The discovery of the first exoplanet back in 1995 received widespread media attention and was seen as an important landmark in a new research field, the planet hunting research.
The discovery was very important not for its magnitude, the planet itself, but because what it means for the future of planetary discovery and mapping. Planet hunting program is leading humankind on a voyage of unprecedented scope promising insight into ours origins and beyond.
Exoplanet exploration’ goal is to find and characterize planetary systems and Earth-like planets around nearby stars, an essential step to reach our ultimate goals, the discovery of habitable planets and evidence of life on other planets.
First planet hunting phase has been done with ground telescopes around the world, pushing the limits of their ability but with the launch of NASA Kepler Space Telescope in 2009, researchers have found thousands of planets orbiting other stars, dozens of these exoplanets are Earth-size planets in or near the habitable zone — the range of distance from a star where liquid water might pool on the planet’s surface.
Future NASA missions, like James Webb Space Telescope in space, will extend this exoplanetary census much farther in the coming years, discovering and characterizing more and more planets beyond our solar system.
Methods of detection One of the most popular and most effective method for locating and confirming extrasolar planets is called the Doppler radial velocity method. This technique largely relies on the fact that a star does not remain completely stationary, a planet’s gravity also affects the host star in return.
A planet could produce changes in position and velocity of the star as they orbit their common center of mass, as result, the host star moves, ever so slightly, in a small circle or ellipse, responding to the gravitational tug of its smaller companion. So, using highly sensitive spectrographs, researchers can track a star’s spectrum, searching for periodic shifts and thus picking out exoplanets across the night sky.
The radial velocity method has proven itself fruitful in the last decades both for the identification of new exoplanet and the confirmation of exoplanets detected by other methods. But with the recent developments in planet hunting, this method becomes gradually inefficient especially when it used to detect planet around small, cool stars (also called M-stars).
To date, Kepler telescope have found thousands of exoplanets, many of them are orbiting M-dwarf stars. So, its become clearly that M cool stars class represent valuable targets for the identification of new Earth-mass planetary companions in the habitable zone.
However, in the case of these low-mass stars, looking at that wobble with the radial velocity becomes gradually harder, as I say, due to the false-positive signals. The wobble could indicate the presence of a planet, but other things can also cause the phenomenon (e.g stellar spots). That’s why researchers decided to refine the radial velocity technique in this latest study.
In a new study published online in The Astrophysical Journal, the Carnegie Institute researchers describe how they fix the radial velocity’ accuracy problem.
New era of planet hunting
Researchers developed a methane isotopologue gas cell that offers a high absorption line density in the regime of near-infrared wavelengths. This development represents a better calibration tool to improve the overall technology for the radial velocity work.
Basically, they still use the radial velocity technique, but they switch from visible to infrared wavelengths when making measurements.
Switching from the visible spectrum to the near-infrared, the wobble effect caused by an orbiting planet will remain the same regardless of wavelength,
Jonathan Gagne, from Carnegie Institution for Science in the US, explained.
But looking in the near-infrared will allow us to reject false positives caused by sunspots and other phenomena that will not look the same in near-infrared as they do in visible light,
In the paper, they also present the first results of this new tool. Researchers use this technological upgrade at the NASA Infrared Telescope Facility located at the top of Mauna Kea in Hawaii to survey 32 late-type, nearby stars mostly selected from known members of young moving groups.
Fast results? Scientists confirmed several known planets and binary systems, and also identified a few new planetary candidates.
Our results indicate that this planet-hunting tool is precise and should be a part of the mix of approaches used by astronomers going forward,
said Peter Gao from California Institute of Technology.
It is amazing to think that two decades ago we had only just confirmed exoplanets actually existed and now we are able to refine and improve those methods for further discoveries,
This new tool could be huge when it comes to confirming exoplanets in the future. It also could allow the detection of Super-Earths near the habitable zone of mid-M dwarfs in the solar neighborhood.
These will serve as a crucial complement to transiting exoplanet studies, as the combination of both the radial velocity and transit methods will provide a measurement of the mean planet density and put strong constraints on the physical properties of future Earth-like discoveries.