Barnard's Star, just six light-years away, has been a challenging target due to its jittery nature and the difficulty of distinguishing genuine planetary signatures from stellar noise. Using the radial velocity method, researchers measure the tiny shifts in starlight caused by gravitational tugs from orbiting planets. However, when the planets are as lightweight as these, each only about 20 to 33 percent the mass of Earth, the gravitational effect becomes vanishingly faint.
To complicate matters further, stellar activity such as quakes and flickers often obscures the already faint signals. The detected velocity changes range from only 0.2 to 0.5 meters per second, while the background stellar noise is nearly tenfold stronger, at about 2 meters per second. Isolating such faint planetary signals required new levels of precision and data processing.
The research team tackled this by building sophisticated models to simulate the star's natural variability. By subtracting the simulated noise from the raw observations, they were able to filter out the background and unveil the planetary patterns underneath.
Observations from the MAROON-X spectrograph on the Gemini Telescope in Hawaii confirmed the presence of the previously suggested planet "b" and uncovered three new planetary companions, designated c, d, and e. Earlier hints of planet b came from ESPRESSO, an ultra-sensitive instrument on the Very Large Telescope in Chile. Together, these instruments provided a clearer, more complete picture of this four-planet system.
Despite their significance, these planets are unlikely to host life due to their tight orbits around their star. The innermost planet completes an orbit in just over two days, while the outermost wraps up its circuit in under seven days. These rapid revolutions suggest scorching surface conditions far from the habitable zone.
Nevertheless, the find energizes the broader hunt for Earth-like worlds. Detecting such small, rocky planets remains a technical feat, but continued advances in radial velocity techniques could illuminate many more such candidates. These improvements may eventually help astronomers zero in on truly habitable environments in our galactic neighborhood.
Barnard's Star itself was discovered in 1916 by astronomer Edward Emerson Barnard, a pioneer in photographic studies of the cosmos.
Research Report:Four Sub-Earth Planets Orbiting Barnard's Star from MAROON-X and ESPRESSO
Related Links
NASA Exoplanet Archive
Lands Beyond Beyond - extra solar planets - news and science
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