Posted on by Fraser Cain

Tiny Satellite Could Make a Big Difference

Prof. Robert Zee and Eric Caillibot put final touches on CanX-2. Image credit: U of T Click to enlarge
A 3.5- kilogram satellite that could revolutionize the space industry was unveiled Aug. 31 at U of T?s Institute for Aerospace Studies (UTIAS).

The Canadian Advanced Nanospace eXperiment 2 (CanX-2) satellite, which appears as unassuming as a shoebox, will pave the way for a wave of mini-satellites that are more effective and less expensive.

CanX-2 is the brainchild of graduate students and staff. Professor Robert Zee, manager of the institute?s space flight laboratory (SFL) and the CanX-2 team leader, said the point of the satellite mission is two-fold.

?The first is to provide complete development cycle training for students through a mission that has to be complete in two years,? Zee said. ?The second is to launch a tiny research platform into space to test innovative, revolutionary technologies in a rapid, risk-taking manner and also to perform important science missions that are now benefiting from the availability of smaller and smaller instrumentation.?

Set to launch next year, CanX-2 will test small, low-power devices such as a mini-spectrometer designed to measure greenhouse gases. Its primary goal is to lay the groundwork for flying formations of two similar but more advanced satellites.

These satellites, CanX-4 and CanX-5, will demonstrate technology that could eventually find large, expensive satellites replaced by groups of smaller, cheaper collaborating satellites. CanX-4 and CanX-5 are scheduled for launch in 2008.

?What we?re trying to prove here is that spacecraft don?t have to be huge and clunky to achieve the best results,? said Zee, who added that the price tag for the CanX-2 and two following missions is only $1 million, compared with hundreds of millions of dollars for a traditional satellite mission.

?These nanosatellites and the tiny technologies that we?re launching into space represent a paradigm shift in the way we think about and execute space missions.?

For students such as Daniel Kekez the chance to work on a real space mission is priceless. ?I?ve spent the past two years going from designs and calculations to building and testing hardware and software that will fly and operate in space,? Kekez said. ?This kind of experience would take years to obtain for an engineer starting out in industry. It?s simply fantastic!?

CanX-2 is the second nanosatellite mission at UTIAS/SFL. CanX-1, Canada?s first nanosatellite and one of the smallest satellites ever built, was launched with the MOST microsatellite in 2003 by Eurockot Launch Services from Plesetsk, Russia

Original Sourse: U of T News Release

Posted on by Fraser Cain

Rogue Supermassive Black Hole Has No Galaxy

Hubble image from a sample of 20 nearby quasars. Image credit: NASA/ESA/ESO Click to enlarge
The detection of a super-massive black hole without a massive ‘host’ galaxy is the surprising result from a large Hubble and VLT study of quasars.

This is the first convincing discovery of such an object. One intriguing explanation is that the host galaxy may be made almost exclusively of ‘dark matter’.
A team of European astronomers has used two of the most powerful astronomical facilities available, the NASA/ESA Hubble Space Telescope and the ESO Very Large Telescope (VLT) at Cerro Paranal, to discover a bright quasar without a massive host galaxy.

Quasars are powerful and typically very distant source of huge amounts of radiation. They are commonly associated with galaxies containing an active central black hole.

The team conducted a detailed study of 20 relatively nearby quasars. For 19 of them, they found, as expected, that these super-massive black holes are surrounded by a host galaxy. But when they studied the bright quasar HE0450-2958, located some 5000 million light-years away, they could not find evidence for a host galaxy.

The astronomers suggest that this may indicate a rare case of a collision between a seemingly normal spiral galaxy and an ‘exotic’ object harbouring a very massive black hole.

With masses that are hundreds of millions times bigger than the Sun, super-massive black holes are commonly found in the centres of the most massive galaxies, including our own Milky Way. These black holes sometimes dramatically manifest themselves by devouring matter that they gravitationally swallow from their surroundings.

The best fed of these objects shine as ‘quasars’ (standing for ‘quasi-stellar object’ because they had initially been thought of as stars).

The past decade of observations, largely with the Hubble telescope, has shown that quasars are normally associated with massive host galaxies. However, observing the host galaxy of a quasar is challenging work because the quasar completely outshines the host and masks the galaxy?s underlying structure.

To overcome this problem, the astronomers devised a new and highly efficient strategy. Combining Hubble?s ultra-sharp images and spectroscopy from ESO?s VLT, they observed their sample of 20 quasars at the same time as a reference star. The star served as a reference pinpoint light source that was used to disentangle the quasar light from any possible light from an underlying galaxy.

Despite the innovative techniques used, no host galaxy was seen around HE0450-2958. This means that if any host galaxy exists, it must either be at least six times fainter than typical host galaxies, or have a radius smaller than about 300 light-years, i.e. 20 to 170 times smaller than typical host galaxies (which normally have radii ranging from about 6000 to 50 000 light-years).

“With the powerful combination of Hubble and the VLT we are confident that we would have been able to detect a normal host galaxy,” said Pierre Magain of the Universit? de Li?ge, Belgium.

The astronomers did however detect an interesting smaller cloud of gas about 2500 light-years wide near the quasar, which they call ‘the blob’. VLT observations show this cloud to be glowing because it is bathed in the intense radiation coming from the quasar, and not from stars inside the cloud. Most likely, it is the gas from this cloud that feeds the super-massive black hole, thereby allowing it to become a quasar.

“The absence of a massive host galaxy, combined with the existence of the blob and the star-forming galaxy, lead us to believe that we have uncovered a really exotic quasar,” said Fr?d?ric Courbin of the Ecole Polytechnique Federale de Lausanne, Switzerland.

“There is little doubt that an increase in the formation of stars in the companion galaxy and the quasar itself have been ignited by a collision that must have taken place about 100 million years ago. What happened to the putative quasar host remains unknown.”

HE0450-2958 is a challenging case. The astronomers propose several possible explanations. Has the host galaxy been completely disrupted as a result of the collision? Has an isolated black hole captured gas while crossing the disk of a spiral galaxy? This would require very special conditions and would probably not have caused such a tremendous disturbance of the neighbouring galaxy as is observed. Further studies will hopefully clarify the situation.

Another intriguing hypothesis is that the galaxy harbouring the black hole was almost exclusively made of ‘dark matter’. It may be that what is observed is a normal phase in the formation of a massive galaxy, which in this case has taken place several 1000 million years later than in most others.

Original Source: ESA Portal

Posted on by Fraser Cain

Mars Reconnaissance Orbiter is Doing Well

Artist’s concept of Mars Reconnaissance Orbiter. Image credit: NASA/JPL Click to enlarge
Three cameras on NASA’s Mars Reconnaissance Orbiter worked as expected in a test pointing them at the moon and stars on Sept. 8.

“We feel great about how the camera performed and can hardly wait to see what it will show us at Mars,” said Dr. Alfred McEwen of the University of Arizona, Tucson, principal investigator for the High Resolution Imaging Science Experiment aboard Mars Reconnaissance Orbiter.

The test also checked operation of the spacecraft’s Context Camera and Optical Navigation Camera, plus the spacecraft’s high-gain antenna and systems for handling and distributing data from the instruments.

“The instruments and the ground data system passed this test with flying colors,” said Mars Reconnaissance Orbiter Project Manager Jim Graf of NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We received 75 gigabits of data in less than 24 hours, which is a new one-day record for any interplanetary mission.”

The spacecraft was about 10 million kilometers (6 million miles) from the moon when it turned to slew the cameras’ fields of view across that test target. At that distance, the moon would appear as a single star-like dot to the unaided eye. In the test images by the high-resolution camera, it is about 340 pixels in diameter and appears as a crescent about 60 pixels wide. The tests also included imaging of the star cluster Omega Centauri for data to use in calibrating the camera.

During its primary science mission at Mars, the spacecraft will orbit within about 300 kilometers (186 miles) of that planet’s surface. From that distance, the high-resolution camera will discern objects as small as one meter or yard across.

The Mars Reconnaissance Orbiter, launched on Aug. 12, will reach Mars and enter orbit on about March 10, 2006. After gradually adjusting the shape of its orbit for half a year, it will begin its primary science phase in November 2006. The mission will examine Mars in unprecedented detail from low orbit, returning several times more data than all previous Mars missions combined. Scientists will use its instruments to gain a better understanding of the history and current distribution of Mars’ water. By inspecting possible landing sites and by providing a high-data-rate relay, it will also support future missions that land on Mars.

More information about the mission, including new test images of the moon by the high-resolution camera, is available online at http://www.nasa.gov/mro.

The Mars Reconnaissance Orbiter mission is managed by JPL, a division of the California Institute of Technology, Pasadena, for the NASA Science Mission Directorate. Lockheed Martin Space Systems, Denver, prime contractor for the project, built both the spacecraft and the launch vehicle. Ball Aerospace & Technologies Corp., Boulder, Colo., built the High Resolution Imaging Science Experiment instrument for the University of Arizona to provide to the mission. Malin Space Science Systems, San Diego, Calif., provided the Context Camera. JPL provided the Optical Navigation Camera.

Original Source: NASA News Release

Posted on by Fraser Cain

Let’s Find Life

Artist illustration of the Terrestrial Planet Finder. Image credit: NASA/JPL. Click to enlarge.
Find life!

If it were up to me; if I were running NASA, or the ESA, or the plucky Canadian Space Agency, I’d narrow my focus like a laser beam to answer this fundamental question: are we alone in the Universe?

Find life on Mars
At the time that I’m writing this rant, there are two robotic rovers crawling around the surface of Mars searching for evidence that water once existed on Mars. The reasoning is that if Mars was wet for a long period of time, it would have given life an opportunity to get a foothold.

Well, the rovers have done it. Both Spirit and Opportunity have turned up evidence that Mars was warm and wet, probably for millions of years. And although there were supposed last only three months, they’re still going strong after 18 months! Their solar panels are being regularly cleaned by gusts of wind, and it’s not unreasonable to expect many more months of service.

But there’s a problem. The rovers are colour blind. They can analyze rocks, and search for past evidence of water, but they’re unable to see evidence of life. No problem, new equipment is being developed back here on Earth that would give future rovers the ability to analyze soil for the telltale traces of life. Other detectors will be able to sniff the air for a whiff of methane gas; another possible byproduct of life.

Those rovers are so successful, engineers should put future developments on hold and just start mass producing them. Build dozens and equip them with the latest and greatest instruments and turn them loose on the surface of Mars. By mass producing the same rover chassis, engineers should be able to bring the costs down significantly. Keep improving the design, but why reinvent the wheel?

If we could have 20+ rovers on the surface of Mars, sampling soil, sniffing air, and testing ice, from equator to pole, it would substantially improve our chances of finding life. It’s no guarantee, of course, but it would sure give us our best shot to find it. And if you do find life, you could send a second generation of rovers to analyze the life in great detail and learn whether we share a distant ancestor; some adventurous microbe that jumped planets.

The implications of finding life on Mars are staggering; it could mean that life is as pervasive in the Solar System as it is here on Earth. But it might also mean that all life in the Solar System is related, as there’s growing evidence that life can travel back and forth between planets on meteorites.

So, even if we find life on Mars, I think the discovery would be bittersweet. Maybe our Solar System is filled with life, but could the rest of the Universe be lifeless?

Find Life in Other Star Systems
I think it’s fair to say that the Hubble Space Telescope is one of the most productive and important science instruments ever created. It has fundamentally changed our view of the Universe we live in. It helped find extrasolar planets and discovered the mysterious dark energy which is accelerating the Universe.

But to find life on other worlds, we need more specialized tools. One of these is the Terrestrial Planet Finder, which is currently scheduled for launch in 2012-2015. If everything goes as planned, this amazingly sensitive space telescope will be finding Earth-sized planets orbiting other stars within a decade. Furthermore, it’ll be so powerful, it can analyze the atmosphere of these planets and see if any of them have large quantities of oxygen.

That’s critical. We have oxygen in our atmosphere because hardworking microbes and plants have been producing it for millions of years. Oxygen is so reactive, it really can’t exist in the atmosphere unless there’s a constant source refreshing it. So, if you find oxygen, you’ve found life.

So imagine, in just a decade from now, scientists will be able start analyzing nearby stars and turning up planets with biospheres. You could look up in the sky and start pointing out stars to your friends. “Life… life… life.”

Now wouldn’t that be a groundbreaking discovery? Are we alone in the Universe? We might be able to say, “nope, there’s life everywhere.”

I think the Terrestrial Planet Finder is going to be such a fundamental instrument, it’ll become a bottleneck. Scientists will be lined up for 20 years waiting for a shot to use it. We should build more than one. Once again, we should consider “mass producing” them and analyze many planets at once. Bring down the costs, and give scientists a chance to build up a census of the life surrounding us.

But are we talking about intelligent life or slime mold? We won’t really know. (Well, astronomers might figure out how to detect chloroflourocarbons and guess that a planet is in the golden age of air conditioning.)

Until we actually find intelligent life out there, we’re still going to feel a little lonely.

Find Intelligent Life in the Universe
If you’ve seen Contact, you’ll remember Jodie Foster’s character was searching the heavens with a powerful radio telescope, hoping to hear communications from a distant civilization.

This technology exists. For more than 20 years, SETI (Search for Extraterrestrial Intelligence) researchers have been listening to various stars and precise frequencies, hoping to hear a message from afar. The problem is that our Milky Way is an enormous place, with quadrillions of stars. And the number of frequencies are so vast, that it’ll take a long time to search the sky comprehensively.

Technology is improving, and SETI researchers are now able to scan many stars quickly in many frequencies, but it’s still a fraction of the total sky. The computing power to analyze these data is tremendous, but millions of people around the world have installed SETI@home on their personal computers to lend a hand.

Unlike the Mars rovers and various planet finding missions, SETI gets very little public funding. And this is a tragedy. In a single stroke, SETI could discover intelligent life in the Universe, and maybe even help us communicate back. I’d like to watch educational television broadcast by a civilization millions of years more advanced than us.

We need to develop a mega project to scan the entire sky at all the likely frequencies, and even search optical wavelengths too – in case aliens are using lasers to communicate with us.

Find Life: on Mars, on other planets, across the Milky Way.
We live in an amazing time in human history. We’ve wondered about our place in the Universe for thousands of years, and now we’re within arms’ reach of finding the answers. Who knows? Maybe in just a few decades we could have some definitive answers.

And if we don’t find life on Mars, orbiting other stars, or communicating to us across the vast distances of the Milky Way, it’ll tell us something else.

Something just as important.

Maybe life here on Earth is more precious than we thought. We should take better care of the planet we live on, and the creatures we share it with – it might be unique in the Universe.

Let’s start cranking out those rovers, planet finding telescopes and radio dishes and get an answer. (And if I had to choose, I’d probably advocate putting other stuff on hold while we looked).

Written by Fraser Cain

Posted on by Fraser Cain

Early Atmosphere Looked Very Different From Today

Bruce Fegley examines a meteorite. Image credit: WUSTL Click to enlarge
Using primitive meteorites called chondrites as their models, earth and planetary scientists at Washington University in St. Louis have performed outgassing calculations and shown that the early Earth’s atmosphere was a reducing one, chock full of methane, ammonia, hydrogen and water vapor.

In making this discovery Bruce Fegley, Ph.D., Washington University professor of earth and planetary sciences in Arts & Sciences, and Laura Schaefer, laboratory assistant, reinvigorate one of the most famous and controversial theories on the origins of life, the 1953 Miller-Urey experiment, which yielded organic compounds necessary to evolve organisms.

Chondrites are relatively unaltered samples of material from the solar nebula, According to Fegley, who heads the University’s Planetary Chemistry Laboratory, scientists have long believed them to be the building blocks of the planets. However, no one has ever determined what kind of atmosphere a primitive chondritic planet would generate.

“We assume that the planets formed out of chondritic material, and we sectioned up the planet into layers, and we used the composition of the mix of meteorites to calculate the gases that would have evolved from each of those layers,” said Schaefer. “We found a very reducing atmosphere for most meteorite mixes, so there is a lot of methane and ammonia.”

In a reducing atmosphere, hydrogen is present but oxygen is absent. For the Miller-Urey experiment to work, a reducing atmosphere is a must. An oxidizing atmosphere makes producing organic compounds impossible. Yet, a major contingent of geologists believe that a hydrogen-poor, carbon dioxide-rich atmosphere existed because they use modern volcanic gases as models for the early atmosphere. Volcanic gases are rich in water, carbon dioxide, and sulfur dioxide but contain no ammonia or methane.

“Geologists dispute the Miller-Urey scenario, but what they seem to be forgetting is that when you assemble the Earth out of chondrites, you’ve got slightly different gases being evolved from heating up all these materials that have assembled to form the Earth. Our calculations provide a natural explanation for getting this reducing atmosphere,” said Fegley.

Schaefer presented the findings at the annual meeting of the Division of Planetary Sciences of the American Astronomical Society, held Sept. 4-9 in Cambridge, England.

Schaefer and Fegley looked at different types of chondrites that earth and planetary scientists believe were instrumental in making the Earth. They used sophisticated computer codes for chemical equilibrium to figure out what happens when the minerals in the meteorites are heated up and react with each other. For example, when calcium carbonate is heated up and decomposed, it forms carbon dioxide gas.

“Different compounds in the chondritic Earth decompose when they’re heated up, and they release gas that formed the earliest Earth atmosphere,” Fegley said.

The Miller-Urey experiment featured an apparatus into which was placed a reducing gas atmosphere thought to exist on the early Earth. The mix was heated up and given an electrical charge and simple organic molecules were formed. While the experiment has been debated from the start, no one had done calculations to predict the early Earth atmosphere.

“I think these computations hadn’t been done before because they’re very difficult; we use a special code” said Fegley, whose work with Schaefer on the outgassing of Io, Jupiter’s largest moon and the most volcanic body in the solar system, served as inspiration for the present early Earth atmosphere work.

Original Source: WUSTL News Release

Posted on by Fraser Cain

Fensal-Aztlan Region on Titan

Fensal-Aztlan at Titan’s surface. Image credit: NASA/JPL/SSI Click to enlarge
During its Sept. 7, 2005, flyby of Titan, Cassini acquired images of territory on the moon’s Saturn-facing hemisphere that were assembled to create this mosaic.

Once known only as “the H” because the region looks something like the letter on its side, features in this region now possess provisional names. The northern branch of the H is now called “Fensal,” while the southern branch is known as “Aztlan.”

Fensal is littered with small “islands” ranging in size from 5 to 40 kilometers (3 to 25 miles) across. These landforms currently are thought to be water ice upland areas, surrounded by shallower terrain that is filled-in with dark particulate material from the atmosphere. A few larger islands are also seen, like Bazaruto Facula (near right, containing a dark crater), and several islands in western Fensal. When viewed in images of Shangri-La (on the other side of Titan), island-like landforms of this size tend to occur in clusters with apparent preferred orientations. The small islands in Fensal appear much more scattered (and most appear roughly circular), although a few islands do have an east-west orientation to their long axis.

Aztlan, on the other hand, appears comparatively devoid of small islands, with three large islands in its western reaches, plus only a few smaller islands. The largest of these islands is called “Sotra Facula” (just right of center in the bottom left mosaic frame), and measures 240 by 120 kilometers (149 to 75 miles) across.

The territory covered by this mosaic is similar to that seen in Titan Mosaic – East of Xanadu, which is composed of images from Cassini’s March 2005 Titan flyby. However, the gaps between the images in this mosaic are smaller and fewer than in the earlier mosaic.

The mosaic is centered on a region at 7 degrees north latitude, 21 degrees west longitude on Titan.

These Cassini spacecraft narrow-angle camera images were taken using a filter sensitive to wavelengths of infrared light centered at 938 nanometers. They were acquired at distances ranging from approximately 200,600 to 191,800 kilometers (124,600 to 119,200 miles) from Titan. Resolution in the images is about 2 kilometers (1.2 miles) per pixel. Each image has been strongly enhanced to improve the visibility of surface features.

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

Investigation Into One of Mars Express’ Instruments

Artist’s impression of Mars Express. Image credit: ESA Click to enlarge
ESA has started a technical investigation into the Planetary Fourier Spectrometer (PFS) on board Mars Express, after a problem developed in the instrument a few months ago.

Vibration effects (induced by spacecraft activities) have been suggested as a cause for the observed behaviour. However no source has yet been identified and other causes internal to the instrument cannot be fully ruled out.
In order to establish the exact cause of the problem, ESA?s Mars Express team is setting up an investigations board involving experts from the Mission Science Working Team, ESA, industry and the Italian Space Agency (ASI).

This could lead to resuming scientific observations using modified procedures but, until all existing data and a number of additional measurements currently being planned have been examined, it is too early to draw a conclusion on the operational status of the PFS instrument.

The PFS instrument has performed without any such problems for almost two years, following the launch of Mars Express in June 2003. In this period, the instrument has provided much new information on the global composition and movement of the Martian atmosphere.

Even if it is found that PFS is no longer fully functional, it is only one element in the scientific package on board Mars Express. The other six instruments (HRSC, OMEGA, ASPERA, SPICAM, MARSIS, MaRS) are all currently working well and are providing new insights into the Red Planet and its evolution. These remaining instruments will continue the scientific success of the Mars Express mission.

Original Source: ESA Portal

Posted on by Fraser Cain

Giant Jet Streams

Jupiter. Image credit: NASA/JPL Click to enlarge
Turbulence driven by sunlight and thunderstorm activity may explain the multiple east-west jet streams on Jupiter and Saturn and even produce strong winds extending hundreds or thousands of kilometers into the interior, far below the altitudes where the jets are driven.

Scientists have been trying to understand the mechanisms that form the jet streams and control their structure since the first high-resolution images of Jupiter were returned by the Pioneer and Voyager spacecraft in the 1970s.

On Earth, the jet streams — narrow currents of air flowing from west to east in the midlatitudes — form a major component of our planet’s global circulation, and they control much of the large-scale weather experienced by the United States and other countries outside of the tropics. Similar east-west jet streams dominate the circulation of the giant planets Jupiter, Saturn, Uranus, and Neptune, reaching up to 400 miles per hour on Jupiter and nearly 900 miles per hour on Saturn and Neptune. The question of what causes these jet streams and how deep they extend into the interior of the giant planets remain some of the most important unsolved problems in the study of planetary atmospheres.

Adam Showman and Yuan Lian of The University of Arizona in Tucson and Peter Gierasch of Cornell University in Ithaca, New York, explained how cloud-layer turbulence can drive deep jets at the 37th annual meeting of the Division of Planetary Sciences of the American Astronomical Society, held in Cambridge, England.

Lian, Showman, and Gierasch performed computer simulations showing that horizontal temperature contrasts — generated by sunlight or differences in thunderstorm activity — can produce multiple jet streams that penetrate deep into the interior of a giant planet. In the simulations, the temperature contrasts induce deep-penetrating circulation cells that in turn drive the deep jets. The study, which uses an advanced three-dimensional computer model, is among the first that allows an assessment of how jets formed near the top of the atmosphere interact with the interior.

Most planetary scientists have assumed that jets pumped near the top of the atmosphere will remain confined to those shallow layers, and we’ve shown that this is not a valid assumption,” Showman said.

NASA’s Galileo Probe, which parachuted through Jupiter’s atmosphere in 1995, was intended in part to help answer the question of how deep the jet streams extend. The probe found strong winds extending at least 150 kilometers (almost 100 miles) below the clouds. Planetary scientists have widely interpreted this measurement as evidence that the jets are driven from deep inside Jupiter’s interior. The new study challenges this interpretation.

“We still don’t know whether the jets on the giant planets are driven from the top or within the deep interior,” Showman said. “But our study shows that the deep winds measured by the Galileo probe could just as easily result from shallow cloud-layer turbulence as from turbulence deep inside Jupiter’s interior.”

“This result contradicts a long-standing assumption on the part of many planetary scientists.”

The new study also shows that, under realistic conditions, the turbulence can produce not only numerous jet streams but a strong eastward flow at the equator, as observed on Jupiter and Saturn. Such flows are notoriously difficult to produce in atmospheric models, Showman noted.

Original Source: NASA Astrobiology

Posted on by Fraser Cain

The Risk of a Comet Strike is Low

Comet. Image credit: NASA/JPL Click to enlarge
The chances of the Earth being hit by a comet from beyond Pluto ? ? la Deep Impact ? are much lower than previously thought, according to new research by an ANU astronomer.

Using computer simulations and data from an American military telescope, Dr Paul Francis, from the ANU Research School of Astronomy and Astrophysics at Mt Stromlo, has found there are seven times fewer comets in our solar system than previously thought.

?I calculate that small comets, capable of destroying a city, only hit the Earth once every 40 million years or so,? Dr Francis said. ?Big continent-busting comets, as shown in the movie Deep Impact, are rarer still, only hitting once every 150 million years or so. So I don?t lose sleep over it, but you?re still more likely to be killed by a comet than to win the Lotto jackpot.?

Previous estimates of the number of comets were based on the work of amateur astronomers, who for hundreds of years have been scanning the skies, looking for new comets.

Previously, it was believed that these amateur astronomers were only spotting three per cent of the comets passing close to the Earth: the rest were thought to be missed because they were in the wrong part of the sky or were too faint.

But Dr Francis found that the amateurs were doing better than anyone had realised ? they were actually spotting 20 per cent of comets. There are therefore far fewer undiscovered comets.

?The new data allowed us to count the number of faint and far-away comets that the amateurs had missed. And we found that they were pretty rare,? Dr Francis said.

These results apply to comets coming from beyond the orbit of Pluto, which is where most comets live. The Earth is still at risk of being hit by asteroids, and by so-called short-period comets ? ones that come past repeatedly, like Halley?s comet.

?But asteroids and short-period comets come past again and again, so if we?re clever enough we can find them all and predict which, if any, will hit the Earth,? said Dr Francis. ?If we find one on a collision course with the Earth, we would normally have hundreds of years warning in which to do something about it, like deflecting the asteroid.

?The comets coming from beyond Pluto, so called long-period comets, are nastier, as they are totally unpredictable, and if we see one on a collision course we?d have at best one or two years warning ? not long enough to do anything.?

Dr Francis? research has been accepted for publication in the Astrophysical Journal. It was based on computer simulations, published data from the Lincoln Near Earth Asteroid Research Project at White Sands Missile Range in New Mexico, and on data from amateur astronomers around the world.

Original Source: ANU News Release

Posted on by Fraser Cain

Hubble’s View of the Boomerang Nebula

Boomerang Nebula. Image credit: STScI/AURA Click to enlarge
The Hubble Space Telescope has “caught” the Boomerang Nebula in these new images taken with the Advanced Camera for Surveys. This reflecting cloud of dust and gas has two nearly symmetric lobes (or cones) of matter that are being ejected from a central star. Over the last 1,500 years, nearly one and a half times the mass of our Sun has been lost by the central star of the Boomerang Nebula in an ejection process known as a bipolar outflow. The nebula’s name is derived from its symmetric structure as seen from ground-based telescopes. Hubble’s sharp view is able to resolve patterns and ripples in the nebula very close to the central star that are not visible from the ground.

Astronomers are uncertain of the cause of bipolar outflow in this, and many other, young nebulae like the Boomerang. It may be that a disk of slow-moving material is situated around the equator of the star, thereby blocking more rapidly moving ejected material there, and allowing only matter closer to the poles to be ejected. Another consideration may be that magnetic fields are responsible for constraining the material and thus causing the double-lobed shape of the nebula.

Bipolar outflows are seen to occur both from very young stars (“protostars”) that are still in the process of collapsing and forming, and from old stars nearing the ends of their lives that have become bloated red giants. The Boomerang is believed to be the ejected outer layers from an old red giant. Each lobe of the Boomerang Nebula is nearly one light-year in length, making the total length of the nebula half as long as the distance from our Sun to our nearest neighbors- the Alpha Centauri stellar system, located roughly 4 light-years away.

These images of the Boomerang were taken in early 2005 with the Advanced Camera for Surveys onboard Hubble. A visible light filter was used in combination with a series of polarization filters. Similar to polarizing sunglasses that are used to reduce the amount of scattered light that enters our eyes on a sunny day, the telescope’s polarizing filters allow only light of a specific polarization angle to pass through to the camera’s detector. By combining images taken at different polarization angles, astronomers can study light scattering in the nebula and the properties of the small dust particles responsible for the scattering. Colors were assigned to represent different polarization components, and then those colors were adjusted to accentuate features in the nebula, resulting in the multi-hued composite image.

The Boomerang Nebula is located about 5,000 light-years from Earth in the direction of the Southern constellation Centaurus. Submillimeter radio measurements made in 1995 show the deep interior of the nebula to have a temperature of only one degree Kelvin above absolute zero, with absolute zero equal to nearly -460 degrees Fahrenheit. This makes the inner regions of the Boomerang Nebula one of the coldest known places in the universe.

Original Source: Hubble News Release