How Galaxies Came to Be: Astronomers Explain Hubble Sequence

For the first time, two astronomers have explained the diversity of galaxy shapes seen in the universe. The scientists, Dr Andrew Benson of the California Institute of Technology (Caltech) and Dr Nick Devereux of Embry-Riddle University in Arizona, tracked the evolution of galaxies over thirteen billion years from the early Universe to the present day.

Their results appear in the journal Monthly Notices of the Royal Astronomical Society.

Galaxies are the collections of stars, planets, gas and dust that make up most of the visible component of the cosmos. The smallest have a few million and the largest as many as a million million (a trillion) stars.

American astronomer Edwin Hubble first developed a taxonomy for galaxies in the 1930s that has since become known as the 'Hubble Sequence'. There are three basic shapes: spiral, where arms of material wind out in a disk from a small central bulge, barred spirals, where the arms wind out in a disk from a larger bar of material and elliptical, where the galaxy's stars are distributed more evenly in a bulge without arms or disk. For comparison, the galaxy we live in, the Milky Way, has between two and four hundred thousand million stars and is classified as a barred spiral.

Explaining the Hubble Sequence is complex. The different types clearly result from different evolutionary paths but until now a detailed explanation has eluded scientists.

Benson and Devereux combined data from the infrared Two Micron All Sky Survey (2MASS) with their sophisticated GALFORM computer model to reproduce the evolutionary history of the Universe over thirteen billion years. To their surprise, their computations reproduced not only the different galaxy shapes but also their relative numbers.

"We were completely astonished that our model predicted both the abundance and diversity of galaxy types so precisely," said Devereux. "It really boosts my confidence in the model," added Benson.

The astronomers' model is underpinned by and endorses the 'Lambda Cold Dark Matter' model of the Universe. Here 'Lambda' is the mysterious 'dark energy' component believed to make up about 72% of the cosmos, with cold dark matter making up another 23%. Just 4% of the Universe consists of the familiar visible or 'baryonic' matter that makes up the stars and planets of which galaxies are comprised.

Galaxies are thought to be embedded in very large haloes of dark matter and Benson and Devereux believe these to be crucial to their evolution. Their model suggests that the number of mergers between these haloes and their galaxies drives the final outcome -- elliptical galaxies result from multiple mergers whereas disk galaxies have seen none at all. Our Milky Way galaxy's barred spiral shape suggests it has seen a complex evolutionary history, with only a few minor collisions and at least one episode where the inner disk collapsed to form the large central bar.

Source: www.sciencedaily.com

Mirror Testing at NASA Breaks Superstitious Myths

In ancient mythological times reflective surfaces like shiny metals and mirrors were thought to be magical and credited with the ability to look into the future. NASA is using mirrors to do just the opposite -- look into the past.

Fast forward a couple of centuries from ancient time and myths to find NASA is developing a primary mirror, 21.3 feet in diameter, for use on the James Webb Space Telescope in a very different way -- to tell us about our beginning in the universe and how the first galaxies formed. The primary mirror will serve as the telescope's eye and peer through dusty clouds to see stars forming planetary systems, connecting the Milky Way to our own Solar System.

Handling delicate space hardware holds no superstitious myths for NASA, but it's still a delicate task that requires careful preparation. Six of the 18 Webb telescope mirror segments are being moved into the X-ray and Cryogenic Facility, or XRCF, at NASA's Marshall Space Flight Center in Huntsville, Ala., to eventually experience temperatures dipping to a chilling -414 degrees Fahrenheit to ensure they can withstand the extreme space environments.

When the primary mirror is assembled in space, it will include three different shapes of mirror segments: 6 are "A" segments, 6 are "B" segments and 6 are "C" segments. This upcoming test in the XRCF will collect data from all three sizes -- "A, B and C"-- a first for these in the cryogenic facility. This test will also include the engineering development unit, the first primary mirror segment of the Webb telescope that has met flight specifications at ambient temperatures.

"By the time testing in the XRCF concludes in 2011, all 18 flight segments will have been through multiple measurements while experiencing the extreme temperatures of space," said Helen J. Cole, James Webb Space Telescope Activities Project Manager at NASA Marshall. "This process has been six years in the making and we're excited that we can support the Webb telescope development with our world class cryogenic test facility."

Marshall's X-ray & Cryogenic Facility is the world's largest X-ray telescope test facility and a unique, cryogenic, clean room optical test location. The test chamber takes approximately five days to cool a mirror segment to cryogenic temperatures. As this cooling takes place, engineers will measure in extreme detail how the shapes of the mirrors change, simulating how they'll react to space temperatures.

"This is a tremendously important milestone to the Webb Telescope project that bodes well for both our future mirror manufacturing schedule and for the potential performance capabilities of the telescope," said Lee Feinberg, James Webb Space Telescope Optical Telescope Element Manager at NASA Goddard.

Northrop Grumman Corporation is leading the design and development effort for the space agency's Goddard Space Flight Center, Greenbelt, Md. Mirror manufacturing began six years ago, led by Northrop Grumman's principal optical contractor Ball Aerospace. Brush Wellman in Elmore, Ohio made twenty-one 500-lb. hexagonal mirror blanks from beryllium, an extremely strong, lightweight metal. Axsys Technologies in Cullman, Ala. machined the backside of the beryllium blanks and chemically etched them into an isogrid pattern that reduced mirror mass by 92 percent, from 250 kg to 21 kg (equivalent to 553 pounds and 46 pounds). The front side of the mirror blank was machined to prep the optical surface for high precision grinding, polishing and testing, which is being done by Tinsley. The mirror segments have undergone a series of polishing and cryogenic testing cycles. Ball incorporates the mirrors into optical assemblies, which are mounted on the telescope structure.

Source: www.sciencedaily.com

How Earth Survived Its Birth

WASHINGTON — Just how Earth survived the process of its birth without suffering an early demise by falling into the sun has been something of a mystery to astronomers, but a new model has figured out what protected our planet when it was still a vulnerable, baby world.

In short, temperature differences in the space around the sun, 4.6 billion years ago, caused Earth to migrate outward as much as gravity was trying to pull it inward, and so the fledgling world found equilibrium in what we now know to be a very habitable orbit.

Planets like the Earth are thought to form from condensing clouds of gas and dust surrounding stars. The material in these disks gradually clumps together, eventually forming planetesimals – the asteroid-sized building blocks that eventually collide to form full-fledged planets.

As the planets are forming, they are also thought to migrate within the surrounding dust disk. The classic picture of this planet migration suggests that planets like (and including) the Earth should have plummeted into the sun while they were still planetesimals.

"Well, this contradicts basic observational evidence, like We. Are. Here," said astronomer Moredecai-Mark Mac Low of the American Museum of Natural History in New York.

Mac Low and his colleagues investigated this apparent paradox and came up with a new model that explains how planets can migrate as they're forming and still avoid a fiery premature death. He presented these findings here today at the 215th meeting of the American Astronomical Society.

One problem with the classic view of planet formation and migration is that it assumed that the temperature of the protoplanetary disk around a star is constant in temperature across its whole span, Mac Low explained.

It turns out that portions of the disk are actually opaque and so cannot cool quickly by radiating heat out to space. This creates temperature differences across the disk, and these differences have not been accounted for before in models. So Mac Low and his colleagues created new model simulations of planet migration that include a disk with variations in temperature.

What happens when you change the temperatures in the disk is this: The temperature changes can completely alter the nature of the planet migrations, causing planets to migrate outward instead of inward.

"Well, that is a major development," Mac Low said, because you can put it in the model and see if outward migration cancels inward migration "and allows us to survive, or at least our progenitors."

Sure enough, that seems to be the case. Within the disk, zones of inward and outward migration develop that meet at equilibrium zones; once planets reach these, "they more or less sit there," Mac Low said.

And eventually the disk dissipates to a point where its gravity can no longer influence the planets to pull or push them into new orbits.

So the model suggests that outward migration "allows planetoids to survive," which explain how planets in our solar system and others that we see in galaxy survive, Mac Low said.

Source: www.space.com

NASA Scientists Classify the Time Before Earth Existed: the Chaotian Era

The geological time scale, with its familiar Cretaceous, Cambrian, and Eocene periods, works great as a calendar for the history of the Earth. Indeed, the different periods only cover the 3.8 billion years of life on Earth, with everything before that time lumped into one nondescript eon called the Hadean. But for some geologists, that lack of specificity simply won't work any more.

Frustrated by referring to Hadean-era events with vague phrases like "around the time of Moon formation" or "shortly after Earth cooled", four scientists, including two from NASA, have chopped up the Hadean into distinct geologic periods, and even extended the time scale back to the formation of the solar system, with a new eon called the "Chaotian."

Under the new scheme, the Hadean Eon begins when Tellus, the proto-Earth, gets smacked into by Theia, a proto-planet absorbed into the Earth. This impact caused the formation of the Moon, and marks the beginning of Earth at its current size. Everything coming before that event takes place in the Chaotian.

During the Chaotian, the planets coalesce out of a giant disk of hot dust, cool, and form the solar system we know today. The Chaotian is also broken down into bombastic-sounding periods like the Hyperitian and the Titanomachean.

If the names seem a little out there, it's because they're drawn from classic Greek and Latin literature. Since no scientist can avoid naming something after Greek myths, the geologists drew the names from Hesiod's Theogony, Aeschylus's Prometheus Bound, and Thamyris's Titanomachia. Which is to say, NERDS!

The scientists hope that the new time scale will enable geologists studying the early history of the planet to write more accurate papers. For the rest of us, just be happy that there's a period of our history literally named "Clash Of The Titans."

Source: www.popsci.com

Kepler Telescope Spots Hotter, Weirder Bodies Than Ever Before Seen (In The Sky, That Is)

It's been less than a year since NASA launched the Kepler Space Telescope, and the device is already paying off with new discoveries. In particular, NASA scientists have identified a planet with the consistency of styrofoam, a gaggle of exoplanets, and two never-before-observed objects too small to be stars, but too hot to be planets.

NASA researchers revealed these discoveries yesterday, during a meeting of the American Astronomical Society. These revelations cover the first data sets produced by the Kepler Telescope, which launched in March 2009.

The styrofoam planet, called Kepler 7b, is 1.6 times the size of Jupiter, and less dense than water. If that wasn't weird enough, Kepler 7b also maintains a toasty 2300-degree Fahrenheit surface temperature, roughly hot enough to melt gold. But those planets weren't even the hottest objects Kepler found. Two of the objects Kepler detected were hotter than the stars they orbited, thus failing to resemble any previously observed astronomical bodies.

The objects are far smaller than stars, but much too hot to be planets. Some astronomers think that they might be newly formed planets, still hot from their chaotic birth. However, others think they might be white dwarf stars, slowly shrinking and dying as they orbit a more stable twin star at the center of their solar system.

And while these exotic bodies are certainly interesting, the most exciting discoveries announced yesterday were of something incredibly common to us Earthlings: sun-like stars. Based on measurements taken through Kepler, the NASA astronomers determined that only one third of 43,000 observed sun-like stars emit periodic life-killing bursts of radiation. This number is far lower than the previous estimate, and greatly expands the number of known solar systems potentially capable of harboring alien life.

Despite all the fascinating discoveries, the rate of discoveries coming out of Kepler may have been the most impressive revelation of the talk. Within the first six weeks of operation, scientists had already used Kepler to confirm five new exoplanets, a rate of discovery that makes Kepler a worthy successor to the Hubble.

Source: www.popsci.com

Is There Life on Other Planets?

Most scientists believe that, yes, there may be life on other planets.

What scientists look for when searching for alien life are stars that are similar to our sun, and planets that show evidence of water, an atmosphere that contains oxygen or methane, and a planet that is neither too far nor too close to its sun. Scientists believe that water is a necessary component of life, so a planet with none cannot support life (at least not life as we know it). In our solar system, the planet most similar to ours is Mars, however, scientists have not found evidence that life exists there, or that it ever did. There is evidence that there was once water on Mars, however, there doesn't seem to be any water on Mars now. Mars does have a lot of water ice at the polar caps, but the temperature on Mars at the poles is too cold for this ice to melt.

At Mars equator it does get to a comfortable daytime temperature that is slightly above 60 °F (16°C) but there isn't ice or water at the equator and Mars equator gets very cold during the nighttime, below -200 °F (-129 °C). This means that any life that might be inclined to form during the daytime would probably not survive the night. Scientists are still investigating whether or not life ever existed on Mars.

Scientists are also investigating whether or not some of the moons of Jupiter and Saturn are capable of supporting life, such as Jupiter's moon Europa, for example. The planets Jupiter and Saturn themselves certainly don't seem capable of supporting life.

Source: www.outerspacesite.com

NASA's Mars Rover Spirit Has Uncertain Future as Sixth Anniversary Nears

NASA's Mars rover Spirit will mark six years of unprecedented science exploration and inspiration for the American public on Sunday. However, the upcoming Martian winter could end the roving career of the beloved, scrappy robot.

Spirit successfully landed on the Red Planet at 8:35 p.m. PST on Jan. 3, 2004, and its twin Opportunity arrived at 9:05 p.m. Jan. 24, 2004. The rovers began missions intended to last for three months but which have lasted six Earth years, or 3.2 Mars years. During this time, Spirit has found evidence of a steamy and violent environment on ancient Mars that was quite different from the wet and acidic past documented by Opportunity, which has been operating successfully as it explores halfway around the planet.

A sand trap and balky wheels are challenges to Spirit's mobility that could prevent NASA's rover team from using a key survival strategy for the rover. The team may not be able to position the robot's solar panels to tilt toward the sun to collect power for heat to survive the severe Martian winter.

Nine months ago, Spirit's wheels broke through a crusty surface layer into loose sand hidden underneath. Efforts to escape this sand trap barely have budged the rover. The rover's inability to use all six wheels for driving has worsened the predicament. Spirit's right-front wheel quit working in 2006, and its right-rear wheel stalled a month ago. Surprisingly, the right-front wheel resumed working, though intermittently. Drives with four or five operating wheels have produced little progress toward escaping the sand trap. The latest attempts resulted in the rover sinking deeper in the soil.

"The highest priority for this mission right now is to stay mobile, if that's possible," said Steve Squyres of Cornell University in Ithaca, N.Y. He is principal investigator for the rovers.

If mobility is not possible, the next priority is to improve the rover's tilt, while Spirit is able to generate enough electricity to turn its wheels. Spirit is in the southern hemisphere of Mars, where it is autumn, and the amount of daily sunshine available for the solar-powered rover is declining. This could result in ceasing extraction activities as early as January, depending on the amount of remaining power. Spirit's tilt, nearly five degrees toward the south, is unfavorable because the winter sun crosses low in the northern sky.

Unless the tilt can be improved or luck with winds affects the gradual buildup of dust on the solar panels, the amount of sunshine available will continue to decline until May 2010. During May, or perhaps earlier, Spirit may not have enough power to remain in operation.

"At the current rate of dust accumulation, solar arrays at zero tilt would provide barely enough energy to run the survival heaters through the Mars winter solstice," said Jennifer Herman, a rover power engineer at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The team is evaluating strategies for improving the tilt even if Spirit cannot escape the sand trap, such as trying to dig in deeper with the wheels on the north side. In February, NASA will assess Mars missions, including Spirit, for their potential science versus costs to determine how to distribute limited resources. Meanwhile, the team is planning additional research about what a stationary Spirit could accomplish as power wanes.

"Spirit could continue significant research right where it is," said Ray Arvidson of Washington University in St. Louis, deputy principal investigator for the rovers. "We can study the interior of Mars, monitor the weather and continue examining the interesting deposits uncovered by Spirit's wheels."

A study of the planet's interior would use radio transmissions to measure wobble of the planet's axis of rotation, which is not feasible with a mobile rover. That experiment and others might provide more and different findings from a mission that has already far exceeded expectations.

"Long-term change in the spin direction could tell us about the diameter and density of the planet's core," said William Folkner of JPL. He has been developing plans for conducting this experiment with a future, stationary Mars lander. "Short-period changes could tell us whether the core is liquid or solid," he said.

In 2004, Opportunity discovered the first mineralogical evidence that Mars had liquid water. The rover recently finished a two-year investigation of a half-mile wide crater called Victoria and now is headed toward Endeavor crater, which is approximately seven miles from Victoria and nearly 14 miles across. Since landing, Opportunity has driven more than 11 miles and returned more than 132,000 images.

Source: www.sciencedaily.com