Astronomers Capture Rare Image of Baby Planet Forming in Real Time
A team of astronomers has made a groundbreaking discovery by capturing a rare image of a protoplanet, known as AB Aurigae b, actively forming around a young star. This giant protoplanet, approximately four times the mass of Jupiter, is located about 93 astronomical units from its star, which is roughly three times the distance between the Sun and Neptune. The observations provide a unique glimpse into the chaotic processes of planetary formation.
Protoplanets are celestial bodies still developing within the gas and dust disks surrounding young stars. They are crucial to understanding how the planets we know today come into existence. Unlike established planets, protoplanets remain embedded in their birth environments, feeding on surrounding material through their own circumplanetary disks.
Rare Insights into Planetary Formation
Using the Very Large Telescope equipped with the MUSE spectrograph in Chile, researchers from the Astrobiology Center in Japan detected the emission of hydrogen alpha lines from AB Aurigae b. This hydrogen light originates from hot gas spiraling into the planet as it consumes material from its protoplanetary disk.
The hydrogen emission from AB Aurigae b exhibits a unique “inverse P Cygni profile,” indicating that gas is falling toward the planet rather than being expelled. This pattern is typically seen in young stars undergoing rapid accretion but has now been directly observed in a protoplanet for the first time. Specifically, the emission appears slightly blue-shifted, indicating gas moving toward observers at speeds of about 100 kilometres per second, while absorption features indicate material moving away at approximately 75 kilometres per second.
This discovery is particularly significant because, unlike other young planets that have been directly imaged, which orbit in cleared gaps in their disks, AB Aurigae b remains surrounded by its birth disk. This unique position allows astronomers to observe the feeding process as the planet accumulates mass from its environment.
Challenging Existing Planet Formation Models
The system’s young age, estimated at around 2 million years, means researchers are witnessing planetary formation in its earliest stages. Observations of AB Aurigae b challenge established models of planet formation. Its distant location suggests that the planet likely formed through a process where dense regions of the disk rapidly collapse under their own gravity, rather than the core accretion method previously thought to be responsible for the formation of Jupiter and Saturn.
The detection of hydrogen emission provides direct evidence of mass accretion onto a protoplanet still within the disk from which it formed. This finding offers crucial insights into how gas giant planets grow during their formation phase. The circumplanetary disk surrounding AB Aurigae b acts as a feeding mechanism, channeling material from the larger protoplanetary disk onto the developing planet.
As researchers continue to analyze this discovery, future observations will determine how much of the detected emission originates from the planet itself versus reprocessed light from the surrounding disk. They will also explore whether similar accretion signatures can be found around other young stars, marking the beginning of a new era in the study of planetary formation.
This significant discovery highlights the evolving field of astronomy and the potential for further groundbreaking revelations in understanding the birth of planets in our universe.
