Dedicated to spreading the Good News of Basic and Applied Science at great research institutions world wide. Good science is a collaborative process. The rule here: Science Never Sleeps.
Authors: V. Squicciarini, R. Gratton, M. Janson, et al.
First Author’s Institution: Department of Physics and Astronomy, University of Padova, Padova, Italy
Status: Published in Astronomy & Astrophysics [open access]
Tiny Homelands
In the decades since 51 Pegasi b, the first exoplanet around a solar-type star, was discovered in 1995, thousands of exoplanets have been identified. However, the majority of the known exoplanets were discovered based on the radial velocity and transit methods, which are only sensitive to exoplanets close to their host stars.
Thus, current observations on exoplanets are greatly biased. For some stars, especially those with a low mass, The formation of close-in giant planets can be explained by core accretion theory through the growth of a dust core. But things are quite different for massive stars: giant planets tend to far from their parents. The massive disk of the central massive star allows giant planets to form in a remote area through gravitational instability, while near the central star, dust for planet formation are likely to be blown away by strong stellar wind or destroyed by UV and X-ray radiation in a short time. The direct imaging is undoubtedly the best method to search for giant exoplanets in large separations.
Different from previous direct imaging surveys targeting stars with spectral type no earlier than A, the B-star Exoplanet Abundance Study (BEAST) survey first aims at more massive ones. The second planetary system the survey found belongs to the massive star μ2 Scorpii (μ2 Sco). μ2 Sco, also known as HR 6252, HD 151985, or HIP 82545, is a member of Scorpius-Centaurus association about 400 light years from us. Based on the data of Gaia DR2 and photometry in from a previous study, it is considered a B2IV star with a mass of ~9 M⊙, indicating it will probably end its life as a supernova. To image the system, Its bright radiation is masked by the coronagraph to outline its faint companions, and the adaptive optics system in the SPHERE on the ESO Very Large Telescope provides high angular resolution.
With two epochs of observation in 2018 and 2021 respectively, background sources visible in both epochs can be excluded through their null proper motion and others are judged according to their colors. Finally, only 2 companion candidates remain, named CC0 and CC2. The probability that these two objects are high proper motion background stars or isolated brown dwarfs are calculated and turn out to be negligible.
CC0 is located only 21 ± 1 AU from the host star and is covered by the Integral Field Spectrograph (IFS), which allows a spatially resolved spectroscopy. The authors have not completely confirmed its existence yet, as it is just on the edge of the coronagraphic mask (Figure 1). But at least, they excluded the possibility of speckles, because the separation between a speckle and μ2 Sco should be in proportion to wavelength while for CC0 it is constant. Spectral fittings of two models give the mass of CC0 18.5 ± 1.5 MJ (mass of Jupiter) and an equilibrium temperature ~900 K. The detection of CC2 is definite, and thus CC2 is also named μ2 Sco b as the first confirmed companion of μ2 Sco. Because CC2 has a separation of 290 ± 10 AU, out of the field of view of IFS, its physical parameters are estimated through its color-magnitude diagram using two bands of SPHERE’s dual-band imager IRDIS (Figure 2). The result shows a substellar object with a spectral type L0-L2. The fitting of the photometry suggests the mass of CC2 is 14.4 ± 0.8 MJ.
Figure 1: IFS images of μ2 Sco (left panel: first epoch; right panel: second epoch). CC0 is circled in white. The star in the center is masked, and the point-like source in the lower left of the first epoch image is a background star.
Figure 2: IRDIS images of μ2 Sco (left panel: first epoch; right panel: second epoch). CC2 is circled in white. Other point-like sources in the field of view are background stars.
The high-resolution images also show the positions of CC0 and CC2 shifted ~20 mas and ~10 mas, respectively, between 2018 and 2021. The angular position of CC0 changed ~11° and the distance from CC2 to the host star, μ2 Sco, changed ~5 mas over the years. Based on the position difference, the orbital parameters of the two objects were fitted (table 1) and an MCMC chain named orbitize! was applied to predict the orbits, which are shown in Figure 4. Also, the authors showed that CC0 and CC2 share the same parent and the best-fit orbits are Hill stable (can remain dynamically stable in a long timescale) despite large eccentricities.
Planets or brown dwarfs?
Figure 3: Relation between mass ratio and irradiation of known exoplanets and Solar System planets. CC2 has a similar mass ratio and irradiation to Jupiter, while CC0 has a higher irradiation. Here only shows exoplanets with a parent whose mass is known to a precision of over 30 percent. Most exoplanets are detected by radial velocity (red) and transit methods (green). Imaging (blue) fills the gap of planets with high host star mass ratio and low irradiation.
Strictly speaking, CC0 and CC2 can be considered brown dwarfs rather than planets, as their masses exceed the deuterium-burning limit (M ∼13 MJ). However, the mass ratio of them to their host star (0.0015 and 0.0019) are similar to that of Jupiter to and the Sun (0.00095). Moreover, the mean irradiation of CC0 and CC2 are like Mercury and Jupiter, respectively. Thus, the μ2 Sco system appears to be a large-size Solar System. This is probably not an individual case as b Cen b, the first exoplanet BEAST discovered, is ~11 MJ around the binary system b Cen (5.5+3.5 M⊙) and the mass ratio is 0.0013. So, is the μ2 Sco system a planetary system or a multiple stellar system? Its similarity to the Solar System indicates mass is probably not the only criterion. The authors suggest that the formation pathway may be a key factor. The giant planets or brown dwarfs around a very low mass star are probably the results of turbulent fragmentation within the natal molecular cloud, which should be labeled as “star-like”. Otherwise, the system is probably “planet-like”, especially when there is evidence that companions are originated from protoplanetary disks, including a low planet-to-star mass ratio or orbits with resonance. In this case, both CC2 and b Cen b should be regarded as planets, no matter what their masses are.
Figure 4: Fitting results of absolute magnitudes (two bands), mass, projected separation, and orbital elements (semi-major axis, eccentricity, and inclination) of CC2 and CC0. Both have a high eccentricity.
Figure 5: Possible orbits of CC2 (upper) and CC0 (lower) given by MCMC chains. The yellow star is their parent μ2 Sco, and the orange stars are positions of CC0 and CC2 in two epochs. For CC2, the displacement is not evident. Panels in the right show the changes of position angles and distances from the central star between two epochs.
A classical core-accretion scenario cannot explain the existence of CC0 and CC2, as it takes millions of years to form a giant planet, but the UV and X-ray radiation of a B star can destroy its disk in ~105 years. The gravitational instability model allows giant planets to form in wide orbits within 104 years, and then some move closer to the host star through rapid migration. This is consistent with the analysis of CC0 and CC2 that their orbits tend to have high eccentricities. However, recent updates of the core-accretion model allow CC0 and CC2 to form close to μ2 Sco and migrate to their current position later. Thus, more observations are needed in the following years to confirm the existence of CC0 and further constrain the orbits of the system.
Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
Why read Astrobites?
Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.
Full identification of an astronomical asset will be presented once in the first instance of that asset.
A groundbreaking study using ALMA paves the way for a deeper understanding of dark matter’s true nature.
Figure 1. Detected fluctuations of dark matter. The brighter orange color indicates regions with high dark matter density and the darker orange color indicates regions with low dark matter density. The white and blue colors represent gravitationally lensed objects observed by ALMA. (Credit: ALMA (ESO/NAOJ/NRAO), K.T. Inoue et al.)
A conceptual diagram of the gravitational lens system MG J0414+0534. The object at the center of the image indicates the lensing galaxy. The orange color shows dark matter in the intergalactic space, and the pale yellow color indicates dark matter in the lensing galaxy. (Credit: NAOJ, K.T. Inoue)
A research team led by Professor Kaiki Taro Inoue at Kindai University in Osaka, Japan, has used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to make an unprecedented discovery. The team has found fluctuations in dark matter distribution in the Universe on a scale smaller than that of massive galaxies.
This is the first time that the spatial fluctuations of dark matter in the far Universe have been detected on scales less than 30,000 light-years. This result shows that cold dark matter [1] is favored even on scales smaller than massive galaxies and is an essential step toward understanding the true nature of dark matter. The article was published in The Astrophysical Journal [below] on September 7th.
Dark matter, the invisible material that makes up a significant fraction of the mass of the Universe, is thought to have played an important role in the formation of structures such as stars and galaxies [2]. Since dark matter is not uniformly distributed in space but in clumps, its gravity can slightly change the path of light (including radio waves) from distant light sources. Observations of this effect (gravitational lensing) have shown that dark matter is associated with relatively massive galaxies and clusters of galaxies. However, how it is distributed at smaller scales is unknown.
Using the exceptional observational power of ALMA, the research team focused on a distant quasar [3], MG J0414+0534 [4], situated 11 billion light-years away from Earth. This particular quasar displays a rare quadruple image thanks to the gravitational lensing effects of a galaxy in the foreground. However, the positions and shapes of these images did not match calculations based purely on the foreground galaxy’s gravitational pull, indicating another influence at play.
Further investigation revealed the source of this discrepancy: the effects of dark matter on a scale smaller than that of large galaxies—specifically, less than 30,000 light-years. These findings confirmed and enriched the theoretical model of cold dark matter. According to the theory, these clumps of dark matter are distributed not just within galaxies (as represented by the pale yellow color in Figure 2) but also in intergalactic spaces (shown in orange in Figure 2).
The challenge lay in the fact that the gravitational lensing effects induced by these tiny clumps of dark matter are complicated to detect on their own. However, the high-resolution capabilities of ALMA, coupled with the lensing effect of the foreground galaxy, enabled this pioneering detection. Therefore, this research is a significant step toward verifying dark matter theories and further unraveling its enigmatic nature.
This work was supported by Grant-in-Aids for Scientific Research from the Japan Society for the Promotion of Science (Nos. 17H02868, 19K03937), the National Astronomical Observatory of Japan ALMA Joint Scientific Research Project 2018-07A, the same ALMA J A P A N Research Fund NAOJ-ALMA-256, and Taiwan MoST 103-2112-M-001-032-MY3, 106-2112-M-001-011, 107-2119-M-001-020, 107-2119-M-001-020.
Notes:
[1] As the Universe expands, the density of matter decreases. Thus, particles of dark matter (matter that is invisible to light) will no longer encounter other particles and will have independent motion different from the movement of ordinary matter. In this case, dark matter particles that move at a speed far less than the speed of light with respect to ordinary matter are called cold dark matter. Because of the low velocity, it cannot erase the small-scale structures in the Universe.
[2] In the early Universe, stars and galaxies are thought to have been formed by the gravitational growth of density fluctuations of dark matter and the aggregation of hydrogen and helium attracted to clumps of dark matter. The distribution of dark matter on scales smaller than that of massive galaxies is still unknown.
[3] A quasar is the central compact region of a galaxy that emits extremely bright light. The compact region and the surroundings have a large amount of dust that emits radio waves.
[4] MG J0414+0534 is located in the direction of the constellation Taurus as seen from the Earth. This object’s redshift (the increase in the wavelength of light divided by the original wavelength) is z=2.639. The corresponding distance is assumed to be 11 billion light-years, considering the uncertainty in the cosmological parameters.
Additional Information:
The research team was composed by Kaiki Taro Inoue (Faculty of Science and Engineering, Kindai University, Higashi-Osaka, Japan), Takeo Minezaki (Institute of Astronomy, School of Science, University of Tokyo, Mitaka, Tokyo, Japan), Satoki Matsushita (Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan), and Kouichiro Nakanishi (National Astronomical Observatory of Japan, Mitaka, Tokyo, Japan / The Graduate University for Advanced Studies, SOKENDAI, Mitaka, Japan).
The antennas can be moved across the desert plateau over distances from 150 m to 16 km, which will give ALMA a powerful variable “zoom”, similar in its concept to that employed at the centimetre-wavelength Very Large Array (VLA) site in New Mexico, United States.
The high sensitivity is mainly achieved through the large numbers of antenna dishes that will make up the array.
The telescopes were provided by the European, North American and East Asian partners of ALMA. The American and European partners each provided twenty-five 12-meter diameter antennas, that compose the main array. The participating East Asian countries are contributing 16 antennas (four 12-meter diameter and twelve 7-meter diameter antennas) in the form of the Atacama Compact Array, which is part of the enhanced ALMA.
By using smaller antennas than the main ALMA array, larger fields of view can be imaged at a given frequency using ACA. Placing the antennas closer together enables the imaging of sources of larger angular extent. The ACA works together with the main array in order to enhance the latter’s wide-field imaging capability.
ALMA has its conceptual roots in three astronomical projects — the Millimeter Array (MMA) of the United States, the Large Southern Array (LSA) of Europe, and the Large Millimeter Array (LMA) of Japan.
The first step toward the creation of what would become ALMA came in 1997, when the National Radio Astronomy Observatory and the European Southern Observatory agreed to pursue a common project that merged the MMA and LSA. The merged array combined the sensitivity of the LSA with the frequency coverage and superior site of the MMA. ESO and NRAO worked together in technical, science, and management groups to define and organize a joint project between the two observatories with participation by Canada and Spain (the latter became a member of ESO later).
A series of resolutions and agreements led to the choice of “Atacama Large Millimeter Array”, or ALMA, as the name of the new array in March 1999 and the signing of the ALMA Agreement on 25 February 2003, between the North American and European parties. (“Alma” means “soul” in Spanish and “learned” or “knowledgeable” in Arabic.) Following mutual discussions over several years, the ALMA Project received a proposal from the National Astronomical Observatory of Japan whereby Japan would provide the Atacama Compact Array and three additional receiver bands for the large array, to form Enhanced ALMA. Further discussions between ALMA and NAOJ led to the signing of a high-level agreement on 14 September 2004 that makes Japan an official participant in Enhanced ALMA, to be known as the Atacama Large Millimeter/submillimeter Array. A groundbreaking ceremony was held on November 6, 2003 and the ALMA logo was unveiled.
During an early stage of the planning of ALMA, it was decided to employ ALMA antennas designed and constructed by known companies in North America, Europe, and Japan, rather than using one single design. This was mainly for political reasons. Although very different approaches have been chosen by the providers, each of the antenna designs appears to be able to meet ALMA’s stringent requirements. The components designed and manufactured across Europe were transported by specialist aerospace and astrospace logistics company Route To Space Alliance, 26 in total which were delivered to Antwerp for onward shipment to Chile.
9.7.23
Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
Bethany Downer
ESA/Hubble.org
Terzan 12 Compass Image
This is Hubble Space Telescope’s colorful view of globular star cluster Terzan 12. It is a compact beehive-like structure of hundreds of thousands of stars crowded together. Because of scattering by interstellar dust, the stars on the left side of the image appear redder. The stars toward the right side of the image are bluish-white. The image is sprinkled with bright blue foreground stars. There is also a smattering of bright red giant stars across the image.
Credits: NASA, ESA, ESA/Hubble, Roger Cohen (RU)
Summary
Snowball of Stars Shines Through Clouds of Dust and Gas
For astronomers, space can be so cluttered that sometimes you can’t see the forest for the trees. A good example is the globular star cluster Terzan 12. Like all globular star clusters, it is a compact beehive of hundreds of thousands of stars crowded together. Picture it as snow globe. Now, shake the globe and that mimics the chaotic motion of stars inside a cluster. Globular clusters are the oldest inhabitants of our Milky Way. They contain aging stars and some of their burned-out stars are nearly as old as the universe itself. Despite their senility, globular clusters are on the go. They orbit above and below the pancake-flat stellar disk of our galaxy. They can also plunge right through the galactic plane. Identifying them is tricky because they are embedded among the billions of stars in the Milky Way’s disk. And to further complicate things there is a lot of dust in the galactic plane that filters and scatters light from Terzan 12. This makes the cluster appear redder than it normally would in Hubble’s snapshots.
_____________________________________________________
The colorful image of the globular star cluster Terzan 12 is a spectacular example of how dust in space affects starlight coming from background objects.
A globular star cluster is a conglomeration of stars, arranged in a spheroidal shape. Stars in globular clusters are bound together by gravity, with a higher concentration of stars towards the center. The Milky Way has about 150 ancient globular clusters at its outskirts. These clusters orbit around the galactic center, but far above and below the pancake-flat plane of our galaxy, like bees buzzing around a hive.
The location of this globular cluster, deep in the Milky Way in the constellation Sagittarius, means that it is shrouded in gas and dust which absorb and alter the starlight emanating from Terzan 12. The cluster is about 15,000 light-years from Earth. This location leaves a lot of room for intervening interstellar dust particles between us and the cluster to scatter blue light, causing only the redder wavelengths to come through to Earth. The interstellar dust clouds are mottled so that different parts of the cluster look redder than other parts along our line of sight.
The brightest red stars in the photo are bloated, aging giants, many times larger than our Sun. They lie between Earth and the cluster. Only a few may actually be members of the cluster. The very brightest hot, blue stars are also along the line of sight and not inside the cluster, which only contains aging stars.
Terzan 12 is one of 11 globular clusters discovered by the Turkish-Armenian astronomer Agop Terzan approximately a half-century ago. With its sharp vision, Hubble has revolutionized the study of globular clusters ever since its launch in 1990. Hubble observations have shed light on the relation between age and composition in the Milky Way galaxy’s innermost globular clusters.
STScI operates its missions on behalf of NASA, the worldwide astronomy community, and to the benefit of the public. The science operations activities directly serve the astronomy community, primarily in the form of HST, and eventually JWST observations and grants, but also include distributing data from other NASA missions, such as the FUSE: Far Ultraviolet Spectroscopic Explorer – NASA, Galaxy Evolution Explorer – Universe Missions – NASA JPL-Caltech and ground-based sky surveys.
The ground system development activities create and maintain the software systems that are needed to provide these services to the astronomy community. STScI’s public outreach activities provide a wide range of information, on-line media, and programs for formal educators, planetariums and science museums, and the general public. STScI also serves as a source of guidance to NASA on a range of optical and UV space astrophysics issues.
The STScI staff interacts and communicates with the professional astronomy community through a number of channels, including participation at the bi-annual meetings of the American Astronomical Society, publication of quarterly STScI newsletters and the STScI website, hosting user committees and science working groups, and holding several scientific and technical symposia and workshops each year. These activities enable STScI to disseminate information to the telescope user community as well as enabling the STScI staff to maximize the scientific productivity of the facilities they operate by responding to the needs of the community and of NASA.
Full identification of an astronomical asset will be presented once in the first instance of that asset.
Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have detected the magnetic field of a galaxy so far away that its light has taken more than 11 billion years to reach us. We see it as when the Universe was just 2.5 billion years old. The result provides astronomers with vital clues about how the magnetic fields of galaxies like our own Milky Way came to be.
This image shows the orientation of the magnetic field in the distant 9io9 galaxy, seen here when the Universe was only 20% of its current age — the furthest ever detection of a galaxy’s magnetic field. The observations were done with the Atacama Large Millimeter/submillimeter Array (ALMA). Dust grains within 9io9 are somewhat aligned with the galaxy’s magnetic field, and due to this they emit polarised light, meaning that light waves oscillate along a preferred direction rather than randomly. ALMA detected this polarisation signal, from which astronomers could work out the orientation of the magnetic field, shown here as curved lines overlaid on the ALMA image. The polarised light signal emitted by the magnetically aligned dust in 9io9 was extremely faint, representing just one percent of the total brightness of the galaxy, so astronomers used a clever trick of nature to help them obtain this result. The team was helped by the fact that 9io9, although very distant from us, had been magnified via a process known as gravitational lensing. This occurs when light from a distant galaxy, in this case 9io9, appears brighter and distorted as it is bent by the gravity of a very large object in the foreground. Credit: ALMA (ESO/NAOJ/NRAO)/J. Geach et al.
This infrared image shows the distant galaxy 9io9, seen here as a reddish arc curved around a bright nearby galaxy. This nearby galaxy acts as a gravitational lens: its mass curves spacetime around it, bending lightrays coming from 9io9 in the background, hence its distorted shape. This colour view results from combining infrared images taken with ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA) in Chile and the Canada France Hawaii Telescope (CFHT) in the US. Credit: ESO/J. Geach et al.
Zooming-in on 9io9
This video takes us on a journey from our home in the Milky Way to a galaxy far, far away, 9io9. Using ALMA, astronomers have recently detected a galaxy-wide magnetic field in 9io9, making it the furthest-ever detection of a galactic magnetic field. 9io9 is so far away its light has taken more than 11 billion years to reach us: we see it as it was when the Universe was only 2.5 billion years old.
We first see the night sky in visible light and then switch to infrared light when we finally reach 9io9. Here, the galaxy appears as a faint reddish arc curved around a bright nearby galaxy. We then see the ALMA image of 9io9 at millimeter wavelengths, with the orientation of the magnetic field indicated by overlaid curves. Credit: ESO/ALMA (ESO/NAOJ/NRAO)/DESI/CFHT/N. Risinger (skysurvey.org)/J. Geach et al.
Lots of astronomical bodies in the Universe have magnetic fields, whether it be planets, stars or galaxies. “Many people might not be aware that our entire galaxy and other galaxies are laced with magnetic fields, spanning tens of thousands of light-years,” says James Geach, a professor of astrophysics at the University of Hertfordshire, UK, and lead author of the study published today in Nature [below].
“We actually know very little about how these fields form, despite their being quite fundamental to how galaxies evolve,” adds Enrique Lopez Rodriguez, a researcher at Stanford University, USA, who also participated in the study. It is not clear how early in the lifetime of the Universe, and how quickly, magnetic fields in galaxies form because so far astronomers have only mapped magnetic fields in galaxies close to us.
Using ALMA, Geach and his team have discovered a fully formed magnetic field in a distant galaxy, similar in structure to what is observed in nearby galaxies. The field is about 1000 times weaker than the Earth’s magnetic field but extends over more than 16,000 light-years.
“This discovery gives us new clues as to how galactic-scale magnetic fields are formed,” explains Geach. Observing a fully developed magnetic field this early in the history of the Universe indicates that magnetic fields spanning entire galaxies can form rapidly while young galaxies are still growing.
The team believes that intense star formation in the early Universe could have played a role in accelerating the development of the fields. Moreover, these fields can in turn influence how later generations of stars will form. Co-author and ESO astronomer Rob Ivison says that the discovery opens up “a new window onto the inner workings of galaxies, because the magnetic fields are linked to the material that is forming new stars.”
To make this detection, the team searched for light emitted by dust grains in a distant galaxy, “9io9” [1]. Galaxies are packed full of dust grains, and when a magnetic field is present, the grains tend to align, and the light they emit becomes polarised. This means the light waves oscillate along a preferred direction rather than randomly. When ALMA detected and mapped a polarised signal coming from 9io9, the presence of a magnetic field in a very distant galaxy was confirmed for the first time.
“No other telescope could have achieved this,” says Geach. The hope is that with this and future observations of distant magnetic fields the mystery of how these fundamental galactic features form will begin to unravel.
Notes
[1] “9io9” was discovered in the course of a citizen science project. The discovery was helped by viewers of the British BBC television programme Stargazing Live, when over three nights in 2014 the audience was asked to examine millions of images in the hunt for distant galaxies.
Additional Information
The science team is composed of J. E. Geach (Centre for Astrophysics Research, School of Physics, Engineering and Computer Science, University of Hertfordshire, UK [Hertfordshire]), E. Lopez-Rodriguez (Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, USA), M. J. Doherty (Hertfordshire), Jianhang Chen (European Southern Observatory, Garching, Germany [ESO]), R. J. Ivison (ESO), G. J. Bendo (UK ALMA Regional Centre Node, Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, UK), S. Dye (School of Physics and Astronomy, University of Nottingham, UK) and K. E. K. Coppin (Hertfordshire).
Fig. 1: The magnetic field orientation of the gravitationally lensed galaxy 9io9 at z = 2.553.
a–d, ALMA 242 GHz polarimetric observations of the Stokes I, Q and U parameters, and the polarized intensity (PI). The synthetic beam of the observations (1.2″ × 0.9″, θ = 68°) is shown as the red ellipse, lower left. The B field orientation is indicated by white lines shown at the Nyquist sampling, with line lengths proportional to the polarization fraction. e–h, Synthetic polarimetric observations using a constant B field configuration in the source plane. Contours indicate signal to noise: for Stokes I, the contours increase as σI × 2^3,4,5,…. For Stokes Q and U and for PI, the contours start at 3σ and increase in steps of 1σ. Dec., declination; RA, right ascension.
See the science paper for further instructive material with images.
The antennas can be moved across the desert plateau over distances from 150 m to 16 km, which will give ALMA a powerful variable “zoom”, similar in its concept to that employed at the centimetre-wavelength Very Large Array (VLA) site in New Mexico, United States.
The high sensitivity is mainly achieved through the large numbers of antenna dishes that will make up the array.
The telescopes were provided by the European, North American and East Asian partners of ALMA. The American and European partners each provided twenty-five 12-meter diameter antennas, that compose the main array. The participating East Asian countries are contributing 16 antennas (four 12-meter diameter and twelve 7-meter diameter antennas) in the form of the Atacama Compact Array, which is part of the enhanced ALMA.
By using smaller antennas than the main ALMA array, larger fields of view can be imaged at a given frequency using ACA. Placing the antennas closer together enables the imaging of sources of larger angular extent. The ACA works together with the main array in order to enhance the latter’s wide-field imaging capability.
ALMA has its conceptual roots in three astronomical projects — the Millimeter Array (MMA) of the United States, the Large Southern Array (LSA) of Europe, and the Large Millimeter Array (LMA) of Japan.
The first step toward the creation of what would become ALMA came in 1997, when the National Radio Astronomy Observatory and the European Southern Observatory agreed to pursue a common project that merged the MMA and LSA. The merged array combined the sensitivity of the LSA with the frequency coverage and superior site of the MMA. ESO and NRAO worked together in technical, science, and management groups to define and organize a joint project between the two observatories with participation by Canada and Spain (the latter became a member of ESO later).
A series of resolutions and agreements led to the choice of “Atacama Large Millimeter Array”, or ALMA, as the name of the new array in March 1999 and the signing of the ALMA Agreement on 25 February 2003, between the North American and European parties. (“Alma” means “soul” in Spanish and “learned” or “knowledgeable” in Arabic.) Following mutual discussions over several years, the ALMA Project received a proposal from the National Astronomical Observatory of Japan whereby Japan would provide the Atacama Compact Array and three additional receiver bands for the large array, to form Enhanced ALMA. Further discussions between ALMA and NAOJ led to the signing of a high-level agreement on 14 September 2004 that makes Japan an official participant in Enhanced ALMA, to be known as the Atacama Large Millimeter/submillimeter Array. A groundbreaking ceremony was held on November 6, 2003 and the ALMA logo was unveiled.
During an early stage of the planning of ALMA, it was decided to employ ALMA antennas designed and constructed by known companies in North America, Europe, and Japan, rather than using one single design. This was mainly for political reasons. Although very different approaches have been chosen by the providers, each of the antenna designs appears to be able to meet ALMA’s stringent requirements. The components designed and manufactured across Europe were transported by specialist aerospace and astrospace logistics company Route To Space Alliance, 26 in total which were delivered to Antwerp for onward shipment to Chile.
Illustration of “Hoʻoleilana”. Red region (left) shows the enclosed shell with individual galaxies depicted as luminous tiny specks. Photo credit: Frédéric Durillon, Animea Studio; Daniel Pomarède, IRFU, CEA University Paris-Saclay. This work benefited from a government funding by France 2030 (P2I-Graduate School of Physics) under reference ANR-11-IDEX-0003.
A University of Hawaiʻi-led discovery of an immense bubble 820 million light years from Earth is believed to be a fossil-like remnant of the birth of the universe. Astronomer Brent Tully from the UH Institute for Astronomy and his team unexpectedly found the bubble within a web of galaxies. The entity has been given the name “Hoʻoleilana’, a term drawn from the Kumulipo, a Hawaiian creation chant evoking the origin of structure.
The new findings published in The Astrophysical Journal [below], mention these massive structures are predicted by the Big Bang theory, as the result of 3D ripples found in the material of the early universe, known as Baryon Acoustic Oscillations (BAO).
“We were not looking for it. It is so huge that it spills to the edges of the sector of the sky that we were analyzing,” explained Tully. “As an enhancement in the density of galaxies it is a much stronger feature than expected. The very large diameter of one billion light years is beyond theoretical expectations. If its formation and evolution are in accordance with theory, this BAO is closer than anticipated, implying a high value for the expansion rate of the universe.”
Astronomers located the bubble using data from Cosmicflows-4, which is to date, the largest compilation of precise distances to galaxies. Tully co-published the exceptional catalog in fall 2022. His team of researchers believe this may be the first time astronomers identified an individual structure associated with a BAO. The discovery could help bolster scientists’ knowledge of the effects of galaxy evolution.
Enormous bubbles of matter
In the well-established Big Bang theory, during the first 400,000 years, the universe is a cauldron of hot plasma similar to the interior of the Sun. Within a plasma, electrons were separated from the atomic nuclei. During this period, regions with slightly higher density began to collapse under gravity, even as the intense bath of radiation attempted to push matter apart. This struggle between gravity and radiation made the plasma oscillate or ripple and spread outward.
The largest ripples in the early universe depended on the distance a sound wave could travel. Set by the speed of sound in the plasma, this distance was almost 500 million light years, and was fixed once the universe cooled and stopped being a plasma, leaving vast three-dimensional ripples. Throughout the eons, galaxies formed at the density peaks, in enormous bubble-like structures. Patterns in the distribution of galaxies, properly discerned, could reveal the properties of these ancient messengers.
“I am the cartographer of the group, and mapping Hoʻoleilana in three dimensions helps us understand its content and relationship with its surroundings,” said researcher Daniel Pomarede of CEA Paris-Saclay University in France. “It was an amazing process to construct this map and see how the giant shell structure of Hoʻoleilana is composed of elements that were identified in the past as being themselves some of the largest structures of the universe.”
This same team of researchers also identified the Laniākea Supercluster in 2014. That structure, which includes the Milky Way, is small in comparison. Stretching at a diameter of about 500 million light years, Laniākea extends to the near edge of this much larger bubble.
Uncovering a single BAO
Tully’s team discovered that Hoʻoleilana had been noted in a 2016 research paper as the most prominent of several shell-like structures seen in the Sloan Digital Sky Survey. However, the earlier work did not reveal the full extent of the structure, and that team did not conclude they had found a BAO.
Using the Cosmicflows-4 catalog, the researchers were able to see a full spherical shell of galaxies, identify its center, and show that there is a statistical enhancement in the density of galaxies in all directions from that center. Hoʻoleilana encompasses many well-known structures previously found by astronomers, such as the Harvard/Smithsonian Great Wall containing the Coma Cluster, the Hercules Cluster and the Sloan Great Wall. The Boötes Supercluster resides at its center. The historic Boötes Void, a massive empty spherical region, lies inside Hoʻoleilana.
The University of Hawai’i Institute for Astronomy is a research unit within the University of Hawai’i system. The Institute for Astronomy’s main headquarters are located at 2680 Woodlawn Drive in Honolulu, Hawai’i, adjacent to the University of Hawai’i-Mānoa campus.
Additional facilities are located at Pukalani, Maui and Hilo on Hawaiʻi island (the Big Island). Institute for Astronomy employs over 150 astronomers and support staff. Institute for Astronomy astronomers perform research into Solar System objects, stars, galaxies and cosmology.
The Institute for Astronomy was founded in 1967 to conduct research and to manage the observatory complexes at Haleakalā, Maui and the Maunakea Observatory. It has approximately 55 faculty and employs over 300 people.
The two, 10-meter optical/infrared telescopes near the summit of Maunakea on the island of Hawai’i feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrographs and world-leading laser guide star adaptive optics systems.
The University of Hawai‘i includes 10 campuses and dozens of educational, training and research centers across the Hawaiian Islands. As the public system of higher education in Hawai‘i, The University of Hawai‘i offers opportunities as unique and diverse as our Island home.
The 10 University of Hawai‘i campuses and educational centers on six Hawai’ian Islands provide unique opportunities for both learning and recreation.
The University of Hawai‘i is the State’s leading engine for economic growth and diversification, stimulating the local economy with jobs, research and skilled workers.
The University of Hawaiʻi system, formally The University of Hawaiʻi, is a public college and university system that confers associate, bachelor’s, master’s, and doctoral degrees through three university campuses, seven community college campuses, an employment training center, three university centers, four education centers and various other research facilities distributed across six islands throughout the state of Hawai’i in the United States. All schools of The University of Hawaiʻi system are accredited by the Western Association of Schools and Colleges. The University of Hawai‘i system’s main administrative offices are located on the property of the University of Hawaiʻi-Mānoa in Honolulu CDP.
The University of Hawaiʻi-Mānoa is the flagship institution of The University of Hawaiʻi system. It was founded as a land-grant college under the terms of the Morrill Acts of 1862 and 1890. Programs include Hawaiian/Pacific Studies, Astronomy, East Asian Languages and Literature, Asian Studies, Comparative Philosophy, Marine Science, Second Language Studies, along with Botany, Engineering, Ethnomusicology, Geophysics, Law, Business, Linguistics, Mathematics, and Medicine. The second-largest institution is The University of Hawaiʻi at Hilo on the “Big Island” of Hawaiʻi, with over 3,000 students. The University of Hawaiʻi-West Oʻahu in Kapolei primarily serves students who reside in Honolulu’s western and central suburban communities. The University of Hawaiʻi Community College system comprises four community colleges island campuses on O’ahu and one each on Maui, Kauaʻi, and Hawaiʻi. The schools were created to improve accessibility of courses to more Hawaiʻi residents and provide an affordable means of easing the transition from secondary school/high school to college for many students. The University of Hawaiʻi education centers are located in more remote areas of the State and its several islands, supporting rural communities via distance education.
Research facilities
Center for Philippine Studies
Cancer Research Center of Hawaiʻi
East-West Center
Haleakalā Observatory
Hawaiʻi Natural Energy Institute
Institute for Astronomy
Institute of Geophysics and Planetology
Institute of Marine Biology
Lyon Arboretum
Maunakea Observatory
W. M. Keck Observatory
Waikīkī Aquarium
From “Live Science” : “Black holes keep ‘burping up’ stars they destroyed years earlier and astronomers don’t know why”
Years after ripping stars to shreds, 24 black holes suddenly flared up with radio waves in inexplicable ‘burping’ bouts. Half of all star-killing black holes may experience the same.
An illustration shows a tidal disruption event, a black hole ripping apart a star and devouring it. (Image credit: Sophia Dagnello, NRAO/AUI/NSF)
Up to half of the black holes that devour stars “burp up” their stellar remains years later.
Astronomers made the discovery after spending years watching black holes involved in tidal disruption events (TDEs).
TDEs occur when stars venture too close to black holes. These cosmic monsters’ immense gravity exerts incredible tidal forces that stretch and squeeze the stars — a process called spaghettification. The unfortunate stars involved in TDEs are ripped apart or “unraveled” in a matter of hours, signaled by a powerful flash of electromagnetic radiation in visible light.
Some of the stellar material of the destroyed star is flung away from the black hole while the rest forms a thin frisbee-like structure around it called an accretion disk, which gradually feeds that material to the black hole. In its early days, the accretion disk is unstable, and matter sloshes around and smashes into itself, causing outflows detectable by radio waves. But astronomers traditionally only look at these star-eating black holes for a few months following the TDEs.
In the new research, however, astronomers watched black holes involved in TDEs for hundreds of days, finding that in up to 50% of the cases, the black holes “burped back” stellar matter years after the TDE.
“If you look years later, a very, very large fraction of these black holes that don’t have radio emission at these early times will actually suddenly ‘turn on’ in radio waves,” study lead author Yvette Cendes, a research associate at the Harvard and Smithsonian Center for Astrophysics told Live Science. “I call it a ‘burp’ because we’re having some sort of delay where this material is not coming out of the accretion disk until much later than people were anticipating.”
The re-emission of this material for 10 of the 24 black holes happened between two and six years after the star-destroying events. The observations are described in a study uploaded Aug. 25 for The Astrophysical Journal [below], which has not yet been peer-reviewed.
Black holes are definitely messy eaters
Cendes and the team don’t know what’s causing black holes to “switch on” after many years, but whatever it is definitely does not come from inside the black holes.
Black holes are marked by an event horizon – the point at which gravity is so strong that not even light can escape.”Black holes are very extreme gravitational environments even before you pass that event horizon, and that’s what’s really driving this,” Cendes said. “We don’t fully understand if the material observed in radio waves is coming from the accretion disk or if it is being stored somewhere closer to the black hole. Black holes are definitely messy eaters, though.”
Part of the mystery stems from computer models that simulate TDEs, which typically terminate just weeks after the destruction of the star. The new research suggests the models need to be updated to capture some of the black holes’ most unexpected behavior.
For instance, in two cases, the radio waves emitted by black holes peaked, faded and then peaked again.
“There was a second peak, the two black holes re-brightened, and that’s completely new and unexpected,” Cendes said. “People were thinking that you’d have one outflow, and then it’s kind of done. So this observation means these black holes can ‘turn on’ and then ‘turn on’ again.”
Cendes said the team will keep monitoring all of the TDE-causing black holes, especially as some of them are still getting brighter.
8.30.23
Maria Cristina Baglio
New York University Abu Dhabi and Italian National Institute for Astrophysics (INAF)
Abu Dhabi, United Arab Emirates
Tel: +97126287089
Email: mcb19@nyu.edu ; maria.baglio@inaf.it
Francesco Coti Zelati
Institute of Space Sciences
Barcelona, Spain
Tel: (+34) 937379788 430416
Email: cotizelati@ice.csic.es
With a remarkable observational campaign that involved 12 telescopes both on the ground and in space, including three European Southern Observatory (ESO) facilities, astronomers have uncovered the strange behaviour of a pulsar, a super-fast-spinning dead star. This mysterious object is known to switch between two brightness modes almost constantly, something that until now has been an enigma. But astronomers have now found that sudden ejections of matter from the pulsar over very short periods are responsible for the peculiar switches.
We have witnessed extraordinary cosmic events where enormous amounts of matter, similar to cosmic cannonballs, are launched into space within a very brief time span of tens of seconds from a small, dense celestial object rotating at incredibly high speeds,” says Maria Cristina Baglio, researcher at New York University Abu Dhabi, affiliated with the Italian National Institute for Astrophysics (INAF), and the lead author of the paper published today in Astronomy & Astrophysics [below].
A pulsar is a fast-rotating, magnetic, dead star that emits a beam of electromagnetic radiation into space.
As it rotates, this beam sweeps across the cosmos — much like a lighthouse beam scanning its surroundings — and is detected by astronomers as it intersects the line of sight to Earth. This makes the star appear to pulse in brightness as seen from our planet.
PSR J1023+0038, or J1023 for short, is a special type of pulsar with a bizarre behaviour. Located about 4500 light-years away in the Sextans constellation, it closely orbits another star. Over the past decade, the pulsar has been actively pulling matter off this companion, which accumulates in a disc around the pulsar and slowly falls towards it.
Since this process of accumulating matter began, the sweeping beam virtually vanished and the pulsar started incessantly switching between two modes. In the ‘high’ mode, the pulsar gives off bright X-rays, ultraviolet and visible light, while in the ‘low’ mode it’s dimmer at these frequencies and emits more radio waves. The pulsar can stay in each mode for several seconds or minutes, and then switch to the other mode in just a few seconds. This switching has thus far puzzled astronomers.
“Our unprecedented observing campaign to understand this pulsar’s behaviour involved a dozen cutting-edge ground-based and space-borne telescopes,” says Francesco Coti Zelati, a researcher at the Institute of Space Sciences, Barcelona, Spain, and co-lead author of the paper. The campaign included ESO’s Very Large Telescope (VLT)[below] and ESO’s New Technology Telescope (NTT)[below], which detected visible and near-infrared light, as well as the Atacama Large Millimeter/submillimeter Array (ALMA)[below], in which ESO is a partner. Over two nights in June 2021, they observed the system make over 280 switches between its high and low modes.
“We have discovered that the mode switching stems from an intricate interplay between the pulsar wind, a flow of high-energy particles blowing away from the pulsar, and matter flowing towards the pulsar,” says Coti Zelati, who is also affiliated with INAF.
In the low mode, matter flowing towards the pulsar is expelled in a narrow jet perpendicular to the disc. Gradually, this matter accumulates closer and closer to the pulsar and, as this happens, it is hit by the wind blowing from the pulsating star, causing the matter to heat up.
Artist’s animation of the pulsar PSR J1023+0038
This artist’s animation shows the pulsar PSR J1023+0038 stealing gas from its companion star. This gas accumulates in a disc around the pulsar, slowly falls towards it, and is eventually expelled in a narrow jet. In addition, there is a wind of particles blowing away from the pulsar, represented here by a cloud of very small dots. This wind clashes with the infalling gas, heating it up and making the system glow brightly in X-rays and ultraviolet and visible light. Eventually, blobs of this hot gas are expelled along the jet, and the pulsar returns to the initial, fainter state, repeating the cycle. This pulsar has been observed to switch incessantly between these two states every few seconds or minutes. Credit: M. Kornmesser/ESO.
The system is now in a high mode, glowing brightly in the X-ray, ultraviolet and visible light. Eventually, blobs of this hot matter are removed by the pulsar via the jet. With less hot matter in the disc, the system glows less brightly, switching back into the low mode.
While this discovery has unlocked the mystery of J1023’s strange behaviour, astronomers still have much to learn from studying this unique system and ESO’s telescopes will continue to help astronomers observe this peculiar pulsar. In particular, ESO’s Extremely Large Telescope (ELT)[below], currently under construction in Chile, will offer an unprecedented view of J1023’s switching mechanisms. “The ELT will allow us to gain key insights into how the abundance, distribution, dynamics, and energetics of the inflowing matter around the pulsar are affected by the mode switching behavior,” concludes Sergio Campana, Research Director at the INAF Brera Observatory and coauthor of the study.
More information
Other telescope used in this work include ESA’sXMM-Newton, NASA/ESA Hubble, China’s FAST radio telescope, NASA/TU Denmark/ISA NuSTAR, NRAO VLA, NASA NICER, NASA Swift,and ESO/INAF Rapid Eye Mount telescope.
This research was presented in a paper to appear in Astronomy & Astrophysics [below]
The team is composed of M. C. Baglio (Center for Astro, Particle, and Planetary Physics, New York University Abu Dhabi, UAE [NYU Abu Dhabi]; INAF – Osservatorio Astronomico di Brera, Merate, Italy [INAF Brera]), F. Coti Zelati (Institute of Space Sciences, Campus UAB, Barcelona, Spain [ICE–CSIC]; Institut d’Estudis Espacials de Catalunya (IEEC), Barcelona, Spain [IEEC]; INAF Brera), S. Campana (INAF Brera), G. Busquet (Departament de Física Quànticai Astrofísica, Universitat de Barcelona, Spain; Institut de Ciències del Cosmos, Universitat de Barcelona, Spain; IEEC), P. D’Avanzo (INAF Brera), S. Giarratana (INAF – Istituto di Radioastronomia, Bologna, Italy [INAF Bologna]; Department of Physics and Astronomy, University of Bologna, Italy [Bologna]), M. Giroletti (INAF Bologna; Bologna), F. Ambrosino (INAF – Osservatorio Astronomico di Roma, Rome, Italy [INAF Roma]); INAF – Istituto Astrofisica Planetologia Spaziali, Rome, Italy; Sapienza Università di Roma, Rome, Italy), S.Crespi (NYU Abu Dhabi), A. Miraval Zanon (Agenzia Spaziale Italiana, Rome, Italy; INAF Roma), X. Hou (Yunnan Observatories, Chinese Academy of Sciences, Kunming, China; Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming, China), D. Li (National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China; Research Center for Intelligent Computing Platforms, Zhejiang Laboratory, Hangzhou, China), J. Li (CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, China; School of Astronomy and Space Science, University of Science and Technology of China, Hefei, China), P. Wang (Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing, China), D. M. Russell (NYU Abu Dhabi), D. F. Torres (INAF Brera; IEEC; Institució Catalana de Recercai Estudis Avançats, Barcelona, Spain), K. Alabarta (NYU Abu Dhabi), P. Casella (INAF Roma), S. Covino (INAF Brera), D. M. Bramich (NYU Abu Dhabi; Division of Engineering, New York University Abu Dhabi, UAE), D. de Martino (INAF − Osservatorio Astronomico di Capodimonte, Napoli, Italy), M. Méndez (Kapteyn Astronomical Institute, University of Groningen, Groningen, The Netherlands), S. E. Motta (INAF Brera), A. Papitto (INAF Roma), P. Saikia (NYU Abu Dhabi), and F. Vincentelli (Instituto de Astrofísica de Canarias, Tenerife, Spain; Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain).
The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte] (EU)(CL) is the foremost intergovernmental astronomy organization in Europe and the world’s most productive ground-based astronomical observatory by far. today ESO is supported by 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 program 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 organizing cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: Cerro La Silla,Cerro Paranaland Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration in astronomy. Established as an intergovernmental organization in 1962, ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvelous place with unique conditions to observe the sky, hosts our telescopes. At Paranal ESO will host and operate the Čerenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Cerro La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun). 3.6m telescope & HARPS at Cerro LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.
8.25.23
Jonas Enander
Jonas Enander was a science communication intern at ESO. He has a PhD in physics from Stockholm University. After doing postdoctoral research in cosmology and astrophysics at the Karlsruhe Institute of Technology in Germany, he switched career to science writing and outreach.
__________________________________________
What you’ll discover in this blog post:
-Why there are few Neptune-sized exoplanets orbiting very close to other stars.
-Why not all exoplanets orbit their stars in an orderly fashion.
-How astronomers can work out the 3D shapes of the orbits of exoplanets.
__________________________________________
Astronomers have found thousands of planets that orbit around stars other than the Sun. While observing these exoplanets, they noticed an odd pattern: planets orbiting very close to their host star are either small rocky worlds like Earth or giant gas planets like Jupiter; mysteriously, few of them have intermediate sizes similar to Neptune’s. In this blog post we follow a team of astronomers who tried to solve this exoplanetary mystery.
Since the first detection of an exoplanet in 1992, astronomers have catalogued over 5000 more. They found that exoplanetary systems can be very different from our own Solar System.
“Who might have thought that, for instance, planets twice the size of Jupiter could live so close to their stars that they lose thousands of tons of their atmosphere every second?” reflects Omar Attia, a PhD student at the University of Geneva, Switzerland and co-author of study on exoplanets orbiting close to their star published in Astronomy & Astrophysics [below] earlier this year. The wide variety of exoplanetary systems intrigued him: “I realized that observing exoplanets brings a direct insight into the strange nature of the Universe.“
One of the strange features of exoplanetary systems has to do with the size of exoplanets that orbit very close to their host star. In this region, astronomers have found many small rocky planets like Earth and gas giants like Jupiter, but only a few intermediate sized planets like Neptune. Astronomers dubbed the lack of such Neptune-sized exoplanets the “Neptune desert”. This does not refer to an actual desert on Neptune, but to a lack of planets of this size close to their host star.
The cause of the Neptune desert is a mystery. It seems that some kind of mechanism prevents Neptune-sized planets from orbiting very close to their host stars. If astronomers could solve this problem, they would have a deeper understanding of how planetary systems form and evolve. This would, in turn, teach us what type of planetary systems can exist around the hundred of billions of stars in the Milky Way, and crucially how unique (or not) our own Solar System is among them.
Vincent Bourrier, assistant professor at the University of Geneva and first author of the study, set out to solve this mystery. He is a member of the PlanetS National Centre of Competence in Research in Switzerland, and has a history with exoplanets. “I participated in the first detection of a Neptune-sized planet losing its atmosphere a few years ago,” he explains. “My simulations showed that this planet, located at the border of the Neptune desert, was eroding much faster than expected.” This could explain why there are so few of these planets very close to their stars: as they lose their atmosphere they can end up becoming smaller bodies.
When Bourrier studied the orbit of this Neptune-sized planet around its host star he found that it moved in a highly unusual way. All planets in our Solar System orbit in nearly the same plane around the Sun, and in the same direction. Moreover, the Sun itself also spins around its own axis, and the orbital motion of the planets is aligned with this rotation: none of the planets moves backwards nor in a highly inclined orbit relative to the Sun’s equator. This is due to the fact that both the Sun and the planets formed out of the collapse of a rotating nebular cloud. This common orbital plane is in fact a ubiquitous feature in most planetary systems.
Most planets orbit their star in the same plane and direction as the rotation of the star itself. But sometimes planets can have very inclined orbits, or even move backwards relative to the star’s rotation, as shown in this artist’s impression. Credit: L. Calçada/ESO.
But something had disrupted the Neptune-sized planet that Bourrier studied, making it leave the orbital plane where it was formed. Could this misaligned orbit be linked to the general lack of Neptune-sized planets close to their stars?
One single planet is not enough to establish a trend, though. Therefore, Bourrier, Attia and their colleagues set out to study the orbital structure of other exoplanets living in the vicinity of the Neptune desert, to see if their orbits were also highly misaligned.
Finding misaligned orbits
The two most common techniques to detect exoplanets are the transit method and the radial velocity method.
The transit method measures the dimming of a star when an orbiting planet passes in front of it. The radial velocity method on the other hand uses spectroscopy to measure periodic changes in the velocity of a star caused by the gravitational tug of a planet orbiting around it.
These two techniques can tell us many properties of an exoplanet such its size, mass, distance to its host star and orbital period, but not how inclined the orbit is relative to the star’s equator. This requires a more sophisticated trick called the Rossiter-McLaughlin method which, in a way, combines the other two methods. As an exoplanet moves in front of the star, it will sequentially block either the part of the star rotating towards or away from us, changing the spectrum of the star in subtle ways that allow astronomers to work out the 3D shape of the orbit, as illustrated in the animation below.
This animation illustrates how astronomers can measure the inclination of a planet’s orbit with respect to the rotation of the star. When a star rotates, light from the side approaching us appears shifted to bluer colours due to the Doppler effect, whereas light from the receding side is red-shifted. When a planet transits in front of the star it will block different parts of it, changing the shape of the spectral lines. If the planet transits in the same direction as the star’s rotation, the planet will first block the blue-shifted side of the star and then the red-shifted one, and vice versa if the planet orbits backwards. If the planet’s orbit is very inclined, the deformation of the spectral lines happen mostly at the centre of the lines rather than from side to side. Credit: M. Kornmesse/ESO.
One of the telescopes that Bourrier’s team used was the ESO 3.6-metre telescope [below] at La Silla Observatory in Chile. This telescope hosts the High Accuracy Radial velocity Planet Searcher (HARPS), a sophisticated spectrograph and one of the premier instruments in the world for studying exoplanets. It can detect minute changes in stellar spectral lines, exactly what the team needed.
With the aid of HARPS and other instruments worldwide, Bourrier and his team measured the orbital alignment of 12 exoplanets near the Neptune desert. They found that 9 of them (a staggering 75%) had orbits that were highly tilted relative to the equatorial plane defined by the rotation of the star. This is a larger incidence of misaligned orbits than for other planets outside of the Neptune desert.
Wandering planets
Planets don’t always orbit their star at the same distance where they were born. “A star and the planets orbiting around it are formed from the same material, which is a mix of gas and dust”, explains Attia. “In the system’s infancy, the remaining material that was not used to form planets settles in a disc around the star, which perturbs the young planets’ orbits and makes them migrate until they reach their final position.” Gravitational interactions between the star and the planet can also alter the orbit, as can close encounters with other bodies in the stellar system. This may even have happened in our own Solar System.
Neptunes that migrated close to their star early on lost their atmosphere quickly, leaving smaller bodies behind. “Neptunes at the border of the desert likely survived thanks to a delayed migration and erosion,” explains Bourrier, and the fact that their orbits are so misaligned tells us this migration happened via some disruptive process and not in a smooth way.
Although these new results are important, there is nevertheless more work to be done to fully solve the mystery of the Neptune desert. In particular, the HARPS measurements are not sensitive enough to determine if low-mass planets close to the desert undergo a similarly disruptive migration. To find out, the team has been awarded observing time with another one of ESO’s flagship planetary hunting instruments: the Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO).
ESPRESSO is attached to ESO’s Very Large Telescope at Paranal Observatory in Chile, and it can measure radial velocity changes as small as 10 cm/s, similar to the tug the Earth exerts on the Sun. “ESPRESSO will allow us to study the orbital architectures of smaller planets on the low-mass end of the desert, and to determine whether they share similarly misaligned architectures,” says Bourrier.
Moreover, since the VLT’s 8 m mirrors collect 5 times more light than the 3.6 m telescope, ESPRESSO will allow them to observe fainter stars than with HARPS and therefore study many more of them. The team plans to observe 58 transiting Neptunes in 36 nights over the coming 2 years, and this larger sample of planetary systems will yield more robust conclusions about the mechanisms responsible for the Neptune desert.
European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte] (EU) is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. 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: Cerro La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
Part of the world-wide effort to scan and identify near-Earth objects, the European Space Agency’s Test-Bed Telescope 2 (TBT2), a technology demonstrator hosted at ESO’s La Silla Observatory in Chile, has now started operating. Working alongside its northern-hemisphere partner telescope, TBT2 will keep a close eye on the sky for asteroids that could pose a risk to Earth, testing hardware and software for a future telescope network.
A visualization of a magnetar, one of the possible sources of fast radio bursts. [Credit: NASA’s Goddard Space Flight Center]
They’re powerful, they’re fast, and we aren’t sure about what causes them, but astronomers are closer than ever to understanding the source of mysterious fast radio bursts.
Flashes Without a known Cause
Fast radio bursts: one of the most recent mysteries to appear in the sky and one of the most active fields of astronomical research. Since the discovery of the first of these powerful <1-second eruptions eruptions of radio waves back in 2007, astronomers have recorded hundreds of similar events. We know that they must originate from beyond our Milky Way galaxy, but, beyond that, astronomers have still yet to settle on a consensus about what might cause such brief, energetic flashes. This mystery of the origins of these bursts has driven many astronomers into an exciting, frustrating, and increasingly productive quest to understand whatever immense forces power them.
It is not easy to study a flash; by their very nature, they appear for only a fraction of a second, then vanish to almost never return. While a precious few do eventually repeat, they do so at largely irregular intervals, meaning astronomers can never really be sure when or where a fast radio burst might happen. The ones astronomers do manage to spot are almost always flagged by survey telescopes that scan huge swaths of the sky at once. A wide field of view comes with a tradeoff, though: although these telescopes can monitor enough sky that they have a good chance of catching a burst, their view of the sky is fairly blurry. So, although astronomers have recorded a few hundred bursts by now, they usually can’t say exactly where each one came from.
For the 16 years since the discovery of the first fast radio burst, astronomers have been trying to piece together their secrets without even knowing the location of each flash. Recently, however, they have made progress both in narrowing in on their quarry and on understanding their source. Below are three recent studies published in AAS Journals detailing this progress.
Zooming In
First up is a study published in May of this year by a team led by Shivani Bhandari, Netherlands Institute for Radio Astronomy. Bhandari and collaborators describe their discovery of a fast radio burst using the Australian Square Kilometre Array Pathfinder, a relatively new and phenomenally capable radio telescope that they used the pin down the location of the flash to within one arcsecond (about 0.03% of a degree!).
This extreme precision allowed the team to identify which galaxy the flash came from, and what they found was somewhat surprising: the host was a small, somewhat boring dwarf galaxy with almost no ongoing star formation. This is in contrast to the handful of known hosts of repeating fast radio burst, which were all more lively, active galaxies. Considering both the host and the properties of the burst itself, the team concluded that their burst could have been caused by an “accretion jet from a hyperaccreting black hole.”
Magnetar Earthquakes?
A month later in early June, a team led by Fayin Wang, Nanjing University, published their own analysis of archival data to suggest an alternative source. By digging through all of the observations of two known repeating fast radio burst collected by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), Wang and colleagues realized that the gaps between bursts were not quite as random as previously thought.
Instead, whatever was causing the bursts seemed to have “memory,” meaning the triggers must be correlated in time. Building from this, they advocate for a different explanation, positing that the bursts occur whenever a highly magnetized neutron star undergoes “crustal fractures” — in other words, earthquakes. After a shift, the magnetic stresses will build up again and cause the process to repeat, which could give rise to the recurring bursts.
More Than One
The location of one of the thirteen repeating fast radio burst, which lines up perfectly with a pair of merging spiral galaxies. [Michilli et al. 2023]
Finally, in late June, another study led by Daniele Michilli, Massachusetts Institute of Technology, offered a bridge between the two previous ones. This publication describes a re-analysis of data collected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME), which resulted in newer, much more precise estimates of previous fast radio burst locations.
The team focused on 13 repeating bursts and pinned down each of their locations to within about 10 arcseconds. While that isn’t precise enough to nail the host galaxy for all 13, they did mange to conclusively identify the host for two of them. Intriguingly, these two galaxies were nothing alike: one is a peaceful, quiescent galaxy, and the other is one in a pair of merging spiral galaxies that are actively forming many stars. This suggests that fast radio burst can come from a range of environments, or even that there could be multiple causes that each produce a similar looking signal.
While the final, well-supported model to describe all fast radio burst is still out of reach, astronomers are actively getting closer to this final goal. As new telescopes and processing techniques come online, it is only a matter of time until enough data is collected and analyzed that a clearer picture emerges. Soon, what now appear as mysterious flashes will be the subjects of well-documented chapters in the next textbooks, and this knowledge will be based on studies happening today, like these three.
The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.
The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.
Adopted June 7, 2009
The society was founded in 1899 through the efforts of George Ellery Hale. The constitution of the group was written by Hale, George Comstock, Edward Morley, Simon Newcomb and Edward Charles Pickering. These men, plus four others, were the first Executive Council of the society; Newcomb was the first president. The initial membership was 114. The AAS name of the society was not finally decided until 1915, previously it was the “Astronomical and Astrophysical Society of America”. One proposed name that preceded this interim name was “American Astrophysical Society”.
The AAS today has over 7,000 members and six divisions – the Division for Planetary Sciences (1968); the Division on Dynamical Astronomy (1969); the High Energy Astrophysics Division (1969); the Solar Physics Division (1969); the Historical Astronomy Division (1980); and the Laboratory Astrophysics Division (2012). The membership includes physicists, mathematicians, geologists, engineers and others whose research interests lie within the broad spectrum of subjects now comprising contemporary astronomy.
In 2019 three AAS members were selected into the tenth anniversary class of TED Fellows.
The AAS established the AAS Fellows program in 2019 to “confer recognition upon AAS members for achievement and extraordinary service to the field of astronomy and the American Astronomical Society.” The inaugural class was designated by the AAS Board of Trustees and includes an initial group of 232 Legacy Fellows.
Ms Gurjeet Kahlon
Royal Astronomical Society
Mob: +44 (0)7802 877 700
press@ras.ac.uk
Dr Robert Massey
Royal Astronomical Society
Mob: +44 (0)7802 877 699
press@ras.ac.uk
Science contacts
Agostina Filócomo
Universidad Nacional de Río Negro and Facultad de Ciencias Atronómicas y Geofísicas (Universidad Nacional de La Plata)
afilocomo@unrn.edu.ar
Juan Facundo Albacete Colombo
Universidad Nacional de Río Negro
jfalbacetecolombo@unrn.edu.ar
Artist’s impression of a T Tauri star: system formed by a central star and a circumstellar disk. This is what our Solar System looked like 4.5 billion years ago. The gamma-ray emission would be produced in the star’s most violent and energetic flares. Credit: INAF-OAPa/S. Orlando Licence type Attribution (CC BY 4.0)
A team of scientists from Argentina and Spain have reported the first observational evidence that a type of young low-mass star, known as T Tauri stars, are capable of emitting gamma radiation. The study is published in MNRAS [below].
Note: While this article is important, the writers fail to acknowledge the forthcoming Earth based Čerenkov gamma-ray Astronomy (now H.E.S.S., Veritas. Magic, even the the forthcoming Čerenkov Telescope Array referenced in the science paper.
The Fermi satellite has been continuously observing the sky since its launch in 2008, and from these observations it is known that about 30% of gamma-ray sources detected throughout the entire night sky remain unidentified – the origins of these gamma-ray detections are unknown.
Some of these mysterious sources were studied by PhD student Agostina Filócomo and a team of researchers in order to determine their origin. Several of the gamma-ray sources appear to originate from star forming regions, but the team had no explanation as to why – so they decided to investigate. The study focuses on star-forming region NGC 2071, which lies in the northern part of the molecular cloud Orion B.
To try and pinpoint the cause of these mysterious gamma-ray bursts, the team decided to look to objects known as “T Tauri stars”, which are low-mass stars in formation. T Tauri stars consist of a central star and a disk of gas and dust orbiting around it, where planets could form. T Tauri stars are known for their fluctuating brightness, and are typically found near regions of active star formation.
The team noted that three unidentified gamma sources observed at different time intervals were coming from the part of the sky that the young star-forming region NGC 2071 is located. At least 58 stars classified as T Tauri stars are known to be forming here. There are no other objects in this region that can be a source of gamma-ray emission.
A possible explanation is that sporadic gamma-ray radiation is produced by T Tauri stars during powerful flare episodes known as “megaflares”, in which electromagnetic bursts are produced by magnetic energy stored in the atmospheres of the stars. Megaflares can span several stellar radii and last a few hours. Although there is flare activity on the Sun at present, it is not on the same scale as a megaflare. Megaflares are far more powerful, and if they were to take place on the Sun, would be detrimental to life on planet Earth.
This might explain the origin of multiple previously unknown gamma-ray sources. Understanding the physical processes in T Tauri stars also provides information on the early conditions that led to the genesis of the Sun and our Solar System.
Ph.D. student Agostina Filócomo claims “This observational evidence is essential for understanding the origin of sources that have previously remained unknown for more than a decade, which is unquestionably a step forward in astronomy. It is also critical to comprehend the processes that occur during the early phases of star formation: if a T Tauri star produces gamma-ray radiation, it will affect the gas conditions of the protoplanetary disk and, consequently, the evolution of planet formation. The discovery of this phenomenon serves to understand how not only the Sun but also our home planet, Earth, were formed and evolved.”
Figure 1.
NGC 2071 (the nebula close to the centre of the image) obtained with the Wide-field Infrared Survey Explorer (WISE) using the 22 μm (red), 4.6 μm (green), and 3.4 μm (blue) bands. In white, we show the 3σ significance Fermi error ellipses that positionally coincide with NGC 2071. 1FGL, 2FGL, and 3FGL are the first, second, and third Fermi catalogue, respectively.
See the science paper for further instructive material with images.
The Royal Astronomical Society is a learned society and charity that encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. Its headquarters are in Burlington House, on Piccadilly in London. The society has over 4,000 members (“Fellows”), most of them professional researchers or postgraduate students. Around a quarter of Fellows live outside the UK.
The society holds monthly scientific meetings in London, and the annual National Astronomy Meeting at varying locations in the British Isles. The Royal Astronomical Society publishes the scientific journals MNRAS and Geophysical Journal International, along with the trade magazine Astronomy & Geophysics.
The Royal Astronomical Society maintains an astronomy research library, engages in public outreach and advises the UK government on astronomy education. The society recognizes achievement in Astronomy and Geophysics by issuing annual awards and prizes, with its highest award being the Gold Medal of The Royal Astronomical Society. The Royal Astronomical Society is the UK adhering organization to the International Astronomical Union and a member of the UK Science Council.
The society was founded in 1820 as the Astronomical Society of London to support astronomical research. At that time, most members were ‘gentleman astronomers’ rather than professionals. It became the Royal Astronomical Society in 1831 on receiving a Royal Charter from William IV. A Supplemental Charter in 1915 opened up the fellowship to women.
One of the major activities of the RAS is publishing refereed journals. It publishes two primary research journals, the Monthly Notices of the Royal Astronomical Society [MNRAS] in astronomy and (in association with The German Geophysical Society [Deutsche Geophysikalische Gesellschaft e.V. ](DE)]) the Geophysical Journal International in geophysics. It also publishes the magazine A&G which includes reviews and other articles of wide scientific interest in a ‘glossy’ format. The full list of journals published (both currently and historically) by the RAS, with abbreviations as used for the NASA ADS bibliographic codes is:
Memoirs of the Royal Astronomical Society (MmRAS): 1822–1977[3]
Monthly Notices of the Royal Astronomical Society (MNRAS): Since 1827
Geophysical Supplement to Monthly Notices (MNRAS): 1922–1957
Geophysical Journal (GeoJ): 1958–1988
Geophysical Journal International (GeoJI): Since 1989 (volume numbering continues from GeoJ)
Quarterly Journal of the Royal Astronomical Society (QJRAS): 1960–1996
Astronomy & Geophysics (A&G): Since 1997 (volume numbering continues from QJRAS)
Associated groups
The RAS sponsors topical groups, many of them in interdisciplinary areas where the group is jointly sponsored by another learned society or professional body:
sciencesprings