COSMOLOGY
VLBA produces first full 3-D view of binary star-planet system
Technique provides details otherwise unavailable
Peer-Reviewed PublicationIMAGE: FROM ABOVE A PLANET ABOUT TWICE THE SIZE OF JUPITER, THIS ARTIST'S CONCEPTION SHOWS THE STAR THAT PLANET IS ORBITING AND THAT STAR'S BINARY COMPANION IN THE DISTANCE. view more
CREDIT: SOPHIA DAGNELLO, NRAO/AUI/NSF.
By precisely tracing a small, almost imperceptible, wobble in a nearby star's motion through space, astronomers have discovered a Jupiter-like planet orbiting that star, which is one of a binary pair. Their work, using the National Science Foundation's Very Long Baseline Array (VLBA), produced the first-ever determination of the complete, 3-dimensional structure of the orbits of a binary pair of stars and a planet orbiting one of them. This achievement, the astronomers said, can provide valuable new insights on the process of planet formation.
Though more than 5,000 extrasolar planets have been discovered so far, only three have been discovered using the technique -- called astrometry -- that produced this discovery. However, the feat of determining the 3-D architecture of a binary-star system that includes a planet "cannot be achieved with other exoplanet discovery methods," said Salvador Curiel, of the National Autonomous University of Mexico (UNAM).
"Since most stars are in binary or multiple systems, being able to understand systems such as this one will help us understand planet formation in general," Curiel said.
The two stars, which together are called GJ 896AB, are about 20 light-years from Earth -- close neighbors by astronomical standards. They are red dwarf stars, the most common type in our Milky Way galaxy. The larger one, around which the planet orbits, has about 44 percent of the mass of our Sun, while the smaller is about 17 percent as massive as the Sun. They are separated by about the distance of Neptune from the Sun, and orbit each other once every 229 years.
For their study of GJ 896AB, the astronomers combined data from optical observations of the system made between 1941 and 2017 with data from VLBA observations between 2006 and 2011. They then made new VLBA observations in 2020. The continent-wide VLBA's supersharp resolution -- ability to see fine detail -- produced extremely precise measurements of the stars' positions over time. The astronomers performed extensive analysis of the data that revealed the stars' orbital motions as well as their common motion through space.
Detailed tracing of the larger star's motion showed a slight wobble that revealed the existence of the planet. The wobble is caused by the planet's gravitational effect on the star. The star and planet orbit a location between them that represents their common center of mass. When that location, called the barycenter, is sufficiently far from the star, the star's motion around it can be detectable.
The astronomers calculated that the planet has about twice the mass of Jupiter and orbits the star every 284 days. Its distance from the star is slightly less than Venus' distance from the Sun. The planet's orbit is inclined roughly 148 degrees from the orbits of the two stars.
"This means that the planet moves around the main star in the opposite direction to that of the secondary star around the main star," said Gisela Ortiz-León, of UNAM and the Max Planck Institute for Radioastronomy. "This is the first time that such dynamical structure has been observed in a planet associated with a compact binary system that presumably was formed in the same protoplanetary disk", she added.
"Additional detailed studies of this and similar systems can help us gain important insights into how planets are formed in binary systems. There are alternate theories for the formation mechanism, and more data can possibly indicate which is most likely," said Joel Sanchez-Bermudez, of UNAM. "In particular, current models indicate that such a large planet is very unlikely as a companion to such a small star, so maybe those models need to be adjusted," he added.
The astrometric technique will be a valuable tool for characterizing more planetary systems, the astronomers said. "We can do much more work like this with the planned Next Generation VLA (ngVLA)," said Amy Mioduszewski, of the National Radio Astronomy Observatory. "With it, we may be able to find planets as small as the Earth."
The astronomers are reporting their findings in the 1 September issue of the Astronomical Journal.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
JOURNAL
The Astronomical Journal
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
3D Orbital Architecture of a Dwarf Binary System and Its Planetary Companion
ARTICLE PUBLICATION DATE
1-Sep-2022
NASA’s Webb takes its first-ever direct image of distant world
Reports and ProceedingsIMAGE: THIS IMAGE SHOWS THE EXOPLANET HIP 65426 B IN DIFFERENT BANDS OF INFRARED LIGHT, AS SEEN FROM THE JAMES WEBB SPACE TELESCOPE: PURPLE SHOWS THE NIRCAM INSTRUMENT’S VIEW AT 3.00 MICROMETERS, BLUE SHOWS THE NIRCAM INSTRUMENT’S VIEW AT 4.44 MICROMETERS, YELLOW SHOWS THE MIRI INSTRUMENT’S VIEW AT 11.4 MICROMETERS, AND RED SHOWS THE MIRI INSTRUMENT’S VIEW AT 15.5 MICROMETERS. THESE IMAGES LOOK DIFFERENT BECAUSE OF THE WAYS THE DIFFERENT WEBB INSTRUMENTS CAPTURE LIGHT. A SET OF MASKS WITHIN EACH INSTRUMENT, CALLED A CORONAGRAPH, BLOCKS OUT THE HOST STAR’S LIGHT SO THAT THE PLANET CAN BE SEEN. THE SMALL WHITE STAR IN EACH IMAGE MARKS THE LOCATION OF THE HOST STAR HIP 65426, WHICH HAS BEEN SUBTRACTED USING THE CORONAGRAPHS AND IMAGE PROCESSING. THE BAR SHAPES IN THE NIRCAM IMAGES ARE ARTIFACTS OF THE TELESCOPE’S OPTICS, NOT OBJECTS IN THE SCENE. (UNLABELED VERSION.) view more
CREDIT: CREDIT: NASA/ESA/CSA, A CARTER (UCSC), THE ERS 1386 TEAM, AND A. PAGAN (STSCI).
NASA’s JWST takes its first-ever direct image of distant world
WASHINGTON – An astrophysicist at the U.S. Naval Research Laboratory (NRL) is part of NASA’s James Webb Space Telescope’s (JWST) Early Release Science Team for Direct Observations of Exoplanets that released the observations of a super-Jupiter exoplanet, HIP 65426 b, using JWST Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) Sept. 1.
Jordan Stone, Ph.D., an astrophysicist in NRL’s Remote Sensing Division said this early release of the exoplanet imagery was detected using seven of JWST’s observational filters, representing the first images of an exoplanet to be obtained by JWST, and the first ever direct detection of an exoplanet at wavelengths beyond 5 microns.
“One of the things we're most excited about is that we now have the ability to measure the brightness of planets at wavelengths longer than 5 microns,” Jordan Stone, Ph.D., an astrophysicist at the U.S. Naval Research Laboratory in Washington, D.C. said. “So we now have this, highly precise, machine that's giving us the ability to, to measure light from planet surfaces across a really broad wavelength range. And so this is really going to transform our understanding of giant planets.”
An exoplanet is any planet beyond our solar system. HIP 65426 b, is a relatively young exoplanet, about 14 million years old, and is located in the constellation Centaurus, about 349 light years from Earth.
The JWST NIRCam observes from 0.6 to 5 microns and offers imaging, coronagraphy, and grism slitless spectroscopy; MIRI is a camera and a spectrograph that observes mid to long infrared radiation from 5 microns to 28 microns. It also has coronagraphs, especially for observing exoplanets.
HIP 65426 b circles an A type star, which is about twice the size of the sun. The planet orbits its star at about 60 – 100 AU (7.4 – 9.3 billion miles) distance. That is roughly the double the distance Pluto is from the sun. The exoplanet is seven times the mass and about one and a half times the size of Jupiter.
JWST, launched on Christmas Day 2021, is an international collaboration between NASA, the European Space Agency, and the Canadian Space Agency, and the first large strategic mission of the NASA Astrophysics Division to launch since the 1990’s. The infrared observatory is orbiting the Sun about 1 million miles from Earth. Since coming on line, it has produced stunning images and a series of preliminary discoveries.
About the U.S. Naval Research Laboratory
NRL is a scientific and engineering command dedicated to research that drives innovative advances for the U.S. Navy and Marine Corps from the seafloor to space and in the information domain. NRL is located in Washington, D.C. with major field sites in Stennis Space Center, Mississippi; Key West, Florida; Monterey, California, and employs approximately 3,000 civilian scientists, engineers and support personnel.
For more information, contact NRL Corporate Communications at (202) 480-3746 or nrlpao@nrl.navy.mil.
Cornell astronomers show how terrain evolves on icy comets
ITHACA, N.Y. – With an eye toward a possible return mission years in the future, Cornell University astronomers have shown how smooth terrains – a good place to land a spacecraft and to scoop up samples – evolve on the icy world of comets.
By applying thermal models to data gathered by the Rosetta mission – which caught up to the barbell-shaped Comet 67P/Churyumov–Gerasimenko almost a decade ago – they show that the topography influences the comet’s surface activity across hundreds of meters.
“You can have a uniform surface composition on comets and still have hotspots of activity,” said lead author Abhinav S. Jindal, a graduate student in astronomy and member of the research group of Alexander Hayes, associate professor of astronomy. “The topography is driving the activity.”
Comets are icy bodies made of dust, rocks and gas left over from the solar system’s formation about 4.6 billion years ago, Jindal said. They form in the solar system’s outer fringes and have spent eternity cruising through the dark, cosmic freezer of space, far from the sun’s heat.
“Their chemistry has not changed much from when comets formed, making them ‘time capsules’ preserving primordial material from the birth of the solar system,” Jindal said, explaining that these bodies likely seeded early Earth with water and key building blocks of life.
“As some of these comets have been pulled into the inner solar system,” he said, “their surfaces undergo changes. Science is trying to understand the driving processes.”
As Comet 67P loops its way back toward the sun, the body speeds by it to a point called perihelion – its closest approach – and the comet warms up. The Rosetta mission followed the comet as it rounded the sun and studied its activity. The smooth terrains serve as locations where the most changes were observed, making them key to grasping the surface’s evolution.
Jindal and the researchers examined the evolution of 16 topographic depressions in the Imhotep region – the largest smooth terrain deposit on 67P – between June 5, 2015, when activity was first observed, and Dec. 6, 2015, when the final large-scale changes were observed.
The comet went through a process called sublimation – in which the icy parts turned gaseous in the sun’s heat. The comet’s smooth Imhotep region showed a complex pattern of simultaneous eroding scarps (the steep edges of arc-shaped depressions) and material deposition.
Jindal believes science will one day return to Comet 67P. “These comets are helping us to answer the question of where we come from,” he said.
The research was published in the Planetary Science Journal.
For more information, see this Cornell Chronicle story.
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JOURNAL
The Planetary Science Journal
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