There's a class of objects in the cosmos that are neither stars, nor are they quite planets.
Astronomers used the powerful James Webb Space Telescope to sleuth out some of these objects, called brown dwarfs, in a vibrant star-forming region of our galaxy called the Flame Nebula. Brown dwarfs are too small to trigger the nuclear engines in stars, but are more massive than most planets. They are unbound, free-flying objects in the universe.
And with this new research, scientists have improved our understanding of these elusive free-floating worlds and earned a good grasp of their mass limitations. Their mass can be as low as two to three times the mass of Jupiter, a gas giant over 300 times more massive than Earth. (Webb could view smaller objects, but didn't find any.)
"Webb, for the first time, has been able to probe up to and beyond that limit," Michael Meyer, an astronomer at the University of Michigan, said in a statement. "If that limit is real, there really shouldn’t be any one-Jupiter-mass objects free-floating out in our Milky Way galaxy, unless they were formed as planets and then ejected out of a planetary system.”
The research will be published in the peer-reviewed science journal The Astrophysical Journal Letters.
The Webb telescope image below shows what are likely three brown dwarfs in the Flame Nebula, which teems with hot, young forming stars (protostars). Previously, researchers spent 10 years peering at the Flame Nebula, but couldn't find these objects in the dense areas of the star-forming region. They aren't easy to find: Lower-mass objects like brown dwarfs are extremely faint to telescopes, as they lack the heat and size of stars. But the Webb telescope, which views faint infrared light (detected as heat), revealed these deep space objects.
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Stars and brown dwarfs alike are created in dense clouds of gases like hydrogen. These clouds "fragment" apart, and inside each of these objects take shape under forces dominated by gravity, temperature, and pressure. Stars form when a contracting object's core is massive enough to stoke nuclear fusion and become an energy-producing, luminous star. Brown dwarfs are too small to create this fusion, and become solitary objects in the cosmos, without signs of a surrounding solar system.
These new observations, and those forthcoming, will help researchers understand objects in the cosmos that could be rogue planets or small brown dwarfs. “There's a big overlap between the things that could be planets and the things that are very, very low mass brown dwarfs," Meyer explained. "And that's our job in the next five years: to figure out which is which and why."
The Webb telescope's powerful abilities
The Webb telescope — a scientific collaboration between NASA, ESA, and the Canadian Space Agency — is designed to peer into the deepest cosmos and reveal new insights about the early universe. It's also examining intriguing planets in our galaxy, along with the planets and moons in our solar system.
Here's how Webb is achieving unparalleled feats, and may for years to come:
- Giant mirror: Webb's mirror, which captures light, is over 21 feet across. That's over two-and-a-half times larger than the Hubble Space Telescope's mirror, meaning Webb has six times the light-collecting area. Capturing more light allows Webb to see more distant, ancient objects. The telescope is peering at stars and galaxies that formed over 13 billion years ago, just a few hundred million years after the Big Bang. "We're going to see the very first stars and galaxies that ever formed," Jean Creighton, an astronomer and the director of the Manfred Olson Planetarium at the University of Wisconsin–Milwaukee, told Mashable in 2021.
- Infrared view: Unlike Hubble, which largely views light that's visible to us, Webb is primarily an infrared telescope, meaning it views light in the infrared spectrum. This allows us to see far more of the universe. Infrared has longer wavelengths than visible light, so the light waves more efficiently slip through cosmic clouds; the light doesn't as often collide with and get scattered by these densely packed particles. Ultimately, Webb's infrared eyesight can penetrate places Hubble can't.
"It lifts the veil," said Creighton.
- Peering into distant exoplanets: The Webb telescope carries specialized equipment called spectrographs that will revolutionize our understanding of these far-off worlds. The instruments can decipher what molecules (such as water, carbon dioxide, and methane) exist in the atmospheres of distant exoplanets — be they gas giants or smaller rocky worlds. Webb looks at exoplanets in the Milky Way galaxy. Who knows what we'll find?
"We might learn things we never thought about," Mercedes López-Morales, an exoplanet researcher and astrophysicist at the Center for Astrophysics-Harvard & Smithsonian, previously told Mashable.
