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Written by: NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

Published: 19 June 2022

A star's death throes have so violently disrupted its planetary system that the dead star left behind, called a white dwarf, is siphoning off debris from both the system's inner and outer reaches. This is the first time astronomers have observed a white dwarf star that is consuming both rocky-metallic and icy material, the ingredients of planets.

Archival data from NASA's Hubble Space Telescope and other NASA observatories were essential in diagnosing this case of cosmic cannibalism. The findings help describe the violent nature of evolved planetary systems and can tell astronomers about the makeup of newly forming systems.

The findings are based on analyzing material captured by the atmosphere of the nearby white dwarf star G238-44. A white dwarf is what remains of a star like our Sun after it sheds its outer layers and stops burning fuel though nuclear fusion. "We have never seen both of these kinds of objects accreting onto a white dwarf at the same time," said Ted Johnson, the lead researcher and recent University of California, Los Angeles (UCLA) bachelor's graduate. "By studying these white dwarfs, we hope to gain a better understanding of planetary systems that are still intact."

The findings are also intriguing because small icy objects are credited for crashing into and "irrigating" dry, rocky planets in our solar system. Billions of years ago comets and asteroids are thought to have delivered water to Earth, sparking the conditions necessary for life as we know it. The makeup of the bodies detected raining onto the white dwarf implies that icy reservoirs might be common among planetary systems, said Johnson.

"Life as we know it requires a rocky planet covered with a variety of elements like carbon, nitrogen, and oxygen," said Benjamin Zuckerman, UCLA professor and co-author. "The abundances of the elements we see on this white dwarf appear to require both a rocky and a volatile-rich parent body – the first example we've found among studies of hundreds of white dwarfs."

Demolition derby

Theories of planetary system evolution describe the transition between a red giant star and white dwarf phases as a chaotic process. The star quickly loses its outer layers and its planets' orbits dramatically change. Small objects, like asteroids and dwarf planets, can venture too close to giant planets and be sent plummeting toward the star. This study confirms the true scale of this violent chaotic phase, showing that within 100 million years after the beginning of its white dwarf phase, the star is able to simultaneously capture and consume material from its asteroid belt and Kuiper belt-like regions.

The estimated total mass eventually gobbled up by the white dwarf in this study may be no more than the mass of an asteroid or small moon. While the presence of at least two objects that the white dwarf is consuming is not directly measured, it's likely one is metal-rich like an asteroid and another is an icy body similar to what's found at the fringe of our solar system in the Kuiper belt.

Though astronomers have cataloged over 5,000 exoplanets, the only planet where we have some direct knowledge of its interior makeup is Earth. The white dwarf cannibalism provides a unique opportunity to take planets apart and see what they were made of when they first formed around the star.

The team measured the presence of nitrogen, oxygen, magnesium, silicon and iron, among other elements. The detection of iron in a very high abundance is evidence for metallic cores of terrestrial planets, like Earth, Venus, Mars, and Mercury. Unexpectedly high nitrogen abundances led them to conclude the presence of icy bodies.

"The best fit for our data was a nearly two-to-one mix of Mercury-like material and comet-like material, which is made up of ice and dust," Johnson said. "Iron metal and nitrogen ice each suggest wildly different conditions of planetary formation. There is no known solar system object with so much of both."

Death of a planetary system

When a star like our Sun expands into a bloated red giant late in its life, it will shed mass by puffing off its outer layers. One consequence of this can be the gravitational scattering of small objects like asteroids, comets, and moons by any remaining large planets. Like pinballs in an arcade game, the surviving objects can be thrown into highly eccentric orbits.

"After the red giant phase, the white dwarf star that remains is compact – no larger than Earth. The wayward planets end up getting very close to the star and experience powerful tidal forces that tear them apart, creating a gaseous and dusty disk that eventually falls onto the white dwarf's surface," Johnson explained.

The researchers are looking at the ultimate scenario for the Sun's evolution, 5 billion years from now. Earth might be completely vaporized along with the inner planets. But the orbits of many of the asteroids in the main asteroid belt will be gravitationally perturbed by Jupiter and will eventually fall onto the white dwarf that the remnant Sun will become.

For over two years, the research group at UCLA, the University of California, San Diego and the Kiel University in Germany, has worked to unravel this mystery by analyzing the elements detected on the white dwarf star cataloged as G238-44. Their analysis includes data from NASA's retired Far Ultraviolet Spectroscopic Explorer (FUSE), the Keck Observatory's High Resolution Echelle Spectrometer (HIRES) in Hawaii, and the Hubble Space Telescope's Cosmic Origins Spectrograph (COS) and Space Telescope Imaging Spectrograph (STIS).

The team's results were presented at an American Astronomical Society (AAS) press conference on Wednesday, June 15, 2022.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

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Written by: GEORGINA MARIE GUARDADO

Published: 18 June 2022

LAKE COUNTY, Calif. — The National Endowment for the Arts, or NEA, in partnership with Arts Midwest, has announced support for 62 nonprofit organizations to hold NEA Big Read programming in 2022-2023.

Among the grantees is the Lake County Library.

In total, the NEA is investing $1,071,140 to support programming centered around one of 15 different contemporary books, with the aim of inspiring meaningful conversations, artistic responses, and new discoveries and connections in participating communities.

The NEA Big Read showcases a diverse range of contemporary titles that reflect many different voices and perspectives, aiming to inspire conversation and discovery.

The Lake County Library is a recipient of a $9,500 grant to host the NEA Big Read countywide with dynamic community reading programs, and has selected Postcolonial Love Poem by Natalie Diaz for 2023 programming.

Activities will take place from February 2023 to March 2023.

Winner of the 2021 Pulitzer Prize in Poetry, Postcolonial Love Poem is a collection of poetry by Arizona poet Natalie Diaz — who is Mojave, an enrolled member of the Gila River Indian Tribe, Latinx and queer.

The poems push against the forces of racism, environmental destruction, addiction, and mental illness with the power of desire, love, and language.

From publisher Gray Wolf Press, “Postcolonial Love Poem is an anthem of desire against erasure. Natalie Diaz’s brilliant second collection demands that every body carried in its pages — bodies of language, land, rivers, suffering brothers, enemies, and lovers — be touched and held as beloveds.”

Confirmed partners for the 2023 program include the County of Lake Board of Supervisors, Scotts Valley Band of Pomo Indians, Mendocino College Lake Center, Lake County Campus of Woodland Community College, Lake County Special Districts, Lake County Library Genealogy and Local History Group, Museums of Lake County, Lake County Office of Education, Lake County Farmers’ Finest, Lake County Arts Council, Middletown Art Center and O'Meara Bros. Brewing Company. Organizers expect to add more partners as planning continues.

Follow the Lake County Library on Facebook, Instagram and Twitter, or sign up for their online newsletter for updates. Visit the Lake County Library’s website at http://library.lakecountyca.gov.

Georgina Marie Guardado is the Lake County Library’s Adult Literacy Program coordinator.

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Written by: LAKE COUNTY NEWS REPORTS

Published: 18 June 2022

CLEARLAKE OAKS, Calif. — Pacific Gas and Electric Co. said several projects are underway in Lake County to harden the electric system and build a safer and more resilient power grid for its customers and communities.

In Lake County, PG&E plans to underground approximately 15 miles of overhead distribution power lines and harden 21 miles in high fire-threat areas to reduce wildfire risk in 2022.

“As part of our efforts to evolve with California’s changing weather conditions, we are working year-round to make our system safer, and that includes placing overhead lines underground where we can and installing stronger power poles with covered conductors,” said Ron Richardson, regional vice president for PG&E’s North Coast Region. “Not only will undergrounding reduce ignition risk by 99% on undergrounded circuits, but it will reduce spending on temporary repairs and recurring costs such as vegetation management and curb the need for wildfire safety-related outages.”

Crews have started preliminary work to underground approximately 9 miles of a distribution line in sections from Clearlake Oaks along parts of Highway 20 to Spring Valley.

PG&E has notified customers of field surveys to be conducted through the second half of June.

As part of the surveys, field crews will locate property corners and pick up topographical features. Helicopters may also be used to gather this information.

Residents in these areas may also see different colors of spray paint on the ground and around PG&E equipment. These are markings so workers know where existing underground utilities are located, such as power lines, water, sewer, storm drains and communications.

PG&E will be marking the ground over the next three weeks with red spray paint where electrical equipment is located. Each commodity has a different color to mark the location of their underground equipment.

“Customers in the areas of future undergrounding may also notice markings on the ground that look like “X’s” or a chess board. These are flight panels that help us establish horizontal and vertical control. It’s how everyone working on the project can be on the same coordinate system,” said Brett Brusatori, supervisor for PG&E Land Surveying.

Undergrounding is part of PG&E’s Community Wildfire Safety Program, which the company launched in 2018 to help keep customers and communities safe in the face of growing wildfire risk across our state.

Nearly one-third of the electric power lines that serve PG&E’s customers are now in High Fire-Threat Districts designated by the California Public Utilities Commission.

Undergrounding is just one of the system-hardening tools PG&E uses to reduce wildfire risks.

Depending on the needs of the community, PG&E reviews additional risk-reduction efforts including installing stronger poles, covered power lines and sectionalizing devices; conducting enhanced vegetation management; adjusting power line safety settings; and implementing public safety power shut-offs.

Even though PG&E’s power lines will be moved underground, some of the power poles in these areas could remain in place to carry service lines that feed customer homes and to carry telecommunications equipment for other companies.

On July 21, 2021, PG&E announced a new, multiyear infrastructure safety initiative to underground approximately 10,000 miles of power lines in and near high fire-threat areas. It’s reported to be the largest effort in the U.S. to underground power lines as a wildfire risk reduction measure.