ST/ Researchers discover the universe’s oldest stars in our galactic backyard
Space biweekly vol.98, 16th May — 30th May
TL;DR
- Astronomers discovered three of the oldest stars in the universe within the Milky Way’s halo, formed between 12 and 13 billion years ago.
- 2. A new Earth-sized exoplanet was found around SPECULOOS-3, an ultracool dwarf star located 55 light-years from Earth.
- WASP-193b, an extremely low-density giant planet, was discovered orbiting a distant Sun-like star.
- An exoplanet with numerous active volcanoes, appearing fiery red from a distance, was identified by astrophysicists.
- A novel method for detecting Population III stars, the universe’s first generation stars, has been developed, holding promise for understanding the universe’s origins.
- Researchers detected atmospheric gases around 55 Cancri e, a hot rocky exoplanet 41 light-years away, the best evidence yet of a rocky planet atmosphere outside our solar system.
- Despite extreme conditions, Venus offers crucial insights into the potential for life on other planets, according to a new paper.
- The first high-resolution map of a massive explosion in a nearby galaxy was created, revealing how intergalactic space is polluted with chemical elements.
- NASA’s James Webb Space Telescope was used to map the weather on the hot gas-giant exoplanet WASP-43 b.
- While studying star-forming gas in a radio galaxy, researchers discovered 49 other galaxies by detecting their gas.
- And more!
Space industry in numbers
The global smart space market size is projected to grow from USD 9.4 billion in 2020 to USD 15.3 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 10.2% during the forecast period. The increasing venture capital funding and growing investments in smart space technology to drive market growth.
Analysts at Morgan Stanley and Goldman Sachs have predicted that economic activity in space will become a multi-trillion-dollar market in the coming decades. Morgan Stanley’s Space Team estimates that the roughly USD 350 billion global space industry could surge to over USD 1 trillion by 2040.
Space industry news
- Inversion Space targets military market with ‘warehouses in space’
- Lithuania 40th nation to sign Artemis Accords
- SatVu aims to revive thermal imaging business in 2025 with two satellites
- Unseenlabs expands focus to land, air, sea and space
- FAA reauthorization bill includes short-term learning period extension
- Seraphim picks nine startups for latest space accelerator program
- Terran Orbital takes charge after switching propulsion suppliers on satellite program
- OneWeb coverage target held up by India regulatory delays
- Tomorrow.io gets DoD contract to launch two microwave weather sensor satellites
- Helium leak delays Starliner crewed test flight
- Intuitive Machines making upgrades to second lunar lander
- India plans Chandrayaan-4 moon sample return, will involve private sector
- NASA selects proposals for new line of Earth science missions
- OHB expects to conclude deal to go private in weeks
- Terran Orbital confirms new satellite deal with Lockheed Martin ahead of earnings
- ULA could fly dummy payload on next Vulcan launch if Dream Chaser is delayed
- NASA and JAXA to operate XRISM as-is despite instrument issue
Latest research
The oldest stars with low neutron-capture element abundances and origins in ancient dwarf galaxies
by Hillary Diane Andales, Ananda Santos Figueiredo, Casey Gordon Fienberg, Mohammad K Mardini, Anna Frebel in Monthly Notices of the Royal Astronomical Society
MIT researchers, including several undergraduate students, have discovered three of the oldest stars in the universe, and they happen to live in our own galactic neighborhood.
The team spotted the stars in the Milky Way’s “halo” — the cloud of stars that envelopes the entire main galactic disk. Based on the team’s analysis, the three stars formed between 12 and 13 billion years ago, the time when the very first galaxies were taking shape. The researchers have coined the stars “SASS,” for Small Accreted Stellar System stars, as they believe each star once belonged to its own small, primitive galaxy that was later absorbed by the larger but still growing Milky Way. Today, the three stars are all that are left of their respective galaxies. They circle the outskirts of the Milky Way, where the team suspects there may be more such ancient stellar survivors.
“These oldest stars should definitely be there, given what we know of galaxy formation,” says MIT professor of physics Anna Frebel. “They are part of our cosmic family tree. And we now have a new way to find them.”
As they uncover similar SASS stars, the researchers hope to use them as analogs of ultrafaint dwarf galaxies, which are thought to be some of the universe’s surviving first galaxies. Such galaxies are still intact today but are too distant and faint for astronomers to study in depth. As SASS stars may have once belonged to similarly primitive dwarf galaxies but are in the Milky Way and as such much closer, they could be an accessible key to understanding the evolution of ultrafaint dwarf galaxies.
“Now we can look for more analogs in the Milky Way, that are much brighter, and study their chemical evolution without having to chase these extremely faint stars,” Frebel says.
The team’s discoveries grew out of a classroom concept. During the 2022 fall semester, Frebel launched a new course, 8.S30(Observational Stellar Archaeology), in which students learned techniques for analyzing ancient stars and then applied those tools to stars that had never been studied before, to determine their origins.
“While most of our classes are taught from the ground up, this class immediately put us at the frontier of research in astrophysics,” Andales says.
The students worked from star data collected by Frebel over the years from the 6.5-meter Magellan-Clay telescope at the Las Campanas Observatory. She keeps hard copies of the data in a large binder in her office, which the students combed through to look for stars of interest. In particular, they were searching ancient stars that formed soon after the Big Bang, which occurred 13.8 billion years ago. At this time, the universe was made mostly of hydrogen and helium and very low abundances of other chemical elements, such as strontium and barium. So, the students looked through Frebel’s binder for stars with spectra, or measurements of starlight, that indicated low abundances of strontium and barium.
Their search narrowed in on three stars that were originally observed by the Magellan telescope between 2013 and 2014. Astronomers never followed up on these particular stars to interpret their spectra and deduce their origins. They were, then, perfect candidates for the students in Frebel’s class.
The students learned how to characterize a star in order to prepare for the analysis of the spectra for each of the three stars. They were able to determine the chemical composition of each one with various stellar models. The intensity of a particular feature in the stellar spectrum, corresponding to a specific wavelength of light, corresponds to a particular abundance of a specific element.
After finalizing their analysis, the students were able to confidently conclude that the three stars did hold very low abundances of strontium, barium, and other elements such as iron, compared to their reference star — our own sun. In fact, one star contained less than 1/10,000 the amount of iron to helium compared to the sun today.
“It took a lot of hours staring at a computer, and a lot of debugging, frantically texting and emailing each other to figure this out,” Santos recalls. “It was a big learning curve, and a special experience.”
The stars’ low chemical abundance did hint that they originally formed 12 to 13 billion years ago. In fact, their low chemical signatures were similar to what astronomers had previously measured for some ancient, ultrafaint dwarf galaxies. Did the team’s stars originate in similar galaxies? And how did they come to be in the Milky Way? On a hunch, the scientists checked out the stars’ orbital patterns and how they move across the sky. The three stars are in different locations throughout the Milky Way’s halo and are estimated to be about 30,000 light years from Earth. (For reference, the disk of the Milky Way spans 100,000 light years across.)
As they retraced each star’s motion about the galactic center using observations from the Gaia astrometric satellite, the team noticed a curious thing: Relative to most of the stars in the main disk, which move like cars on a racetrack, all three stars seemed to be going the wrong way. In astronomy, this is known as “retrograde motion” and is a tipoff that an object was once “accreted,” or drawn in from elsewhere.
“The only way you can have stars going the wrong way from the rest of the gang is if you threw them in the wrong way,” Frebel says.
The fact that these three stars were orbiting in completely different ways from the rest of the galactic disk and even the halo, combined with the fact that they held low chemical abundances, made a strong case that the stars were indeed ancient and once belonged to older, smaller dwarf galaxies that fell into the Milky Way at random angles and continued their stubborn trajectories billions of years later.
Frebel, curious as to whether retrograde motion was a feature of other ancient stars in the halo that astronomers previously analyzed, looked through the scientific literature and found 65 other stars, also with low strontium and barium abundances, that appeared to also be going against the galactic flow.
“Interestingly they’re all quite fast — hundreds of kilometers per second, going the wrong way,” Frebel says. “They’re on the run! We don’t know why that’s the case, but it was the piece to the puzzle that we needed, and that I didn’t quite anticipate when we started.”
The team is eager to search out other ancient SASS stars, and they now have a relatively simple recipe to do so: First, look for stars with low chemical abundances, and then track their orbital patterns for signs of retrograde motion. Of the more than 400 billion stars in the Milky Way, they anticipate that the method will turn up a small but significant number of the universe’s oldest stars. Frebel plans to relaunch the class this fall, and looks back at that first course, and the three students who took their results through to publication, with admiration and gratitude.
“It’s been awesome to work with three women undergrads. That’s a first for me,” she says. “It’s really an example of the MIT way. We do. And whoever says, ‘I want to participate,’ they can do that, and good things happen.”
Detection of an Earth-sized exoplanet orbiting the nearby ultracool dwarf star SPECULOOS-3
by Michaël Gillon, Peter P. Pedersen, Benjamin V. Rackham, et al in Nature Astronomy
The SPECULOOS project, led by the astronomer Michaël Gillon from the University of Liège, has just discovered a new Earth-sized exoplanet around SPECULOOS-3, an “ultracool dwarf” star as small as Jupiter, twice as cold as our Sun, and located 55 light-years from Earth. After the famous TRAPPIST-1, SPECULOOS 3 is the second planetary system discovered around this type of star.
Ultra-cool dwarf stars are the least massive stars in our Universe, similar in size to Jupiter, more than twice as cold, ten times less massive and a hundred times less luminous than our Sun. Their lifespan is over a hundred times longer than that of our star, and they will be the last stars to shine when the Universe becomes cold and dark. Although they are far more common in the Cosmos than Sun-like stars, ultra-cool dwarf stars are still poorly understood due to their low luminosity. In particular, very little is known about their planets, even though they represent a significant fraction of the planetary population of our Milky Way.
It’s against this backdrop that the SPECULOOSconsortium, led by the University of Liège, has just announced the discovery of a new Earth-sized planet orbiting a nearby ultra-cool dwarf star. The SPECULOOS-3 b exoplanet lies around 55 light-years from Earth (which is very close on a cosmic scale! Our galaxy, the Milky Way, stretches over 100,000 light-years). SPECULOOS 3 is only the second planetary system to be discovered around this type of star: “SPECULOOS-3 b is practically the same size as our planet,” explains the astronomer Michaël Gillon, first author of the article. A year, i.e. an orbit around the star, lasts around 17 hours. Days and nights, on the other hand, should never end. We believe that the planet rotates synchronously, so that the same side, called the day side, always faces the star, just like the Moon does for the Earth. On the other hand, the night side hand, would be locked in endless darkness.”
The SPECULOOS (Search for Planets EClipsing ULtra-cOOl Stars) project, initiated and led by astronomer Michaël Gillon, has been specially designed to search for exoplanets around the nearest ultra-cold dwarf stars. “These stars are scattered across the sky, so you must observe them one by one, over a period of weeks, to have a good chance of detecting transiting planets,” continues the researcher. This requires a dedicated network of professional robotic telescopes.” This isthe concept behind SPECULOOS, jointly run by the Universities of Liège, Cambridge, Birmingham, Berne, MIT and ETH Zürich.
“We designed SPECULOOS specifically to observe nearby ultra-cool dwarf stars in search of rocky planets that lend themselves well to detailed studies,” comments Laetitia Delrez, astronomer at the University of Liège. In 2017, our SPECULOOS prototype using the TRAPPIST telescope discovered the famous TRAPPIST-1 system made up of seven Earth-sized planets, including several potentially habitable ones. This was an excellent start!”
The SPECULOOS-3 star is more than twice as cold as our sun, with an average temperature of around 2,600°C. Due to its hyper-short orbit, the planet receives almost sixteen times more energy per second than the Earth does from the Sun and is therefore literally bombarded with high-energy radiation. “In such an environment, the presence of an atmosphere around the planet is highly unlikely,” says Julien de Wit, MIT professor and co-director of the SPECULOOS Northern Observatory and its Artemis telescope, co-developed by the University of Liège and MIT, and the mainstay of this discovery. The fact that this planet has no atmosphere could be a plus in several respects. For example, it could enable us to learn a great deal about ultra-cool dwarf stars, which in turn will make possible more in-depth studies of their potentially habitable planets.”
SPECULOOS-3 b is proving to be an excellent target for the JWST space telescope, to be launched in 2021, whose data will revolutionize our vision of the Universe. “With the JWST, we could even study the mineralogy of the planet’s surface!” enthuses Elsa Ducrot, a former researcher at the University of Liège now based at Paris Observatory.
“This discovery demonstrates the ability of our SPECULOOS-North observatory to detect Earth-sized exoplanets suitable for detailed study. And this is just the beginning! Thanks to the financial support of the Walloon Region and the University of Liège, two new telescopes, Orion and Apollo, will soon join Artemis on the plateau of the Teide volcano in Tenerife, to speed up the hunt for these fascinating planets” concludes Michaël Gillon.
An extended low-density atmosphere around the Jupiter-sized planet WASP-193 b
by Khalid Barkaoui, Francisco J. Pozuelos, Coel Hellier, Barry Smalley, et al in Nature Astronomy
An international team led by researchers from the EXOTIC Laboratory of the University of Liège, in collaboration with MIT and the Astrophysics Institute in Andalusia, has just discovered WASP-193b, an extraordinarily low-density giant planet orbiting a distant Sun-like star.
This new planet, located 1,200 light-years from Earth, is 50% larger than Jupiter but seven times less massive, giving it an extremely low density comparable to that of cotton candy. “WASP-193b is the second least dense planet discovered to date, after Kepler-51d, which is much smaller,” explains Khalid Barkaoui, a Postdcotral Researcher at ULiège’s EXOTIC Laboratory and first author of the article. Its extremely low density makes it a real anomaly among the more than five thousand exoplanets discovered to date. This extremely-low-density cannot be reproduced by standard models of irradiated gas giants, even under the unrealistic assumption of a coreless structure.”
The new planet was initially spotted by the Wide Angle Search for Planets (WASP), an international collaboration of academic institutions that together operated two robotic observatories, one in the northern hemisphere and the other in the south. Each observatory used an array of wide-angle cameras to measure the brightness of thousands of individual stars across the entire sky. In data taken between 2006 and 2008, and again from 2011 to 2012, the WASP-South observatory detected periodic transits, or dips in light, from the star WASP-193. Astronomers determined that the star’s periodic dips in brightness were consistent with a planet passing in front of the star every 6.25 days. The scientists measured the amount of light the planet blocked with each transit, which gave them an estimate of the planet’s size.
The team used then the TRAPPIST-South and SPECULOOS-South observatories — directed by Michaël Gillon, FNRS Research Director and astrophysicist at ULiège — located in the Atacama Desert in Chile to measure the planetary signal in different wavelengths and to validate the planetary nature of the eclipsing object. Finally, they also used spectroscopic observations collected by the HARPS and CORALIE spectrographs — also located in Chile (ESO)- to measure the mass of the planet. To their great surprise, the accumulated measurements revealed an extremely low density for the planet. Its mass and its size, they calculated, were about 0.14 and 1.5 that of Jupiter, respectively. The resulting density came out to about 0.059 grams per cubic centimeter. Jupiter’s density, in contrast, is about 1.33 grams per cubic centimeter; and Earth is a more substantial 5.51 grams per cubic centimeter. One of the materials closest in density to the new, puffy planet, is cotton candy, which has a density of about 0.05 grams per cubic centimeter.
“The planet is so light that it’s difficult to think of an analogous, solid-state material,” says Julien de Wit, professor at Massachusetts Institute of Technology (MIT) and co-author. “The reason why it’s close to cotton candy is because both are pretty much air. The planet is basically super fluffy.”
The researchers suspect that the new planet is made mostly from hydrogen and helium, like most other gas giants in the galaxy. For WASP-193b, these gases likely form a hugely inflated atmosphere that extends tens of thousands of kilometers farther than Jupiter’s own atmosphere. Exactly how a planet can inflate so much is a question that no existing theory of planetary formation can yet answer. It certainly requires a significant deposit of energy deep into the planet’s interior, but the details of the mechanism are not yet understood.
“We don’t know where to put this planet in all the formation theories we have right now, because it’s an outlier of all of them. We cannot explain how this planet was formed. Looking more closely at its atmosphere will allow us to constrain an evolutionary path of this planet, adds Francisco Pozuelos, astronomer at the Instituto de Astrofisica de Andalucia (IAA-CSIC, Granada, Spain).”
“WASP-193b is a cosmic mystery. Solving it will require some more observational and theoretical work, notably to measure its atmospheric properties with the JWST space telescope and to confront them to different theoretical mechanisms that possibly result in such an extreme inflation”, concludes Khalid Barkaoui.
A Perfect Tidal Storm: HD 104067 Planetary Architecture Creating an Incandescent World
by Stephen R. Kane, Tara Fetherolf, Zhexing Li, Alex S. Polanski, Andrew W. Howard, Howard Isaacson, Teo Močnik, Sadie G. Welter in The Astronomical Journal
UC Riverside astrophysicist Stephen Kane had to double check his calculations. He wasn’t sure the planet he was studying could be as extreme as it seemed.
Kane never expected to learn that a planet in this faraway star system is covered with so many active volcanoes that seen from a distance it would take on a fiery, glowing-red hue.
“It was one of those discovery moments that you think, ‘wow, it’s amazing this can actually exist,” Kane said.
Launched in 2018, NASA’s Transiting Exoplanet Survey Satellite, or TESS, searches for exoplanets — planets outside our solar system — that orbit the brightest stars in the sky, including those that could support life. Kane was studying a star system called HD 104067 about 66 light years away from our sun that was already known to harbor a giant planet. TESS had just discovered signals for a new rocky planet in that system. In gathering data about that planet, he unexpectedly found yet another one, bringing the total number of known planets in the system to three.
The new TESS-discovered planet is a rocky planet like Earth, but 30% larger. However, unlike Earth, it has more in common with Io, Jupiter’s rocky innermost moon and the most volcanically active body in our solar system.
“This is a terrestrial planet that I would describe as Io on steroids,” Kane said. “It’s been forced into a situation where it’s constantly exploding with volcanoes. At optical wavelengths you would be able to see a glowing, red-hot planet with a molten lava surface.”
Kane calculated that the surface temperature of the new planet, TOI-6713.01, would be 2,600 degrees Kelvin, which is hotter than some stars. Gravitational forces are to blame for the volcanic activity both on Io and on this planet. Io is very close to Jupiter. Kane explained that Jupiter’s other moons force Io into an elliptical or “eccentric” orbit around the planet, which itself has a very strong gravitational pull.
“If the other moons weren’t there, Io would be in a circular orbit around the planet, and it would be quiet on the surface. Instead, Jupiter’s gravity squeezes Io so much that it erupts in volcanoes constantly,” Kane said.
Similarly, there are two planets in the HD 104067 system that are farther away from the star than this new planet. Those outer planets are also forcing the inner rocky planet into an eccentric orbit around the star that squeezes it as it orbits and rotates. Kane likens this scenario to racquetball, where the small rubber game ball bounces more and gets hotter as it is constantly hit with paddles. This effect is called tidal energy, a term used when referencing one body’s gravitational effect on another body. On Earth, tides are mostly the result of the moon’s gravity dragging our oceans along.
Moving forward, Kane and his colleagues would like to measure the mass of the flaming planet and learn its density. This would tell them how much material is available to blow out of the volcanoes. Kane said that tidal effects on planets hasn’t historically been a big focus of exoplanet research. Perhaps that will change with this discovery.
“This teaches us a lot about the extremes of how much energy can be pumped into a terrestrial planet, and the consequences of that,” Kane said. “While we know that stars contribute to the heat of a planet, the vast majority of the energy here is tidal and that cannot be ignored.”
Detecting Population III Stars through Tidal Disruption Events in the Era of JWST and Roman
by Rudrani Kar Chowdhury, Janet N. Y. Chang, Lixin Dai, Priyamvada Natarajan in The Astrophysical Journal Letters
A recent study led by the research group of Professor Jane Lixin DAI of the Department of Physics at The University of Hong Kong (HKU) has discovered a novel method for detecting the first-generations stars, known as Population III (Pop III) stars, which have never been directly detected. The research has been widely acknowledged by the international astronomy community with a highlight from the Space Telescope Science Institute, which operates several NASA telescopes. These potential discoveries about Pop III stars hold the promise of unlocking the secrets of the universe’s origin and providing a deeper understanding of the remarkable journey from the primordial cosmos to the world we inhabit today.
Shortly after the Universe began with the Big Bang, the first stars, composed mainly of hydrogen and helium, began to form. The properties of these first-generation stars, Pop III, are very different from stars like our own Sun or even the ones that are forming today. They were tremendously hot, gigantic in size and mass, but very short-lived. Pop III stars are the first factories to synthesise most elements heavier than hydrogen and helium around us today. They are also very important for forming later generations of stars and galaxies. However, there have not been convincing direct detections of Pop III stars up to now, as these stars formed in the early universe are very far away and way too faint for any of our telescopes on the ground or in space.
For the first time, HKU scientists discovered a novel method for detecting these first stars in the early Universe. A recent study led by the research group of Professor Jane Lixin DAI of the Department of Physics at HKU proposed that a Pop III star can be torn apart into pieces by tidal force if it wanders into the vicinity of a massive black hole. In such a tidal disruption event (TDE), the black hole feasts on the stellar debris and produces very luminous flares. The researchers investigated the complex physical process involved and demonstrated that these flares can shine across billions of light years to reach us today. Most importantly, they have found that the unique signatures of these TDE flares can be used to identify the existence of Pop III stars and gain insights into their properties.
“As the energetic photons travel from a very faraway distance, the timescale of the flare will be stretched due to the expansion of the Universe. These TDE flares will rise and decay over a very long period of time, which sets them apart from the TDEs of solar-type stars in the nearby Universe,” said Professor Jane Dai, principal investigator and the corresponding author of the project. “Interestingly, not only are the timescales of the flares are stretched, so is their wavelength. The optical and ultraviolet light emitted by the TDE will be transferred to infrared emissions when reaching the Earth.” Dr Rudrani KAR CHOWDHURY, Postdoctoral Fellow of the Department of Physics at HKU and the first author of the paper, further added.
What makes the discovery more exciting is that two NASA flagship missions, the recently launched James Webb Space Telescope (JWST) and the upcoming Nancy Grace Roman Space Telescope (Roman), have the capability to observe such infrared emissions from great distances. Professor Priya NATARAJAN of the Department of Astronomy and Physics at Yale University and a co-author of the paper mentioned, “Roman’s unique capabilities of simultaneously being able to observe a large area of the sky and peeking deep into early Universe makes it a promising probe for detecting these Pop III TDE flares, which would in turn serve as an indirect discovery of Pop III stars.” Ms Janet CHANG, a PhD student at the Department of Physics at HKU and co-author of the paper, added, “We expect that a few dozens of these events will be detected by Roman every year if the right observation strategy is pursued.” With these findings in mind, the next decade presents significant potential for identifying these distinct sources, leading to exciting revelations about Pop III stars and unraveling the mysteries of the universe’s inception.
A secondary atmosphere on the rocky Exoplanet 55 Cancri e
by Renyu Hu, Aaron Bello-Arufe, Michael Zhang, Kimberly Paragas, Mantas Zilinskas, Christiaan van Buchem, Michael Bess, Jayshil Patel, Yuichi Ito, Mario Damiano, Markus Scheucher, Apurva V. Oza, Heather A. Knutson, Yamila Miguel, Diana Dragomir, Alexis Brandeker, Brice-Olivier Demory in Nature
Researchers using NASA’s James Webb Space Telescope may have detected atmospheric gases surrounding 55 Cancri e, a hot rocky exoplanet 41 light-years from Earth. This is the best evidence to date for the existence of any rocky planet atmosphere outside our solar system.
Renyu Hu from NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, is lead author on a paper. “Webb is pushing the frontiers of exoplanet characterization to rocky planets,” Hu said. “It is truly enabling a new type of science.”
55 Cancri e (image below, details/download), also known as Janssen, is one of five known planets orbiting the Sun-like star 55 Cancri, in the constellation Cancer. With a diameter nearly twice that of Earth and density slightly greater, the planet is classified as a super-Earth: larger than Earth, smaller than Neptune, and likely similar in composition to the rocky planets in our solar system.
To describe 55 Cancri e as “rocky,” however, could leave the wrong impression. The planet orbits so close to its star (about 1.4 million miles, or one-twenty-fifth the distance between Mercury and the Sun) that its surface is likely to be molten — a bubbling ocean of magma. With such a tight orbit, the planet is also likely to be tidally locked, with a dayside that faces the star at all times and a nightside in perpetual darkness. In spite of numerous observations since it was discovered to transit in 2011, the question of whether or not 55 Cancri e has an atmosphere — or even could have one given its high temperature and the continuous onslaught of stellar radiation and wind from its star — has gone unanswered.
“I’ve worked on this planet for more than a decade,” said Diana Dragomir, an exoplanet researcher at the University of New Mexico and co-author on the study. “It’s been really frustrating that none of the observations we’ve been getting have robustly solved these mysteries. I am thrilled that we’re finally getting some answers!”
Unlike the atmospheres of gas giant planets, which are relatively easy to spot (the first was detected by NASA’s Hubble Space Telescope more than two decades ago), thinner and denser atmospheres surrounding rocky planets have remained elusive. Previous studies of 55 Cancri e using data from NASA’s now-retired Spitzer Space Telescope suggested the presence of a substantial atmosphere rich in volatiles (molecules that occur in gas form on Earth) like oxygen, nitrogen, and carbon dioxide. But researchers could not rule out another possibility: that the planet is bare, save for a tenuous shroud of vaporized rock, rich in elements like silicon, iron, aluminum, and calcium. “The planet is so hot that some of the molten rock should evaporate,” explained Hu.
To distinguish between the two possibilities, the team used Webb’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) to measure 4- to 12-micron infrared light coming from the planet. Although Webb cannot capture a direct image of 55 Cancri e, it can measure subtle changes in light from the system as the planet orbits the star.
By subtracting the brightness during the secondary eclipse (image below, details/download), when the planet is behind the star (starlight only), from the brightness when the planet is right beside the star (light from the star and planet combined), the team was able to calculate the amount of various wavelengths of infrared light coming from the dayside of the planet. This method, known as secondary eclipse spectroscopy, is similar to that used by other research teams to search for atmospheres on other rocky exoplanets, like TRAPPIST-1 b.
The first indication that 55 Cancri e could have a substantial atmosphere came from temperature measurements based on its thermal emission (image below, details/download), or heat energy given off in the form of infrared light. If the planet is covered in dark molten rock with a thin veil of vaporized rock or no atmosphere at all, the dayside should be around 4,000 degrees Fahrenheit (~2,200 degrees Celsius).
“Instead, the MIRI data showed a relatively low temperature of about 2,800 degrees Fahrenheit [~1540 degrees Celsius],” said Hu. “This is a very strong indication that energy is being distributed from the dayside to the nightside, most likely by a volatile-rich atmosphere.” While currents of lava can carry some heat around to the nightside, they cannot move it efficiently enough to explain the cooling effect.
When the team looked at the NIRCam data, they saw patterns consistent with a volatile-rich atmosphere. “We see evidence of a dip in the spectrum between 4 and 5 microns — less of this light is reaching the telescope,” explained co-author Aaron Bello-Arufe, also from NASA JPL. “This suggests the presence of an atmosphere containing carbon monoxide or carbon dioxide, which absorb these wavelengths of light.” A planet with no atmosphere or an atmosphere consisting only of vaporized rock would not have this specific spectral feature.
“We’ve spent the last ten years modelling different scenarios, trying to imagine what this world might look like,” said co-author Yamila Miguel from the Leiden Observatory and the Netherlands Institute for Space Research (SRON). “Finally getting some confirmation of our work is priceless!”
Venus as an Anchor Point for Planetary Habitability
by Stephen R. Kane, Paul K. Byrne in Submitted to arXiv
Despite surface temperatures hot enough to melt lead, lava-spewing volcanoes, and puffy clouds of sulfuric acid, uninhabitable Venus offers vital lessons about the potential for life on other planets, a new paper argues.
“We often assume that Earth is the model of habitability, but if you consider this planet in isolation, we don’t know where the boundaries and limitations are,” said UC Riverside astrophysicist and paper first author Stephen Kane. “Venus gives us that.”
The paper compiles much of the known information about Earth and Venus. It also describes Venus as an anchor point from which scientists can better understand the conditions that preclude life on planets around other stars. Though it also features a pressure cooker-like atmosphere that would instantly flatten a human, Earth and Venus share some similarities. They have roughly the same mass and radius. Given the proximity to that planet, it’s natural to wonder why Earth turned out so differently. Many scientists assume that insolation flux, the amount of energy Venus receives from the sun, caused a runaway greenhouse situation that ruined the planet.
“If you consider the solar energy received by Earth as 100%, Venus collects 191%. A lot of people think that’s why Venus turned out differently,” Kane said. “But hold on a second. Venus doesn’t have a moon, which is what gives Earth things like ocean tides and influenced the amount of water here.”
In addition to some of the known differences, more NASA missions to Venus would help clear up some of the unknowns. Scientists don’t know the size of its core, how it got to its present, relatively slow rotation rate, how its magnetic field changed over time, or anything about the chemistry of the lower atmosphere.
“Venus doesn’t have a detectable magnetic field. That could be related to the size of its core,” Kane said. “Core size also give us information about how a planet cools itself. Earth has a mantle circulating heat from its core. We don’t know what’s happening inside Venus.”
A terrestrial planet’s interior also influences its atmosphere. That is the case on Earth, where our atmosphere is largely the result of volcanic outgassing. NASA does have twin missions to Venus planned for the end of this decade, and Kane is assisting with both of them. The DAVINCI mission will probe the acid-filled atmosphere to measure noble gases and other chemical elements.
“DAVINCI will measure the atmosphere all the way from the top to the bottom. That will really help us build new climate models and predict these kinds of atmospheres elsewhere, including on Earth, as we keep increasing the amount of CO2,” Kane said.
The VERITAS mission, led by NASA’s Jet Propulsion Laboratory, won’t land on the surface but it will allow scientists to create detailed 3D landscape reconstructions, revealing whether the planet has active plate tectonics or volcanoes.
“Currently, our maps of the planet are very incomplete. It’s very different to understand how active the surface is, versus how it may have changed through time. We need both kinds of information,” Kane said.
Ultimately, the paper advocates for missions like these to Venus for two main reasons. One is the ability, with better data, to use Venus to ensure inferences about life on farther-flung planets are correct.
“The sobering part of the search for life elsewhere in the universe is that we’re never going to have in situ data for an exoplanet. We aren’t going there, landing, or taking direct measurements of them,” Kane said.
“If we think another planet has life on the surface, we might not ever know we’re wrong, and we’d be dreaming about a planet with life that doesn’t have it. We are only going to get that right by properly understanding the Earth-size planets we can visit, and Venus gives us that chance.”
The other reason to research Venus is that it offers a preview of what Earth’s future could look like.
“One of the main reasons to study Venus is because of our sacred duties as caretakers of this planet, to preserve its future. My hope is that through studying the processes that produced present-day Venus, especially if Venus had a more temperate past that’s now devastated, there are lessons there for us. It can happen to us. It’s a question of how and when,” Kane said.
MAUVE: a 6 kpc bipolar outflow launched from NGC 4383, one of the most H i-rich galaxies in the Virgo cluster
by Adam B Watts, Luca Cortese, Barbara Catinella, Amelia Fraser-McKelvie, Eric Emsellem, Lodovico Coccato, Jesse van de Sande, Toby H Brown, Yago Ascasibar, Andrew Battisti, Alessandro Boselli, Timothy A Davis, Brent Groves, Sabine Thater in Monthly Notices of the Royal Astronomical Society
A team of international researchers studied galaxy NGC 4383, in the nearby Virgo cluster, revealing a gas outflow so large that it would take 20,000 years for light to travel from one side to the other.
Lead author Dr Adam Watts, from The University of Western Australia node at the International Centre for Radio Astronomy Research (ICRAR), said the outflow was the result of powerful stellar explosions in the central regions of the galaxy that could eject enormous amounts of hydrogen and heavier elements. The mass of gas ejected is equivalent to more than 50 million Suns.
“Very little is known about the physics of outflows and their properties because outflows are very hard to detect,” Dr Watts said. “The ejected gas is quite rich in heavy elements giving us a unique view of the complex process of mixing between hydrogen and metals in the outflowing gas.
“In this particular case, we detected oxygen, nitrogen, sulphur and many other chemical elements.”
Gas outflows are crucial to regulate how fast and for how long galaxies can keep forming stars. The gas ejected by these explosions pollutes the space between stars within a galaxy, and even between galaxies, and can float in the intergalactic medium forever. The high-resolution map was produced with data from the MAUVE survey, co-led by ICRAR researchers Professors Barbara Catinella and Luca Cortese, who were also co-authors of the study. The survey used the MUSE Integral Field Spectrograph on the European Southern Observatory’s Very Large Telescope, located in northern Chile.
“We designed MAUVE to investigate how physical processes such as gas outflows help stop star formation in galaxies,” Professor Catinella said. “NGC 4383 was our first target, as we suspected something very interesting was happening, but the data exceeded all our expectations.
“We hope that in the future, MAUVE observations reveal the importance of gas outflows in the local Universe with exquisite detail.”
Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b
by Taylor J. Bell, Nicolas Crouzet, Patricio E. Cubillos, et al in Nature Astronomy
An international team of researchers has successfully used NASA’s James Webb Space Telescope to map the weather on the hot gas-giant exoplanet WASP-43 b.
Precise brightness measurements over a broad spectrum of mid-infrared light, combined with 3D climate models and previous observations from other telescopes, suggest the presence of thick, high clouds covering the nightside, clear skies on the dayside, and equatorial winds upwards of 5,000 miles per hour mixing atmospheric gases around the planet. The investigation is just the latest demonstration of the exoplanet science now possible with Webb’s extraordinary ability to measure temperature variations and detect atmospheric gases trillions of miles away.
WASP-43 b is a “hot Jupiter” type of exoplanet: similar in size to Jupiter, made primarily of hydrogen and helium, and much hotter than any of the giant planets in our own solar system. Although its star is smaller and cooler than the Sun, WASP-43 b orbits at a distance of just 1.3 million miles — less than 1/25th the distance between Mercury and the Sun.
With such a tight orbit, the planet is tidally locked, with one side continuously illuminated and the other in permanent darkness. Although the nightside never receives any direct radiation from the star, strong eastward winds transport heat around from the dayside. Since its discovery in 2011, WASP-43 b has been observed with numerous telescopes, including NASA’s Hubble and now-retired Spitzer space telescopes.
“With Hubble, we could clearly see that there is water vapor on the dayside. Both Hubble and Spitzer suggested there might be clouds on the nightside,” explained Taylor Bell, researcher from the Bay Area Environmental Research Institute and lead author of a study. “But we needed more precise measurements from Webb to really begin mapping the temperature, cloud cover, winds, and more detailed atmospheric composition all the way around the planet.”
Although WASP-43 b is too small, dim, and close to its star for a telescope to see directly, its short orbital period of just 19.5 hours makes it ideal for phase curve spectroscopy, a technique that involves measuring tiny changes in brightness of the star-planet system as the planet orbits the star.
Since the amount of mid-infrared light given off by an object depends largely on how hot it is, the brightness data captured by Webb can then be used to calculate the planet’s temperature. The team used Webb’s MIRI (Mid-Infrared Instrument) to measure light from the WASP-43 system every 10 seconds for more than 24 hours. “By observing over an entire orbit, we were able to calculate the temperature of different sides of the planet as they rotate into view,” explained Bell. “From that, we could construct a rough map of temperature across the planet.”
The measurements show that the dayside has an average temperature of nearly 2,300 degrees Fahrenheit (1,250 degrees Celsius) — hot enough to forge iron. Meanwhile, the nightside is significantly cooler at 1,100 degrees Fahrenheit (600 degrees Celsius). The data also helps locate the hottest spot on the planet (the “hotspot”), which is shifted slightly eastward from the point that receives the most stellar radiation, where the star is highest in the planet’s sky. This shift occurs because of supersonic winds, which move heated air eastward.
“The fact that we can map temperature in this way is a real testament to Webb’s sensitivity and stability,” said Michael Roman, a co-author from the University of Leicester in the U.K.
To interpret the map, the team used complex 3D atmospheric models like those used to understand weather and climate on Earth. The analysis shows that the nightside is probably covered in a thick, high layer of clouds that prevent some of the infrared light from escaping to space. As a result, the nightside — while very hot — looks dimmer and cooler than it would if there were no clouds.
The broad spectrum of mid-infrared light captured by Webb also made it possible to measure the amount of water vapor (H2O) and methane (CH4) around the planet. “Webb has given us an opportunity to figure out exactly which molecules we’re seeing and put some limits on the abundances,” said Joanna Barstow, a co-author from the Open University in the U.K.
The spectra show clear signs of water vapor on the nightside as well as the dayside of the planet, providing additional information about how thick the clouds are and how high they extend in the atmosphere. Surprisingly, the data also shows a distinct lack of methane anywhere in the atmosphere. Although the dayside is too hot for methane to exist (most of the carbon should be in the form of carbon monoxide), methane should be stable and detectable on the cooler nightside.
“The fact that we don’t see methane tells us that WASP-43b must have wind speeds reaching something like 5,000 miles per hour,” explained Barstow. “If winds move gas around from the dayside to the nightside and back again fast enough, there isn’t enough time for the expected chemical reactions to produce detectable amounts of methane on the nightside.”
The team thinks that because of this wind-driven mixing, the atmospheric chemistry is the same all the way around the planet, which wasn’t apparent from past work with Hubble and Spitzer.
A serendipitous discovery of HI-rich galaxy groups with MeerKA
by Marcin Glowacki, Leah Albrow, Tristan Reynolds, Edward Elson, Elizabeth Mahony, James Allison in Monthly Notices of Royal Astronomical Society
A team of international astronomers have discovered 49 new gas-rich galaxies using the MeerKAT radio telescope in South Africa from observations that were not even three hours long and were made possible by IDIA (Inter-University Institute of Data Intensive Astronomy).
Dr. Marcin Glowacki, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) in Western Australia, led the research, which aimed to study the star-forming gas in a single radio galaxy. Although the team didn’t find any star-forming gas in the galaxy they were studying, Dr. Glowacki instead discovered other galaxies while inspecting the data. In total, the gas of 49 galaxies was detected. Dr Glowacki said this was a great example of how fantastic an instrument like MeerKAT is for finding the star-forming gas in galaxies.
“I did not expect to find almost fifty new galaxies in such a short time,” he said. “By implementing different techniques for finding galaxies, which are used for other MeerKAT surveys, we were able to detect all of these galaxies and reveal their gas content.”
The new galaxies have been informally nicknamed the 49ers — a reference to the 1849 California gold rush miners. Dr Glowacki views the 49 new galaxies as valuable as gold nuggets in our night sky. Many galaxies are near each other, forming galaxy groups, with several identified in one observation. Three galaxies, in particular, are directly connected by their gas.
Dr Glowacki said, “These three are particularly interesting, as by studying the galaxies at other wavelengths of light, we discovered the central galaxy is forming many stars. It is likely stealing the gas from its companion galaxies to fuel its star formation, which may lead the other two to become inactive.”
Professor Ed Elson, from the University of the Western Cape and a co-author of the paper, said, “This discovery highlights the raw power of the MeerKAT telescope as an imaging instrument. The methods we developed and implemented to study the 49ers will be useful for MeerKAT large science surveys, and smaller observing campaigns such as ours.”
Subscribe to Paradigm!
Medium. Twitter. Telegram. Telegram Chat. Reddit. LinkedIn.
Main sources
Research articles
