SPACE
Flyby of asteroid Dinkinesh reveals a surprisingly complex history
SwRI-led Lucy mission to Jupiter’s Trojan asteroids finds interesting attractions along the way
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AS NASA’S LUCY SPACECRAFT FLEW PAST THE ASTEROID DINKINESH, ITS L’LORRI INSTRUMENT PRODUCED STEREOGRAPHIC IMAGES OF THE NOV. 1, 2023, ENCOUNTER. THE SWRI-LED SCIENCE TEAM ANALYZED PROCESSED IMAGES, IDENTIFYING A TROUGH (YELLOW DOTS) AND RIDGE (ROSE DOTS) ON ITS SURFACE. THE FINAL PANEL SHOWS A SIDE VIEW OF DINKINESH AND ITS SATELLITE SELAM TAKEN A FEW MINUTES AFTER CLOSEST APPROACH.
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CREDIT: NASA/SWRI/JOHNS HOPKINS APL/NOIRLAB
SAN ANTONIO — May 30, 2024 —When NASA’s Lucy spacecraft flew past the tiny main belt asteroid Dinkinesh last November, the Southwest Research Institute-led mission discovered a trough and ridge structure on the main asteroid as well as the first-ever-encountered contact binary satellite. The flyby data of this half-mile-wide object revealed a dramatic history of sudden breakups and transformation.
Scientists think a big chunk of Dinkinesh suddenly shifted, excavating the trough and flinging debris into its vicinity. Some materials fell back to the asteroid body, forming the ridge, while others coalesced to form a contact binary satellite known as Selam. The complex shapes show that Dinkinesh and Selam have significant internal strength and a complex, dynamic history.
“To understand the history of planets like Earth, we need to understand how objects behave when they hit each other, which is affected by the strength of the planetary materials,” said SwRI’s Hal Levison, principal investigator for the Lucy mission and lead author of May 29 paper in Nature discussing this research. “We think the planets formed as zillions of objects orbiting the Sun, like asteroids, ran into each other. Whether objects break apart when they hit or stick together has a lot to do with their strength and internal structure.”
Researchers think that Dinkinesh is revealing its internal structure in how it has responded to stress. Over millions of years, its surface was unevenly heated by the Sun. This slight imbalance caused Dinkinesh to gradually rotate faster. Stress built over time and was suddenly released as a large piece of the asteroid shifted into a more elongated shape.
“The Lucy science team started gathering data about Dinkinesh using telescopes in January 2023, when it was added to our list of targets,” said SwRI’s Simone Marchi, Lucy deputy principal investigator and the paper’s second author. “Thanks to the telescopic data, we thought we had quite a good picture of what Dinkinesh would look like, and we were thrilled to make so many unexpected discoveries.”
If the structure of Dinkinesh were weaker, more like the rubble-pile asteroid Bennu, the fragmented materials would have gradually moved toward the equator and flown off into orbit as it spun faster. However, images suggest Dinkinesh has more cohesive strength, because it could hold together longer, more like a rock that suddenly gives way under stress, fragmenting into large pieces.
“This flyby showed us Dinkinesh has some strength and allowed us to do a little ‘archeology’ to see how this tiny asteroid evolved,” Levison said. “When it broke apart, a disk of material formed, some of which rained back onto the surface, creating the ridge.”
The rest of the disk materials likely formed the double-lobed moon Selam, a contact binary. How this unusual moon ultimately formed remains a mystery, one that the scientists are already digging into.
“We see ridges around asteroids’ equators regularly among near-Earth asteroids, but seeing one up close, around an asteroid with a satellite, helps to unravel some of the possible histories of these binary asteroids,” said SwRI’s Kevin Walsh, an astrophysicist specializing in planetary formation.
Dinkinesh and its satellite are the first two of 11 asteroids that Lucy plans to explore over its 12-year journey. After skimming the inner edge of the main asteroid belt, Lucy is now heading back toward Earth for a gravity assist in December 2024. That close flyby will slingshot the spacecraft back through the main asteroid belt, where it will observe asteroid Donaldjohanson in 2025 en route to the Trojan asteroids, two swarms of ancient bodies that lead and trail Jupiter in its orbit around the Sun. Starting in 2027, Lucy is scheduled to fly past eight Trojans in both asteroid swarms.
Lucy’s principal investigator is from SwRI’s Solar System Science and Exploration Division in Boulder, Colorado. SwRI is based in San Antonio. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering, and safety and mission assurance. Lockheed Martin Space in Littleton, Colorado, built and operates the spacecraft. Lucy is the 13th mission in NASA’s Discovery Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Discovery Program for the Science Mission Directorate at NASA Headquarters in Washington.
For a movie about the Dinkinesh-Selam encounter, visit: https://youtu.be/aE3ixq2yrcw?si=ICxGRZeZFDhYO5Nq
To read the May 29 paper in Nature discussing Dinkinesh research, visit https://www.nature.com/articles/s41586-024-07378-0.
For more information visit https://www.nasa.gov/lucy or https://www.swri.org/planetary-science.
JOURNAL
Nature
NASA’s James Webb Space Telescope finds most distant known galaxy
NASA/GODDARD SPACE FLIGHT CENTER
IMAGE:
THIS INFRARED IMAGE FROM NASA’S JAMES WEBB SPACE TELESCOPE (ALSO CALLED WEBB OR JWST) WAS TAKEN BY THE NIRCAM (NEAR-INFRARED CAMERA) FOR THE JWST ADVANCED DEEP EXTRAGALACTIC SURVEY, OR JADES, PROGRAM. THE NIRCAM DATA WAS USED TO DETERMINE WHICH GALAXIES TO STUDY FURTHER WITH SPECTROSCOPIC OBSERVATIONS. ONE SUCH GALAXY, JADES-GS-Z14-0 (SHOWN IN THE PULLOUT), WAS DETERMINED TO BE AT A REDSHIFT OF 14.32 (+0.08/-0.20), MAKING IT THE CURRENT RECORD-HOLDER FOR THE MOST DISTANT KNOWN GALAXY. THIS CORRESPONDS TO A TIME LESS THAN 300 MILLION YEARS AFTER THE BIG BANG.
IN THE BACKGROUND IMAGE, BLUE REPRESENTS LIGHT AT 0.9, 1.15, AND 1.5 MICRONS (FILTERS F090W + F115W + F150W), GREEN IS 2.0 AND 2.77 MICRONS (F200W + F277W), AND RED IS 3.56, 4.1, AND 4.44 MICRONS (F356W + F410M + F444W). THE PULLOUT IMAGE SHOWS LIGHT AT 0.9 AND 1.15 MICRONS (F090W + F115W) AS BLUE, 1.5 AND 2.0 MICRONS (F150W + F200W) AS GREEN, AND 2.77 MICRONS (F277W) AS RED.
CREDIT: CREDIT: NASA, ESA, CSA, STSCI, BRANT ROBERTSON (UC SANTA CRUZ), BEN JOHNSON (CFA), SANDRO TACCHELLA (CAMBRIDGE), PHILL CARGILE (CFA)
Over the last two years, scientists have used NASA’s James Webb Space Telescope (also called Webb or JWST) to explore what astronomers refer to as Cosmic Dawn – the period in the first few hundred million years after the big bang where the first galaxies were born. These galaxies provide vital insight into the ways in which the gas, stars, and black holes were changing when the universe was very young. In October 2023 and January 2024, an international team of astronomers used Webb to observe galaxies as part of the JWST Advanced Deep Extragalactic Survey (JADES) program. Using Webb’s NIRSpec (Near-Infrared Spectrograph), they obtained a spectrum of a record-breaking galaxy observed only two hundred and ninety million years after the big bang. This corresponds to a redshift of about 14, which is a measure of how much a galaxy’s light is stretched by the expansion of the universe. We invited Stefano Carniani from Scuola Normale Superiore in Pisa, Italy, and Kevin Hainline from the University of Arizona in Tucson, Arizona, to tell us more about how this source was found and what its unique properties tell us about galaxy formation.
“The instruments on Webb were designed to find and understand the earliest galaxies, and in the first year of observations as part of the JWST Advanced Deep Extragalactic Survey (JADES), we found many hundreds of candidate galaxies from the first 650 million years after the big bang. In early 2023, we discovered a galaxy in our data that had strong evidence of being above a redshift of 14, which was very exciting, but there were some properties of the source that made us wary. The source was surprisingly bright, which we wouldn’t expect for such a distant galaxy, and it was very close to another galaxy such that the two appeared to be part of one larger object. When we observed the source again in October 2023 as part of the JADES Origins Field, new imaging data obtained with Webb’s narrower NIRCam (Near-Infrared Camera) filters pointed even more toward the high-redshift hypothesis. We knew we needed a spectrum, as whatever we would learn would be of immense scientific importance, either as a new milestone in Webb’s investigation of the early universe or as a confounding oddball of a middle-aged galaxy.
“In January 2024, NIRSpec observed this galaxy, JADES-GS-z14-0, for almost ten hours, and when the spectrum was first processed, there was unambiguous evidence that the galaxy was indeed at a redshift of 14.32, shattering the previous most-distant galaxy record (z = 13.2 of JADES-GS-z13-0). Seeing this spectrum was incredibly exciting for the whole team, given the mystery surrounding the source. This discovery was not just a new distance record for our team; the most important aspect of JADES-GS-z14-0 was that at this distance, we know that this galaxy must be intrinsically very luminous. From the images, the source is found to be over 1,600-light years across, proving that the light we see is coming mostly from young stars and not from emission near a growing supermassive black hole. This much starlight implies that the galaxy is several hundreds of millions of times the mass of the Sun! This raises the question: How can nature make such a bright, massive, and large galaxy in less than 300 million years?
“The data reveal other important aspects of this astonishing galaxy. We see that the color of the galaxy is not as blue as it could be, indicating that some of the light is reddened by dust, even at these very early times. JADES researcher Jake Helton of Steward Observatory and the University of Arizona also identified that JADES-GS-z14-0 was detected at longer wavelengths with Webb’s MIRI (Mid-Infrared Instrument), a remarkable achievement considering its distance. The MIRI observation covers wavelengths of light that were emitted in the visible-light range, which are redshifted out of reach for Webb’s near-infrared instruments. Jake’s analysis indicates that the brightness of the source implied by the MIRI observation is above what would be extrapolated from the measurements by the other Webb instruments, indicating the presence of strong ionized gas emission in the galaxy in the form of bright emission lines from hydrogen and oxygen. The presence of oxygen so early in the life of this galaxy is a surprise and suggests that multiple generations of very massive stars had already lived their lives before we observed the galaxy.
“All of these observations, together, tell us that JADES-GS-z14-0 is not like the types of galaxies that have been predicted by theoretical models and computer simulations to exist in the very early universe. Given the observed brightness of the source, we can forecast how it might grow over cosmic time, and so far we have not found any suitable analogs from the hundreds of other galaxies we’ve observed at high redshift in our survey. Given the relatively small region of the sky that we searched to find JADES-GS-z14-0, its discovery has profound implications for the predicted number of bright galaxies we see in the early universe, as discussed in another concurrent JADES study (Robertson et al., recently accepted). It is likely that astronomers will find many such luminous galaxies, possibly at even earlier times, over the next decade with Webb. We’re thrilled to see the extraordinary diversity of galaxies that existed at Cosmic Dawn!”
These spectroscopic observations were taken as part of Guaranteed Time Observations (GTO) program 1287, and the MIRI ones as part of GTO program 1180.
Medium and mighty: Intermediate-mass black holes can survive in globular clusters
First-ever simulations of individual stars in a forming globular cluster demonstrate potential mechanisms of intermediate-mass black hole formation
SCHOOL OF SCIENCE, THE UNIVERSITY OF TOKYO
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STAR CLUSTER FORMING IN A GIANT MOLECULAR CLOUD REPRODUCED BY THE SIMULATION. THIS IMAGE IS BASED ON THE SIMULATION. BLUE DOTS REPRESENT INDIVIDUAL STARS. DARK AND BRIGHT COLOR INDICATE THE GAS TEMPERATURES (COLD AND HOT). VISUALIZED BY TAKAAKI TAKEDA (VASA ENTERTAINMENT INC.)
view moreCREDIT: MICHIKO FUJII AND TAKAAKI TAKEDA. 2024
Joint research led by Michiko Fujii of the University of Tokyo demonstrated a possible formation mechanism of intermediate-mass black holes in globular clusters, star clusters that could contain tens of thousands or even millions of tightly packed stars. The first ever star-by-star massive cluster-formation simulations revealed that sufficiently dense molecular clouds, the “birthing nests” of star clusters, can give birth to very massive stars that evolve into intermediate-mass black holes. The findings were published in the journal Science.
“Previous observations have suggested that some massive star clusters (globular clusters) host an intermediate-mass black hole (IMBH),” Fujii explains the motivation for the research project. “An IMBH is a black hole with a mass of 100-10000 solar masses. So far, there has been no strong theoretical evidence to show the existence of IMBH with 1000-10 000 solar masses compared to less massive (stellar mass) and more massive (supermassive) ones.”
Birthing nests might conjure up images of warmth and tranquility. Not so with stars. Globular star clusters form in turmoil. The differences in density first cause stars to collide and merge. As the stars continue to merge and grow, the gravitational forces grow with them. The repeated stellar collisions in the dense, central region of globular clusters are called runaway collisions. They can lead to the birth of very massive stars with more than 1000 solar masses. These stars could potentially evolve into IMBHs. However, previous simulations of already-formed clusters suggested that stellar winds blow away most of their mass, leaving them too small. To investigate whether IMBHs could “survive,” researchers needed to simulate a cluster while it was still forming.
“Star cluster formation simulations were challenging because of the simulation cost,” Fujii says. “We, for the first time, successfully performed numerical simulations of globular cluster formation, modeling individual stars. By resolving individual stars with a realistic mass for each, we could reconstruct the collisions of stars in a tightly packed environment. For these simulations, we have developed a novel simulation code, in which we could integrate millions of stars with high accuracy.”
In the simulation, the runaway collisions indeed led to the formation of very massive stars that evolved into intermediate-mass black holes. The researchers also found that the mass ratio between the cluster and the IMBH matched that of the observations that originally motivated the project.
“Our final goal is to simulate entire galaxies by resolving individual stars,” Fujii points to future research. “It is still difficult to simulate Milky Way-size galaxies by resolving individual stars using currently available supercomputers. However, it would be possible to simulate smaller galaxies such as dwarf galaxies. We also want to target the first clusters, star clusters formed in the early universe. First clusters are also places where IMBHs can be born.”
Omega Centauri, a globular cluster in the Milky-way galaxy. This globular cluster may host an intermediate-mass black hole.
CREDIT
ESO
JOURNAL
Science
METHOD OF RESEARCH
Computational simulation/modeling
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Simulations predict intermediate-mass black hole formation in globular clusters
ARTICLE PUBLICATION DATE
30-May-2024
News from "El Gordo": Study suggests dark matter may have collisional properties after all
Using simulations, the research provided a possible explanation for the behaviour observed in this gigantic merging cluster of galaxies
SCUOLA INTERNAZIONALE SUPERIORE DI STUDI AVANZATI
Contrary to what is established by the standard model, dark matter may indeed be self-interacting. This was the conclusion of a new piece of research published in "Astronomy & Astrophysics" (A&A) and conducted by Riccardo Valdarnini of SISSA's Astrophysics and Cosmology group. Using numerical simulations, the study analysed what happens inside "El Gordo" (literally "The Fat One" in Spanish), a giant cluster merger seven billion light years away from us. The calculations indicated that in this cluster the observed physical separation between the points of maximum density of Dark Matter and those of the other mass components can be explained using the so-called SIDM (Self-Interacting dark matter) model, as opposed to the standard one. This research makes an important contribution in favour of the SIDM model, according to which dark matter particles exchange energy through collisions, with interesting astrophysical repercussions.
"El Gordo": a gigantic cosmic structure for the study of dark matter
"According to the currently-accepted standard cosmological model, the present baryonic matter density of the Universe can account for only 10% of its total matter content. The remaining 90% is in the form of Dark Matter," explains Riccardo Valdarnini, author of the research. "It is generally thought that this matter is non baryonic and made of cold collisionless particles, which respond only to gravity. Hence the name "Cold Dark Matter" (CDM). However, there are still a number of observations which have not yet been explained using the standard model” says the researcher. "To answer these questions, several authors suggest an alternative model, called SIDM." Proving the collisional properties of dark matter and, more generally, alternative theories to the standard cosmological model one is very complicated: "There are, however, unique laboratories that can prove very useful for this purpose, many light years away from us. These are the massive galaxy clusters, gigantic cosmic structures that, upon collision, determine the most energetic events since the Big Bang. With a mass of about 1015 solar masses, El Gordo is one of the largest galaxy clusters we know. Due to its peculiarities, El Gordo has been the subject of numerous studies, both theoretical and observational".
Dark matter could be collisional
According to the standard paradigm, during a cluster merger the behavior of the collisional gas mass component will differ from that of the other two components - galaxies and dark matter. In this scenario, the gas will dissipate part of its initial energy. "This is why, after the collision, the peak of gas mass density will lag behind those of dark matter and galaxies," explains Valdarnini. With the SIDM model, however, a peculiar phenomenon should be observed, namely the physical separation of dark matter centroids - its maximum density points - from those of other mass components with peculiarities that represent a true “Signature of SIDM models”. According to observations, this is exactly what happens inside "El Gordo".
Observing El Gordo
"Let us start with observations:" explains Valdarnini. El Gordo consists of two massive subclusters, respectively denominated northwestern (NW) and southeastern (SE). The X-ray image of the "El Gordo" cluster shows a single X-ray emission peak in the SE subcluster and two faint tails elongated beyond the X-ray peak. A noteworthy feature is the peak location of the different mass components. At variance with what can be seen in the Bullet Cluster, another important example of a colliding cluster, the X-ray peak precedes the SE dark matter peak. Moreover, the Brightest Cluster Galaxy (BCG) is not only trailing the X-ray peak, but it also appears to be spatially offset from the SE mass centroid. Another notable aspect can be seen in the NW cluster, where the galaxy number density peak is spatially offset from the corresponding mass peak."
Research findings suggest Collisional Dark Matter as an explanation for the phenomena observed in "El Gordo"
In order to explain his findings and validate the SIDM models, in the study published in "Astronomy & Astrophysics", Valdarnini used a large set of so-called N-body/hydrodynamical simulations. Thus, he carried out a systematic study aimed at reproducing the observational features of "El Gordo". "The most significant result of this simulation study is that the relative separations observed between the different mass centroids of the "El Gordo" cluster are naturally explained if the dark matter is self-interacting," states Valdarnini. "For this reason, these findings provide an unambiguous signature of a dark matter behaviour that exhibits collisional properties in a very energetic high-redshift cluster collision. There are, however, inconsistencies, as the SIDM cross section values obtained from these simulations are higher than present upper limits, which are of order unity at cluster scales. This suggests that present SIDM models should be considered as only a low order approximation, and that the underlying physical processes that describe the interaction of dark matter in major cluster mergers are more complex than can be adequately represented by the commonly-assumed approach based on the scattering of dark matter particles. The study makes a compelling case for the possibility of self-interacting dark matter between colliding clusters as an alternative to the standard collisionless dark matter paradigm".
JOURNAL
Astronomy and Astrophysics
METHOD OF RESEARCH
Computational simulation/modeling
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
An N-body/hydrodynamical simulation study of the merging cluster El Gordo: A compelling case for self-interacting dark matter?
Martian meteorites deliver a trove of information on Red Planet’s structure
The nature of Mars’ mantle and crust is revealed in its volcanic rocks
IMAGE:
NAKHLA METEORITE. IMAGE MEASURES FOUR CENTIMETERS ACROSS.
view moreCREDIT: SCRIPPS INSTITUTION OF OCEANOGRAPHY AT UC SAN DIEGO
Mars has a distinct structure in its mantle and crust with discernible reservoirs, and this is known thanks to meteorites that scientists at Scripps Institution of Oceanography at UC San Diego and colleagues have analyzed on Earth.
Meteorites that formed roughly 1.3 billion years ago and then ejected from Mars have been collected by scientists from sites in Antarctica and Africa in recent decades. Scripps Oceanography geologist James Day and his colleagues report May 31 in the journal Science Advances on analyses of the chemical compositions of these samples from the Red Planet.
These results are important for understanding not only how Mars formed and evolved, but also for providing precise data that can inform recent NASA missions like Insight and Perseverance and the Mars Sample Return, said study lead Day.
“Martian meteorites are the only physical materials we have available from Mars,” said Day. “They enable us to make precise and accurate measurements and then quantify processes that occurred within Mars and close to the martian surface. They provide direct information on Mars’ composition that can ground truth mission science, like the ongoing Perseverance rover operations taking place there.”
Day’s team assembled its account of Mars’ formation using meteorite samples that all came from the same volcano, known as nakhlites and chassignites. Some 11 million years ago, a large meteor impact on Mars sheared away parts of the planet and sent the rocks hurtling into space. Some of those landed on Earth in the form of meteorites, with the first of these being discovered in 1815 in Chassigny, France and then in 1905 in Nakhla, Egypt.
Since then, more such meteorites have been discovered in locations including Mauritania and Antarctica. Scientists are able to identify Mars as their place of origin because these meteorites are relatively young, so come from a recently active planet, have distinct compositions of the abundant element oxygen compared to Earth, and retain the composition of Mars’ atmosphere measured on the surface by the Viking landers in the 1970s.
The team analyzed the two keystone nakhlite and chassignite meteorite types. Nakhlites are basaltic, similar to lavas erupting in Iceland and Hawaii today, but are rich in a mineral called clinopyroxene. Chassignites are almost exclusively made of the mineral olivine. On Earth, basalts are a main component of the planet’s crust, especially under the oceans, while olivines are abundant in its mantle.
The same is true on Mars. The team showed that these rocks are related to each other through a process known as fractional crystallization within the volcano in which they were formed. Using the composition of these rocks, they also show that some of the then-molten nakhlites incorporated portions of crust close to the surface that also interacted with Mars’ atmosphere.
“By determining that nakhlites and chassignites are from the same volcanic system, and that they interacted with martian crust that was altered by atmospheric interactions, we can identify a new rock type on Mars,” said Day. “With the existing collection of martian meteorites, all of which are volcanic in origin, we are able to better understand the internal structure of Mars.”
The team was able to do this because of the distinctive chemical characteristics of nakhlites and chassignites, as well as the characteristic compositions of other martian meteorites. These reveal an atmospherically altered upper crust to Mars, a complex deeper crust and a mantle where plumes from deep within Mars have penetrated to the base of the crust, while the interior of Mars’, formed early in its evolution have also melted to produce distinct types of volcanoes.
“What’s remarkable is that Mars’ volcanism has incredible similarities, but also differences, to Earth,” said Day. “On the one hand, nakhlites and chassignites formed in similar ways to recent volcanism in places like Oahu in Hawaii. There, newly formed volcanoes press down on the mantle generating tectonic forces that produce further volcanism.”
“On the other hand, the reservoirs in Mars are extremely ancient, separating from one another shortly after the Red planet formed. On Earth, plate tectonics has helped to remix reservoirs back together over time. In this sense, Mars provides an important link between what the early Earth may have looked like from how it looks today.”
Besides Day, Marine Paquet of Scripps Oceanography and colleagues from the University of Nevada Las Vegas and the French National Centre for Scientific Research contributed to the study. The NASA Solar Systems Workings and Emerging Worlds program funded the research.
The Chassigny meteorite in cross-polarized light. This meteorite is dominated by the mineral olivine. Grains are roughly 0.5 millimeters across.
CREDIT
Scripps Institution of Oceanography at UC San Diego
JOURNAL
Science Advances
METHOD OF RESEARCH
Meta-analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
A heterogenous mantle and crustal structure formed during the early differentiation of Mars
ARTICLE PUBLICATION DATE
31-May-2024
Astronomers discover potentially habitable planet
An Earth-like planet with the potential to support human life has been discovered just 40 light-years away.
Named Gliese 12 b, the planet orbits its host star every 12.8 days, and is comparable in size to Venus – so slightly smaller than Earth.
It has an estimated surface temperature of 42C, which is lower than most of the 5,000-odd exoplanets (planets outside of the solar system) confirmed so far.
Astronomers suggest Gliese 12 b is one of the few known planets where humans could theoretically survive, but they are still unsure what its atmosphere looks like, if it has one at all.
Getting an answer to what the atmosphere looks like is vital because it would reveal if the planet can maintain temperatures suitable for liquid water – and possibly life – to exist on its surface.
Masayuki Kuzuhara, a project assistant professor at the Astrobiology Centre in Tokyo, who co-led one research team with Akihiko Fukui, said: “We’ve found the nearest, transiting, temperate, Earth-size world located to date.
“Although we don’t yet know whether it possesses an atmosphere, we’ve been thinking of it as an exo-Venus, with similar size and energy received from its star as our planetary neighbour in the solar system.”
The University of Warwick’s Professor Thomas Wilson, a physicist, was involved in the discovery, using data from Nasa’s satellites to confirm the planet’s existence and characteristics such as its size, temperature, and distance away from Earth.
He said: “This is a really exciting discovery and will help our research into planets similar to Earth.
“Sadly, this planet is a little far away for us to experience it more closely. The light we are seeing now is from 40 years ago – that’s how long it has taken to reach us here on Earth.
The two teams, including one in Tokyo, used observations by Nasa’s TESS (Transiting Exoplanet Survey Satellite) to help make their discovery.
The planet’s equivalent of the Sun, called Gliese 12, is a cool red dwarf located in constellation Pisces.
The star is only about 27% of the Sun’s size, with about 60% of the Sun’s surface temperature.
Gliese 12 b is not the first Earth-like exoplanet to have been discovered, but Nasa said there are only a handful of worlds like it that warrant a closer look.
It has been billed as a potential target for further investigation by the US space agency’s James Webb Space Telescope.
The newly discovered planet could also be significant because it may help reveal whether the majority of stars in the Milky Way galaxy are capable of hosting temperate planets that have atmospheres and are therefore habitable.
The distance separating the planet and its star is just 7% of the distance between Earth and the Sun, and the planet receives 1.6 times more energy from its star than Earth does from the Sun.
One important factor in retaining an atmosphere is the storminess of its star.
Red dwarfs tend to be magnetically active, resulting in frequent, powerful X-ray flares.
However, analyses by scientists conclude that Gliese 12 shows no signs of extreme behaviour.
“Gliese 12 b represents one of the best targets to study whether Earth-size planets orbiting cool stars can retain their atmospheres, a crucial step to advance our understanding of habitability on planets across our galaxy,” said Shishir Dholakia, a doctoral student at the Centre for Astrophysics at the University of Southern Queensland in Australia.
He co-led a research team with Larissa Palethorpe, a doctoral student at the University of Edinburgh and University College London (UCL).
Co-author Dr Vincent Van Eylen, also from UCL, said: “GJ12b is an incredibly exciting planet because its size is identical to that of Earth.
“Even though GJ12b is about 15 times closer to its star than Earth is to our Sun, because it orbits such a small star the temperature on the planet may be quite similar to that on Earth.
“That doesn’t necessarily guarantee that the planet is habitable, but it does make it a great place to start looking.
“Fortunately it’s also a very nearby star, so we will learn much more about the planet and its atmosphere with telescopes like JWST in the next years.”
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