SPACE
Rare, double-lobe nebula resembles overflowing cosmic ‘jug’
Gemini South captures the spectacular end-of-life display of a red-giant star
Reports and ProceedingsIMAGE: A BILLOWING PAIR OF NEARLY SYMMETRICAL LOOPS OF DUST AND GAS MARK THE DEATH THROES OF AN ANCIENT RED-GIANT STAR, AS CAPTURED BY GEMINI SOUTH, ONE HALF OF THE INTERNATIONAL GEMINI OBSERVATORY, OPERATED BY NSF’S NOIRLAB. THE RESULTING STRUCTURE, SAID TO RESEMBLE AN OLD STYLE OF ENGLISH JUG, IS A RARELY SEEN BIPOLAR REFLECTION NEBULA. EVIDENCE SUGGESTS THAT THIS OBJECT FORMED BY THE INTERACTIONS BETWEEN THE DYING RED GIANT AND A NOW-SHREDDED COMPANION STAR. THE IMAGE WAS OBTAINED BY NOIRLAB’S COMMUNICATION, EDUCATION & ENGAGEMENT TEAM AS PART OF THE NOIRLAB LEGACY IMAGING PROGRAM. view more
CREDIT: INTERNATIONAL GEMINI OBSERVATORY/NOIRLAB/NSF/AURA IMAGE PROCESSING: T.A. RECTOR (UNIVERSITY OF ALASKA ANCHORAGE/NSF’S NOIRLAB), J. MILLER (GEMINI OBSERVATORY/NSF’S NOIRLAB), M. RODRIGUEZ (GEMINI OBSERVATORY/NSF’S NOIRLAB), M. ZAMANI (NSF’S NOIRLAB)
The glowing nebula IC 2220, nicknamed the Toby Jug Nebula owing to its resemblance to an old English drinking vessel, is a rare astronomical find. This reflection nebula, located about 1200 light-years away in the direction of the constellation Carina (the keel), is a double-lobed, or bipolar, cloud of gas and dust created and illuminated by the red-giant star at its center. This end-of-life phase of red giant stars is relatively brief, and the celestial structures that form around them are rare, making the Toby Jug Nebula an excellent case study into stellar evolution.
This image, captured by the Gemini South telescope, one half of the International Gemini Observatory, operated by NSF’s NOIRLab, showcases the Toby Jug Nebula’s magnificent, nearly symmetrical double-looped structure and glowing stellar heart. These features are unique to red giants transitioning from aging stars to planetary nebulae [1] and therefore offer astronomers valuable insight into the evolution of low- to intermediate-mass stars nearing the end of their lives as well as the cosmic structures they form.
At the heart of the Toby Jug Nebula is its progenitor, the red-giant star HR3126. Red giants form when a star burns through its supply of hydrogen in its core. Without the outward force of fusion, the star begins to contract. This raises the core temperature and causes the star to then swell up to 400 times its original size. Though HR3126 is considerably younger than our Sun — a mere 50 million years old compared to the Sun’s 4.6 billion years — it is five times the mass. This allowed the star to burn through its hydrogen supply and become a red giant much faster than the Sun.
As HR 3126 swelled, its atmosphere expanded and it began to shed its outer layers. The expelled stellar material flowed out into the surrounding area, forming a magnificent structure of gas and dust that reflects the light from the central star. Detailed studies of the Toby Jug Nebula in infrared light have revealed that silicon dioxide (silica) is the most likely compound reflecting HR3126’s light.
Astronomers theorize that bipolar structures similar to those seen in the Toby Jug Nebula are the result of interactions between the central red giant and a binary companion star. Previous observations, however, found no such companion to HR3126. Instead, astronomers observed an extremely compact disk of material around the central star. This finding suggests that a former binary companion was possibly shredded into the disk, which may have triggered the formation of the surrounding nebula.
In about five billion years from now, when our Sun has burned through its supply of hydrogen, it too will become a red giant and eventually evolve into a planetary nebula. In the very distant future, all that will be left of our Solar System will be a nebula as vibrant as the Toby Jug Nebula with the slowly cooling Sun at its heart.
The image was processed by NOIRLab’s Communication, Education & Engagement team as part of the NOIRLab Legacy Imaging Program. The observations were made with Gemini South on Cerro Pachón in Chile using one of the dual Gemini Multi-Object Spectrographs (GMOS). Though spectrographs are designed to split light into various wavelengths for study, the GMOS spectrographs also have powerful imaging capabilities, as demonstrated by this exceptional view of the Toby Jug Nebula.
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[1] The term “planetary nebulae” is a misnomer; they are unrelated to planets. The term was likely first used in the 1780s by astronomer William Herschel, who noted their seemingly round, planet-like shape when observed through early telescopes.
NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory), the US center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (operated in cooperation with the Department of Energy’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O'odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.
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Astronomers identify the coldest star yet that emits radio waves
Cooler than a campfire and smaller than Jupiter, this brown dwarf star is a rare find
IMAGE: AN IMAGE DISPLAYING THE RELATIVE SIZE OF A TYPICAL BROWN DWARF STAR. IN THE INSTANCE OF THE STAR IN THIS STUDY, THE BROWN DWARF IS SMALLER THAN JUPITER (BETWEEN 0.65 AND 0.95 ITS RADIUS) BUT IS MORE MASSIVE, SOMEWHERE BETWEEN FOUR AND 44 TIMES THE MASS OF JUPITER. view more
CREDIT: NASA/JPL
Astronomers at the University of Sydney have shown that a small, faint star is the coldest on record to produce emission at radio wavelength.
The ‘ultracool brown dwarf’ examined in the study is a ball of gas simmering at about 425 degrees centigrade – cooler than a typical campfire – without burning nuclear fuel.
By contrast, the surface temperature of the Sun, a nuclear inferno, is about 5600 degrees.
While not the coldest star ever found, it is the coolest so far analysed using radio astronomy. The findings are published today in The Astrophysical Journal Letters.
Lead author and PhD student in the School of Physics, Kovi Rose, said: “It’s very rare to find ultracool brown dwarf stars like this producing radio emission. That’s because their dynamics do not usually produce the magnetic fields that generate radio emissions detectable from Earth.
“Finding this brown dwarf producing radio waves at such a low temperature is a neat discovery.”
“Deepening our knowledge of ultracool brown dwarfs like this one will help us understand the evolution of stars, including how they generate magnetic fields.”
How the internal dynamics of brown dwarfs sometimes produce radio waves is something of an open question. While astronomers have a good idea how larger ‘main sequence’ stars like the Sun generate magnetic fields and radio emissions, it is still not fully known why fewer than 10 percent of brown dwarf stars produce such emission.
The rapid rotation of ultracool dwarfs is thought to play a part in generating their strong magnetic fields. When the magnetic field rotates at a different speed to the dwarf’s ionised atmosphere, it can create electrical current flows.
In this instance, it is thought the radio waves are being produced by the inflow of electrons to the magnetic polar region of the star, which, coupled with the rotation of the brown dwarf star, is producing regularly repeating radio bursts.
Brown dwarf stars, so called as they give off little energy or light, are not massive enough to ignite the nuclear fusion associated with other stars like our Sun.
Mr Rose said: “These stars are a kind of missing link between the smallest stars that burn hydrogen in nuclear reactions and the largest gas giant planets, like Jupiter.
The star, with the catchy name T8 Dwarf WISE J062309.94−045624.6, is located about 37 light years from Earth. It was discovered in 2011 by astronomers at Caltech in the United States.
The star’s radius is between 0.65 and 0.95 that of Jupiter. Its mass is not well understood but is at least four times more massive than Jupiter but no more than 44 times more massive. The Sun is 1000 times more massive than Jupiter.
The analysis of the star was made by Mr Rose using new data from the CSIRO ASKAP telescope in Western Australia and followed up with observations from the Australia Telescope Compact Array near Narrabri in NSW and the MeerKAT telescope in South Africa.
Professor Tara Murphy, co-author and Head of the School of Physics at the University of Sydney, said: “We've just started full operations with ASKAP and we're already finding a lot of interesting and unusual astronomical objects, like this.
“As we open this window on the radio sky, we will improve our understanding of the stars around us, and the potential habitability of exoplanet systems they host.”
DOWNLOAD photos at this link.
INTERVIEWS
Kovi Rose | kovi.rose@sydney.edu.au || Prof Tara Murphy | tara.murphy@sydney.edu.au
MEDIA ENQUIRIES Marcus Strom | +61 423 982 485 | marcus.strom@sydney.edu.au
DECLARATION Researchers declare no conflicts.
ACKNOWLEDGEMENTS
The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. CSIRO’s ASKAP radio telescope is part of the Australia Telescope National Facility (ATNF). Operation of ASKAP is funded by the Australian Government with support from the National Collaborative Research Infrastructure Strategy. ASKAP uses the resources of the Pawsey Supercomputing Research Centre. Establishment of ASKAP, Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory and the Pawsey Supercomputing Research Centre are initiatives of the Australian Government, with support from the Government of Western Australia and the Science and Industry Endowment Fund. The Australia Telescope Compact Array is part of the ATNF which is funded by the Australian Government for operation as a National Facility managed by CSIRO. We acknowledge the Gomeroi people as the Traditional Owners of the Observatory site. This publication makes use of data products from the Wide-field Infrared Survey Explorer (WISE), which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration.
JOURNAL
The Astrophysical Journal Letters
METHOD OF RESEARCH
Data/statistical analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Periodic Radio Emission from the T8 Dwarf WISE J062309.94–045624.6
ARTICLE PUBLICATION DATE
13-Jul-2023
When the stars align: Astronomers find answers to mysterious action of ghost stars in our Galaxy
IMAGE: A NOW ICONIC COLLAGE SHOWING 22 INDIVIDUAL WELL-KNOWN PNE, ARTISTICALLY ARRANGED IN A SPIRAL PATTERN BY ORDER OF APPROXIMATE PHYSICAL SIZE. view more
CREDIT: ESA/HUBBLE AND NASA, ESO, NOAO/AURA/NSF FROM AN IDEA BY THE CORRESPONDING AUTHOR AND IVAN BOJIČIĆ AND RENDERED BY IVAN BOJIČIĆ WITH INPUT FROM DAVID FREW AND THE AUTHOR.
A collaboration of scientists from The University of Manchester and the University of Hong Kong have found a source for the mysterious alignment of stars near the Galactic Centre.
The alignment of planetary nebulae was discovered ten years ago by a Manchester PhD student, Bryan Rees, but has remained unexplained.
New data obtained with the European Southern Observatory Very Large Telescope in Chile and the Hubble Space Telescope, published in Astrophysical Journal Letters, has confirmed the alignment but also found a particular group of stars that is responsible, namely close binary stars.
Planetary nebulae are clouds of gas that are expelled by stars at the end of their lives - the Sun will also form one about five billion years from now. The ejected clouds are ‘ghosts’ of their dying stars and they form beautiful structures such as an hourglass or butterfly shape.
The team studied a group of so-called planetary nebulae found in the Galactic Bulge near the centre of our Milky Way. Each of these nebulae are unrelated and come from different stars, which were born at different times, and spend their lives in completely different places. However, the study found that many of their shapes line up in the sky in the same way and are aligned almost parallel to the Galactic plane (our Milky Way).
This is in the same direction as found by Bryan Rees a decade ago.
The new research, led by Shuyu Tan, a student at the University of Hong Kong, found that the alignment is present only in planetary nebulae which have a close stellar companion. The companion star orbits the main star at the centre of the planetary nebulae in an orbit closer than Mercury is to our own Sun.
The planetary nebulae that do not show close companions do not show the alignment, which suggests that the alignment is potentially linked to the initial separation of the binary components at the time of the star’s birth.
Albert Zijlstra, co-author and Professor in Astrophysics at The University of Manchester, said: “This finding pushes us closer to understanding the cause for this mysterious alignment.
“Planetary nebulae offer us a window into the heart of our galaxy and this insight deepens our understanding of the dynamics and evolution of the Milky Way’s bulge region.
“The formation of stars in the bulge of our galaxy is a complex process that involves various factors such as gravity, turbulence, and magnetic fields. Until now, we have had a lack of evidence for which of these mechanisms could be causing this process to happen and generating this alignment.
“The significance in this research lies in the fact that we now know that the alignment is observed in this very specific subset of planetary nebulae.”
The researchers investigated 136 confirmed planetary nebulae in the galaxy bulge – the thickest section of our Milky Way composed of stars, gas and dust - using the European Southern Observatory Very Large Telescope, which has a main mirror diameter of eight metres.
They also re-examined and re-measured 40 of these from the original study using images from the high-resolution Hubble Space Telescope.
Prof Quentin Parker, the corresponding author from the University of Hong Kong, suggests the nebulae may be shaped by the rapid orbital motion of the companion star, which may even end up orbiting inside the main star.
The alignment of the nebulae may mean that the close binary system preferentially forms with their orbits in the same plane.
Although further studies are needed to fully understand the mechanisms behind the alignment, the findings provide important evidence for the presence of a constant and controlled process that has influenced star formation over billions of years and vast distances.
JOURNAL
The Astrophysical Journal Letters
ARTICLE TITLE
When the Stars Align: A 5 σ Concordance of Planetary Nebulae Major Axes in the Centre of our Galaxy
ARTICLE PUBLICATION DATE
13-Jul-2023
James Webb Telescope catches glimpse of possible first-ever ‘dark stars’
Stars powered with dark matter still need proving but could reveal clues about the nature of one of the universe’s great mysteries
IMAGE: THESE THREE OBJECTS (JADES-GS-Z13-0, JADES-GS-Z12-0, AND JADES-GS-Z11-0) WERE ORIGINALLY IDENTIFIED AS GALAXIES IN DECEMBER 2022 BY THE JWST ADVANCED DEEP EXTRAGALACTIC SURVEY (JADES). NOW, A TEAM INCLUDING KATHERINE FREESE AT THE UNIVERSITY OF TEXAS AT AUSTIN SPECULATE THEY MIGHT ACTUALLY BE “DARK STARS,” THEORETICAL OBJECTS MUCH BIGGER AND BRIGHTER THAN OUR SUN, POWERED BY PARTICLES OF DARK MATTER ANNIHILATING. view more
CREDIT: IMAGE CREDIT: NASA/ESA
Stars beam brightly out of the darkness of space thanks to fusion, atoms melding together and releasing energy. But what if there’s another way to power a star?
A team of three astrophysicists — Katherine Freese at The University of Texas at Austin, in collaboration with Cosmin Ilie and Jillian Paulin ’23 at Colgate University — analyzed images from the James Webb Space Telescope (JWST) and found three bright objects that might be “dark stars,” theoretical objects much bigger and brighter than our sun, powered by particles of dark matter annihilating. If confirmed, dark stars could reveal the nature of dark matter, one of the deepest unsolved problems in all of physics.
“Discovering a new type of star is pretty interesting all by itself, but discovering it’s dark matter that’s powering this—that would be huge,” said Freese, director of the Weinberg Institute for Theoretical Physics and the Jeff and Gail Kodosky Endowed Chair in Physics at UT Austin.
Although dark matter makes up about 25% of the universe, its nature has eluded scientists. Scientists believe it consists of a new type of elementary particle, and the hunt to detect such particles is on. Among the leading candidates are Weakly Interacting Massive Particles. When they collide, these particles annihilate themselves, depositing heat into collapsing clouds of hydrogen and converting them into brightly shining dark stars. The identification of supermassive dark stars would open up the possibility of learning about the dark matter based on their observed properties.
The research is published in the Proceedings of the National Academy of Sciences.
Follow-up observations from JWST of the objects’ spectroscopic properties — including dips or excess of light intensity in certain frequency bands — could help confirm whether these candidate objects are indeed dark stars.
Confirming the existence of dark stars might also help solve a problem created by JWST: There seem to be too many large galaxies too early in the universe to fit the predictions of the standard model of cosmology.
“It’s more likely that something within the standard model needs tuning, because proposing something entirely new, as we did, is always less probable,” Freese said. “But if some of these objects that look like early galaxies are actually dark stars, the simulations of galaxy formation agree better with observations.”
The three candidate dark stars (JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0) were originally identified as galaxies in December 2022 by the JWST Advanced Deep Extragalactic Survey (JADES). Using spectroscopic analysis, the JADES team confirmed the objects were observed at times ranging from about 320 million to 400 million years after the Big Bang, making them some of the earliest objects ever seen.
“When we look at the James Webb data, there are two competing possibilities for these objects,” Freese said. “One is that they are galaxies containing millions of ordinary, population-III stars. The other is that they are dark stars. And believe it or not, one dark star has enough light to compete with an entire galaxy of stars.”
Dark stars could theoretically grow to be several million times the mass of our sun and up to 10 billion times as bright as the sun.
“We predicted back in 2012 that supermassive dark stars could be observed with JWST,” said Ilie, assistant professor of physics and astronomy at Colgate University. “As shown in our recently published PNAS article, we already found three supermassive dark star candidates when analyzing the JWST data for the four high redshift JADES objects spectroscopically confirmed by Curtis-Lake et al, and I am confident we will soon identify many more.”
The idea for dark stars originated in a series of conversations between Freese and Doug Spolyar, at the time a graduate student at the University of California, Santa Cruz. They wondered: What does dark matter do to the first stars to form in the universe? Then they reached out to Paolo Gondolo, an astrophysicist at the University of Utah, who joined the team. After several years of development, they published their first paper on this theory in the journal Physical Review Letters in 2008.
Together, Freese, Spolyar and Gondolo developed a model that goes something like this: At the centers of early protogalaxies, there would be very dense clumps of dark matter, along with clouds of hydrogen and helium gas. As the gas cooled, it would collapse and pull in dark matter along with it. As the density increased, the dark matter particles would increasingly annihilate, adding more and more heat, which would prevent the gas from collapsing all the way down to a dense enough core to support fusion as in an ordinary star. Instead, it would continue to gather more gas and dark matter, becoming big, puffy and much brighter than ordinary stars. Unlike ordinary stars, the power source would be evenly spread out, rather than concentrated in the core. With enough dark matter, dark stars could grow to be several million times the mass of our sun and up to 10 billion times as bright as the sun.
Funding for this research was provided by the U.S. Department of Energy’s Office of High Energy Physics program and the Vetenskapsradet (Swedish Research Council) at the Oskar Klein Centre for Cosmoparticle Physics at Stockholm University.
JOURNAL
Proceedings of the National Academy of Sciences
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Supermassive Dark Star candidates seen by JWST
ARTICLE PUBLICATION DATE
13-Jul-2023
Exploring dark matter and the first bright galaxies simultaneously: 21-cm forest probe may unlock secrets of early universe
IMAGE: EXPLORING DARK MATTER AND THE FIRST GALAXIES SIMULTANEOUSLY WITH THE 21-CM FOREST view more
CREDIT: NAOC & NEU
The mystery of the first galaxies of the universe is an indomitable urge of human beings. The formation of them is mastered by the nature of dark matter which is also one of the most important problems faced by fundamental physics. However, understanding the nature of dark matter—for example, whether it is cold or warm—and its subsequent effect on the first galaxy formation is a huge challenge.
Now, a joint research team from Northeastern University (China) and the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) has proposed using a novel probe to try to shed light on the nature of dark matter and the early formation of galaxies simultaneously.
The team's study was published in Nature Astronomy on July 6.
One way of understanding dark matter is to try to measure the mass of dark matter particles through cosmological observations of small-scale structures. But detecting small-scale structures in which no star formation has ever occurred is difficult, especially during the cosmic dawn. Fortunately, atomic hydrogen gas in and around these dark, small structures from cosmic dawn creates 21-cm absorption lines along the lines of sight between Earth and high-redshift radio point sources. These absorption lines are known collectively as the 21-cm forest.
The 21-cm forest probe is a theoretical concept proposed more than 20 years to probe for gas temperatures and potentially for dark matter properties during the cosmic dawn. So far, scientists have not attempted to actually use the probe due to numerous challenges, including extremely weak signals, the difficulty in identifying high-redshift background sources, and the degeneracy between the mass of dark matter particles and the heating effect, which would prevent the probe from constraining either the particle mass or the heating effect from the first galaxies.
Recently, though, a number of high-redshift radio-loud quasars have been discovered. In addition, construction on the Square Kilometre Array (SKA)—an international initiative to build the world's largest radio telescope—began last December. Both these developments suggest that using the 21-cm forest probe will soon be feasible.
Inspired by power spectrum analyses widely used in cosmological probes, the NAOC researchers realized that the distinctive scale-dependences of the signals caused by the warm dark matter effect and the heating effect, respectively, could be used to statistically extract key features to distinguish the two effects.
In this study, the researchers proposed a novel statistical solution to simultaneously solve the weak signal problem and the degeneracy problem, by measuring the one-dimensional (1-D) power spectrum of the 21-cm forest. The signal scale-dependence revealed by the amplitude and shape of the 1-D power spectrum makes the 21-cm forest probe a viable and effective means of simultaneously measuring dark matter properties and the thermal history of the Universe.
"By measuring the one-dimensional power spectrum of the 21-cm forest, we can not only make the probe actually feasible by increasing the sensitivity, but also provide a way to distinguish the effects of warm dark matter models and early heating process," said XU Yidong, corresponding author of the study. "We will be able to kill two birds with one stone!"
In scenarios where cosmic heating is not too severe, SKA Phase 1's low-frequency array will be capable of effectively constraining both dark matter particle mass and gas temperature. In cases where cosmic heating is more significant, utilizing multiple background radio sources during SKA Phase 2 will enable robust detection capabilities.
The 21-cm forest offers a viable means for constraining dark matter at redshift ranges beyond the reach of other observations. By measuring the heating level, the 21-cm forest provides a way to constrain the spectral properties of the first galaxies and the first black holes, so as to shed light on the nature of the first bright objects in the Universe. Using the 21-cm forest probe will serve as an indispensable avenue for advancing our understanding of the early Universe and peering into the mysteries of both dark matter and the first galaxies.
Since application of the 21-cm forest probe is closely tied to observations of high-redshift background radio sources, the next step will also involve identifying more radio-bright sources at the cosmic dawn (such as radio-loud quasars and gamma-ray burst afterglows) that can be followed up in the SKA era.
JOURNAL
Nature Astronomy
ARTICLE TITLE
The 21-cm forest as a simultaneous probe of dark matter and cosmic heating history
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