Astronomers have announced the discovery of three new exoplanets orbiting a youthful counterpart to our Sun, located within the vast Pisces-Eridanus stellar stream spanning over 1,300 light-years.
Stellar streams emerge when the Milky Way's gravity disrupts star clusters or dwarf galaxies, sending individual stars drifting along their original paths and forming elongated, dispersing groups.
Two years ago, researchers from the University of Vienna identified the Pisces-Eridanus stream using data from the European Space Agency's Gaia mission. This stream stretches across approximately 1,300 light-years, encompassing 14 constellations.
Shortly after, scientists at Columbia University in New York analyzed stars within it using NASA's Transiting Exoplanet Survey Satellite (TESS). Young stars rotate faster than older ones; by measuring rotation periods, the team confirmed these stars formed roughly 120 million years ago.
Among them, TOI 451—located just 400 light-years from Earth—hosts three planets, detected by TESS via the transit method. This technique spots periodic dips in starlight as planets pass in front of their host from our vantage point.
The innermost, TOI 451 b, completes an orbit every 1.9 days. It's 1.9 times Earth's size and 2–12 times more massive. TOI 451 c orbits every 9.2 days, measuring three times Earth's radius and 3–16 times its mass. The outermost, TOI 451 d, takes 16 days per orbit, is four times Earth's size, and has 4–19 Earth masses.
All three are intensely hot: even the farthest orbits three times closer to its star than Mercury does to the Sun. Equilibrium temperatures range from about 1,200°C for the inner planet to around 450°C for the outer one.
Despite their hostility, the system's youth and proximity make it ideal for probing planetary atmosphere evolution. Large worlds like these should retain substantial atmospheres despite extreme heat. By analyzing starlight filtering through these atmospheres, scientists can determine chemical compositions—a task for which the James Webb Space Telescope, launching in October, is well-suited.
Details appear in The Astronomical Journal.
