The universe is a vast, strange place with many unique objects. Between the space of stars, planets can be found floating without a parent, running rogue throughout eternity. These rogue planets, also known as free-floating planetary-mass objects (FFPMOs), are such celestial bodies that do not orbit a star. Unlike planets within a solar system, these objects drift through space independently yet also blur the boundary of what could be considered a star or a planet. It’s not fully understood when a planet can become large enough to undergo thermonuclear fusion. We know that Jupiter is a very massive object, but not massive enough to become a star in its own right. How much larger would Jupiter need to be?
A recent discovery by James Webb Space Telescope provides valuable insights into the processes of planet formation and the dynamics of planetary systems. Rogue planets can tell us stories of great gravitational interactions in the early dynamics of the formation of solar systems, when many planets existed. It’s even possible our own solar system was responsible for sending its own rogue planets out into the cosmos, as it’s thought many planets existed before the traditional eight we know today, perhaps the most famous being Theia, the planet that impacted our Moon. Understanding rogue planets helps scientists explore the range of planetary types and the conditions under which they form while also providing information about the process of stellar formation and how planetary and stellar formation differ.
James Webb Space Telescope (JWST)’s Discovery and Implications
The James Webb Space Telescope, launched with the mission to explore the universe’s earliest galaxies and star systems, brings unprecedented capabilities in infrared astronomy. Equipped with advanced instruments such as the Near Infrared Imager and Slitless Spectrograph (NIRISS), JWST enables detailed observations of distant and faint objects. Its mission is crucial for expanding our knowledge of the cosmos, including the discovery of previously unseen celestial phenomena, such as these rogue planets.
Astronomers from universities like John Hopkins, Cornell, University of Montreal, and others partnered to look for rogue worlds in NGC 1333 - a relatively young star cluster in the Perseus molecular cloud complex located roughly 967 light-years away from our solar system. As mentioned, rogue planets are likely to be found near young solar systems, making NGC 1333 an ideal target for finding new and unique rogue planets. NGC 1333 was already known to have a high presence of protostars and brown dwarfs, telling astronomers that star formation is active in this region. Peering into this nebula, astronomers discovered six new planetary mass candidates, ranging from a mass between 5 and 15 masses of Jupiter. Most notably, one object appeared to have an “infrared excess” - meaning that it has a clear sign of a planetary disk.
The worlds discovered by JWST suggest that these rogue planets are among the smallest rogue planets ever discovered and blur the border even further between a massive planet and a small star. This discovery will help aid in the question of how small an object can be to undergo nuclear fusion. These observations also help confirm that the universe produces planetary mass objects in at least two unique ways - either through a collapse of dust and gas, as it was thought our own Sun formed, or in the disk around young stars as Jupiter and Saturn formed. The presence of the dusty disk around the world with an infrared excess shows that it definitely formed like a star, and might mean it has its own “Micro” solar system.
Image Credit: ESA/Webb, NASA & CSA, A. Scholz, K. Muzic, A. Langeveld, R. Jayawardhana
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