JWST discovers 40 pairs of Jupiter Mass Binary Objects - JuMBOs - in Orion Nebula
Quote:
Originally Posted by Jonathon Amos, BBC, 2 Oct 2023
Jupiter-sized "planets" free-floating in space, unconnected to any star, have been spotted by the James Webb Space Telescope (JWST).
What's intriguing about the discovery is that these objects appear to be moving in pairs. Astronomers are currently struggling to explain them.
The telescope observed about 40 pairs in a fabulously detailed new survey of the famous Orion Nebula.
They've been nicknamed Jupiter Mass Binary Objects, or "JuMBOs" for short.
Originally Posted by Jonathan O’Callaghan, New York Times
Stars in our universe form when giant clouds of dust and gas gradually coalesce under gravity. Eventually, regions of a cloud become so dense that they squeeze atoms of hydrogen together and kick-start nuclear fusion, forming the core of a star. In less dense areas, a more diminutive version of fusion — deuterium fusion — can occur in smaller objects. These are called brown dwarfs, or sometimes “failed stars.”
JuMBOs appear to be a smaller class of gaseous object. While brown dwarfs can grow to about 13 times the mass of Jupiter, the new objects can get as small as about half the planet’s mass, with temperatures of more than 1,000 degrees Fahrenheit. They are separated by about 200 times the distance between the Earth and the Sun, orbiting each other on paths that take more than 20,000 years to complete.
Were they alone in space, they might be easier to explain. But their appearance in pairs, 42 of which are seen by the Webb telescope in the Orion Nebula, is baffling. According to existing scientific models, it should not be possible to form single objects so small directly from clouds of dust and gas, let alone in pairs, Dr. Pearson said. Even if they were ejected planets — violently kicked from young stars because of gravitational forces — it is similarly unclear why there would be so many couplets.
“It’s like kicking a cup of tea across a room and having all the tea land in the teacup,” Dr. Pearson said. “And then doing that 42 times.”
The discovery is “completely unexpected,” said Matthew Bate, a professor of theoretical astrophysics at the University of Exeter in England. Many stars, perhaps even all stars, including our sun, are born as pairs. But as binary objects decrease in mass, they become less common, as their weaker gravitational attraction makes them more easily torn apart. Yet the existence of JuMBOs “implies we may be missing something about how these very low mass objects form,” Dr. Bate said.
Dr. Pearson hopes to get to the bottom of the problem by using the Webb telescope to pick apart the light from the objects, revealing what their gaseous atmospheres are made of and perhaps how they formed. Currently, he said, he can only deduce evidence of methane and water on them.
Looking for JuMBOs in other star-forming regions could help, too.
“Orion is really massive and really dense,” Dr. Pearson said. “Do we find the same thing happens in a sparse region? That might give us a clue of what formation mechanism might be happening.”
Could 2 large planets, around the size of Jupiter, both orbiting around a common star, interact gravitationally in such a way that they are both ejected from the orbit of that star and continue to orbit their common centre of gravity?
Quote:
Yes, it is possible for two large planets, roughly the size of Jupiter, orbiting a common star to interact gravitationally in such a way that they are both ejected from the orbit of the star and continue to orbit their common center of gravity. This scenario is known as "planet-planet scattering" or "planet-planet ejection" in the context of planetary dynamics.
Here's how it might happen:
1. Initial Orbit: Initially, the two Jupiter-sized planets orbit their common star in separate orbits.
2. Close Encounter: Due to their gravitational interaction, the two planets may approach each other closely in their orbits.
3. Energy Exchange: During the close encounter, they exchange energy and momentum. If the encounter is energetic enough, it can result in one or both planets gaining sufficient kinetic energy to escape the gravitational pull of the star.
4. Ejection: If one or both planets gain enough velocity from the encounter, they can be ejected from the star's gravitational influence, entering into a new trajectory that takes them into a shared orbit around their common center of gravity.
After the ejection from the star's orbit, these two planets can continue to orbit their common center of mass, effectively forming a binary planet system. The specifics of this outcome depend on the precise parameters of the encounter, including the masses, velocities, and orbital configurations of the planets.
It's worth noting that planet-planet scattering can result in various outcomes, including ejection, orbital changes, or even collisions between planets. The final configuration depends on the initial conditions and the physics of the encounter. Computer simulations are often used to study these scenarios in greater detail.
Paper "Jupiter Mass Binary Objects in the Trapezium" by Pearson et. al.
Quote:
Originally Posted by Pearson et. al.
Abstract
A key outstanding question in star and planet formation is how far the initial mass
function of stars and sub-stellar objects extends, and whether or not there is a cutoff
at the very lowest masses. Isolated objects in the planetary-mass domain below
13 Jupiter masses, where not even deuterium can fuse, are very challenging to
observe as these objects are inherently faint. Nearby star-forming regions provide
the best opportunity to search for them though: while they are young, they are
still relatively warm and luminous at infrared wavelengths. Previous surveys have
discovered a handful of such sources down to 3–5 Jupiter masses, around the
minimum mass limit established for formation via the fragmentation of molecular
clouds, but does the mass function extend further? In a new James Webb Space
Telescope near-infrared survey of the inner Orion Nebula and Trapezium Cluster,
we have discovered and characterised a sample of 540 planetary-mass candidates
with masses down to 0.6 Jupiter masses, demonstrating that there is indeed no
sharp cut-off in the mass function. Furthermore, we find that 9% of the planetarymass
objects are in wide binaries, a result that is highly unexpected and which
challenges current theories of both star and planet formation.
