Hubble follows shadow play around planet-forming disk
IMAGE: THIS ARTIST'S CONCEPT IS BASED ON HUBBLE SPACE TELESCOPE IMAGES OF GAS-AND-DUST DISKS AROUND THE YOUNG STAR TW HYDRAE. HUBBLE SPACE TELESCOPE PHOTOS SHOW SHADOWS SWEEPING ACROSS THE DISKS ENCIRCLING THE SYSTEM. THE INTERPRETATION IS THESE SHADOWS ARE FROM SLIGHTLY INCLINED INNER DISKS THAT BLOCK STARLIGHT FROM REACHING THE OUTER DISK, AND THEREFORE ARE CASTING A SHADOW. THE DISKS ARE SLIGHTLY INCLINED TO EACH OTHER DUE TO THE GRAVITATIONAL PULL OF UNSEEN PLANETS WARPING THE DISK STRUCTURE. view more
CREDIT: NASA, AURA/STSCI FOR ESA, LEAH HUSTAK (STSCI)
The young star TW Hydrae is playing "shadow puppets" with scientists observing it with NASA's Hubble Space Telescope.
In 2017, astronomers reported discovering a shadow sweeping across the face of a vast pancake-shaped gas-and-dust disk surrounding the red dwarf star. The shadow isn't from a planet, but from an inner disk slightly inclined relative to the much larger outer disk – causing it to cast a shadow. One explanation is that an unseen planet's gravity is pulling dust and gas into the planet's inclined orbit.
Now, a second shadow – playing a game of peek-a-boo – has emerged in just a few years between observations stored in Hubble's MAST archive. This could be from yet another disk nestled inside the system. The two disks are likely evidence of a pair of planets under construction.
TW Hydrae is less than 10 million years old and resides about 200 light-years away. In its infancy, our solar system may have resembled the TW Hydrae system, some 4.6 billion years ago. Because the TW Hydrae system is tilted nearly face-on to our view from Earth, it is an optimum target for getting a bull's-eye-view of a planetary construction yard.
The second shadow was discovered in observations obtained on June 6, 2021, as part of a multi-year program designed to track the shadows in circumstellar disks. John Debes of AURA/STScI for the European Space Agency at the Space Telescope Science Institute in Baltimore, Maryland, compared the TW Hydrae disk to Hubble observations made several years ago.
"We found out that the shadow had done something completely different," said Debes, who is principal investigator and lead author of the study published in The Astrophysical Journal. "When I first looked at the data, I thought something had gone wrong with the observation because it wasn't what I was expecting. I was flummoxed at first, and all my collaborators were like: what is going on? We really had to scratch our heads and it took us a while to actually figure out an explanation."
The best solution the team came up with is that there are two misaligned disks casting shadows. They were so close to each other in the earlier observation they were missed. Over time they've now separated and split into two shadows. "We've never really seen this before on a protoplanetary disk. It makes the system much more complex than we originally thought," he said.
The simplest explanation is that the misaligned disks are likely caused by the gravitational pull of two planets in slightly different orbital planes. Hubble is piecing together a holistic view of the architecture of the system.
The disks may be proxies for planets that are lapping each other as they whirl around the star. It's sort of like spinning two vinyl phonograph records at slightly different speeds. Sometimes labels will match up but then one gets ahead of the other.
"It does suggest that the two planets have to be fairly close to each other. If one was moving much faster than the other, this would have been noticed in earlier observations. It's like two race cars that are close to each other, but one slowly overtakes and laps the other," said Debes.
The suspected planets are located in a region roughly the distance of Jupiter from our Sun. And, the shadows complete one rotation around the star about every 15 years – the orbital period that would be expected at that distance from the star.
Also, these two inner disks are inclined about five to seven degrees relative to the plane of the outer disk. This is comparable to the range of orbital inclinations inside our solar system. "This is right in line with typical solar system style architecture," said Debes.
The outer disk that the shadows are falling on may extend as far as several times the radius of our solar system's Kuiper belt. This larger disk has a curious gap at twice Pluto's average distance from the Sun. This might be evidence for a third planet in the system.
Any inner planets would be difficult to detect because their light would be lost in the glare of the star. Also, dust in the system would dim their reflected light. ESA's Gaia space observatory may be able to measure a wobble in the star if Jupiter-mass planets are tugging on it, but this would take years given the long orbital periods.
The TW Hydrae data are from Hubble's Space Telescope Imaging Spectrograph. The James Webb Space Telescope's infrared vision may also be able to show the shadows in more detail.
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 conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.
Comparison images from the Hubble Space Telescope, taken several years apart, have uncovered two eerie shadows moving counterclockwise across a gas-and-dust disk encircling the young star TW Hydrae. The disks are tilted face-on to Earth and so give astronomers a bird's-eye view of what's happening around the star. The left image, taken in 2016, shows just one shadow [A] at the 11:00 o'clock position. This shadow is cast by an inner disk that is slightly inclined to the outer disk and so blocks starlight. The picture on the left shows a second shadow that emerged from yet another nested disk [C] at the 7:00 o’clock position, as photographed in 2021. The original inner disk is marked [B] in this later view. The shadows rotate around the star at different rates like the hands on a clock. They are evidence for two unseen planets that have pulled dust into their orbits. This makes them slightly inclined to each other. This is a visible-light photo taken with the Space Telescope Imaging Spectrograph. Artificial color, to enhance details, has been added.
CREDIT
NASA, ESA, STScI, John Debes (AURA/STScI for ESA) IMAGE PROCESSING: Joseph DePasquale (STScI)
JOURNAL
The Astrophysical Journal
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
The Surprising Evolution of the Shadow on the TW Hya Disk
ARTICLE PUBLICATION DATE
4-May-2023
`Space waves' offer new clues to space weather, Embry-Riddle researchers report
IMAGE: WHEN SOLAR WIND HITS THE MAGNETOSPHERE, IT CREATES BREAKING WAVES KNOWN TO SCIENTISTS AS KELVIN-HELMHOLTZ WAVES. THIS WAVE ACTIVITY IS SEASONAL, RESEARCHERS FOUND; IT INCREASES AROUND THE SPRING AND FALL SEASONS (EQUINOXES) AND DECREASES AROUND SUMMER AND WINTER (SOLSTICES). view more
CREDIT: ILLUSTRATION: S. KAVOSI AND H. NYKYRI / EMBRY-RIDDLE AERONAUTICAL UNIVERSITY
More accurate space-weather predictions and safer satellite navigation through radiation belts could someday result from new insights into “space waves,” researchers at Embry-Riddle Aeronautical University reported.
The group’s latest research, published on May 4, 2023, by the journal Nature Communications, shows that seasonal and daily variations in the Earth’s magnetic tilt, toward or away from the Sun, can trigger changes in large-wavelength space waves.
These breaking waves, known as Kelvin-Helmholtz waves, occur at the boundary between the solar wind and the Earth’s magnetic shield. The waves happen much more frequently around the spring and fall seasons, researchers reported, while wave activity is poor around summer and winter.
As plasma or solar wind streams from the Sun at speeds up to 1 million miles per hour, it pushes energy, mass and momentum toward the planet’s magnetic shield. It also whips up space waves.
Fast-moving solar wind can’t pass directly through the Earth’s magnetic shield, so it thunders along the magnetosphere, propelling Kelvin-Helmholtz waves with massive peaks up to 15,000 kilometers (km) high and 40,000 km long.
Astronaut Safety and Satellite Communication
“Through these waves, solar wind plasma particles can propagate into the magnetosphere, leading to variations in radiation belt fluxes of energetic particles—regions of dangerous radiation—that may affect astronaut safety and satellite communications,” said Dr. Shiva Kavosi, a research associate at Embry-Riddle and first author of the “Nature Communications” paper. “On the ground, these events can impact power grids and Global Positioning Systems.”
Describing the properties of space waves and the mechanisms that cause them to intensify is key to understanding and forecasting space weather, Kavosi noted: “Space weather events represent an increasing threat, yet in many cases, we don’t understand exactly what controls it. Any progress we can make in understanding the mechanisms behind space weather disturbances will improve our ability to provide forecasts and warnings.”
In trying to understand the causes of seasonal and diurnal variations of geomagnetic activity, researchers in the field have set forth several different hypotheses. For example, the Russell-McPherron (R-M) effect, first described in 1973, explains why auroras are more frequent and brighter in the spring and fall, based on the interplay of the Earth’s dipole tilt and a small magnetic field near the Sun’s equator.
“We don’t have all the answers yet,” said Dr. Katariina Nykyri, professor of physics and associate director for the Center of Space and Atmospheric Research at Embry-Riddle, “but our paper shows that the R-M effect is not the only explanation for the seasonal variation of geomagnetic activities. Equinox-driven events, based on the Earth’s dipole tilt, and R-M effects could operate simultaneously.”
In the future, Nykyri added, constellations of spacecraft in the solar wind and magnetosphere could more fully explain the complicated, multi-scale physics of space weather phenomena. “Such a system would allow advanced warnings of space weather to inform the operators of rocket launches and electrical power grids,” she said.
The “Nature Communications” paper concludes that “KH waves activity exhibit seasonal and diurnal variations, indicating the critical role of dipole tilt in modulating KHI across the magnetopause as a function of time.”
The research article, “Seasonal and Diurnal Variations of Kelvin-Helmholtz Instability at Terrestrial Magnetopause,” was authored by Embry-Riddle researchers Nykyri and Kavosi; C.J. Farrugia and Jimmy Raedar of the University of New Hampshire, Institute for the Study of Earth, Oceans and Space; and J.R. Johnson of Andrews University. The DOI is 10.1038/s41467-023-37485-x. The public link is https://www.nature.com/articles/s41467-023-37485-x.
The work was supported by NASA grants (numbers 80NSSC18K0661, SA405826326 80NSSC18K1381, 80NSSC22K0304 and 80NSSC22K0515) as well as support from the Magnetospheric Multiscale mission (MMS) at the University of New Hampshire.
About Embry-Riddle Aeronautical University
Reporters worldwide contact Embry-Riddle Aeronautical University for content experts in all aspects of aviation, aviation business, aerospace, engineering and STEM-related fields. Our faculty experts specialize in unmanned and autonomous systems, security and intelligence, air traffic and airport management, astronomy, human factors psychology, meteorology, spaceflight operations, urban air mobility and much more. Visit the Embry-Riddle Newsroom for story ideas.
Embry-Riddle educates 32,750+ students at its residential campuses in Daytona Beach, Florida and Prescott, Arizona, at approximately 110 Worldwide Campus locations and through online degree programs. In 2023, U.S. News & World Report named Embry-Riddle Worldwide the nation’s No. 2 provider of online bachelor’s degree programs. The university has ranked either No. 1 or No. 2 in this category every year since 2016. Our residential campuses hold multiple Top 10 rankings. All of our campuses have been ranked Best for Veterans.
JOURNAL
Nature Communications
METHOD OF RESEARCH
Computational simulation/modeling
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Seasonal and Diurnal Variations of Kelvin-Helmholtz Instability at Terrestrial Magnetopause
ARTICLE PUBLICATION DATE
4-May-2023
Neutron star’s X-rays reveal ‘photon
metamorphosis’
ITHACA, N.Y. -- A “beautiful effect” predicted by quantum electrodynamics (QED) can explain the puzzling first observations of polarized X-rays emitted by a magnetar – a neutron star featuring a powerful magnetic field, according to a Cornell astrophysicist.
The extremely dense and hot remnant of a massive star, boasting a magnetic field 100 trillion times stronger than Earth’s, was expected to generate highly polarized X-rays, meaning that the radiation’s electromagnetic field did not vibrate randomly but had a preferred direction.
But scientists were surprised when NASA’s Imaging X-ray Polarimetry Explorer (IXPE) satellite last year detected that lower- and higher-energy X-rays were polarized differently, with electromagnetic fields oriented at right angles to each other.
The phenomenon can be naturally explained as a result of “photon metamorphosis” – a transformation of X-ray photons that has been theorized but never directly observed, said Dong Lai, Ph.D. ’94, the Benson Jay Simon ’59, MBA ’62, and Mary Ellen Simon, M.A. ’63, Professor of Astrophysics in the College of Arts and Sciences.
“In this observation of radiation from a faraway celestial object, we see a beautiful effect that is a manifestation of intricate, fundamental physics,” Lai said. “QED is one of the most successful physics theories, but it had not been tested in such strong magnetic field conditions.”
Lai is the author of “IXPE Detection of Polarized X-rays from Magnetars and Photon Mode Conversion at QED Vacuum Resonance,” published April 18 in Proceedings of the National Academy of Sciences.
The research builds on calculations Lai and Wynn Ho, Ph.D. ’03, published 20 years ago, incorporating observations NASA reported last November of the magnetar 4U 0142+61, located 13,000 light-years away in the Cassiopeia constellation.
Quantum electrodynamics, which describes microscopic interactions between electrons and photons, predicts that as X-ray photons exit the neutron star’s thin atmosphere of hot, magnetized gas, or plasma, they pass through a phase called vacuum resonance.
There, Lai said, photons, which have no charge, can temporarily convert into pairs of “virtual” electrons and positrons that are influenced by the magnetar’s super-strong magnetic field even in vacuum, a process called “vacuum birefringence.” Combined with a related process, plasma birefringence, conditions are created for the polarity of high-energy X-rays to swing 90 degrees relative to low-energy X-rays, according to Lai’s analysis.
“You can think about the polarization as two flavors of photons,” he said. “A photon suddenly converting from one flavor to another – you don’t usually see this kind of thing. But it’s a natural consequence of the physics if you apply the theory under these extreme conditions.”
The IXPE mission did not see the polarization swing in observations of another magnetar, called 1RXS J170849.0-400910, with an even stronger magnetic field. Lai said that’s consistent with his calculations, which suggest vacuum resonance and photon metamorphosis would occur very deep inside such a neutron star.
Lai said his interpretation of IXPE’s observations of the magnetar 4U 0142+61 helped constrain its magnetic field and rotation, and suggested that its atmosphere was likely composed of partially ionized heavy elements.
Ongoing study of X-rays from some of the universe’s most extreme objects, including neutron stars and black holes, he said, enables scientists to probe the behavior of matter in conditions that can’t be replicated in labs, and adds to understanding of the universe’s beauty and diversity.
“The observations by IXPE have opened a new window for studying the surface environment of neutron stars,” Lai said. “This will lead to new insights into these enigmatic objects.”
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JOURNAL
Proceedings of the National Academy of Sciences
DOI
UTEP awarded numerous grants to support NASA space research
Research opportunities include examining imitation planetary bedrock and preparing astronauts for Artemis lunar operations
Grant and Award AnnouncementIMAGE: RESEARCHERS AT THE UNIVERSITY OF TEXAS AT EL PASO WILL HELP BUILD A ROBOTIC DEVICE FOR WELDING IN SPACE, PREPARE ASTRONAUTS FOR A MISSION TO THE MOON AND MORE, THANKS TO A SLEW OF NEW GRANTS FROM NASA. view more
CREDIT: THE UNIVERSITY OF TEXAS AT EL PASO.
EL PASO, Texas (May 4, 2023) – Researchers at The University of Texas at El Paso will help build a robotic device for welding in space, prepare astronauts for a mission to the Moon and more, thanks to a slew of new grants from NASA.
The burst of grants awarded to faculty across various departments and colleges highlight UTEP’s strong partnership with NASA and the critical scientific and engineering contributions made by the University for space exploration.
“These joint initiatives between UTEP and NASA strengthen UTEP’s reputation as a premier research institution,” said Stephen Aley, Ph.D., associate vice president of research and special projects with the Office of Research and Sponsored Projects. “The work and research performed by our faculty will impact NASA’s future space exploration and beyond.”
The grants include:
Lunar Regolith Simulants Study
Professors Reza Ashtiani, Ph.D. and Darren Cone will perform research on the granular mechanics of lunar soils. Under this grant, UTEP will become the repository of lunar regolith simulants, materials developed in the lab to represent physical, chemical and mineralogical characteristics of planetary soils. The study aims to provide valuable insights into the complex challenges of constructing infrastructure on other planets.
Development of a Robotic System for In-Space Welding
Professors Angel Flores-Abad, Ph.D., Joel Quintana, Ph.D., and John Bird, Ph.D., will support the development of a digital and hardware robotic system for in-space welding by characterizing process motion and forces and generating real and synthetic performance data.
Artemis Lunar Operations Support
This grant will allow professor Jose Hurtado, Ph.D., to continue his long-time work of providing geology expertise to NASA, including mission simulations and intensive field training for NASA astronauts at locations on Earth that resemble the Moon.
Lunar Soil, Rock Simulant Analysis
Through this grant, UTEP professors Carlos Cabrera Martinez, Ph.D., and Cone, along with Alejandro Metta, Ph.D., manager of the X-Ray Core Facility within UTEP’s Department of Chemistry & Biochemistry, will study imitation planetary regolith, the layer of rock on top of bedrock. The research this team will conduct will help analyze important structures in imitation lunar dust, helping to identify lunar resources that could support future bases of people living on the Moon.
“It’s important to learn about what types of oxides, water and other types of resources may be available on the Moon,” said Carlos Cabrera Martinez, Ph.D., professor and chair of the department of Chemistry and Biochemistry at UTEP. “This can give you an idea of where you can get, for example, oxygen and other metals and water — and that’s important to know for people staying on the Moon for a long time.”
Cabrera is hopeful that all of these grants are paving the way for UTEP to continue providing expertise and assistance to NASA for lunar research and other expeditions.
About The University of Texas at El Paso
The University of Texas at El Paso is America’s leading Hispanic-serving university. Located at the westernmost tip of Texas, where three states and two countries converge along the Rio Grande, 84% of our 24,000 students are Hispanic, and half are the first in their families to go to college. UTEP offers 169 bachelor’s, master’s and doctoral degree programs at the only open-access, top-tier research university in America.
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