Posted on by Fraser Cain

Super Star Cluster Discovered in Our Own Milky Way

Super star clusters are groups of hundreds of thousands of very young stars packed into an unbelievably small volume. They represent the most extreme environments in which stars and planets can form.

Until now, super star clusters were only known to exist very far away, mostly in pairs or groups of interacting galaxies. Now, however, a team of European astronomers [1] have used ESO’s telescopes to uncover such a monster object within our own Galaxy, the Milky Way, almost, but not quite, in our own backyard!

The newly found massive structure is hidden behind a large cloud of dust and gas and this is why it took so long to unveil its true nature. It is known as “Westerlund 1” and is a thousand times closer than any other super star cluster known so far. It is close enough that astronomers may now probe its structure in some detail.

Westerlund 1 contains hundreds of very massive stars, some shining with a brilliance of almost one million suns and some two-thousand times larger than the Sun (as large as the orbit of Saturn)! Indeed, if the Sun were located at the heart of this remarkable cluster, our sky would be full of hundreds of stars as bright as the full Moon. Westerlund 1 is a most unique natural laboratory for the study of extreme stellar physics, helping astronomers to find out how the most massive stars in our Galaxy live and die.

From their observations, the astronomers conclude that this extreme cluster most probably contains no less than 100,000 times the mass of the Sun, and all of its stars are located within a region less than 6 light-years across. Westerlund 1 thus appears to be the most massive compact young cluster yet identified in the Milky Way Galaxy.

Super Star Clusters
Stars are generally born in small groups, mostly in so-called “open clusters” that typically contain a few hundred stars. From a wide range of observations, astronomers infer that the Sun itself was born in one such cluster, some 4,500 million years ago.

In some active (“starburst”) galaxies, scientists have observed violent episodes of star formation (see, for example, ESO Press Photo 31/04), leading to the development of super star clusters, each containing several million stars.

Such events were obviously common during the Milky Way’s childhood, more than 12,000 million years ago: the many galactic globular clusters – which are nearly as old as our Galaxy (e.g. ESO PR 20/04) – are indeed thought to be the remnants of early super star clusters.

All super star clusters so far observed in starburst galaxies are very distant. It is not possible to distinguish their individual stars, even with the most advanced technology. This dramatically complicates their study and astronomers have therefore long been eager to find such clusters in our neighbourhood in order to probe their structure in much more detail.

Now, a team of European astronomers [1] has finally succeeded in doing so, using several of ESO’s telescopes at the La Silla observatory (Chile).

Westerlund 1
The open cluster Westerlund 1 is located in the Southern constellation Ara (the Altar constellation). It was discovered in 1961 from Australia by Swedish astronomer Bengt Westerlund, who later moved from there to become ESO Director in Chile (1970 – 74). This cluster is behind a huge interstellar cloud of gas and dust, which blocks most of its visible light. The dimming factor is more than 100,000 – and this is why it has taken so long to uncover the true nature of this particular cluster.

In 2001, the team of astronomers identified more than a dozen extremely hot and peculiar massive stars in the cluster, so-called “Wolf-Rayet” stars. They have since studied Westerlund 1 extensively with various ESO telescopes.

They used images from the Wide Field Imager (WFI) attached to the 2.2-m ESO/MPG as well as from the SUperb Seeing Imager 2 (SuSI2) camera on the ESO 3.5-m New Technology Telescope (NTT). From these observations, they were able to identify about 200 cluster member stars.

To establish the true nature of these stars, the astronomers then performed spectroscopic observations of about one quarter of them. For this, they used the Boller & Chivens spectrograph on the ESO 1.52-m telescope and the ESO Multi-Mode Instrument (EMMI) on the NTT.

An Exotic Zoo
These observations have revealed a large population of very bright and massive, quite extreme stars. Some would fill the solar system space within the orbit of Saturn (about 2,000 times larger than the Sun!), others are as bright as a million Suns.

Westerlund 1 is obviously a fantastic stellar zoo, with a most exotic population and a true astronomical bonanza. All stars identified are evolved and very massive, spanning the full range of stellar oddities from Wolf-Rayet stars, OB supergiants, Yellow Hypergiants (nearly as bright as a million Suns) and Luminous Blue Variables (similar to the exceptional Eta Carinae object – see ESO PR 31/03).

All stars so far analysed in Westerlund 1 weigh at least 30-40 times more than the Sun. Because such stars have a rather short life – astronomically speaking – Westerlund 1 must be very young. The astronomers determine an age somewhere between 3.5 and 5 million years. So, Westerlund 1 is clearly a “newborn” cluster in our Galaxy!

The Most Massive Cluster
Westerlund 1 is incredibly rich in monster stars – just as one example, it contains as many Yellow Hypergiants as were hitherto known in the entire Milky Way!

“If the Sun were located at the heart of Westerlund 1, the sky would be full of stars, many of them brighter than the full Moon”, comments Ignacio Negueruela of the Universidad de Alicante in Spain and member of the team.

The large quantity of very massive stars implies that Westerlund 1 must contain a huge number of stars. “In our Galaxy, explains Simon Clark of the University College London (UK) and one of the authors of this study, “there are more than 100 solar-like stars for every star weighing 10 times as much as the Sun. The fact that we see hundreds of massive stars in Westerlund 1 means that it probably contains close to half a million stars, but most of these are not bright enough to peer through the obscuring cloud of gas and dust”. This is ten times more than any other known young clusterin the Milky Way.

Westerlund 1 is presumably much more massive than the dense clusters of heavy stars present in the central region of our Galaxy, like the Arches and Quintuplet clusters. Further deep infrared observations will be required to confirm this.

This super star cluster now provides astronomers with a unique perspective towards one of the most extreme environments in the Universe. Westerlund 1 will certainly provide new opportunities in the long-standing quest for more and finer details about how stars, and especially massive ones, do form.

… and the Most Dense
The large number of stars in Westerlund 1 was not the only surprise awaiting Clark and his colleagues. From their observations, the team members also found that all these stars are packed into an amazingly small volume of space, indeed less than 6 light-years across. In fact, this is more or less comparable to the 4 light-year distance to the star nearest to the Sun, Proxima Centauri!

It is incredible: the concentration in Westerlund 1 is so high that the mean separation between stars is quite similar to the extent of the Solar System.

“With so many stars in such a small volume, some of them may collide”, envisages Simon Clark. “This could lead to the formation of an intermediate-mass black hole more massive than 100 solar masses. It may well be that such a monster has already formed at the core of Westerlund 1.”

The huge population of massive stars in Westerlund 1 suggests that it will have a very significant impact on its surroundings. The cluster contains so many massive stars that in a time span of less than 40 million years, it will be the site of more than 1,500 supernovae. A gigantic firework that may drive a fountain of galactic material!

Because Westerlund 1 is at a distance of only about 10,000 light-years, high-resolution cameras such as NAOS/CONICA on ESO’s Very Large Telescope can resolve its individual stars. Such observations are now starting to reveal smaller stars in Westerlund 1, including some that are less massive than the Sun. Astronomers will thus soon be able to study this exotic galactic zoo in great depth.

More information
The research presented in this ESO Press Release will soon appear in the leading research journal Astronomy and Astrophysics (“On the massive stellar population of the Super Star Cluster Westerlund 1” by J.S. Clark and colleagues). The PDF file is available at the A&A web site. A second paper (“Further Wolf-Rayet stars in the starburst cluster Westerlund 1”, by Ignacio Negueruela and Simon Clark) will also soon be published in Astronomy and Astrophysics. It is available as astro-ph/0503303.
A Spanish press release issued by Universidad de Alicante is available on the web site of Ignacio Negueruela.

Note
[1]: The team is composed of Simon Clark (University College London, UK), Ignacio Negueruela (Universidad de Alicante, Spain), Paul Crowther (University of Sheffield, UK), Simon Goodwin (University of Wales, Cardiff, UK), Rens Waters (University of Amsterdam) and Sean Dougherty (Dominion Radio Astrophysical Observatory).

Original Source: ESO News Release

Posted on by Fraser Cain

What’s Up This Week – Mar 21 – 27, 2005

Image credit: Alwyn Botha
Monday, March 21 – For readers looking for an exceptional morning challenge with either binoculars or small scopes, try 8th magnitude comet C/2003 T4 LINEAR. On this date it will be in the same binocular field west of the M2 and continue southeast toward Beta Aquarii over the next four mornings.

Tonight the most outstanding feature on the lunar surface will be the “Bay of Rainbows” – Sinus Iridum. Take the time to power up on the area and enjoy its many wonderful features such as bright Promontoriums LaPlace to the northeast and Heraclides to the southwest. It is ringed by the Juras Mountains where you will spot crater Bianchini in the center with Sharp to its west. Look for the punctures Helicon and Le Verrier in the smooth sands of Mare Ibrium and the long, smooth “dune” of Dorsae Heim interrupted by C. Herschel.

Tuesday, March 22 – Tonight there will be two meteor showers – the Camelopardalids and the March Geminids. While the Camelopardalids have no definite peak, they have a screaming fall rate of about one per hour and are the slowest recorded meteors at 7 kps. The March Geminids were discovered in 1973 and confirmed in 1975. The fall rate is usually about 40 per hour and they are considered “slow”. With the bright skies tonight, it will be difficult to distinguish them, but trace back to the point of origin to identify which stream.

While bright Aristarchus and the graceful old Gassendi will try to steal tonight’s lunar show, continue on towards the Southern Highlands to look for the long ellipse of crater Schiller near the limb. Small crater Bayer borders its northeastern edge.

Born on this day in 1799 was Friedrich Argelander, creator of the first international astronomical organization. Argelander also compiled star catalogues and studied variable stars. With deep sky studies improbable for the next few days, why don’t we try taking a look at a variable ourselves? RT (star 48) Aurigae is a bright cephid that is located roughly halfway between Epsilon Geminorum and Theta Aurigae. This perfect example of a pulsating star follows a precise timetable of 3.728 days and fluxes by close to one magnitude.

Wednesday, March 23 – Tonight let’s travel to the far southern edge of the lunar surface to visit three craters. Past study, the lava-filled Wargentin, is bordered by shallow Nasmyth to the east and Phoclydes to the southeast. This pair makes a wonderful “impression” on the Moon, for together they look like a giant shoe print!

The first photo of the Moon was taken tonight in 1840 by J.W. Draper. (Yes, it was done in 1839 by L.J.M. Daguerre – but contained no detail.) Why don’t you try as well? Camcorders, webcams and digital cameras are inexpensive ways of experimenting and even a common disposable camera can yield surprising results when held to the eyepiece of a telescope. Circle your thumb and index finger around the pair to aid in alignment and block stray light. Just click and say “green cheese”…

Thursday, March 24 – With the lunar terminator highlighting crater Grimaldi on the western limb, let’s try our hand at a more difficult feature. To Grimaldi’s east you will see the complex structure of crater Damoiseau. Extending from a break on its western rim edge is a long surface “crack” that runs north to south between the pair. This challenging feature is known as Rima Grimaldi.

On this night in 1893, Walter Baade – the developer of the concept of stellar population – became the first human to resolve the Andromeda Galaxy’s companions into individual stars. Tonight we’ll stay within our own galaxy as we travel 85 light years away to learn about “The Little King” – Regulus.

Ranking as the twenty-first brightest star in the night sky, Alpha Leonis is a helium type star about 5 times larger and 160 times brighter than our own Sun. Speeding away from us at 3.7 kilometers per second, Regulus is also a multiple system whose 8th magnitude companion is easily seen in small telescopes. The companion is itself a double at around magnitude 13 and is a dwarf of an uncertain type. There is also a 13th magnitude fourth star in this grouping, but it is believed that it is not associated with Regulus since the “Little King” is moving toward it and will be about 14″ away in 785 years.

Friday, March 25 – Tonight is Full Moon and time to explore the bright ray systems that criss-cross its surface. One of the strongest will eminate from crater Tycho and head toward the southwest limb. If libration is favourable in your area, you might catch a glimpse of the Doerful Mountains on the Moon’s edge. This incredible mountain range comes within a kilometer of being as tall as the Himalayas. If the Earth and the Moon were the same size, we would find the Doerfuls are three times higher than Everest!

On this date in 1655, Christian Huygens was still celebrating his earlier discovery of Saturn’s rings when he made an even more important contribution – Titan. 350 years later, the probe named for Huygens is now exploring Saturn’s largest satellite and you can as well. Even small telescopes can easily see the first moon discovered in our solar system to have an atmosphere. Before you observe, try checking the current positions of Saturn’s moons so you know precisely where to look.

Saturday, March 26 – Heads up southwestern Australia! The Moon will occult Jupiter for you on this this universal date. Please check this IOTA page to see a path map and compute times for your location. For the majority of northern hemisphere viewers, you will get to see a very pleasing conjunction of the two around 1 degree apart.

With the strong influence of the Moon to the east, let’s journey this evening towards another lovely multiple system as we explore Beta Monocerotis. Located about a fist width northwest of Sirius, Beta is one of the finest true triple systems for the small telescope. At low power, the 450 light year distant white primary will show the blue B and C stars to the southeast. If skies are stable, up the magnification to split the E/W oriented pair. All three stars are within a magnitude of each other and make Beta one of the finest sights for late winter skies.

Sunday, March 27 – Tonight as the Moon rises, check the eastern limb where you will see the terminator has advanced toward the eastern edge of Mare Crisium. With the shadows throwing its mountained walls into relief, we can see where this Washington state-sized area could possibly have been impact formed. Crisium is unique simply because it does not connect to any other mare. While the walls don’t seem that high at around 450 meters, that’s comparable to taking on the Vasques Cirque vertical drop at Winter Park, Colorado… without the skis!

Until next week? Keep smiling and looking up! May all your journeys be at light speed… ~Tammy Plotner

Posted on by Fraser Cain

Seeing the Planks in Einstein’s Cross

Image credit: Hubble
Spiral galaxy PGC 69457 is located near the boundary of fall constellations Pegasus and Aquarius some 3 degrees south of third magnitude Theta Pegasi – but don’t dig out that 60mm refractor to look for it. The galaxy is actually some 400 million light years away and has an apparent brightness of magnitude 14.5. So next fall may be a good time to hook up with that “astro-nut” friend of yours who is always heading off into the sunset to get well away from city lights sporting a larger, much larger, amateur instrument…

But there are plenty of 14th magnitude galaxies in the sky – what makes PGC 69457 so special?

To begin with most galaxies don’t “block” the view of an even more distant quasar (QSO2237+0305). And should others exist, few have just the right distribution of high-density bodies needed to cause light to “bend” in a way that an otherwise invisible object is visible. With PGC 69457 you get not one – but four – separate 17th magnitude views of the same quasar for the trouble of setting up one 20 inch truss tube dobsonian. Is it worth it? (Can you say “quadruple your observing pleasure”?)

But the phenomenon behind such a view is even more interesting to professional astronomers. What can we learn from such a unique effect?

The theory is already well established – Albert Einstein predicted it in his “General Theory of Relativity” of 1915. Einstein’s core idea was that an observer undergoing acceleration and one stationary in a gravitational field could not tell the difference between the two on their “weight”. By exploring this idea to its fullest, it became clear that not only matter but light (despite being massless) undergoes the same sort of confusion. Because of this, light approaching a gravitational field at an angle is “accelerated toward” the source of the gravity – but because the velocity of light is constant such acceleration only effects light’s path and wavelength – not its actual speed.

Gravitational lensing itself was first detected during the total solar eclipse of 1919. This was seen as a slight shift in the positions of stars near the Sun’s corona as captured on photographic plates. Because of this observation, we now know that you don’t need a lens to bend light – or even water to refract the image of those Koi swimming in the pond. Light like matter takes the path of least resistance and that means following the gravitational curve of space as well as the optical curve of a lens. The light from QSO2237+0305 is only doing what comes naturally by surfing the contours of “space-time” arcing around dense stars lying along the line of sight from a distant source through a more neighboring galaxy. The really interesting thing about Einstein’s Cross comes down to what it tells us about all the masses involved – those in the galaxy that refracts the light, and the Big One in the heart of the quasar that sources it.

In their paper “Reconstruction of the microlensing light curves of the Einstein Cross” Korean astrophysicist Dong-Wook Lee (et al) of Sejong University in association with Belgian astrophysicist J. Surdez (et al) of the University of Liege, found evidence of an accretion disk surrounding the black hole in Quasar QSO2237+0305. How is such a thing possible at the distances involved?

Lenses in general “collect and focus light” and those “gravitational lenses” (Lee at al posit a minimum of five low-mass but highly condensed bodies) within PGC 69457, do the same. In this way, light from a quasar that would normally travel well away from our instruments “wraps around” the galaxy to come toward us. Because of this we “see” 100,000 times more detail than otherwise possible. But there is a catch: Despite getting 100,000 times more resolution, we still only see light, not detail. And because there are several masses refracting light in the galaxy, we see more than one view of the quasar.

To get useful information from the quasar, you have to collect light over long periods of time (months to years) and use special analytical algorithms to pull the resulting data together. The method used by Lee and associates is called LOHCAM (LOcal Hae CAustic Modeling). (HAE itself is an acronym for High Amplification Events). Using LOHCAM and data available from OGLE (Optical Gravitational Lensing Experiment) and GLIPT (Gravitational Lens International Time Project), the team determined not only that LOHCAM works as hoped but that QSO2237+0305 may include a detectable accretion disk (from which it draws matter to power its light engine). The team has also determined the approximate mass of the quasars black hole, the size of the ultraviolet region radiating from it, and estimated the transverse motion of the black hole as it moves relative to the spiral galaxy.

The central black hole in Quasar QSO2237+0305 is thought to have a combined mass of 1.5 billion Suns – a value rivaling those of the largest central black holes ever discovered. Such a mass number represents 1 percent of the total number of stars in our own Milky Way galaxy. Meanwhile and by comparison, QSO2237+0305’s black hole is roughly 50 times more massive than that in the center of our own galaxy.

Based on “double-peaks” in luminosity from the quasar, Lee et al used LOHCAM to also determine the size of QSO2237+0305’s accretion disk, its orientation, and detected a central obscuration region around the black hole itself. The disk itself is roughly 1/3rd of a light year in diameter and is turned face on towards us.

Impressed? Well let’s also add that the team has determined the minimum number of microlenses and related masses found in the lensing galaxy. Depending on transverse velocity assumed (in LOHCAM modeling), the smallest range from that of a gas giant – such as the planet Jupiter – through that of our own Sun.

So how does this “hole” thing work?

The OGLE and GLIPT projects monitored changes in the intensity of visual light streaming to us from each of the four 17th magnitude views of the quasar. Since most quasars are unresolvable,due to their great distances in space, by telescope. Fluctuations in luminosity are seen only as a single point of data based on the brightness of the entire quasar. However, QSO2237+0305 presents four images of the quasar and each image highlights luminosity originating from a different perspective of the quasar. By telescopically monitoring all four images simultaneously, slight variations in image intensity can be detected and recorded in terms of magnitude, date, and time. Over several months to years, a considerable number of such “high amplification events” can occur. Patterns emerging out of their occurrence (from one 17th magnitude view to the next) can then be analyzed to show motion and intensity. Out of this a super high resolution view of normally unseen structure within the quasar is possible.

Could you and your friend with that 20 inch dob-newtonian do this?

Sure – but not without some very expensive equipment and a good handle on some complex mathematical imaging algorithms. A nice place to start however might simply be to ogle the galaxy and hang with the cross for awhile…

Written by Jeff Barbour

Posted on by Fraser Cain

Why Colonize the Moon First?

Artist's concept for a Lunar base. Credit: NASA

NASA has a new Vision for Space Exploration: in the decades ahead, humans will land on Mars and explore the red planet. Brief visits will lead to longer stays and, maybe one day, to colonies.

First, though, we’re returning to the Moon.

Why the Moon before Mars?

“The Moon is a natural first step,” explains Philip Metzger, a physicist at NASA Kennedy Space Center. “It’s nearby. We can practice living, working and doing science there before taking longer and riskier trips to Mars.”

The Moon and Mars have a lot in common. The Moon has only one-sixth Earth’s gravity; Mars has one-third. The Moon has no atmosphere; the Martian atmosphere is highly rarefied. The Moon can get very cold, as low as -240o C in shadows; Mars varies between -20o and -100o C.

Even more important, both planets are covered with silt-fine dust, called “regolith.” The Moon’s regolith was created by the ceaseless bombardment of micrometeorites, cosmic rays and particles of solar wind breaking down rocks for billions of years. Martian regolith resulted from the impacts of more massive meteorites and even asteroids, plus ages of daily erosion from water and wind. There are places on both worlds where the regolith is 10+ meters deep.

Operating mechanical equipment in the presence of so much dust is a formidable challenge. Just last month, Metzger co-chaired a meeting on the topic: “Granular Materials in Lunar and Martian Exploration,” held at the Kennedy Space Center. Participants grappled with issues ranging from basic transportation (“What kind of tires does a Mars buggy need?”) to mining (“How deep can you dig before the hole collapses?”) to dust storms–both natural and artificial (“How much dust will a landing rocket kick up?”).

Answering these questions on Earth isn’t easy. Moondust and Mars dust is so … alien.

Try this: Run your finger across the screen of your computer. You’ll get a little residue of dust clinging to your fingertip. It’s soft and fuzzy–that’s Earth dust.

Lunar dust is different: “It’s almost like fragments of glass or coral–odd shapes that are very sharp and interlocking,” says Metzger. (View an image of lunar dust.)

“Even after short moon walks, Apollo 17 astronauts found dust particles had jammed the shoulder joints of their spacesuits,” says Masami Nakagawa, associate professor in the mining engineering department of the Colorado School of Mines. “Moondust penetrated into seals, causing the spacesuits to leak some air pressure.”

In sunlit areas, adds Nakagawa, fine dust levitated above the Apollo astronauts’ knees and even above their heads, because individual particles were electrostatically charged by the Sun’s ultraviolet light. Such dust particles, when tracked into the astronauts’ habitat where they would become airborne, irritated their eyes and lungs. “It’s a potentially serious problem.”

Dust is also ubiquitous on Mars, although Mars dust is probably not as sharp as moondust. Weathering smooths the edges. Nevertheless, Martian duststorms whip these particles 50 m/s (100+ mph), scouring and wearing every exposed surface. As the rovers Spirit and Opportunity have revealed, Mars dust (like moondust) is probably electrically charged. It clings to solar panels, blocks sunlight and reduces the amount of power that can be generated for a surface mission.

For these reasons, NASA is funding Nakagawa’s Project Dust, a four-year study dedicated to finding ways of mitigating the effects of dust on robotic and human exploration, ranging from designs of air filters to thin-film coatings that repel dust from spacesuits and machinery.

The Moon is also a good testing ground for what mission planners call “in-situ resource utilization” (ISRU)–a.k.a. “living off the land.” Astronauts on Mars are going to want to mine certain raw materials locally: oxygen for breathing, water for drinking and rocket fuel (essentially hydrogen and oxygen) for the journey home. “We can try this on the Moon first,” says Metzger.

Both the Moon and Mars are thought to harbor water frozen in the ground. The evidence for this is indirect. NASA and ESA spacecraft have detected hydrogen–presumably the H in H2O–in Martian soil. Putative icy deposits range from the Martian poles almost to the equator. Lunar ice, on the other hand, is localized near the Moon’s north and south poles deep inside craters where the Sun never shines, according to similar data from Lunar Prospector and Clementine, two spacecraft that mapped the Moon in the mid-1990s.

If this ice could be excavated, thawed out and broken apart into hydrogen and oxygen … Voila! Instant supplies. NASA’s Lunar Reconnaissance Orbiter, due to launch in 2008, will use modern sensors to search for deposits and pinpoint possible mining sites.

“The lunar poles are a cold place, so we’ve been working with people who specialize in cold places to figure out how to land on the soils and dig into the permafrost to excavate water,” Metzger says. Prime among NASA’s partners are investigators from the Army Corps of Engineers’ Cold Regions Research and Engineering Laboratory (CRREL). Key challenges include ways of landing rockets or building habitats on ice-rich soils without having their heat melt the ground so it collapses under their weight.

Testing all this technology on the Moon, which is only 2 or 3 days away from Earth, is going to be much easier than testing it on Mars, six months away.

So … to Mars! But first, the Moon.

Original Source: Science@NASA Article

Posted on by Fraser Cain

India and Europe Agree on Lunar Mission

Image credit: ESA
On 17 March the ESA Council, at its meeting in Paris, unanimously approved a cooperation agreement between ESA and the Indian Space Research Organisation for India?s first moon mission ? Chandrayaan-1.

The Indian Space Research Organisation (ISRO), founded in 1969, launched its first satellite in 1975. Since then it has developed a number of launch vehicles as well as satellites for Earth observation, remote sensing, telecommunications and weather forecasting. India has its own launch site at Sriharikota but has also used Europe?s Spaceport in French Guiana to launch its satellites. Chandrayaan-1 marks its first venture into planetary space science.

Under the agreement Europe will coordinate and support the provision of three instruments: CIXS-2, the Chandrayaan-1 Imaging X-Ray Spectrometer; SARA, a Sub-keV Atom Relecting Analyzer; and SIR-2, a Near-Infrared Spectrometer. It will also support the hardware for the High-Energy X-ray Spectrometer (HEX). Direct ESA in-kind contributions are also foreseen under this historical agreement. In return, all data resulting from the instruments will be made immediately available to ESA Member States through ESA.

The instruments requested are identical to those on ESA?s SMART-1. Launched in 2003, SMART-1, having demonstrated a new solar electric propulsion motor and tested other technologies on its way to the moon, has just started its science phase. It will make the first comprehensive inventory of key chemical elements in the lunar surface.

ISRO plans to send a 1050 kg (523 kg initial orbit mass and 440 kg dry mass) remote sensing satellite to help unravel mysteries about the origin and evolution of the solar system in general and the Moon in particular. The satellite, which is expected to have an operational life of two years, will be launched by India?s Polar Satellite Launch Vehicle in 2007/2008.

ESA will give ISRO the benefit of its experience with SMART-1 and will further assist in operations facilitation as well as providing the science instruments.

ESA’s SMART-1 put Europe in the lead in the new race back to the Moon. As well as India and Japan, China and the USA also intend to launch lunar missions in the coming years. The cooperation with India will keep European scientists in the forefront.

The ESA Director of Science, David Southwood, said: “One should also see the cooperation in a wider context. Space science is a natural area for space agencies to learn to work together in technical matters. Such cooperation remains a strategic element in the Director General’s wider agenda for the Agency.”

Original Source: ESA News Release

Posted on by Fraser Cain

Cassini Sees Mimas Eclipse Janus

Saturn’s icy, impact-riddled moon Mimas slips briefly in front of Saturn’s moon Janus in this movie from Cassini. Mimas is 397 kilometers (247 miles) across, while Janus is 181 kilometers (113 miles) across.

The movie was created from 37 original images taken over the course of 20 minutes as the spacecraft’s narrow-angle camera remained pointed toward Janus. Although Mimas moves a greater distance across the field of view, Janus also moved perceptibly during this time. The images were aligned to keep Janus close to the center of the scene. Additional frames were inserted between the 37 Cassini images in order to smooth the appearance of Mimas’ movement — a scheme called interpolation. Close-up images from the few minutes surrounding the occultation are arranged into a strip along the bottom of the movie.

The terrain on Mimas seen here is about 80 degrees west of the terrain seen in a previously released movie (see Mimas on the Move), which showed the little moon appearing to cross Saturn’s ring plane from Cassini’s vantage point. In that previous movie, the rim of the large impact crater Herschel (130 kilometers, or 80 miles wide) was visible as a flattening of the moon’s eastern limb. In the new movie, Herschel is almost at dead center.

Contrast on Janus was mildly enhanced to aid the visibility of its surface. The right side of Mimas appears bright because the moon was partly overexposed in this image sequence.

The images for this movie were taken in visible light on March 5, 2005, when Cassini was approximately 1.8 million kilometers (1.1 million miles) from Mimas and 1.9 million kilometers (1.2 million miles) from Janus. The image scale is approximately 11 kilometers (7 miles) per pixel.

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

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

Original Source: NASA/JPL/SSI

Posted on by Fraser Cain

Ripples in Spacetime Could Explain Dark Energy

Why is the universe expanding at an accelerating rate, spreading its contents over ever greater dimensions of space? An original solution to this puzzle, certainly the most fascinating question in modern cosmology, was put forward by four theoretical physicists, Edward W. Kolb of the U.S. Department of Energy’s Fermi National Accelerator Laboratory, Chicago (USA): Sabino Matarrese of the University of Padova; Alessio Notari from the University of Montreal (Canada); and Antonio Riotto of INFN (Istituto Nazionale di Fisica Nucleare) of Padova (Italy). Their study was submitted yesterday to the journal Physical Review Letters.

Over the last hundred years, the expansion of the universe has been a subject of passionate discussion, engaging the most brilliant minds of the century. Like his contemporaries, Albert Einstein initially thought that the universe was static: that it neither expanded nor shrank. When his own Theory of General Relativity clearly showed that the universe should expand or contract, Einstein chose to introduce a new ingredient into his theory. His “cosmological constant” represented a mass density of empty space that drove the universe to expand at an ever-increasing rate.

When in 1929 Edwin Hubble proved that the universe is in fact expanding, Einstein repudiated his cosmological constant, calling it “the greatest blunder of my life.” Then, almost a century later, physicists resurrected the cosmological constant in a variant called dark energy. In 1998, observations of very distant supernovae demonstrated that the universe is expanding at an accelerating rate. This accelerating expansion seemed to be explicable only by the presence of a new component of the universe, a “dark energy,” representing some 70 percent of the total mass of the universe. Of the rest, about 25 percent appears to be in the form of another mysterious component, dark matter; while only about 5 percent comprises ordinary matter, those quarks, protons, neutrons and electrons that we and the galaxies are made of.

“The hypothesis of dark energy is extremely fascinating,” explains Padova’s Antonio Riotto, “but on the other hand it represents a serious problem. No theoretical model, not even the most modern, such as supersymmetry or string theory, is able to explain the presence of this mysterious dark energy in the amount that our observations require. If dark energy were the size that theories predict, the universe would have expanded with such a fantastic velocity that it would have prevented the existence of everything we know in our cosmos.”

The requisite amount of dark energy is so difficult to reconcile with the known laws of nature that physicists have proposed all manner of exotic explanations, including new forces, new dimensions of spacetime, and new ultralight elementary particles. However, the new report proposes no new ingredient for the universe, only a realization that the present acceleration of the universe is a consequence of the standard cosmological model for the early universe: inflation.

“Our solution to the paradox posed by the accelerating universe,” Riotto says, “relies on the so-called inflationary theory, born in 1981. According to this theory, within a tiny fraction of a second after the Big Bang, the universe experienced an incredibly rapid expansion. This explains why our universe seems to be very homogeneous. Recently, the Boomerang and WMAP experiments, which measured the small fluctuations in the background radiation originating with the Big Bang, confirmed inflationary theory.

It is widely believed that during the inflationary expansion early in the history of the universe, very tiny ripples in spacetime were generated, as predicted by Einstein’s theory of General Relativity. These ripples were stretched by the expansion of the universe and extend today far beyond our cosmic horizon, that is over a region much bigger than the observable universe, a distance of about 15 billion light years. In their current paper, the authors propose that it is the evolution of these cosmic ripples that increases the observed expansion of the universe and accounts for its acceleration.

“We realized that you simply need to add this new key ingredient, the ripples of spacetime generated during the epoch of inflation, to Einstein’s General Relativity to explain why the universe is accelerating today,” Riotto says. “It seems that the solution to the puzzle of acceleration involves the universe beyond our cosmic horizon. No mysterious dark energy is required.”

Fermilab’s Kolb called the authors’ proposal the most conservative explanation for the accelerating universe. “It requires only a proper accounting of the physical effects of the ripples beyond our cosmic horizon,” he said.

Data from upcoming experiments will allow cosmologists to test the proposal. “Whether Einstein was right when he first introduced the cosmological constant, or whether he was right when he later refuted the idea will soon be tested by a new round of precision cosmological observations,” Kolb said. “New data will soon allow us to distinguish between our explanation for the accelerated expansion of the universe and the dark energy solution.”

INFN (Istituto Nazionale di Fisica Nucleare), Italy’s national nuclear physics institute, supports, coordinates and carries out scientific research in subnuclear, nuclear and astroparticle physics and is involved in developing relevant technologies.

Fermilab, in Batavia, Illinois, USA, is operated by Universities Research Association, Inc. for the Department of Energy’s Office of Science, which funds advanced research in particle physics and cosmology.

Original Source: Istituto Nazionale di Fisica Nucleare

Posted on by Fraser Cain

Many Faces of Hyperion

As it loops around Saturn, Cassini periodically gets a good view of Saturn’s moon Hyperion. Hyperion chaotically tumbles around in its orbit and is perhaps the largest irregularly-shaped moon in the solar system. New details about this oddball worldlet will certainly come to light in September, 2005, when Cassini is slated to approach Hyperion at a distance of 990 kilometers (615 miles). Hyperion is 266 kilometers (165 miles) across.

The images were taken in visible light with the Cassini spacecraft narrow-angle camera in October 2004 and February 2005, at distances ranging from 1.3 to 1.6 million kilometers (808,000 to 994,000 million miles) from Hyperion and at Sun-Hyperion-spacecraft, or phase, angles ranging from 42 to 66 degrees. Resolution in the original images was 8 to 10 kilometers (5 to 6 miles) per pixel. The images have been contrast-enhanced and magnified by a factor of two to aid visibility.

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 team is based at the Space Science Institute, Boulder, Colo.

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

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Mars is Still Geologically Active

Shifting glaciers and exploding volcanoes aren?t confined to Mars? distant past, according two new reports in the journal Nature.

Glaciers moved from the poles to the tropics 350,000 to 4 million years ago, depositing massive amounts of ice at the base of mountains and volcanoes in the eastern Hellas region near the planet?s equator, based on a report by a team of scientists analyzing images from the Mars Express mission. Scientists also studied images of glacial remnants on the western side of Olympus Mons, the largest of the volcano calderas in the solar system. They found additional evidence of recent ice formation and movement on these tropical mountain glaciers, similar to ones on Mount Kilimanjaro in Africa.

In a second report, the international team reveals previously unknown traces of a major eruption of Hecates Tholus less than 350,000 million years ago. In a depression on the volcano, researchers found glacial deposits estimated to be 5 to 24 million years old.

James Head, professor of geological sciences at Brown University and an author on the Nature papers, said the glacial data suggests recent climate change in Mars? 4.6-billion-year history. The team also concludes that Mars is in an ?interglacial? period. As the planet tilts closer to the sun, ice deposited in lower latitudes will vaporize, changing the face of the Red Planet yet again.

Discovery of the explosive eruption of Hecates Tholus provides more evidence of recent Mars rumblings. In December, members of the same research team revealed that calderas on five major Mars volcanoes were repeatedly active as little as 2 million years ago. The volcanoes, scientists speculated, may even be active today.

?Mars is very dynamic,? said Head, lead author of one of the Nature reports. ?We see that the climate change and geological forces that drive evolution on Earth are happening there.?

Head is part of a 33-institution team analyzing images from Mars Express, launched in June 2003 by the European Space Agency. The High Resolution Stereo Camera, or HRSC, on board the orbiter is producing 3-D images of the planet?s surface.

These sharp, panoramic, full-color pictures provided fodder for a third Nature report. In it, the team offers evidence of a frozen body of water, about the size and depth of the North Sea, in southern Elysium.

A plethora of ice and active volcanoes could provide the water and heat needed to sustain basic life forms on Mars. Fresh data from Mars Express ? and the announcement that live bacteria were found in a 30,000-year-old chunk of Alaskan ice ? is fueling discussion about the possibility of past, even present, life on Mars. In a poll taken at a European Space Agency conference last month, 75 percent of scientists believe bacteria once existed on Mars and 25 percent believe it might still survive there.

Head recently traveled to Antarctica to study glaciers, including bacteria that can withstand the continent?s dry, cold conditions. The average temperature on Mars is estimated to be 67 degrees below freezing. Similar temperatures are clocked in Antarctica?s frigid interior.

?We?re now seeing geological characteristics on Mars that could be related to life,? Head said. ?But we?re a long way from knowing that life does indeed exist. The glacial deposits we studied would be accessible for sampling in future space missions. If we had ice to study, we would know a lot more about climate change on Mars and whether life is a possibility there.?

The European Space Agency, the German Aerospace Center and the Freie Universitaet in Berlin built and flew the HRSC and processed data from the camera. The National Aeronautics and Space Administration (NASA) supported Head?s work.

Original Source: Brown University

Posted on by Fraser Cain

Problem with Opportunity’s Mineral Finding Tool

Image credit: NASA/JPL
NASA has suspended use of one of the mineral-identifying tools on the Opportunity Mars rover while experts troubleshoot a problem with getting data from the instrument, the robot’s miniature thermal emission spectrometer.

“As always, our first priority is to protect the instrument, so we have turned it off while we plan diagnostic tests,” said Jim Erickson of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., project manager for the Mars Exploration Rover Project. “Opportunity’s other instruments are healthy and providing excellent science, and Spirit’s entire instrument suite is working well and being kept busy by the science team.”

Both Opportunity and Spirit, its twin, have been examining Mars since January 2004, more than four times as long as their successful three-month primary missions. While researchers work to diagnose the spectrometer-data problem and seek the best way to mend it or work around it, Opportunity is continuing its journey and observing a crater called “Vostok.” On the other side of the planet, meanwhile, martian winds have revealed themselves as dust devils in new images from Spirit and caused mixed effects on the rover itself, depositing dust on a camera and removing dust from solar panels.

On March 3 and 4, Opportunity transmitted data sets for 17 successful readings by its miniature thermal emission spectrometer but also reported that eight other attempted readings yielded incomplete data sets. This spectrometer, from high on the rover’s mast, observes rocks and other targets from afar. It measures the infrared radiation they emit in 167 different wavelengths, providing information about the targets’ composition. Two other types of spectrometers, mounted on the rover’s robotic arm, provide additional information about composition when the rover is close enough to touch the target.

Researchers are considering several possible root causes for the spectrometer-data problem. One possibility is malfunctioning of an optical switch that tells a mirror in the instrument when to begin moving. Another is that the mirror is not properly moving at a constant velocity. “If it is the optical switch, we could use a redundant one built into the instrument,” said Dr. Phil Christensen of Arizona State University, Tempe, lead scientist for the miniature thermal emission spectrometers on both rovers. He added that, if the root cause cannot be remedied, scientists could still get useful data from the instrument in its currently impaired condition.

Even a total loss of the miniature thermal emission spectrometer would not end the rover’s usefulness. In fact, NASA took a calculated risk by disabling this instrument on Opportunity 10 months ago, though the current problem appears unrelated to potential damage anticipated then. At that time, rover operators began using a “deep sleep” technique to conserve energy on Opportunity during reduced-sunshine months of Mars’ winter. Turning off power to overnight heaters let the instrument get cold enough to possibly damage its beam-splitter. However, the spectrometer kept working through the coldest months. Christensen said, “What we’re seeing now does not appear to be any problem with the beam-splitter.”

The rover team is not restricting use of Spirit’s miniature thermal emission spectrometer while troubleshooting the problem on Opportunity.

Spirit’s work capabilities grew with a sudden jump in output from solar panels on March 9, which caused the daily power supply to double. In a possibly related development three days earlier, some dust appeared to have blown onto lenses of Spirit’s front hazard-avoidance camera, enough for slight mottling in images from both the left and right eyes of the stereo camera, but not enough to affect the usefulness of the camera. Mottling in left-eye images cleared markedly the same day the power increased. Team members speculated that Spirit’s power boost, like similar ones on Opportunity in October, resulted from wind removing some accumulated dust from solar panels. Spirit captured pictures of dust-lofting whirlwinds on March 10, adding evidence for windy local conditions. Images the next day showed solar panels cleaned of most of their dust buildup.

Opportunity’s rear hazard-avoidance camera picked up some dust contamination three months ago. The dust on it has not affected operations and has neither decreased nor increased perceptibly since first noticed. No dust has contaminated lenses of the navigation cameras or panoramic cameras on either rover. From all cameras combined, the rovers have returned more than 72,000 images. Images and other geological data from Spirit and Opportunity are successfully providing unprecedented evidence about wet environmental conditions in Mars’ past.

JPL, a division of the California Institute of Technology in Pasadena, has managed NASA’s Mars Exploration Rover project since it began in 2000. Images and additional information about the rovers and their discoveries are available on the Internet at http://www.nasa.gov/vision/universe/solarsystem/mer_main.html and http://marsrovers.jpl.nasa.gov.

Original Source: NASA/JPL News Release