Wonders of the Universe

HOW TO FIND EXOPLANETS

One of the most exciting areas of current astronomical research is the hunt for planets around other stars – known simply as exoplanets – which are potential homes for extraterrestrial life. Until recently such a search would have been impossible, as planets are too faint to see over interstellar distances, however, thanks to new modern instrumentation, we are now able to detect the telltale signals of exoplanets using two main techniques: the radial velocity method and the transit method. With these techniques, individual planets and even planetary systems have been discovered around hundreds of stars. Masses of these extrasolar planets range from a few times that of Earth, to the size of 25 Jupiters. Whether a planet could support life depends on its distance from the parent star. Around each star is a ‘habitable zone’, in which temperatures are suitable for water to exist as a liquid. The size of this zone depends on the energy output of the star; the faintest ones have the closest, narrowest zones. The red dwarf Gliese 581 is believed to have at least one planet within its habitable zone.

Nathalie Lees © HarperCollins

As we observe all the cosmic structures around us in spectacular detail, each tells us something different about the life cycle of the stars. However, something much deeper can be learnt from understanding the existence of stars: they are the ultimate origin of all but the simplest of Leucippus’ and Democritus’ long-sought-after atoms, and as such are the building blocks of ourselves. To comprehend how the stars could play such a vital role in our existence, we must momentarily step back from the skies and come firmly back down to Earth.

The largest mountain range in the world, the Himalayas is also the youngest. This panorama, taken from the top of Kala Pattar in the Sagarmatha National Park, Nepal, shows only a fraction of its scale. Understanding the creation of these impressive mountains helps us to answer many questions about the structure of all living elements in the Universe.