New horizons

The revolutionary new generation of telescopes brought entirely new types of object within the range of astronomers. While the Hubble Space Telescope's mirror was not large, its position above the atmosphere meant it did not lose light through absorption, and its resolution was second to none. In contrast, giant ground-based telescopes such as the Keck and the VLT can see deeper and fainter, but not quite as clearly as the HST Recording technology has changed too—electronic CCDs (see pp.144—5) respond to light in

dots represent / galaxies: 1,059 galaxies appear on the map

Milky Way

750 million light-years

500 million light-years 250 million light-years dots represent / galaxies: 1,059 galaxies appear on the map

Milky Way

750 million light-years

500 million light-years 250 million light-years the edge of the solar system

The latest telescopes have detected extremely faint objects in our cosmic backyard, such as the large Kuiper belt object 2003 UB313, seen moving slowly against the background stars.

a different way from photographic plates, and because they record digitally, data from many short exposures can be combined into a long-exposure image, in a way that was impossible with conventional photography Among the discoveries made in this new era have been the Kuiper belt beyond Pluto, extrasolar planetary systems, and the deep structure of the universe itself.

limits of the universe

Astronomers can now measure the red shifts of thousands of distant galaxies. Plotting their distribution reveals features such as the filaments and voids of the large-scale universe. One of the first such maps (left) showed galaxies distributed in an unusual "stick figure" shape.

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