Hilo based JCMT astronomer wins prestigious NASA Fellowship

Dr. Alex Tetarenko wins prestigious NASA Fellowship

Dr. Alex Tetarenko, a Hilo-based astronomer who works at the James Clerk Maxwell Telescope (JCMT), has been selected as a new Fellow by NASA for its prestigious NASA Hubble Fellowship Program (NHFP). Dr. Tetarenko was one of 24 NHFP Fellows to be selected out of more than 400 applicants. The program enables outstanding postdoctoral scientists to pursue independent research in any area of NASA Astrophysics, using theory, observation, experimentation, or instrument development.

With the proposed research topic “Unraveling the Complex Nature of Black Holes and How They Power Explosive Outflows with Time-Domain Observations”, Tetarenko will help provide answers on how the universe works.

Alex Tetarenko was born and raised in Calgary, Alberta, Canada. She received her BSc in Astrophysics from the University of Calgary, and she pursued graduate school at the University of Alberta, obtaining her MSc in 2014 and her PhD in 2018. Alex’s PhD thesis was awarded the J.S. Plaskett Medal from the Canadian Astronomical Society for the most outstanding doctoral thesis in Canada. Following her PhD studies, Alex took up an independent fellowship at the Maunakea Observatories in Hawaiʻi, working at the East Asian Observatory’s James Clerk Maxwell Telescope, where she currently resides.

“I am super excited for this amazing opportunity, and while I will be sad to leave the island, I am incredibly grateful for my time here and for all the support I have received over the past several years, which most certainly played a big part in being able to win this Fellowship,” said Tetarenko.

Alex’s research focuses on studying relativistic jets launched from stellar-mass black hole systems in our galaxy, to understand the complex relationship between the mass plunging into a black hole and the material that is jettisoned away. The main goals of her research are to develop new ways to study jets launched from black holes, both in terms of designing observing techniques to gather new types of data, as well as building new computational and statistical tools to analyze this data.

As an Einstein fellow, Alex’s pioneering research program will implement a novel time-domain technique to observe galactic black hole systems at radio wavelengths. This innovative technique, adapting algorithms used in X-ray astronomy, allows her to directly measure the physical properties of black hole jets and how they evolve through measuring how the intensity of the light we receive from these jets varies over different time-scales. With this research, she will place constraints on jet speeds, energetics, and size-scales, in turn allowing her to begin to address key open questions in jet research, such as understanding the energy source of these jets and the impact they have on their environment. This work will also provide benefits to the broader scientific community, through developing statistical techniques that can be applied to big data problems, and building new observing methods applicable for the operations and data analysis at next-generation telescopes.


For more information: https://hubblesite.org/contents/news-releases/2021/news-2021-16

Contact: Dr. Alex Tetarenko a.tetarenko@eaobservatory.org

See this announcement in the West Hawaii Today.

Formation of the Hub–Filament System G33.92+0.11: Local Interplay between Gravity, Velocity, and Magnetic Field

Figure 1. B-field orientations (segments) sampled on a 12” grid overlaid on 850 μm dust continuum (color and contours), sampled on a 4” grid, of the G33.92+0.11 region. The segments are rotated by 90° to represent magnetic field orientations. The yellow and white segments display the larger than 3 and 2–3 polarization detections. The green contours show the total intensity at 20, 50, 200, 300, 500, 1000, and 
 2000 mJy beam-1.

Interstellar filaments are ubiquitous in molecular clouds, and they are a key intermediate stage toward the formation of stars. Previous observations found that many stars commonly form within clustered environments associated with hub–filament systems (HFSs), where they are formed in a dense hub with numerous radial filaments extending from the central hub (Myers 2009, ApJ, 700:1609). Understanding how HFSs form is a topic of considerable interest since HFSs are the possible transition stage connecting the evolution of filamentary clouds and the formation of protoclusters.

G33.92+0.11 is such an HFS, where two massive protoclusters have been discovered by ALMA within the central 0.6 pc area of a dense hub associated with several few pc- length converging filaments (Liu et al. 2019, ApJ, 871:185). Since the size of the entire HFS is well beyond the maximum recoverable scale of interferometers, JCMT observations are essential to investigate the large-scale environments where the massive HFS could form.

We performed polarization observations using JCMT POL-2 to probe the magnetic field morphology in this 5-pc HFS. It is widely known that this polarized continuum emission originates from the dichoric alignment of interstellar dust grains along magnetic field lines in the interstellar medium through the Radiative Alignment Torques (RATs), and so the observed polarization orientation traces the plane-of-sky magnetic field morphology (Andersson et al. 2015 ARA&A, 53:501).

The magnetic field structure inferred from our POL-2 observations reveals a converging pattern pointing toward the hub center (Figure 1), apparently similar to the converging filamentary structures identified from the dust continuum map shown in the top panel of Figure 2, implying that the evolution of the converging filaments is coupled with magnetic fields.

Figure 2: Differential orientation maps for filament vs. magnetic field, local gravity, and local velocity gradient (from top to bottom) overlaid on the 850 μm intensity. The cyan lines are the identified filaments. The yellow and white segments represent the magnetic field orientations, the red arrows are the projected local gravity, and the magenta arrows show the local velocity gradients. Filled color-coded circles (color wedge) are the pairwise differential orientations

In order to evaluate the relative importance among gravity, turbulence, and magnetic fields, we used the modified Davis-Chandrasekhar-Fermi technique to estimate the energy scale of these physical parameters (Houde et al. 2009, ApJ, 706:1504). By combining our POL-2 polarization data and the velocity information extracted from the IRAM 30-m C18O (2-1) data, the obtained ratio of kinematic to gravitational energy is 0.10–0.20, and the ratio of magnetic to gravitational energy is 0.05–0.10. Hence, the global gravitational energy dominates the kinematic and magnetic energy and appears to be the major driving factor in the evolution of these filaments on a global scale.

The Davis-Chandrasekhar-Fermi technique only describes the averaged global properties over the entire system. It is important to note that many physical parameters, such as densities however, the physical parameters, including densities, gas velocities, magnetic field strengths, etc., are far from being homogeneous but actually vary by orders of magnitudes in such a dynamical HFS. Therefore, an analysis merely focusing on the global aspect might lack information on spatial variations which is essential for us to understand how the physical condition evolves from the ambient material to the converging filaments, and to the central hub. Hence, we additionally developed an approach aiming at studying the detailed local interplay between the spatial properties of the filamentary structures, the magnetic fields, the local gravitational force, and the local velocity gradient.

As a first step to investigate the spatial properties, we performed an all-pairwise comparison of the relative orientation among filaments, magnetic fields, local gravitational force, and local velocity gradient on the dust continuum map (Figure 2). This comparison reveals systematic changes of these relative orientations from diffuse extending filaments toward the densest hub center. With statistics based on the Kolmogorov-Smirnov test, we conclude that the filaments tend to align with the magnetic field and local gravity in the dense hub. In the low-density areas, we find that the local velocity gradients tend to be perpendicular to both the magnetic field and local gravity, although the filaments still tend to align with local gravity.

Combining local and global aspects, we propose a scenario where G33.92+0.11 is a multiscale gravitationally collapsing cloud with relatively weak turbulence and magnetic field. The ambient gas in the diffuse environment is accreted onto the filaments, while the filaments drag the magnetic field lines and flow toward the gravitational center (illustrated in Figure 3). Due to the resolution limitation, the observed local velocity gradients mainly trace the gas accumulation from the surrounding to the filaments, especially in low-density areas, and are thus perpendicular to the filaments. The observed magnetic field is stretched by the accretion flows, especially in high-density areas, and is therefore aligned with filaments and gravity.

One challenge of this scenario is how these converging filaments remain stable without fragmenting into numerous cores before reaching the hub center. To answer this question, we estimate the variation of critical linear density along these filaments considering the support from both thermal, non-thermal, and magnetic support. We find that the non-thermal kinematic energy within these filaments, traced by the local velocity dispersion, is significantly increasing with the local density. In return, this can stabilize filaments from self-fragmenting until reaching the central hub. This mechanism might also explain how a massive star/protocluster can accumulate a significant amount of mass from the large-scale environment.

Figure 3: Cartoon illustrating observed features. The black arrows represent the directions of local gravity. The yellow curve shows a model-compatible magnetic field morphology, with the orange segments displaying the observed field segments with a spatial resolution (~0.5 pc) comparable to the filament widths (0.5–1 pc). The magenta arrows illustrate the directions of gas motion, with the white arrows depicting the observed velocity gradients at the resolved 0.5 pc scale. The background color displays local density. An outer subcritical and inner supercritical zone is indicated.

This research was published in The Astrophysical Journal at: https://iopscience.iop.org/article/10.3847/1538-4357/abc74e

Authors: Jia-Wei Wang1,2, Patrick M. Koch1, Roberto Galván-Madrid3, Shih-Ping Lai2, Hauyu Baobab Liu1, Sheng-Jun Lin2, and Kate Pattle2,4    

Edited by Steve Mairs

Author Affiliations:

1 Academia Sinica Institute of Astronomy and Astrophysics, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan

2 Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan; jwwang@asiaa.sinica.edu.tw

3 Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán, Mexico

4 Centre for Astronomy, School of Physics, National University of Ireland Galway, University Road, Galway, Ireland

Pōwehi: Astronomers Image Magnetic Fields at the Edge of M87’s Black Hole

Two Hawai`i-based telescopes, the James Clerk Maxwell Telescope (JCMT), operated by the East Asian Observatory, and the Submillimeter Array (SMA), operated by the Smithsonian Astrophysical Observatory and the Academia Sinica Institute for Astronomy and Astrophysics, have once again combined efforts with the global network of telescopes known as the Event Horizon Telescope. Today the image of Pōwehi, the Black Hole at the Centre of M87, has been shown in new light – specifically polarized light. The polarized light has enabled astronomers for the first time in history to measure polarization, a signature of magnetic fields, this close to the edge of a black hole. The observations are key to explaining how the M87 galaxy, located 55 million light-years away, is able to launch energetic jets from its core.

“We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets that extend far beyond the galaxy,” says Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University in the Netherlands.

On 10 April 2019, scientists released the first ever image of a black hole, Pōwehi, revealing a bright ring-like structure with a dark central region — the black hole’s shadow. Since then, the EHT collaboration has delved deeper into the data on the supermassive object at the heart of the M87 galaxy collected in 2017. They have discovered that a significant fraction of the light around the M87 black hole is polarized.

A view of the M87 supermassive black hole in polarized light. The Event Horizon Telescope (EHT) collaboration, who produced the first ever image of a black hole released in 2019, has today a new view of the massive object Pōwehi at the centre of the Messier 87 (M87) galaxy: how it looks in polarized light. This is the first time astronomers have been able to measure polarization, a signature of magnetic fields, this close to the edge of a black hole.This image shows the polarized view of the black hole in M87. The lines mark the orientation of polarization, which is related to the magnetic field around the shadow of the black hole. Credit: EHT

Light becomes polarized when it goes through certain filters. As an example many of us here in Hawai`i have polarized sunglasses, in space light can become polarized when it is emitted in hot regions of space that are magnetized. In the same way polarized sunglasses help us see better by reducing reflections and glare from bright surfaces, astronomers can sharpen their vision of the region around the black hole by looking at how the light originating from there is polarized. Specifically, polarization allows astronomers to map the magnetic field lines present at the inner edge of the black hole.

The bright jets of energy and matter that emerge from M87’s core and extend at least 5000 light-years from its centre are one of the galaxy’s most mysterious and energetic features. Most matter lying close to the edge of a black hole falls in. However, some of the surrounding particles escape moments before capture and are blown far out into space in the form of jets.

Hilo astronomer Geoff Bower who is the EHT Project Scientist said These beautiful images tell an amazing story of how powerful magnetic fields control the black hole’s appetite and funnel part of its lunch out at nearly the speed of light.  Producing these images was an incredible technical achievement from observations around the world to sophisticated image analysis.” 

Astronomers have relied on different models of how matter behaves near the black hole to better understand this process. But they still don’t know exactly how jets larger than the galaxy are launched from its central region, which is as small in size as the Solar System, nor how exactly matter falls into the black hole. With the new EHT image of the black hole and its shadow in polarized light, astronomers managed for the first time to look into the region just outside the black hole where this interplay between matter flowing in and being ejected out is happening.

This composite image shows three views of the central region of the Messier 87 (M87) galaxy in polarised light. The galaxy has a supermassive black hole at its centre and is famous for its jets, that extend far beyond the galaxy. One of the polarised-light images, obtained with the Chile-based Atacama Large Millimeter/submillimeter Array (ALMA), shows part of the jet in polarised light, with a size of 6000 light years from the centre of the galaxy. The other polarised light images zoom in closer to the supermassive black hole: the middle view covers a region about one light year in size and was obtained with the National Radio Astronomy Observatory’s Very Long Baseline Array (VLBA) in the US. The most zoomed-in view was obtained by linking eight telescopes around the world to create a virtual Earth-sized telescope, the Event Horizon Telescope or EHT. This allows astronomers to see very close to the supermassive black hole, into the region where the jets are launched. The lines mark the orientation of polarisation, which is related to the magnetic field in the regions imaged.The ALMA data provides a description of the magnetic field structure along the jet. Therefore the combined information from the EHT and ALMA allows astronomers to investigate the role of magnetic fields from the vicinity of the event horizon (as probed with the EHT on light-day scales) to far beyond the M87 galaxy along its powerful jets (as probed with ALMA on scales of thousand of light-years). The values in GHz refer to the frequencies of light at which the different observations were made. The horizontal lines show the scale (in light years) of each of the individual images. Credit: © EHT Collaboration; ALMA (ESO/NAOJ/NRAO), Goddi et al.; VLBA (NRAO), Kravchenko et al.; J. C. Algaba, I. Martí-Vidal

The team found that only 0.1% of the theoretical models can explain what the astronomers are seeing at the event horizon. The new observations also revealed information about the structure and strength of the magnetic field just outside the black hole that astronomers didn’t have before.

“Our first glimpse of Pōwehi – a snapshot of the total light intensity –  was like seeing the movie poster. Now, with our polarized glasses on, we have front row seats as the film begins. The polarized images show us how black holes do what they do and why we see what we see,”  JCMT Deputy Director, Dr Jessica Dempsey states. “Our worldwide and home team pushed every technical, theoretical and observational boundary to achieve this. And we are still in the first minutes of the story. We have so much more to see. Pass the popcorn.”

To observe the heart of the M87 galaxy, the collaboration linked eight telescopes around the world, including the JCMT and SMA located on Maunakea, to create a virtual Earth-sized telescope, the EHT. The impressive resolution obtained with the EHT is equivalent to that needed to measure the length of a credit card on the surface of the Moon.

This allowed the team to directly observe the black hole shadow and the ring of light around it, with the new polarized-light image clearly showing that the ring is magnetized.

“The EHT is a one-of-a-kind facility to test the laws of physics in a region of extreme gravity. It gives us a unique chance to look at phenomena we have never studied before,” says EHT collaboration member Jongho Park, an East Asian Core Observatories Association Fellow at the Academia Sinica, Institute of Astronomy and Astrophysics in Taiwan.

Future EHT observations will reveal even more information about the mysterious region of space near the event horizons of supermassive black holes.The results are published today in two separate papers in The Astrophysical Journal Letters by the EHT collaboration. The research, which was coordinated by Mościbrodzka, involved over 300 researchers from multiple organisations and universities worldwide. Simon Radford, Director of Hawaii Operations, Submillimeter Array said “This research showcases the close cooperation between observatories in Hawai’i and elsewhere. The SMA and the JCMT have participated in the EHT for more than a decade. They will continue to play a major role in future EHT observations because of their location, their technology, and the dedication of their talented staff.” 

Supplemental information

This research was presented in two papers published today in The Astrophysical Journal.

The Event Horizon Telescope

The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe, North and South America. The international collaboration is working to capture the most detailed black hole images ever obtained by creating a virtual Earth-sized telescope. Supported by considerable international investment, the EHT links existing telescopes using novel systems — creating a fundamentally new instrument with the highest angular resolving power that has yet been achieved.

The individual telescopes involved are: ALMA, APEX, the IRAM 30-meter Telescope, the IRAM NOEMA Observatory, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope (LMT), the Submillimeter Array (SMA), the Submillimeter Telescope (SMT), the South Pole Telescope (SPT), the Kitt Peak Telescope, and the Greenland Telescope (GLT).

The EHT consortium consists of 13 stakeholder institutes: the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University and the Smithsonian Astrophysical Observatory.


Astronomers collaborated with renowned Hawaiian language and cultural practitioner Dr. Larry Kimura for the Hawaiian naming of the supermassive black hole at the centre of the galaxy M87. Pōwehi, meaning embellished dark source of unending creation, is a name sourced from the Kumulipo, the primordial chant describing the creation of the Hawaiian universe. Pō, profound dark source of unending creation, is a concept emphasized and repeated in the Kumulipo, while wehi, or wehiwehi, honored with embellishments, is one of many descriptions of pō in the chant. Dr. Kimura is an associate professor at University of Hawai‘i at Hilo Ka Haka ‘Ula o Ke‘elikolani College of Hawaiian Language.

Media Contacts

Geoff Bower
Chief Scientist for Hawaii Operations, ASIAA
Project Scientist, Event Horizon Telescope
Affiliate Graduate Faculty, UH Manoa Physics and Astronomy


Jessica Dempsey
Deputy Director of the East Asian Observatory (EAO) and JCMT

Local Media Coverage

JCMT and ALMA: Hunting for stellar nurseries in Orion

Stars are known to form in so-called “molecular clouds”; collections of cold gas and dust in the space between stars. These stellar nurseries can contain a number of dense clumps of gas and dust called “prestellar cores”. Research has suggested that these cores are expected to exhibit concentrated structures within them – the “seeds” of new stars right at the cusp of being born.

Strong efforts by astronomers have been made to find such “seeds” of stars inside prestellar cores in the past, but mostly in vain. It was difficult to catch such seeds in action perhaps because they are short-lived, but also due to the inherent difficulties in observing such dense regions and at such small scales. Despite the challenges, Dipen Sahu, at the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), Taiwan, and lead author of this study stated that “despite the challenges it is very important to understand when and how such stellar embryo(s) come to live” noting that “it is this critical early stage that is important to observe as we understand how these early stages shape the stellar offspring. We would like to know how stellar systems are formed, but we need to study them near their birth to fully understand the process.”

We would like to know how stellar systems are formed, but we need to find them near their birth to understand the process.

One of the closest, brightest and most well known stellar nurseries can be found in the constellation of Orion also known as the Ka Hei-Hei O Nā Keiki (which refers to a children’s string game similar to the cat’s cradle) in Hawaiian. The international team, including astronomers from Taiwan, China, Japan, and Korea, first started out to uncover cold and dense cores in the Orion Molecular Cloud. As dust in the cores absorbs light and blocks the view at the optical wavelengths, astronomers make use of “light” emitted by the dust inside the dense cores at submillimeter wavelengths, obtained using such telescopes as the James Clark Maxwell Telescope (JCMT) situated on the slopes of Maunakea in Hawaii.

Core “G205.46-14.56M3” located in the Orion Molecular Cloud shows signs of multiple small blobs inside. Top right insert: SCUBA-2 image of G2-5.46-14.56M3 as observed by the JCMT, Hawaii. Bottom left insert: ALMA resolves the newly forming stars within. The Orion Constellation is also known as the Ka Hei-Hei O Nā Keiki (“the cat’s cradle”) in Hawaiian. Credit: ASIAA/Wei-Hao Wang/ALMA (ESO/NAOJ/NRAO)/Tie Lie/Sahu et al.

“The JCMT continues to play a pivotal role in locating these cores!”, says Tie Liu at Shanghai Astronomical Observatory, co-author of this study and the principal investigator of the ALMA observation program, “the JCMT is critical in that it gives us the speed to hunt around these stellar nurseries with the sensitivity needed to find these faint regions of cold and dense gas”.

With JCMT providing the team with stellar nursery candidates, the team turned to the largest telescope on the ground to date, the Atacama Large Millimeter and submillimeter Array (ALMA) located in the high desert in northern Chile. The observations carried out with ALMA in late 2018 to early 2019 unveil to the team five cores with  a very concentrated gas and dust distribution at a scale of a 1000 AU. Toward one core named “G205.46-14.56M3” in particular, the image shows signs of multiple small peak structures inside. These peaks are estimated to harbor a high density of cold gas that has never been seen before and their significant mass makes astronomers think that they are very likely to form a binary star system in the future. It is known that a large fraction of Sun-like stars are in binary or multiple stellar systems. Sheng-Yuan Liu at ASIAA, co-author of this study stated “ALMA provides us with unprecedented sensitivity and angular resolution so that we can see faint sources with truly sharp images. Finding twins or triplets should be common in stellar nurseries but it is remarkable to actually obtain the image like seeing inside an egg with two yolks!”

Finding twins or triplets should be common in stellar nurseries but it is remarkable to actually obtain the image like seeing inside an egg with two yolks!

It remains unclear what leads to the sub-structures we see in the core of G205.46-14.56M3. The substructures are likely a complicated interplay between the gas motion, gravity, and magnetic fields that are threading through the gas. The observed emission from the dust only tells us how gas and dust are distributed. Understanding how the gas is moving and how magnetic fields are distributed inside such cores would allow astronomers to further pinpoint the decisive process.

“Detecting such a handful of stellar seeds is just the beginning and the JCMT has proven to be a great tool for uncovering these nurseries. I am excited to see what new discoveries we will make when we combine the power of both JCMT and future followup studies with ALMA”, says Dipen Sahu.

The publication

This work was published: “ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Detection of Extremely High-density Compact Structure of Prestellar Cores and Multiple Substructures Within” by Dipen Sahu et al. in the Astrophysical Journal Letters.

The team is composed of Dipen Sahu (Academia Sinica Institute of Astronomy and Astrophysics), Sheng-Yuan Liu (Academia Sinica Institute of Astronomy and Astrophysics), Tie Liu (Shanghai Astronomical Observatory, Chinese Academy of Sciences), Neal J. Evans II (Department of Astronomy The University of Texas at Austin), Naomi Hirano (Academia Sinica Institute of Astronomy and Astrophysics), Ken’ichi Tatematsu (Nobeyama Radio Observatory, National Astronomical Observatory of Japan, National Institutes of Natural Sciences), Chin-Fei Lee(Academia Sinica Institute of Astronomy and Astrophysics), Kee-Tae Kim (Korea Astronomy and Space Science Institute), Somnath Dutta (Academia Sinica Institute of Astronomy and Astrophysics), Dana Alina (Department of Physics, School of Sciences and Humanities, Nazarbayev University)

Contact Information

Dr. Sheng-Yuan Liu
Academia Sinica Institute of Astronomy and Astrophysics
ASIAA, Taiwan
Email: syliu@asiaa.sinica.edu.tw

Dr. Jessica Dempsey
James Clerk Maxwell Telescope
East Asian Observatory, Hawaii, USA
Email: ​j.dempsey@eaobservatory.org

Media Releases:

  • Media release at ASIAA
  • Media release at SHAO
  • Media release at NAOJ

JCMT Astronomer helps size up the first black hole ever detected

Dr. Alex Tetarenko, a Hilo based astronomer who works at the James Clerk Maxwell Telescope (JCMT), has been collaborating with an international team of researchers to analyze new observations of the first black hole ever detected. Their discovery is leading astronomers to question what they know about the Universe’s most mysterious objects.

Dr. Alex Tetarenko, Credit: EAO

Published today in the journal Science, the research shows that the system known as Cygnus X-1, contains the most massive stellar-mass black hole ever detected without the use of gravitational waves. “Our new observations have shown us that Cygnus X-1 is further away from Earth than previously thought, which in turn tells us this black hole is much larger than previous estimates, weighing in at more than 20 times the mass of our own Sun” says Dr. Tetarenko.


The Cygnus X-1 binary system consists of a stellar-mass black hole that is pulling material off of a ‘donor star’. “Our new observations have shown us that Cygnus X-1 is further away from Earth than previously thought, which in turn tells us the black hole is much larger than previous estimates, weighing in at more than 20 times the mass of our own Sun.” Artist: Pete Wheeler (COMET) Credit: International Centre for Radio Astronomy Research.

Cygnus X-1 is one of the closest black holes to Earth. It was discovered in 1964 when a pair of Geiger counters were carried on board a sub-orbital rocket launched from New Mexico. This object was famously the focus of a scientific wager between physicists Stephen Hawking and Kip Thorne, with Hawking betting in 1974 that it was not a black hole and eventually conceding the bet in 1990.

In this latest work, astronomers observed a full orbit of the black hole over a six day period using the Very Long Baseline Array — a continent-sized radio telescope made up of 10 dishes spread across the United States — together with a clever technique to measure distances in space. “One of the telescopes in the Very Long Baseline Array is located in Hawaiʻi on the slopes of Maunakea, and this antenna plays a critical role in making it possible to do this kind of science” explains Dr. Tetarenko.

Lead researcher, Professor James-Miller Jones from Curtin University and the International Centre for Radio Astronomy Research (ICRAR) outlines the clever technique used by this team of researchers. “If we can view the same object from different locations, we can calculate its distance away from us by measuring how far the object appears to move relative to the background. If you hold your finger out in front of your eyes and view it with one eye at a time, you’ll notice your finger appears to jump from one spot to another. It’s exactly the same principle.”

“The domino effect of our new observations has led to fascinating new insights about how stars evolve and how black holes form” says co-author Dr. Arash Bahramian, who is also at Curtin University and ICRAR. Tetarenko and Bahramian are longtime colleagues, having both completed their PhDs at the University of Alberta in Canada.

In fact, this study has sparked two more companion papers. Co-author Professor Ilya Mandel from Monash University and the ARC Centre of Excellence in Gravitational Wave Discovery (OzGrav) further explains the wide reaching implications of this work.

“Cygnus X-1 in particular began life as a star approximately 60 times the mass of the Sun and collapsed tens of thousands of years ago. During their lifetime stars lose mass to their surrounding environment through stellar winds that blow away from their surface. But to make a black hole as heavy as Cygnus X-1, we need to dial down the amount of mass that bright stars lose during their lifetimes”.

The new measurements of distance and mass also tell us that the black hole in Cygnus X-1 is spinning incredibly quickly (very close to the speed of light), as shown in a second companion paper led by PhD candidate, Xueshan Zhao, at the Chinese Academy of Sciences.

“All of these exciting discoveries were made possible by the collaboration between a diverse group of international astronomers focused on different observational and theoretical aspects of black holes, all coming together for a new extensive and rigorous look at a known but previously elusive black hole.” adds Dr. Bahramian.

As the next generation of telescopes comes online, their improved sensitivity reveals the Universe in increasingly more detail, leveraging decades of effort invested by scientists and research teams around the world to better understand the cosmos and the exotic and extreme objects that exist.

“Studying black holes is like shining a light on the Universe’s best kept secret—it’s a challenging but incredibly exciting area of research” says Professor Miller-Jones. “There is so much left to discover about these enigmatic astrophysical objects” adds Dr. Tetarenko.


Original Publication:
‘Cygnus X-1 contains a 21-solar mass black hole – implications for massive star winds’, published in Science on February 18th, 2021.

Companion Papers:
‘Reestimating the Spin Parameter of the Black Hole in Cygnus X-1’, published in The Astrophysical Journal on February 18th, 2021.

‘Wind mass-loss rates of stripped stars inferred from Cygnus X-1’, published in The Astrophysical Journal on February 18th, 2021.


Dr. Alex Tetarenko, EAO Fellow, East Asian Observatory

Dr. Jessica Dempsey, Deputy Director of the East Asian Observatory (EAO) and JCMT


Local Media Coverage

Call for Proposals 21B



The East Asian Observatory is happy to invite PI observing proposals for semester 21B at the JCMT. Proposal submission is via the JCMT proposal handling system, Hedwig. For full details, and for proposal submission, please see


The 21B Call for Proposals closes on the 16th of March, 2021.

If this is your first time using Hedwig, you should ‘Log in’ and generate an account. There is a Hedwig ‘Help’ facility at the upper right corner of each page, and individual Help tags in many other places.

Please contact us at helpdesk@eaobservatory.org if you have remaining questions.

First Light with new JCMT receiver `Āweoweo

IRC+10216, also known as CW Leonis – a carbon star embedded in a thick dust envelope, was the target for first light observations with the second Nāmakanui insert; `Āweoweo. This spectrum was captured on the night of January 13 2021 (UT 20200114).

`Āweoweo operates between 283 – 365 GHz and is a Sideband Separating (2SB) instrument. When commissioned, `Āweoweo, will be available to both JCMT Users (PI and Large Programs – perfect for sensitive single pointing observations), and VLBI users (as part of the Event Horizon Telescope and the East Asian VLBI Network).

JCMT staff presented “Commissioning of Nāmakanui on the JCMT” at the SPIE conference in December 2020. For details see: Mizuno et al. 2020.

SCUBA-2 captures Jupiter and Saturn Conjunction

JCMT astronomers were excited to capture the conjunction of Saturn and Jupiter on December 21st 2020 using SCUBA-2. The conjunction – although occurring every 20 years the closest one prior to 2020 was in 1623 and this won’t be matched again until the Jupiter-Saturn conjunction of March 15, 2080. Telescope operator Kevin Silva was on hand to capture this unique moment.

Aside from science, the telescope operators at JCMT do use Jupiter or Saturn for focusing, and occasionally Saturn for pointing. Dr Harriet Parsons was interviewed by Hawaii News Now about the event.

Jupiter and Saturn as observed by SCUBA-2 at a wavelength of 0.85mm. Remember we are not seeing our Sun’s light reflected off the planets, what we are seeing is the planet “glowing” thermally in submillimeter, similar to how the volcanologists monitor Halema`uma`u crate at night – the active volcano on Hawai`i. Jupiter we see is much brighter than Saturn, larger in angular extent. Saturn is slightly elongated – thanks to Saturn’s rings.

Jupiter and Saturn are so bright that we have a harder time seeing the fainter moons of Jupiter. In this resealed image we get to see Callisto, the moon of Jupiter approximately 3.8′ out from Jupiter. The Spikes we see around Jupiter is artificial – they are diffraction spikes caused by light bending/diffracting around the support beams of our secondary mirror. The brighter circles around Jupiter and Saturn are also artificial – they are caused from the sheer brightness of the planets.