Elias 2-24b: The Youngest Exoplanet Confirmed So Far

What about the planets? How are planets born, and how do they grow? Astronomers are trying to answer these fundamental questions by studying young planets. Finding them, however, is difficult. All the planets in our solar system formed about 4.6 billion years ago, so researchers must look beyond our solar system for more recently formed worlds. That makes exoplanets an especially valuable research target.

Why young exoplanets are difficult to find

Most of the approximately 6,000 exoplanets identified so far are also billions of years old. That does not mean young planets are rare. Older planets are simply easier to detect with common methods such as the transit method, which identifies the slight dimming of a star as a planet passes in front of it.

Newly formed exoplanets are often hidden inside disks of gas and dust—the leftover building blocks of planetary formation, known as protoplanetary disks. The challenge of locating such a young object is part of what makes the discovery of Elias 2-24b so exciting. It is the youngest exoplanet confirmed so far.

How astronomers identified Elias 2-24b

A research team led by Andrea Bernardi of Universidad Diego Portales in Chile studied seven protoplanetary disks with large gaps in their dense material. Growing planets are thought to create such gaps as they move through the surrounding disk. The team reanalyzed data gathered with coronagraphs, instruments that block the central star’s light so astronomers can detect faint reflections from nearby objects.

Scientists have known for nearly a decade that the disk surrounding the star Elias 2-24 contains a gap. The European Southern Observatory’s Very Large Telescope detected a bright spot inside that gap, leading to an ongoing debate over whether the object was truly a planet.

To investigate, the researchers compared observations collected in 2018 and 2020 at the W. M. Keck Observatory in Hawaii. The bright spot had moved in a way that showed it was not noise from an unrelated background star or an instrument. Instead, the evidence indicated that it was an object gravitationally bound to Elias 2-24—most likely a planet.

A planet less than 1 million years old

Elias 2-24b is approximately 450 light-years from Earth and orbits its star at a distance of about 55 astronomical units. One astronomical unit is the average distance between Earth and the Sun.

Researchers estimate that Elias 2-24b has a mass between 1.9 and 4.0 times that of Jupiter, although they believe its volume is likely much smaller than that of our solar system’s gas giant. Because its host star is less than 1 million years old, the exoplanet is estimated to be similarly young.

A new record for the youngest directly observed exoplanet

Before Elias 2-24b, the youngest exoplanets confirmed through direct observation were planets orbiting PDS 70 and WISPIT 2. Both are more than 5 million years old.

Elias 2-24b is therefore far younger than the previous record-holders, offering astronomers a rare opportunity to study a planet while it is still forming and to learn more about how planetary systems are born.