Unveiling 18 New Earth-Sized Exoplanets: One Holds Promise for Life
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Chapter 1: The Discovery of New Exoplanets
Recently, astronomers have made an exciting discovery: 18 Earth-sized planets orbiting distant stars, identified through data collected by the now-retired Kepler spacecraft. Among these, one stands out as the smallest exoplanet ever detected, while another exhibits conditions that may support life.
The majority of exoplanets are located by monitoring the decrease in a star's brightness as a planet passes in front of it, obstructing light from reaching Earth. This transit method is more effective for larger planets, which block more light and create noticeable shadows. However, the brightness of stars can vary, appearing brighter at their centers than at their edges, complicating the detection of smaller planets. To address this, researchers at the Max Planck Institute for Solar System Research (MPS) have developed a sophisticated algorithm capable of identifying the subtle signs of these smaller celestial bodies.
“In many of the planetary systems we analyzed, the newly discovered planets are the smallest,” noted Kai Rodenbeck from the University of Göttingen.
The transit of smaller planets induces a gradual curve in the light emitted by their host stars. By factoring this curve into their calculations, researchers can now detect smaller planets with unprecedented accuracy. This innovative algorithm from MPS specifically targets smaller worlds that might have been overlooked in previous Kepler data and other observational efforts.
In their initial test, researchers examined 517 stars in the Kepler dataset, each already known to host at least one transiting planet. The smallest planet identified in this latest study measures just 69% of Earth's size, while the largest is only twice the size of our home planet. Most of the newly discovered planets are located in close proximity to their stars, exposing them to extreme temperatures that could reach between 100 and 1000 degrees Celsius (approximately 200 to 1800 degrees Fahrenheit).
The 18 exoplanets found in this recent investigation vary in size from smaller than Earth to slightly smaller than Neptune. Approximately 96% of the 4,000 exoplanets identified to date are significantly larger than Earth. Larger planets block more starlight and create sharper shadows, making them easier to detect. In contrast, smaller planets exhibit less pronounced brightness variations during transits.
“…[A] stellar disk appears slightly darker at the edge than in the center. When a planet moves in front of a star, it therefore initially blocks less starlight than at the mid-time of the transit. The maximum dimming of the star occurs in the center of the transit just before the star becomes gradually brighter again,” explained Dr. Rene Heller from MPS.
From 2009 to 2013, the Kepler space telescope surveyed 100,000 stars, revealing 2,300 exoplanets in various solar systems. After experiencing a malfunction, the mission was rebranded as K2, allowing it to continue its work. By the time it was decommissioned in the autumn of 2018, Kepler had studied over 100,000 additional stars.
Among the newly identified planets, only one may be suitable for life as we know it: EPIC 201238110.02. Although its name is not particularly inviting, it could be the most hospitable of the newly discovered worlds. This planet is larger than Earth but smaller than Neptune, located within its star's habitable zone, where conditions might allow for liquid water on its surface.
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Before the launch of the Kepler spacecraft in 1992, no exoplanets were known to exist. Since then, Kepler has uncovered thousands, and now the Transiting Exoplanet Survey Satellite (TESS) is actively contributing to our growing catalog of alien worlds.
Researchers at MPS are optimistic that their new algorithm could eventually uncover up to 100 previously hidden planets in existing datasets, marking a significant advancement in our exploration of worlds beyond our own.