Our heavenly bodies make for hot dates

Astronomy
September 29, 2006

Patrick Moore looks beyond the clouds to revel in images of a stunning cosmic almanac.

Many beautiful books on astron-omy have been published in recent years, but this new offering is the equal of any. Both authors are distinguished scientists: Jerry Bonnell is astrophysicist with the Universities Space Research Association, while Robert Nemiroff is a professor of physics at Michigan Technological University. They compile an exceptionally popular website, "Astronomy Picture of the Day" ( http:///apod.nasa.gov/ ), which receives more than a million hits a week. There are many people (myself included) who look at it as soon as they log on.

What they have done in this book is to select 365 of the best recent images - one for each day of the year - and reproduce them alongside with a page of appropriate text. All branches of astronomy are covered. There are photographs taken with the world's best telescopes, together with images from space and from other worlds - look, for example, at the Mars rover Spirit examining rocks in the crater Gusev, once a lake of liquid water, or Buzz Aldrin setting up equipment at the lunar Sea of Tranquillity, photographed by Neil Armstrong, the first man on the Moon. Comets, meteor storms, displays of polar lights, tremendous outbursts on the Sun, images of nebulae, star clusters, galaxies, quasars - all are here.

The book, of course, can be read straight through, cover to cover, but it is equally fascinating to dip in anywhere; no page will be disappointing. For example, what is the topic for August , the day on which this review is being written? Open the book, and we find that we are seeing the centre of the Virgo cluster of galaxies, well over 50 million light-years away; we are looking back in time as well as into deep space. There are three obvious galaxies, two elliptical and one spiral; it is humbling to realise that each of these systems includes many tens of millions of suns and, no doubt, vast numbers of planets, Earth-like and otherwise.

Turn forward a few days, to August 31; we find here a beautiful photograph of Albireo, a double star in the constellation of the Swan, with a golden-yellow primary and an azure-blue companion. On the next day, September 1, the scene is dominated by clouds of hydrogen gas, glowing brilliant red; this nebula, IC 1396, in the far-northern constellation of Cepheus, is an active star-forming region - a true stellar nursery, 2,000 light-years away, where new stars are being born; about 5,000 million years ago, our own Sun too was created inside a nebula.

The present Solar System is not neglected. For May 28, two visiting comets are shown, catalogued officially as C2002 T7 and C/2001 Q4; they are not spectacular, but they are certainly interesting and are rare visitors to the inner part of the Solar System. By May 31, comet T7 had become bright enough to be seen with the naked eye and had developed a long, complex tail that stretched right across the constellation of Pisces; Q4 also brightened and formed a tail. If you did not see them, you will not have another chance; neither comet will return for many centuries.

Another comet, Tempel 1, moves in a different sort of orbit; it has been seen regularly since it was discovered in 1875 by the German astronomer Ernst Tempel. The picture on July 3 shows it as it appeared at its return in 2005; it looks like a small fuzzy patch with a short blue-tinted tail. At this time it was seen against the background of the Virgo cluster of galaxies. On the following day it was hit by the probe Deep Impact , which crashed into the comet's nucleus at a speed of 9.5km per second and blasted out a large crater. Of course the impactor was destroyed and an expanding cloud of debris was photographed a few seconds later from the fly-by section of the spacecraft; it was found to contain complex ingredients such as silicate grains, iron compounds, hydrocarbons, clays and carbonates, so that one of the Nasa scientists likened it to "a cosmic souffle". Once the cloud cleared away, an amazing amount of detail could be made out on the nucleus itself, which is about 5km long and porous and fluffy. Comets are insubstantial things, and there had been suggestions that Tempel 1 might be fatally damaged by the collision but these fears proved to be groundless. Tempel continued sublimely on its way and will next return to perihelion in 2010, none the worse for the encounter.

From comets to planets. Mars has always had a special fascination for us, mainly because it is less unlike the Earth than any other body in the Solar System, and we cannot rule out the possibility of life there; the brilliant canal-building engineers have been banished to the realm of science fiction, but there may well be lowly organisms in underground lakes, or even seas. The entry for July 24 shows Mars close to the limb of the Moon and it looks surprisingly small - much smaller than an average lunar crater - but the Moon is our nearest neighbour in space, less than a quarter of a million miles away, while Mars is more than 100 times as far. Nevertheless, orbiters and landers have carried out detailed surveys of the Red Planet and its dwarf satellites, Phobos and Deimos.

The two rovers, Spirit and Opportunity , have been outstandingly successful and are still working, well beyond their expected lifetimes; Spirit stopped at a football-sized boulder, which was nicknamed the White Boat (February 5); Opportunity , on the opposite side of Mars, has found strange rock-and-iron spheres, which have been called "blueberries" (July 30). There are images of the Earth's non-identical twin, Venus, including its transit across the face of the Sun (June 4 and June 30), but there is also a transit picture of another kind (July 25) when two space vehicles, the Discovery shuttle and the International Space Station, were seen together against the solar disk. The odds against this being repeated seem to be astronomical in every sense of the term.

The Cassini spacecraft has provided stunning views of Saturn (December 8) and its rings (July 11) as well as its satellites, and carried the Huygens lander, which came down gently on Titan, Saturn's major satellite (January 21, May 3). The Galileo probe has swooped past Jupiter's satellite Europa (November 30) and shown the icy surface, which may overlie an ocean of water; who knows what may exist in that eerie, sunless sea?

Brilliantly coloured pictures of nebulae and galaxies dominate many of the pages. We must, of course, see the Hubble Ultra-Deep Field (March 6), which may look less spectacular but is appropriately described as "the deepest image of the universe ever taken in visible light". Hubble's most powerful camera concentrated on one small area of the sky over a long period; the area was selected because it seemed to contain no feature of note, but Hubble showed that it was crowded with galaxies about 13,000 million light-years away, so that we are now seeing them as they used to be when the universe was young.

To see a pair of closer galaxies in detail, turn to the page for March 5, where we find two systems, one spiral and one elliptical, 55 million light-years from us. They are pulling upon each other, and at the edge of the foreground edgewise-on spiral a burst of star formation has been triggered, resulting in the presence of young blue star clusters.

Before ending this review, I opened three pages entirely at random. I first opened at April 26, where I found an intriguing image of the nebula known officially as IC 443 but generally called the Jellyfish Nebula. This is not a galaxy, but the remnant of a star that exploded as a supernova 5,000 years ago in the constellation of the Twins, beside the bright stars Mu and Eta Geminorum.

My second random selection was for June 10 - sunset on Mars, as seen from the Spirit rover inside Gusev; the Sun is just about to dip below the distant wall of the crater. The high-altitude reddish dust in the Martian atmosphere means that twilight is prolonged, and the sky-glow may last for two hours after the Sun has actually set.

Finally, I opened the book at the entry for January 19, the launch of the New Horizons space probe from Cape Canaveral. It is to go to Pluto, no longer classed as a bona fide planet but still fascinating; we may learn more about it when New Horizons reaches it in 2015.

The pictures are cleverly selected - all aspects of astronomy are covered. The reproductions cannot be faulted and the text is lucid and authoritative. Moreover, the price is amazingly reasonable. This book is a gem, and should be in every scientific library, amateur or professional.

Sir Patrick Moore is the author of more than 60 books, mainly on astronomy.

Astronomy: 365 Days

Author - Jerry T. Bonnell and Robert J. Nemiroff
Publisher - Abrams
Pages - 744
Price - £19.95
ISBN - 0 8109 5715 9.

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