2019 Nobel Prize in Physics(2)
Reason for Award
for the discovery of an exoplanet orbiting a solar-type star
Laureates
Switzerland
Switzerland
Explanation
In 1995, Dr. Mayor and Dr. Queloz found a new planet orbiting a star 50 light-years away. The star is similar to our Sun, but its planet circles in just four days and is a very hot gas giant. Their discovery turned the dream that “other stars might have planets” into reality. Today we know more than 4,000 such planets, showing the universe is even busier than we thought. The finding also guides the search for worlds where life could exist.
Related Keywords
exoplanet
Exoplanets are planets that orbit stars outside the Solar System. More than 4,000 have been confirmed since the first discovery in 1995. They show remarkable diversity in size and orbit, many unlike our own system. Atmospheric studies have begun detecting molecules such as water vapour and methane. Exoplanet science is key to assessing the potential for life elsewhere.
radial velocity method
The radial-velocity (RV) method measures periodic shifts in stellar spectral lines caused by the gravitational pull of an orbiting planet. The velocity changes are only a few metres per second, requiring high-resolution spectrographs and stable wavelength references. Hot Jupiters were found first because they induce large amplitudes. New instruments like HARPS and ESPRESSO target centimetre-per-second precision to detect Earth-like planets. The RV technique provides direct estimates of planetary mass and orbital eccentricity.
hot Jupiter
Hot Jupiters are gas giants with Jupiter-like masses that orbit extremely close to their stars, completing orbits in days. Their high temperatures create bloated atmospheres, sometimes showing mass loss driven by stellar winds. They likely form in the outer protoplanetary disk and migrate inward through disk interactions. Their deep transits make them observationally favourable. Their unusual nature reveals diverse evolutionary pathways in planetary systems.
transit photometry
Transit photometry measures the slight dimming of a star when a planet passes in front of it. Light curves yield the planet’s radius and orbital period. Combined with transmission spectroscopy, molecular absorption lines reveal atmospheric composition. Space telescopes like Kepler and TESS have detected thousands of transits. Together with RV data, density can be derived to distinguish rocky from gaseous planets.
high-resolution echelle spectrograph
Echelle spectrographs use staircase-arranged diffraction gratings to achieve resolutions R ≥ 50,000. Instruments like ELODIE, HARPS and ESPRESSO are notable examples. By recording many narrow absorption lines, they enable sub-m/s velocity precision. Temperature–pressure stabilisation and iodine-cell or laser-comb references are essential for stability. Echelle spectrographs are central to RV-based exoplanet detection.