by the gravitational forces generated by colliding galaxies.

Cosmologists predict that the early Universe was full of small galaxies which led short and violent lives. These galaxies collided with each other leaving behind debris which eventually settled into more familiar looking galaxies like the Milky Way.

The researchers say their finding supports the theory that many of the Milky Way’s ancient stars had once belonged to other galaxies instead of being the earliest stars born inside the Galaxy when it began to form about 10 billion years ago.

Simulation showing the stellar halo of a Milky Way-like galaxy in the present day. Credit: Andrew Cooper (Durham University)

Lead author Andrew Cooper, from Durham University’s Institute for Computational Cosmology, said: “Effectively we became galactic archaeologists, hunting out the likely sites where ancient stars could be scattered around the galaxy.

“Our simulations show how different relics in the Galaxy today, like these ancient stars, are related to events in the distant past.

“Like ancient rock strata that reveal the history of Earth, the stellar halo preserves a record of a dramatic primeval period in the life of the Milky Way which ended long before the Sun was born.”

The computer simulations started from shortly after the Big Bang, around 13 billion years ago, and used the universal laws of physics to simulate the evolution of dark matter and the stars.

These simulations are the most realistic to date, capable of zooming into the very fine detail of the stellar halo structure, including star “streams” – which are stars being pulled from the smaller galaxies by the gravity of the dark matter.

One in one hundred stars in the Milky Way belong to the stellar halo, which is much larger than the Galaxy’s familiar spiral disk. These stars are almost as old as the Universe.

Professor Carlos Frenk, Director of Durham University’s Institute for Computational Cosmology, said: “The simulations are a blueprint for galaxy formation.

“They show that vital clues to the early, violent history of the Milky Way lie on our galactic doorstep.

“Our data will help observers decode the trials and tribulations of our Galaxy in a similar way to how archaeologists work out how ancient Romans lived from the artefacts they left behind.”

The research is part of the Aquarius Project, which uses the largest supercomputer simulations to study the formation of galaxies like the Milky Way and was partly funded by the UK’s Science and Technology Facilities Council (STFC).

Aquarius was carried out by the Virgo Consortium, involving scientists from the Max Planck Institute for Astrophysics in Germany, the Institute for Computational Cosmology at Durham University, UK, the University of Victoria in Canada, the University of Groningen in the Netherlands, Caltech in the USA and Trieste in Italy.

Durham’s cosmologists will present their work to the public as part of the Royal Society’s 350th anniversary ‘See Further’ exhibition, held at London’s Southbank Centre until July 4th.

Posted on by Nancy Atkinson

Zapping Titan-Like Atmosphere with UV Creates Life Precursors

Which Planets Have Rings?
This colorized image taken by the Cassini orbiter, shows Saturn's A and F rings, the small moon Epimetheus and Titan, the planet's largest moon. Credit: NASA/JPL/Space Science Institute

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From the University of Arizona

The first experimental evidence showing how atmospheric nitrogen can be incorporated into organic macromolecules is being reported by a University of Arizona team. The finding indicates what organic molecules might be found on Titan, the moon of Saturn that scientists think is a model for the chemistry of pre-life Earth.

Earth and Titan are the only known planetary-sized bodies that have thick, predominantly nitrogen atmospheres, said Hiroshi Imanaka, who conducted the research while a member of UA’s chemistry and biochemistry department.

How complex organic molecules become nitrogenated in settings like early Earth or Titan’s atmosphere is a big mystery, Imanaka said.

“Titan is so interesting because its nitrogen-dominated atmosphere and organic chemistry might give us a clue to the origin of life on our Earth,” said Imanaka, now an assistant research scientist in the UA’s Lunar and Planetary Laboratory. “Nitrogen is an essential element of life.”

However, not just any nitrogen will do. Nitrogen gas must be converted to a more chemically active form of nitrogen that can drive the reactions that form the basis of biological systems.

Imanaka and Mark Smith converted a nitrogen-methane gas mixture similar to Titan’s atmosphere into a collection of nitrogen-containing organic molecules by irradiating the gas with high-energy UV rays. The laboratory set-up was designed to mimic how solar radiation affects Titan’s atmosphere.

Most of the nitrogen moved directly into solid compounds, rather than gaseous ones, said Smith, a UA professor and head of chemistry and biochemistry. Previous models predicted the nitrogen would move from gaseous compounds to solid ones in a lengthier stepwise process.

Titan looks orange in color because a smog of organic molecules envelops the planet. The particles in the smog will eventually settle down to the surface and may be exposed to conditions that could create life, said Imanaka, who is also a principal investigator at the SETI Institute in Mountain View, Calif.

However, scientists don’t know whether Titan’s smog particles contain nitrogen. If some of the particles are the same nitrogen-containing organic molecules the UA team created in the laboratory, conditions conducive to life are more likely, Smith said.

Laboratory observations such as these indicate what the next space missions should look for and what instruments should be developed to help in the search, Smith said.

Imanaka and Smith’s paper, “Formation of nitrogenated organic aerosols in the Titan upper atmosphere,” is scheduled for publication in the Early Online edition of the Proceedings of the National Academy of Sciences the week of June 28. NASA provided funding for the research.

The UA researchers wanted to simulate conditions in Titan’s thin upper atmosphere because results from the Cassini Mission indicated “extreme UV” radiation hitting the atmosphere created complex organic molecules.

Therefore, Imanaka and Smith used the Advanced Light Source at Lawrence Berkeley National Laboratory’s synchroton in Berkeley, Calif. to shoot high-energy UV light into a stainless steel cylinder containing nitrogen-and-methane gas held at very low pressure.

The researchers used a mass spectrometer to analyze the chemicals that resulted from the radiation.

Simple though it sounds, setting up the experimental equipment is complicated. The UV light itself must pass through a series of vacuum chambers on its way into the gas chamber.

Many researchers want to use the Advanced Light Source, so competition for time on the instrument is fierce. Imanaka and Smith were allocated one or two time slots per year, each of which was for eight hours a day for only five to 10 days.

For each time slot, Imanaka and Smith had to pack all the experimental equipment into a van, drive to Berkeley, set up the delicate equipment and launch into an intense series of experiments. They sometimes worked more than 48 hours straight to get the maximum out of their time on the Advanced Light Source. Completing all the necessary experiments took years.

It was nerve-racking, Imanaka said: “If we miss just one screw, it messes up our beam time.”

At the beginning, he only analyzed the gases from the cylinder. But he didn’t detect any nitrogen-containing organic compounds.

Imanaka and Smith thought there was something wrong in the experimental set-up, so they tweaked the system. But still no nitrogen.

“It was quite a mystery,” said Imanaka, the paper’s first author. “Where did the nitrogen go?”

Finally, the two researchers collected the bits of brown gunk that gathered on the cylinder wall and analyzed it with what Imanaka called “the most sophisticated mass spectrometer technique.”

Imanaka said, “Then I finally found the nitrogen!”

Imanaka and Smith suspect that such compounds are formed in Titan’s upper atmosphere and eventually fall to Titan’s surface. Once on the surface, they contribute to an environment that is conducive to the evolution of life.

Posted on by Nancy Atkinson

Opportunity Rover Able to See More Detail of Endeavour Crater

Since the summer of 2008, when NASA's Mars Exploration Rover Opportunity finished two years of studying Victoria Crater, the rover's long-term destination has been the much larger Endeavour Crater to the southeast. Credit: JPL

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From a JPL press release:

Mars rover team members have begun informally naming features around the rim of Endeavour Crater, as they develop plans to investigate that destination when NASA’s Opportunity rover arrives there after many more months of driving. A new, super-resolution view of a portion of Endeavour’s rim reveals details that were not discernible in earlier images from the rover. Several high points along the rim can be correlated with points discernible from orbit.

Super-resolution is an imaging technique combining information from multiple pictures of the same target to generate an image with a higher resolution than any of the individual images.

Endeavour has been the team’s long-term destination for Opportunity since the summer of 2008, when the rover finished two years of studying Victoria Crater. By the spring of 2010, Opportunity had covered more than a third of the charted, 19-kilometer (12-mile) route from Victoria to Endeavour and reached an area with a gradual, southward slope offering a view of Endeavour’s elevated rim.

After the rover team chose Endeavour as a long-term destination, the goal became even more alluring when observations with the Compact Reconnaissance Imaging Spectrometer for Mars, on NASA’s Mars Reconnaissance Orbiter, found clay minerals exposed at Endeavour. Clay minerals, which form under wet conditions, have been found extensively on Mars from orbit, but have not been examined on the surface. Additional observations with that spectrometer are helping the rover team choose which part of Endeavour’s rim to visit first with Opportunity.

The team is using the theme of names of places visited by British Royal Navy Capt. James Cook in his 1769-1771 Pacific voyage in command of H.M.S. Endeavour for informal names of sites at Endeavour Crater. Points visible in the super-resolution view from May 12 include “Cape Tribulation” and “Cape Dromedary.”

See more images and info on the names of the different features at Stu Atkinson’s “Road to Endeavour” blog.

Posted on by Nancy Atkinson

Earth’s Gravity Seen in HD

New map of Earth's gravity field from GOCE. Credit: ESA

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The sleek and sexy-looking GOCE satellite has provided a new, finely detailed look at Earth’s gravity – in high definition. This is the first-ever global gravity model and is based on just two months of data from the low-flying GOCE. “GOCE is delivering where it promised: in the fine spatial scales,” GOCE Mission Manager Rune Floberghagen said. “We have already been able to identify significant improvements in the high-resolution ‘geoid’, and the gravity model will improve as more data become available.”

GOCE stands for Gravity field and steady-state Ocean Circulation Explorer.

The geoid is a measure of the lumps and bumps in Earth’s gravity, and shows how the surface would look if an ocean covered the earth, also known as surface of equal gravitational attraction and mean sea level.
Scientists say it is a crucial reference for accurately measuring ocean circulation, sea-level change and ice dynamics – all affected by climate change.

GOCE in orbit. Credit: ESA

The GOCE team presented their initial data at ESA’s Living Planet Symposium. ESA launched GOCE in March 2009, and the data is from November and December 2009.

“Over continents, and in particular in regions poorly mapped with terrestrial or airborne techniques, we can already conclude that GOCE is changing our understanding of the gravity field,” said Floberghagen. Over major parts of the oceans, the situation is even clearer, as the marine gravity field at high spatial resolution is for the first time independently determined by an instrument of such quality.”

This will greatly improve our knowledge and understanding of the Earth’s internal structure, and will be used as a much-improved reference for ocean and climate studies, including sea-level changes, oceanic circulation and ice caps dynamics survey. Numerous applications are expected in climatology, oceanography and geophysics.

“The computed global gravity field looks very promising. We can already see that important new information will be obtained for large areas of South America, Africa, Himalaya, South-East Asia and Antarctica,” said Prof. Reiner Rummel from Technische Universität München, Chairman of the GOCE Mission Advisory Group. “With each two-month cycle of data, the gravity model will become more detailed and accurate. I am convinced that the data will be of great interest to various disciplines of Earth sciences.”

The spacecraft can measure accelerations as small as 1 part in 10,000,000,000,000 of the gravity experienced on Earth.

GOCE flies in orbit at just 254.9 km (158 miles) mean altitude – the lowest orbit sustained over a long period by any Earth observation satellite, but the lower the altitude, the better the data.

Anaglyph images created from an ESA video animation of global gravity gradients. A more accurate global map will be generated by ESA's GOCE craft. Credit: ESA and Nathaniel Burton Bradford.

The residual air at this low altitude causes the orbit of a standard satellite to decay very rapidly. So, to counteract the drag, the satellite fires an ion thruster using xenon gas, maintaining its orbit. This ensures the gravity sensors are flying as though they are in pure freefall, so they pick up only gravity readings and not the disturbing effects from other forces.

To obtain clean gravity readings, there can be no disturbances from moving parts, so the entire satellite is a single extremely sensitive measuring device.

The new map is just from the first data, and more information will be forthcoming. In May, ESA made available the first set of gravity gradients and ‘high-low satellite-to-satellite tracking’ to scientific and non-commercial users – and much more will come in the following months.

Souces: ESA, BBC

Posted on by Nancy Atkinson

This Week in Space with Miles O’Brien

An exclusive interview with SpaceX’s safety officer delves into the post-flight review of the Falcon 9 test launch. Also this week, the final shuttle missions slip out and John Glenn enters debate about the space program’s future. Subscribe on iTunes to This Week in Space.

Posted on by Steve Nerlich

Astronomy Without A Telescope – Stellar Archaeology

Artist's impression of Population 3 stars born over 13 billion years ago - the earliest, oldest and presumably now extinct star types. Credit: NASA.

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Although, as we look further and deeper into the sky, we are always looking into the past – there are other ways of gaining information about the universe’s ancient history. Low mass, low metal stars may be remnants of the early universe and carry valuable information about the environment of that early universe.

The logic of stellar archaeology involves tracking generations of stars back to the very first stars seen in our universe. Stars born in recent eras, say within the last five or six billion years, we call Population I stars – which includes our Sun. These stars were born from an interstellar medium (i.e. gas clouds etc) that had been seeded by the death throes of a previous generation of stars we call Population II stars.

Population II stars were born from an interstellar medium that existed maybe 12 or 13 billion years ago – and which had been seeded by the death throes of Population III stars, the first stars ever seen in our universe.

And when I say death throes seeding the interstellar medium this includes average sized stars blowing off a planetary nebula at the end of their red giant phase – or bigger stars exploding as supernovae.

So for example, the low metal spectral signature of HE 0107-5240 matches that predicted for a very early low mass Population II star built from the end-products of a Population III supernova.

This is about as close as we can get gathering any information about Population III stars. Telescopes that can look deeper into space (and hence look further back in time) may eventually spot one – but it’s unlikely that any still exist. Theory has it that Population III stars formed from a homogenous interstellar medium of hydrogen and helium. The homogeneity of this medium meant that any stars that formed were all massive – in the order of hundreds of solar masses.

Stars of this scale, not only have short life spans but explode with such a force that the star literally blows itself to bits as a ‘pair-instability’ supernova – leaving no remnant neutron star or black hole behind. Supernova SN2006gy was probably a pair-instability supernova – mimicking the last gasps of Population III stars that lived more than 13 billion years ago.

Recipe for a pair instability supernova. In very massive stars, gamma rays radiating from the core become so energetic that they can undergo pair production after interaction with a nucleus. Essentially, the gamma ray creates a paired particle and antiparticle (commonly an electron and a positron). The loss of radiation pressure as gamma rays convert to particles results in gravitational collapse of the star's core - and kaboom! Credit: chandra.harvard.edu

It was only after Population III stars had seeded the interstellar medium with heavier elements that fine structure cooling resulted in disruption of thermal equilibrium and fragmentation of gas clouds – enabling smaller, and hence longer lived, Population II stars to be born.

Around the Milky Way, we can find very old Population II stars in orbiting dwarf galaxies. These stars are also common in the galactic halo and in globular clusters. However, in ‘the guts’ of the galaxy we find lots of young Population I stars.

This all leads to the view that the Milky Way is a gravitational hub nearly as old as the universe itself – which has been steadily growing in size and keeping itself looking young by maintaining a steady diet of ancient dwarf galaxies – which, deprived of such a diet, have remained largely unchanged since their formation in the early universe.

Further reading:

A. Frebel. Stellar Archaeology – Exploring the Universe with Metal-Poor Stars http://arxiv4.library.cornell.edu/abs/1006.2419