Posted on by Fraser Cain

Supernova in Galaxy NGC 1559

Supernova 2005dh and NGC 1559. Image credit: ESO Click to enlarge
The southern Reticulum constellation certainly isn’t a big hit for amateur astronomers. This tiny, bleak and diamond-shaped constellation, not far on the sky from the Large Magellanic Cloud, is often overlooked. But recently, astronomers had a closer look at a galaxy situated inside it. And more precisely at an exploding star hosted by the spiral galaxy NGC 1559.

On the night of August 4, 2005, Australian amateur astronomer Reverend Robert Evans discovered a supernova just North of the galaxy with his 0.31-m telescope. The supernova – the explosion of a star – was of magnitude 13.8, that is, only 20 times fainter than the entire host galaxy. Being the 104th supernova discovered in 2005, it received the name SN 2005df. Noticeably, Evans had already discovered 2 other supernovae in the same galaxy: in 1984 (SN 1984J) and in 1986 (SN 1986L).

The following night, astronomer Marilena Salvo and her Australian colleagues classified the supernova as a somewhat unusual type Ia supernova, caught probably 10 days before it reached its maximum brightness. Such a supernova is thought to be the result of the explosion of a small and dense star – a white dwarf – inside a binary system. As its companion was continuously spilling matter onto the white dwarf, the white dwarf reached a critical mass, leading to a fatal instability and the supernova.

These are exactly a kind of supernovae in which Dietrich Baade, Ferdinando Patat (ESO), Lifan Wang (Lawrence Berkeley National Laboratory, USA), and their colleagues are interested. In particular, they study the polarization properties of this kind of supernova in order to learn more about their asphericity, which holds important clues to the detailed physics that governs this terminal catastrophe in the life of such stars.

Having an accepted observing programme that uses the FORS1 multi-mode instrument on Kueyen, one of the four Unit Telescopes of ESO’s 8.2m Very Large Telescope at Cerro Paranal, they triggered a Target of Opportunity request so that on-duty astronomers at the VLT could observe this supernova, which was done on August 6.

From a very first analysis of their data, Wang and his colleagues found that SN 2005df resembles closely another supernova they had studied before, SN 2001el, whose explosion they showed was significantly asymmetric.

NGC 1559 is a SBc(s)-type spiral galaxy located about 50 million light-years away, that weighs the equivalent of about 10,000 million of suns, and is about 7 times smaller than our Milky Way: on the sky, it measures about 4×2 arcmin2. Receding from us at a speed of about 1,300 km/s, it is a galaxy of the Seyfert type. Such galaxies are characterized by a bright nucleus that radiates strongly in the blue and in the ultraviolet. Astronomers think that about 2 solar masses of gas per year are transformed into stars in this galaxy. Like most galaxies, NGC 1559 probably contains a black hole in its centre, which should have a mass that is equivalent to 300,000 suns.

Original Source: ESO News Release

Posted on by Fraser Cain

Future Ice Free Summers in the Arctic

Arctic ocean. Image credit: NASA/GSFC Click to enlarge
The current warming trends in the Arctic may shove the Arctic system into a seasonally ice-free state not seen for more than one million years, according to a new report. The melting is accelerating, and a team of researchers were unable to identify any natural processes that might slow the de-icing of the Arctic.

Such substantial additional melting of Arctic glaciers and ice sheets will raise sea level worldwide, flooding the coastal areas where many of the world’s people live.

Melting sea ice has already resulted in dramatic impacts for the indigenous people and animals in the Arctic, which includes parts of Alaska, Canada, Russia, Siberia, Scandinavia and Greenland.

?What really makes the Arctic different from the rest of the non-polar world is the permanent ice in the ground, in the ocean and on land,? said lead author University of Arizona geoscientist Jonathan T. Overpeck. ?We see all of that ice melting already, and we envision that it will melt back much more dramatically in the future as we move towards this more permanent ice-free state.?

The report by Overpeck and his colleagues is published in the Aug. 23 Eos, the weekly newspaper of the American Geophysical Union. A complete list of authors and their affiliations is at the end of this release.

The report is the result of weeklong meeting of a team of interdisciplinary scientists who examined how the Arctic environment and climate interact and how that system would respond as global temperatures rise. The workshop was organized by the NSF Arctic System Science Committee, which is chaired by Overpeck. The National Science Foundation funded the meeting.

The past climates in the Arctic include glacial periods, where sea ice coverage expanded and ice sheets extended into Northern America and Europe, and warmer interglacial periods during which the ice retreats, as it has during the past 10,000 years.

By studying natural data loggers such as ice cores and marine sediments, scientists have a good idea what the ?natural envelope? for Arctic climate variations has been for the past million years, Overpeck said.

The team of scientists synthesized what is currently known about the Arctic and defined key components that make up the current system. The scientists identified how the components interact, including feedback loops that involve multiple parts of the system.

?In the past, researchers have tended to look at individual components of the Arctic,? said Overpeck. ?What we did for the first time is really look at how all of those components work together.?

The team concluded that there were two major amplifying feedbacks in the Arctic system involving the interplay between sea and land ice, ocean circulation in the North Atlantic, and the amounts of precipitation and evaporation in the system.

Such feedback loops accelerate changes in the system, Overpeck said. For example, the white surface of sea ice reflects radiation from the sun. However, as sea ice melts, more solar radiation is absorbed by the dark ocean, which heats up and results in yet more sea ice melting.

While the scientists identified one feedback loop that could slow the changes, they did not see any natural mechanism that could stop the dramatic loss of ice.

?I think probably the biggest surprise of the meeting was that no one could envision any interaction between the components that would act naturally to stop the trajectory to the new system,? Overpeck said. He added that the group investigated several possible braking mechanisms that had been previously suggested.

In addition to sea and land ice melting, Overpeck warned that permafrost?the permanently frozen layer of soil that underlies much of the Arctic?will melt and eventually disappear in some areas. Such thawing could release additional greenhouse gases stored in the permafrost for thousands of years, which would amplify human-induced climate change.

Overpeck said humans could step on the brakes by reducing carbon dioxide emissions. ?The trouble is we don?t really know where the threshold is beyond which these changes are inevitable and dangerous,” Overpeck said. ?Therefore it is really important that we try hard, and as soon as we can, to dramatically reduce such emissions.?

Original Source: University of Arizona News Release

Posted on by Fraser Cain

What’s Up This Week – August 22 – August 28, 2005

M8. Image credit: N.A. Sharp, REU Program, NOAO/AURA/NSF. Click to enlarge.
Monday, August 22 – Tonight let’s start by watching the dance of the ecliptic as Venus and Jupiter have now drawn within a fist’s width (10 degrees) of each other about 90 minutes after sunset. They’re about to get much closer!

With the later rise of tonight’s Moon, let’s take this opportunity to visit a deepsky object that’s great in either telescopes or binoculars. Are you ready to swim in the “Lagoon”?

Easily located about three finger width’s above the tip of the teapot’s spout – Al Nasal – the M8 is one of Sagittarius’ premier objects. This combination of emission/reflection and dark nebula could only get better as an open cluster is also involved. Spanning a half a degree of sky, this gem is loaded with features. One of the most prominent is a curving dark channel that divides the area nearly in half. On its leading (western) side you will note two bright stars. It is believed that the southern-most of this pair (9 Sagittarii) is the illuminating star of the nebula. One the trailing (eastern) side, is a loose collection of stars designated as NGC 6530 which contains 18 erratically changing variables known as “flare stars”. This is a very young group of stars, and still in the process of formation. For large scopes, and those with filters, look for many small patches of dark nebulae called “globules”. These are believed to be “protostar” regions – areas where new stars are undergoing formation. Return again to star 9 Sagittarii and look carefully at a very concentrated portion of the nebula to its west/southwest. This region is known as the “Hourglass” and it is a source of radio emission. How cool is that?!

Tuesday, August 23 – If you’re up before sunrise this morning, be sure to check out the eastern horizon. Can you spot Saturn with Mercury below it? Tiny Mercury has now reached its greatest elongation from the Sun (18 degrees) and is now as high in the pre-dawn sky as it will get.

Grab your binoculars tonight and head towards Sagittarius. About a thumb’s length northeast of the top star in the teapot’s “lid” – Kaus Borealis, you’ll discover a fine open cluster that’s equally impressive in a telescope. The M25 is a scattered galactic cluster that contains a cephid variable – U Sagittarii. This one is a quick change artist, going from magnitude 6.3 to 7.1 in less than seven days. Keep an eye on it over the next few weeks by comparing it to the other cluster members. Variable stars are fun!

Wednesday, August 24 – Around 3 hours after sunset tonight, we’re going to dispel a myth. At this time you will note a waning Moon, about 2/3 illuminated has already risen and that Mars is less than a fist’s width to its lower right. Just how big is it?

We’ve all heard the email scam that’s been around on the internet telling about this year’s Mars apparition. First let’s start with the myth. According to them, Mars will be 34,649,589 miles from Earth and appear as large as the full Moon in the sky! I’m sorry, but there’s something wrong with that equation. Let’s have a look at why…

This illustrates the size of our Earth, Moon and Mars. As you can see, Mars is about twice the size of our Moon. Now let’s use some logic. We know the the Moon is approximately one quarter of a million miles away, and we know how big it appears in our sky. For Mars to appear that large, it would need to be a million miles away! No matter how close we might come , it’s never going to be that close. Now let’s look at some facts…

During 2005 Mars will not be as close to Earth as it was in 2003. Fortunately, this year it will be higher in our sky, allowing everyone the opportunity to see and enjoy it. Mars is the only planet with a surface that can be plainly seen with details for even a small telescope and in 2005 and 2006 it will be at its best. Why? This time it will be above the celestial equator. This is good news for northern observers! Mars will be 32 degrees higher than it was in 2003, meaning we have far less of our own atmosphere to view through. This should provide considerably better observations of the Red Planet.

With a 4″ telescope and good conditions, you should be able to see large surface features, bright clouds, and the haze in the Martian atmosphere. Perhaps there will be a large dust storm, or you’ll witness the polar caps change. With a 6″ to 10″ telescope, the features will remain pretty much the same, but you’ll be able to follow them longer as Mars begins to shrink again. Larger scopes will pick out even more subtle features.

At first, your views may not be very exciting, but don’t stop watching. The Red Planet’s closest approach to Earth occurs at 04:21 UT on October 30th reaching its maximum diameter until November 6th. Of all the worlds we can observe, Mars is the most “Earth-like” with its changing seasons and polar caps. To the unaided eye, it will appear like a bright reddish star, but will lose its color to a faded orange in the eyepiece. Just like the Moon, it’s many features have been mapped and there are several on-line sites to help you get the most out of your Mars experience. Enjoy!

Thursday, August 25 – On this date in 1981, Voyager 2 made a fly- by of Saturn. Eight years later in 1989, Voyager 2 flew by Neptune on this date. Why don’t we make a “date” tonight to have a look at this distant blue world? After just having passed opposition on August 8, the gas giant is still holding a respectable magnitude 8 and can even be picked out with binoculars. You’ll find it northeast of Theta Capricornii.

Friday, August 26 – With plenty of time to spare before the Moon rises, let’s have a look at a great binocular target and a treasure trove for the telescope – M24. Located just above the top star in the teapot’s lid – Kaus Borealis – the M24 is often referred to as the “Small Sagittarius Star Cloud”. This vast region is easily seen unaided from a dark sky site and is a stellar profusion in binoculars. Telescopes will find an enclosed galactic cluster – NGC 6603 – on its northern border. For those of you who prefer a challenge, look for Barnard Dark Nebula, B92, just above the central portion.

Saturday, August 27 – With tonight’s dark sky, we’ll be undertaking a slightly more difficult study – M20.

Located about another finger width above previous study, M8, the “Trifid” nebula will appear in smaller telescopes as a double star with a faint nebulosity surrounding it. At low power, attendant open cluster M21 can often be squeezed into the same field of view. As aperture approaches the 8″ to 10″ range, so does resolution, and the “double” star will now reveal itself to be a triple (multiple) system – HN 40. The actual “Trifid” pattern that most of us recognize is in the southern portion of a much larger nebula – the region surrounding HN 40. These dark, dissecting dust lanes move off to meet space at the structure’s east and west edges, while the southernmost dustlane ends in brightest portion of the nebula. With much larger scopes, the M20 will show differences in concentration in each of the lobes along with embedded stars. It requires a dark night, but the “Trifid” is worth the hunt!

Sunday, August 28 – In 1789 on this day, Sir William Herschel discovered Saturn’s moon – Enceladus. So where is the “Ring King”? Then get thee up before dawn and look! Saturn has now risen almost a handspan above dawn’s early light. Can you still spot Mercury?

Next week means much darker skies and an opportunity to explore some of the summer’s finest deep sky objects. Until then? May all your journeys be at light speed! …~Tammy Plotner

Posted on by Fraser Cain

Pandora Hovers Above the Rings

Saturn’s moon Pandora. Image credit: NASA/JPL/SSI Click to enlarge
While close to Saturn in its orbit, Cassini stared directly at the planet to find Saturn’s moon Pandora in the field of view. The F ring shepherd moon is gliding towards the right in this scene. The F ring is thinly visible just above the main rings. Pandora is 84 kilometers (52 miles) across.
Near the lower left, some variation in the height of Saturn’s cloud tops can be detected. This effect is often visible near the terminator (the day and night boundary), where the Sun is at a very low angle above Saturn’s horizon.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 16, 2005, at a distance of approximately 1.3 million kilometers (800,000 miles) from Saturn. The image scale is about 8 kilometers (5 miles) per pixel on Saturn and about 6 kilometers (4 miles) per pixel on Pandora.

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

Asteroid Close Call Will Be a Gain for Science

Asteroid. Image credit: U.S. Geological Survey Click to enlarge
A University of Michigan-led research team has discovered that for the first time in history, scientists will be able to observe how the Earth’s gravity will disrupt a massive asteroid’s spin.

Scientists predict a near-miss when Asteroid 99942 Apophis, also known as the 2029 meteor, passes Earth in 2029. An asteroid flies this close to the planet only once every 1,300 years. The chance to study it will help scientists deal with the object should it threaten collision with Earth.

Only about three Earth diameters will separate Apophis and Earth when the 400-meter asteroid hurtles by Earth’s gravity, which will twist the object into a complex wobbling rotation. Such an occurrence has never been witnessed but could yield important clues to the interior of the sphere, according to a paper entitled, “Abrupt alteration of the spin state of asteroid 99942 Apophis (2004 MN4) during its 2029 Earth flyby,” accepted for publication in the journal Icarus.

The team of scientists is led by U-M’s Daniel Scheeres, associate professor of aerospace engineering, and includes U-M’s Peter Washabaugh, associate professor of aerospace engineering.

Apophis is one of more than 600 known potentially hazardous asteroids and one of several that scientists hope to study more closely. In Apophis’ case, additional measurements are necessary because the 2029 flyby could be followed by frequent close approaches thereafter, or even a collision.

Scheeres said not only is it the closest asteroid flyby ever predicted in advance, but it could provide a birds-eye view of the asteroid’s “belly.”

“In some sense it’s like a space science mission ‘for free’ in that something scientifically interesting will happen, it will be observable from Earth, and it can be predicted far in advance,” Scheeres said.

If NASA places measuring equipment on the asteroid’s surface, scientists could for the first time study an asteroid’s interior, similar to how geologists study earthquakes to gain understanding of the Earth’s core, Scheeres said. Because the torque caused by the Earth’s gravitational pull will cause surface and interior disruption to Apophis, scientists have a unique opportunity to observe its otherwise inaccessible mechanical properties, Scheeres said. Throwing the asteroid off balance could also affect its orbit and how close it comes to Earth in future years.

“Monitoring of this event telescopically and with devices placed on the asteroid’s surface could reveal the nature of its interior, and provide us insight into how to deal with it should it ever threaten collision,” Scheeres said.

The asteroid will be visible in the night sky of Europe, Africa and Western Asia.

The asteroid was discovered late last year and initially scientists gave it a 1-in-300 chance of hitting the Earth on April 13, 2029. Subsequent analysis of new and archived pre-discovery images showed that Apophis won’t collide with Earth that day, but that later in 2035, 2036, and 2037 there remains a 1-in-6,250 chance that the asteroid could hit Earth, Scheeres said. Conversely, that’s a 99.98 percent chance that the asteroid will miss Earth.

The asteroid is relatively small, about the length of three football fields. If it hit it wouldn’t create wide-scale damage to the Earth, but would cause major damage at the impact site, Scheeres said.

The team of scientists also includes Lance Benner and Steve Ostro of NASA’s Jet Propulsion Laboratory, Alessandro Rossi of ISTI-CNR, Italy, and Francesco Marzari of the University of Padova, Italy.

U-M University News Release

Posted on by Fraser Cain

Proof of Life?

Mars south polar cap. Image credit: NASA/JPL/MSSS Click to enlarge
Pamela Conrad, an astrobiologist with NASA’s Jet Propulsion Laboratory, has traveled to the ends of the Earth to study life. Conrad recently appeared in James Cameron’s 3-D documentary “Aliens of the Deep,” where she and several other scientists investigated strange creatures that inhabit the ocean floor.

On June 16, 2005, Conrad gave a lecture called, “A Bipolar Year: What We Can Learn About Looking for Life on Other Planets By Working in Cold Deserts.”

In part 2 of this edited transcript, Conrad describes how her work in cold deserts could aid the search for alien life.

“If we were to find life on Mars, and that life lived in the rocks, how would we study it? You can’t answer that question unless you first do some experiments on Earth. And that’s what we’re doing in the Arctic and in the Antarctic.

In the Arctic we looked at a volcano about a 150 to 200 thousand years old, made of weathered basalt. It’s very interesting weathered basalt, because it contains minerals that look very much like some of the unexplainable minerals in the controversial martian meteorite that was described to have fossilized life in it.

In the Arctic site that we went to — Svalbard, Norway — there are polar bears. So when you go to the Arctic, you have to have some training in shooting. They don’t want you to kill polar bears, but they want you to be able to do so if he’s about to kill you. So we started our expedition to the Arctic with a half-day of gun training. It was fun shooting at paper targets, but I don’t know what I’d do if I were confronted with a polar bear looking at me with dinner in his eyes.

There are no polar bears in the Antarctic, but the sea life is abundant and diverse. At McMurdo Base, there are penguins, there are birds called skua, there are a couple of different types of seals. As you go farther away from the base by the shore, you get to places that are desolate. We investigated a place in the McMurdo Dry Valleys called Battleship Promontory. The rocks there are sandstone, and they were originally deposited underwater. Inside these rocks, thriving layered communities of microbes make their existence. They freeze solid during the winter and come back to life during the summer. Of course, the summer at its most exuberant heat wave only gets to be about 10 degrees Centigrade.

NASA’s strategy for looking for life is to first look around quickly, and process a lot of information. When you get to the interesting stuff, you might take a longer amount of time, and do it more carefully with higher resolution. You wouldn’t want to do something really destructive first, because you might destroy the thing you’re trying to study. You want to be as minimally invasive as possible. Some techniques are very invasive: taking a hammer and whacking on a rock and breaking it into pieces certainly makes you unable to look at the basic overall structure, the geomorphology, of that rock. So when you’re looking for life in rock, if you’re trying to be non-destructive, you can’t crack open the rock and look inside. So there has to be some kind of clue of life on the surface of the rock.

Porphyrins are a ubiquitous class of naturally occurring compounds with many important biological representatives including hemes, chlorophylls, and several others. Life anywhere is going to have some sort of electron transport or energy harnessing system. The common ones on Earth are based on porphyrins, which have very specific shapes.

We would like to bring samples back from places like Mars, but right now we don’t know how to do that. In the future, we will do that, but then it would be a very long experiment. We have to develop the technology to do it, we have to get to Mars safely, we have to get the samples, and we have to safely get it back. That’s a complex problem.

Eventually, there will be human exploration. I want to go to every cool place I can, but I don’t think I’ll go to Mars anytime soon. But there are a lot of people who want to go to other planets, and as we listen to the different strategies and paths that NASA takes, I’m sure that that will happen in time. Right now, I’m focussing on things that might prepare us for the type of solar system exploration that we’re doing right now: sending out a spacecraft, landing it, and doing an experiment.

So my team is developing strategies for life detection, using methods that are non-destructive and quick. We survey the landscape with a minimally invasive tool, we look for the contrast in the chemistry of the rock and the chemistry of organisms that might be on or in the rock. We do it in cold deserts because cold deserts are analogous to the kind of environment we find on Mars. Mars is much drier and much colder, but that’s about as close as we can get here.

My group has been working with an optical technique. I like to describe it as the black light you can buy at PetCo, where you shine the light on the carpet to look for dog or cat pee. Only ours is a little bit higher tech and more specific than that, because there isn’t any dog or cat pee in the areas where we go. Our technique is called “laser-induced native fluorescence.” You take a very short wavelength of light – an invisible wavelength deep into the ultraviolet – and you illuminate a spot. If that spot has organic molecules, that spot glows. And the color of the glow tells you something about what kind of molecule it is, how big it is, how complicated it is. And it’s really cool because it’s fast – you can do this in 50 microseconds. Even though ultraviolet light can be damaging, we have a very short blast. So this is a very minimally invasive technique, because it doesn’t harm living things. The microbes that we’ve detected using this method don’t die.

The machine is about the size of a shoebox, and you can take it anywhere you want to immediately tell where you have life and where you don’t.

We’ve used this tool in the Arctic, sticking it into holes to determine whether or not certain minerals have any organic molecules associated with them – the specific organic molecules that might be associated with the presence of microbes. That tells us whether to grab any rocks and take them back to the lab to look for organisms. We’ve also used the tool on a manipulator arm of a deep-sea submersible and detected organic molecules coming out of hydrothermal vents on the sea floor.

In Antarctica, the organisms live in a certain type of rock that has a lot of pore space to hold water. That means they’re better able to maintain hydration. Temperatures in the rock swing, but not as wildly as the outside air because of heat that’s absorbed by the rock during the day. Also, the kind of minerals that make up that rock are transparent to ultraviolet light. If the basis of your food chain is photosynthesis, then you’ve got be underneath a mineral that transmits light.

There are different kinds of organisms that live in the rock. The kind of organism that lives in the pores spaces of rock don’t go very deep — maybe a centimeter and a half if you have a really thick community. But you do see chemical evidence going a few centimeters deeper into the rock.

There are other kinds of organisms that don’t live in the pore spaces. They migrate into the cracks in rocks. They are called “chasmoliths.” They typically do chemosynthesis, that is, they rip out chemistry associated with the rock, and they either oxidize some ion, or reduce some other ion, and this whole cycle of oxidizing something and reducing something is akin to the respiration we do. Since it doesn’t involve photosynthesis, they don’t need light, so they can go deeper into the rock. But the chemistry in the rock influences how deeply they can go — these tiny organisms have a community structure that has a specific set of chemical conditions that support it. If you change that set of chemical conditions, you have a whole different environment. Another limitation is you can’t go too deep and use up too much space, or thermodynamically you can’t continue to do chemistry because you’ll drown in your own poop. That’s an unfortunate state of affairs.

You can tell the difference between one bacterium and another with our instrument, because different chemicals are on the surface of the organisms. Just using fluorescence can tell you the difference between basic types of bacteria. If you have a spore, and you want know what species you have, you use other techniques, like looking at the vibrational properties of the atomic bond.

One of the cool things about looking for microbial life on Earth is that microbes are everywhere. Most of the biodiversity on Earth is microbial, and they can live in challenging environments. You have to give them credit for being clever in terms of coming up with adaptive strategies to cope with stressful environments.

When we think of looking for fossils of past life, we tend to think of stuff like dinosaur bones. Astrobiologists don’t really expect to find dinosaurs on Mars, although I do have a National Enquirer cover that differs.

But you can find fossil structures in rocks, created from organisms that were in the sediment as it was being lithified – made into a rock. You can also try to find chemical fossils, signs that there was life there. There are some chemicals that are really big molecules that are very hardy and withstand a lot. We just have to be clever enough to distinguish the chemistry associated with the rock from the chemistry associated with the living things.”

Original Source: NASA Astrobiology

Posted on by Fraser Cain

Evidence of Our Violent Early Solar System

Meteorite. Image credit: NASA/JPL/Cornell Click to enlarge
A U of T scientist has found unexpectedly ?young? material in meteorites ? a discovery that breaks open current theory on the earliest events of the solar system.

A paper published today in the August issue of Nature reports that the youngest known chondrules ? the small grains of mineral that make up certain meteorites ? have been identified in the meteorites known as Gujba and Hammadah al Hamra.

Researchers who have studied chondrules generally agree that most were formed as a sudden, repetitive heat, likely from a shock wave, condensed the nebula of dust floating around the early Sun. Thinking that an analysis of the chondrules in Gujba and Hammadah al Hamra would be appropriate for accurately dating this process, U of T geologist Yuri Amelin, together with lead author Alexander Krot of the University of Hawaii, studied the chondrules? mineralogical structure and determined their isotopic age. ?It soon became clear that these particular chondrules were not of a nebular origin,? says Amelin. ?And the ages were quite different from what was expected. It was exciting.?

Amelin explains that not only were these chondrules not formed by a shock wave, but rather emerged much later than other chondrules. ?They actually post-date the oldest asteroids,? he says. ?We think these chondrules were formed by a giant plume of vapour produced when two planetary embryos, somewhere between moon-size and Mars-size, collided.?

What does this mean in the grand scheme of things? The evolution of the solar system has traditionally been seen as a linear process, through which gases around the early sun gradually cooled to form small particles that eventually clumped into asteroids and planets. Now there is evidence of chondrules forming at two very distinct times, and evidence that embryo planets already existed when chondrules were still forming. ?It moves our understanding from order to disorder,? Amelin admits. ?But I?m sure that as new data is collected, a new order will emerge.?

Financial support for this project was provided by NASA and the Canadian Space Agency.

Original Source: University of Toronto

Posted on by Fraser Cain

SOHO Gets Its 1,000th Comet

999th and 1000th comets identified in SOHO images. Image credit: ESA/NASA Click to enlarge
On 5 August 2005, the ESA/NASA SOHO spacecraft achieved an incredible milestone – the discovery of its 1000th comet!

The 1000th comet was a Kreutz-group comet spotted in images from the C3 coronagraph on SOHO’s LASCO instrument by Toni Scarmato, from Calabria, Italy.
Just five minutes prior to discovering SOHO’s 1000th comet, Toni had also spotted SOHO’s 999th comet! These comets take Toni’s personal number of SOHO discoveries to 15.

Many SOHO comet discoveries have been by amateurs using SOHO images on the internet, and SOHO comet hunters come from all over the world. Toni Scarmato, a high school teacher and astrophysics graduate of the University of Bologna, said: ?I am very happy for this special experience that is possible thanks to the SOHO satellite and NASA-ESA collaboration.

“I want to dedicate the SOHO 1000th comet to my wife Rosy and my son Kevin to compensate for the time that I have taken from them to search for SOHO comets.”

The SOHO team also held a contest over the internet to guess the time when the 1000th comet would be discovered. The contest winner is Andrew Dolgopolov of Dublin, Ireland, who guessed the time of the comet?s closest approach to the Sun (perihelion time) within 22 minutes.

SOHO, the Solar and Heliospheric Observatory , is a joint effort between NASA and ESA and is now in its tenth year of operation. Although it was originally planned as a solar and heliospheric mission, it was optimistically hoped that LASCO might observe at least a handful of ?sungrazer? comets, based on the success of the SOLWIND coronagraph in the late 1970s and 1980s, which discovered a small number of very bright Kreutz-group comets.
It was not long after SOHO began sending down a steady stream of data in 1996 that SOHO scientists spotted a Kreutz-group comet in LASCO images. Soon, several more comets had been found and word started to spread of SOHO?s potential as a comet discoverer.

In 2000, amateur astronomer Mike Oates started to search the SOHO images, which had recently became available via the internet. He soon revealed just how much potential SOHO had by quickly spotting over 100 comets in LASCO images.

Almost all SOHO’s comets are discovered using images from its LASCO instrument, the Large Angle and Spectrometric Coronagraph. LASCO is used to observe the faint, multimillion-degree outer atmosphere of the Sun, called the corona. A disk in the instrument is used to make an artificial eclipse, blocking direct light from the Sun so the much fainter corona can be seen. Sungrazing comets are discovered when they enter LASCO’s field of view as they pass close by the Sun.

As time passed, more professional astronomers, as well as amateur enthusiasts from all over the world, joined the search for SOHO comets. In August 2002, Rainer Kracht (now the leading SOHO comet discoverer, with over 150 SOHO comets) spotted SOHO?s 500th comet. This in itself was an achievement that none of the SOHO/LASCO scientists ever imagined would, or could, happen.

However, just three years later, SOHO, with 1000 comet discoveries, is responsible for almost half of all officially recorded comets in history! Add to this the fact that the SOHO mission has completely revolutionised solar physics and the understanding of the Sun, and it shows just how truly amazing the SOHO spacecraft is!

Original Source: ESA Portal

Posted on by Fraser Cain

Next Shuttle Will Fly in March 2006

Discovery lifts off on the 26th, July. Image credit: NASA/Bill Ingalls Click to enlarge
NASA is targeting March for the next Space Shuttle mission (STS-121). The mission will be the second test flight to the International Space Station in the Shuttle Return to Flight sequence.

NASA Administrator Michael Griffin and Associate Administrator for Space Operations Bill Gerstenmaier made the announcement today at a news conference at the agency’s headquarters in Washington.

“We are giving ourselves what we hope is plenty of time to evaluate where we are,” said Administrator Griffin. “We don’t see the tasks remaining before us being as difficult as the path behind us.”

Based on NASA’s self-imposed optimum lighting requirements, the earliest possible launch opportunity for the STS-121 mission is March 4, 2006. The Space Shuttle Discovery will be used for the mission, instead of Space Shuttle Atlantis.

Moving toward a no earlier than March launch for STS-121 will allow engineering teams more time to properly evaluate the issue of large pieces of insulating foam that came off Discovery’s external fuel tank during launch last month.

Targeting March also allows the Space Shuttle Program to put itself into a better posture for future Shuttle missions to the Space Station. Changing Orbiters for the STS-121 mission enables use of Atlantis for the following mission, STS-115, which will resume assembly of the Station.

The switch frees Atlantis to fly the remaining Space Station truss segments, which are too heavy for Discovery, in 2006. By changing the Orbiter line up, the Shuttle program will not have to do two back-to-back missions with Atlantis, as previously scheduled.

“It really makes sense to move to the March timeframe,” Gerstenmaier said. “We’re looking at the Shuttle missions to support the most robust flight sequence for the Space Station and to make the whole sequence flow better. This extra time helps us make sure that all the work we need to do fits and that there are no other issues.”

Discovery’s recent mission, STS-114, and the STS-121 mission are test flights. They will enable NASA to evaluate new safety procedures and equipment, giving the agency greater confidence that the Shuttle can be flown safely through its planned retirement date of 2010.

The external fuel tanks at NASA’s Kennedy Space Center in Florida will be shipped back to the Michoud Assembly Facility in Louisiana for tests and potential modifications.

For information about the STS-114 Return to Flight mission and future Shuttle flights, visit: http://www.nasa.gov/returntoflight

Original Source: NASA News Release

Posted on by Fraser Cain

Newborn Black Holes

Artist’s impression of Swift spacecraft. Image credit: Spectrum Astro/NASA Click to enlarge
Scientists using NASA’s Swift satellite say they have found newborn black holes, just seconds old, in a confused state of existence. The holes are consuming material falling into them while somehow propelling other material away at great speeds.

These black holes are born in massive star explosions. An initial blast obliterates the star, yet the chaotic black hole activity appears to re-energize the explosion several times in just a few minutes. This is a dramatically different view of star death, one that entails multiple explosive outbursts and not just a single bang, as previously thought.

“Stars are exploding two, three and sometimes four times in the first minutes following the initial explosion,” said Prof. David Burrows of Penn State, University Park, Pa. “First comes a blast of gamma rays followed by intense pulses of X-rays. The energies involved are much greater than anyone expected,” he added.

Scientists have seen this phenomenon in nearly half of the longer gamma-ray bursts detected by Swift. These gamma-ray bursts are the most powerful explosions known. They are forerunners of a massive star explosion called a hypernova, which is bigger than a supernova. Using Swift, scientists are finally able to see gamma-ray bursts within minutes after the trigger, instead of hours or days, and are privy to newborn black hole activity.

Until this latest Swift discovery, scientists assumed a simple scenario of a single explosion followed by a graceful afterglow of the dying embers. The new scenario of a blast followed by a series of powerful “hiccups” is particularly evident in a gamma-ray burst from May 2, 2005, named GRB 050502B. This burst lasted 17 seconds during the early morning hours in the constellation Leo. About 500 seconds later, Swift detected a spike in X-ray light about 100 times brighter than anything seen before.

Previously there had been hints of an “X-ray bump” between the burst and afterglow in previous gamma-ray bursts, coming a minute or so after the burst. Swift has seen more than one dozen clear cases of multiple explosions. There are several theories to describe this newly discovered phenomenon and most point to the presence of a newborn black hole.

“The newly formed black hole immediately gets to work,” said Prof. Peter Meszaros of Penn State, head of the Swift theory team. “We aren’t clear on the details yet, but it appears to be messy. Matter is falling into the black hole, which releases a great amount of energy. Other matter gets blasted away from the black hole and flies out into the interstellar medium. This is by no means a smooth operation,” he added.

Another theory is the jet of material shooting away from the dead star starts to fall back onto itself, creating shockwaves in the jet core that ram together blobs of gas and produce X-ray light.

“None of this was realized before simply because we couldn’t get to the scene of the explosion fast enough,” said Dr. Neil Gehrels of NASA Goddard Space Flight Center, Greenbelt, Md., Swift principal investigator. “Swift has the unique ability to detect bursts and turn its X-ray and ultraviolet-optical telescopes to the explosion’s embers within minutes. As such, Swift is detecting new burst details that might rewrite theory,” Gehrels said.

Swift carries three main instruments: the Burst Alert Telescope (BAT); X-ray Telescope (XRT); and the Ultraviolet/Optical Telescope (UVOT). Today’s announcement is based largely on XRT data. The XRT was built at Penn State with partners at the Brera Astronomical Observatory in Italy and the University of Leicester in England.

Swift was launched in November 2004. It is a NASA mission in partnership with the Italian Space Agency and the Particle Physics and Astronomy Research Council, United Kingdom. Swift is managed by Goddard. Penn State controls science and flight operations from the Mission Operations Center in University Park, Pa. The spacecraft was built in collaboration with national laboratories, universities and international partners.

A paper discussing these findings appears online today on Science Express and in the September 9 issue of Science. Burrows is lead author of the paper.

For more information about this research on the Web, visit:
http://www.nasa.gov/vision/universe/watchtheskies/double_burst.html

Original Source: NASA News Release