Super-Earths: are we close to finding an Earth 2.0?

For decades, scientists have searched for an Earth-like world. Have they finally found one?

Scientists have found a staggering 7000 exoplanets – planets that orbit stars outside our solar system – but are still searching for that elusive one similar to Earth itself. That is, until the recent discovery of a “super-Earth.”

A super-Earth is a rocky exoplanet that’s significantly bigger than Earth, and smaller than Neptune and Uranus. The “earth” element to the term is only applicable to the mass, and not the surface quality or habituality.

The experts at the University of Geneva have found a potential candidate for a super-Earth called HD 20794 d. At 19.7 light years away, it’s “in the very close neighborhood of Earth.”

One can’t help but wonder if super-Earths are the most likely place for finding life elsewhere, and how close we are to finding a truly habitable world.

Why super-Earths dominate the search

These super-planets are usually rocky and can be anywhere between 1.5 and 10 times bigger than the Earth. These planets may be prime candidates for habitability because they often have stronger rates of gravity, which can help retain the atmosphere and protect against space radiation.

Furthermore, current technology is optimum for detecting these planets. The scientists use two spectrographs – instruments that measure wavelengths of light, or its spectrum, like a prism breaking light into a rainbow – to measure shifts in the star's light.

If the star wobbles, it suggests a planet is pulling on it, and then the mass and orbit of the planet can be detected.

Scientists work to define a “habitable zone,” which means that if it’s too close to a star, the water heats and evaporates, and too far, it freezes. Also, the atmospheric conditions need to be just right, so a thick atmosphere traps heat, like on Venus, whereas a thin one loses heat, like on Mars.

The HD 20794 d is a curious planet, as it follows an elliptical orbit, which is oval-shaped, instead of circular. In an elliptical orbit such as this, the distance often changes, meaning that the temperature will fluctuate a lot.

The experts exploring new worlds

The University of Geneva is particularly prestigious for researching phenomena like this, and scientists Xavier Dumusque and Michael Cretinger have been researching these exoplanets for over twenty years.

There are three exoplanets worth considering: HD 20794 d, Kepler-442b, and Proxima Centauri b.

• Kepler-442b appears to have the most ideal conditions due to its stable orbit, but at 1,200 light years away, it’s far beyond our reach.
• Proxima Centauri b is much closer, at 4.24 light years, but its proximity to a red dwarf star means it likely experiences extreme radiation.
• That makes HD 20794 d an interesting case – its proximity (19.7 light years) and position in the habitable zone are promising, though more research is needed to understand how its elliptical orbit affects its potential habitability.

This kind of research seems to inch us closer to answering that burning question: “Are we alone?” While HD 20794 d might not be a “second Earth,” it leaves a sense of optimism about where life might be found elsewhere.