Connecting A Star’s Chemical Composition and Planet Formation (Planetary Science)

Researchers from Penn’s Department of Physics and Astronomy have developed a new method for better understanding the relationship between a star’s chemical composition and planet formation. The study was led by recent graduate Jacob Nibauer for his senior thesis with Bhuvnesh Jain and was co-supervised by former Penn postdoc Eric Baxter. The researchers found that the majority of stars in their dataset are similar in composition to the sun, somewhat at odds with earlier work and implying that many stars in the Milky Way could host their own Earth-like planets. These results were presented at the 238th American Astronomical Society conference and also published in the Astrophysical Journal.

The most common technique for finding exoplanets, ones that exist outside of the solar system, involves the transit method, when an exoplanet moves between its star and the observer and causes a dip in the star’s brightness. While most of the known exoplanets have been discovered using this method, this approach is limited because exoplanets can only be detected when their orbit and the observer are perfectly aligned and have short enough orbiting periods. The second most powerful technique, the radial velocity or Doppler method, has other limitations in its ability to find planets.

This raises the question, If planets can’t be detected around a star, can their existence be inferred by studying the host star? The researchers found that the answer to this question is a qualified yes, with new methods helping astronomers better understand how the formation of exoplanets is related to the composition of the star they orbit.

“The idea is that planets and stars are born out of the same natal cloud, so you can imagine a scenario where a rocky planet locks on to enough material to leave the late stellar surface depleted in those elements,” says Nibauer. “The goal is to answer whether planet-hosting stars look different than stars with no planets, and one way to do that is to search for signatures of planet formation in the composition of the stellar surface. Fortunately, the composition of a star, at least of its outer layers, can be inferred from its spectrum, the distribution of light intensity over different frequencies.”

To do this, the researchers used data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2), focusing on 1,500 Milky Way galaxy stars with chemical composition data for five different elements. Nibauer’s novel contribution was to apply Bayesian statistics to measure the abundance of five rock-forming, or “refractory,” elements and objectively separate populations of stars based on their chemical compositions.

Connecting a star’s chemical composition and planet formation
A projection of data from APOGEE, with orange points indicating stars used in this analysis (top) and the abundance ratios of a subset of chemical elements relative to iron in the population of Sun-like stars (bottom). Credit: Jacob Nibauer

Nibauer’s method allows researchers to look at stars with low signal-to-noise ratios, or where measurement background can be larger than the star’s own signal. “This framework, rather than focusing on a star-by-star basis, combines measurements across the entire population allowing us to characterize the global distribution of chemical abundances,” says Nibauer. “Because of that, we’re able to include much larger populations of stars compared with previous studies.”

The researchers found that their dataset neatly separated stars into two populations. Depleted stars, which make up the majority of the sample, are missing refractory elements compared to the not-depleted population. This could indicate that the missing refractory material in the depleted population is locked up in rocky planets. These results are consistent with other smaller, targeted studies of stars that use more precise chemical-composition measurements. However, the interpretation of these results differs from previous studies in that the sun appears to belong to a population which makes up the majority of the sample.

“Previous studies were sun-centric, so stars are either like the sun or not, but Jake developed a methodology to group similar stars without referencing the sun,” says Jain. “This is the first time that a method which ‘let the data speak’ had found two populations, and we could then place the sun in one of those groups, which turned out to be the depleted group.”

This study also provides a promising avenue to identify individual stars which may have a higher likelihood of hosting their own planets, says Nibauer. “The long-term goal is to identify large populations of exoplanets, and any technique that can place a probabilistic constraint on whether a star is likely to be a planet host without having to rely on the usual transit method is very valuable,” he says.

And if Milky Way stars being depleted is the norm, this could mean that the majority of these stars could be orbited by Earthlike planets, opening up the possibility that stars that are “missing” heavier elements simply have them locked up in orbiting rocky exoplanets, though other possible connections to exoplanets are also being explored. “This would be exciting if confirmed by future analyses of larger datasets,” says Jain.

Featured image: An artist’s concept of a young star circled by planets and rings of dust that arise when newly-formed, rocky planets collide with one another. A new study presented at the 238th American Astronomical Society conference describes a new method for quantifying the relationship between a star’s chemical composition and planet formation, work that could help researchers identify individual stars that have a higher likelihood of hosting planets. Credit: NASA/JPL-Caltech


Reference: Jacob Nibauer et al, Statistics of the Chemical Composition of Solar Analog Stars and Links to Planet Formation, The Astrophysical Journal (2021). DOI: 10.3847/1538-4357/abd0f1


Provided by University of Pennsylvania

Classical Nova Explosions Involve Jets Of Oppositely Directed Hot Gas, Plasma (Astronomy)

Scientists at the University of Oxford have discovered that classical nova explosions are accompanied by the ejection of jets of oppositely-directed hot gas and plasma, and that this persists for years following the nova eruption.  Previously, such jets had only been encountered emanating from very different systems such as black holes or newly collapsing stars.

A classical nova is the name given to an explosive event in our Galaxy.  It has been known for decades that when a nova erupts, its brightness can increase by several orders of magnitude and can transform an undetectable star into an object that can be seen by the naked eye.   This huge increase in brightness happens when matter is ripped away from one star onto the hard surface of a companion star, a compact object known as a white dwarf.   The matter accreted onto the white dwarf becomes extremely hot and dense, providing the right conditions to synthesize heavier elements, a process known as thermonuclear runaway. 

It’s amazing that jets emerge from these remarkable objects, in spite of the turbulence of a nova detonation 

The Global Jet Watch, led at the University of Oxford by Professor Katherine Blundell, comprising telescopes separated in longitude around the world to follow sub-day variability in the Galaxy made this discovery possible. The team published this finding in early 2021, reporting the initial discovery of jets in a classical nova that had erupted during the pandemic lockdown of 2020 and was subsequently followed intensively with time-lapse spectroscopy with the Global Jet Watch in the days, weeks and months that followed. 

Illustration of how the speeds along our line-of-sight to the nova that detonated in July 2020 changed in the days that followed its eruption
Graphic shows: Illustration of how the speeds along our line-of-sight to the nova that detonated in July 2020 changed in the days that followed its eruption. The changing speeds along our line-of-sight are believed to be because the directions along which the jets of hydrogen are squirted change with time, a phenomenon known as precession. © Credit: Oxford Science Blog

In a second paper published by the Royal Astronomical Society, the team has demonstrated that the exact same behaviour is exhibited by four out of four classical novae that the Global Jet Watch has been monitoring. This collection of four eruptions includes different types of classical novae (including one hybrid type) suggesting that jets are a likely outcome for the classical nova phenomenon in general.

Besides now being able to study the phenomena of jets, their launch, their propagation and their precession in a new way, the discovery is also a significant advance in understanding the influence of classical novae themselves on our Galaxy, the Milky Way. The fact that they can propagate hot gas far, far away from the site of the explosion itself has implications for the enrichment of the inter-stellar medium within our Galaxy with the new elements synthesised in the course of the explosion.  Further exploration and investigation of these implications is planned.

Dominic McLoughlin, the graduate student who had been investigating the time-series nova data, said; ‘The nova that erupted in July 2020 enabled us to crack the code. Discovering jets in the immediate aftermath of classical nova eruptions means we can now study them as they start launching and precessing – it’s not understood how jets actually get launched in general, despite the fact they happen all over space.’ 

Professor Katherine Blundell, who designed and instigated the Global Jet Watch, said: ‘It’s amazing that jets emerge from these remarkable objects, in spite of the turbulence of a nova detonation – and it’s also amazing that the Global Jet Watch has persisted robustly throughout the turbulent times of lockdown. This opens up a whole new way to study the jet phenomena which is ubiquitous across the Universe.’

“The nova that erupted in July 2020 enabled us to crack the code”

The Global Jet Watch was designed to accomplish two important goals. One of these goals was to be able to provide time-lapse spectroscopy of evolving and dynamic systems in our Galaxy, an important class of which are the so-called micro-quasars which can be regarded as scaled-down, speeded-up models of quasars in the distant Universe. These new results demonstrate its effectiveness in following different types of optical transients as well as its resilience at a time when in-person visits to the observatories are not possible.

Professor Katherine Blundell said: ‘This discovery did not come about because of detailed plans and presumptions about the way the Universe is, but instead as a fun, auxiliary project adjunct to the main research programmes of the Global Jet Watch. Being open to exploring the Universe in new ways invariably seems to produce new insights into its richness and inner workings.’

The second goal of the Global Jet Watch was to engage young people in developing countries, especially girls, into science and technology through the doorway of astronomy which is a gateway and exemplar of so many areas of high-level science and engineering. In non-lockdown times, the schools around the world that host the observatories are free to use the telescopes before local bedtime.

“The Global Jet Watch uniquely combines excellence in science with empowerment for school students, around the world; astronomy is a gateway to science for so many”

The experience of controlling the telescopes, operating the cameras and exploring and capturing the night sky has proved to be a pivotal experience for many. Already some of the first students to have used the telescope at their school have gone on to study science and/or engineering at colleges and universities in their countries.  

Brian Schmidt, the Vice-Chancellor of the Australian National University and Nobel Prize winner in 2011, said: ‘This discovery will change the way we think about classical novae. The Global Jet Watch uniquely combines excellence in science with empowerment for school students, around the world; astronomy is a gateway to science for so many.’

A group of students control the telescope
A group of students control the telescope © Credit: Oxford Science Blog

Steven Lee, the Instrument Scientist on the Global Jet Watch, who designed and built its spectrographs which were essential to making the high-fidelity detections of the phenomenon, said: ‘Although we didn’t expect this discovery, tracking these jets is in fact exactly what the Global Jet Watch was designed to do. The design of our instruments was entirely driven by the main science goals of the Global Jet Watch – and their capabilities mean they could take this discovery in their stride.’ 

For a short video about the Global Jet Watch, please see: https://www.globaljetwatch.net/news/what-is-the-global-jet-watch/

Featured image: Global Jet Watch in glow of observatory against starry night sky. Credit: Oxford Science Blog


References: (1) Dominic McLoughlin, Katherine M Blundell, Steven Lee, Chris McCowage, The precessing jets of classical nova YZ Reticuli, Monthly Notices of the Royal Astronomical Society, Volume 503, Issue 1, May 2021, Pages 704–714, https://doi.org/10.1093/mnras/stab581 (2) Dominic McLoughlin, Katherine M Blundell, Steven Lee, Chris McCowage, The onset of jets in classical novae, Monthly Notices of the Royal Astronomical Society, Volume 505, Issue 2, August 2021, Pages 2518–2529, https://doi.org/10.1093/mnras/stab1364


Provided by Oxford Science Blog

Astronomers Probe Layer-Cake Structure Of Brown Dwarf’s Atmosphere (Planetary Science)

Observations may Offer Insight Into The Atmospheres Of Giant Planets

Brown dwarfs are the cosmic equivalent of tweeners. They’re too massive to be planets and too small to sustain nuclear fusion in their cores, which powers stars. Many brown dwarfs are nomadic. They do not orbit stars but drift among them as loners.

Astronomers would like to know how these wayward objects are put together. Do they share any kind of kinship with bloated gas-giant planets like Jupiter? Studying brown dwarfs is much more difficult than studying nearby Jupiter for making comparisons. We can send spacecraft to Jupiter. But astronomers need to look across many light-years to peer down into a brown dwarf’s atmosphere.

Researchers used the giant W. M. Keck Observatory in Hawaii to observe a nearby brown dwarf in infrared light. Unlike Jupiter, the young brown dwarf is still so hot it glows from the inside out, and looks like a carved Halloween pumpkin. Because the brown dwarf has scattered clouds, light shining up from deep down in the dwarf’s atmosphere fluctuates, which the researchers measured. They found that the dwarf’s atmosphere has a layer-cake structure with clouds having different composition at different altitudes.

Jupiter may be the bully planet of our solar system because it’s the most massive planet. But it’s actually a runt compared to many of the giant planets found around other stars.

These alien worlds, called super-Jupiters, weigh up to 13 times Jupiter’s mass. Astronomers have analyzed the composition of some of these monsters. But it has been difficult to study their atmospheres in detail because these gas giants get lost in the glare of their parent stars.

Researchers, however, have a substitute: the atmospheres of brown dwarfs, so-called failed stars that are up to 80 times Jupiter’s mass. These hefty objects form out of a collapsing cloud of gas, as stars do, but lack the mass to become hot enough to sustain nuclear fusion in their cores, which powers stars.

Instead, brown dwarfs share a kinship with super-Jupiters. Both types of objects have similar temperatures and are extremely massive. They also have complex, varied atmospheres. The only difference, astronomers think, is their pedigree. Super-Jupiters form around stars; brown dwarfs often form in isolation.

A team of astronomers, led by Elena Manjavacas of the Space Telescope Science Institute in Baltimore, Maryland, has tested a new way to peer through the cloud layers of these nomadic objects. The researchers used an instrument at the W. M. Keck Observatory in Hawaii to study in near-infrared light the colors and brightness variations of the layer-cake cloud structure in the nearby, free-floating brown dwarf known as 2MASS J22081363+2921215.

The Keck Observatory instrument, called the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE), also analyzed the spectral fingerprints of various chemical elements contained in the clouds and how they change with time. This is the first time astronomers have used the MOSFIRE instrument in this type of study.

These measurements offered Manjavacas a holistic view of the brown dwarf’s atmospheric clouds, providing more detail than previous observations of this object. Pioneered by Hubble observations, this technique is difficult for ground-based telescopes to do because of contamination from Earth’s atmosphere, which absorbs certain infrared wavelengths. This absorption rate changes due to the weather.

“The only way to do this from the ground is using the high-resolution MOSFIRE instrument because it allows us to observe multiple stars simultaneously with our brown dwarf,” Manjavacas explained. “This allows us to correct for the contamination introduced by the Earth’s atmosphere and measure the true signal from the brown dwarf with good precision. So, these observations are a proof-of-concept that MOSFIRE can do these types of studies of brown-dwarf atmospheres.”

Manjavacas will present her results June 9 in a press conference at the virtual meeting of the American Astronomical Society.

The researcher decided to study this particular brown dwarf because it is very young and therefore extremely bright and has not cooled off yet. Its mass and temperature are similar to those of the nearby giant exoplanet Beta Pictoris b, discovered in 2008 near-infrared images taken by the European Southern Observatory’s Very Large Telescope in northern Chile.

“We don’t have the ability yet with current technology to analyze in detail the atmosphere of Beta Pictoris b,” Manjavacas said. “So, we’re using our study of this brown dwarf’s atmosphere as a proxy to get an idea of what the exoplanet’s clouds might look like at different heights of its atmosphere.”

This graphic shows successive layers of clouds in the atmosphere of a nearby, free-floating brown dwarf. Breaks in the upper cloud layers allowed astronomers to probe deeper into the atmosphere of the brown dwarf called 2MASS J22081363+2921215. Brown dwarfs are more massive than planets but too small to sustain nuclear fusion, which powers stars. This illustration is based on infrared observations of the clouds’ colors and brightness variations, as well as the spectral fingerprints of various chemical elements contained in the clouds and atmospheric modeling. Credit: NASA, ESA, STScI, Andi James (STScI)

Both the brown dwarf and Beta Pictoris b are young, so they radiate heat strongly in the near-infrared. They are both members of a flock of stars and sub-stellar objects called the Beta Pictoris moving group, which shares the same origin and a common motion through space. The group, which is about 33 million years old, is the closest grouping of young stars to Earth. It is located roughly 115 light-years away.

While they’re cooler than bona fide stars, brown dwarfs are still extremely hot. The brown dwarf in Manjavacas’ study is a sizzling 2,780 degrees Fahrenheit (1,527 degrees Celsius).

The giant object is about 12 times heavier than Jupiter. As a young body, it is spinning incredibly fast, completing a rotation every 3.5 hours, compared to Jupiter’s 10-hour rotation period. So, clouds are whipping it, creating a dynamic, turbulent atmosphere.

Keck Observatory’s MOSFIRE instrument stared at the brown dwarf for 2.5 hours, watching how the light filtering up through the atmosphere from the dwarf’s hot interior brightens and dims over time. Bright spots that appear on the rotating object indicate regions where researchers can see deeper into the atmosphere, where it is hotter. Infrared wavelengths allow astronomers to peer deeper into the atmosphere. The observations suggest the brown dwarf has a mottled atmosphere with scattered clouds. If viewed close-up, it might resemble a carved Halloween pumpkin, with light escaping from its hot interior.

Its spectrum reveals clouds of hot sand grains and other exotic elements. Potassium iodide traces the object’s upper atmosphere, which also includes magnesium silicate clouds. Moving down in the atmosphere is a layer of sodium iodide and magnesium silicate clouds. The final layer consists of aluminum oxide clouds. The atmosphere’s total depth is 446 miles (718 kilometers). The elements detected represent a typical part of the composition of brown dwarf atmospheres, Manjavacas said.

The researcher and her team used computer models of brown dwarf atmospheres to determine the location of the chemical compounds in each cloud layer.

Manjavacas’ plan is to use Keck Observatory’s MOSFIRE to study other atmospheres of brown dwarfs and compare them to those of gas giants. Future telescopes such as NASA’s James Webb Space Telescope , an infrared observatory scheduled to launch later this year, will provide even more information about a brown dwarf’s atmosphere. “JWST will give us the structure of the entire atmosphere, providing more coverage than any other telescope,” Manjavacas said.

The researcher hopes that MOSFIRE can be used in tandem with JWST to sample a wide range of brown dwarfs. The goal is a better understanding of brown dwarfs and giant planets.

Featured image: Observations of a nearby brown dwarf suggest that it has a mottled atmosphere with scattered clouds and mysterious dark spots reminiscent of Jupiter’s Great Red Spot, as shown in this artist’s concept. The nomadic object, called 2MASS J22081363+2921215, resembles a carved Halloween pumpkin, with light escaping from its hot interior. Brown dwarfs are more massive than planets but too small to sustain nuclear fusion, which powers stars. Though only roughly 115 light-years away, the brown dwarf is too distant for any features to be photographed. Instead, researchers used the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) at the W. M. Keck Observatory in Hawaii to study the colors and brightness variations of the brown dwarf’s layer-cake cloud structure, as seen in near-infrared light. MOSFIRE also collected the spectral fingerprints of various chemical elements contained in the clouds and how they change with time. Credit: NASA, ESA, STScI, Leah Hustak (STScI).


Provided by NASA/Hubble

Variable Emission from the Milky Way’s Supermassive Black Hole (Cosmology)

At the center of our Milky Way lies a supermassive black hole (SMBH) called Sagittarius A* (SgrA*). Supermassive black holes reside at the centers of most galaxies, and when they actively accrete gas and dust onto their surrounding hot disks and environments they radiate across the electromagnetic spectrum. The mass of SgrA* is about four million solar-masses, much smaller than the billions of solar-mass SMBHs seen in some galaxies. However it is relatively close by, only about twenty-five thousand light-years distant, and this proximity provides astronomers with unique opportunities to probe the properties of SMBHs.

Sag A* has been monitored at radio wavelengths since its discovery in the 1950’s. Variability was first reported in the radio in 1984, and subsequent infrared, submillimeter, and X-ray observations confirmed variability and found that it often flares. Monitoring programs have concluded that on average Sgr A* is accreting material at a very low rate, only a few hundredths of an Earth-mass per year. The fascination with SgrA*’s variability has a practical diagnostic reason too: changes in emission are a measure of the dimensions of the region, set by the time for light to travel across it. Flares have been measured that doubled in strength in less than forty-seven seconds, for example, a time that corresponds to a distance about as small as this black hole’s fundamental event horizon size (light cannot escape from within this boundary). These conclusions are in agreement with size inferences made with radio and near infrared interferometry.

CfA astronomers Steve Willner, Giovanni Fazio, Mark Gurwell, Joe Hora, and Howard Smith have been studying the infrared variability of SgrA* with the IRAC camera on Spitzer, combined with simultaneous X-ray and submillimeter variability with Chandra and the Submillimeter Array. They recently teamed with colleagues to analyze and model a comprehensive set of X-ray, near infrared, and submillimeter observations taken by multiple groups over several decades. The statistical modeling examines the relative timing of flare events and the frequency and duration of variability at each of the different wavelengths. The astronomers conclude that the variable emission probably arises predominantly from a region about twice the size of the event horizon, and that the same related physical activity is often producing the multiple events seen at different wavelengths. The quantitative models also imply the presence of a dense plasma of electrons along with a modestly strong magnetic field. These conclusions are the first to show that a simple physical model can explain most of the features of Sgr A*’s variability and the correlations between the X-ray, IR, and submillimeter emission, but many puzzles still remain including the origin of the strongest infrared flares and the reason for the long timescale of variability seen in the submillimeter.

Featured image: A schematic image of one stage of accretion around the supermassive black hole in the Milky Way’s center. Material flows into a spherical region around the black hole with a magnetic field; subsequent compression and expansion of the hot gas produces the infrared and submillimeter emission while scattering produces the X-ray emission. A new paper examines a comprehensive set of multiwavelength, multi-epoch data and presents a relatively simple physical model that can explain most of the variable features. Witzel et al. 2021


Reference: “Rapid Variability of Sgr A* across the Electromagnetic Spectrum,” G. Witzel, G. Martinez, S. P. Willner, E. E. Becklin, H. Boyce, T. Do, A. Eckart, G. G. Fazio, A. Ghez, M. A. Gurwell, D. Haggard, R. Herrero-Illana, J. L. Hora, Z. Li, J. Liu, N. Marchili, Mark R. Morris, Howard A. Smith, M. Subroweit, and J. A. Zensus, The Astrophysical Journal Supplement Series 2021 (in press).


Provided by CFA Harvard

Hubble Sees a Spiral in Good Company (Cosmology)

This image, taken with Hubble’s Wide Field Camera 3, features the spiral galaxy NGC 4680. Two other galaxies, at the far right and bottom center of the image, flank NGC 4680. NGC 4680 enjoyed a wave of attention in 1997, as it played host to a supernova explosion known as SN 1997bp. Australian amateur astronomer Robert Evans identified the supernova and has identified an extraordinary 42 supernova explosions. 

NGC 4680 is actually a rather tricky galaxy to classify. It is sometimes referred to as a spiral galaxy, but it is also sometimes classified as a lenticular galaxy. Lenticular galaxies fall somewhere in between spiral galaxies and elliptical galaxies. While NGC 4680 does have distinguishable spiral arms, they are not clearly defined, and the tip of one arm appears very diffuse. Galaxies are not static, and their morphologies (and therefore their classifications) vary throughout their lifetimes. Spiral galaxies are thought to evolve into elliptical galaxies, most likely by merging with one another, causing them to lose their distinctive spiral structures.

Text credit: European Space Agency (ESA)
Image credit: ESA/Hubble & NASA, A. Riess et al.


Provided by NASA

Citizen Scientists Discover Two Gaseous Planets around a Bright Sun-like Star (Planetary Science)

At night, seven-year-old Miguel likes talking to his father Cesar Rubio about planets and stars. “I try to nurture that,” says Rubio, a machinist in Pomona, California, who makes parts for mining and power generation equipment. 

Now, the boy can claim his father helped discover planets, too. Cesar Rubio is one of thousands of volunteers participating in Planet Hunters TESS, a NASA-funded citizen science project that looks for evidence of planets beyond our solar system, or exoplanets. Citizen science is a way for members of the public to collaborate with scientists. More than 29,000 people worldwide have joined the Planet Hunters TESS effort to help scientists find exoplanets. 

Planet Hunters TESS has now announced the discovery of two exoplanets in a study published online in Monthly Notices of the Royal Astronomical Society, listing Rubio and more than a dozen other citizen scientists as co-authors.

These exotic worlds orbit a star called HD 152843, located about 352 light-years away. This star is about the same mass as the Sun, but almost 1.5 times bigger and slightly brighter.

Planet b, about the size of Neptune, is about 3.4 times bigger than Earth, and completes an orbit around its star in about 12 days. Planet c, the outer planet, is about 5.8 times bigger than Earth, making it a “sub-Saturn,” and its orbital period is somewhere between 19 and 35 days. In our own solar system, both of these planets would be well within the orbit of Mercury, which is about 88 days.

“Studying them together, both of them at the same time, is really interesting to constrain theories of how planets both form and evolve over time,” said Nora Eisner, a doctoral student in astrophysics at the University of Oxford in the United Kingdom and lead author of the study. 

Cesar Rubio and his son Miguel
Cesar Rubio and his son Miguel enjoy talking about space together. Credits: Cesar Rubio

TESS stands for Transiting Exoplanet Survey Satellite, a NASA spacecraft that launched in April 2018. The TESS team has used data from the observatory to identify more than 100 exoplanets and over 2,600 candidates that await confirmation.  

Planet Hunters TESS, operated through the Zooniverse website, began in December 2018, shortly after the first TESS data became publicly available. Volunteers look at graphs showing the brightness of different stars over time. They note which of those plots show a brief dip in the star’s brightness and then an upward swing to the original level. This can happen when a planet crosses the face of its star, blocking out a tiny bit of light — an event called a “transit.” 

The Planet Hunters project shares each brightness plot, called a “light curve,” with 15 volunteers. In the background of the website, an algorithm collects all of the volunteers’ submissions and picks out light curves that multiple volunteers have flagged. Eisner and colleagues then look at the highest-ranked light curves and determine which ones would be good for scientific follow-up. 

Alexander Hubert
Alexander Hubert is studying to become a math and Latin teacher but enjoys astronomy citizen science projects. Credits: Alexander Hubert

Even in an era of sophisticated computing techniques like machine learning, having a large group of volunteers looking through telescope data is a big help to researchers. Since researchers can’t perfectly train computers to identify the signatures of potential planets, the human eye is still valuable. “That’s why a lot of exoplanet candidates are missed, and why citizen science is great,” Eisner said. 

In the case of HD 152843, citizen scientists looked at a plot showing its brightness during one month of TESS observations. The light curve showed three distinct dips, meaning at least one planet could be orbiting the star. All 15 citizen scientists who looked at this light curve flagged at least two transits, and some flagged the light curve on the Planet Hunters TESS online discussion forum. 

Then, scientists took a closer look. By comparing the data to their models, they estimated that two transits came from the inner planet and the other came from a second, outer planet. 

To make sure the transit signals came from planets and not some other source, such as stars that eclipse each other, passing asteroids, or the movements of TESS itself, scientists needed to look at the star with a different method. They used an instrument called HARPS-N (the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere) at the Telescopio Nazionale Galileo in La Palma, Spain, as well as EXPRES (the Extreme Precision Spectrometer), an instrument at Lowell Observatory in Flagstaff, Arizona. Both HARPS and EXPRES look for the presence of planets by examining whether starlight is “wobbling” due to planets orbiting their star. This technique, called the radial velocity method, allows scientists to estimate the mass of a distant planet, too.

Elisabeth Baeten
Elisabeth Baeten has been part of more than a dozen published scientific studies through Zooniverse projects.Credits: Elisabeth Baeten

While scientists could not get a signal clear enough to pinpoint the planets’ masses, they got enough radial velocity data to make mass estimates — about 12 times the mass of Earth for planet b and about 28 times the mass of Earth for planet c. Their measurements validate that signals that indicate the presence of planets; more data are needed for confirmation of their masses. Scientists continue to observe the planetary system with HARPS-N and hope to have more information about the planets soon. 

Researchers may soon have high-tech tools to see if these planets have atmospheres and what gases are present in them. NASA’s James Webb Space Telescope, launching later this year, will be able to look at what kinds of molecules make up the atmospheres of planets like those in this system, especially the larger outer planet. The HD 152843 planets are far too hot and gaseous to support life as we know it, but they are valuable to study as scientists learn about the range of possible planets in our galaxy. 

“We’re taking baby steps towards the direction of finding an Earth-like planet and studying its atmosphere, and continue to push the boundaries of what we can see,” Eisner said. 

The citizen scientists who classified the HD 152843 light curve as a possible source of transiting planets, in addition to three Planet Hunters discussion forum moderators, were invited to have their names listed as co-authors on the study announcing the discovery of these planets. 

One of these citizen scientists is Alexander Hubert, a college student concentrating in mathematics and Latin in Würzburg, Germany, with plans to become a secondary school teacher. So far, he has classified more than 10,000 light curves through Planet Hunters TESS. 

“I regret sometimes that in our times, we have to constrain ourselves to one, maybe two subjects, like for me, Latin and mathematics,” Hubert said. “I’m really grateful that I have the opportunity on Zooniverse to participate in something different.” 

Elisabeth Baeten of Leuven, Belgium, another co-author, works in the administration of reinsurance, and says classifying light curves on Planet Hunters TESS is “relaxing.” Interested in astronomy since childhood, she was one of the original volunteers of Galaxy Zoo, an astronomy citizen science project that started in 2007. Galaxy Zoo invited participants to classify the shapes of distant galaxies.

While Baeten has been part of more than a dozen published studies through Zooniverse projects, the new study is Rubio’s first scientific publication. Astronomy has been a life-long interest, and something he can now share with his son. The two sometimes look at the Planet Hunters TESS website together.  

“I feel that I’m contributing, even if it’s only like a small part,” Rubio said. “Especially scientific research, it’s satisfying for me.”

Featured image: In this artist’s rendering, two gaseous planets orbit the bright star HD 152843. These planets were discovered through the citizen science project Planet Hunters TESS, in collaboration with professional scientists. Credits: NASA/Scott Wiessinger


Provided by NASA

ALMA Discovers Earliest Gigantic Black Hole Storm (Cosmology)

Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) discovered a titanic galactic wind driven by a supermassive black hole 13.1 billion years ago. This is the earliest-yet-observed example of such wind to date and is a telltale sign that huge black holes have a profound effect on the growth of galaxies from the very early history of the Universe.

At the center of many large galaxies hides a supermassive black hole that is millions to billions of times more massive than the Sun. Interestingly, the mass of the black hole is roughly proportional to the mass of the central region (bulge) of the galaxy in the nearby Universe. At first glance, this may seem obvious, but it is actually very strange. The reason is that the sizes of galaxies and black holes differ by about ten orders of magnitude. Based on this proportional relationship between the masses of two objects that are so different in size, astronomers believe that galaxies and black holes grew and evolved together (coevolution) through some kind of physical interaction.

A galactic wind can provide this kind of physical interaction between black holes and galaxies. A supermassive black hole swallows a large amount of matter. As that matter begins to move at high speed due to the black hole’s gravity, it emits intense energy, which can push the surrounding matter outward. This is how the galactic wind is created.

“The question is when did galactic winds come into existence in the Universe?” says Takuma Izumi, the lead author of the research paper and a researcher at the National Astronomical Observatory of Japan (NAOJ). “This is an important question because it is related to an important problem in astronomy: How did galaxies and supermassive black holes coevolve?”

The research team first used NAOJ’s Subaru Telescope to search for supermassive black holes. Thanks to its wide-field observation capability, they found more than 100 galaxies with supermassive black holes in the Universe more than 13 billion years ago [1].

Then, the research team utilized ALMA’s high sensitivity to investigate the gas motion in the host galaxies of the black holes. ALMA observed a galaxy HSC J124353.93+010038.5 (hereafter J1243+0100), discovered by the Subaru Telescope, and captured radio waves emitted by the dust and carbon ions in the galaxy [2].

Detailed analysis of the ALMA data revealed that there is a high-speed gas flow moving at 500 km per second in J1243+0100. This gas flow has enough energy to push away the stellar material in the galaxy and stop the star formation activity. The gas flow found in this study is truly a galactic wind, and it is the oldest observed example of a galaxy with a huge wind of galactic size. The previous record-holder was a galaxy about 13 billion years ago, so this observation pushes the start back another 100 million years.

ALMA image of the distant galaxy J1243+0100 hosting a supermassive black hole in its center. The distribution of the quiet gas in the galaxy is shown in yellow, and the distribution of high-speed galactic wind is shown in blue. The wind is located in the galaxy center, which indicates the supermassive black hole drives the wind. Credit: ALMA (ESO/NAOJ/NRAO), Izumi et al.

The team also measured the motion of the quiet gas in J1243+0100 and estimated the mass of the galaxy’s bulge, based on its gravitational balance, to be about 30 billion times that of the Sun. The mass of the galaxy’s supermassive black hole, estimated by another method, was about 1% of that. The mass ratio of the bulge to the supermassive black hole in this galaxy is almost identical to the mass ratio of black holes to galaxies in the modern Universe. This implies that the coevolution of supermassive black holes and galaxies has been occurring since less than a billion years after the birth of the Universe.

“Our observations support recent high-precision computer simulations which have predicted that coevolutionary relationships were in place even at about 13 billion years ago,” comments Izumi. “We are planning to observe a large number of such objects in the future and hope to clarify whether or not the primordial coevolution seen in this object is an accurate picture of the general Universe at that time.”

Notes

[1] For more information, please see the Subaru Telescope press release issued on March 13, 2019, “Astronomers Discover 83 Supermassive Black Holes in the Early Universe“. The number of galaxies with supermassive black holes discovered was 83 at the time of this announcement, but the number of discoveries has now increased to over 100.

[2] The redshift of this object is z=7.07. Using the cosmological parameters measured with Planck (H0=67.3km/s/Mpc, Ωm=0.315, Λ=0.685: Planck 2013 Results), we can calculate the distance to the object to be 13.1 billion light-years. (Please refer to “Expressing the distance to remote objects” for the details.)

Additional Information

These observation results are presented as Takuma Izumi et al. “Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). XIII. Large-scale Feedback and Star Formation in a Low-Luminosity Quasar at z = 7.07,” in the Astrophysical Journal on June 14, 2021.

The original image release was published by the National Astronomical Observatory of Japan (NAOJ) an ALMA partner on behalf of East Asia.

This research was supported by the Japan Society for Promotion of Science (JSPS) KAKENHI (No. JP20K14531, JP17H06130, 1146 JP17H01114, JP19J00892), the Leading Initiative for Excellent Young Researchers, MEXT, Japan (HJH02007), NAOJ ALMA Scientific Research Grant (2017-06B, 2020-16B), Spanish MICINN (PID2019-10GB-C33 and “Unit of Excellence María de Maeztu 2020-2023” awarded to ICCUB (CEX2019-000918-M)), National Science Foundation of China (11721303, 11991052, 11950410493, 12073003), National Key R&D Program of China (2016YFA0400702), European Research Council (ERC) Consolidator Grant funding scheme (project ConTExt, grant No. 648179), Independent Research Fund Denmark grant DFF–7014-00017, and the Danish National Research Foundation under Grant No. 140.

Featured image: Artist’s impression of a galactic wind driven by a supermassive black hole located in the center of a galaxy. The intense energy emanating from the black hole creates a galaxy-scale flow of gas that blows away the interstellar matter that is the material for forming stars. Credit: ALMA (ESO/NAOJ/NRAO)


Provided by ALMA

SARS-CoV-2 Protease Cuts Human Proteins; Possible Link To COVID-19 Symptoms (Medicine)

The SARS-CoV-2 papain-like protease (PLpro) plays an essential role in processing viral proteins needed for replication. In addition, the enzyme can cut and inactivate some human proteins important for an immune response. Now, researchers reporting in ACS Infectious Diseases have found other targets of PLpro in the human proteome, including proteins involved in cardiovascular function, blood clotting and inflammation, suggesting a link between the inactivation of these proteins and COVID-19 symptoms.

Viruses like SARS-CoV-2 make multiple proteins as one long “polyprotein.” Viral enzymes called proteases recognize specific amino acid sequences in this polyprotein and cut them to release individual proteins. However, some human proteins also contain these sequences (known as homologous host-pathogen sequences, or SSHHPS), including ones involved in generating the innate immune response, which could help protect the virus from the host. Patricia Legler and colleagues wanted to comprehensively identify human proteins that contain SSHHPS, examine their functions and see whether PLpro can cleave them in a test tube.

The researchers developed a computational method to search a database of all known human proteins for sequences similar or identical to the SARS-CoV-2 SSHHPS. The analysis revealed that the proteins with highest sequence identity were those that had cardiovascular, inflammatory, kidney, respiratory or blood-related functions. For example, two of the proteins containing SSHHPS were cardiac myosins, one was an anti-coagulant and another was an anti-inflammatory protein. Inactivation of these proteins by PLpro is consistent with COVID-19 symptoms of heart damage, blood clots and inflammation. The team confirmed that PLpro could cut these protein sequences in vitro. Performing the same analysis on SSHHPS for the Zika viral protease identified proteins associated with neurological development and disorders, consistent with Zika symptoms. These results suggest that the symptoms and virulence of viruses can be predicted directly from their genomic sequences, the researchers say.

The authors acknowledge funding from the Office of the Secretary of the Navy, Naval Innovative Science and Engineering funding and the Office of Naval Research.

The study, “The SARS-CoV-2 SSHHPS Recognized by the Papain-like Protease”, published in ACS Infectious Diseases

Featured image: A SARS-CoV-2 protease cuts human proteins involved in cardiovascular function, blood clotting and inflammation, suggesting a possible link to COVID-19 symptoms.Credit: Lubo Ivanko/Shutterstock.com


Provided by American Chemical Society

Creating A Needle-free COVID-19 Vaccine (Medicine)

Vaccines are mostly synonymous with needles, an efficient and effective way to provide immunity to myriad infections. As COVID-19 vaccination efforts roll out across the U.S. and the world, some experts believe that a vaccine administered through the nose could be just as effective and easier to administer. A cover story in Chemical & Engineering News, the weekly newsmagazine of the American Chemical Society, explains the pros and cons of nasal vaccines.

SARS-CoV-2, the virus that causes COVID-19, often enters the body through the nose when a person inhales. From there it encounters a network of mucosal membranes that form the body’s first line of immune defense, writes Associate Editor Ryan Cross. The cells of mucus membranes create a special type of antibody, which experts say can provide both mucosal and systemic immunity when triggered by a vaccine that is sprayed into the nasal cavity. In contrast, injectable vaccines only trigger a systemic immune response. The COVID-19 vaccines currently available in the U.S. and Europe are highly effective, but there is not enough supply to inoculate the entire world. So, an intranasal version could help offset the disparity, on top of being easier to use.

However, the mucosal immune system is difficult to study, and intranasal vaccines have not generated much interest in recent years. Only one intranasal vaccine (AstraZeneca’s FluMist) has come to market in the U.S., but its higher cost and mixed results compared to the typical flu shot have made it unpopular. In addition, the way the vaccine is administered means that a patient could sneeze out part of it before it’s absorbed by the body, making it unclear how much of the dose a person gets. Despite these challenges, scientists and biotech companies are still working to make intranasal vaccines for respiratory illnesses. The pandemic has provided an opportunity to run clinical trials, and at least one company hopes to manufacture and distribute nasal doses of the COVID-19 vaccine by the end of the year. 

The study, ““Intranasal vaccines aim to stop COVID-19 where it starts”, Chemical & Engineering News

Featured image credit: C&EN/Shutterstock


Provided by American Chemical Society