A recent telescope survey has given scientists no indication that Planet K2-18b, an Earth-sized planet orbiting in a habitable zone about 110 light years away from ours, has an atmosphere. The results of the survey, conducted by an international team of researchers from England, Ireland, and Canada, have recently been published in Nature Astronomy.
Planet K2-18b is one of numerous planets discovered outside our solar system, known as exoplanets. Of the thousands of exoplanets found since the mid-1990s, K2-18b has been particularly interesting for scientists. Researchers had predicted that it was likely similar to Earth in size and composition, and had the potential to host an atmosphere. These predictions encouraged researchers to conduct the telescopic survey which ultimately found no evidence of an atmosphere.
What is Planet K2-18b?
Planet K2-18b is an exoplanet located in its star system’s ‘habitable zone.’ It was discovered in 2015 by the European Space Agency’s orbiting telescope, the Hubble Space Telescope. At the time of its discovery, the planet was estimated to be about 8.3 times the mass of Earth and twice its radius.
Planet K2-18b is the first super-Earth exoplanet discovered to be located in a habitable zone. This means that it lies in an area where temperatures are not too hot or too cold for water to exist in liquid form. As a result, the planet was highly regarded as a point of research interest for scientists.
How Was the Survey Conducted?
In order to gauge the presence of an atmosphere around the exoplanet, researchers used the Hubble Space Telescope to measure the transit of light from K2-18b’s host star whilst the planet crossed in front of it. This type of observation is known as transmission spectroscopy and it enables researchers to measure the planet’s emission levels on a molecular level. The researchers looked specifically for molecules indicative of potential atmospheres, such as molecular hydrogen or helium.
However, during the observations, the team found that the amount of light dimming while the super-Earth transited its star was consistent with a solid surface and not an atmosphere. This suggests that K2-18b does not possess an atmosphere.
What The Results of the Survey Mean
It is yet unclear why K2-18b has no atmosphere, as many exoplanets thought to be of similar composition have been found to have atmospheres. Scientists hope that further observational studies can help to explain this unusual phenomenon.
The results of the survey also have implications for scientists who are searching for possible signs of life on distant exoplanets. Although the presence of water vapour around a planet does not necessarily indicate the presence of life, it does mean that the planet could potentially provide a habitat for life.
The study authors believe that the findings open a new opportunity for the search for habitable super-Earths. Co-author of the study, Dr. Björn Benneke from the University of Montreal stated:
“This research proves that a large amount of caution must be taken when finding potentially habitable planets. Even though K2-18b is an exciting opportunity to search for signs of life, the present data suggest that it has no significant atmosphere.”
The results of the telescope survey conducted on Planet K2-18b have revealed that the exoplanet may not have an atmosphere. The survey adds to the evidence that suggests atmospheres are not necessarily present on exoplanets. The finding has raised questions about why K2-18b may not have an atmosphere, and it also serves as a reminder that more research needs to be done to find habitable planets.
