Today, at an international exoplanet conference
the team who built the High Accuracy Radial Velocity Planet Searcher,
better known as HARPS, the spectrograph for ESO’s 3.6-metre telescope,
reports on the incredible discovery of more than 30 new exoplanets,
cementing HARPS’s position as the world’s foremost exoplanet hunter.
This is the ESOcast!
Cutting-edge science and life behind the scenes of ESO, the European Southern Observatory.
Exploring the ultimate frontier with our host Dr J, a.k.a. Dr Joe Liske.
Hello and welcome to the ESOcast.
In this episode, we have another major exoplanet discovery coming to you from ESO’s La Silla Observatory.
And we're not just talking about just one exoplanet, we're talking about no less than 30!
It's exoplanets galore!
Including these new results, data from HARPS has led to the discovery
of more than 75 exoplanets in 30 different planetary systems.
In particular, thanks to its amazing precision, the search for small planets,
those with a mass of a few times that of the Earth — known as super-Earths and Neptune-like planets —
has been given a dramatic boost.
HARPS has facilitated the discovery of 24 of the 28 planets known with masses below 20 Earth masses.
As with the previously detected super-Earths, most of the new low-mass candidates reside in multi-planet systems,
with up to five planets per system.
In 1999, ESO launched a call for opportunities to build a high resolution, extremely precise spectrograph
for the ESO 3.6-metre telescope at La Silla, Chile.
Michel Mayor, from the Geneva Observatory, led a consortium to build HARPS,
which was installed in 2003 and was soon able to measure the back-and-forward motions of stars
by detecting small changes in a star’s radial velocity as small as 3.5 km/hour, or a steady walking pace.
Such a precision is crucial for the discovery of exoplanets.
The radial velocity method, which detects small changes in the radial velocity of a star
as it wobbles slightly under the gentle gravitational pull from an unseen exoplanet,
has been most prolific method in the search for exoplanets.
In return for building the instrument, the HARPS consortium was awarded 100 observing nights per year over a five-year period.
Now this time was used to carry out one of the most ambitious systematic searches for exoplanets so far implemented worldwide
by measuring the radial velocities of hundreds of stars that might harbour planetary systems.
The programme soon proved very successful.
Using HARPS, Mayor’s team discovered — among others — the first super-Earth around Mu Arae;
the trio of Neptunes around HD 69830;
Gliese 581d, the first extrasolar planet in the habitable zone of a small star;
and the lightest exoplanet ever detected around a normal star, Gliese 581e.
More recently, they found a potentially lava-covered world, with density similar to that of the Earth’s.
These observations have given astronomers great insight into the diversity of planetary systems
and they have helped us to understand how they might form.
The HARPS consortium was very careful in their selection of targets,
with several sub-programmes aimed at looking for planets around solar-like stars,
low-mass dwarf stars, or stars with a lower metal content than the Sun.
Although it was thought that giant planets couldn’t form around low-mass stars,
the HARPS team has found several of them.
The number of exoplanets known around low-mass stars — so-called M dwarfs —
has also dramatically increased, including new super-Earth candidates.
Although the first phase of the observing programme is now officially concluded,
two new programmes have been started.
And the team still expects to make many new discoveries from the first 5 years of data.
There is no doubt that HARPS will continue to lead the field of exoplanet discovery,
and especially pushing towards the detection of Earth-type planets.
This is Dr J signing off for the ESOcast.
Join me again next time for another cosmic adventure.
ESOcast is produced by ESO, the European Southern Observatory. www.eso.org
ESO, the European Southern Observatory, is the pre-eminent intergovernmental science and technology organisation in astronomy
designing, constructing and operating the world's most advanced ground-based telescopes.
Transcription by ESO ; translation by —