Last year, astronomers using the James Webb Space Telescope (JWST) made the surprising discovery of some free-floating, planetary-mass objects in the Orion Nebula that cast doubt on their ideas about planet and star formation. And now, new research has further deepened the mystery around these objects, called Jupiter-mass binary objects, or JuMBOs.
JuMBOs are not stars, but they are not actually planets either. Mark McCaughrean, senior science advisor at the European Space Agency (ESA), and his colleagues originally found the objects in the Orion Nebula. This nebula is a star birth region also known as Messier 45 and is located approximately 1,350 light-years from Earth.
Building on this observation, a team of researchers used data collected by the Karl G. Jansky Very Large Array (VLA) at the US National Science Foundation’s National Radio Astronomy Observatory to examine radio signals from some of the JuMBOs. But although McCaughrean and his colleagues found 40 pairs of JuMBOs, only one pair of these strange objects was found to emit radio waves.
“JuMBOs are already difficult to explain with star and planet formation models, and now we have a strong radio emission and it is unclear what is producing it,” said team member and National Autonomous Professor Luis F. Rodriguez. University of Mexico told Space.com.
The radio signal appeared to come from both components of “JuMBO 24”. Both components appear to have a mass of about 11 times that of Jupiter, making them the largest of their kind seen by JWST; Other components have masses between 3 and 8 times the mass of the solar system’s largest planet.
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The signal was significantly stronger than radio signals associated with objects similar to JuMBOs, also known as brown dwarfs. Brown dwarfs are objects born in the same way as stars, but they fail to accumulate enough mass in their cores to trigger the conversion of hydrogen into helium as your standard star does. This failure to initiate the process that defines a star throughout its main-sequence lifetime has led to brown dwarfs with masses between 13 and 75 times the mass of Jupiter earning the unfortunate nickname of “failed stars.”
“There are mechanisms to explain radio emissions in regular stars and brown dwarfs. For JuMBOs, we do not have a mechanism to explain this very strong radio emission,” said Rodriguez.
Neither stars nor planets
JuMBOs are hot, gaseous and relatively small objects found in pairs; This is a combination that challenges common observations of binary stars. Normally, scientists believe that only the most massive stars prefer life in binary copulations; The smaller a stellar body is, the less likely it is to form a binary partnership.
Binary stars are born when extremely dense particles in a disk of gas and dust collapse and accumulate mass, forming twin stars. While approximately 75% of large stars are binary stars, this ratio drops to 50% for sun-sized stars and 25% for the smallest stars. Chances of finding brown dwarfs in binaries close to zero. This means that JuMBOs, which are below the mass limit for brown dwarfs, should not actually exist as binaries if they form like stars.
But if JuMBOs form like stars, the sheer number of those discovered in Orion suggests that the binary frequency of stellar bodies is for some reason “jumping” at masses below that of brown dwarfs. This is something that has not yet been explained in star formation models.
So, if these planet-mass objects cannot form according to current star formation models, they are born as planets, right? Maybe so, but it’s equally difficult to explain whether the JuMBO pairs are created as planets formed from leftover material in the same disks of gas and dust that gave birth to their parent stars.
Some planets are known to be ejected from around their host star as a result of internal or external gravitational effects, such as encounters with other star systems. From there, these worlds become “rogue planets” and wander the universe without a host star, just like Orion’s JuMBOs appear to be orphans. But the process that creates these orphan planets is so violent that pairs of gravitationally bound planets must break apart.
The ejection mechanism cannot explain why Jupiter-like planets are ejected together. This means that the planetary evolution pathway can explain how JuMBOs emerged, but not why they still have their binary partners. There isn’t just one or two JuMBO matches on Orion, although that may happen in some cases. There are 42 of them.
These JuMBOs are probably not the result of a single freak launch event.
JuMBOs on Orion become even more difficult to explain given the fact that some of the binaries they inhabit are extremely widely spaced. In fact, a few JuMBOs appear to be as far away as 300 times the distance between the Earth and the Sun. Others are separated by the width of the entire solar system, meaning they are very weakly gravitationally bound.
Radio signals from JuMBO24 do not mean life
Rodriguez and his colleagues knew Orion well, having previously studied the nebula with the VLA. So when JuMBOS showed up in JWST’s infrared data, they decided to follow up by looking at archival data of radio wave observations to find the radio wave counterparts of these detections.
“We said, ‘Hey, let’s go see if any of the JuMBOs have been detected before.’ We took VLA archival data and calibrated it, finding JuMBO 24 in all three data ‘epochs’,” said Rodriguez. “We detected radio wave emissions from the largest JuMBO binary, but it is unclear why the others were not detected in radio waves.”
He explained that the team thinks other JuMBOs may also be emitting radio waves because their components are smaller than the two 11 Jupiter-mass objects in the JuMBO 24 binary.
“We’re asking the VLA for time to create deeper images in the hopes of finding maybe a few more, which will allow us to have a much better understanding of the process that creates radio waves from JuMBOs,” Rodriguez said.
These deeper observations can also reveal the speed of JuMBOs across the sky relative to the Orion Nebula. If JuMBOs are moving rapidly, this could indicate that they formed as planets around stars and were expelled from those systems, explained Rodriguez. On the other hand, he noted, if these interesting celestial bodies were nearly fixed relative to Orion, this would mean that they were created from huge clouds of gas and dust that collapsed like stars.
Both explanations would prompt us to rethink how stars and planets form and evolve within their systems.
Radio signals could also be indicative of intelligent life on Earth, but Rodriguez was quick to debunk speculation that this was also the case for JuMBO 24.
“Life is not expected on Jupiter-like objects without a solid surface, and JuMBOs would be pretty cool since there are no stars associated with them,” he said. “If JuMBOs had moons, one could speculate that life could exist in a subsurface ocean, as suspected on Europa, Ganymede, and Enceladus. But the objects in Orion are only a few million years young.” [compared to our 4.6 billion-year-old solar system]”If it exists, it probably means there wasn’t enough time in these months for life to emerge.”
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In the unlikely event that these objects or moons around them could support life, researchers chasing alien organisms on JuMBO 24 would have to explain why the radio emissions were coming from both components of this strange duo, rather than just one, Rodriguez added.
So while JuMBOs may be the astronomical discovery of the 2020s, and fascinating targets for scientists looking to better understand the formation of stars and planets, they may not be great targets for scientists investigating the possibility of life outside the solar system.
The team’s research was published in Astrophysical Journal Letters in January.