'Frame-dragging' with two spinning stars twisting space and time. Credit: Mark Myers, OzGrav ARC Centre of Excellence.
(Swinburne University of Technology) An international team of astrophysicists led by Australian Professor Matthew Bailes, from the ARC Centre of Excellence of Gravitational Wave Discovery (OzGrav), has shown exciting new evidence for 'frame-dragging'—how the spinning of a celestial body twists space and time—after tracking the orbit of an exotic stellar pair for almost two decades. The data, which is further evidence for Einstein's theory of General Relativity, is published today the journal Science.
The unusual star system known as PSR J1141-6545 was discovered around 10,000 light years away in the constellation of Musca aka The Fly in 2001. Since 2001 we have trekked to Parkes several times a year to map this system's orbit, which exhibits a multitude of Einsteinian gravitational effects.
At the heart is a fast-spinning white dwarf star — the remains of an old star about the size of Earth but 300,000 times its density.
Every five hours it is circled by a neutron star (pulsar) — the core of an exploded star no bigger than a city but about 100 billion times more dense than Earth.
The neutron star sends out regular pulses of high-energy particles like a lighthouse, which the astronomers used to track its orbit.
Mapping the evolution of orbits is not for the impatient, but our measurements are ridiculously precise. Although PSR J1141-6545 is several hundred quadrillion kilometres away (a quadrillion is a million billion), we know the pulsar rotates 2.5387230404 times per second, and that its orbit is tumbling in space.
This means the plane of its orbit is not fixed, but instead is slowly rotating.
Lead author Vivek Venkatraman Krishnan, Max Planck Institute for Radio Astronomy (MPIfR): "At first, the stellar pair appeared to exhibit many of the classic effects that Einstein's theory predicted. We then noticed a gradual change in the orientation of the plane of the orbit."
"Pulsars are cosmic clocks. Their high rotational stability means that any deviation to the expected arrival time of its pulses is probably due to the pulsar's motion or due to the electrons and magnetic fields that the pulses encounter. Pulsar timing is a powerful technique where we use atomic clocks at radio telescopes to estimate the arrival time of the pulses from the pulsar to very high precision. The motion of the pulsar in its orbit modulates the arrival time, thereby enabling its measurement." YouTube video: Dragging the Space-Time Continuum by OzGrav ARC Centre of Excellence:
Dr. Paulo Freire: "We postulated that this might be, at least in-part, due to the so-called 'frame-dragging' that all matter is subject to in the presence of a rotating body as predicted by the Austrian mathematicians Lense and Thirring in 1918."
Professor Thomas Tauris, Aarhus University: "In a stellar pair, the first star to collapse is often rapidly rotating due to subsequent mass transfer from its companion. Tauris's simulations helped quantify the magnitude of the white dwarf's spin. In this system the entire orbit is being dragged around by the white dwarf's spin, which is misaligned with the orbit."
(NASA) This month marks the third anniversary of the discovery of a remarkable system of seven planets known as TRAPPIST-1. These seven rocky, Earth-size worlds orbit an ultra-cool star 39 light-years from Earth. Three of those planets are in the habitable zone, meaning they are at the right orbital distance to be warm enough for liquid water to exist on their surfaces. After its 2021 launch, NASA’s James Webb Space Telescope will observe those worlds with the goal of making the first detailed near-infrared study of the atmosphere of a habitable-zone planet.
Video: An Introduction to the James Webb Space Telescope Mission:
To find signs of an atmosphere, astronomers will use a technique called transmission spectroscopy. They observe the host star while the planet is crossing the face of the star, known as a transit. The light of the star filters through the planet’s atmosphere, which absorbs some of the starlight and leaves telltale fingerprints in the star’s spectrum.
Finding an atmosphere around a rocky exoplanet — the word scientists use for planets beyond our solar system — won’t be easy. Their atmospheres are more compact than those of gas giants, while their smaller size means they intercept less of the star’s light. TRAPPIST-1 is one of the best available targets for Webb since the star itself is also quite small, meaning the planets’ size relative to the star is larger.
“The atmospheres are harder to detect but the reward is higher. It would be very exciting to make the first detection of an atmosphere on an Earth-sized planet,” said David Lafrenière of the University of Montreal, principal investigator on one of the teams examining TRAPPIST-1.
Red dwarf stars like TRAPPIST-1 tend to have violent outbursts that could make the TRAPPIST-1 planets inhospitable. But determining whether they have atmospheres, and if so, what they're made of, is the next step to finding out whether life as we know it could survive on these distant worlds.
The United States National Science Foundation (NSF) recently announced the award of a $12.7M grant to architect and design a next-generation Event Horizon Telescope (ngEHT). The principal investigator of this program is the EHT Founding Director, Sheperd Doeleman at the Center for Astrophysics | Harvard & Smithsonian. The ngEHT will sharpen our focus on black holes, and let researchers move from still-imagery to real-time videos of space-time at the event horizon.
The new award is aimed at solving the formidable technical and algorithmic challenges required to significantly expand the capability of the EHT. The first M87 black hole images were made using the technique of Very Long Baseline Interferometry (VLBI), in which an array of radio dishes around the world is combined to form an Earth-sized virtual telescope. By exploring new dish designs and locations, the ngEHT effort will plan the architecture for a new array with roughly double the number of sites worldwide.
Learn more about supermassive black holes:
YouTube video from How the Universe Works
The Event Horizon Telescope (EHT) which made the first direct image of a black hole, an image seen by billions of people around the world, is being upgraded after securing a $12.7M grant from the National Science Foundation. Coming soon: A greatly enhanced EHT (EHT-II), one with 7-8 additional telescopes placed around the world in locations designed to maximize imaging speed, dynamic range, and fidelity.
The much faster snapshot mode of this combination will allow rapid tracking of changes near the black hole event horizon, allowing for the first time ever the creation of movies directly showing the dynamics of extreme gravity environments. The greater imaging power will also address long-standing fundamental questions such as how matter is blasted away from a black hole in the form of relativistic jets. Broader impacts include a National Air and Space Museum exhibit, and training of students in instrumentation development.
Instead of relying on existing large facilities to form the Very Long Baseline Interferometry (VLBI) array, as the existing EHT has done, this design program will consider engineering and placement of small-diameter dishes that optimally fill out an Earth sized virtual telescope, tailored precisely for science objectives. By roughly doubling the number of dishes in the array through cost-effective use of small dishes, the EHT-II will be capable of making the first real-time movies of supermassive black holes. The Large Millimeter Telescope in Mexico, in collaboration with the University of Massachusetts Amherst, will serve as a testbed for advanced dual frequency receivers that will be developed as part of this design initiative.
This project is supported by the Foundation-wide Mid-scale Research Infrastructure program. The project will be managed by the Division of Astronomical Sciences within the Directorate for Mathematics and Physical Sciences.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
A blinding flash, a loud sonic boom, and shattered glass everywhere. This is what the people of Chelyabinsk, Russia, experienced five years ago when an asteroid exploded over their city the morning of Feb. 15, 2013.
The house-sized asteroid entered the atmosphere over Chelyabinsk at over eleven miles per second and blew apart 14 miles above the ground. The explosion released the energy equivalent of around 440,000 tons of TNT and generated a shock wave that blew out windows over 200 square miles and damaged some buildings. Over 1,600 people were injured in the blast, mostly due to broken glass.
“The Chelyabinsk event drew widespread attention to what more needs to be done to detect even larger asteroids before they strike our planet,” said NASA Planetary Defense Officer Lindley Johnson. “This was a cosmic wake-up call.”
Watch the event archive from Tuvix72:
YouTube video from Tuvix72
(NASA) Coincidentally, on the same day as the Chelyabinsk event, the United Nations Committee on Peaceful Uses of Outer Space Working Group on Near-Earth Objects was meeting in Vienna to finalize a recommendation to the U.N. on how to defend Earth from possible asteroid impacts. One result of this meeting was an endorsement by the U.N. General Assembly for the establishment of an International Asteroid Warning Network (IAWN) for worldwide collaboration on the detection and tracking of potential impact hazards and a Space Missions Planning Advisory Group (SMPAG) as a forum for the national space agencies to collaborate on plans for preventing any possible asteroid impact. In January 2014, the IAWN steering committee held its first meeting, and SMPAG met for the first time later that year.
At the same time, NASA’s Near Earth Object (NEO) Observations Program was growing in response to increased awareness of asteroid impact risks. The program focuses on finding asteroids 460 feet (140 meters) and larger that represent the most severe impact risks to Earth. The goal of the program is to find at least 90 percent of these asteroids early enough to allow deflection or other preparations for impact mitigation. By January 2018, discovery of near-Earth objects of all sizes had surpassed the 17,500 mark – an 84 percent increase since January 2013.
“Thanks to upgraded telescopes coming online in recent years, the rate of asteroid discovery has increased considerably,” said Kelly Fast, manager of NASA’s NEO Observations Program. “Over 8,000 of these larger asteroids are now being tracked. However, there are over twice that number still out there to be found.”
In January 2016, NASA established a Planetary Defense Coordination Office (PDCO), tasked with ensuring the early detection of potentially hazardous objects – asteroids and comets whose orbits can bring them within about 5 million miles (8 million kilometers) of Earth, and of a size large enough to reach Earth’s surface. PDCO is responsible for tracking and characterizing any potentially hazardous objects, issuing warnings about potential impacts, and providing timely and accurate communications about any actual impact threat while leading the coordination of U.S. Government planning for a response. The NEO Observations Program, a primary element of the PDCO, provides data from projects supported by the program to fulfill these responsibilities.
NASA works with the Federal Emergency Management Agency (FEMA) to lead U.S. Government planning for response to an actual impact threat. “We’ve conducted a series of ‘tabletop exercises’ with FEMA and other U.S. government agencies to simulate the events of an impending catastrophic asteroid impact with Earth to increase our emergency preparedness for it, and we’re planning more,” said Johnson. “We also work closely with our international colleagues in the International Asteroid Warning Network and the Space Missions Planning Advisory Group.”
Going beyond simulations, NASA also is undertaking the Double Asteroid Redirection Test (DART), a space-flight mission designed to demonstrate the kinetic-impact technique for nudging an asteroid off a predicted impact course with Earth. Launch is tentatively set for early to mid-2021. The Planetary Defense Coordination Office also is supporting development of concepts for a space-based asteroid search, detection and tracking mission.
In 2017, the first “test” of a global asteroid-impact early-warning system took place. The observation campaign was conceived and organized by NASA-funded asteroid observers, overseen by NASA, and included participants from the International Asteroid Warning Network and other international partners. The target of this observing campaign was an asteroid known as 2012 TC4. While scientists knew enough from the short period of discovery observations back in 2012 that it would safely pass Earth this last October, its precise path was uncertain, so it was an ideal target for a planetary defense exercise.
This early-warning-system test went well. Fast noted, “This was a successful real-life exercise for NASA and for the International Asteroid Warning Network, with smooth recovery of the object, precise prediction of the orbit and tracking of the asteroid as it passed about 27,000 miles from Earth’s surface on October 12th.”
While no known asteroid is predicted to be on an impact course with Earth for the next 100 years, the search goes on, and preparations for planetary defense continue. Said Johnson, “We must keep looking for what we know is still out there to be found.”
'Frame-dragging' with two spinning stars twisting space and time. Credit: Mark Myers, OzGrav ARC Centre of Excellence.
Image credit: NASA and JPL/Caltech
