Astronomers are using NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton to investigate whether nearby stars could host habitable exoplanets. 

NASA's Chandra Checks Habitable Exoplanets

The research focuses on the radiation these stars emit, which could impact conditions for life. This work aims to guide future observations with next-generation telescopes, which hope to capture the first images of Earth-like planets.

Researchers are examining stars close to Earth that future telescopes could take images of planets in the stars' habitable zones. These zones are regions where planets could have liquid water on their surfaces. 

According to NASA, although the images of these planets will be mere points of light, their different wavelengths of light will provide crucial information about their surface compositions and atmospheres, 

Breanna Binder of California State Polytechnic University in Pomona, who led the study, emphasized the importance of understanding the amount of harmful X-rays from a planet's host star. She pointed out that without this knowledge, a key element in determining a planet's habitability would be missing.

Binder and her colleagues started with a list of stars close enough to Earth that future telescopes could image planets within their habitable zones. The Habitable Worlds Observatory in space and Extremely Large Telescopes on the ground are among those telescopes set to begin operating in the next decade or two.

Using X-ray data from Chandra and XMM-Newton, the team analyzed which stars could potentially host planets with conditions suitable for life. They looked at the brightness of the stars in X-rays, the energy of the X-rays, and the variability in X-ray output, such as flares. 

Sarah Peacock, a co-author of the study from the University of Maryland, Baltimore County, noted that they had identified stars where the X-ray radiation environment in the habitable zone is similar to or even milder than that in which Earth evolved. These conditions might be crucial for maintaining a rich atmosphere like Earth's.

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Analyzing the X-ray of Nearby Stars

The researchers utilized data collected over nearly 10 days from Chandra observations and around 26 days from XMM observations to analyze the X-ray characteristics of 57 nearby stars. 

NASA said that these planets resemble giants such as Jupiter, Saturn, or Neptune, with only a small number potentially being less than twice the mass of Earth. NASA further noted that numerous planets are likely orbiting stars in the sample, specifically those comparable in size to Earth, that remain undetected. 

Transit studies, which detect slight dimming in starlight as planets pass in front of their stars from our planet's viewpoint, often overlook many planets due to specific geometric requirements for detection. According to NASA, this decreases the possibility of identifying transiting planets within a small sample of stars.

The alternative primary method for identifying planets involves monitoring the gravitational tug induced on a star by orbiting planets. This approach primarily identifies giant planets located relatively close to their host stars.

This investigation forms part of an ongoing endeavor to comprehend which stars are most likely to sustain habitable planets. By studying the X-ray emissions from these stars, astronomers aim to determine which stars possess the most favorable conditions for supporting life. 

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