Hot Jupiters and Cold Nomads

The exoplanet research is advancing rapidly. Nearly 4000 exoplanets are now known. Completely new and strange types of worlds have been discovered. Many of them are  Hot Jupiters, i.e. giant planets that are located very close to their parent stars. Other may be ocean planets which have all-covering oceans which can be hundreds or thousands of kilometres deep. The by far coldest ones are the nomad planets, which move in the interstellar space without belonging to any star at all.

It is astoundingly much information that can be extracted from the normally very faint light that the astronomers have to work with. Nevertheless, one should keep in mind that artistic visualisations (like the one above) have to be taken with a grain of salt.

Basically, there are two types of measurements that can be made; photometric and spectroscopic. Using photometry you can measure very small changes in the light of the parent star. With spectroscopy a detailed analysis of various wavelengths in the light of the parent star are made. But then you need more light to begin with, in order to be able to measure anything. With the giant telescopes that now are being constructed spectroscopy will be made in much greater detail and for much fainter light sources.

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