This alien planet's hotspot is in the wrong place and astronomers have no idea why

In the catalogue of strange worlds beyond our solar system, hot Jupiters occupy a special category of the bizarre. These are gas giants the size of Jupiter or larger that orbit their host stars in a matter of days — so close that their surface temperatures can exceed thousands of degrees. Astronomers thought they had a fairly good handle on how these planets behave. Then they looked more closely at CoRoT-2 b, and the rulebook turned out to be wrong.

A Planet That Should Not Exist As It Does

CoRoT-2 b sits 696 light-years from Earth. It is a hulking world — 3.5 times the mass of Jupiter and 1.5 times its size — that races around its host star in just 41 hours, completing a full orbit in under two Earth days. By the standards of hot Jupiters, this makes it an extreme but not unusual example of its type. What makes CoRoT-2 b extraordinary is what its atmosphere is doing. On every other hot Jupiter astronomers have studied, the planet's hottest point — its thermal hotspot — is displaced slightly in the direction the planet orbits. Winds in the upper atmosphere carry heat from the blazing dayside in the direction of the planet's motion, and the hotspot follows. On CoRoT-2 b, the hotspot is displaced in the opposite direction entirely. It is, by every model astronomers have, in the wrong place.

What A Hot Jupiter Should Look Like

To understand why this is so puzzling, it helps to understand what makes hot Jupiters tick. Because they orbit so close to their stars, most hot Jupiters are tidally locked — the same hemisphere always faces the star, just as the same side of the Moon always faces Earth. The dayside bakes under constant stellar radiation while the nightside stays cold. Powerful atmospheric winds, driven by this extreme temperature difference, flow from the hot dayside to the cooler nightside. These winds drag the peak heat — the hotspot — slightly ahead of the subsolar point in the direction of the planet's orbit. This pattern has been observed consistently across dozens of hot Jupiters. CoRoT-2 b was supposed to follow the same pattern. It does not.

The Very Large Telescope Reveals The Clue

New observations from the Very Large Telescope at the European Southern Observatory have given astronomers their best clue yet about what is happening on CoRoT-2 b. The data reveals that this hot Jupiter is rotating unusually slowly — far slower than any other hot Jupiter yet studied. One full rotation of CoRoT-2 b takes approximately three Earth days. But the planet's year — the time it takes to complete one orbit of its star — is just 1.7 days. In other words, CoRoT-2 b orbits its star twice before it has finished spinning once on its own axis. This is the opposite of what most hot Jupiters do, and it appears to be the key to why the hotspot ends up in the wrong place. The findings were presented at the 248th meeting of the American Astronomical Society in Pasadena, California, in June 2026.

Why Slow Rotation Changes Everything

In a standard tidally locked hot Jupiter, the winds flowing from the dayside to the nightside are what determine where the hotspot sits. But when a planet is rotating more slowly than it orbits, the atmospheric dynamics change in fundamental ways. The Coriolis forces that shape wind patterns — the same forces that create cyclones and trade winds on Earth — behave differently when the planet's rotation rate is out of step with its orbital speed. Instead of atmospheric winds carrying heat forward in the direction of the orbit, they can be deflected backward, dragging the hotspot in the opposite direction. This is the leading hypothesis that researchers have settled on to explain CoRoT-2 b's backwards atmosphere — and it is unlike anything observed on another planet in or out of our solar system.

A Window Into Planetary Diversity

The significance of CoRoT-2 b goes beyond one anomalous planet. Hot Jupiters were once considered among the best-understood class of exoplanets precisely because their extreme properties made them easy to observe and their behaviour seemed predictable. CoRoT-2 b suggests that even within this well-studied category, the range of possible atmospheric behaviours is wider than models have accounted for. If slow rotation can produce a backwards hotspot on one hot Jupiter, there may be other worlds with similarly unusual rotation states that have been misinterpreted or overlooked in existing data. The researchers behind this work have described the pleasure of studying planetary exceptions — finding worlds that do not fit the standard picture and working out why. CoRoT-2 b, it turns out, is one of the most instructive exceptions yet found.

What Comes Next

Follow-up observations of CoRoT-2 b are expected to further probe the planet's atmospheric structure and test the slow-rotation hypothesis against competing explanations. The Very Large Telescope's spectroscopic capabilities allow researchers to map temperature distributions across the planet's visible disc, building a more detailed picture of where heat is concentrated and how it moves. Whether the slow rotation explanation holds up or gives way to something more surprising, CoRoT-2 b has already done what the best scientific anomalies do: it has forced astronomers to look at a class of well-studied objects and ask whether they fully understand them. The answer, at least for now, appears to be no.