How NASA’s Roman Mission Will Hunt for Primordial Black Holes - UNIVERSE

Astronomers have discovered black holes ranging from a few times the Sun’s mass to tens of billions. Now a group of scientists has predicted that NASA’s Nancy Grace Roman Space Telescope could find a class of “featherweight” black holes that has so far eluded detection.

Today, black holes form either when a massive star collapses or when heavy objects merge. However, scientists suspect that smaller “primordial” black holes, including some with masses similar to Earth’s, could have formed in the first chaotic moments of the early universe.

This artist’s concept takes a fanciful approach to imagining small primordial black holes. In reality, such tiny black holes would have a difficult time forming the accretion disks that make them visible here. NASA’s Goddard Space Flight Center

“Detecting a population of Earth-mass primordial black holes would be an incredible step for both astronomy and particle physics because these objects can’t be formed by any known physical process,” said William DeRocco, a postdoctoral researcher at the University of California Santa Cruz who led a study about how Roman could reveal them. A paper describing the results has been published in the journal Physical Review D. “If we find them, it will shake up the field of theoretical physics.”

Primordial Black Hole Recipe

The smallest black holes that form nowadays are born when a massive star runs out of fuel. Its outward pressure wanes as nuclear fusion dies down, so inward gravitational pull wins the tug-of-war. The star contracts and may get so dense it becomes a black hole.

But there’s a minimum mass required: at least eight times that of our Sun. Lighter stars will either become white dwarfs or neutron stars.

Conditions in the very early universe, however, may have allowed far lighter black holes to form. One weighing the mass of Earth would have an event horizon –– the point of no return for infalling objects –– about as wide as a U.S. dime coin.

Just as the universe was being born, scientists think it experienced a brief but intense phase known as inflation when space expanded faster than the speed of light. In these special conditions, areas that were denser than their surroundings may have collapsed to form low-mass primordial black holes.

While theory predicts the smallest ones should evaporate before the universe has reached its current age, those with masses similar to Earth could have survived.

Discovering these tiny objects would have an enormous impact on physics and astronomy.

“It would affect everything from galaxy formation to the universe’s dark matter content to cosmic history,” said Kailash Sahu, an astronomer at the Space Telescope Science Institute in Baltimore, who was not involved in the study. “Confirming their identities will be hard work and astronomers will need a lot of convincing, but it would be well worth it.”

Stephen Hawking theorized that black holes can slowly shrink as radiation escapes. The slow leak of what’s now known as Hawking radiation would, over time, cause the black hole to simply evaporate. This infographic shows the estimated lifetimes and event horizon –– the point past which infalling objects can’t escape a black hole’s gravitational grip –– diameters for black holes of various small masses. NASA’s Goddard Space Flight Center

Hints of Hidden Homesteaders

Observations have already revealed clues that such objects may be lurking in our galaxy. Primordial black holes would be invisible, but wrinkles in space-time have helped round up some possible suspects.

Microlensing is an observational effect that occurs because the presence of mass warps the fabric of space-time, like the imprint a bowling ball makes when set on a trampoline. Any time an intervening object appears to drift near a background star from our vantage point, the star’s light must traverse the warped space-time around the object. If the alignment is especially close, the object can act like a natural lens, focusing and amplifying the background star’s light.

Separate groups of astronomers using data from MOA (Microlensing Observations in Astrophysics) –– a collaboration that conducts microlensing observations using the Mount John University Observatory in New Zealand –– and OGLE (the Optical Gravitational Lensing Experiment) have found an unexpectedly large population of isolated Earth-mass objects.

Planet formation and evolution theories predict certain masses and abundances of rogue planets ––worlds roaming the galaxy untethered to a star. The MOA and OGLE observations suggest there are more Earth-mass objects drifting through the galaxy than models predict.

“There’s no way to tell between Earth-mass black holes and rogue planets on a case-by-case basis,” DeRocco said. But scientists expect Roman to find 10 times as many objects in this mass range than ground-based telescopes. “Roman will be extremely powerful in differentiating between the two statistically.”

DeRocco led an effort to determine how many rogue planets should be in that mass range, and how many primordial black holes Roman could discern amongst them.

Finding primordial black holes would reveal new information about the very early universe, and would strongly suggest that an early period of inflation did indeed occur. It could also explain a small percentage of the mysterious dark matter scientists say makes up the bulk of our universe’s mass, but have so far been unable to identify.

“This is an exciting example of something extra scientists could do with data Roman is already going to get as it searches for planets,” Sahu said. “And the results are interesting whether or not scientists find evidence that Earth-mass black holes exist. It would strengthen our understanding of the universe in either case.”

The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA’s Jet Propulsion Laboratory and Caltech/IPAC in Southern California, the Space Telescope Science Institute in Baltimore, and a science team comprising scientists from various research institutions. The primary industrial partners are BAE Systems, Inc in Boulder, Colorado; L3Harris Technologies in Rochester, New York; and Teledyne Scientific & Imaging in Thousand Oaks, California.

Download high-resolution video and images from NASA’s Scientific Visualization Studio

By Ashley Balzer
NASA’s Goddard Space Flight Center, Greenbelt, Md. 

Source: How NASA’s Roman Mission Will Hunt for Primordial Black Holes - NASA

International SWOT Mission Can Improve Flood Prediction - EARTH

Flooding on the Souris River inundated this community in North Dakota in 2011. The U.S.-French SWOT satellite is giving scientists and water managers a new tool to look at floods in 3D, information that can improve predictions of where and how often flooding will occur. Credit: North Dakota State Water Commission

A partnership between NASA and the French space agency, the satellite is poised to help improve forecasts of where and when flooding will occur in Earth’s rivers, lakes, and reservoirs.

Rivers, lakes, and reservoirs are like our planet’s arteries, carrying life-sustaining water in interconnected networks. When Earth’s water cycle runs too fast, flooding can result, threatening lives and property. That risk is increasing as climate change alters precipitation patterns and more people are living in flood-prone areas worldwide.

Scientists and water managers use many types of data to predict flooding. This year they have a new tool at their disposal: freshwater data from the Surface Water and Ocean Topography (SWOT) satellite. The observatory, a collaboration between NASA and the French space agency, CNES (Centre National d’Études Spatiales), is measuring the height of nearly all water surfaces on Earth. SWOT was designed to measure every major river wider than about 300 feet (100 meters), and preliminary results suggest it may be able to observe much smaller rivers.

Stream gauges can accurately measure water levels in rivers, but only at individual locations, often spaced far apart. Many rivers have no stream gauges at all, particularly in countries without resources to maintain and monitor them. Gauges can also be disabled by floods and are unreliable when water overtops the riverbank and flows into areas they cannot measure.

SWOT provides a more comprehensive, 3D look at floods, measuring their height, width, and slope. Scientists can use this data to better track how floodwaters pulse across a landscape, improving predictions of where flooding will occur and how often.

Building a Better Flood Model

One effort to incorporate SWOT data into flood models is led by J. Toby Minear of the Cooperative Institute for Research in Environmental Sciences (CIRES) in Boulder, Colorado. Minear is investigating how to incorporate SWOT data into the National Oceanic and Atmospheric Administration’s National Water Model, which predicts the potential for flooding and its timing along U.S. rivers. SWOT freshwater data will fill in spatial gaps between gauges and help scientists like Minear determine the water levels (heights) at which flooding occurs at specific locations along rivers. 

UNC-Chapel Hill doctoral student Marissa Hughes levels a tripod to install a GPS unit to precisely measure the water surface elevation of a segment of New Zealand’s Waimakariri River. The measurements were used to calibrate and validate data from the U.S.-French SWOT satellite. Credit: Alyssa LaFaro/UNC Research

He expects SWOT to improve National Water Model data in multiple ways. For example, it will provide more accurate estimates of river slopes and how they change with streamflow. Generally speaking, the steeper a river’s slope, the faster its water flows. Hydrologic modelers use slope data to predict the speed water moves through a river and off a landscape.

SWOT will also help scientists and water managers quantify how much water lakes and reservoirs can store. While there are about 90,000 relatively large U.S. reservoirs, only a few thousand of them have water-level data that’s incorporated into the National Water Model. This limits scientists’ ability to know how reservoir levels relate to surrounding land elevations and potential flooding. SWOT is measuring tens of thousands of U.S. reservoirs, along with nearly all natural U.S. lakes larger than about two football fields combined.

Some countries, including the U.S., have made significant investments in river gauging networks and detailed local flood models. But in Africa, South Asia, parts of South America, and the Arctic, there’s little data for lakes and rivers. In such places, flood risk assessments often rely on rough estimates. Part of SWOT’s potential is that it will allow hydrologists to fill these gaps, providing information on where water is stored on landscapes and how much is flowing through rivers.

Tamlin Pavelsky, NASA’s SWOT freshwater science lead and a researcher at the University of North Carolina at Chapel Hill, says SWOT can help address the growing threat of flooding from extreme storms fueled by climate change. “Think about Houston and Hurricane Harvey in 2017,” he said. “It’s very unlikely we would have seen 60 inches of rain from one storm without climate change. Societies will need to update engineering design standards and floodplain maps as intense precipitation events become more common.”

Pavelsky says these changes in Earth’s water cycle are altering society’s assumptions about floods and what a floodplain is. “Hundreds of millions of people worldwide will be at increased risk of flooding in the future as rainfall events become increasingly intense and population growth occurs in flood-prone areas,” he added.

SWOT flood data will have other practical applications. For example, insurers can use models informed by SWOT data to improve flood hazard maps to better estimate an area’s potential damage and loss risks. A major reinsurance company, FM Global, is among SWOT’s 40 current early adopters — a global community of organizations working to incorporate SWOT data into their decision-making activities.

“Companies like FM Global and government agencies like the U.S. Federal Emergency Management Agency can fine tune their flood models by comparing them to SWOT data,” Pavelsky said. “Those better models will give us a more accurate picture of where and how often floods are likely to happen.”

More About the Mission

Launched on Dec. 16, 2022, from Vandenberg Space Force Base in central California, SWOT is now in its operations phase, collecting data that will be used for research and other purposes.

SWOT was jointly developed by NASA and CNES, with contributions from the Canadian Space Agency (CSA) and the UK Space Agency. NASA’s Jet Propulsion Laboratory, managed for the agency by Caltech in Pasadena, California, leads the project’s U.S. component. For the flight system payload, NASA provided the KaRIn instrument, a GPS science receiver, a laser retroreflector, a two-beam microwave radiometer, and NASA instrument operations. CNES provided the Doppler Orbitography and Radioposition Integrated by Satellite (DORIS) system, dual frequency Poseidon altimeter (developed by Thales Alenia Space), KaRIn radio-frequency subsystem (together with Thales Alenia Space and with support from the UK Space Agency), the satellite platform, and ground operations. CSA provided the KaRIn high-power transmitter assembly. NASA provided the launch vehicle and the agency’s Launch Services Program, based at Kennedy Space Center, and managed the associated launch services.

For more on SWOT, visit: https://swot.jpl.nasa.gov/. 

Source: International SWOT Mission Can Improve Flood Prediction - NASA