Hubble Sees Galaxy with Dark Rings in New Light - UNIVERSE

This NASA/ESA Hubble Space Telescope image features an uncommon galaxy with a striking appearance. NGC 7722 is a lenticular galaxy located about 187 million light-years away in the constellation Pegasus.

A lenticular, meaning “lens-shaped,” galaxy is a type whose classification sits between more familiar spiral galaxies and elliptical galaxies. It is also less common than spirals and ellipticals — partly because these galaxies have a somewhat ambiguous appearance, making it hard to determine if it is a spiral, an elliptical, or something in between. Many of the known lenticular galaxies sport features of both spiral and elliptical. In this case, NGC 7722 lacks the defined arms of a spiral galaxy, while it has an extended, glowing halo and a bright bulge in its center like an elliptical galaxy. Unlike elliptical galaxies, it has a visible disk — concentric rings swirl around its bright nucleus. Its most prominent feature, however, is undoubtedly the long lanes of dark red dust coiling around the outer disk and halo.

This NASA/ESA Hubble Space Telescope image of NGC 7722, a lenticular galaxy located about 187 million light-years away, features concentric rings of dust and gas that appear to swirl around its bright nucleus.

ESA/Hubble & NASA, R. J. Foley (UC Santa Cruz), Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA; Acknowledgment: Mehmet Yüksek

This new Hubble image, the sharpest taken of NGC 7722, brings the galaxy’s impressive dust lanes into sharp focus. Bands of dust like this are not uncommon in lenticular galaxies, and they stand out against the broad, smooth halo of light that typically surrounds lenticulars. Astronomers think NGC 7722’s distinctive dust lanes are the result of a past merger with another galaxy, similar to other lenticular galaxies. Researchers do not fully understand how lenticular galaxies form, but they think mergers and other gravitational interactions play an important part in reshaping galaxies and exhausting their supplies of gas while bringing new dust.

While it doesn’t host as many new, young stars as a spiral galaxy, there’s still activity in NGC 7722: in 2020 it was host to the explosion of a star that astronomers detected from Earth. SN 2020SSF was a Type Ia supernova, an event that occurs when a white dwarf star in a binary system siphons enough mass away from its companion star that it grows unstable and explodes. These explosions output a remarkably consistent level of light: by measuring how bright they appear from Earth and comparing that to how bright they intrinsically are, astronomers can tell how far away they must be. Type Ia supernovae are one of the best ways to measure distances to galaxies, so understanding exactly how they work is of great importance for astronomy.

Taken with Hubble’s Wide Field Camera 3, this Hubble image was obtained as part of an observing program (#16691, PI: R. J. Foley) that followed up on recent supernovae. SN 2020SSF, is not visible in this image. Researchers purposefully observed NGC 7722 two years after the supernova faded to witness the supernova’s aftereffects and examine its surroundings, which can only be accomplished once the intense light of the explosion is gone. With Hubble’s clear vision, astronomers can search for radioactive material created by the supernova, catalog its neighbors to help determine the original star’s age, and look for the companion star it left behind — all from almost 200 million light-years away.

Text Credit: European Space Agency (ESA)  

Source: Hubble Sees Galaxy with Dark Rings in New Light - NASA Science

Mesh bioreactor achieves 20‑fold efficiency increase and 50% cost reduction for wastewater treatment - Engineering - Energy & Green Tech

Schematic of transient cavitation-driven biofouling control using piezoelectric device. Credit: HKUST

A Hong Kong University of Science and Technology (HKUST) research team has developed a wastewater treatment technology that integrates a mesh bioreactor with an ultrasound-induced transient cavitation cleaning mechanism. The system can complete mesh cleaning within 3.8 seconds under anaerobic conditions and achieves 10–20 times higher flux than conventional membrane bioreactors (MBRs). The technology operates efficiently with substantially lower energy consumption, produces treated effluent surpassing international and local discharge standards, and reduces the cost of treating each cubic meter of wastewater to 50% of conventional MBRs, offering a sustainable solution for both municipal and industrial wastewater treatment.

The research was led by Prof. Chen Guanghao, Chair Professor of the Department of Civil and Environmental Engineering at HKUST, together with Dr. Guo Hongxiao, Postdoctoral Fellow and Luo Yu, Ph.D. student in the same department. The study, titled "Transient cavitation enables ultrafast fouling removal in mesh bioreactors for efficient sludge–liquid separation during wastewater treatment", was published in the journal Nature Water.

Conventional secondary wastewater treatment worldwide commonly relies on MBR systems, where aerobic or anaerobic microorganisms degrade organic matter in wastewater. Under the Hong Kong Drainage Services Department standards, the total suspended solids (TSS) of secondary-treated effluent must reach 30 mg/L or below. While MBRs are effective in separating suspended biomass from water, they face persistent membrane fouling, requiring regular cleaning and membrane replacement, leading to high operational costs.

The HKUST team designed a mesh bioreactor (MeBR) using 10–200 μm mesh material to achieve separation mainly through a biocake layer that self-forms on the mesh from retained solids and microbial biomass. The technology incorporates piezoelectric ultrasound transducers that generate cavitation of microbubbles, which rapidly form and collapse to remove fouling from the mesh surface. This mechanism enables complete cleaning within 10 seconds under aerobic conditions, and as quickly as 3.8 seconds under anaerobic conditions when treating domestic wastewater.

Video demonstration of cavitation-driven cleaning on fouled aerobic mesh. Credit: Nature Water (2025). DOI: 10.1038/s44221-025-00531-7 – Follow link for video: Mesh bioreactor achieves 20‑fold efficiency increase and 50% cost reduction for wastewater treatment

Key breakthroughs of the system include:

• Each square meter of mesh can process 148–307 L m⁻² h⁻¹, achieving 10–20 times the flux of conventional MBRs while maintaining mesh integrity over long-term operation.
• The treated effluent maintains a TSS below 20 mg/L, outperforming Hong Kong's 30 mg/L standard and meeting discharge requirements in approximately 75% of the global population.
• The system requires only 2.5–47 Wh/m³, significantly reducing overall operational expenditure.

The first author of the paper and Ph.D. student at HKUST, Luo explained, "Across 120 days of continuous filtration tests and an additional 21‑day trial using real municipal wastewater, the meshes retained their structural integrity. Although minor physical changes—such as variations in pore size and surface roughness—were observed after long-term operation, they did not compromise the mechanical stability of the meshes, demonstrating the system's durability."

Dr. Guo, corresponding author added, "The technology enables the mesh to operate stably at ultrahigh fluxes that far exceed those of typical MeBRs and reach 10–20 times those of conventional MBR systems, without any additional cleaning requirements. The ultrahigh fluxes also reduce the biocake reformation period to under 10 minutes, overcoming a long-standing challenge and ensuring stable effluent quality during continuous operation."

Prof. Chen, corresponding author, stated, "Cities worldwide are facing increasing pressures from climate change, rising energy costs and growing wastewater loads. Treating more wastewater with fewer resources is becoming a universal challenge. This technology demonstrates that high‑flux treatment can be achieved while still meeting stringent global discharge standards, potentially easing the burden on existing facilities and offering a more flexible solution for densely populated cities.

"Based on current analyses, the system can reduce the treatment cost by approximately US$0.05 per cubic meter of wastewater resulting in significant cumulative benefit. Ultimately, our goal is to deliver research that creates real and meaningful value for society."

Provided by Hong Kong University of Science and Technology 

by Hong Kong University of Science and Technology

edited by Gaby Clark, reviewed by Robert Egan

Source: Mesh bioreactor achieves 20‑fold efficiency increase and 50% cost reduction for wastewater treatment