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ALMA Radio Telescope Delivers Its Highest Resolution Image Yet

It pictured the laser-like emission in microwaves of a star in its twilight years.


Dr. Alfredo Carpineti


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

Alfredo (he/him) has a PhD in Astrophysics on galaxy evolution and a Master's in Quantum Fields and Fundamental Forces.

Senior Staff Writer & Space Correspondent

 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.

The hydrogen cyanide seen by ALMA (in blue) around star R Leporis (in orange).

Image credit: Y. Asaki - ALMA (ESO/NAOJ/NRAO)

Astronomers and engineers at the Atacama Large Millimeter/submillimeter Array (ALMA) have pushed the observatory's capabilities to the highest resolution yet. They were able to see features 5 milli-arcseconds apart in observations of the aged star R Leporis. That is equivalent to seeing a school bus on the surface of the Moon and it is a 15-fold improvement compared to previous observations of the same object.

The team achieved this by placing antennas in a configuration spanning 16 kilometers (10 miles) and using the highest frequency on the receiver (the so-called Band 10). They also used a new calibration method that helped refine the observations.


And the work paid off. The observations provide the most detailed look yet at the maser around R Leporis. A maser is exactly like a laser, but it is specific to microwave emission. In this case, it’s the emission of hydrogen cyanide that is found in a cloud that surrounds R Leporis.

 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.
A schematic view of how using a calibrator to work out the atmospheric fluctuation allows the team to massively improve resolution.
Image credit: ALMA (ESO/NAOJ/NRAO)/Y. Asaki et al.)

"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," Yoshiharu Asaki, the ALMA astronomer who led this project, said in a statement.

Other new details of the cloud of material around R Leporis came to life with a higher resolution; the team was also able to study the movement of this gas. The maser emission is in a specific wavelength and by looking for a Doppler shift – like the pitch of a siren changing if an ambulance is approaching or moving away – the team could work out if the gas was coming towards us or away.

 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 animation shows the motion of hydrogen cyanide moving around the star R Leporis
Image credit: Y. Asaki & N. Lira – ALMA (ESO/NAOJ/NRAO)

"It is very exciting to demonstrate the technical feasibility and scientific potential of high-frequency observations on ALMA's longest baselines," John Carpenter, observatory scientist, added. "We continue to advance ALMA's capabilities to unveil the Cosmos' mysteries, now with a sharper eye than ever."


R Leporis is located 1,350 light-years away – a well-known variable star that shines with a luminosity of about 6,700 times that of the Sun.

Papers describing the technical advancements on ALMA and the results on R Leporis are both published in The Astrophysical Journal.


spaceSpace and PhysicsspaceAstronomy
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  • radio telescope,

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  • R leporis