'Warm Jupiter' spotted in a four billion-year-old star cluster

In a cosmic neighborhood, a team has uncovered a “warm Jupiter” planet. This discovery challenges our understanding of planet formation, hinting at the complex ways these giant worlds might come to be.

A team led by Luis Thomas of the University Observatory Munich has described a new exoplanet (a planet outside of our solar system) orbiting a star within the ancient star cluster Messier 67. This gas giant, designated S1429 b, belongs to a class known as warm Jupiters.

Messier 67 and warm Jupiter

Messier 67, nicknamed the King Cobra Cluster, is a grand old dame among star clusters. Estimated to be over 4 billion years old, it’s one of the most ancient and well-studied open clusters in our galaxy.

This incredible age makes it a fascinating window into how stars evolve and how star clusters change over vast stretches of time. Interestingly, the cluster is about the same age as our Sun.

This offers scientists a chance to study a stellar environment that might resemble our own solar system in its youth. Astronomers wonder, could planets – even those potentially capable of supporting life – exist in a place like M67? That possibility makes it a prime target for hunting exoplanets.

The team’s “Search for Giant Planets in M67” survey is dedicated to answering those questions.

Hot and Warm Jupiter

Hot Jupiters are gas giants, like the Jupiter in our solar system, but they orbit incredibly close to their stars. This makes them scorching hot – way hotter than any planet in our solar system.

Warm Jupiters, like S1429 b, are a bit less extreme. They’re still gas giants, but they orbit their stars farther away than hot Jupiters.

This means they’re warm, but not blazing hot. They also have longer orbits than hot Jupiters, putting them somewhere in between the super-close hot worlds and planets further out, like Jupiter in our solar system.

S1429 b

“Between December 2019 and March 2022, we continued the observations of 11 stars in M67 with the Habitable Planet Finder spectrograph (HPF). We included six stars that showed potential long-term RV variations and five stars at the turn-off point of M67 which had no previously published data,” explained the researchers.

The team’s efforts paid off. Warm Jupiter S1429 b is about twice as massive as Jupiter. It completes an orbit around its host star every 77.48 days, at a relatively close distance.

This proximity results in a warm equilibrium temperature of about 683 Kelvin. “This is the sixth planet discovered in Messier 67… they are distributed over different evolutionary stages,” noted the researchers.

Warm Jupiter research insights

The presence of a warm Jupiter in this ancient cluster raises questions about planet formation and migration. Did this planet form later than its neighboring stars? Did it wander in from elsewhere?

As scientists uncover more exoplanets, they refine their understanding of how and where planets form, pushing the boundaries of our knowledge about the universe.

The discovery of a warm Jupiters implies that there is a whole range of giant planets out there, and they don’t all form in the ways we initially expected.

The study is published as a pre-print in the journal ArXiv.org.

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