HARPS stands for High Accuracy Radial Velocity Planet Searcher, and the instrument’s primary goal is to find new planets. The device was installed at the La Silla Observatory in Chile in 2003, and just a few months later, HARPS’ creators were rewarded with the discovery of the first new planet using the tool. To date, the instrument has discovered over 130 exoplanets, making it one of the most successful innovations in astronomy.
Our knowledge of the galaxy and universe is always growing, and with HARPS and other tools to detect more planets, humankind will benefit tremendously. It can have a tremendous impact on the economy and our resources if we devise ways to reach these planets and source valuable and rare elements. Ultimately, the impending question about whether we can colonise other planets and create conditions for humans to live on them may be answered. And it is all thanks to these new innovative techniques such as HARPS.
How HARPS Works to Find Planets Outside the Solar System
HARPS focuses on stars and can pick up tiny their tiny movements when a planet orbits around them. These are called Wobbles, and they happen because, during a planet’s orbit around its host sun, it moves the sun ever so slightly. This movement is due to the planet’s gravitational pull, which will cause the star to “wobble”, and even the slightest movement is detectable by HARPS. This is called the Radial Velocity Method, and whenever a star moves, its relative distance from the Earth changes.
HARPS has a spectrograph which allows it to calculate precise radial velocity movements with an accuracy of better than 1 metre per second. It is far more reliable than the classical fibre spectroscopy, which has an expected precision of around 10 metres per second. Every time a movement occurs, the colour of the star will change very slightly. The speed and distance of these movements give scientists the information they need to determine how big the planet is and how fast it orbits the host sun.
Key Innovations in the Design of HARPS
It is by no means the only instrument that is used to find new stars, but HARPS is recognised for its outstanding accuracy. This is down to a few design features that enhance HARPs’ performance.
Vacuum-Sealed Spectrograph Reducing Noise
One of the key elements of HARPS is its vacuum-sealed spectrograph that has a controlled temperature. This ensures that the results are not tainted by external factors such as changes in the temperature. Reducing the noise helps scientists to ascertain the exact movements and speeds of a planet.
Identical Optic Fibre Feeds for Stability
The dual optic fibres transmit the lights of the stars, and both feeds are mechanically stabilised to ensure that the results are clear. The results can pick up the slightest frequency modulations via the Doppler Effect.
Advanced Charge-Coupled Devices to Capture Crisp Images
The CCD used in HARPS is a light-sensitive circuit that creates images converting photons into electrons. The high resolution of HARPS’ CCDs captures a wide spectrum of colours. It is these that can calculate the movements of a planet down to an accuracy of 1m/s.
Most Significant Discoveries Using HARPS
The primary use of HARPs is to find planets that are similar to Earth. These exoplanets should have suns to orbit, and they should be in the habitable zone. Essentially, they should be far away enough from the sun to be able to accommodate life.
But HARPs has not only found such types of planets. It has also been used to discover new planetary systems as well as exoplanets of all sizes.
HD 330075 b – Extrasolar Planet
This was the first exoplanet to be discovered through HARPs. In February of 2004, the planet was spotted in the constellation of Norma. The planet is a gas giant, about three-quarters the size of Jupiter, and orbits around star HD 330075.
Gliese 581 – Planetary System
This big discovery came in 2007, and HARPs found an entire planetary system. The system is located in the constellation Libra and has several planets, including Gliese 581 d, which lies in the habitable zone of the planetary system.
Proxima Centauri b – Exoplanet
The findings of HARPs in 2008 and 2009 ruled out the existence of this planet, but anomalies were located in Proxima Centauri. Using more advanced instruments, Proxima b was discovered in 2016. This exoplanet is a similar size to Earth, and it has the potential to sustain life.
HD 85512 b – Exoplanet
This planet was discovered in 2011 in the constellation of Vela. It is a super-Earth, at least 3.6 times the mass of Earth. It is just outside the inner edge of the habitable zone, but in 2011, it was one of the best candidates for habitability.
HD 40307 – Planetary System
This planetary system was found in 2008 in the Pictor constellation. The system has at least 6 planets, including HD 40307 g, which lies in the habitable zone.
Is HARPS Still Finding Planets and Systems
The last discoveries using HARPS were made in 2013, and since it has been surpassed by more advanced tools. Scientists now use methods such as ESPRESSO at the European Southern Observatory or ESO. ESPRESSO can offer even more precise data and measure smaller radial velocity changes. Where HARPs could measure 10m/s, ESPRESSO can measure movements of 10cm/s
Although the information collected by HARPS is still relevant, the technology is no longer leading new discoveries as it did when it was launched.