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Watch a humanoid robot driving a car extremely slowly
Watch a humanoid robot driving a car extremely slowly
NASA’s asteroid sample mission gave scientists around the world the rare opportunity to study an artificial meteor
Investigating the Origins of the Crab Nebula With NASA’s Webb
New data revises our view of this unusual supernova explosion.
A team of scientists used NASA’s James Webb Space Telescope to parse the composition of the Crab Nebula, a supernova remnant located 6,500 light-years away in the constellation Taurus. With the telescope’s MIRI (Mid-Infrared Instrument) and NIRCam (Near-Infrared Camera), the team gathered data that is helping to clarify the Crab Nebula’s history.
The Crab Nebula is the result of a core-collapse supernova from the death of a massive star. The supernova explosion itself was seen on Earth in 1054 CE and was bright enough to view during the daytime. The much fainter remnant observed today is an expanding shell of gas and dust, and outflowing wind powered by a pulsar, a rapidly spinning and highly magnetized neutron star.
The Crab Nebula is also highly unusual. Its atypical composition and very low explosion energy previously have been explained by an electron-capture supernova — a rare type of explosion that arises from a star with a less-evolved core made of oxygen, neon, and magnesium, rather than a more typical iron core.
“Now the Webb data widen the possible interpretations,” said Tea Temim, lead author of the study at Princeton University in New Jersey. “The composition of the gas no longer requires an electron-capture explosion, but could also be explained by a weak iron core-collapse supernova.”
Image A: Crab Nebula (NIRCam and MIRI) This image by NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) shows different structural details of the Crab Nebula. The supernova remnant is comprised of several different components, including doubly ionized sulfur (represented in green), warm dust (magenta), and synchrotron emission (blue). Yellow-white mottled filaments within the Crab’s interior represent areas where dust and doubly ionized sulfur coincide. The observations were taken as part of General Observer program 1714. Studying the Present to Understand the PastPast research efforts have calculated the total kinetic energy of the explosion based on the quantity and velocities of the present-day ejecta. Astronomers deduced that the nature of the explosion was one of relatively low energy (less than one-tenth that of a normal supernova), and the progenitor star’s mass was in the range of eight to 10 solar masses — teetering on the thin line between stars that experience a violent supernova death and those that do not.
However, inconsistencies exist between the electron-capture supernova theory and observations of the Crab, particularly the observed rapid motion of the pulsar. In recent years, astronomers have also improved their understanding of iron core-collapse supernovae and now think that this type can also produce low-energy explosions, providing that the stellar mass is adequately low.
Webb Measurements Reconcile Historic ResultsTo lower the level of uncertainty surrounding the Crab’s progenitor star and nature of the explosion, the team led by Temim used Webb’s spectroscopic capabilities to hone in on two areas located within the Crab’s inner filaments.
Theories predict that because of the different chemical composition of the core in an electron-capture supernova, the nickel to iron (Ni/Fe) abundance ratio should be much higher than the ratio measured in our Sun (which contains these elements from previous generations of stars). Studies in the late 1980s and early 1990s measured the Ni/Fe ratio within the Crab using optical and near-infrared data and noted a high Ni/Fe abundance ratio that seemed to favor the electron-capture supernova scenario.
The Webb telescope, with its sensitive infrared capabilities, is now advancing Crab Nebula research. The team used MIRI’s spectroscopic abilities to measure the nickel and iron emission lines, resulting in a more reliable estimate of the Ni/Fe abundance ratio. They found that the ratio was still elevated compared to the Sun, but only modestly and much lower in comparison to prior estimates.
The revised values are consistent with electron-capture, but do not rule out an iron core-collapse explosion from a similarly low-mass star. (Higher-energy explosions from higher-mass stars are expected to produce ratios closer to solar abundances.) Further observational and theoretical work will be needed to distinguish between these two possibilities.
“At present, the spectral data from Webb covers two small regions of the Crab, so it’s important to study much more of the remnant and identify any spatial variations,” said Martin Laming of the Naval Research Laboratory in Washington and a co-author of the paper. “It would be interesting to see if we could identify emission lines from other elements, like cobalt or germanium.”
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Besides pulling spectral data from two small regions of the Crab Nebula’s interior to measure the abundance ratio, the telescope also observed the remnant’s broader environment to understand details of the synchrotron emission and the dust distribution.
The images and data collected by MIRI enabled the team to isolate the dust emission within the Crab and map it in high resolution for the first time. By mapping the warm dust emission with Webb, and even combining it with the Herschel Space Observatory’s data on cooler dust grains, the team created a well-rounded picture of the dust distribution: The outermost filaments contain relatively warmer dust, while cooler grains are prevalent near the center.
“Where dust is seen in the Crab is interesting because it differs from other supernova remnants, like Cassiopeia A and Supernova 1987A,” said Nathan Smith of the Steward Observatory at the University of Arizona and a co-author of the paper. “In those objects, the dust is in the very center. In the Crab, the dust is found in the dense filaments of the outer shell. The Crab Nebula lives up to a tradition in astronomy: The nearest, brightest, and best-studied objects tend to be bizarre.”
These findings have been accepted for publication in The Astrophysical Journal Letters.
The observations were taken as part of General Observer program 1714.
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 CSA (Canadian Space Agency).
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These findings have been accepted for publication in The Astrophysical Journal Letters.
Media ContactsLaura Betz – laura.e.betz@nasa.gov, Rob Gutro – rob.gutro@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Abigail Major – amajor@stsci.edu / Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
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Globetrotting NASA Research Model Increases Accuracy
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater) The NASA 5.2% scale, semi-span version of the High Lift Common Research Model installed in the German-Dutch Wind Tunnels – Braunschweig Low-Speed Wind Tunnel in Braunschweig, Germany on May 4, 2023. NASANASA and its international partners are using the same generically shaped wing design to create physical and digital research models to better understand how air moves around an aircraft during takeoff and landing.
Various organizations are doing computer modeling with computational tools and conducting wind tunnel tests using the same High Lift Common Research Model (CRM-HL), a NASA-led effort.
This ensures the aerospace community is getting accurate answers despite any differences in testing conditions or facilities.
What started as a voluntary partnership in 2019 has grown into the CRM-HL ecosystem with 10 partners across five countries. The team is building eight wind tunnel models, which will be tested at eight wind tunnels during the next three years.
What we are learning today would take us 10 years to do alone. The partners are using each other’s research for the mutual benefit of all.Melissa Rivers
NASA Researcher
“What we are learning today would take us 10 years to do alone,” said Melissa Rivers, subproject manager in NASA’s Transformational Tools and Technologies project, which leads the CRM-HL research. “The partners are using each other’s research for the mutual benefit of all.”
The team will define and assess common wind tunnel conditions in more than 14 tests across the globe.
“Through this research, we are learning about differences that occur when we build and test several identical airplane models in multiple wind tunnels,” Rivers said.
Researchers can use data from these wind tunnel tests to then check if the research tools using computational fluid dynamics are accurately predicting the physics of an aircraft.
“The computer simulations and computational fluid dynamics tools are key contributions from this international partnership,” said NASA’s Mujeeb Malik, a lead researcher for the project. “The runs [tests] are critical to figuring out what we do not know and determining what we want to test.”
The partners are developing a standard way to communicate their data so that everyone can better compare the results from their models and wind tunnel tests.
NASA also is developing a cloud-based solution to give each partner access to the data and foster collaboration.
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This silent, 20-second video shows a computer simulation of air flowing over a 5.2% scale of NASA's High Lift Common Research Model wing design. The color key at lower right indicates the speed of the air.NASA Expanding Collaborations with Common Research ModelsThis high lift research effort builds on the success of a previous Common Research Model effort focused on transonic speeds.
Between 2008 and 2014, many organizations built their own versions of NASA’s model. They then tested the models in tunnels around the world.
The transonic model helped the community better understand the physics of aircraft at cruise. The current high lift model focuses on the takeoff and landing portions of flight when the aircraft is flying slower than at cruise.
Since there are more wind tunnels that can run low-speed tests, more partners can participate in the current collaboration.
The partners working on the CRM-HL span five countries – United States, United Kingdom, France, Germany, and Japan and include:
- NASA
- German Aerospace Center
- National Office for Aerospace Studies and Research, the French Aerospace Lab
- JAXA (Japan Aerospace Exploration Agency)
- European Transonic Wind Tunnel
- Aerospace Technology Institute
- Boeing
- Kawasaki Heavy Industries
- QinetiQ
- Airbus
Data from the CRM-HL research effort also are driving NASA’s High Lift Prediction Workshop series. The series is sponsored by the Applied Aerodynamics Technical Committee of the American Institute of Aeronautics and Astronautics.
The workshops are intended to engage the broader aviation community in these efforts and inspire researchers around the world.
Another goal of this research is to help realize Certification by Analysis, which supports key objectives of the NASA Computational Fluid Dynamics Vision 2030 Study.
NASA, industry, and academia developed the study to lay out a long-term plan for developing future computational capabilities and meeting software and hardware needs for computational fluid dynamics.
The aerospace community will require these resources to efficiently makeaccurate predictions of how air moves around an aircraft. This work also informs the analysis and design of aircraft.
Certification by Analysis would significantly reduce the amount of flight tests required for an aircraft or engine to meet the requirements for airworthiness.
This could save aircraft development programs time and millions of dollars. It could also improve product safety and performance.
The Federal Aviation Administration (FAA) sets the requirements for airworthiness. Companies must provide test results to show new aircraft and engines meet the regulations.
“Before the FAA would allow this type of certification, the analysis must be as accurate as flight testing,” said Rivers.
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