This graphic shows a three-dimensional map of stars near the sun. These stars are close enough that they could be prime targets for searching for direct images of planets using future telescopes. The blue halos represent stars that were observed with NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton. The yellow star in the center of this diagram represents the position of the sun. The concentric rings show distances of 5, 10 and 15 parsecs (one parsec is approximately 3.2 light years). Credit: Cal Poly Pomona/B. binder; Illustration: NASA/CXC/M.Weiss
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This graphic shows a three-dimensional map of stars near the sun. These stars are close enough that they could be prime targets for searching for direct images of planets using future telescopes. The blue halos represent stars that were observed with NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton. The yellow star in the center of this diagram represents the position of the sun. The concentric rings show distances of 5, 10 and 15 parsecs (one parsec is approximately 3.2 light years). Credit: Cal Poly Pomona/B. binder; Illustration: NASA/CXC/M.Weiss
Using NASA’s Chandra X-ray Observatory and ESA’s (European Space Agency) XMM-Newton, astronomers are studying whether nearby stars could host habitable exoplanets, based on their ability to radiation that could destroy the potential conditions for life as we know it. This type of research will help guide observations with the next generation of telescopes aimed at taking the first images of planets like Earth.
A team of researchers examined stars close enough to Earth that future telescopes could take images of planets in their so-called habitable zones, defined as orbits in which planets could have liquid water on their surfaces. Their results were presented at the 244th meeting of the American Astronomical Society in Madison, Wisconsin.
All planet images will be single points of light and will not directly show surface features such as clouds, continents and oceans. However, their spectra – the amount of light at different wavelengths – will reveal information about the composition of the planets’ surfaces and atmospheres.
Several factors influence what might make a planet suitable for life as we know it. One of these factors is the amount of harmful X-rays and ultraviolet light it receives from its host star, which can damage or even destroy the planet’s atmosphere.
“Without characterizing the the study. “We need to look at what kind of X-ray doses these planets are getting.”
Binder and his colleagues began with a list of stars close enough to Earth that future ground- and space-based telescopes could obtain images of planets in their habitable zones. These future telescopes include the Habitable Worlds Observatory and extremely large ground-based telescopes.
Based on X-ray observations of some of these stars using data from Chandra and XMM-Newton, Binder’s team examined which stars might host planets that provide hospitable conditions for life to form and thrive.
The team studied the stars’ X-ray brightness, X-ray energy, and how much and how quickly their X-ray output changes, for example due to skin flares. Brighter, more energetic X-rays can cause more damage to the atmospheres of orbiting planets.
“We identified stars whose habitable zone X-ray environment is similar, or even milder, to that in which Earth evolved,” said Sarah Peacock, co-author of the study from the University of Maryland, Baltimore County. “Such conditions could play a key role in maintaining a rich atmosphere like that found on Earth.”
The researchers used data available in the archive from nearly 10 days of Chandra observations and about 26 days of XMM observations to examine the X-ray behavior of 57 nearby stars, including some with known planets. . Most of them are giant planets like Jupiter, Saturn or Neptune, while only a handful of planets or candidate planets could be around twice as massive as Earth.
There are likely many more planets orbiting the stars in the sample, especially those similar in size to Earth, which so far remain undetected. Transit studies, which look for tiny dips in light as planets pass in front of their stars from our perspective, overlook many planets because special geometry is needed to spot them. This means that the chances of detecting transiting planets in a small sample of stars are low; only one exoplanet in the sample was detected by transits.
The other main planet detection technique involves detecting the wobble of a star induced by orbiting planets, and this technique is primarily sensitive to finding giant planets relatively close to their host stars.
“We don’t know how many Earth-like planets will be discovered in images from the next generation of telescopes, but we do know that observing time on them will be precious and extremely difficult to obtain,” said co-author Edward Schwieterman of the University of California, Riverside. “This radiological data makes it possible to refine and prioritize the list of targets and could make it possible to obtain the first image of a planet similar to Earth more quickly.”