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November’s Night Sky Notes: Spy the Seventh Planet, Uranus
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By NASA
Discovery Alert: Watch the Synchronized Dance of a 6-Planet System
The discovery: Six planets orbit their central star in a rhythmic beat, a rare case of an “in sync” gravitational lockstep that could offer deep insight into planet formation and evolution.
Key facts: A star smaller and cooler than our Sun hosts a truly strange family of planets: six “sub-Neptunes” – possibly smaller versions of our own Neptune – moving in a cyclic rhythm. This orbital waltz repeats itself so precisely it can be readily set to music.
This animation shows six “sub-Neptune” exoplanets in rhythmic orbits around their star – with a musical tone as each planet passes a line drawn through the system. The line is where the planets cross in front of (transit) their star from Earth’s perspective. In these rhythms, known as “resonance,” the innermost planet makes three orbits for every two of the next planet out. Among the outermost planets, a pattern of four orbits for every three of the next planet out is repeated twice. Animation credit: Dr. Hugh Osborn, University of Bern Details: While multi-planet systems are common in our galaxy, those in a tight gravitational formation known as “resonance” are observed by astronomers far less often. In this case, the planet closest to the star makes three orbits for every two of the next planet out – called a 3/2 resonance – a pattern that is repeated among the four closest planets.
Among the outermost planets, a pattern of four orbits for every three of the next planet out (a 4/3 resonance) is repeated twice. And these resonant orbits are rock-solid: The planets likely have been performing this same rhythmic dance since the system formed billions of years ago. Such reliable stability means this system has not suffered the shocks and shakeups scientists might typically expect in the early days of planet formation – smash-ups and collisions, mergers and breakups as planets jockey for position. And that, in turn, could say something important about how this system formed. Its rigid stability was locked in early; the planets’ 3/2 and 4/3 resonances are almost exactly as they were at the time of formation. More precise measurements of these planets’ masses and orbits will be needed to further sharpen the picture of how the system formed.
Fun facts: The discovery of this system is something of a detective story. The first hints of it came from NASA’s TESS (the Transiting Exoplanet Survey Satellite), which tracks the tiny eclipses – the “transits” – that planets make as they cross the faces of their stars. Combining the TESS measurements, made in separate observations two years apart, revealed an assortment of transits for the host star, called HD 110067. But it was difficult to distinguish how many planets they represented, or to pin down their orbits.
Eventually, astronomers singled out the two innermost planets, with orbital periods – “years” – of 9 days for the closest planet, 14 days for the next one out. A third planet, with a year about 20 days long, was identified with the help of data from CHEOPS, The European Space Agency’s CHaracterising ExOPlanets Satellite.
Then the scientists noticed something extraordinary. The three planets’ orbits matched what would be expected if they were locked in a 3/2 resonance. The next steps were all about math and gravity. The science team, led by Rafael Luque of the University of Chicago, worked through a well-known list of resonances that potentially could be found in such systems, trying to match them to the remaining transits that had been picked up by TESS. The only resonance chain that matched up suggested a fourth planet in the system, with an orbit about 31 days long. Two more transits had been seen, but their orbits remained unaccounted for because they were only single observations (more than one transit observation is needed to pin down a planet’s orbit). The scientists again ran through the list of possible orbits if there were two additional, outer planets that fit the expected chain of resonances across the whole system. The best fit they found: a fifth planet with a 41-day orbit, and a sixth just shy of 55.
At this point the science team almost hit a dead end. The slice of the TESS observations that had any chance of confirming the predicted orbits of the two outer planets had been set aside during processing. Excessive light scattered through the observation field by Earth and the Moon seemed to make them unusable. But not so fast. Scientist Joseph Twicken, of the SETI Institute and of the NASA Ames Research Center, took notice of the scattered light problem. He knew that scientist David Rapetti, also of Ames and of the Universities Space Research Association, happened to be working on a new computer code to recover transit data thought to be lost because of scattered light. At Twicken’s suggestion, Rapetti applied his new code to the TESS data. He found two transits for the outer planets – exactly where the science team led by Luque had predicted.
The discoverers: An international team of researchers led by Rafael Luque, of the University of Chicago, published a paper online on the discovery, “A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067,” in the journal Nature on Nov. 29.
Tracing a link between two neighbour planet at regular time interval along their orbits, creates a pattern unique to each couple. The six planets of the HD110067 system create together a mesmerising geometric pattern due to their resonance-chain. Credit: Thibaut Roger/NCCR PlanetS, CC BY-NC-SA 4.0 View the full article
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By NASA
3 min read
NASA’s Hubble Measures the Size of the Nearest Transiting Earth-Sized Planet
This is an artist’s concept of the nearby exoplanet LTT 1445Ac, which is the size of Earth. The planet orbits a red dwarf star. The star is in a triple system, with two closely orbiting red dwarfs seen at upper right. The black dot in front of the bright light-red sphere at image center is planet LTT 1445Ac transiting the face of the star. The planet has a surface temperature of roughly 500 degrees Fahrenheit. In the foreground at lower left is another planet in the system, LTT 1445Ab. The view is from 22 light-years away, looking back toward our Sun, which is the bright dot at lower right. Some of the background stars are part of the constellation Boötes. NASA, ESA, Leah Hustak (STScI) NASA’s Hubble Space Telescope has measured the size of the nearest Earth-sized exoplanet that passes across the face of a neighboring star. This alignment, called a transit, opens the door to follow-on studies to see what kind of atmosphere, if any, the rocky world might have.
The diminutive planet, LTT 1445Ac, was first discovered by NASA’s Transiting Exoplanet Survey Satellite (TESS) in 2022. But the geometry of the planet’s orbital plane relative to its star as seen from Earth was uncertain because TESS does not have the required optical resolution. This means the detection could have been a so-called grazing transit, where a planet only skims across a small portion of the parent star’s disk. This would yield an inaccurate lower limit of the planet’s diameter.
“There was a chance that this system has an unlucky geometry and if that’s the case, we wouldn’t measure the right size. But with Hubble’s capabilities we nailed its diameter,” said Emily Pass of the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts.
Hubble observations show that the planet makes a normal transit fully across the star’s disk, yielding a true size of only 1.07 times Earth’s diameter. This means the planet is a rocky world, like Earth, with approximately the same surface gravity. But at a surface temperature of roughly 500 degrees Fahrenheit, it is too hot for life as we know it.
The planet orbits the star LTT 1445A, which is part of a triple system of three red dwarf stars that is 22 light-years away in the constellation Eridanus. The star has two other reported planets that are larger than LTT 1445Ac. A tight pair of two other dwarf stars, LTT 1445B and C, lies about 3 billion miles away from LTT 1445A, also resolved by Hubble. The alignment of the three stars and the edge-on orbit of the BC pair suggests that everything in the system is co-planar, including the known planets.
“Transiting planets are exciting since we can characterize their atmospheres with spectroscopy, not only with Hubble but also with the James Webb Space Telescope. Our measurement is important because it tells us that this is likely a very nearby terrestrial planet. We are looking forward to follow-on observations that will allow us to better understand the diversity of planets around other stars,” said Pass.
This research has been accepted for publication in The Astronomical Journal.
The Hubble Space Telescope is a project of international cooperation between NASA and ESA. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.
Media Contacts:
Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov
Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
Science Contact:
Emily Pass
Center for Astrophysics | Harvard & Smithsonian, Cambridge, Massachusetts
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Last Updated Nov 16, 2023 Editor Andrea Gianopoulos Location Goddard Space Flight Center Related Terms
Astrophysics Astrophysics Division Earth-like Exoplanets Exoplanets Goddard Space Flight Center Hubble Space Telescope Missions Science & Research Science Mission Directorate Terrestrial Exoplanets TESS (Transiting Exoplanet Survey Satellite) The Universe Keep Exploring Discover More Topics From NASA
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By European Space Agency
The NASA/ESA Hubble Space Telescope has measured the size of the nearest Earth-sized exoplanet that passes across the face of a neighbouring star. This alignment, called a transit, opens the door to follow-on studies to see what kind of atmosphere, if any, the rocky world might have.
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By NASA
Scientists are following neon signs in a search for clues to one planetary system’s future and the past of another – our own solar system. Following up on a peculiar reading by NASA’s previous infrared flagship observatory, the now-retired Spitzer Space Telescope, the agency’s James Webb Space Telescope detected distinct traces of the element neon in the dusty disk surrounding the young Sun-like star SZ Chamaelontis (SZ Cha).
Image: SZ Chamaeleontis Protoplanetary Disk (Artist Concept )
In this artist concept, the young star SZ Chamaeleontis (SZ Cha) is surrounded by a disk of dust and gas with the potential to form a planetary system. Once our solar system looked something like this, before planets, moons, and asteroids formed. The raw ingredients, including those for life on Earth, were present in the Sun’s protoplanetary disk. SZ Cha emits radiation in multiple wavelengths which are evaporating the disk. Planets are in a race against time to form before the disk of material is evaporated completely. NASA’s James Webb Space Telescope observed typical conditions in the disk – it was being bombarded primarily by X-rays. However, when NASA’s Spitzer Space Telescope observed the disk in 2008, it saw a different scene, dominated by extreme ultraviolet (EUV) light, indicated by the presence of a specific type of neon in the disk. These differences are significant because planets would have more time to form from a disk dominated by EUV. Astronomers are investigating the cause of the difference between Webb and Spitzer’s readings, and think it may be due to the presence (or not) of a strong wind that, when active, absorbs EUV, leaving X-rays to hit the disk.NASA, ESA, CSA, Ralf Crawford (STScI) Differences in the neon readings between Spitzer and Webb point to a never-before-observed change in high-energy radiation that reaches the disk, which eventually causes it to evaporate, limiting the time planets have to form.
“How did we get here? It really goes back to that big question, and SZ Cha is the same type of young star, a T-Tauri star, as our Sun was 4.5 billion years ago at the dawn of the solar system,” said astronomer Catherine Espaillat of Boston University, in Massachusetts, who led both the 2008 Spitzer observations and the newly published Webb results. “The raw materials for Earth, and eventually life, were present in the disk of material that surrounded the Sun after it formed, and so studying these other young systems is as close as we can get to going back in time to see how our own story began.”
Scientists use neon as an indicator of how much, and what type, of radiation is hitting and eroding the disk around a star. When Spitzer observed SZ Cha in 2008, it saw an outlier, with neon readings unlike any other young T-Tauri disk. The difference was the detection of neon III, which is typically scarce in protoplanetary disks that are being pummeled by high-energy X-rays. This meant that the high-energy radiation in the SZ Cha disk was coming from ultraviolet (UV) light instead of X-rays. Besides being the lone oddball result in a sample of 50-60 young stellar disks, the UV vs. X-ray difference is significant for the lifetime of the disk and its potential planets.
Image: Neon Gas In Protoplanetary Disk
Contrasting data from NASA’s James Webb and Spitzer space telescopes show change in the disk surrounding the star SZ Chamaeleontis (SZ Cha) in just 15 years. In 2008, Spitzer’s detection of significant neon III made SZ Cha an outlier among similar young protoplanetary disks. However, when Webb followed up on SZ Cha in 2023, the ratio of neon II to III was within typical levels. All of this is significant because protoplanetary disks are the stuff of future planetary systems – and those potential planets are in a race against time. Astronomers use neon as an indicator of the dominant radiation hitting the disk and causing it to evaporate. When extreme ultraviolet light is dominant, there is more neon III. That is the unusual circumstance that Spitzer observed in 2008. Typically, a disk is dominated by X-ray radiation, which evaporates the disk more quickly, leaving planets less time to form. Researchers think the dramatic differences in neon detections are the result of a wind that, when present, absorbs ultraviolet light and leaves X-rays to pummel the disk. They will continue using Webb to find other examples of variability in disk conditions, working toward a better understanding of how planetary systems develop around Sun-like stars.NASA, ESA, CSA, Ralf Crawford (STScI) “Planets are essentially in a race against time to form up in the disk before it evaporates,” explained Thanawuth Thanathibodee of Boston University, another astronomer on the research team. “In computer models of developing systems, extreme ultraviolet radiation allows for 1 million more years of planet formation than if the evaporation is predominately caused by X-rays.”
So, SZ Cha was already quite the puzzle when Espaillat’s team returned to study it with Webb, only to find a new surprise: The unusual neon III signature had all but disappeared, indicating the typical dominance of X-ray radiation.
The research team thinks that the differences in neon signatures in the SZ Cha system are the result of a variable wind that, when present, absorbs UV light and leaves X-rays to pummel the disk. Winds are common in a system with a newly formed, energetic star, the team says, but it is possible to catch the system during a quiet, wind-free period, which is what Spitzer happened to do.
“Both the Spitzer and Webb data are excellent, so we knew this had to be something new we were observing in the SZ Cha system – a significant change in conditions in just 15 years,” added co-author Ardjan Sturm of Leiden University, Leiden, Netherlands.
Espaillat’s team is already planning more observations of SZ Cha with Webb, as well as other telescopes, to get to the bottom of its mysteries. “It will be important to study SZ Cha, and other young systems, in multiple wavelengths of light, like X-ray and visible light, to discover the true nature of this variability we’ve found,” said co-author Caeley Pittman of Boston University. “It’s possible that brief, quiet periods dominated by extreme UV radiation are common in many young planetary systems, but we just have not been able to catch them.”
“Once again, the universe is showing us that none of its methods are as simple as we might like to make them. We need to rethink, re-observe, and gather more information. We’ll be following the neon signs,” said Espaillat.
This research has been accepted for publication in Astrophysical Journal Letters.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
Media Contacts
Laura Betz – laura.e.betz@nasa.gov, Rob Gutro– rob.gutro@nasa.gov
NASA’s Goddard Space Flight Center, , Greenbelt, Md.
Leah Ramsay lramsay@stsci.edu , Christine Pulliam cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
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Download full resolution images for this article from the Space Telescope Science Institute.
Research results have been accepted for publication in Astropyisical Journal Letters.
Related Information
How do Planets Form? https://exoplanets.nasa.gov/faq/43/how-do-planets-form/
Planetary Systems – https://universe.nasa.gov/stars/planetary-systems/
Webb Mission – https://science.nasa.gov/mission/webb/
Webb News – https://science.nasa.gov/mission/webb/latestnews/
Webb Images – https://science.nasa.gov/mission/webb/multimedia/images/
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Last Updated Nov 15, 2023 Editor Steve Sabia Contact Related Terms
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