Astronomers get some new toys to play with

Few scientists believe that the space shuttle has helped their profession. Mostly, it has been used to convey astronauts to a space station that has produced little worthwhile research and to launch satellites that might have been put into orbit more cheaply by old-fashioned, throwaway rockets. But it has done one thing to assist astronomers. It has allowed what is probably their most famous instrument to be repaired and upgraded. That instrument is the Hubble space telescope, which took the picture of the Carina nebula shown above, and has snapped more than half a million other images over the years. Now, as the shuttle program draws to its close (the final launch will take place next year), Hubble is to be given its last makeover by the crew of Atlantis. On top of that, if the week has gone well, two other satellites intended to probe the universe’s earliest days will have been launched.

The mission to Hubble, which began on May 11th and is planned to last 11 days, will install a wide-field camera that will let the telescope see galaxies previously beyond its reach. Using this, the eager coteries of astronomers who have access to the instrument will be able to observe young, hot stars that glow mainly in the ultraviolet part of the spectrum. They will also be able to see the first stars and galaxies that formed in the universe, which are now so old and distant that their light has been relegated to the infra-red part of the spectrum by the “red shift” caused by the universe’s expansion. These wonders can be observed only from space, because ozone and water in the Earth’s atmosphere absorb light at those wavelengths.

Atlantis’s crew will, as well, add a “cosmic origins spectrograph” to the telescope, to parse light in a way that reveals which chemical elements it has been interacting with. This will allow astronomers to examine the evolution of galaxies, the formation of planets and the synthesis of chemical elements from the primeval hydrogen and helium that constituted the primitive universe. The spectrograph will also be used to investigate the structure and composition of matter concentrated in the “cosmic web”—long, narrow filaments of galaxies and intergalactic gas separated by huge voids. To do this, it will look at what happens to the light coming from faint, distant quasars as it passes through the web. Absorption of this light should reveal the composition and specific location in space of the constituents of the cosmic web, illuminating both the large-scale structure of the universe and progressive changes in the chemical composition of matter as time has gone by.

More prosaically, Hubble will receive new protective blankets, gyroscopes and batteries, a unit that transmits data to Earth will be replaced, and two existing instruments will be repaired. The upgrade should keep it running until 2014 when its successor, the James Webb space telescope, is supposed to be launched. Meanwhile, on May 14th, the European Space Agency should have added its own contribution to the study of the infant universe. It was due, as The Economist went to press, to launch two satellites the more familiar way, aboard a disposable rocket.

Peering into the cradle

One of these satellites, <em>Planck</em>, will look at the cosmic microwave background, a snapshot taken a mere 380,000 years after the Big Bang. That was the moment when matter started to coalesce and the universe became transparent. The radiation of the microwave background is mostly uniform, but small variations in its intensity show the origins of what went on to become galaxies, stars, planets and, in at least one instance, intelligent life. The first snapshot of the infant universe was made in 1992 and a second, more detailed, followed in 2003. Mapping the cosmic microwave background is hard because the Milky Way itself shines quite brightly at these wavelengths, making the background hard to discern. <em>Planck</em> is expected to generate as sharp an image as is physically possible, given the foreground glare.

Astronomers are hopeful that Planck will be able to identify how dark matter, a mysterious substance that makes up a quarter of the universe, forms larger structures that, by exerting a strong gravitational pull, determine the distribution of more familiar (but rarer) visible matter. They will examine temperature variations in the microwave background amounting to a few millionths of a degree, to see whether they can discern such features in it. Meanwhile, another team will be listening for the echoes of primordial gravitational waves—ripples in the fabric of space and time.

The second European satellite, Herschel, will scrutinize the universe at infra-red wavelengths. Stars and planets form within swirling clouds of dust and gas that visible light cannot penetrate, but which infra-red radiation can. Herschel will study the formation of galaxies and examine how they age. It will also peek at star-forming regions within galaxies.

When Edwin Hubble, the astronomer after whom the space telescope is named, looked at the skies in the 1920s using what was then the world’s largest telescope, he found that there were galaxies outside the Milky Way, an observation that profoundly shocked his contemporaries. Max Planck founded quantum theory, and thus wrecked the Newtonian universe. And William Herschel discovered Uranus, the first planet unknown to the astrologers of old. If the new and refurbished instruments named after these scientific mould-breakers do as much in the next few years as their eponyms did, it will, indeed, be an exciting time for astronomy and physics.

Source: The Economist