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New research shows gaia could detect Earth-like planets up to 30 light-years away

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In 2013, the European Space Agency (ESA) launched the Gaia mission with a remarkable objective: to map over a billion stars within our Milky Way galaxy. Despite its monumental data collection, Gaia often remains in the shadows, not capturing much attention on its own.

But the tides might be turning.

Gaia’s primary tool is astrometry, a precise science that measures the positions, distances, and motions of stars. It’s so sensitive that it can even detect the subtle wobbles induced by planets orbiting massive stars. In 2021, Gaia achieved a significant milestone by detecting its first two transiting exoplanets. It is anticipated to discover thousands of Jupiter-sized exoplanets beyond our solar system.

But recent research has pushed the boundaries even further. This study suggests that Gaia could potentially spot Earth-like planets up to 30 light-years away.

The research paper, titled “The Possibility of Detecting our Solar System Through Astrometry,” authored solely by Dong-Hong Wu from the Department of Physics at Anhui Normal University, China, delves into this intriguing possibility.

Most astronomers hunt for exoplanets using the transit method, where spacecraft like TESS monitor sections of the sky, observing multiple stars at once. When a planet passes in front of a star from our perspective, it creates a noticeable dip in the star’s brightness, which TESS can detect. Repeated dips in brightness signal the presence of a planet.

However, Gaia relies on astrometry, offering a unique advantage. It excels at accurately determining the orbital characteristics of exoplanets. This doesn’t diminish the value of other detection methods; they are undoubtedly crucial. As the paper’s author clarifies, “Neither the transit nor radial velocity method provides complete physical parameters of one planet, and both methods prefer to detect planets close to the central star. On the contrary, the astrometry method can provide a three-dimensional characterization of the orbit of one planet and has the advantage of detecting planets far away from the host star.” The strengths of astrometry are evident.

Considering the possibility of technologically advanced extraterrestrial civilizations, the paper raises an intriguing question: If these civilizations possess astrometry technology on par with or superior to Gaia’s, could they detect planets in our solar system, including Earth?

Astrometric precision is measured in microarcseconds, and this precision diminishes with distance. According to the ESA, Gaia can pinpoint a star’s position with an incredible accuracy of 24 microarcseconds, even for objects 4,000 times fainter than what the naked eye can see. To put it in perspective, this is akin to measuring the thickness of a human hair from a distance of 1,000 kilometers. However, Wu’s work is founded on the expectation of even more advanced astrometry, the kind we are likely to develop in the near future.

“If astrometry precision reaches or exceeds 10 microarcseconds,” as the paper proposes, “all 8,707 stars located within 30 parsecs of our solar system could potentially detect the four giant planets within 100 years.”

This forms the core of Wu’s research. The 30-parsecs (approximately 100 light-years) region encompasses nearly 9,000 stars. If an extraterrestrial intelligence from one of these stars possesses astrometry capabilities of this caliber, they could potentially observe Jupiter, Saturn, Uranus, and Neptune in our solar system. The only caveat is that they would need to observe our solar system for nearly a century to ensure a clear signal.

This figure from the research shows how long it would take for an ETI with advanced astrometry to detect our solar system’s four giant planets. “We find that all the four giants in our solar system could be detected and well-characterized as long as they are observed for at least 90 years with SNR > 1,” the author writes. Credit: Wu 2023

Within a 100-light-year radius from our Sun, the Gaia Catalog of Nearby Stars lists a total of 8,707 stars. These stars hold potential significance because any Extraterrestrial Intelligence (ETI) residing around them could potentially detect the four gas giants in our solar system, provided their astrometry precision is within ten microarcseconds. However, precision, expressed in microarcseconds, is the critical factor here, as a larger observational error significantly reduces the number of stars within range.

Dong-Hong Wu, the author of this research, points out that if the observational error reaches 100 microarcseconds, only 183 nearby stars could detect all four gas giants. Nonetheless, all of them could spot Jupiter within a decade. Detecting Jupiter from a distance is noteworthy because it might indicate a protective role this massive planet plays by deflecting potentially hazardous asteroids and comets away from the inner solar system.

From an ETI perspective, finding gas giants in the outer regions of a solar system could signal the presence of rocky planets closer to the star. This might pique their curiosity and prompt further investigation.

Now, let’s turn the tables and consider whether ETIs could detect Earth using astrometry. Once again, it hinges on achieving microarcsecond accuracy. Wu suggests that over 300 stars within ten parsecs of our solar system could detect Earth if they attain an astrometry precision of 0.3 microarcseconds. Our current technological constraints prevent us from achieving such precision, but the capabilities of an ETI civilization remain an intriguing unknown.

Now, consider our own technological advancements. The European Space Agency (ESA) is already contemplating Gaia’s successor, GaiaNIR, designed to expand Gaia’s search into the infrared spectrum. GaiaNIR could revisit Gaia’s targets, further enhancing the accuracy of Gaia’s existing data, and potentially detecting long-period exoplanets—those with lengthy orbits that are challenging to identify using the transit method. This technology could put us in the position to discover Earth-sized planets within a 10-parsec radius in the future.

Astrometry, with its non-reliance on celestial alignments like the transit method, holds promise. It can monitor a star from any angle, detecting planet-induced wobbles. The question remains: How technologically advanced would ETIs need to be to detect Earth using astrometry? Are there any ETIs within 10 parsecs, 30 parsecs, or even 100 parsecs? The existence of ETIs remains an intriguing, unanswered question. However, our appetite for Earth-sized exoplanets continues to grow, and Gaia’s potential in satisfying it could elevate this mission to grab more headlines and attention, just as other missions regularly do.

Source: Universe Today

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