Astronomers find a potentially habitable Earth-sized planet

Astronomers have identified a new Earth-sized planet 146 light-years from our solar system that could sit in the habitable zone of its star.

The discovery raises hopes for finding nearby worlds like our own, even as scientists caution that the planet may be bitterly cold.

The candidate planet, known as HD 137010 b, orbits a sun-like star and is estimated to be around 6% larger than Earth. Researchers say it has about a 50% chance of lying within the star's habitable zone, the region where liquid water could exist.

The planet was detected using data from Nasa's Kepler space telescope during its extended K2 mission in 2017. An international team of scientists from Australia, the UK, the US, and Denmark analysed a faint signal caused when the planet briefly passed in front of its star, creating a slight dip in brightness.

Dr Chelsea Huang of the University of Southern Queensland said the planet completes one orbit in roughly 355 days, close to Earth's year. She added that its relative closeness makes it especially valuable for future study.

The initial signal was first spotted by citizen scientists through the Planet Hunters project. One of them was Dr Alexander Venner, now the study's lead author, who took part while still at secondary school. He later returned to the data as a professional researcher and confirmed the finding.

Despite the excitement, scientists stress that HD 137010 b remains a candidate planet. Only one transit has been observed so far, while three are usually required for confirmation. Its star is cooler and dimmer than the Sun, which means surface temperatures on the planet could fall below minus 70 degrees Celsius.

The research article appeared this week in Astrophysical Journal Letters.