NASA’s Chandra X-ray space telescope has taken a significant step in the search for alien life by creating a three-dimensional map of stars close to our sun. This map could guide astronomers in their quest to find exoplanets capable of supporting life.
Chandra, celebrating 25 years in orbit, has mapped stars within a radius of 16.3 to 49 light-years from Earth. This proximity allows telescopes to collect light spectra from potential planets residing in the habitable zones of these stars. The habitable zone, also known as the “Goldilocks zone,” is the region around a star where conditions are just right for liquid water to exist on a planet’s surface. By analyzing the spectra, scientists can potentially identify features like continents, oceans, clouds, and atmospheric composition.
Chandra’s X-ray capability is crucial for assessing a planet’s habitability. High-energy radiation like X-rays and ultraviolet radiation can strip a planet’s atmosphere and damage complex molecules essential for life, rendering it uninhabitable. Therefore, Chandra’s observations help determine which planets have been exposed to excessive radiation, allowing scientists to prioritize their search for potentially habitable worlds.
Breanna Binder, the lead researcher from California State Polytechnic University, emphasized the importance of understanding X-ray radiation: “Without characterizing X-rays from its host star, we would be missing a key element on whether a planet is truly habitable or not. We need to look at what kind of X-ray doses these planets are receiving.”
The team compiled the map by analyzing data from Chandra and the European Space Agency’s XMM-Newton telescope. They focused on 57 stars close enough for future telescopes like the Habitable Worlds Observatory and the Extremely Large Telescope to image orbiting planets. While being in the habitable zone is a promising factor, it doesn’t guarantee habitability. Venus and Mars, both within the sun’s habitable zone, are not suitable for life as we know it.
To further refine their list, the team measured the intensity, energy, and variability of X-rays emitted by the stars. Brighter and more energetic X-rays indicate a higher likelihood of atmospheric damage to orbiting planets.
“We have identified stars where the habitable zone’s X-ray radiation environment is similar to or even milder than the one in which Earth evolved,” explained team member Sarah Peacock from the University of Maryland. “Such conditions may play a key role in sustaining a rich atmosphere like the one found on Earth.”
Some of the stars in the map are already known to host exoplanets with sizes comparable to Jupiter, Saturn, Neptune, and Uranus. There could also be Earth-like planets within these systems yet to be discovered. The transit method, which relies on detecting dips in starlight as a planet crosses its star’s face, is less effective in finding Earth-sized planets orbiting at a greater distance. The radial velocity method, which detects the “wobble” caused by a planet’s gravitational pull on its star, also favors massive planets close to their stars.
“We don’t know how many planets similar to Earth will be discovered in images with the next generation of telescopes, but we do know that observing time on them will be precious and extremely difficult to obtain,” concluded team member Edward Schwieterman from the University of California, Riverside. “These X-ray data are helping to refine and prioritize the list of targets and may allow the first image of a planet similar to Earth to be obtained more quickly.”
The team presented their research at the 244th meeting of the American Astronomical Society in Madison, Wisconsin. Their findings provide valuable insights for future exoplanet searches, guiding astronomers towards the most promising candidates in the quest for life beyond Earth.
