Astronomers spot nearby Earth-like planet in possible habitable zone

Astronomers have identified a potentially habitable, Earth-sized planet about 146 light-years from Earth, raising fresh interest in nearby worlds that could one day be studied in detail by next-generation telescopes.

The candidate planet, known as HD 137010 b, is estimated to be about 6% larger than Earth and orbits a sun-like star with a period of roughly 355 days. An international team of scientists from Australia, the UK, the US and Denmark discovered the planet by analysing data collected in 2017 by NASA’s Kepler space telescope during its extended K2 mission, The Guardian outlines. 

Dr Chelsea Huang, a researcher at the University of Southern Queensland (USQ) and a co-author of the study, said the planet has an orbit similar to Earth’s and “about a 50% chance of residing in the habitable zone” of its host star.

“What’s very exciting about this particular Earth-sized planet is that its star is only [about] 150 light-years away from our solar system,” Huang said. “The next best planet around a sun-like star, in a habitable zone, [Kepler-186f] is about four times farther away and 20 times fainter.”

HD 137010 b was detected using the transit method, which measures the slight dimming of a star’s light as a planet passes in front of it. The initial signal was identified by citizen scientists participating in the Planet Hunters project, including the study’s first author, Dr Alexander Venner, who was a high school student at the time.

“I contributed to this citizen science project called Planet Hunters back when I was in secondary school, and it was a big part of how I got into research,” Venner said. “It was an amazing experience to go back to this work and dig up such an important discovery.”

Huang said the research team was initially sceptical of the finding.

“The team’s first reaction to the discovery was ‘that this cannot possibly be true’,” she said. “But we double checked and triple checked everything and … it’s a textbook example of a transit of a planet.”

The relative brightness and proximity of the host star could make HD 137010 b a key target for future observation.

“The brightness and closeness of the star it orbits puts it ‘within reach of [being observed with] the next generation of telescopes’,” Huang said. “I’m sure this will be the first target to be observed when the technology gets there.”

The star is cooler and dimmer than the Sun, meaning the planet’s surface temperature may be more comparable to Mars, potentially dropping below –70°C.

Dr Sara Webb, an astrophysicist at Swinburne University who was not involved in the research, described the discovery as “very exciting” but cautioned that more evidence is required before HD 137010 b can be confirmed as an exoplanet.

“There is only one transit [detected], and typically in planetary science we’re talking a gold standard of three [detections],” Webb said.

She added that while the planet could be Earth-like, another possibility is that it is “something called a super snowball. Essentially, a big, icy world that potentially has a lot of water, but a lot of it’s frozen.”

Although the planet is relatively close in astronomical terms, Webb noted that human travel there remains far beyond current capabilities.

“Though the planet ‘is very close in the grand scheme of our galaxy’,” she said, “if we were to try and get there, it would take us tens of thousands, if not hundreds of thousands of years travelling at the current speeds that we can.”

By Sabina Mammadli