The solar system considered habitable is dangerous

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A new planet earth is further away than thought! The discovered solar system is not safe from stellar flares as was originally believed.

A nearby star, the host of two (and possibly three) planets, was initially thought to be quiet and rather “dull.” These attributes are sought after because they create a safe environment for your planets, especially those that may be in what scientists call “the habitable zone” where liquid water could exist on their surfaces and life could be possible.

But astronomers at Arizona State University have announced that this nearby star turns out not to be so tame after all.

This star, called GJ 887, is one of the brightest M stars in the sky, these are low-mass red stars that outnumber stars like our sun more than ten times, and the vast majority of the planets in our galaxy are orbit.

GJ 887 had initially been noted for the seemingly smooth space environment it provides for its recently discovered planets. In monitoring by NASA’s Transiting Exoplanet Study Satellite (TESS), a mission to search for planets outside our solar system, the star curiously exhibited no detectable flares during 27 days of continuous observations.

And the absence of flares is a quality that favors the survival of the atmospheres on the planets that orbit the star and, therefore, the potential life on those planets.

New “planet Earth” in imminent danger

But ASU astronomers Parke Loyd and Evgenya Shkolnik from ASU’s School of Earth and Space Exploration had their doubts that GJ 887 was that quiet. Digging into archival data from the Hubble Space Telescope, they found that GJ 887 actually turns on every hour.

How did they detect this difference? Using far ultraviolet light, Loyd, Shkolnik and their collaborators were able to see huge peaks of brightness caused by the star flares.

Their findings were recently published in a Research Note from the American Astronomical Society, with co-authors from the University of Colorado, Boulder, and the Naval Research Laboratory in Washington, D.C.

M stars, potentially habitable

Because there are so many, M-stars like GJ 887 are a key player in humanity’s quest to understand where Earth fits in the vast collection of planets in the universe and in the search for life on other planets.

“If the genesis of life on a planet is more or less a roll of the dice, then M-stars are rolling those dice much more than any other type of star,” Loyd explained.

But there is a catch. M stars tend to dot their planets with sparkles. They can also be two-faced and appear calm in visible light, such as that observed by the TESS mission. In reality, they can be riddled with flares that are clearly evident in ultraviolet light, which has photons (light particles) of much higher energy than visible light.

And each flare has the potential to bombard the star’s planets with a magnetic storm and a shower of fast-moving particles, increasing the chances that the atmospheres of the GJ 887 planets have long since eroded.

“It is fascinating to learn that observing stars with normal optical light (as the TESS mission does) does not come close to telling the whole story,” Shkolnik said. “The harmful radiation environment of these planets can only be fully understood with ultraviolet observations, such as those from the Hubble Space Telescope.”

While ultraviolet monitoring of M stars is valuable, the resources astronomers have to devote to such observations are currently limited. Fortunately, there are plans in the works for missions that can help meet this need, including an ASU-led CubeSat mission called Star-Planet Activity Research CubeSat (SPARCS), of which Shkolnik is the principal investigator.

This mission will provide astronomers with the observing time they need to capture ultraviolet flares from M stars and measure how often they occur, ultimately leading to a greater understanding of the stars and planets in our galaxy.

“The ultraviolet emission from a star is really a critical, albeit still missing, piece of the puzzle for our understanding of the planets’ atmospheres and their habitability,” Shkolnik said.


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