The International Astronomical Union by Johannes Andersen & David Baneke & Claus Madsen

Author:Johannes Andersen & David Baneke & Claus Madsen
Language: eng
Format: epub
ISBN: 9783319969657
Publisher: Springer International Publishing

Artist’s impression of the Gaia launch into orbit. Photo: ESA/D. Ducros

All this resulted in an impressive amount of new data—in electronic form, since photographic technology had by now been completely replaced by electronic detectors. The digital data could be exchanged through the rapidly expanding Internet, and analysed with ever more powerful computers. With time, the computers became so fast and powerful that ‘computational astronomy’, based on detailed numerical modelling of physical processes, became a specialised branch of astronomy in itself, and a new source of knowledge next to observational and theoretical astrophysics.

The wealth of data and increasingly detailed computations brought many new insights in the physics of the Universe. High-energy astrophysics advanced rapidly, as did the theoretical understanding of the interstellar matter, which turned out to be surprisingly rich in complex molecules. The new observations also raised new questions, however, especially after the discovery in 1998 that the expansion of the universe is accelerating. This was the opposite of what everybody had expected and discussed: a uniform or even slowly decelerating expansion. The evidence came from Type Ia supernovae, which had been discovered to larger and larger distances, thanks to modern technology and more efficient search strategies. Moreover, the correlation between their peak luminosity and their decay times made it possible to use them as ‘standard candles’.

Two competing teams had used different techniques to reach the same result, and their papers announcing the discovery were published nearly simultaneously. Saul Perlmutter, Brian Schmidt and Adam Riess also shared the 2011 Nobel Prize as well as the Gruber Cosmology Prize for this discovery. Their discovery supported cosmological models that stated that visible, baryonic matter only encompasses a mere ~5% of the Universe; later modelling concluded that the other 95% consists of ‘dark matter’ (~25%), the existence of which had already been concluded from other observations, and an even more mysterious ‘dark energy’ (~70%), the nature of which is still completely unknown.

Interestingly, one of the most spectacular discoveries of the 1990s was done with a relatively small telescope. In 1995, Swiss astronomers observing at the classic Haute-Provence observatory in France announced that they had found a planet with a surprisingly short period of only 4 days, orbiting another star than the Sun. There had been earlier claims, but this was trustworthy enough to inaugurate a rush to find new ‘exoplanets’, as they were called.

Earlier attempts had all assumed that exoplanetary systems were analogous to the Solar System, but the first actual exoplanets were gas giants in extremely close orbit around their star. They did not resemble anything in the Solar System at all, so all models could be thrown out the window. These massive, short-period ‘hot Jupiters’, as they were soon dubbed, were of course the easiest to discover, but when transiting exoplanets were also found, giving access to approximate radii and densities, sceptics were silenced. Overnight, exoplanet research became a major field of astronomy.

The desire to understand exoplanetary systems in general is also motivated by the fundamental, underlying human question: are we

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