ALMA Achieve Unprecedented Resolution to Observe the Universe
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ALMA Achieve Unprecedented Resolution to Observe the Universe

15 November, 2023 / Read time: 6 minutes

Scientific Paper

The Atacama Large Millimeter/submillimeter Array (ALMA) has once again demonstrated its unparalleled ability to push the boundaries of astronomical observation. An international team of astronomers and engineers has successfully conducted an observation that achieved an extraordinary resolution of 5 milliarcseconds, using ALMA's highest frequency Band 10 receiver and an array configuration that spans 16 kilometers. This shows ALMA can be used by astronomers to observe objects in detail equivalent to seeing a 10-meter-long bus on the Moon.

This groundbreaking observation allowed the team to capture unprecedented details of a maser1 around an evolved star within the Milky Way. The observations used an innovative Band-to-band (B2B) phase-referencing technique that significantly enhances ALMA’s high-frequency capabilities.

John Carpenter, Observatory Scientist, shared his enthusiasm for the successful operation: " It is very exciting to demonstrate the technical feasibility and scientific potential of high-frequency observations on ALMA's longest baselines."

Antonio Hales, North American ALMA Regional Center Deputy Manager and part of the science team, reflected on the implications of this result: "Achieving this unparalleled resolution through the Band-to-band method has pushed ALMA's capabilities to their absolute limit, opening a new window for astrophysics. This allows astronomers to probe phenomena with a precision that was once beyond our reach.”

Yoshiharu Asaki, the ALMA Astronomer who led this project, highlighted the collaborative effort: "This remarkable achievement in high-resolution imaging through ALMA's advanced capabilities marks a significant milestone in our quest to understand the Universe. The success of the Band 10 high-resolution observation showcases our commitment to innovation and reinforces ALMA's position as a leader in astronomical discovery. We are excited about the new possibilities for the scientific community."

“These observations, showcasing the highest resolution that ALMA can attain, is a great example of what the hard work and dedication of international collaboration can achieve, including the many people behind the scenes” celebrates Luke Maud, ALMA Regional Center (ARC) Scientist from the European ARC, part of this project, and Principal Investigator in a precursor technical paper. He adds that “the band-to-band mode, facilitating more high-frequency observations and allowing us to reach the highest spatial resolution, lays the groundwork for a new era of discoveries.”

The observations represent a pivotal step forward in radio astronomy and are evidence of the international collaboration that makes such scientific advancements possible. "We continue to advance ALMA's capabilities to unveil the Cosmos' mysteries, now with a sharper eye than ever," concluded John Carpenter.

Additional Information

Precursor technical work was published in: “ALMA High-frequency Long-baseline Campaign in 2019: Band 9 and 10 In-band and Band-to-band Observations Using ALMA's Longest Baselines” by L. T. Maud, Y. Asaki et al., in the Astrophysical Journal on August 2023 (DOI: 10.3847/1538-4365/acd6f1)

The results of this research will appear in “ALMA High-frequency Long Baseline Campaign in 2021: Highest Angular Resolution Submillimeter Wave Images for the Carbon-rich Star R Lep” by Y. Asaki et al., in the Astrophysical Journal on November 15, 2023 (DOI:10.3847/1538-4357/acf619).

This announcement is based on the original Press Release by the National Astronomical Observatory of Japan (NAOJ).

ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), NSTC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.

Images, Videos and Animations

This image of R Leporis, a star in the final stages of its evolution, is the highest-resolution image ever achieved with ALMA. It has an angular resolution of 5 milli-arcseconds, equivalent to seeing a 10-metre-long bus on the Moon. It was conducted using the ALMA Band 10 (high-frequency) receivers, an array configuration with a maximum antenna separation of 16 kilometers, and a novel calibration technique known as Band-to-band. Submillimeter-wave emission from the stellar surface is shown in orange, and hydrogen cyanide maser emissions at 891 GHz are shown in blue. The observations show that a ring-like gas structure surrounds the star and that gas from the star is escaping to the surrounding space. Credit: Y. Asaki - ALMA (ESO/NAOJ/NRAO)
The evolved star R Leporis observed with ALMA's highest angular resolution - Peering into the depths of the cosmos, ALMA unveils the enigmatic beauty of R Leporis, a star in the twilight of its life. This high-resolution animation captures the star's submillimeter-wave radiation in a warm color palette, illustrating the vigorous activity in the star's outer layers. The cooler hues map the intricate dance of hydrogen cyanide (HCN) masers detected in ALMA's Band 10 at an impressively high frequency of 891 GHz. As you scroll through the animation, you can observe different parts of the HCN gas moving at varying radial velocities. The color of the gas indicates the direction it is moving in: redshift (positive velocity) means that the gas is moving away, while blueshift (negative velocity) means it is approaching. The image has an incredibly sharp angular resolution of 5 milli-arcseconds, the greatest resolution that ALMA can currently achieve. This image is a vibrant testament to the dynamic end-of-life processes of stars like R Leporis. Credit: Y. Asaki & N. Lira – ALMA (ESO/NAOJ/NRAO)
The evolved star R Leporis observed with ALMA's highest angular resolution - Peering into the depths of the cosmos, ALMA unveils the enigmatic beauty of R Leporis, a star in the twilight of its life. This high-resolution animation captures the star's submillimeter-wave radiation in a warm color palette, illustrating the vigorous activity in the star's outer layers. The cooler hues map the intricate dance of hydrogen cyanide (HCN) masers detected in ALMA's Band 10 at an impressively high frequency of 891 GHz. The animation shows different parts of the HCN gas moving at varying radial velocities. The color of the velocity indicates the direction it is moving in: redshift (positive velocity) means that the gas is moving away, while blueshift (negative velocity) means it is approaching. The image has an incredibly sharp angular resolution of 5 milli-arcseconds, the greatest resolution that ALMA can currently achieve. This image is a vibrant testament to the dynamic end-of-life processes of stars like R Leporis.
Credit: Y. Asaki & N. Lira – ALMA (ESO/NAOJ/NRAO)
In new observations that pushed ALMA capabilities to the extreme, researchers had to develop a new calibration method to obtain the highest-resolution ever image with ALMA. In this so-called band-to-band method, atmospheric fluctuations are compensated for by observing a nearby calibrator in low-frequency radio waves, while the target is observed with high-frequency radio waves. The top right inset image shows the ALMA image of R Leporis that achieved the highest resolution of 5 milli-arcseconds. Submillimeter-wave emission from the stellar surface is shown in orange and hydrogen cyanide maser emissions at 891 GHz are shown in blue. The top left inset image shows a previous observation of the same star using a different array configuration with less distance between the antennas and without the band-to-band method, resulting in a resolution of 75 milli-arcsec. The previous resolution is too coarse to specify the positions of each of the two emission components.

Note

  1. A maser is an astronomical phenomenon where molecules in space emit intense, focused beams of microwave radiation. These natural masers often occur in star-forming regions or around dying stars, where certain conditions cause molecules like hydrogen cyanide to release energy coordinatedly. This creates a powerful microwave signal that astronomers can detect and analyze to understand distant cosmic environments' physical conditions and dynamics. ↩︎

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