Posted on by Fraser Cain

Three Neptunes Orbiting Another Star

An artist’s impression of a planetary system around HD 69830. Image credit: ESO. Click to enlarge
Astronomers have discovered a nearby star that’s home to three Neptune-sized planets; no super-Jupiters here. The star, HD 69830, is located 41 light-years away in the constellation of Puppis. With magnitude 5.95, it’s just possible to see with the unaided eye. The discovery was made using the European Southern Observatory’s 3.6 metre telescope at La Silla in Chile. The planets orbit their star in 8.67, 31.6 and 197 days respectively.

Using the ultra-precise HARPS spectrograph on ESO’s 3.6-m telescope at La Silla (Chile), a team of European astronomers have discovered that a nearby star is host to three Neptune-mass planets. The innermost planet is most probably rocky, while the outermost is the first known Neptune-mass planet to reside in the habitable zone. This unique system is likely further enriched by an asteroid belt.

“For the first time, we have discovered a planetary system composed of several Neptune-mass planets”, said Christophe Lovis, from the Geneva Observatory and lead-author of the paper presenting the results.

During more than two years, the astronomers carefully studied HD 69830, a rather inconspicuous nearby star slightly less massive than the Sun. Located 41 light-years away towards the constellation of Puppis (the Stern), it is, with a visual magnitude of 5.95, just visible with the unaided eye. The astronomers’ precise radial-velocity measurements allowed them to discover the presence of three tiny companions orbiting their parent star in 8.67, 31.6 and 197 days.

“Only ESO’s HARPS instrument installed at the La Silla Observatory, Chile, made it possible to uncover these planets”, said Michel Mayor, also from Geneva Observatory, and HARPS Principal Investigator. “Without any doubt, it is presently the world’s most precise planet-hunting machine”.

The detected velocity variations are between 2 and 3 metres per second, corresponding to about 9 km/h! That’s the speed of a person walking briskly. Such tiny signals could not have been distinguished from ‘simple noise’ by most of today’s available spectrographs.

The newly found planets have minimum masses between 10 and 18 times the mass of the Earth. Extensive theoretical simulations favour an essentially rocky composition for the inner planet, and a rocky/gas structure for the middle one. The outer planet has probably accreted some ice during its formation, and is likely to be made of a rocky/icy core surrounded by a quite massive envelope. Further calculations have also shown that the system is in a dynamically stable configuration.

The outer planet also appears to be located near the inner edge of the habitable zone, where liquid water can exist at the surface of rocky/icy bodies. Although this planet is probably not Earth-like due to its heavy mass, its discovery opens the way to exciting perspectives.

“This alone makes this system already exceptional”, said Willy Benz, from Bern University, and co-author. “But the recent discovery by the Spitzer Space Telescope that the star most likely hosts an asteroid belt is adding the cherry to the cake.”

With three roughly equal-mass planets, one being in the habitable zone, and an asteroid belt, this planetary system shares many properties with our own solar system.

“The planetary system around HD 69830 clearly represents a Rosetta stone in our understanding of how planets form”, said Michel Mayor. “No doubt it will help us better understand the huge diversity we have observed since the first extra-solar planet was found 11 years ago.”

Original Source: ESO News Release

Posted on by Fraser Cain

Before the Big Bang

Researchers have developed a model of a shrinking universe that existed prior to the Big Bang. Image credit: NASA. Click to enlarge
The Big Bang describes how the Universe began as a single point 13.7 billion years ago, and has been expanding ever since, but it doesn’t explain what happened before that. Researchers from Penn State University believe that there should be traces of evidence in our current universe that could used to look back before the Big Bang. According to their research, there was a contracting universe with similar space-time geometry to our expanding universe. The universe collapsed and then “bounced” as the Big Bang.

According to Einstein’s general theory of relativity, the Big Bang represents The Beginning, the grand event at which not only matter but space-time itself was born. While classical theories offer no clues about existence before that moment, a research team at Penn State has used quantum gravitational calculations to find threads that lead to an earlier time. “General relativity can be used to describe the universe back to a point at which matter becomes so dense that its equations don’t hold up,” says Abhay Ashtekar, Holder of the Eberly Family Chair in Physics and Director of the Institute for Gravitational Physics and Geometry at Penn State. “Beyond that point, we needed to apply quantum tools that were not available to Einstein.” By combining quantum physics with general relativity, Ashtekar and two of his post-doctoral researchers, Tomasz Pawlowski and Parmpreet Singh, were able to develop a model that traces through the Big Bang to a shrinking universe that exhibits physics similar to ours.

In research reported in the current issue of Physical Review Letters, the team shows that, prior to the Big Bang, there was a contracting universe with space-time geometry that otherwise is similar to that of our current expanding universe. As gravitational forces pulled this previous universe inward, it reached a point at which the quantum properties of space-time cause gravity to become repulsive, rather than attractive. “Using quantum modifications of Einstein’s cosmological equations, we have shown that in place of a classical Big Bang there is in fact a quantum Bounce,” says Ashtekar. “We were so surprised by the finding that there is another classical, pre-Big Bang universe that we repeated the simulations with different parameter values over several months, but we found that the Big Bounce scenario is robust.”

While the general idea of another universe existing prior to the Big Bang has been proposed before, this is the first mathematical description that systematically establishes its existence and deduces properties of space-time geometry in that universe.

The research team used loop quantum gravity, a leading approach to the problem of the unification of general relativity with quantum physics, which also was pioneered at the Penn State Institute of Gravitational Physics and Geometry. In this theory, space-time geometry itself has a discrete ‘atomic’ structure and the familiar continuum is only an approximation. The fabric of space is literally woven by one-dimensional quantum threads. Near the Big-Bang, this fabric is violently torn and the quantum nature of geometry becomes important. It makes gravity strongly repulsive, giving rise to the Big Bounce.

“Our initial work assumes a homogenous model of our universe,” says Ashtekar. “However, it has given us confidence in the underlying ideas of loop quantum gravity. We will continue to refine the model to better portray the universe as we know it and to better understand the features of quantum gravity.”

The research was sponsored by the National Science Foundation, the Alexander von Humboldt Foundation, and the Penn State Eberly College of Science.

Original Source: PSU News Release

Posted on by Fraser Cain

Searching For Crater Chains on the Earth

Aorounga impact crater. Image credit: NASA/JPL. Click to enlarge
Comet 73P/Schwassmann Wachmann 3 is a beautiful sight in the night sky, especially now that it’s fractured into many pieces. There’s evidence for these kinds of impacts on several planets and moons in the Solar System, and astronomers watched 23 fragments of Comet Shoemaker-Levy 9 smash into Jupiter in 1993. What if a string of comet fragments like this hit the Earth? There are only a few examples of these kinds of impacts on the Earth; unfortunately, wind, rain and tectonic forces work to hide the evidence.

As the fragments of shattered comet 73P/Schwassmann Wachmann 3 glide harmlessly past Earth this month in full view of backyard telescopes, onlookers can’t help but wonder, what if a comet like that didn’t miss, but actually hit our planet?

For the answer to that question, we look to the Sahara desert.

In a remote windswept area named Aorounga, in Chad, there are three craters in a row, each about 10 km in diameter. “We believe this is a ‘crater chain’ formed by the impact of a fragmented comet or asteroid about 400 million years ago in the Late Devonian period,” explains Adriana Ocampo of NASA headquarters.

Ocampo and colleagues discovered the chain in 1996. The main crater “Aorounga South” had been known for many years?it sticks out of the sand and can be seen from airplanes and satellites. But a second and possibly third crater were buried. They lay hidden until radar onboard the space shuttle (SIR-C) penetrated the sandy ground, revealing their ragged outlines.

“Here on Earth, crater chains are rare,” says Ocampo, but they are common in other parts of the solar system.

The first crater chains were discovered by NASA’s Voyager 1 spacecraft. In 1979 when the probe flew past Jupiter’s moon Callisto, cameras recorded a line of craters, at least fifteen long, evenly spaced as if someone had strafed the moon with a Gatling gun. Eventually, eight chains were found on Callisto and three more on Ganymede.

At first the chains were a puzzle. Were they volcanic? Had an asteroid skipped along the surface of Callisto like a stone skipping across a pond?

The mystery was solved in 1993 with the discovery of Comet Shoemaker-Levy 9. SL-9 was not a single comet, but a “string of pearls,” a chain of 21 comet fragments created a year earlier when Jupiter’s gravity ripped the original comet apart. SL-9 struck back in 1994, crashing into Jupiter. Onlookers watched titanic explosions in the giant planet’s atmosphere, and it only took a little imagination to visualize the result if Jupiter had had a solid surface: a chain of craters.

Astronomers have since realized that fragmented comets and rubble-pile asteroids are commonplace. Comets fall apart rather easily; sunlight alone can shatter their fragile nuclei. Furthermore, there is mounting evidence that many seemingly solid asteroids are assemblages of boulders, dust and rock held together by feeble gravity. When these things hit, they make chains.

In 1994, researchers Jay Melosh and Ewen Whitaker announced their finding of two crater chains on the Moon. One, on the floor of the crater Davy, is spectacular–an almost perfect line of 23 pockmarks each a few miles in diameter. This proved that crater chains exist in the Earth-Moon system.

But where on Earth are they?

Earth tends to hide its craters. “Wind and rain erode them, sediments fill them in, and the tectonic recycling of Earth’s crust completely obliterates them,” says Ocampo. On the Moon, there are millions of well-preserved craters. On Earth, “so far we’ve managed to find only about 174.”

Sounds like a job for Google. Seriously. Amateur astronomer Emilio Gonzalez pioneered the technique in March 2006. “I use Google Earth,” he explains. Google Earth is a digital map of our planet made of stitched-together satellite images. You can zoom in and out, fly around and inspect the landscape in impressive detail. It’s a bit like a video game-except it is real.

Gonzalez began by calling up Kebira impact crater in Libya?the Sahara’s largest. It was so easy to see, he recalls, “I decided to look around for more.” Minutes later he was “flying” over the Libya-Chad border when another crater appeared. And then another. They both had multiple rings and a central peak, the telltale splash of a high-energy impact. “It couldn’t be this easy!” he marveled.

But it was. At least one of the craters had never been catalogued before, and both, almost incredibly, lined up with the Aorounga crater 200 km away: map. In less than 30 minutes, Gonzalez had found two good impact candidates and possibly multiplied the length of the Aorounga chain. Hours of additional searching produced no new results. “Beginner’s luck,” he laughs. (If you would like to hunt for your own craters online, Gonzalez offers these tips.)

Ocampo doubts that these new craters are related to Aorounga. “They don’t appear to be the same age.” But she can’t rule it out either.

“We need to do some fieldwork,” she says. To prove a crater is a crater-and not, say, a volcano-researchers must visit the site to look for signs of extraterrestrial impact such as “shatter cones” and other minerals forged by intense heat and pressure. This kind of geological study can also reveal the age of an impact site, marking it as part of a chain or an independent event.

Answers may have to wait. Civil war in Chad and the possibility of war between Chad and Sudan prevent scientists from mounting an expedition. Meanwhile, researchers are scrutinizing candidate chains in Missouri and Spain. Although those sites are more accessible than Chad, researchers still can’t decide if they are chains or not. It’s difficult work.

Ocampo believes it’s worth the effort. “The history of Earth is shaped by impacts,” she says. “Crater chains can tell us important things about our planet.”

And so the search goes on.

Original Source: NASA News Release

Posted on by Fraser Cain

Galaxy Clusters Have Different Supernova Yields

Clusters of galaxies as seen by XMM-Newton. Image credit: ESA. Click to enlarge
Galaxy clusters are the largest objects in the Universe. Each cluster can contain hundreds or even thousands of galaxies held together by gravity. These clusters are filled with hot gas, emitting a tremendous amount of X-ray radiation. ESA’s XMM-Newton observatory recently watched two galaxy clusters enabling astronomers to learn that these clusters have higher quantities of Type 1a supernovae – exploding white dwarf stars – than our own galaxy.

Deep observations of two X-ray bright clusters of galaxies with ESA’s XMM-Newton satellite allowed a group of international astronomers to measure their chemical composition with an unprecedented accuracy. Knowing the chemical composition of galaxy clusters is of crucial importance to understanding the origin of chemical elements in the Universe.

Clusters, or conglomerates, of galaxies are the largest objects in the Universe. By looking at them through optical telescopes it is possible to see hundreds or even thousands of galaxies occupying a volume a few million light years across. However, such telescopes only reveal the tip of the iceberg. In fact most of the atoms in galaxy clusters are in the form of hot gas emitting X-ray radiation, with the mass of the hot gas five times larger than the mass in the cluster’s galaxies themselves.

Most of the chemical elements produced in the stars of galaxy clusters – expelled into the surrounding space by supernova explosions and by stellar winds – become part of the hot X-ray emitting gas. Astronomers divide supernovae into two basic types: ‘core collapse’ and ‘Type Ia’ supernovae. The ‘core collapse’ supernovae originate when a star at the end of its life collapses into a neutron star or a black hole. These supernovae produce lots of oxygen, neon and magnesium. The Type Ia supernovae explode when a white dwarf star consuming matter from a companion star becomes too massive and completely disintegrates. This type produces lots of iron and nickel.

Respectively in November 2002 and August 2003, and for one and a half day each time, XMM-Newton’s made deep observations of the two galaxy clusters called ‘Sersic 159-03’ and ‘2A 0335+096’. Thanks to these data the astronomers could determine the abundances of nine chemical elements in the clusters ‘plasma’ ??bf? a gas containing charged particles such as ions and electrons.

These elements include oxygen, iron, neon, magnesium, silicon, argon, calcium, nickel, and – detected for the first time ever in a galaxy cluster – chromium. “Comparing the abundances of the detected elements to the yields of supernovae calculated theoretically, we found that about 30 percent of the supernovae in these clusters were exploding white dwarfs (‘Type Ia’) and the rest were collapsing stars at the end of their lives (‘core collapse’),” said Norbert Werner, from the SRON Netherlands Institute for Space Research (Utrecht, Netherlands) and one of the lead authors of these results.

“This number is in between the value found for our own Galaxy (where Type Ia supernovae represent about 13 percent of the supernovae ‘population’) and the current frequency of supernovae events as determined by the Lick Observatory Supernova Search project (according to which about 42 percent of all observed supernovae are Type Ia),” he continued.

The astronomers also found that all supernova models predict much less calcium than what is observed in clusters and that the observed nickel abundance cannot be reproduced by these models. These discrepancies indicate that that the details of supernova enrichment is not yet clearly understood. Since clusters of galaxies are believed to be fair samples of the Universe, their X-ray spectroscopy can help to improve the supernova models.

The spatial distribution of elements across a cluster also holds information about the history of clusters themselves. The distribution of elements in 2A 0335+096 indicates an ongoing merger. The distribution of oxygen and iron across Sersic 159-03 indicates that while most of the enrichment by the core collapse supernovae happened long time ago, Type Ia supernovae still continue to enrich the hot gas by heavy elements especially in the core of the cluster.

Original Source: ESA Portal

Posted on by Fraser Cain

Iapetus’ Darker Side

Saturn’s moon Iapetus. Image credit: NASA/JPL/SSI. Click to enlarge
This Cassini image shows the darker side of Saturn’s moon Iapetus. Scientists aren’t sure why, but Iapetus’ leading hemisphere is much darker than its trailing hemisphere. At the top of the image, it’s possible to see a large impact basin 400 km (250 miles) wide. Cassini took this photograph on April 4, 2006, at a distance of approximately 1.4 million kilometers (900,000 miles) from Iapetus.

A distant glimpse of Iapetus reveals details within the dark terrain of Cassini Regio, including an impact basin at top that is roughly 400 kilometers (250 miles) wide.

Researchers remain unsure about the mechanism that has darkened the leading hemisphere.

This view looks toward the southern hemisphere on the leading side of Iapetus (1,468 kilometers, or 912 miles across). North is up.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 4, 2006, at a distance of approximately 1.4 million kilometers (900,000 miles) from Iapetus. The image scale is 9 kilometers (6 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Twin Supernovae in NGC 3190

Spiral galaxy NGC 3190. Image credit: ESO. Click to enlarge
Supernovae are rare enough, but astronomers discovered two going off in galaxy NGC 3190 at the same time. NGC 3190 is a large spiral galaxy that we see nearly edge on. Its shape has been warped through interactions between other nearby galaxies, and it has an active galactic nucleus. Astronomers uncovered one supernova in the southeastern part in March 2002, and then another team uncovered a second supernova on the other side two months later. This photograph of NGC 3190 was taken by ESO’s Very Large Telescope.

his beautiful edge-on spiral galaxy with tightly wound arms and a warped shape that makes it resemble a gigantic potato crisp lies in the constellation Leo (‘the Lion’) and is approximately 70 million light years away. It is the dominant member of a small group of galaxies known as Hickson 44, named after the Canadian astronomer, Paul Hickson. In addition to NGC 3190, Hickson 44 consists of one elliptical and two spiral galaxies. These are, however, slightly out of the field of view and therefore not visible here.

In 1982, Hickson published a catalogue of over 400 galaxies found in compact, physically-related groups of typically 4 to 5 galaxies per group (see the image of Robert’s Quartet in ESO PR Photo 34/05 as another example). Such compact groups allow astronomers to study how galaxies dynamically affect each other, and help them test current ideas on how galaxies form. One idea is that compact groups of galaxies, such as Hickson 44, merge to form a giant elliptical galaxy, such as NGC 1316 (see ESO PR 17/00).

Indeed, signs of tidal interactions are visible in the twisted dust lane of NGC 3190. This distortion initially misled astronomers into assigning a separate name for the southwestern side, NGC 3189, although NGC 3190 is the favoured designation.

NGC 3190 has an ‘Active Galactic Nucleus’, and as such, the bright, compact nucleus is thought to host a supermassive black hole.

In March 2002, a new supernova (SN 2002bo) was found in between the ‘V’ of the dust lanes in the southeastern part of NGC 3190. It was discovered independently by the Brazilian and Japanese amateur astronomers, Paulo Cacella and Yoji Hirose. SN 2002bo was caught almost two weeks before reaching its maximum brightness, allowing astronomers to study its evolution. It has been the subject of intense monitoring by a world-wide network of telescopes. The conclusion was that SN 2002bo is a rather unusual Type Ia supernova. The image presented here was taken in March 2003, i.e. about a year after the maximum of the supernova which is 50 times fainter on the image than a year before.

While observing SN 2002bo in May 2002, a group of Italian astronomers discovered another supernova, SN 2002cv, on the other side of NGC 3190. Two supernovae of this type appearing nearly simultaneously in the same galaxy is a rare event, as normally astronomers expect only one such event per century in a galaxy. SN 2002cv was best visible at infrared wavelengths as it was superimposed on the dust lane of NGC 3190, and therefore hidden by a large quantity of dust. In fact, this supernova holds the record for the most obscured Type Ia event.

The image was obtained with a total exposure time of 14 minutes only. Yet, with the amazing power of the Very Large Telescope, it reveals a large zoo of galaxies of varying morphologies. How many can you find?

Original Source: ESO News Release

Posted on by Fraser Cain

Comet is Bright With X-Rays

NASA’s Swift captured this image of 73P/Schwassmann-Wachmann 3 as it bypassed the Ring Nebula. Image credit: NASA. Click to enlarge
Comet 73P/Schwassmann-Wachmann 3 is visible in the night sky with even a small backyard telescope, and it will make its closest approach to Earth next week (don’t worry, it’s still really far away). One of the features of this comet, however, is that it’s unusually bright in the X-ray spectrum. Three X-ray observatories will observe the comet in the coming weeks to determine what it’s made of, and maybe even the composition of the solar wind that causes its tail.

Scientists using NASA’s Swift satellite have detected X-rays from a comet that is now passing the Earth and rapidly disintegrating on what could be its final orbit around the sun.

Swift’s observations provide a rare opportunity to investigate several ongoing mysteries about comets and our solar system, and hundreds of scientists have tuned in to the event.

The comet, called 73P/Schwassmann-Wachmann 3, is visible with even a small, backyard telescope. Peak brightness is expected next week, when it comes within 7.3 million miles of Earth, or about 30 times the distance to the Moon. There is no threat to Earth, however.

This is the brightest comet ever detected in X-rays. The comet is so close that astronomers are hoping to determine not only the composition of the comet but also of the solar wind. Scientists think that atomic particles that comprise the solar wind interact with comet material to produce X-rays, a theory that Swift might prove true.

Three world-class X-ray observatories now in orbit—NASA’s Chandra X-ray Observatory, the European-led XMM-Newton, and the Japanese-led Suzaku—will observe the comet in the coming weeks. Like a scout, Swift has provided information to these larger facilities about what to look for. This type of observation can only take place in the X-ray waveband.

“The Schwassmann-Wachmann comet is a comet like no other,” said Scott Porter of NASA’s Goddard Space Flight Center in Greenbelt, Md., part of the Swift observation team. “During its 1996 passage it broke apart. Now we are tracking about three dozen fragments. The X-rays being produced provide information never before revealed.”

The situation is reminiscent of the Deep Impact probe, which penetrated comet Tempel 1 about a year ago. This time, nature itself has broken the comet. Because Schwassmann-Wachmann 3 is much closer to both the Earth and the sun than Tempel 1 was, it currently appears about 20 times brighter in X-rays. Schwassmann-Wachmann 3 passes Earth about every five years. Scientists could not anticipate how bright it would become in X-rays this time around.

“The Swift observations are amazing,” said Greg Brown of Lawrence Livermore National Laboratory in Livermore, Calif., who led the proposal for Swift observation time. “Because we are viewing the comet in X-rays, we can see many unique features. The combined results of data from several premier orbiting observatories will be spectacular.”

Swift is primarily a gamma-ray burst detector. The satellite also has X-ray and ultraviolet/optical telescopes. Because of its burst-hunting ability to turn rapidly, Swift has been able to track the progress of the fast-moving Schwassmann-Wachmann 3 comet. Swift is the first observatory to simultaneously observe the comet in both ultraviolet light and X-rays. This cross comparison is crucial for testing theories about comets.

Swift and the other three X-ray observatories plan to combine forces to observe Schwassmann-Wachmann 3 closely. Through a technique called spectroscopy, scientists hope to determine the chemical structure of the comet. Already Swift has detected oxygen and hints of carbon. These elements are from the solar wind, not the comet.

Scientists think that X-rays are produced through a process called charge exchange, in which highly (and positively) charged particles from the sun that lack electrons steal electrons from chemicals in the comet. Typical comet material includes water, methane and carbon dioxide. Charge exchange is analogous to the tiny spark seen in static electricity, only at a far greater energy.

By comparing the ratio of X-ray energies emitted, scientists can determine the content of the solar wind and infer the content of the comet material. Swift, Chandra, XMM-Newton and Suzaku each provide complementary capabilities to nail down this tricky measurement. The combination of these observations will provide a time evolution of the X-ray emission of the comet as it navigates through our solar system.

Porter and his colleagues at Goddard and Lawrence Livermore tested the charge exchange theory in an earthbound laboratory in 2003. That experiment, at Livermore’s EBIT-I electron beam ion trap, produced a complex spectrograph of intensity versus X-ray energy for a variety of expected elements in the solar wind and comet. “We are anxious to compare nature’s laboratory to the one we created,” Porter said.

The German-led ROSAT mission, now decommissioned, was the first to detect X-rays from a comet, from Hyakutake in 1996. This was a great surprise. It took about five years before scientists had a suitable explanation for X-ray emission. Now, ten years after Hyakutake, scientists could settle the mystery.

Original Source: NASA News Release

Posted on by Fraser Cain

Biggest 3-D Map of the Universe

A schematic view of the new SDSS three-dimensional map. Image credit: Hogg/SDSS-II collaboration. Click to enlarge
Astronomers from UC Berkeley have created the most comprehensive three-dimensional map of the Universe ever published. Amazingly, this map is merely a slice containing 1/10th of the northern hemisphere. It contains 600,000 galaxies and extends out 5.6 billion light-years into space. This map allows astronomers to study evidence for dark energy – the mysterious force accelerating the expansion of the Universe.

A team of astronomers led by Nikhil Padmanabhan and David Schlegel has published the largest three-dimensional map of the universe ever constructed, a wedge-shaped slice of the cosmos that spans a tenth of the northern sky, encompasses 600,000 uniquely luminous red galaxies, and extends 5.6 billion light-years deep into space, equivalent to 40 percent of the way back in time to the Big Bang.

Schlegel is a Divisional Fellow in the Physics Division of Lawrence Berkeley National Laboratory, and Padmanabhan will join the Lab’s Physics Division as a Chamberlain Fellow and Hubble Fellow in September; presently he is at Princeton University. They and their coauthors are members of the Sloan Digital Sky Survey (SDSS), and have previously produced smaller 3-D maps by using the SDSS telescope in New Mexico to painstakingly collect the spectra of individual galaxies and calculate their distances by measuring their redshifts.

“What’s new about this map is that it’s the largest ever,” says Padmanabhan, “and it doesn’t depend on individual spectra.”

The principal motive for creating large-scale 3-D maps is to understand how matter is distributed in the universe, says Padmanabhan. “The brightest galaxies are like lighthouses – where the light is, is where the matter is.”

Schlegel says that “because this map covers much larger distances than previous maps, it allows us to measure structures as big as a billion light-years across.”

The variations in galactic distribution that constitute visible large-scale structures are directly descended from variations in the temperature of the cosmic microwave background, reflecting oscillations in the dense early universe that have been measured to great accuracy by balloon-borne experiments and the WMAP satellite.

The result is a natural “ruler” formed by the regular variations (sometimes called “baryon oscillations,” with baryons as shorthand for ordinary matter), which repeat at intervals of some 450 million light-years.

“Unfortunately it’s an inconveniently sized ruler,” says Schlegel. “We had to sample a huge volume of the universe just to fit the ruler inside.”

Says Padmanabhan, “Although the universe is 13.7 billion years old, that really isn’t a whole lot of time when you’re measuring with a ruler that’s marked only every 450 million light-years.”

The distribution of galaxies reveals many things, but one of the most important is a measure of the mysterious dark energy that accounts for some three-fourths of the universe’s density. (Dark matter accounts for roughly another 20 percent, while less than 5 percent is ordinary matter of the kind that makes visible galaxies.)

“Dark energy is just the term we use for our observation that the expansion of the universe is accelerating,” Padmanabhan remarks. “By looking at where density variations were at the time of the cosmic microwave background” – only about 300,000 years after the Big Bang – “and seeing how they evolve into a map that covers the last 5.6 billion years, we can see if our estimates of dark energy are correct.”

The new map shows that the large-scale structures are indeed distributed the way current ideas about the accelerating expansion of the universe would suggest. The map’s assumed distribution of dark matter, which although invisible is affected by gravity just like ordinary matter, also conforms to current understanding.

What made the big new 3-D map possible were the Sloan Digital Sky Survey’s wide-field telescope, which covers a three-degree field of view (the full moon is about half a degree), plus the choice of a particular kind of galactic “lighthouse,” or distance marker: luminous red galaxies.

“These are dead, red galaxies, some of the oldest in the universe – in which all the fast-burning stars have long ago burned out and only old red stars are left,” says Schlegel. “Not only are these the reddest galaxies, they’re also the brightest, visible at great distances.”

The Sloan Digital Sky Survey astronomers worked with colleagues on the Australian Two-Degree Field team to average the color and redshift of a sample of 10,000 red luminous galaxies, relating galaxy color to distance. They then applied these measurements to 600,000 such galaxies to plot their map.

Padmanabhan concedes that “there’s statistical uncertainty in applying a brightness-distance relation derived from 10,000 red luminous galaxies to all 600,000 without measuring them individually. The game we play is, we have so many that the averages still give us very useful information about their distribution. And without having to measure their spectra, we can look much deeper into space.”

Schlegel agrees that the researchers are far from achieving the precision they want. “But we have shown that such measurements are possible, and we have established the starting point for a standard ruler of the evolving universe.”

He says “the next step is to design a precision experiment, perhaps based on modifications to the SDSS telescope. We are working with engineers here at Berkeley Lab to redesign the telescope to do what we want to do.”

“The Clustering of Luminous Red Galaxies in the Sloan Digital Sky Survey Imaging Data,” by Nikhil Padmanabhan, David J. Schlegel, Uros Seljak, Alexey Makarov, Neta A. Bahcall, Michael R. Blanton, Jonathan Brinkmann, Daniel J. Eisenstein, Douglas P. Finkbeiner, James E. Gunn, David W. Hogg, ??bf?eljko Ivezić, Gillian R. Knapp, Jon Loveday, Robert H. Lupton, Robert C. Nichol, Donald P. Schneider, Michael A. Strauss, Max Tegmark, and Donald G. York, will appear in the Monthly Notices of the Royal Astronomical Society and is now available online at http://arxiv.org/archive/astro-ph.

SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions, which are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, Cambridge University, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington.

SDSS funding is provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. Visit the SDSS web site at http://www.sdss.org/.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California. Visit our website at http://www.lbl.gov.

Original Source: Berkeley Lab

Posted on by Fraser Cain

What’s Up This Week – May 15 – May 21, 2006

M63: “The Sunflower Galaxy”. Image credit: N.A. Sharp/NOAO/AURA/NSF. Click to enlarge
Greetings, fellow SkyWatchers! It may be raining all over the world, but when the skies do clear there will be plenty to explore as we take a look at bright star systems, distant galaxies, globular clusters and astronomy history. So turn your eyes to the skies, because….

Here’s what’s up!

Monday, May 15, 2006 – While we have a short time before the Moon rises, let’s head towards the stars and revisit the fourth brightest in the sky – Arcturus.

Located some 37 light-years away, the “Watcher of the Bear” was one of the very first stars to be seen during daylight in 1635. It achieved public fame when light from Arcturus activated a photoelectric cell which actuated a relay to turn on floodlights to open Chicago’s “Century of Progress” Exposition in 1933. This nearby star was chosen for the honor because the light reaching Earth that night was thought to have left Arcturus during Chicago’s 1893 Exposition. Here’s to guessing you couldn’t see Arcturus once the lights were on….

But keep your lights off and your eyes on the skies as we explore four celestial “neighbors” of Arcturus. About a fist width east, you’ll see four stars arranged roughly north/south. The northernmost is 4.6 magnitude Xi – a very pretty double with yellow primary and disparate orange secondary. The next star south is 4.7 magnitude Omicron, followed by 4.9 magnitude Pi to the southwest. Pi is a double with a closely matched magnitude companion trailing it to the east. Keep heading south for Zeta – also close to being a matched set. But, beware… It takes at least a larger scope and high magnification to split this pair!

Tuesday, May 16 – With plenty of time before the Moon rises, let’s revisit a galaxy very similar to our own Milky Way – NGC 2903. Located less than two degrees south of Lambda Leonis, this magnificent 9.0 magnitude barred spiral can be spotted with binoculars from a dark location, and is easily seen in a small scope.

While NGC 2903’s size and central bar closely resemble our own galaxy’s structure, the Hubble Space Telescope crossed the 25 million light-year gap and found evidence of young globular clusters in its galactic halo – unlike our own old structures. This widespread star forming region is believed to be attributed to the gravity of the central bar. Small telescopes will show the bar as a lateral concentration across the central structure, while larger apertures will reveal spiral arms and condensed regions of innumerable stars.

Want to try something new? How about the exquisite 9.6 magnitude globular cluster – NGC 5634. Found about halfway between Iota and Mu Virginis and almost due south of Phi, what makes it special is its environs. The little globular shows half its size in smaller scopes, but shares the field but that half with an 8th and a 12th magnitude star. This gives it the appearance of a trinary star system!

Wednesday, May 17 – Today in 1835, J. Norman Lockyer was born. While the name might not be widely recognized, Lockyer was the first to note previously unknown absorption lines in the Sun’s spectrum while making visual studies in 1868. Little he knew that he had correctly identified the electromagnetic signature of the second most abundant element in the universe – helium – an element not discovered on Earth until 1891! Also known as the “Father of Archeoastronomy,” Sir Lockyer was one of the first to note the astronomical nature of ancient structures such as Stonehenge and the Egyptian pyramids.

If you would like to see a helium rich star, look no further tonight than Alpha Virginis – Spica.

Also on this day in 1882, a sun-grazing comet was discovered on photographs of the solar corona taken during a total solar eclipse – but the mysterious comet has not been seen since.

Thursday, May 18 – Before the Moon rises tonight, let’s locate Iota Centauri – another “bright star and galaxy” view. NGC 5102 is a 9.7 magnitude lenticular galaxy which displays a brilliant core. The core region is about all you will see with a 2.9 magnitude star so nearby! A challenge? You bet…

On this day in 1910, Comet Halley transited the Sun, but could not be detected visually. Since the beginning of astronomical observation, transits, eclipses and occultations have provided some very accurate determinations of size. Since Comet Halley could not be spotted against the solar surface, we learned almost a century ago that a cometary nucleus had to be smaller than 100 kilometers in diameter.

Would you like to get a grasp on that concept? Wait until the Moon rises tonight and revisit the most prominent crater of all – Copernicus. In a study done by Shoemaker, this ancient crater was proven to be formed by a gigantic impact. Feature after feature so closely resembles geological impact craters on Earth, that we can say with complete certainty this crater was formed by a large meteoritic body. And just how large is crater Copernicus? Oh, about the size of a certain famous comet’s nucleus – 100 kilometers…

Now let’s head for Omega Centauri. At magnitude 3.7, NGC 5139 is one of the few studies in the night sky receiving a Greek letter despite being decidedly “unstarlike!”

Recorded by Ptolemy as a star, given the designation “Omega” by Bayer, and first noted as non-stellar by Edmond Halley in 1677, J.L.E. Dreyer went on to add three exclamation marks (!!!) to his abbreviated description after including it as entry 5139 in the 1888 New General Catalogue. As the largest globular cluster in our own galaxy, this 5 million solar mass “star of stars” contains more matter than Sagittarius A – the supermassive black hole on which the Milky Way pivots. Omega’s mass is greater than some dwarf galaxies. Of the more than thirty galaxies associated with our Local Group, only the Great Andromeda possesses a globular (G1) brighter than Omega!

Friday, May 19 – Tonight let’s begin by locating the constellation Canes Venatici as we pick out the “Sunflower Galaxy” – M63. Located about a fist width southwest of M51, you can sometimes spot it by scanning the area midway between Alkaid and Cor Caroli.

Originally discovered in 1779 by M?chain, bright M63 is located about 37 million light-years away and believed to be part of a group of galaxies including M51. To binoculars, M63 appears as a faint misty oval, but larger scopes will reveal the galaxy’s spiral arms as a grainy background – brightening considerably towards the center. The most interesting feature of M63 is its arm structure. Most typical spiral galaxies contain two or three distinct arms, yet this structure is multiple – showing short spiral arcs reminding many observers of a “celestial flower.” Studies of M63 reveal that the galactic material at the edges of these arms is moving much faster than normal. Given the amount of visible matter, this additional rotational velocity indicates the presence of significant amounts of dark matter in its overall structure.

If you’re in the mood for a challenge, why not try faint globular cluster – NGC 5466. Located in Bootes, NGC 5466 gives a splendid view in larger scopes. – showing a “pin-cushiony” distribution of its fainter stars. Small instruments might be able to pick this one up on a dark night. The cluster is 52 million light-years away – a value very similar to that of M53 and neighboring globular cluster NGC 5053. To locate NGC 5466, start at M3, about halfway between Arcturus and Cor Caroli. Head due east about five degrees past a lone 6th magnitude star.

Saturday, May 20 – Early evening dark means a good time to look for “the Owl and the Edge-On.”

Start with Beta Ursae Majoris – southwestern star of the Big Dipper. About a finger-width between it and Phecda to the southeast, you’ll catch the 10.1 magnitude Edge-On galaxy first seen by Pierre M?chain on February 19, 1781. Although it was later verified by Charles Messier, it didn’t formally enter the Messier catalog until 1953 when Owen Gingerich entered it. Despite being faint, M108 contrasts well on a good dark night sky and larger scopes will make out irregular patches of detail.

Less than a finger-width further southeast, you’ll spot M97 – the Owl Nebula. But let’s ask a tough question: Which came first, the Owl or the Edge-On? According to Owen Gingerich’s research, the Owl (M97) was discovered by Pierre M?chain three days earlier than the Edge-On – and what an accomplishment that was! Many observers cite M97 as one of the most difficult of the Messier studies to detect – especially through the kind of contrast-robbing skies found near larger cities. Pollution!

The “Owl” gets its name for the vague gray-greenness of its light, and the two curious voids visible through larger scopes. These voids are thought to be the result of looking at a globe of nebulosity whose lowest-density poles lie at an oblique angle to our line of sight. The material making up M97 and the light causing it to glow are associated with a high surface temperature central star in the last stages of life. At the center of M97 is a faint 16th magnitude dying star.

Sunday, May 21 – Are you ready for something new? Then let’s start by locating the two northernmost stars of the Big Dipper – Dubhe and Megrez. Now imagine that these two bright stars are the base of a pyramid. Use lowest power and center at the apex of this pyramid to the north. There you will see a fine, mid-sized spiral galaxy – NGC 4125. Average scopes will see a stellar nucleus in the 9.8 magnitude structure, along with an expansive core region and faint spiral extensions. A “Missed-Messier” perhaps? You bet!

Something old? Return to Omega Centauri and the 7.0 magnitude, almost incomprehensibly structured galaxy NGC 5128. It’s otherwise known as radio-source Centaurus A! NGC 5128 is easily found halfway between Omega and Iota Centauri.

And now for Moon rise…

In 1961, United States President John F. Kennedy launched the country on a journey to the Moon as he made one of his most famous speeches to Congress: “I believe this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to Earth. No single space project in this period will be more impressive to mankind or more important for the long-range exploration of space…”

While the Apollo 11 landing site is hidden behind the terminator tonight, it is still possible to see another: that of Apollo 15. Locate previous northern study crater Plato and look due south past the isolated Spitzbergen Mountains to comparably-sized Archimedes. Spend a few moments enjoying Archimedes’ well-etched terraced walls and textured bright floor. Then look east look for the twin punctuations of Aristillus and the more northern Autolycus. South of Aristillus note the heart-shape of Paulus Putredinus. There you will see Mons Hadley very well highlighted and alone on its northeastern bank. Power up to see that the Mons Hadley area includes a cove known as the Hadley Delta, and there on that plain just north of the brilliant mountain peak is where Apollo 15 touched down.

Be aware that Uranus is also very nearby and will be occulted by the Moon! Check IOTA for specifics in your area.

May all your journeys be at light speed… ~Tammy Plotner with Jeff Barbour.

Posted on by Fraser Cain

Astrophoto: The Large Magellanic Cloud by John Gleason

The Large Magellanic Cloud by John Gleason
In August 1519, a Portuguese admiral with five tall ships and a crew of 270 men departed from Spain on the first attempt to circle the earth by taking a route predominantly through the southern hemisphere. The admiral, named Ferdinand Magellan, didn’t return to Spain having died on the voyage during a battle in the Philippines and only one ship returned with eighteen tattered men three years later. The voyage was a milestone in human history by discovering the full scope of the Earth’s size, the need for an international date line and the two Clouds of Magellan, the largest one pictured here.

The Magellanic Clouds were actually known previously by the indigenous people living in the southern hemisphere. A Persian astronomer made the first written reference almost 600 years prior to Magellan?s discovery, but it was Magellan who made their existence part of western knowledge and thus they were named after him. The clouds are actually two out of thirteen dwarf satellite galaxies that orbit the Milky Way. The total number circling our island universe will probably grow since two new ones have recently been reported and additional ones are already suspected.

The Large Magellanic Cloud is the more massive and closer of the two named after the explorer and the second closest galaxy to our own. Located about 180,000 light years distant in southern constellation of Dorado, the Large Magellanic Cloud is estimated to span over 15,000 light years and contains about 60 globular clusters, 400 planetary nebulae, 700 open clusters, and several hundred thousand giant and supergiant stars. It is speculated that this satellite galaxy may have formerly been a larger spiral that ventured too close and was partially devoured by the Milky Way.

This spectacular portrait of the Large Magellanic Cloud is a mosaic of six separate images taken through a hydrogen-alpha narrow band filter. The filter rejects white light that is visible to the naked eye and only allows the very dark red radiation emitted by hydrogen gas, a primary component of nebulae, to pass onto the CCD.detector. The area of this image covers is several times the diameter of the full moon. The Large Magellanic Cloud is the glowing elongated object extending from the eleven o’clock position towards the center. Around it are dozens of nebulae, the most prominent of which is called the Tarantula, located to the upper right of the galaxy in this picture. This is also the vicinity where the closest supernova in 300 years was discovered in 1987- SN1987A.

Veteran astrophotographer John Gleason produced this picture earlier this year from the Sky Shed Observatory in Coonabarabran, New South Wales, Australia. John used a four-inch Takahashi FSQ astrograph and an 11 mega-pixel astronomical camera to record the twenty cumulative hours of exposures required to produce this striking deep space image.

Do you have photos you’d like to share? Post them to the Universe Today astrophotography forum or email them, and we might feature one in Universe Today.

Written by R. Jay GaBany