String theory solves mystery about how particles behave outside a black hole photon sphere

Figure 1. An artist’s impression of a “string” passing near a black hole. As the string approaches the black hole, it is gradually stretched. Then, as it moves past the black hole, it begins to vibrate. The image to the left, which was captured by the Event Horizon Telescope, represents the shadow of the supermassive black hole at the center of the galaxy M87, including the ring of light around it. (Credit: EHT Collaboration; Kavli IPMU (Kavli IPMU modified EHT’s original image)).

A paper by the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Director Ooguri Hirosi and Project Researcher Matthew Dodelson on the string theoretical effects outside the black hole photon sphere has been selected for the “Editors’ Suggestion” of the journal Physical Review D. Their paper was published on March 24, 2021.

In a quantum theory of point particles, a fundamental quantity is the correlation function, which measures the probability for a particle to propagate from one point to another. The correlation function develops singularities when the two points are connected by light-like trajectories. In a flat spacetime, there is such a unique trajectory, but when spacetime is curved, there can be many light-like trajectories connecting two points. This is a result of gravitational lensing, which describes the effect of curved geometry on the propagation of light.

In the case of a black hole spacetime, there are light-like trajectories winding around the black hole several times, resulting in a black hole photon sphere, as seen in the recent images by the Event Horizon Telescope (EHT) of the supermassive black hole at the center of the galaxy M87. 

Released on April 10, 2019, the EHT Collaboration’s images captured the shadow of a black hole and its photon sphere, the ring of light surrounding it. A photon sphere can occur in a region of a black hole where light entering in a horizontal direction can be forced by gravity to travel in various orbits. These orbits lead to singularities in the aforementioned correlation function.

However, there are cases when the singularities generated by trajectories winding around a black hole multiple times contradict with physical expectations. Dodelson and Ooguri have shown that such singularities are resolved in string theory. 

In string theory, every particle is considered as a particular excited state of a string. When the particle travels along a nearly light-like trajectory around a black hole, the spacetime curvature leads to tidal effects, which stretch the string. 

Dodelson and Ooguri showed that, if one takes these effects into account, the singularities disappear consistently with physical expectations. Their result provides evidence that a consistent quantum gravity must contain extended objects such as strings as its degrees of freedom. 

Ooguri says, “Our results show how string theoretical effects are enhanced near a black hole. Though the effects we found are not strong enough to have an observable consequence on ETH’s black hole image, further research may show us a way to test string theory using black holes.”

Paper details:

Journal: Physical Review D
Title: Singularities of thermal correlators at strong coupling

Authors: Matthew Dodelson (a), Hirosi Ooguri (a, b)
Author affiliation:
a. Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
b. Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, CA 91125, USA 

DOI: 10.1103/PhysRevD.103.066018 (Posted on March 24, 2021)
Abstract of the treatise (Physical Review D)
Preprint (arXiv.org website) https://arxiv.org/abs/2010.09734

Research contact:

Hirosi Ooguri
Director, Principal Investigator
Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo
E-mail: hirosi.ooguri@ipmu.jp
 

Matthew Dodelson
Project Researcher
Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo
Email: matthew.dodelson@ipmu.jp

Media contact

John Amari
Public Relations Officer
Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo
E-mail: press@ipmu.jp
TEL: 080-4056-2767

Source: Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU)

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First interstellar comet may be the most pristine ever found

PR Image eso2106a

Image of the 2I/Borisov interstellar comet captured with the VL

 

PR Image eso2106b

Artist’s impression of the surface of interstellar comet 2I/Borisov

 

PR Image eso2106c

Artist’s impression of the surface of interstellar comet 2I/Borisov (close up)

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Videos

PR Video eso2106a

ESOcast 236 Light: First interstellar comet may be the most pristine ever found 

 

PR Video eso2106b

Animation of the orbit of interstellar comet 2I/Borisov 

 

PR Video eso2106c

Artist’s animation of the surface of interstellar comet 2I/Borisov

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New observations with the European Southern Observatory’s Very Large Telescope (ESO’s VLT) indicate that the rogue comet 2I/Borisov, which is only the second and most recently detected interstellar visitor to our Solar System, is one of the most pristine ever observed. Astronomers suspect that the comet most likely never passed close to a star, making it an undisturbed relic of the cloud of gas and dust it formed from.

2I/Borisov was discovered by amateur astronomer Gennady Borisov in August 2019 and was confirmed to have come from beyond the Solar System a few weeks later. “2I/Borisov could represent the first truly pristine comet ever observed,” says Stefano Bagnulo of the Armagh Observatory and Planetarium, Northern Ireland, UK, who led the new study published today in Nature Communications. The team believes that the comet had never passed close to any star before it flew by the Sun in 2019.

Bagnulo and his colleagues used the FORS2 instrument on ESO's VLT, located in northern Chile, to study 2I/Borisov in detail using a technique called polarimetry [1]. Since this technique is regularly used to study comets and other small bodies of our Solar System, this allowed the team to compare the interstellar visitor with our local comets.

The team found that 2I/Borisov has polarimetric properties distinct from those of Solar System comets, with the exception of Hale–Bopp. Comet Hale–Bopp received much public interest in the late 1990s as a result of being easily visible to the naked eye, and also because it was one of the most pristine comets astronomers had ever seen. Prior to its most recent passage, Hale–Bopp is thought to have passed by our Sun only once and had therefore barely been affected by solar wind and radiation. This means it was pristine, having a composition very similar to that of the cloud of gas and dust it — and the rest of the Solar System — formed from some 4.5 billion years ago.

By analysing the polarisation together with the colour of the comet to gather clues on its composition, the team concluded that 2I/Borisov is in fact even more pristine than Hale–Bopp. This means it carries untarnished signatures of the cloud of gas and dust it formed from.

“The fact that the two comets are remarkably similar suggests that the environment in which 2I/Borisov originated is not so different in composition from the environment in the early Solar System,” says Alberto Cellino, a co-author of the study, from the Astrophysical Observatory of Torino, National Institute for Astrophysics (INAF), Italy.

Olivier Hainaut, an astronomer at ESO in Germany who studies comets and other near-Earth objects but was not involved in this new study, agrees. “The main result — that 2I/Borisov is not like any other comet except Hale–Bopp — is very strong,” he says, adding that “it is very plausible they formed in very similar conditions.”

“The arrival of 2I/Borisov from interstellar space represented the first opportunity to study the composition of a comet from another planetary system and check if the material that comes from this comet is somehow different from our native variety,” explains Ludmilla Kolokolova, of the University of Maryland in the US, who was involved in the Nature Communications research. 

Bagnulo hopes astronomers will have another, even better, opportunity to study a rogue comet in detail before the end of the decade. “ESA is planning to launch Comet Interceptor in 2029, which will have the capability of reaching another visiting interstellar object, if one on a suitable trajectory is discovered,” he says, referring to an upcoming mission by the European Space Agency.

An origin story hidden in the dust

Even without a space mission, astronomers can use Earth’s many telescopes to gain insight into the different properties of rogue comets like 2I/Borisov. “Imagine how lucky we were that a comet from a system light-years away simply took a trip to our doorstep by chance,” says Bin Yang, an astronomer at ESO in Chile, who also took advantage of 2I/Borisov’s passage through our Solar System to study this mysterious comet. Her team’s results are published in Nature Astronomy.

Yang and her team used data from the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, as well as from ESO’s VLT, to study 2I/Borisov’s dust grains to gather clues about the comet’s birth and conditions in its home system. 

They discovered that 2I/Borisov’s coma — an envelope of dust surrounding the main body of the comet — contains compact pebbles, grains about one millimetre in size or larger. In addition, they found that the relative amounts of carbon monoxide and water in the comet changed drastically as it neared the Sun. The team, which also includes Olivier Hainaut, says this indicates that the comet is made up of materials that formed in different places in its planetary system.

The observations by Yang and her team suggest that matter in 2I/Borisov’s planetary home was mixed from near its star to further out, perhaps because of the existence of giant planets, whose strong gravity stirs material in the system. Astronomers believe that a similar process occurred early in the life of our Solar System.

While 2I/Borisov was the first rogue comet to pass by the Sun, it was not the first interstellar visitor. The first interstellar object to have been observed passing by our Solar System was ʻOumuamua, another object studied with ESO’s VLT back in 2017. Originally classified as a comet, ʻOumuamua was later reclassified as an asteroid as it lacked a coma.

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Notes

[1] Polarimetry is a technique to measure the polarisation of light. Light becomes polarised, for example,  when it goes through certain filters, like the lenses of polarised sunglasses or cometary material. By studying the properties of sunlight polarised by a comet’s dust, researchers can gain insights into the physics and chemistry of comets.

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More Information

This research highlighted in the first part of this release was presented in the paper “Unusual polarimetric properties for interstellar comet 2I/Borisov” to appear in Nature Communications (doi: 10.1038/s41467-021-22000-x). The second part of the release highlights the study “Compact pebbles and the evolution of volatiles in the interstellar comet 2I/Borisov” to appear in Nature Astronomy (doi: 10.1038/s41550-021-01336-w).

The team who conducted the first study is composed of S. Bagnulo (Armagh Observatory & Planetarium, UK [Armagh]), A. Cellino (INAF – Osservatorio Astrofisico di Torino, Italy), L. Kolokolova (Department of Astronomy, University of Maryland, US), R. Nežič (Armagh; Mullard Space Science Laboratory, University College London, UK; Centre for Planetary Science, University College London/Birkbeck, UK), T. Santana-Ros (Departamento de Fisica, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante, Spain; Institut de Ciencies del Cosmos, Universitat de Barcelona, Spain), G. Borisov (Armagh; Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Bulgaria), A. A. Christou (Armagh), Ph. Bendjoya (Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France), and M. Devogele (Arecibo Observatory, University of Central Florida, US).

The team who conducted the second study is composed of Bin Yang (European Southern Observatory, Santiago, Chile [ESO Chile]), Aigen Li (Department of Physics and Astronomy, University of Missouri, Columbia, USA), Martin A. Cordiner (Astrochemistry Laboratory, NASA Goddard Space Flight Centre, USA and Department of Physics, Catholic University of America, Washington, DC, USA), Chin-Shin Chang (Joint ALMA Observatory, Santiago, Chile [JAO]), Olivier R. Hainaut (European Southern Observatory, Garching, Germany), Jonathan P. Williams (Institute for Astronomy, University of Hawai‘i, Honolulu, USA [IfA Hawai‘i]), Karen J. Meech (IfA Hawai‘i), Jacqueline V. Keane (IfA Hawai‘i), and Eric Villard (JAO and ESO Chile).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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Links

• Research papers:
• Bagnulo et. al, Nature Communications
• Yang et. al, Nature Astronomy
• Photos of the VLT
• Photos of the ALMA
• For scientists: got a story? Pitch your research

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Contacts:

Stefano Bagnulo
Armagh Observatory and Planetarium
Armagh, UK
Tel: +44 (0)28 3752 3689
Email: Stefano.Bagnulo@Armagh.ac.uk

Alberto Cellino
INAF Torino
Turin, Italy
Tel: +39 011 8101933
Email: alberto.cellino@inaf.it

Ludmilla Kolokolova
Department of Astronomy, University of Maryland
College Park, Maryland, USA
Tel: +1-301-405-1539
Email: lkolokol@umd.edu

Bin Yang
European Southern Observatory
Santiago, Chile
Email: byang@eso.org

Olivier Hainaut
European Southern Observatory
Garching bei München, Germany
Tel: +49 89 3200 6752
Cell: +49 151 2262 0554
Email: ohainaut@eso.org

Bárbara Ferreira
European Southern Observatory
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: press@eso.org

Source: ESO/News

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Stellar Eggs near Galactic Center Hatching into Baby Stars

ALMA pseudo-color composite image of the gas outflows from baby stars in the Galactic Center region. Gas moving toward us is shown in blue and gas moving away from us is shown in red. Credit: ALMA (ESO/NAOJ/NRAO), Lu et al. Hi-res image

Astronomers found a number of baby stars hiding around the center of the Milky Way using the Atacama Large Millimeter/submillimeter Array (ALMA). Previous studies had suggested that the environment there is too harsh to form stars because of the strong tidal forces, strong magnetic fields, high energy particles, and frequent supernova explosions. These findings indicate that star formation is more resilient than researchers thought. These observations suggest there is ubiquitous star formation activity hidden deep in dense molecular gas, which may allow for the possibility of a future burst of star formation around the Galactic Center. 

“It is like hearing babies’ cries in a place we expected to be barren,” says Xing Lu, an astronomer at the National Astronomical Observatory of Japan. “It is very difficult for babies to be born and grow up healthily in an environment that is too noisy and unstable. However, our observations prove that even in the strongly disturbed areas around the Galactic Center, baby stars still form.”

Stars are formed in cosmic clouds gathered by gravity. If something interferes with the gravity driven processes, star formation will be suppressed. There are many potential sources of interference in the Central Molecular Zone (CMZ) of the Milky Way, located within a radius of 1000 light-years from the Galactic Center. Examples include strong turbulence which stirs up the clouds and prevents them from contracting, or strong magnetic fields can support the gas against self-gravitational collapse. In fact, previous observations indicated that star formation here is much less efficient; with the exception of one active star forming region called Sagittarius B2 (Sgr B2).

Lu and his colleagues used ALMA to tackle the mystery of suppressed star formation in most of the CMZ. The target regions contain an ample amount of gas, but no star formation has been expected. Contrary to the traditional picture, the team discovered more than 800 dense cores of gas and dust particles in the CMZ. “The discovery leads to the question of whether they are actually ‘stellar eggs’ or not,” says Lu. To look for telltale signs of star formation indicative of stellar eggs, the team again used ALMA to search for energetic gas outflows, which are like the birth cries of baby stars. Thanks to ALMA’s high sensitivity and high spatial resolution, for the first time, they detected 43 small and faint outflows in the clouds. This is unambiguous evidence of ongoing star formation. It turned out that many baby stars were hiding in the regions that were thought to be unsuitable for stellar growth.

The small number of detected outflows is another mystery. Considering the fact that more than 800 “stellar eggs” have been found, the small number of “stellar babies” might indicate that the star formation activity in the CMZ is in the very early phase. “Although a large number of outflows might be still hidden in the regions, our results may suggest we are seeing the beginning of the next wave of active star formation,” says Lu.

“Although previous observations have suggested that overall star formation rates are suppressed to about 10% in the giant molecular clouds in the Galactic Center, this observation shows that the star formation processes hidden in dense molecular gas clouds are not very different from those of the Solar neighborhood,” explains Shu-ichiro Inutsuka, a professor at Nagoya University and a co-author of the research paper. “The ratio of the number of star-forming cores to star-less cores seems to be only a few times smaller than that in the Solar neighborhood. This can be regarded as the ratio of their respective lifetimes. We think that the average duration of the star-less core stage in the Galactic Center might be somewhat longer than in the Solar neighborhood. More research is needed to explain why it is so.”

The research team is now analyzing ALMA’s higher resolution observation data for the CMZ and aims to study the properties of the accretion disks around the baby stars which drive the gas outflows. By comparing with other star forming regions, they hope to better understand star formation in the CMZ, from clouds to protostars, and from chemistry to magnetic fields.

 
Paper information

These observation results were presented in Xing Lu et al. “ALMA Observations of Massive Clouds in the Central Molecular Zone: Ubiquitous Protostellar Outflows” in the Astrophysical Journal on March 16, 2021.

This research was supported by the Japan Society of Promotion of Science (JSPS) KAKENHI (No. 18K13589 & 20K14528), the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through an Emmy Noether Research Group (grant number KR4801/1-1), the DFG Sachbeihilfe (grant number KR4801/2-1), the SFB 881 “The Milky Way System” (subproject B2), the European Union’s Horizon 2020 research and innovation programme via the ERC Starting Grant MUSTANG (grant agreement number 714907), and the National Science Foundation under Award No. 1816715.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organization for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

 Source:  Atacama Large Millimeter/submillimeter Array (ALMA)

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New light on baryonic matter and gravity on cosmic scales

The presence of ionized gas around galaxies with moves with them leaves a trace in the microwave background radiation which can be detected knowing the pattern of velocities of the galaxies provided by the map. Credit: Carlos Hernández-Monteagudo (IAC).

Scientists estimate that dark matter and dark energy together are some 95% of the gravitational material in the universe while the remaining 5% is baryonic matter, which is the “normal” matter composing stars, planets, and living beings. However for decades almost one half of this matter has not been found either. Now, using a new technique, a team in which the Instituto de Astrofísica de Canarias (IAC) has participated, has shown that this “missing” baryonic matter is found filling the space between the galaxies as hot, low density gas. The same technique also gives a new tool that shows that the gravitational attraction experienced by galaxies is compatible with the theory of General Relativity. This research is published today in three articles in the journal Monthly Notices of the Royal Astronomical Society (MNRAS).

In designing this new technique they have analyzed the changes in the electromagnetic spectrum, its shift to the red, caused by the reddening of the light from the galaxies as they speed away from us. In the Universe, the sources which move away show a redder spectrum, and those which approach us show a bluer spectrum. This effect has given essential data for the development of modern cosmology. Almost a century ago, Edwin Hubble discovered that the redshifts of galaxies are bigger the further away from us they are, and this was the initial evidence which eventually led to the Big Bang model of the universe. Since then these redshifts have been used to find the distances to the galaxies and to build three dimensional maps of their distribution in the Universe.

In the work we are reporting here a new method has been developed, which studies the statistics of the redshifts of galaxies, without converting them to distances. In their first article, the team shows that these maps are sensitive to the gravitational attraction between galaxies on cosmological scales. In a second article, the same team compare the maps with observations of the cosmic microwave background,, and they permit, for the first time, a complete census of the baryonic matter during 90% of the life of the Universe.

“Most of this 'ordinary' matter is invisible to us because it is not sufficiently hot to emit energy. However, by using maps of the redshifts of the galaxies we find that all of this matter fills the space between them”, explains Jonás Chaves-Montero, a researcher at the Donostia International Physics Center (DIPC) and first author of this article.

Finally, as found in a third article, the researchers have also used the redshift maps of the galaxies to study the nature of gravity. “In contrast to previous approaches, our new method is not based on any conversion of redshift to distance, and it is shown to be robust agains noise and data impurities. Thanks to that it allow us to conclude with high accuracy, that the observations are compatible with Einstein’s theory of gravity”, notes Carlos Hernández-Monteagudo, an IAC researcher who is the first author on this third article.

These studies have been performed by researchers Carlos Hernández-Monteagudo, Jonás Chaves-Montero, Raúl Angulo and Giovanni Aricò, who designed the research during their time at the Centre for Studies of Cosmic Physics of Aragón (CEFCA), even though now they are working at other Spanish research centres, such as the Instituto de Astrofísica de Canarias, and the Donostia International Physics Center. In one of the articles there was participation also by J. D. Emberson, a Canadian researcher at the Argonne National Laboratory, Illinois, USA.

 Authors

SCIENCE COMMUNICATION AND OUTREACH UNIT

 

References

Hernandez-Monteagudo, Carlos; Chaves-Montero, Jonas; Angulo, Raul E. “Angular R…

Articles:

Hernandez-Monteagudo, Carlos; Chaves-Montero, Jonas; Angulo, Raul E. “Angular Redshift Fluctuations: a New Cosmological Observable”. MNRAS: https://ui.adsabs.harvard.edu/abs/2019arXiv191112056H/abstract

Chaves-Montero, Jonas; Hernandez-Monteagudo, Carlos; Angulo, Raul E.; Emberson, J. D. “Measuring the evolution of intergalactic gas from z=0 to 5 using the kinematic Sunyaev-Zel'dovich effect”. MNRAS: https://ui.adsabs.harvard.edu/abs/2019arXiv191110690C/abstract

Hernández-Monteagudo, Carlos; Chaves-Montero, Jonás; Angulo, Raúl E.; Ariccò, Giovanni. “Tomographic Constraints on Gravity from Angular Redshift Fluctuations in the Late Universe”, MNRAS: https://ui.adsabs.harvard.edu/abs/2020arXiv200506568H/abstract  

Contact at the IAC: 

Carlos Hernández-Monteagudo: carlos.hernandez.monteagudo@iac.es

Source: Instituto de Astrofísica de Canarias - (IAC)/News

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New Images Reveal Magnetic Structures Near Supermassive Black Hole

View of the M87 supermassive black hole and jet

This composite image shows three radio-telescope views of the central region of the galaxy Messier 87 (M87), where a jet of fast-moving particles is ejected from the galaxy's core. In these images, the lines indicate polarization -- the alignment of the electric fields in the radio waves coming from the object. The polarization is a signature of the magnetic fields. The ALMA image shows the inner 6000 light-years of the jet. The image from the National Science Foundation's Very Long Baseline Array (VLBA) zooms down to show the inner one light-year of the jet, and the EHT image shows the region closest to the supermassive black hole at the galaxy's core. Labels indicate the observing frequency in GigaHertz (GHz) and the distance indicated by the scale bar below the frequency. Combined, these images allow astronomers to study the structure of magnetic fields from very close to the black hole to thousands of light-years outward from it. Credit: EHT Collaboration; Goddi et al., ALMA (ESO/NAOJ/NRAO); Kravchenko et al.; J. C. Algaba, I. Martí-Vidal, NRAO/AUI/NSF. Hi-Res File

ALMA image of M87 jet

This image shows a view of the jet in the galaxy Messier 87 (M87). The image was obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), while observing as part of the Event Horizon Telescope (EHT). The image captures the part of the jet, with a size of 6000 light years, closer to the center of the galaxy. The lines mark the orientation of polarization, which is related to the magnetic field in the region imaged. This ALMA image indicates what the structure of the magnetic field along the jet looks like. Credit: Goddi et al., ALMA (ESO/NAOJ/NRAO). Hi-Res File

New EHT Image

The new image of the region around the supermassive black hole at the core of the galaxy M87, from the Event Horizon Telescope. Lines show polarization of the radio emission from the area closest to the black hole. Credit: EHT Collaboration. Hi-Res File

 

A new view of the region closest to the supermassive black hole at the center of the galaxy Messier 87 (M87) has shown important details of the magnetic fields close to the black hole and hints about how powerful jets of material can originate in that region.

A worldwide team of astronomers using the Event Horizon Telescope, a collection of eight telescopes, including the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, measured a signature of magnetic fields — called polarization — around the black hole. Polarization is the orientation of the electric fields in light and radio waves and it can indicate the presence and alignment of magnetic fields.

“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,” said Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University in the Netherlands.

New images with the EHT and ALMA allowed scientists to map magnetic field lines near the edge of M87’s black hole. That same black hole is the first ever to be imaged — by the EHT in 2019. That image revealed a bright ring-like structure with a dark central region — the black hole’s shadow. The newest images are a key to explaining how M87, 50 million light-years from Earth, can launch energetic jets from its core.

The black hole at M87’s center is more than 6 billion times more massive than the Sun. Material drawn inward forms a rotating disk — called an accretion disk — closely orbiting the black hole. Most of the material in the disk falls into the black hole, but some surrounding particles escape and are ejected far out into space in jets moving at nearly the speed of light.

“The newly published polarized images are key to understanding how the magnetic field allows the black hole to ‘eat’ matter and launch powerful jets,” said Andrew Chael, a NASA Hubble Fellow at the Princeton Center for Theoretical Science and the Princeton Gravity Initiative in the U.S.

The scientists compared the new images that showed the magnetic field structure just outside the black hole with computer simulations based on different theoretical models. They found that only models featuring strongly magnetized gas can explain what they are seeing at the event horizon.

“The observations suggest that the magnetic fields at the black hole’s edge are strong enough to push back on the hot gas and help it resist gravity’s pull. Only the gas that slips through the field can spiral inwards to the event horizon,” explained Jason Dexter, Assistant Professor at the University of Colorado Boulder and Coordinator of the EHT Theory Working Group.

To make the new observations, the scientists linked eight telescopes around the world — including ALMA — 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 resolution allowed the team to directly observe the black hole shadow and the ring of light around it, with the new image clearly showing that the ring is magnetized. The results are published in two papers in the Astrophysical Journal Letters by the EHT collaboration. The research involved more than 300 researchers from multiple organizations and universities worldwide.

A third paper also was published in the same volume of the Astrophysical Journal Letters, based on data from ALMA, lead by Ciriaco Goddi, a scientist at Radboud University and Leiden Observatory, the Netherlands.

“The combined information from the EHT and ALMA allowed scientists to investigate the role of magnetic fields from the vicinity of the event horizon to far beyond the core of the galaxy, along its powerful jets extending thousands of light-years,” Goddi said.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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 Institut de Radioastronomie Millimetrique (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.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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Media Contact:

Dave Finley, Public Information Officer
(575) 835-7302
dfinley@nrao.edu

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Scientific Papers:

Paper VII (The Astrophysical Journal Letters, Vol. 910, L12):

Paper VIII (The Astrophysical Journal Letters, Vol. 910, L13):

Related Paper, Goddi et al., Polarimetric properties of Event Horizon Telescope targets from ALMA, The Astrophysical Journal Letters, Vol. 910, in press, 24 March 2021:

 

Source: National Radio Astronomy Observatory (NRAO)/News

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Is the nearest star cluster to the Sun being destroyed?

The Hyades and their tidal tails

The true extent of the Hyades tidal tails have been revealed for the first time by data from the ESA’s Gaia mission. The Gaia data has allowed the former members of the star cluster (shown in pink) to be traced across the whole sky. Those stars are marked in pink, and the shapes of the various constellations are traced in green. The image was created using Gaia Sky. ESA/Gaia/DPAC, CC BY-SA 3.0 IGO; acknowledgement: S. Jordan/T. Sagrista

Data from ESA’s Gaia star mapping satellite have revealed tantalising evidence that the nearest star cluster to the Sun is being disrupted by the gravitational influence of a massive but unseen structure in our galaxy.

If true, this might provide evidence for a suspected population of ‘dark matter sub-halos’. These invisible clouds of particles are thought to be relics from the formation of the Milky Way, and are now spread across the galaxy, making up an invisible substructure that exerts a noticeable gravitational influence on anything that drifts too close.

ESA Research Fellow Tereza Jerabkova and colleagues from ESA and the European Southern Observatory made the discovery while studying the way a nearby star cluster is merging into the general background of stars in our galaxy. This discovery was based on Gaia’s Early third Data Release (EDR3) and data from the second release.

The team chose the Hyades as their target because it is the nearest star cluster to the Sun. It is located just over 153 light years away, and is easily visible to skywatchers in both northern and southern hemispheres as a conspicuous ‘V’ shape of bright stars that marks the head of the bull in the constellation of Taurus. Beyond the easily visible bright stars, telescopes reveal a hundred or so fainter ones contained in a spherical region of space, roughly 60 light years across.

A star cluster will naturally lose stars because as those stars move within the cluster they tug at each other gravitationally. This constant tugging slightly changes the stars’ velocities, moving some to the edges of the cluster. From there, the stars can be swept out by the gravitational pull of the galaxy, forming two long tails.

One tail trails the star cluster, the other pulls out ahead of it. They are known as tidal tails, and have been widely studied in colliding galaxies but no one had ever seen them from a nearby open star cluster, until very recently.

Locating the Hyades tidal tails
Access the video

The key to detecting tidal tails is spotting which stars in the sky are moving in a similar way to the star cluster. Gaia makes this easy because it is precisely measuring the distance and movement of more than a billion stars in our galaxy. “These are the two most important quantities that we need to search for tidal tails from star clusters in the Milky Way,” says Tereza.

Previous attempts by other teams had met with only limited success because the researchers had only looked for stars that closely matched the movement of the star cluster. This excluded members that left earlier in its 600–700 million year history and so are now travelling on different orbits.

To understand the range of orbits to look for, Tereza constructed a computer model that would simulate the various perturbations that escaping stars in the cluster might feel during their hundreds of millions of years in space. It was after running this code, and then comparing the simulations to the real data that the true extend of the Hyades tidal tails were revealed. Tereza and colleagues found thousands of former members in the Gaia data. These stars now stretch for thousands of light years across the galaxy in two enormous tidal tails.

But the real surprise was that the trailing tidal tail seemed to be missing stars. This indicates that something much more brutal is taking place than the star cluster gently ‘dissolving’. 

Evolution of Hyades star cluster from ~ 650 million years ago until now
Access the video

Running the simulations again, Tereza showed that the data could be reproduced if that tail had collided with a cloud of matter containing about 10 million solar masses. “There must have been a close interaction with this really massive clump, and the Hyades just got smashed,” she says.

But what could that clump be? There are no observations of a gas cloud or star cluster that massive nearby. If no visible structure is detected even in future targeted searches, Tereza suggests that object could be a dark matter sub-halo. These are naturally occurring clumps of dark matter that are thought to help shape the galaxy during its formation. This new work shows how Gaia is helping astronomers map out this invisible dark matter framework of the galaxy.

“With Gaia, the way we see the Milky Way has completely changed. And with these discoveries, we will be able to map the Milky Way’s sub-structures much better than ever before,” says Tereza. And having proved the technique with the Hyades, Tereza and colleagues are now extending the work by looking for tidal tails from other, more distant star clusters.

Note For Editor

“The 800pc long tidal tails of the Hyades star cluster: Possible discovery of candidate epicyclic over-densities from an open star cluster” by Tereza Jerabkova et al. will be published online by Astronomy and Astrophysics on 24 March 2021. https://www.aanda.org/10.1051/0004-6361/202039949

For more information, please contact:
ESA Media Relations
Email: media@esa.int

Source: ESA/Space Science

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Pandora Mission Would Expand NASA’s Capabilities in Probing Alien Worlds

This illustration captures an exoplanet as it is about to cross in front of – or transit – its start
Credit: NASA's Goddard Space Flight Center. Hi-res image

This illustration (not to scale) depicts Pandora’s orbital pattern in Sun-synchronous low-Earth orbit, located approximately 435 to 497 miles (700 to 800 kilometers) above Earth’s surface, as it observes its targeted exoplanets and stars. This orbit enables Pandora to obtain multiple observations of exoplanets over long periods and the Earthshine exclusion zone helps avoid reflected light from Earth. Credits: Lawrence Livermore National Laboratory and NASA’s Goddard Space Flight Center.Hi-res image

This illustration depicts Pandora’s use of transit spectroscopy to reliably identify an exoplanet’s atmospheric composition as it passes in front of its host star. Credits: Lawrence Livermore National Laboratory and NASA’s Goddard Space Flight Center.Hi-res image

In the quest for habitable planets beyond our own, NASA is studying a mission concept called Pandora, which could eventually help decode the atmospheric mysteries of distant worlds in our galaxy. One of four low-cost astrophysics missions selected for further concept development under NASA’s new Pioneers program, Pandora would study approximately 20 stars and exoplanets – planets outside of our solar system – to provide precise measurements of exoplanetary atmospheres.

This mission would seek to determine atmospheric compositions by observing planets and their host stars simultaneously in visible and infrared light over long periods. Most notably, Pandora would examine how variations in a host star’s light impacts exoplanet measurements. This remains a substantial problem in identifying the atmospheric makeup of planets orbiting stars covered in starspots, which can cause brightness variations as a star rotates.

Pandora is a small satellite mission known as a SmallSat, one of three such orbital missions receiving the green light from NASA to move into the next phase of development in the Pioneers program. SmallSats are low-cost spaceflight missions that enable the agency to advance scientific exploration and increase access to space. Pandora would operate in Sun-synchronous low-Earth orbit, which always keeps the Sun directly behind the satellite. This orbit minimizes light changes on the satellite and allows Pandora to obtain data over extended periods. Of the SmallSat concepts selected for further study, Pandora is the only one focused on exoplanets.

“Exoplanetary science is moving from an era of planet discovery to an era of atmospheric characterization,” said Elisa Quintana, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the principal investigator for Pandora. “Pandora is focused on trying to understand how stellar activity affects our measurements of exoplanet atmospheres, which will lay the groundwork for future exoplanet missions aiming to find planets with Earth-like atmospheres.”

Maximizing the scientific potential

Pandora concentrates on studying exoplanetary and stellar atmospheres by surveying planets as they cross in front of – or transit – their host stars. To accomplish this, Pandora would take advantage of a proven technique called transit spectroscopy, which involves measuring the amount of starlight filtering through a planet’s atmosphere, and splitting it into bands of color known as a spectrum. These colors encode information that helps scientists identify gases present in the planet’s atmosphere, and can help determine if a planet is rocky with a thin atmosphere like Earth or if it has a thick gas envelope like Neptune.

This mission, however, would take transit spectroscopy a step further. Pandora is designed to mitigate one of the technique’s most crucial setbacks: stellar contamination. “Stars have atmospheres and changing surface features like spots that affect our measurements,” said Jessie Christiansen, the deputy science lead at the NASA Exoplanet Archive at Caltech in Pasadena, California, and a co-investigator for Pandora. “To be sure we’re really observing an exoplanet’s atmosphere, we need to untangle the planet’s variations from those of the star.”

Pandora would separate stellar and exoplanetary signals by observing them simultaneously in infrared and visible light. Stellar contamination is easier to detect at the shorter wavelengths of visible light, and so obtaining atmospheric data through both infrared and visible light would allow scientists to better differentiate observations coming from exoplanet atmospheres and stars.

“Stellar contamination is a sticking point that complicates precise observations of exoplanets,” said Benjamin Rackham, a 51 Pegasi b Postdoctoral Fellow at the Massachusetts Institute of Technology in Cambridge and a co-investigator for Pandora. “Pandora would help build the necessary tools for disentangling stellar and planetary signals, allowing us to better study the properties of both starspots and exoplanetary atmospheres.”

Sinergy in space

Joining forces with NASA’s larger missions, Pandora would operate concurrently with the James Webb Space Telescope, slated for launch later this year. Webb will provide the ability to study the atmospheres of exoplanets as small as Earth with unprecedented precision, and Pandora would seek to expand the telescope’s research and findings by observing the host stars of previously identified planets over longer periods.

Missions such as NASA’s Transiting Exoplanet Survey Satellite (TESS), Hubble Space Telescope, and the retired Kepler and Spitzer spacecraft have given scientists astonishing glimpses at these distant worlds, and laid a strong foundation in exoplanetary knowledge. These missions, however, have yet to fully address the stellar contamination problem, the magnitude of which is uncertain in previous studies of exoplanetary atmospheres. Pandora seeks to fill these critical gaps in NASA’s understanding of planetary atmospheres and increase the capabilities in exoplanet research. 

“Pandora is the right mission at the right time because thousands of exoplanets have already been discovered, and we are aware of many that are amenable to atmospheric characterization that orbit small active stars,” said Jessie Dotson, an astrophysicist at NASA’s Ames Research Center in California’s Silicon Valley and the deputy principal investigator for Pandora. “The next frontier is to understand the atmospheres of these planets, and Pandora would play a key role in uncovering how stellar activity impacts our ability to characterize atmospheres. It would be a great complement to Webb’s mission.”

A launch pad for exploration

Lawrence Livermore National Laboratory (LLNL), in Livermore, California, is co-leading the Pandora mission with NASA’s Goddard Space Flight Center. LLNL will manage the mission and leverage capabilities developed for other government agencies, including a low-cost approach to the telescope design and fabrication that enables this groundbreaking exoplanet science from a SmallSat platform.

NASA’s Pioneers program, which consists of SmallSats, payloads attached to the International Space Station, and scientific balloon experiments, fosters innovative space and suborbital experiments for early-to-mid-career researchers through low-cost, small hardware missions. Under this new program, Pandora would operate on a five-year timeline with a budget cap of $20 million.

Despite tight constraints, the Pioneers program enables Pandora to concentrate on a focused research question while engaging a diverse team of students and early career scientists from more than a dozen of universities and research institutes. This SmallSat platform creates an excellent blueprint for small-scale missions to make an impact in the astrophysics community.

“Pandora’s long-duration observations in visible and infrared light are unique and well-suited for SmallSats,” said Quintana. “We are excited that Pandora will play a crucial role in NASA’s quest for finding other worlds that could potentially be habitable.”

For more information about the Pioneers program, visit:  https://science.nasa.gov/astrophysics/programs/astrophysics-pioneers

By Anisha Engineer
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Media Contact:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Editor: Rob Garner

Source: NASA/Exoplanets

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Astronomers see a ‘Space Jellyfish’

A composite image of the USS Jellyfish in Abell 2877 showing the optical Digitised Sky Survey (background) with XMM X-ray data (magenta overlay) and MWA 118 MHz radio data (red-yellow overlay). Credit: Torrance Hodgson, ICRAR/Curtin University.Hi-res image

A radio telescope located in outback Western Australia has observed a cosmic phenomenon with a striking resemblance to a jellyfish.

Published today in The Astrophysical Journal, an Australian-Italian team used the Murchison Widefield Array (MWA) telescope to observe a cluster of galaxies known as Abell 2877.

Lead author and PhD candidate Torrance Hodgson, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) in Perth, said the team observed the cluster for 12 hours at five radio frequencies between 87.5 and 215.5 megahertz.

“We looked at the data, and as we turned down the frequency, we saw a ghostly jellyfish-like structure begin to emerge,” he said.

“This radio jellyfish holds a world record of sorts. Whilst it’s bright at regular FM radio frequencies, at 200 MHz the emission all but disappears.

“No other extragalactic emission like this has been observed to disappear anywhere near so rapidly.”

Astronomers see a ‘Space Jellyfish’ from ICRAR on Vimeo

This uniquely steep spectrum has been challenging to explain. “We’ve had to undertake some cosmic archaeology to understand the ancient background story of the jellyfish,” said Hodgson.

“Our working theory is that around 2 billion years ago, a handful of supermassive black holes from multiple galaxies spewed out powerful jets of plasma. This plasma faded, went quiet, and lay dormant.

“Then quite recently, two things happened—the plasma started mixing at the same time as very gentle shock waves passed through the system.

“This has briefly reignited the plasma, lighting up the jellyfish and its tentacles for us to see.”

The jellyfish is over a third of the Moon’s diameter when observed from Earth, but can only be seen with low-frequency radio telescopes.
“Most radio telescopes can’t achieve observations this low due to their design or location,” said Hodgson.

The MWA—a precursor to the Square Kilometre Array (SKA)—is located at CSIRO’s Murchison Radio-astronomy Observatory in remote Western Australia.

The site has been chosen to host the low-frequency antennas for the SKA, with construction scheduled to begin in less than a year.

Tile 107, or “the Outlier” as it is known, is one of 256 tiles of the MWA located 1.5km from the core of the telescope. The MWA is a precursor instrument to the SKA. Photographed by Pete Wheeler, ICRAR.

Professor Johnston-Hollitt, Mr Hodgson’s supervisor and co-author, said the SKA will give us an unparalleled view of the low-frequency Universe.

“The SKA will be thousands of times more sensitive and have much better resolution than the MWA, so there may be many other mysterious radio jellyfish waiting to be discovered once it’s operational.

“We’re about to build an instrument to make a high resolution, fast frame-rate movie of the evolving radio Universe. It will show us from the first stars and galaxies through to the present day,” she said.

“Discoveries like the jellyfish only hint at what’s to come, it’s an exciting time for anyone seeking answers to fundamental questions about the cosmos.”

Composite image of the SKA-Low telescope in Western Australia. The image blends a real photo (on the left) of the SKA-Low prototype station AAVS2.0 which is already on site, with an artists impression of the future SKA-Low stations as they will look when constructed. These dipole antennas, which will number in their hundreds of thousands, will survey the radio sky in frequencies as low at 50Mhz. Credit ICRAR and SKAO.

Original Publication 

‘Ultra-Steep Spectrum Radio Jellyfish Uncovered in Abell 2877’, published in The Astrophysical Journal on March 18^th, 2021.

More Infor: 

ICRAR

The International Centre for Radio Astronomy Research (ICRAR) is a joint venture between Curtin University and The University of Western Australia with support and funding from the State Government of Western Australia.

Murchison Widefield Array

The Murchison Widefield Array (MWA) is a low-frequency radio telescope and is the first of four Square Kilometre Array (SKA) precursors to be completed. A consortium of partner institutions from seven countries (Australia, USA, India, New Zealand, Canada, Japan, and China) financed the development, construction, commissioning, and operations of the facility. The MWA consortium is led by Curtin University.

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Contacts

 

Professor Melanie Johnston-Hollitt (ICRAR / Curtin University)

Ph: +61 400 951 815                

E: Melanie.Johnston-Hollitt@curtin.edu.au

 

Pete Wheeler (Media Contact, ICRAR)

Ph: +61 423 982 018               

E: Pete.Wheeler@icrar.org

 

Vanessa Beasley (Media Contact, Curtin University) 

Ph: +61 8 9266 1811

E: Vanessa.Beasley@curitn.edu.au

 

Source:  International Centre for Radio Astronomy Research (ICRAR)/News

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Discovery of a Mystery Hidden in Chamaeleon

Artist's illustration of a symbiotic binary in outburst
Credit: NASA, ESA, and D. Berry (STScI)

“One of the advantages to being disorganized is that one is always having surprising discoveries.” —A.A. Milne

So begins a recent publication exploring the mystery of CN Cha, an unexpected discovery found in the “disorganization” of vast archives of data. What did we find, and how can we learn from it? The story starts with an unexpectedly luminous star in the Gaia mission’s second data release.

A comparison of two images of CN Cha (red crosshairs), the top taken in April 1991 and the bottom in June 2016
Credit: Adapted from Lancaster et al. 2020

Morphing Appearances

CN Cha is a star located in the direction of the Chamaeleon constellation. This object was first recorded in 1963 as a Mira variable — a massive red-giant star that varies in luminosity regularly as the star expands and contracts.

But when a team of scientists led by Lachlan Lancaster (Princeton University) combed through a recent Gaia catalog looking for interesting bright and distant objects for spectroscopic follow-up, they found a different description of CN Cha: an unusually luminous star that’s not variable.

What followed for Lancaster and collaborators was a detailed dive into decades of archival photometric data — data produced by more than a dozen different observatories and ranging from infrared to ultraviolet wavelengths.

An Eruptive History

By cobbling together this archival data, Lancaster and collaborators were also able to piece together CN Cha’s unusual story.

CN Cha started out with all the properties of a Mira variable star — but then, in 2013, it underwent a spectacular outburst, brightening by about 8 optical magnitudes. For roughly 3 years, it maintained this brightened state, before starting to dim at a rate of 1.4 magnitudes per year.

The authors use this history and new spectroscopic observations to identify the most likely explanation for this mystery: CN Cha is probably a symbiotic binary system that recently experienced a long-duration nova eruption.

 

Photometry from the ASAS (black), APASS (light-blue) and the ASAS–SN (pink) surveys showing the outburst and 3-year plateau in CN Cha’s optical luminosity. Credit: Adapted from Lancaster et al. 2020.

Puzzling Behavior

Symbiotic binaries consist of an evolved star — in the case of CN Cha, presumably a Mira variable — in an orbit with a white dwarf. As mass is transferred onto the white dwarf, it can ignite thermonuclear fusion, causing the system to go into outburst.

The identification of CN Cha as a slow symbiotic nova is intriguing because there are only a few known examples of these outbursts. And though most of CN Cha’s properties are perfectly consistent with those of other slow symbiotic novae, the 3-year extent of its optical brightness plateau is unusually short for this class of transients: one to several decades is more common.

 

The Vera Rubin Observatory, pictured under construction in this image from May 2019, will soon be a new source of large quantities of time-domain survey data. Credit: LSST Project/NSF/AURA

Organizing the Future

So what can we learn from this mysterious source? First, further study of CN Cha may provide valuable insights into symbiotic novae, the evolution of stars in the galactic thick disk, and even the possible progenitors of Type Ia supernova eruptions.

But what’s more, CN Cha’s story underscores how many discoveries are still hidden in the vast — and rapidly growing — quantities of human-collected astronomical data.

The astronomy community is making strides toward developing better systems and tools that centralize different data archives and make them accessible and searchable. Perhaps as we become more organized, stories like CN Cha’s will become routine rather than surprising.

Citation

“A Mystery in Chamaeleon: Serendipitous Discovery of a Galactic Symbiotic Nova,” Lachlan Lancaster et al 2020 AJ 160 125. doi:10.3847/1538-3881/aba435

 By Susanna Kohler

Source: American Astronomical Society (AAS Nova)

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