2.4 A&G • April 2012 • Vol. 53

Planets everywhere

Sue Bowler, Editor

It is very hard to believe, in the current exciting climate of planetary research,

that just 20 years ago the only extrasolar planets known were orbiting a pulsar. No planets had been found orbiting any other star remotely like our Sun and observing-projects to find them were not looking likely to find any. Compare that with the current situation, with hundreds of planets discovered – some in multiple planet systems – and every indication that planets are as much a part of the normal evolution of matter as stars and galaxies. There may even be more planets in the galaxy than there are stars.

The numbers matter. While there seem to be many barriers to the evolution of life in any individual setting, the sheer numbers of places in the universe where we can now think of it happening makes a difference. This does not change the odds of contacting alien beings; the vast distances between stars and the times needed to send any sort of communication between them mean that we are unlikely to be able to meet the neighbours for a chat. But their existence now feels a bit more likely, given that we think there are so many many more potential homes.

The transformation of what was, in 1992, a bit of a fringe field, into a hugely significant multi-disciplinary research area holds a lesson. Nobody knows which arcane idea will one day come to something. Unforeseen results move science forward, but most wild ideas remain precisely that. History suggests it is difficult to choose. The challenge within squeezed science funding is to avoid funding only projects with predictable outcomes. Perhaps we have to accept a few flights of fancy in order to get genuine scientific progress.

Editorial

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NASA puts JWST back on track, but ExoMars collaboration looks unlikelyNASA’s funding plans put the James Webb Space Telescope firmly on track for a launch in 2018, to widespread relief, but the essentially flat funding settlement for 2013 overall means something has to go. Planetary science seems hardest hit, with the especial blow for European planetary scientists of NASA pulling out of ExoMars, the ESA-led mission to look for signs of life on Mars. The American Astronomical Society welcomed the support for science embedded in President Obama’s proposed 2013 budget, but point out that the 20% cut in funding for planetary science threatens to under-mine the recommendations of the recent National Academy of Sciences Decadal Surveys. “We are grateful that the funding for the James Webb Space Telescope puts it on track for a launch in 2018,” says AAS Presi-dent Debra M Elmegreen, “and we hope we can achieve a balance of large, medium and small projects in solar physics, planetary science, and

astronomy and astrophysics so that US leadership in these fields can be sustained.”

The AAS also welcomed develop-ment support for the Large Synop-tic Survey Telescope, the Advanced Technology Solar Telescope (ATST), and the Atacama Large Millimeter Array, now entering science opera-tions. These are top-ranked projects in the 2001 and 2010 astronomy and

astrophysics decadal surveys.But NASA is now expected to

stop funding joint Mars exploration with ESA, raising big problems for ExoMars, the European-led mission to search for signs of life on Mars expected to launch in 2016. ExoMars had been planned with NASA pro-viding not only the launch vehicle, but also key instruments, communi-cations systems for the orbiter as well as a decent system to get the rover to the martian surface. ESA has already started to investigate whether Ros-cosmos, the Russian Space Agency, would be able to take on some or all of these responsibilities in the event of NASA pulling out completely.

Roscosmos is not in a position to supply all of the features NASA had proposed, however, so plans for ExoMars will need to change. Design changes at this stage will probably result in a less ambitious mission, at greater cost, possibly even pushing ExoMars over the €1bn cap agreed among ESA’s contributing nations. http://exploration.esa.int

The ExoMars mission is now in doubt, following NASA cuts. (ESA)

Marsquakes happening yesterday, geologicallyImages from the High Resolution Imaging Science Experiment have shown boulders displaced by seis-mic activity on Mars in the past few million years, and possibly much more recently than that. HiRISE images show the tracks of boulders ranging in size from 2 to 20 m across that have bounced and rolled down cliffs of lava that is just a few million years old. Gerald Rob-erts of Birkbeck College, University of London, led the team which com-pared the distribution of dislodged boulders around the martian fault system known as Cerberus Fossae with rocks displaced on Earth in a

2009 earthquake in central Italy. The size and number of boulders decreased radially. “This is consist-ent with the hypothesis that boulders had been mobilized by ground-shaking, and that the severity of the ground-shaking decreased away from the epicentres of marsquakes,” Roberts says. In the 2009 earth-quake, the boulder falls occurred up to approximately 50 km from the epicentre; on Mars, they were found 100 km away, suggesting that the quakes had a magnitude of over 7.

The quakes may have been very recent, given that the boulder tracks have not yet been destroyed by dust

or wind. The tracks of martian rov-ers can be erased by the wind within a few years, although tracks in shel-tered spots survive longer. Roberts and his team concluded that Mars may still be seismically active. And that would be especially significant in the search for life, because this mars quake took place near Elysium Mons volcano. If there is also recent or current active volcanism, then there is likely to be liquid water and the possibility of life on Mars.

Roberts et al. published their find-ings in JGR-Planets, a publication of the American Geophysical Union.http://tinyurl.com/Marsquake

UFOs from black holes control shape of galaxiesThe bigger the supermassive black hole at the centre of a galaxy, the faster the stars in the galactic bulge rotate. Why this should be so has been something of a puzzle, but now a mechanism that is both powerful and common enough to do the job has been identified. Supermassive black holes strongly influence regions several times the size of our solar system. But the galactic bulge is roughly a million times bigger. Now an international team led by Francesco Tombesi at NASA’s Goddard Space Flight Center has identified a new type of

outflow, a UFO (Ultra Fast Outflow), which may explain the link.

Tombesi and his team targeted 42 nearby active galaxies using the European Space Agency’s XMM-Newton satellite to home in on the location and properties of the UFOs.In 40% of them, they found outflows based on the blueshifted X-ray spec-tral lines of iron fluorescence gas close to the centres of these galaxies. The gas is moving outwards at typi-cally 14% of the speed of light and around one solar mass of gas per year is ejected in each galaxy. “Although slower than particle jets, UFOs are

much faster than other types of galactic outflows, which makes them much more powerful,” Tombesi says. “They have the potential to play a major role in transmitting feedback effects from a black hole into the gal-axy at large.” By removing mass that would otherwise fall into the black hole, ultra-fast outflows may slow its growth. At the same time, UFOs may strip gas from star-forming regions in the bulge, slowing or even shutting down star formation. Tombesi et al. published their results in Monthly Notices of the RAS.http://tinyurl.com/UFO-bhole

A&G • April 2012 • Vol. 53 2.5

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Galaxy collisions show new dark matter behaviour

The core of merging galaxy cluster Abell 520 formed from a violent collision of massive galaxy clusters. False-colour maps show the concentration of starlight (orange), hot gas (green) and dark matter. The blue areas pinpoint the location of most of the mass, which is dominated by dark matter. The blue and green in the centre reveals that a clump of dark matter resides near most of the hot gas, where very few galaxies are found. This confirms previous observations of a dark-matter core in the cluster and could challenge basic theories of dark matter, which predict that galaxies should be anchored to dark matter, even during the shock of a collision. (NASA, ESA, CFHT, CXO, M J Jee [Univ. of California, Davis], and A Mahdavi [San Francisco State Univ.])

The Bullet Cluster is the type example of the behaviour of dark matter in a fast galaxy collision: the dark matter haloes of colliding galaxies do not interact but continue on their way, taking the visible galaxies with them, while the hot gases from each galaxy interact. Now data from a galactic merger in Abell 520 suggest that dark matter does not always behave in this way. James Jee, of the University of California in Davis, and his team started from the unexpected

distribution of gas and dark matter in Abell 520 detected with the Hubble Space Telescope in 2007. These data were considered poor quality and it was not until better quality HST data coupled with observations using NASA’s Chandra X-ray Observatory confirmed the gas distribution that the unusual pattern emerged clearly. Jee and his team then used the Canada–France–Hawaii Telescope and Subaru Telescope to infer the location of dark matter by gravitational lensing, and went

back to the HST to the Wide Field Planetary Camera 2 to produce a more detailed map of the dark matter distribution.

This technique revealed that the dark matter in Abell 520 had collected into a “dark core,” containing far fewer galaxies than would be expected if the dark matter and galaxies were anchored together. Most of the galaxies have apparently sailed through the collision and moved far away.

It is not clear why this galactic collision is so different from others,

notably the Bullet Cluster. Both are thought to be relatively recent encounters, but the team proposes that perhaps Abell 520 was a more complex collision, or that there are faint galaxies in the central region that are not bright enough to be visible. A third possibility is that dark matter, rather than not interacting with itself, can be “sticky” in some way, and some of it has clumped together. Jee et al. published the results in The Astrophysical Journal. http://hubblesite.org/news/2012/10

Nomad planets in Milky Way may outnumber stars and carry lifeGravitational microlensing data suggest our galaxy may be awash with nomad planets, wander-ing in space far from host stars. Researchers at the Kavli Institute for Particle Astrophysics and Cos-mology estimate there may be up to 100 000 such planets in the Milky Way alone – and they may hold life. The team from KIPAC considered the gravitational pull of the Milky Way galaxy, the amount of matter available to make such objects, and how that matter might accumulate

into objects ranging from the size of Pluto to larger than Jupiter. Although there are large uncertainties in the extrapolation – planet formation is not well understood, for example – the team, led by Louis Stringari, is confident that more nomad planets exist than the dozen discovered by gravitational microlensing so far.

Stringari and his colleagues esti-mate that there may be 100 000 over-all. Some were probably ejected from solar systems, but not all of them could have formed in that fashion.

And Stringari and his team think that life is possible on these wan-derers. “If any of these nomad planets are big enough to have a thick atmosphere, they could have trapped enough heat for bacterial life to exist,” says Stringari. Although nomad planets don’t get heat from a star, they may generate heat through internal radioactive decay.

Planets of this size around other stars are generally detected from their effects on the light of that star; nomad planets present more of a

challenge. A reliable count, espe-cially of the smaller objects, will have to wait for the 2020s and the next generation of big survey telescopes, especially the space-based Wide-Field Infrared Survey Telescope and the ground-based Large Synoptic Survey Telescope. Intriguingly, if nomad planets do exist in these numbers, and if they also harbour life, then they may be a mechnism for spreading life across the galaxy.

Stringari et al. submitted their work to Monthly Notices of the RAS.

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2.6 A&G • April 2012 • Vol. 53

Lemaître honouredFamous Belgian astronomer Georges Lemaître has joined the list of notable scientists remembered by the names of ESA’s Automated Transfer Vehicles. ATVs are part of Europe’s contribution to the International Space Station; they deliver supplies to the ISS and, after six months or so, remove waste by burning up with it in the Earth’s atmosphere. The first ATV was named after Jules Verne, the second after Johannes Kepler, and the third, Edoardo Amaldi, is due to head for the ISS in March. ATV-4, Albert Einstein, is expected to take off early in 2013. http://www.esa.int

Sun gets activeA series of major solar flares hit Earth in February and March, triggering geomagentic storms and providing vivid auroral displays at moderate latitudes. Two flares on 6 March produced coronal mass ejections that passed several spacecraft (MESSENGEr, Spitzer and STErEO-B) and continued past Earth and Mars. Both flares came from the same active region on the Sun and the first one, at X5.4, was the second largest of the current solar cycle after the 9 August 2011 X6.9 flare. The flare triggered a temporary radio blackout on the sunward side of Earth that interfered with radio navigation and shortwave radio.http://1.usa.gov/A5yqz6

Earthquakes on IslaySince the start of February this year, the small Scottish isle of Islay has experienced a series of at least nine small earthquakes. The quakes are small, magnitudes around 2–2.8 ML, and have the form of an earthquake swarm comprising several quakes of similar magnitude, rather that the pattern of a large main shock and significantly smaller aftershocks associated with major quakes. residents reported buildings shaking, as if a large tracked vehicle was passing by. However, the quakes are relatively small and unlikely to cause structural damage. Such earthquake swarms are fairly common in Britain and several have been recorded in Scotland in past decades. http://bit.ly/wPEF89

NEws iN BriEf Herschel family papers available onlineA collection of archive materials from the family of Sir John F W Herschel (1792–1871) is now avail-able for study at Harry Ransom Center at the University of Texas at Austin. The collection includes much of John Herschel’s corre-spondence as well as examples of his cyanotypes.The papers include “significant mat-erial relating to William Herschel, the discovery of the planet Uranus, and his sister Caroline, who is now regarded as a pioneering female sci-entist”, says Richard Oram, associ-ate director and Hobby Foundation Librarian at the Ransom Center.

But it is John Herschel’s papers and letters that give this collection such significance as an insight into the Victorian scientific world. John has been called Britain’s first mod-ern physical scientist. Among other achievements, he was a pioneer of photography. In 1842 he invented the cyanotype, an image in shades of blue produced using light-sensitive iron salts. The cyanotype is one of Herschel’s most influential contribu-tions to photography and is also the origin of architects’ blueprints.

The Ransom Center was able to catalogue this important holding and create their online inventory thanks to a grant of $10 000 from the Friends of the Center for History of Physics at the American Institute of Physics.http://tinyurl.com/jherschel Halley’s Comet sketch by Caroline Herschel. (Harry Ransom Center)

VLT detects convincing signs of life – on EarthEuropean Southern Observatory data from the Very Large Tele-scope have enabled astronomers to say with confidence that they can detect signs of life on Earth using spectropolarimetry of earthshine: light from the Earth’s atmosphere reflected from the Moon. This is an important step towards detecting life on exoplanets.Light from exoplanets can be almost overwhelmed by the light of their parent star, but reflection polarizes the light, making it distinguish-able and highlighting atmospheric signatures of life in the planet’s atmo sphere, notably the chemical signature of photosynthesis.

On Earth, the biosphere produces oxygen, ozone, methane and carbon dioxide. While these can all occur naturally in a planet’s atmosphere without the presence of life, their simultaneous presence in large quantities are compatible only with the presence of life. If life were sud-denly to disappear and no longer continuously replenish these gases

they would react and recombine. The characteristic biosignature would disappear with them.

Michael Sterzik of ESO, Stefano Bagnulo of Armagh Observatory and Enric Palle of the Instituto de Astro-fisica de Canarias studied both the colour and the degree of polarization of light from the Earth after reflec-tion from the Moon, as if the light was coming from an exoplanet.

They could tell that Earth’s atmo-sphere is partly cloudy, that part of its surface is covered by oceans and – crucially – that there is veg-etation present. They could even detect changes in the cloud cover and amount of vegetation at different times as different parts of the Earth reflected light towards the Moon.

The team hopes that similar tech-niques will be able to identify exo-planets on which photosynthetic plant life like that on Earth has developed.

Sterzik et al. published their results in Nature.http://www.nature.com

The thin crescent Moon setting over ESO’s Paranal Observatory in Chile. The rest of the disc of the Moon can be faintly seen too. This is earthshine, sunlight reflecting off the Earth and illuminating the lunar surface. (ESO/B Tafreshi/TWAN [twanight.org])

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A&G • April 2012 • Vol. 53 2.7

News • Views

Space for space in Science MuseumFrom Alison BoyleHad David Hughes visited the Science Museum before writing his article on a “National Astronomy Museum” (A&G 53 1.32), he would have been pleased to find that there are many examples of recent British astronomy and space science in the UK’s national science and industry collections.

These include: parts of the Cam-bridge Interplanetary Scintillation Array used by Jocelyn Bell Burnell and Anthony Hewish in the discov-ery of the first pulsar; the JET-X X-ray telescope built by the Uni-versity of Leicester; the UK Dark Matter Collaboration’s DRIFT-1 detector, which the University of Sheffield brought up from Boulby Mine at the Museum’s request; a full-scale model of the Beagle 2 lander from the Open University; and the engineering model for the Huygens Surface Science Package accelerometer, the first man-made object to touch the surface of Titan (also from the OU). Like most large museums, we can display only a small part of our collections, and are improving access to those in storage (the full list is at http://col-lections online.nmsi.ac.uk).

As part of our collecting pro-gramme, we aim to preserve not only hardware, but also heritage that is at even greater risk of disap-pearing: the personal testimony of recent generations of scientists and engineers. On 26–27 April, the Museum will celebrate the 50th anniversary of Ariel-1, and look forward to future UK space activ-ity, with a conference attended by many of the UK’s leading space sci-entists from the past five decades.

Our collecting work is made possible, as it has been for over a century, by the enthusiasm of

friends and colleagues in universi-ties and industry around the UK. Prof. Hughes correctly notes that preserving recent heritage can be a difficult ask for university staff with limited time and storage space, and museum curators are always willing to offer assistance. When the University of Birmingham could no longer store the large Spacelab 2 X-Ray Telescope flown on the space shuttle, the Science Museum was delighted to acquire it.

Of course, it is not feasible for every artefact to find its way into a museum collection – not least given the huge size of some cur-rent technologies – but curators can also advise people on listing and preserving items themselves should they have the resources: for example, the Whipple Museum has an ongoing project to assist the University of Cambridge’s scientific departments in identifying important 20th-century heritage. However, as any museum curator will tell you, managing collections

is not an easy task: contrary to Prof. Hughes’s suggestion, drawing up a national list of artefacts with accompanying photographs is nei-ther easy nor inexpensive, if it is to be created and maintained in such a way that it will still be usable and meaningful in 100 years’ time. Setting up an entirely new museum, either a Jodrell Bank Museum of Radio Astronomy or a new UK National Astronomy Museum, would be a hugely daunting task, and arguably less helpful in the current situation than supporting existing museums who already have the expertise and will to col-lect recent astronomy and space sci-ence. These include many regional and university museums as well as major national collections such as those of the Science Museum and Royal Observatory, Greenwich.

What we find on display and in storage in our science museums today is there by the judgement of generations of curators and scientists. But a bit of luck never

goes astray, and museum curators cannot preserve an item if they are unaware of its existence. I would urge any readers of A&G who may have items of historical interest to contact their nearest museum.Alison Boyle, Curator, Astronomy & Modern Physics, The Science Museum, London, UK; alison.boyle@sciencemuseum.org.uk

No votes for calendar reformFrom Michael FeastIn connection with the news item on calendar reform (A&G 53 1.4), it is interesting to note that this is a matter with which the IAU initially concerned itself but later dropped.

At the first IAU general assem-bly in Rome (1922) the report of Commission 32 (Commission de la reforme du calendrier) was pre-sented and discussed (Trans. IAU 1 ed. A Fowler). The commission had been formed when the Union was established in 1919 and included a cardinal as one of its two presi-dents. The commission presented provisional plans for a universal calendar to the General Assembly and it was agreed to continue discussions by correspondence. The commission was then discontinued. At the assembly the astronomer H N Russell (not a member of Commission 32) “opposed the sanction of the Union being given to any project which altered the succession of the days of the week”.

I was told (I have forgotten by whom) that when, in the years between WWI and II, the Astrono-mer Royal tried to interest the Prime Minister in calendar reform, Stanley Baldwin replied “Don’t you want me to get any votes?”, which nicely illustrates the problem. Michael Feast, Astronomy, University of Cape Town and South African Astronomical Observatory.

Views

Big science at the Science Museum: the Spacelab X-Ray Telescope flew on the space shuttle.

Cluster conundrum clarifiedIn 2003 the four Cluster mission spacecraft flew through an elec-tron diffusion region in Earth’s magnetosheath and found it was 300 times bigger than expected, posing a challenge to theorists. Now modelling of electron accel-eration during reconnection sug-gests what happens and why. Electron diffusion regions lie at the heart of reconnection, the recon-figuration of magnetic field lines accompanied by explosive release

of magnetic energy in solar flares and the formation of aurora. Cluster explored changes in the Earth’s mag-netic field, and famously flew through a reconnection event on 1 October 2001. The data showed a very much larger region in which electrons could be energized than had been predicted from theory. The problem is that it should be impossible to sustain an electric field along the direction of the magnetic field lines, because the plasma in the magnetotail should be

a near-perfect conductor. New modelling of reconnection in

the magnetotail suggests not only that it is possible, but also that the region of space over which the elec-trons are energized during reconnec-tion is a thousand times bigger than previously thought. The volume of space involved also means that this process can account for the number of high-speed electrons formed dur-ing these events.

Jan Egedal of MIT and the Plasma Science and Fusion Center, working with MIT graduate student Ari Le and with William Daughton of the

Los Alamos National Laboratory, used the Kraken supercomputer at the National Institute for Computational Science at Oak Ridge National Labo-ratory in Tennessee. They note that this mechanism, while developed for Earth’s magnetotail, may also apply in the larger-scale situations such as coronal mass ejections. Modelling the effect of reconnection in these set-tings is important because it is high-speed electrons such as found here that permanently damage satellite systems. Egedal et al. report on their work in the journal Nature Physics.http://web.mit.edu/press