by crissly | Apr 9, 2023 | Uncategorized
Nearly 400,000 years after the Big Bang, the primordial plasma of the infant universe cooled enough for the first atoms to coalesce, making space for the embedded radiation to soar free. That light—the cosmic microwave background (CMB)—continues to stream through the sky in all directions, broadcasting a snapshot of the early universe that’s picked up by dedicated telescopes and even revealed in the static on old cathode-ray televisions.
After scientists discovered the CMB radiation in 1965, they meticulously mapped its tiny temperature variations, which displayed the exact state of the cosmos when it was a mere frothing plasma. Now they’re repurposing CMB data to catalog the large-scale structures that developed over billions of years as the universe matured.
“That light experienced a bulk of the history of the universe, and by seeing how it’s changed, we can learn about different epochs,” said Kimmy Wu, a cosmologist at SLAC National Accelerator Laboratory.
Over the course of its nearly 14-billion-year journey, the light from the CMB has been stretched, squeezed, and warped by all the matter in its way. Cosmologists are beginning to look beyond the primary fluctuations in the CMB light to the secondary imprints left by interactions with galaxies and other cosmic structures. From these signals, they’re gaining a crisper view of the distribution of both ordinary matter—everything that’s composed of atomic parts—and the mysterious dark matter. In turn, those insights are helping to settle some long-standing cosmological mysteries and pose some new ones.
“We’re realizing that the CMB does not only tell us about the initial conditions of the universe. It also tells us about the galaxies themselves,” said Emmanuel Schaan, also a cosmologist at SLAC. “And that turns out to be really powerful.”
A Universe of Shadows
Standard optical surveys, which track the light emitted by stars, overlook most of the galaxies’ underlying mass. That’s because the vast majority of the universe’s total matter content is invisible to telescopes—tucked out of sight either as clumps of dark matter or as the diffuse ionized gas that bridges galaxies. But both the dark matter and the strewn gas leave detectable imprints on the magnification and color of the incoming CMB light.
“The universe is really a shadow theater in which the galaxies are the protagonists and the CMB is the backlight,” Schaan said.
Many of the shadow players are now coming into relief.
When light particles, or photons, from the CMB scatter off electrons in the gas between galaxies, they get bumped to higher energies. In addition, if those galaxies are in motion with respect to the expanding universe, the CMB photons get a second energy shift, either up or down, depending on the relative motion of the cluster.
This pair of effects, known respectively as the thermal and kinematic Sunyaev-Zel’dovich (SZ) effects, were first theorized in the late 1960s and have been detected with increasing precision in the past decade. Together, the SZ effects leave a characteristic signature that can be teased out of CMB images, allowing scientists to map the location and temperature of all the ordinary matter in the universe.
Finally, a third effect known as weak gravitational lensing warps the path of CMB light as it travels near massive objects, distorting the CMB as though it were viewed through the base of a wineglass. Unlike the SZ effects, lensing is sensitive to all matter—dark or otherwise.
Taken together, these effects allow cosmologists to separate the ordinary matter from the dark matter. Then scientists can overlay these maps with images from galaxy surveys to gauge cosmic distances and even trace star formation.
by crissly | Dec 15, 2022 | Uncategorized
SWOT could turn out to be a major improvement over measurements by previous satellites. “Instead of a ‘pencil beam’ moving along the Earth’s surface from a satellite, it’s a wide swath. It’ll provide a lot more information, a lot more spatial resolution, and hopefully better coverage up close to the coasts,” says Steve Nerem, a University of Colorado scientist who uses satellite data to study sea-level rise and is not involved with SWOT. And KaRIn’s swath-mapping technology is a brand-new technique, he says. “It’s never been tested from orbit before, so it’s kind of an experiment. We’re looking forward to the data.”
SWOT has other instruments in its toolkit too, including a radar altimeter to fill in the gaps between the swaths of data KaRIn collects, a microwave radiometer to measure the amount of water vapor between SWOT and the Earth’s surface, and an array of mirrors for laser-tracking measurements from the ground.
New satellite data is important because the future of sea-level rise, floods, and droughts may be worse than some experts previously forecast. “Within our satellite record, we’ve seen sea-level rise along US coastlines going up fast over the past three decades,” says Ben Hamlington, a sea-level rise scientist at JPL on the SWOT science team. The rate of sea-level rise is in fact accelerating, especially on the Gulf Coast and East Coast of the United States. “The trajectory we’re on is pointing us to the higher end of model projections,” he says, a point he made in a study last month in the journal Communications Earth & Environment.
Hamlington sees SWOT as a boon for mapping rising sea waters and for researchers studying ocean currents and eddies, which affect how much atmospheric heat and carbon oceans absorb. The satellite will also aid scientists who model storm surges—that is, when ocean water flows onto land.
The new spacecraft’s data will have some synergy with many other Earth-observing satellites already in orbit. Those include NASA’s Grace-FO, which probes underground water via gravity fluctuations, NASA’s IceSat-2, which surveys ice sheets, glaciers, and sea ice, and commercial flood-mapping satellites that use synthetic aperture radar to see through clouds. It also follows other altimeter-equipped satellites, like the US-European Jason-3, the European Space Agency’s Sentinel-6 Michael Freilich satellite, China’s Haiyang satellites, and the Indian-French Saral spacecraft.
Data from these satellites has already shown that some degree of sea-level rise, extreme floods, storms, and droughts are already baked into our future. But we’re not doomed to climate catastrophes, Hamlington argues, because we can use this data to fend off the most extreme projected outcomes, like those that cause rapid glacier or ice sheet melt. “Reducing emissions takes some of the higher projections of sea-level rise off the table,” he says. “Since catastrophic ice sheet loss will only occur under very warm futures, if we can limit warming going forward, we can avoid worst-case scenarios.”
by crissly | Dec 12, 2022 | Uncategorized
After circling the moon for the past three weeks, NASA’s Orion capsule splashed down under parachute yesterday morning off the coast of Mexico’s Baja California near Guadalupe Island, marking an end to the Artemis program’s first major lunar mission. Orion was then scooped up by a recovery crew and sent to port in San Diego, carried in the well of the Navy ship USS Portland. With Artemis 1 in the books, NASA will scrutinize the capsule’s performance, making sure it is safe for future crewed trips to the moon, including a much-anticipated lunar landing in 2026.
“It’s a historic achievement because we are now going back into deep space with a new generation,” said NASA chief Bill Nelson following Orion’s splashdown. “This is a defining day. It is one that marks new technology, a whole new breed of astronaut, a vision for the future.”
During Sunday’s descent, the three parachutes fully inflated, putting the brakes on the spacecraft to slow it from 25,000 miles per hour to just 20 as it hurtled through the atmosphere. But now the Artemis team will be studying all the capsule’s metrics in detail. “First we’ll be looking at: Did the heat shield do its job in rejecting heat and taking care of the heat pulse such that the internal cabin pressure stays at a moderate mid-70 degrees for astronauts when they’re in there?” says Sarah D’Souza, the deputy systems manager at the NASA Ames Research Center who helped develop Orion’s thermal protection system.
That ablative heat shield is made up of thick connected blocks of an epoxy resin material called Avcoat, which burns off as the shield endures scorching temperatures up to 5,000 degrees Fahrenheit, about half the temperature of the surface of the sun. They want to be sure, she says, that “we’ve got a design that will keep humans safe.”
Nelson, too, stressed human safety and habitability during a post-splashdown press conference. “This time we go back to the moon to learn to live, to work, to invent, to create, in order to go on out into the cosmos to further explore,” he said. “The plan is to get ready to go with humans to Mars in the late 2030s, and then even further beyond.”
Orion was originally planned to splash down off the coast of San Diego, but the weather forecast there made that a no-go, and the flight director adjusted its trajectory. That flexibility comes thanks to a maneuver the team attempted called a “skip” reentry, in which Orion descended partway through the atmosphere to an altitude of about 40 miles, then skipped upward and forward like a pebble skimming across a pond, and then entered the atmosphere for good. That kind of reentry also helps to slow down the spacecraft.
The reentry brought Orion within 0.02 degrees of the team’s planned flight angle, and the splashdown into the ocean was a near bullseye, about 2 nautical miles from its target landing site. Once the chutes drifted down, all five balloon-like bags inflated, keeping Orion upright in the water. NASA and Navy officials on the recovery team—in helicopters and boats—then made their approach, preparing to retrieve the spacecraft and stow it in the belly of the USS Portland for the trek back to shore.
by crissly | Nov 18, 2022 | Uncategorized
James Webb led NASA in the 1950s and 60s, during the Cold War–era “Lavender Scare,” when government agencies often enforced policies that discriminated against gay and lesbian federal workers. For that reason, astronomers and others have long called for NASA to change the name of the James Webb Space Telescope. Earlier this year, the space agency agreed to complete a full investigation into Webb’s suspected role in the treatment and firing of LGBTQ employees.
This afternoon, NASA released that long-awaited report by the agency’s chief historian Brian Odom. In an accompanying press release, NASA officials made clear that the agency will not change the telescope’s name, writing: “Based on the available evidence, the agency does not plan to change the name of the James Webb Space Telescope. However, the report illuminates that this period in federal policy—and in American history more broadly—was a dark chapter that does not reflect the agency’s values today.”
Odom was tasked with finding what proof, if any, links Webb to homophobic policies and decisions. Tracking down evidence of contentious 60-year-old events made for a difficult subject of study, Odom says, but he was able to draw on plenty of material from the National Archives in College Park, Maryland, and the Truman Library. “I took this investigation very seriously,” he says.
These allegations include those made by NASA employee Clifford Norton, who filed a lawsuit claiming that he had been fired in 1963 after he was seen in a car with another man. He was taken into police custody, his lawsuit states, and NASA security subsequently brought him to the agency’s headquarters and interrogated him throughout the night. He was later terminated from his job.
Such treatment of federal employees suspected to be gay or lesbian was commonplace at the time, following a 1953 executive order by President Dwight Eisenhower, which listed “sexual perversion” among the kinds of behaviors considered suspicious. Still, the NASA report states, “No evidence has been located showing Webb knew of Norton’s firing at the time. Because it was accepted policy across the government, the firing was, highly likely—though, sadly—considered unexceptional.”
The report and NASA’s announcement frustrate critics who for years have been making a case to change JWST’s name. “Webb has at best a complicated legacy, including his participation in the promotion of psychological warfare. His activities did not earn him a $10 billion monument,” wrote Chanda Prescod-Weinstein, an astrophysicist at the University of New Hampshire, and three other astronomers and astrophysicists in a statement on Substack today. They question the interpretation that a lack of explicit evidence implies that Webb had no knowledge of, or hand in, firings within his own agency, writing: “In such a scenario, we have to assume he was relatively incompetent as a leader: the administrator of NASA should know if his chief of security is extrajudicially interrogating people.”
Prescod-Weinstein believes the timing of this release—on the Friday afternoon before the Thanksgiving holiday—isn’t a coincidence, a way to make the report less widely read. “The fact that they did it even though it’s LGBT STEM Day tells you about the administration’s priorities,” she wrote in an email to WIRED.
NASA usually names telescopes after prominent astronomers, like the Hubble, Spitzer, Chandra, and Compton telescopes. Webb is an exception. He led the agency while it advanced the space program toward the moon landing and promoted astronomy research, but he was a bureaucrat, not an astronomer.
Even though agency officials made the call to keep Webb’s name, Odom says, “We should still use this history as an example of a past that was traumatic for a lot of people. This past, whatever Webb’s role in it was, is important to us going forward.”
That NASA is choosing not to rename the telescope is “not surprising, but disappointing,” says Ralf Danner, a Jet Propulsion Laboratory astronomer and cochair of the American Astronommical Society’s committee for sexual orientation and gender minorities in astronomy. Whether Webb knew of Norton’s treatment, or whether evidence of that exists, is not really relevant, Danner argues, since Webb stood for those policies as NASA administrator. “He’s just the wrong name to show the future of astronomy.”
by crissly | Sep 26, 2022 | Uncategorized
NASA’s team leading the Artemis program of lunar missions really wants to get on with their inaugural spaceflight—which was slated for tomorrow morning. But with a strengthening Hurricane Ian barreling toward the Florida launchpad, it’s time to move the massive Space Launch System rocket to safety.
The space agency will roll the rocket back to the Vehicle Assembly Building to wait for another launch opportunity—but that might mean a delay of several weeks. The team has not yet committed to a date for a new attempt, although a backup window once planned for October 2 now looks all but doomed. “A determination on the return to the pad for launch will be made once the storm has passed and teams conduct post-storm inspections,” Tiffany Fairley, a NASA spokesperson at Kennedy Space Center, wrote in an email to WIRED.
After a series of delays this summer, the Artemis team hoped to finally launch the uncrewed moon rocket from Kennedy in eastern Florida. But worries arose about wind damage to the spacecraft and risks to personnel at the space center. Heading into the weekend, NASA’s weather officers mapped the trajectory of Ian, which at that point was a tropical cyclone that appeared to be gaining strength and heading for landfall in Florida on launch day. The rocket can only tolerate sustained winds up to 74 knots when it’s on the launchpad, said Mike Folger, Exploration Ground Systems program manager at Kennedy, during a press conference on September 23. If those weather forecasts were right, the storm would soon become a hurricane, and winds exceeding that speed would hit Florida’s Space Coast.
NASA had to take into account the weather criteria not only for launching the rocket, but also for getting it moved to shelter, according to a post on NASA’s Artemis blog. Since the trip takes up to 12 hours, and the rocket can only take winds up to 40 knots while on the crawler that ferries it to and from the assembly building, the Artemis team had to make the call Monday morning to get the SLS under cover by Tuesday evening.
This would have been NASA’s third launch attempt. A first try on August 29 was scrubbed due to a liquid hydrogen leak discovered with the third RS-25 engine. (The rocket weathered a smaller storm then, with lightning striking towers nearby, but not the rocket itself.) A second shot on September 3 was also called off due to a hydrogen leak—this time it was larger. (Similar issues were also spotted in April and in June when the team ran “wet dress rehearsal” tests of the fueling and countdown procedures.)
The SLS uses liquid hydrogen supercooled down to -423 degrees Fahrenheit. That’s a light, efficient, and powerful rocket propellant, but it comes with its own challenges. “Cryogenics is a very difficult kind of propellant to handle,” said Brad McCain, vice president of Jacobs Space Operations Group, prime contractor for NASA’s Exploration Ground Systems, at the press conference on September 23. He noted that liquid hydrogen leaks frequently popped up during the 135 space shuttle launches. With the SLS, he said, a “kinder, gentler loading approach,” using less pressure to push the propellant through the lines to the core-stage rocket, worked during a tanking test on September 21.