Author: jcmtadmin

Maunakea Hawaii – JCMT astronomers studying stellar nurseries, the birthplace of stars in our galaxy, have found that nearly  half of stars in the Galaxy are formed in binary/multiple stellar systems (think twins, triplets, quadruplets). Despite the prevalence of binary/multiple births previous studies of stellar nurseries have concentrated more on how single stars form. The origin of binary/multiple stellar systems remains a mystery to astronomers.

The birth of all stars requires the gravitational collapse of cold dense pockets of gas and dust (known as cores) found in what are known as molecular clouds. However, previous investigations have rarely addressed how the properties of the host dense cores affect stellar multiplicity. To address this question a team of astronomers using the JCMT in Hawaii and ALMA telescope in Chile looked to the Orion Cloud complex – of the closest active star formation region. Located in the Orion constellation at about 1,500 light-years away this stellar nursery is an ideal laboratory for testing various models of star formation.

Using the JCMT telescope, astronomers identified 49 cold dense cores in the Orion clouds, locations which are in the process of forming young stars. The team then used the Atacama Large Millimeter/submillimeter Array (ALMA) to unveil the internal structures within these dense cores.

G205.46-14.56 clump located in Orion molecular cloud complex. The yellow contours stand for the dense cores discovered by JCMT, and the zoomed-in pictures shows the 1.3mm continuum emission of ALMA observation. These observations give insight into the formation of various stellar systems in dense cores.

Using the high-resolution ALMA observation, astronomers find that about 30% of the 49 cores are giving birth to binary/multiple stars, while the other cores are only forming single-stars. Astronomers then estimated the physical characteristics (size, density and mass) of these dense cores from the JCMT observations. Surprisingly, astronomers found that cores forming binary/multiple stars tend to show higher densities and higher masses than those cores forming single stars, although the sizes of various cores show no much differences. “This is understandable. Denser cores are much easier to fragment due to the perturbations caused by self-gravity inside molecular cores.” says Qiuyi Luo, a Ph.D. student at Shanghai Astronomical Observatory, who is the first author of this work published in The Astrophysical Journal.

The team also observed the 49 cores in N₂H⁺ J=1-0 molecular line with the Nobeyama 45-m telescope. They found that N₂H⁺ line widths of cores forming binary/multiple stars are statistically larger than that of cores forming single stars. “These Nobeyama observations provide a good measurement of turbulence levels in dense cores. Our findings indicate that binary/multiple stars tend to form in more turbulent cores”, says Prof.Ken’ichi Tatematsu, who lead the Nobeyama observations.

Summarizing the findings Qiuyi Luo said “In a word, we found that binary/multiple stars tend to form in denser and more turbulent molecular cores in this study”. Adding to this comment Sheng-Yuan Liu at ASIAA, co-author of this study stated “The JCMT has proven to be a great tool for uncovering these stellar nurseries for ALMA follow-ups. With ALMA providing unprecedented sensitivity and resolution so that we can do similar studies toward a much sample of larger dense cores for a more thorough understanding of star formation”.

As for future work, corresponding author and lead for the ALMA data Tie Liu, commented: “we have yet to look at the effect of magnetic fields in our analysis. Magnetic field may suppress the fragmentation in dense cores so we are excited to focus the next stage of our research on this area using the JCMT”.

This work was published: “ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): How Do Dense Core Properties Affect the Multiplicity of Protostars?” by Qiuyi Luo et al. in the Astrophysical Journal.

The work presented here was part of a wider collection of work with relevant links/publications provided below:

• JCMT SCOPE (SCUBA-2 Continuum Observations of Pre-protostellar Evolution): https://www.eaobservatory.org/jcmt/science/large-programs/scope/
• ALMASOP (ALMA Survey of Orion Planck Galactic Cold Clumps): https://ui.adsabs.harvard.edu/public-libraries/eKQmqMjaSsKk5DrvPEu-Vg
• The JCMT SPACE survey (Submilimeter Polarization and Astro-Chemistry in Earliest star formation): https://www.eaobservatory.org/jcmt/science/large-programs/space/

MAUNAKEA, HAWAIʻI –– Astronomers have unveiled the first image of the supermassive black hole at the centre of our own Milky Way galaxy. This result provides overwhelming evidence that the object is indeed a black hole and yields valuable clues about the workings of such giants, which are thought to reside at the centre of most galaxies. The image was produced by a global research team called the Event Horizon Telescope (EHT) Collaboration, using observations from a worldwide network of radio telescopes including Hawai‘i-based James Clerk Maxwell Telescope (JCMT) and the Submillimeter Array (SMA).

The image is a long-anticipated look at the massive object that sits at the very centre of our galaxy. Scientists had previously seen stars orbiting around something invisible, compact, and very massive at the centre of the Milky Way. This strongly suggested that this object — known as Sagittarius A* (Sgr A*, pronounced “sadge-ay-star”) — is a black hole, and today’s image provides the first direct visual evidence of it.

First image of the black hole at the centre of the Milky Way. Credit: EHT Collaboration

Although we cannot see the black hole itself, because it is completely dark, glowing gas around it reveals a telltale signature: a dark central region (called a “shadow”) surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun.

“We were stunned by how well the size of the ring agreed with predictions from Einstein’s Theory of General Relativity,” said EHT Project Scientist Geoffrey Bower chief scientist for Hawai‘i operations from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei. “These unprecedented observations have greatly improved our understanding of what happens at the very centre of our galaxy, and offer new insights on how these giant black holes interact with their surroundings.” The EHT team’s results are being published today in a special issue of The Astrophysical Journal Letters [1].

Because the black hole is about 27,000 light-years away from Earth, it appears to us to have about the same size in the sky as a donut on the Moon. To image it, the team created the powerful EHT, which linked together eight existing radio observatories across the planet to form a single “Earth-sized” virtual telescope [2]. The EHT observed Sgr A* on multiple nights, collecting data for many hours in a row, similar to using a long exposure time on a camera.

In creating such an “Earth-sized” telescope the JCMT and SMA in Hawaii provided the most western point. Reflecting on Hawaii’s involvement in this image JCMT Head of Operations Dr Harriet Parsons noted “JCMT’s involvement in such work stretches back 15 years but Hawaii’s involvement in studying the black hole at the center of our Milky Way Galaxy has been an even longer love affair. Prior to this image, Dr. Andrea Ghez had used decades of data from the neighbouring W.M. Keck Observatory to examine orbits of stars around an invisible but massive compact object at the centre of our galaxy. This work earned her the Nobel Prize in 2020, together with Reinhard Genzel and Roger Penrose. To now have an actual image of that same black hole is incredible, and what is most exciting: this is in our home galaxy, the Milky Way.” 

The breakthrough follows the EHT collaboration’s 2019 release of the first image of a black hole, named Pōwehi (also known as M87*)[3], at the centre of the more distant Messier 87 galaxy.

Maunakea Hawaii – JCMT part of the Event Horizon Telescope, a global network of telescopes, that collected data to image the black hole at the center of the Milky Way. Image credit: W. Mongomerie, H. Parsons EAO/JCMT/EHT.

The two black holes look remarkably similar, even though our galaxy’s black hole is more than a thousand times smaller and less massive than Pōwehi [4]. “We have two completely different types of galaxies and two very different black hole masses, but close to the edge of these black holes they look amazingly similar,” says Sera Markoff, Co-Chair of the EHT Science Council and a professor of theoretical astrophysics at the University of Amsterdam, the Netherlands. “This tells us that General Relativity governs these objects up close, and any differences we see further away must be due to differences in the material that surrounds the black holes.”

This achievement was considerably more difficult than for Pōwehi, even though Sgr A* is much closer to us. EHT scientist Chi-kwan (‘CK’) Chan, from Steward Observatory and Department of Astronomy and the Data Science Institute of the University of Arizona, US, explains: “The gas in the vicinity of the black holes moves at the same speed — nearly as fast as light — around both Sgr A* and Pōwehi. But where gas takes days to weeks to orbit the larger Pōwehi, in the much smaller Sgr A* it completes an orbit in mere minutes. This means the brightness and pattern of the gas around Sgr A* was changing rapidly as the EHT Collaboration was observing it — a bit like trying to take a clear picture of a puppy quickly chasing its tail.”

The researchers had to develop sophisticated new tools that accounted for the gas movement around Sgr A*. While Pōwehi was an easier, steadier target, with nearly all images looking the same, that was not the case for Sgr A*. The image of the Sgr A* black hole is an average of the different images the team extracted, finally revealing the giant lurking at the centre of our galaxy for the first time.

Making of the image of the black hole at the centre of the Milky Way. Image credit: EHT Collaboration The Event Horizon Telescope (EHT) Collaboration has created a single image (top frame) of the supermassive black hole at the centre of our galaxy, called Sagittarius A* (or Sgr A* for short), by combining images extracted from the EHT observations. The main image was produced by averaging together thousands of images created using different computational methods — all of which accurately fit the EHT data. This averaged image retains features more commonly seen in the varied images, and suppresses features that appear infrequently. The images can also be clustered into four groups based on similar features. An averaged, representative image for each of the four clusters is shown in the bottom row. Three of the clusters show a ring structure but, with differently distributed brightness around the ring. The fourth cluster contains images that also fit the data but do not appear ring-like. The bar graphs show the relative number of images belonging to each cluster. Thousands of images fell into each of the first three clusters, while the fourth and smallest cluster contains only hundreds of images. The heights of the bars indicate the relative “weights,” or contributions, of each cluster to the averaged image at top.

The effort was made possible through the ingenuity of more than 300 researchers from 80 institutes around the world that together make up the EHT Collaboration. In addition to developing complex tools to overcome the challenges of imaging Sgr A*, the team worked rigorously for five years, using supercomputers to combine and analyse their data, all while compiling an unprecedented library of simulated black holes to compare with the observations.

Scientists are particularly excited to finally have images of two black holes of very different sizes, which offers the opportunity to understand how they compare and contrast. They have also begun to use the new data to test theories and models of how gas behaves around supermassive black holes. This process is not yet fully understood but is thought to play a key role in shaping the formation and evolution of galaxies.

“Now we can study the differences between these two supermassive black holes to gain valuable new clues about how this important process works,” said EHT scientist Keiichi Asada from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei. “We have images for two black holes — one at the large end and one at the small end of supermassive black holes in the Universe — so we can go a lot further in testing how gravity behaves in these extreme environments than ever before.”

Progress on the EHT continues: a major observation campaign in March 2022 included more telescopes than ever before. The ongoing expansion of the EHT network and significant technological upgrades will allow scientists to share even more impressive images as well as movies of black holes in the near future.

Notes

[1] The Astrophysical Journal Letters publish six collaboration and four official papers on Thursday, May 12th, 2022 at 13:07 UT.  The six collaboration papers (First Sagittarius A* Event Horizon Telescope Results):

• Paper I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• Paper II. EHT and Multi-wavelength Observations, Data Processing, and Calibration
• Paper III. Imaging of the Galactic Center Supermassive Black Hole
• Paper IV. Variability, Morphology, and Black Hole Mass
• Paper V. Testing Astrophysical Models of the Galactic Center Black Hole
• Paper VI. Testing the Black Hole Metric

Alongside four additional papers:

• Selective Dynamical Imaging of Interferometric Data
• Millimeter Light Curves of Sagittarius A* Observed during the 2017 Event Horizon Telescope Campaign
• A Universal Power Law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows
• Characterizing and Mitigating Intraday Variability: Reconstructing Source Structure in Accreting Black Holes with mm-VLBI

[2] The individual telescopes involved in the EHT in April 2017, when the observations were conducted, were: the Atacama Large Millimeter/submillimeter Array (ALMA), the Atacama Pathfinder Experiment (APEX), the IRAM 30-meter Telescope, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope Alfonso Serrano (LMT), the Submillimeter Array (SMA), the UArizona Submillimeter Telescope (SMT), the South Pole Telescope (SPT). Since then, the EHT has added the Greenland Telescope (GLT), the NOrthern Extended Millimeter Array (NOEMA) and the UArizona 12-meter Telescope on Kitt Peak to its network.

ALMA is a partnership of the European Southern Observatory (ESO; Europe, representing its member states), the U.S. National Science Foundation (NSF), and the National Institutes of Natural Sciences (NINS) of Japan, together with the National Research Council (Canada), the Ministry of Science and Technology (MOST; Taiwan), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA; Taiwan), and Korea Astronomy and Space Science Institute (KASI; Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, the Associated Universities, Inc./National Radio Astronomy Observatory (AUI/NRAO) and the National Astronomical Observatory of Japan (NAOJ). APEX, a collaboration between the Max Planck Institute for Radio Astronomy (Germany), the Onsala Space Observatory (Sweden) and ESO, is operated by ESO. The 30-meter Telescope is operated by IRAM (the IRAM Partner Organizations are MPG (Germany), CNRS (France) and IGN (Spain)). The JCMT is operated by the East Asian Observatory on behalf of the Center for Astronomical Mega-Science of the Chinese Academy of Sciences, NAOJ, ASIAA, KASI, the National Astronomical Research Institute of Thailand, and organizations in the United Kingdom and Canada. The LMT is operated by INAOE and UMass, the SMA is operated by Center for Astrophysics | Harvard & Smithsonian and ASIAA and the UArizona SMT is operated by the University of Arizona. The SPT is operated by the University of Chicago with specialized EHT instrumentation provided by the University of Arizona.

The Greenland Telescope (GLT) is operated by ASIAA and the Smithsonian Astrophysical Observatory (SAO). The GLT is part of the ALMA-Taiwan project, and is supported in part by the Academia Sinica (AS) and MOST. NOEMA is operated by IRAM and the UArizona 12-meter telescope at Kitt Peak is operated by the University of Arizona.

[3] In 2019 Astronomers collaborated with renowned Hawaiian language and cultural practitioner Dr. Larry Kimura for the Hawaiian naming of the black hole located at the center of a galaxy known as Messier 87. 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.

[4] Black holes are the only objects we know of where mass scales with size. A black hole a thousand times smaller than another is also a thousand times less massive.

More Information

About Event Horizon Telescope 

The EHT consortium consists of 13 stakeholder institutes; the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the Center for Astrophysics | Harvard & Smithsonian, 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, and Radboud University.

About James Clerk Maxwell Telescope

Operated by the East Asian Observatory, the James Clerk Maxwell Telescope (JCMT) is the largest astronomical telescope in the world designed specifically to operate in the submillimeter wavelength region of the spectrum. The JCMT has a diameter of 15 meters and is used to study our Solar System, interstellar and circumstellar dust and gas, and distant galaxies. It is situated near the summit of Maunakea, Hawai‘i, at an altitude of 4,092 meters.

The East Asian Observatory is a collaboration between our partner regions in China, Japan, Korea, Taiwan, Thailand, United Kingdom, Canada, Hong Kong, Vietnam, Malaysia, and Indonesia.  Click here for more information.

The East Asian Observatory wishes to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community.  We are most fortunate to have the opportunity to conduct observations from this mountain.

Links

• EHT website: https://eventhorizontelescope.org/
• Pōwehi 2019 result: https://www.eaobservatory.org/jcmt/2019/04/powehi/
• M. Keck/Andrea Ghez Nobel Prize: https://www.keckobservatory.org/nobel-prize-ghez/

Contacts

Harriet Parsons, JCMT Head of Operations, East Asian Observatory, Hilo, Hawaii

Local Media Coverage

• First image of Milky Way’s black hole produced, (Star Advertiser)
• Maunakea Observatories help astronomers capture image of Milky Way’s black hole, (Hawaii Tribune Herald)
• Maunakea Observatories help astronomers capture 1^st image of Milky Way’s huge black hole, (West Hawaii Today)
• 2 Maunakea Observatories help produce first image of black hole at center of the Milky Way, (Big Island Now)
• Black hole at center of Milky Way photographed for the first time using Mauna Kea telescopes, (Hawaii Tribune Herald)
• Maunakea telescopes helped produce the first image of Milky Way’s black hole, (Hawaii Public Radio)