The new race for space
Today, Britain's astronomers table plans for future missions, each vying for £450m from the European Space Agency. So will the quest for Earth's sister planet win? Or will it be the voyage to Jupiter's icy moon? Helen Brown profiles the top contenders
Wednesday 26 July 2006
PROJECT NAME: DARWIN
Lead institution: The Open University
Aim: To find out if Earth-like planets orbiting nearby stars are capable of sustaining life
Ready for launch: 2015-2020
We don't need to get especially close to other planets to find out if there may be life out there - it may soon be possible to spy on their atmospheres from afar. The Darwin project is a mission to analyse the reflected light from rocky, Earth-sized planets orbiting stars at roughly the same distance we are from the Sun. It has been under development by the European Space Agency since the late 1990s, and the team has an ambitious target list of 500 parent stars to search around. "The problem," says Professor Glenn White, "is that planets may be 10,000 million times fainter than direct light from the parent star - imagine standing 10ft in front of a car with its headlights on full beam in your face and trying to make out a feeble penlight being held beside the headlight. The challenge is to design a mission that enables us to study very faint things beside bright ones."
The proposed solution is to use four spacecraft flying in extremely close formation at 1.5million km from the Earth - the second "lagrangian point ", where the gravitational pull of the Sun, Earth and Moon cancel each other out. Each of these "interplanetary Red Arrows" will be equipped with a telescope 3.5m in diameter. White's team has developed a technique called "nulling interferometry" which combines the light from two telescopes (10-100m apart) pointed at the host star, cancelling it out and causing it to "wink", making the faint reflected light from the planet visible.
A spectrometer will then split the light reflected from the planet into wavelengths, allowing the team to search for signs of gases in the atmosphere (such as carbon dioxide, carbon monoxide and ozone) which are associated with life processes on Earth. "If we see a gas associated with bacteria, like methane," says White, "then there's a fair chance that there's some kind of biogenic process occurring. The detection of life on another planet will have profound sociological, scientific and religious implications for mankind."
Lead institution: University of Leicester
Aim: To study black holes
Ready for launch: 2017-2020
Xeus is spelt with an X because it hopes to become the ultimate X-ray observatory. Professor Bob Warwick's team of X-ray astronomers study the rays emitted from celestial objects. Celestial X-rays (first discovered in 1962) are thought to be emitted from high-energy sources which contain exceptionally hot gases at temperatures from a million to one hundred million degrees Celsius, such as neutron stars and black holes. Since X-ray radiation is absorbed by the Earth's atmosphere, instruments designed to observe them must be taken to a high altitude or - preferably - into space itself.
There are currently four satellite observatories studying the X-ray emissions from celestial bodies - the key missions being the European Space Agency's XMM-Newton and Nasa's Chandra - but Xeus will be 200 times more powerful than its predecessors. "Xeus is a bid to put 'the next generation' of X-ray observatory into space," says Warwick, who is particularly interested in black holes. "As matter is attracted to black holes - which are a source of intense gravity but not much else - it gains lots of energy and heat. So X-rays are the best way to study what happens to matter as is goes over the event horizon and down the plug - or 'gravitational well' as we call it. Black holes remind us that the Universe doesn't take any prisoners. They remind us that our own planet is a relatively serene place compared to such tempestuous regions."
Lead institution: Imperial College, London Aim: To discover if Jupiter's moon Europa is a potential habitat for life
Ready for launch: 2017
Discovered in 1610 by Galileo, Europa is the fourth largest of Jupiter's many moons. It has an outer layer of water thought to be 100km thick, under a crust of ice. Recent data from Nasa's Galileo orbiter certainly suggests the presence of a salty liquid-water ocean beneath the ice. This ocean may contain life subsisting in an environment similar to that of Earth's deep-ocean hydrothermal vents. That's why Galileo was smashed into Jupiter in 2003 - to prevent the unsterilised craft from drifting into, and contaminating, potential life on the moon in the future. Professor Michele Dougherty explains that her team "wants to get the best understanding possible of how thick that icy surface is because in the longer term we want to send a probe below the surface, and we'll need to pick the thinnest part of the surface to penetrate".
PROJECT: DUNE (DARK UNIVERSE EXPLORER)
Lead institution: University of Edinburgh
Aim: To measure the properties of "dark energy"
Ready for launch: 2015
"Dune is a satellite designed to take pictures of the whole sky," says Dr John Peacock. "If you're reaching to the limits you can discover all sorts of things. If you've seen the images from the Hubble telescope you'll know how wonderful they can be, but Hubble just covers a tiny area."
In particular, Peacock's team wants to "decipher the nature of dark energy" which, although it is invisible, can be spotted by the gravitational effects it causes. Only 5 per cent of our universe is composed of visible matter, with "dark matter" making up 25 per cent and the remaining 70 per cent being "dark energy".
"Dark matter clumps together," he says, "and it's probably some elementary particle that's left over from when the Universe was young, and hot and dense. It hasn't turned up in a particle accelerator yet, but it will do at some point. The mystery is the dark energy. Its gravitational properties are peculiar - it's making the expansion of the Universe speed up, pulling the Universe apart, whereas dark matter (with its clumping properties) pulls it together and slows expansion down. By getting huge quantities of astronomical data and taking pictures of most of the galaxies in the Universe, we should be able to work out how the nature of dark energy has changed over time."
The team will also revisit specific patches of sky, hunting for supernovae. "But you never know what we will find," says Peacock, "if you look at the history of surveying the sky, scientists have most often ended up discovering something completely different to the phenomenon they set out to study. But you can't stand up in front of a funding agency and ask for €300m and say 'you never know, something might happen!'"
PROJECT: LUNAR MISSION (WITH AIRLESS MICRO-PENETRATORS)
Lead institution: University College London
Aim: To penetrate the moon's surface and discover more about the lunar core
Ready for launch: 2015
If you believe they put a man on the moon, then surely a 2-5kg drilling machine can't be too difficult to put up there. But such machines - called micro-penetrators or "penetrometers" - which are shot from an orbiter, have never been used before on the moon. As Dr Rob Gowen explains: "No penetrator has yet been deployed on an airless body. Only the Nasa Mars Polar Orbiter/DS2 has deployed penetrators, and neither DS2 nor the main lander were ever heard of again. The only other penetrators mission was the Russian Mars '96 which failed during the launch phase."
Such penetrators are an alternative to planetary soft-landers, which can deliver more elaborate payloads, but face significant restrictions on landing sites and are extremely expensive. Several penetrators can be launched for the price of a soft-landing, allowing for some to fail.
Gowen is ultimately interested in getting the penetrators to Europa and searching for life. But sending them to the Moon is the first step. The team are interested in discovering whether the Moon has a lunar core, and if so, what size it is. "This discovery would have profound impacts on our understanding of the Moon's residual magnetism and, in turn, the origin of the Moon and evolution of planetary magnetic fields," says Gowen. They also want to study the origin and location of the so-called "shallow moonquakes" which may result from tectonic processes occurring 20-30km beneath the moon's surface.
"Going to the moon used to be about rocks," says Gowen, "but now it's more about water, which with its presence, situation, and origin is a thread in the search for life. The most challenging aspect will be survival of the scientific instruments. In terms of technology this is exciting from the point of view of industrial spin-off because we are trying to develop some very light, advanced and tiny instruments. At the moment we're working with extremely sensitive micro-seismometers, trying to make them tougher."
The stars in August
In January 1610, when Galileo turned his astronomical telescope to the Milky Way, he was astonished. "I have observed the nature and material of the Milky Way... with the aid of a telescope, all the disputes that have vexed philosophers have been resolved, and we are at last free from wordy debates about it ... the Galaxy is in fact nothing but a congeries of innumerable stars grouped together in clusters."
Galileo's description was spot-on. The Milky Way is roughly circular, yet thin and flat, a pizza-shaped assemblage of 200,000 million stars, and - as a result of perspective - the more distant stars appear to congregate into a band. In August, that band arches overhead, and it's a glorious sight. The stars appear more densely packed in the constellations of Scorpius and Sagittarius, where you are looking towards the egg-shaped centre of the Galaxy.
Like the Sun, our Milky Way's gravity holds on to a family - in this case, several baby galaxies. The two biggest are the Large and Small Magellanic Clouds, which lie about 170,000 light years away. If you're in the southern hemisphere, you'll spot them in the skies looking like detached portions of the Milky Way.
Now more tiny galaxies have been found. In Apache Point, New Mexico, an automated telescope works around the clock to survey the sky. The Sloan Digital Sky Survey has turned up many firsts - including two new companions to our Milky Way. The research on these galaxies has been conducted by Cambridge scientists Daniel Zucker, Vasily Belokurov and Wyn Evans.
Zucker explains: "I was poring over a field of stars and noticed an overdensity in Canes Venatici. Looking further, it proved to be a previously unknown dwarf galaxy. It's about 640,000 light years from the Sun. This makes it one of the Milky Way's most remote companion galaxies."
Hours later, Zucker's colleague Belokurov e-mailed excitedly with his finding of another dwarf galaxy - this time, located in the background of the stars in the constellation of Bootes. Belokurov couldn't resist nicknaming it "Boo"! Boo is very distorted - a result of being pulled apart by our Galaxy's gravitational tides.
The brilliant planet Jupiter has dominated our summer skies, but it's now slipping away to the south-west. Above Jupiter you'll find orange Arcturus, and to the planet's left the red giant star Antares, which marks the heart of Scorpius (the scorpion).
High in the south lies the large Summer Triangle, composed of three brilliant stars in separate constellations. The jewel is pure-white Vega, the brightest star in the compact star-group of Lyra. To its left, Deneb marks the tail of the swan, Cygnus, which flies below Vega.
The third member of the great triangle is Altair, in another celestial bird, Aquila (the eagle). Two fainter stars, flanking Altair above and below, make this star recognisable.
If you're up before dawn, there's more planetary activity at hand. Venus is a brilliant Morning Star, rising around 4am. Below it you may spot elusive Mercury, which draws closest to Venus on the morning of 11 August. Saturn is gradually creeping upwards in the dawn sky, and passes very close to Venus on 27 August.
Heather Couper and Nigel Henbest
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