SPACE/COSMOS TOO
New study reveals how rogue planetary-mass objects form in young star clusters
Chinese Academy of Sciences Headquarters
image:
This one-million-year-old star-forming region contains thousands of new stars and hundreds of planetary mass objects floating freely in the nebula, not orbiting stars.
view moreCredit: NASA, ESA, CSA /M. McCaughrean, S. Pearson
A groundbreaking study published in Science Advances sheds new light on the mysterious origins of free-floating planetary-mass objects (PMOs)—celestial bodies with masses between stars and planets.
Led by Dr. DENG Hongping of the Shanghai Astronomical Observatory of the Chinese Academy of Sciences, an international team of astronomers used advanced simulations to uncover a novel formation process for these enigmatic objects. The research suggests that PMOs can form directly through violent interactions between circumstellar disks in young star clusters.
The Mystery of Rogue Planetary-Mass Objects
PMOs are cosmic nomads, drifting freely through space, unbound to any star. The mass of these objects is less than 13 times that of Jupiter. They are often observed in young star clusters like the Trapezium Cluster in Orion. While their existence is well-documented, their origin has long puzzled scientists. Previous theories proposed that PMOs could be failed stars or planets ejected from their solar systems. However, these models fail to explain the large number of PMOs, their frequent binary pairings, and their synchronized motion with stars within clusters.
"PMOs don't fit neatly into existing categories of stars or planets," said Dr. DENG, corresponding author of the study. "Our simulations show they likely form through a completely different process—one tied to the chaotic dynamics of young star clusters."
A Cosmic Tug-of-War: How Disks Collide to Create PMOs
Using high-resolution hydrodynamic simulations, the researchers recreated close encounters between two circumstellar disks—rotating annuli of gas and dust surrounding young stars. When these disks collide at speeds of 2–3 km/s and distances of 300–400 astronomical units (AU), their gravitational interactions stretch and compress gas into elongated "tidal bridges."
These tidal bridges eventually collapse into dense filaments, which further fragment into compact cores. When these filaments reach a critical mass, they produce PMOs with masses of about ten times that of Jupiter. The simulations also revealed that up to 14% of PMOs form in pairs or triplets, with 7–15 AU separations, explaining the high rate of PMO binaries in some clusters. Frequent disk encounters in dense environments like the Trapezium Cluster could generate hundreds of PMOs, explaining the observed overabundance.
Why PMOs Are Unique
PMOs are distinct in their formation. Unlike ejected planets, they move in sync with the stars in their host clusters and inherit material from the outer regions of circumstellar disks. This results in a unique composition, with PMOs reflecting the metal-poor outskirts of these disks, where heavy elements are scarce. Many PMOs also retain gas disks up to 200 AU in diameter, suggesting the potential for lunar or even planetary formation around these rogue objects.
"This discovery partly reshapes how we view cosmic diversity," said co-author Prof. Lucio Mayer from the University of Zurich, "PMOs may represent a third class of objects, born not from the raw material of star-forming clouds or via planet-building processes, but rather from the gravitational chaos of disk collisions."
Looking Ahead
The team, including researchers from the University of Hong Kong, the Shanghai Astronomical Observatory, the University of California Santa Cruz, and the University of Zurich, plan further studies to explore the chemical makeup and disk structures of PMOs. Upcoming research on PMOs in various clusters will consolidate the theory of their formation and population properties.
The formation of binary PMOs via circumstellar disk encounters.
Credit
DENG Hongping
Journal
Science Advances
Method of Research
Meta-analysis
Subject of Research
Not applicable
Article Title
Formation of free-floating planetary mass objects via circumstellar disk encounters
Article Publication Date
26-Feb-2025
The future of telescope lenses is flar
Utah engineers create first flat telescope lens that can capture color while detecting light from faraway stars
University of Utah
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Utah researchers demonstrated the capabilities of their flat lens with test images of the sun and moon.
view moreCredit: Menon Lab, University of Utah
For centuries, lenses have worked the same way: curved glass or plastic bending light to bring images into focus. But traditional lenses have a major drawback—the more powerful they need to be, the bulkier and heavier they become. Scientists have long searched for a way to reduce the weight of lenses without sacrificing functionality. And while some slimmer alternatives exist, they tend to be limited in their capacity and are generally challenging and expensive to make.
New research from University of Utah engineering professor Rajesh Menon and colleagues at the Price College of Engineering offers a promising solution applicable to telescopes and astrophotography: a large aperture flat lens that focuses light as effectively as traditional curved lenses while preserving accurate color. This technology could transform astrophotography imaging systems, especially in applications where space is at a premium, such as on aircraft, satellites and space-based telescopes.
Their latest study, featured on the cover of the journal Applied Physics Letters, was led by Menon Lab member Apratim Majumder, a research assistant professor in the Department of Electrical & Computer Engineering. Coauthors include fellow Menon Lab members Alexander Ingold and Monjurul Meem, Department of Physics & Astronomy’s Tanner Obray and Paul Ricketts, and Nicole Brimhall of Oblate Optics.
If you’ve ever used a magnifying glass, you know that lenses bend light to make objects appear larger. The thicker and heavier the lens, the more it bends the light, and the stronger the magnification. For everyday cameras and backyard telescopes, lens thickness isn’t a huge problem. But when telescopes must focus light from galaxies millions of light-years away, the bulk of their lenses become impractical. That’s why observatory and space-based telescopes rely on massive, curved mirrors instead to achieve the same light-bending effect since they can be made much thinner and lighter than lenses.
Scientists have also tried to solve the bulkiness problem by designing flat lenses, which manipulate light in a different way. One existing type, called a Fresnel zone plate (FZP), uses concentric ridges to focus light, rather than a thick, curved surface. While this method does create a lightweight and compact lens, it comes with a tradeoff: it can’t produce true colors. Rather than bending all of the wavelengths of visible light at the same angle, the ridges of an FZP diffract them at different angles, resulting in an image with chromatic aberrations, or color distortions.
Enter Rajesh Menon and his team at the U. Their new flat lens offers the same light-bending power as traditional curved lenses while avoiding the color distortions of FZPs.
“Our computational techniques suggested we could design multi-level diffractive flat lenses with large apertures that could focus light across the visible spectrum and we have the resources in the Utah Nanofab to actually make them,” said Menon, who directs the U’s Laboratory for Optical Nanotechnologies.
The key innovation lies in the microscopically small concentric rings that the researchers can pattern on the substrate. Unlike the ridges of FZPs, which are optimized for a single wavelength, the size and spacing of the flat lens’ indentations keep the diffracted wavelengths of light close enough together to produce a full-color, in-focus image.
“Simulating the performance of these lenses over a very large bandwidth, from visible to near-infrared, involved solving complex computational problems involving very large datasets,” Majumder said. “Once we optimized the design of the lens’ microstructures, the manufacturing process involved required very stringent process control and environmental stability.”
A large, flat, color-accurate lens could have massive implications across industries, but its most immediate application is in astronomy. The researchers demonstrated the capabilities of their flat lens with test images of the sun and moon.
“Our demonstration is a stepping stone towards creating very large aperture lightweight flat lenses with the capability of capturing full-color images for use in air-and-space-based telescopes,” Majumder said.
The concentric rings of microscopic indentations on the researchers’ flat lens are optimized to bring all wavelengths of light into focus at the same time.
Credit
Menon Lab, University of Utah
The study, “Color astrophotography with a 100 mm-diameter f/2 polymer flat lens,” appeared on Feb. 3 in Applied Physics Letters. This research was supported by the Defense Advanced Research Projects Agency, or DARPA, (FA8650-20-C-7020 P00001), the Office of Naval Research (N00014-22-1-2014), and NASA (NNL16AA05C). This content is solely the responsibility of the authors and does not necessarily represent the official views of these funding agencies. Monjurul Meem is now a process engineer at Intel.
Journal
Applied Physics Letters
Method of Research
Imaging analysis
Subject of Research
Not applicable
Article Title
Color astrophotography with a 100 mm-diameter f/2 polymer flat lens
Article Publication Date
3-Feb-2025
COI Statement
Yes, R.M. and N.B. have financial interest in Oblate Optics, Inc.
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