Cosmic Hide-and-Seek: Webb Spots a Planet Near a Neighboring Star ✛

Original: "Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of $$\alpha$$ Cen A. I. Observations, Orbital and Physical Properties, and Exozodi Upper Limits"

arXiv:2508.03814 · 2025-08-05 · CC BY 4.0 · 1 min

Exoplanets Stellar

The [tag:jwst]James Webb Space Telescope[/tag] briefly caught a signal from object S1 — a possible [tag:exoplanet]planet[/tag] around Alpha Centauri A, which then immediately vanished.

The nearest Sun-like star, Alpha Centauri A, shines just four light-years away. The James Webb Space Telescope stared at it, blocking the star with a coronagraph — like holding a hand up to spot the Sun’s satellites. This is how it searched for planets and dust. It found almost no dust: remarkably clean, as if someone swept away the cosmic debris. But in August 2024, a dot called S1 appeared: an object the size of Jupiter, but surprisingly not icy — around –20°C (based on brightness). Then it vanished. Probably, its orbit is so stretched that it hides behind the star every 2–3 years, plunging from cold to warmth. If S1 is the same planet spotted in 2019 as C1, this is one of the lightest worlds directly imaged around a Sun-like star: 90–150 Earth masses.

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The same system has Proxima b — an Earth-sized planet where a year lasts just 11 days.

In ‘Avatar,’ the planet Polyphemus and its moon Pandora orbit Alpha Centauri A — our searches make that world a little more real.

T_{\mathrm{eq}} = T_\star \left(\frac{1-A_B}{4f}\right)^{1/4} \sqrt{\frac{R_\star}{d}} (1-e^2)^{-1/8}

The planet's temperature is determined by the star's temperature and radius, distance, albedo, and orbital eccentricity

R_{\mathrm{H}} \approx a(1-e) \sqrt[3]{\frac{m_p}{3(m_*+m_p)}}

Shows the distance from the planet at which its gravity dominates over the star's attraction

Scientists

Christian Doppler D. B. McLaughlin Didier Queloz Michel Mayor R. A. Rossiter David Charbonneau

Concepts

trappist 1 hot jupiter atmospheres james webb space telescope mercury super earth earth radius exoplanets around red dwarfs andromeda galaxy neptune asteroid belt sun like star sub neptune parker solar probe miri habitable worlds observatory roman red dwarf planets terrestrial exoplanet solar radius tess

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Cosmic Hide-and-Seek: Webb Spots a Planet Near a Neighboring Star ✛