The Orion Nebula, M42, is the largest stellar nursery close to Earth. Within this massive complex some 1300 light years away, the James Webb Space Telescope has unveiled hundreds of Jupiter-sized rogue planets roaming freely here.
Rogue planets are free-floating planets that do not orbit a star. They are thought to form when planets are ejected from their star systems during close encounters with other planets or stars. Alternatively, they could form directly from the gas and dust in a star-forming region, without ever orbiting a star.
The Orion Nebula is an amazing place. It is a region of space that spans more than a full square degree in the sky, and the densest star cluster within it, the Trapezium Cluster, contains approximately 2800 stars all squished within 20 light-years of one another.
Under a dark sky, with no light pollution, one can actually see the nebula complex in the blade of the sword hanging from Orion’s Belt. It is without doubt one of the most observed objects in our night sky. Observations of this nebula can be traced all the way back to the 1880’s.
It has long been understood that the Orion Nebula complex was creating newly-formed stars, including many bright, massive stars that are destined to be short-lived. There are also collapsing clouds of molecular gas, dust-shrouded protostars with planet-forming disks around them, and evaporating gaseous globules, being boiled away by the radiation of nearby, newborn stars.
So it was with great anticipation and astonishment that when JWST took a look at the nebula, astronomers found more than 500 Jupiter-mass planet-like objects freely floating within the surveyed region, with a whopping 9% of them in binary systems, making them what astronomers are calling JuMBOs: Jupiter-Mass Binary Objects.
Nowhere else have astronomers found so many rogue planets found in such large numbers in close proximity. This discovery suggests that free-floating planets are much more common than previously thought.
JWST was able to detect these planets because for the first time, we have an incredibly powerful telescope that, because it sees in the infrared part of the spectrum, can actually pierce the veil of dust and gas that make up most of the nebula to reveal what lies inside. The giant space telescope centered its gaze on the center of the nebula, where things are most dense: the Trapezium Cluster, home to some of the youngest stars known: stars whose median age is only about 300,000 years. For most of human history, the majority of the Trapezium cluster has been obscured by dust.
Not any longer, the infrared cameras on JWST cataloged about 540 Jupiter-mass objects, ranging from about 0.6 Jupiter masses, roughly the lower limit of what JWST can identify, all the way up to around 13 Jupiter masses, or the approximate line between the most massive planet and the least massive brown dwarf star.
The discovery of these free-floating planets raises new questions about how planets form and evolve. It is unclear how these planets can form without a star to provide them with energy and heat. It’s possible that these planets are the result of failed stellar systems that boiled away much of the material needed to create a planetary system, leaving behind these gas giants.
Astronomers are continuing to study the JWST data to learn more about these free-floating planets. They are striving to make more observations of this region in the infrared in the hope to determine how they form, how long they can survive, and whether they have the potential to harbor life.