Science
Dark Skies and Dark Energy Converge at a West Texas Star Party
Two billion years after the cosmos banged into existence, a mysterious force known as dark energy began shoving space outward, causing the universe to balloon faster and faster and threatening to one day rip apart everything within it, from clusters of galaxies to particles inside atoms.
Astronomers have taken on the behemoth task of figuring out the fate of our nearly 14-billion-year-old universe by understanding what dark energy is, and how exactly it works. But on Earth, they can do so only under the darkest of night skies. For a team of researchers, that meant setting up shop at the McDonald Observatory in the remote Big Bend region of West Texas, in the biggest dark-sky reserve on the planet.
“We wanted to go for the most distant objects that we could see on a telescope,” said Karl Gebhardt, an astronomer at the University of Texas at Austin and the father of the Hobby-Eberly Telescope Dark Energy Experiment, or HETDEX. Those objects, he explained, are galaxies as far away as 12 billion light-years, and they are faint enough to be obscured by the brightness of the full moon, or too many well-lit storefronts.
The dark skies of Big Bend enabled the HETDEX team to collect data from 2017 to 2024; now, Dr. Gebhardt and his colleagues are on the cusp of their first major result. But the region’s starry nights are valued for far more than their scientific merit. They have also inspired an ecosystem of dark-sky advocacy that extends beyond astronomers’ desire to decipher the universe, particularly as light pollution encroaches on the ability to see the stars.
Each year, tens of thousands of visitors, mostly Texans from the bigger cities, trek up the mountains to attend “star parties” thrown regularly by McDonald Observatory. Nearly 400 people signed up for the star party last Friday, one of several events celebrating International Dark Sky Week throughout the region.
According to Stephen Hummel, who coordinates McDonald’s dark-sky outreach, local ordinances exist across Big Bend to minimize light pollution at night. But much of the effort is voluntary. “I don’t think astronomy is the biggest motivator for adopting these practices,” Mr. Hummel said before Friday’s star party, timed to April’s new moon.
Access to the stars “is part of the landscape, like the mountains are,” he said. “For many people, you can’t think about the Big Bend region without thinking about the night sky. It’s integral to its identity.”
At the speed of night
Scientists first discovered that the universe was expanding ever faster in 1998 by observing a certain kind of supernova, or exploding star. These supernovas emit the same amount of light regardless of where they sit in the universe; this makes it possible to predict how bright such events should appear given their distances from Earth.
If gravity were slowing down the expansion of the universe, as astronomers believed would be the case, such supernovas should have looked slightly brighter than predicted. Instead, those supernovas appeared dimmer: The expansion of the universe was speeding up.
“‘Dark energy’ is the phrase we use to represent our ignorance of how the universe is expanding,” Dr. Gebhardt said. But “it may not be dark. It may not be energy.”
One way to investigate the nature of dark energy is to chart the spread of matter across the cosmos, a pattern that froze in place as the universe cooled after the Big Bang. That pattern is a bit like a cosmic fingerprint: Its ridges have stretched as the universe has grown larger. Astronomers can measure this expansion by mapping the positions of galaxies in different eras of cosmic time.
The HETDEX team is attempting to make a map of the universe as it was between 10 billion and 12 billion years ago, an earlier epoch than any dark-energy survey has yet reached.
“I didn’t want to observe the same region of the universe and just try to do a better job,” Dr. Gebhardt said. “I wanted to do something new.”
Star-forming galaxies in this era of cosmic time emit photons, or particles of light, at a specific ultraviolet wavelength. As the universe expands, that wavelength gets stretched out, and the light is in the visible range by the time it reaches Earth.
To capture this ancient light, HETDEX researchers employed the giant Hobby-Eberly Telescope, which consists of 91 hexagonal mirrors tiled together like a reflective honeycomb. Tens of thousands of cables feed any collected photons into a set of spectrographs, which split the light into a rainbow of different colors. This data helps astronomers identify which light came from distant galaxies and calculate the source’s distance from Earth.
Using the galaxies’ depth and position in the night sky, scientists can construct a three-dimensional map of the early universe.
But the galaxies targeted by HETDEX are so far and faint that sometimes only a couple of hundred photons make it to Earth. Even in as dark and remote a place as Big Bend, that meant the survey could be done only when the moon was not visible, lest it wash out the telescope’s view. According to Taft Armandroff, the director of McDonald Observatory, the site has some of the darkest skies on the continent.
“It is really, really critical for the astronomy we do,” Dr. Armandroff said in an interview in January.
Astronomers have been exploring the universe at McDonald since 1939. But the effort to legally protect the darkness of the region with outdoor lighting regulations began in the 1970s, as ranching communities around the observatory began to grow. The Greater Big Bend International Dark Sky Reserve was formally designated in 2022.
Today, the reserve spans more than nine million acres across Texas and Mexico and includes several small towns, historical sites, protected wildlife areas and natural parks. With the observatory’s encouragement, the darkness has become its own attraction. It has also become an inspiration for economic opportunity, environmental conservation and pride in a rural way of life.
A party under the stars
A winding road, flanked by yellow grasslands and accented by the occasional javelina or roadrunner, leads up to the three research telescopes, situated atop neighboring mountain peaks, of McDonald Observatory. Smaller telescopes, used for education and outreach, dot the area below the summits.
The sky blushed pink as the sun dipped behind the Davis Mountains late on the Friday afternoon of International Dark Sky Week. The silver dome of the Hobby-Eberly Telescope creaked open as operators prepared for nightly observations.
Below, stargazers crowded into the visitor center to learn about light pollution and dark-sky-friendly illumination. Bats swooped through the breezy twilight air, and visitors ambled toward the outdoor amphitheater for a guided tour of the heavens. Clouds that had rolled in at sunset suddenly dissipated, revealing a moonless night splattered with stars. Orion beamed in the western sky, the Big Dipper in the northeast — the two constellations around which HETDEX had focused its galactic survey.
“If y’all don’t know what dark energy is, don’t feel bad,” the star party’s host said. “Neither do we!”
The HETDEX survey completed observations two summers ago, and astronomers have been analyzing its data since. Their first measurement of dark energy in the early universe is expected to come out this year.
“I thought that I was going to get depressed or tired,” said Dr. Gebhardt, who conceived the project more than two decades ago. “But I’ve never been more excited.”
Already, HETDEX scientists are thinking bigger. They hope to use the Hobby-Eberly to scan the entire night sky, increasing their pool of data to further refine their knowledge of dark energy in distant cosmic time.
But for now, Hobby-Eberly has lighter fare to study: the atmospheres of stars, planets circling faraway suns, the gravitational influence of galaxies central to other experiments. And on this Friday night, the star-party attendees had their own observations to make, including of cloud bands on Jupiter and a nursery of baby stars just south of Orion’s belt, 15,000 light-years away.
Julian Muñoz, a theoretical astrophysicist who joined HETDEX in 2023, vividly recalls the first time he saw the night sky at McDonald Observatory. “In a way, it’s like discovering the universe,” he said. Through the eyepiece of a telescope, he examined a cluster of ancient stars that astronomers have used to better understand how galaxies form.
“Not only is it there, but it was there when Newton was alive,” Dr. Muñoz said. “And it’ll be there when I’m gone. And we’ll get to understand the universe through it.”
The Los Angeles County Department of Public Health is investigating a confirmed measles case in a resident who recently traveled internationally, the agency said in a release Saturday.
This is the fifth measles case identified by the county this year as outbreaks increase across the U.S. and globally.
The infected resident arrived at the Los Angeles International Airport on Thursday on Alaska Airlines Flight 1354. Other travelers at Tom Bradley International Terminal B that day between 6 a.m. and 8 a.m. may have been exposed to the virus, officials said.
Public health officials are advising residents to check their immunization status and watch for symptoms if exposed. The measles-mumps-rubella vaccine is the most effective protection from measles, according to the public health department.
“As measles cases increase, it is important that residents take steps to make sure they are fully protected,” L.A. County Health Officer Muntu Davis said in a statement. “The MMR vaccine is the safest and most reliable way to prevent measles and protect yourself, your family, and your community.”
In coordination with the federal Centers for Disease Control and Prevention, L.A. County Public Health will notify travelers seated near the infected person on the flight.
Affected travelers are at risk of developing measles from seven to 21 days after exposure to the virus. Symptoms include rash, fever, cough and red, watery eyes.
Measles can lead to complications including pneumonia, brain swelling and even death. Those with symptoms should notify their healthcare facility before visiting, officials said.
So far this year, 1,814 measles cases have been confirmed nationwide, including 48 in California.
In January, health officials recorded the most amount of cases since the U.S. achieved elimination of the virus in 2000.
Archaeologists working in Egypt have discovered a remarkable combination of Homeric epic and Egyptian ritual: a 2,000-year-old mummy with a papyrus fragment of the “Iliad” sealed in a clay packet outside its wrappings.
It is the first time a literary work has been found playing a functional, spiritual role in the mummification process. And it suggests that for a Roman-era Egyptian, the “Iliad” — specifically some lines from Book 2’s “Catalogue of Ships” — was perhaps as crucial for navigating the afterlife as a magical spell.
“The find is incredibly significant, primarily for the discovery of such a papyrus with Greek literary text in its original context,” said Foy Scalf, an Egyptologist at the University of Chicago. “We have evidence that such Greek literary texts could be used as magical amulets and that Homer was frequently cited in such amulets, as well as in the large handbooks now known as ‘The Greco-Egyptian Formularies.’ The new find directly supports that indirect knowledge.”
The mummy, a nonroyal male, was unearthed by the Mission of the University of Barcelona at a burial site known as Oxyrhynchus, as part of a project directed by Ignasi-Xavier Adiego of the university’s Institute of Ancient Near East. Leah Mascia, a specialist in the written and material culture of Greco-Roman and Late Antique Egypt at the Free University of Berlin, coordinated the collaborative breakthrough that finally brought the damaged text to light.
Recognizing that the heavily degraded papyrus required careful analysis, Dr. Mascia worked with a conservator, Margalida Munar, to stabilize the artifact, and Dr. Adiego, an authority on the Carian language, to study the text. Together, their combined expertise in preservation and linguistics allowed them to identify and read the document.
After six years of painstakingly reconstructing tomb fragments, Dr. Mascia uncovered a rare moment of cultural alchemy: Roman Egypt, where foreign and local customs merged. Her analysis, which identified embalmer seals and folding patterns of the papyrus packet, suggests that classical Greek epics were not merely read but physically repurposed.
Traditionally, mummified bodies were buried with sepulchral texts like the “Book of the Dead” and “The Book of Breathing,” formulaic manuals intended to protect and guide the deceased through the underworld. Yet, by the early Roman period, a major shift emerged: the introduction of sealed papyrus packets placed upon the dead.
These new packets contained a surprising mix of texts, including Greco-Egyptian magic, documentary records and even literary works like the “Iliad,” indicating a personalized, alternative funerary practice.
Out of the dumps
The Oxyrhynchus necropolis, located near the modern village of El-Bahnasa about 120 miles south of Cairo, is not just a burial site but an archaeological mother lode. Located on the banks of the Bahr Yussef canal, the area is speckled with ancient garbage dumps that managed to preserve everything from wedding invitations and tax records to horoscopes and early Christian gospels.
The ruins of Oxyrhynchus were initially documented by Vivant Denon, a scholar during Napoleon’s 1798 Egyptian campaign. But they held a secret that remained buried for an additional century, until 1896, when British archaeologists dug up more than 400,000 fragments of papyri from the ancient trash heaps. The discoveries ultimately included lost masterworks by poets and playwrights like Sappho and Euripides, transforming millenniums-old refuse into a cornerstone of classical literature.
In the 1990s, the Mission of the University of Barcelona and the University of Cairo began a joint project largely funded by the Spanish Ministry of Culture and the Egyptian Ministry of Tourism and Antiquities. This ongoing mission, directed by Maite Mascort i Roca and Esther Pons Mellado and staffed by archaeologists, epigraphists and papyrologists, focuses on various sectors of the necropolis, including No. 22, where experts are reconstructing the elaborate social and religious life of residents during the transition from the Ptolemaic to the Roman era.
Researchers exploring the multichambered burial site have exhumed a remarkable trove of treasures, among them mummies adorned with golden tongues — gold foil placed over the mouth — and at least one with copper, ritualistic additions that may have ensured that the dead could confidently speak their case to Osiris, the god of death and resurrection, before judgment.
A separate, distinct area of the necropolis — Sector 42 — has yielded large jars containing cremated remains. One vessel held the bones of an adult, an infant and a feline, along with fabric fragments. While these individuals most likely date to a slightly different period from the “Iliad” mummy, the immense complexity of these rites implies a wealthy, status-conscious class, providing fresh insight into the spiritual anxieties of the Roman-era community.
A cultural passport
Recovered in December from Tomb 65, the fragmentary papyrus packet contains a passage from the 2,800-year-old “Iliad” that functions as a detailed inventory of the Achaean army’s naval strength and regional origins, describing the forces arrayed against Troy to retrieve Helen. The text mentions specific commanders, such as Guneus, who arrived with “two and twenty ships from Cyphus,” and Tlepolemus, a “son of Hercules” who brought nine ships from Rhodes.
Dr. Mascia’s findings reveal a deliberate, intimate act: a document prepared in a mummification workshop and placed directly upon the body of the deceased. “These sealed papyrus packets may have been regarded as part of an alternative funerary procedure,” she said, adding that further studies were essential to prove this hypothesis.
This spiritual first-aid follows a long tradition. Dr. Scalf noted that “The Greco-Egyptian Formularies” even suggests the “Iliad” doubled as a literal medical kit. For a bed-bound patient shivering with malaria, the prescription was simple: Brace your head against a papyrus scroll of Book 4 to break the fever.
For residents navigating the complex, vibrant crossroads of Roman Egypt, Greek literary papyri may have functioned as a crucial cultural passport, said Anna Dolganov, a historian at the Austrian Archaeological Institute. In Egypt, being Hellenic connoted an exclusive social status and financial privilege — and had to be meticulously documented through genealogies going back across several centuries.
Buried with the dead, the “Iliad” perhaps served as a cheat code for a more comfortable afterlife. Dr. Dolganov wonders if carrying the epic poem was a deliberate strategy to secure entry into the Greek underworld, effectively sidestepping the torturous trials of Egyptian mythology. For these individuals, a Hellenic identity wasn’t just for this world — it was an eternal upgrade, offering a smoother path and higher status in the great beyond.
Science
Ten times worse than benzene — California updates its science on two chemicals in everyday air
Two toxic contaminants present in California’s ambient air appear to be much stronger carcinogens than previously known, state environmental health officials announced Thursday.
The draft finding from the state’s Office of Environmental Health Hazard Assessment finds that acrolein and ethylene oxide may pose an estimated cancer risk more than 10 times higher than benzene, a serious carcinogen linked to leukemia and other cancers.
It is the first step in a review process before final risk values are adopted, and it arrives at a time federal air-quality regulations are being reined in.
“If the early air monitoring results bear out, and if the draft cancer values developed are close to what eventually becomes final, then each air contaminant poses an unacceptable cancer risk,” said Kris Thayer, OEHHA’s director.
The update reflects the state’s evolving understanding of its most dangerous pollutants, which has shifted over the decades from visible pollutants, such as smog, to more invisible ones that cause cancer, heart disease and other health harms.
It comes only two months after the Trump administration’s Environmental Protection Agency moved to roll back standards on ethylene oxide, or EtO, in an effort to save millions of dollars in compliance costs for facilities that use the chemical for medical sterilization. The administration said it acted to “safeguard the supply of essential medical equipment,” but experts said the move will also expose more people to health risks.
It also follows a new national report from the American Lung Assn. that found 82% of Californians live in counties with unhealthful air, nearly double the national average.
“This is an important step to better understanding the harms of pollutants impacting Californians’ health,” said Will Barrett, assistant vice president for nationwide clean air policy at the American Lung Assn., who reviewed the state’s findings for The Times. “Following the latest available health science to determine risk is crucial to protecting health.”
Ethylene oxide is a colorless gas often used in the sterilization of medical devices, particularly those that can’t be cleaned using steam or radiation.
Acrolein can be formed when materials burn, such as cigarettes, e-cigarettes and vapes, wood, plastics and gasoline for cars, trucks, ships and aircraft. It can also be released by cooking fats and oils at high temperatures, and has been found in water produced by oil and gas operations and is an ingredient in some pesticides used in irrigation canals.
People can take steps to protect themselves from acrolein exposure in everyday life by avoiding smoking tobacco or using e-cigarettes and vaping products, avoiding smoke from fires or exhaust from diesel and gasoline vehicles and equipment — much of which can also help reduce exposure to ethylene oxide, officials said. When cooking with oils or fats, people should avoid very high temperatures and use a range hood fan when possible.
While both chemicals have been present in the state’s air for years, the new assessments from OEHHA are based on the latest science on health risks, officials said. Both acrolein and ethylene oxide were found to pose an estimated cancer risk exceeding 800 in 1 million — on par with the cancer risk that diesel exhaust was estimated to pose when it first emerged as a major public health concern in the 1990s, the agency said.
In response to the findings, Gov. Gavin Newsom’s May budget revision, released Thursday, includes $2.5 million in funding for the California Air Resources Board and OEHHA in support of research to help reduce people’s exposure to acrolein and ethylene oxide. The funding will help the state identify and track major sources of the chemicals and turn the findings into public health policy outcomes, officials said.
OEHHA’s assessment provides the first cancer risk value for acrolein since it was classified as probably cancer-causing to humans by the International Agency for Research on Cancer in 2020. Ethylene oxide was already identified as a carcinogen by the state, but the new assessment updates its risk levels based on the new research. The risk calculations are based on air monitoring data, which vary across the state depending on location, nearby sources and other factors.
Officials said the findings underscore the state’s efforts to strengthen environmental protection measures for residents at a moment when federal officials seek to loosen them.
“Especially in light of some of the national rollbacks we’re seeing on protections for public health, it really underscores how important the work that we’re doing here in California is,” said Courtney Smith, principal deputy executive officer with the Air Resources Board. “Not only for protecting the health of Californians, but also to ensure that there is rigorous, solid science available to other entities as well who may want to pursue additional protections.”
Short-term exposure to EtO by inhalation can cause headaches, dizziness, nausea, fatigue respiratory irritation and other adverse health effects, according to the federal Agency for Toxic Substances and Disease Registry. Longer-term exposure increases the risk of cancers of the white blood cells, such as non-Hodgkin’s lymphoma, as well as breast cancer.
Inhaling acrolein can cause nose and throat irritation and a decreased breathing rate. Chronic exposure, such as through cigarette smoke, has been linked to the development of asthma, chronic obstructive pulmonary disease and respiratory cancers.
The findings also come as California continues to receive poor grades on air quality. The American Lung Assn. annual State of the Air report found that the five U.S. counties with the worst smog pollution are all in California. Bakersfield was the metropolitan area with the worst level of year-round particle pollution for the seventh year in a row, while Los Angeles was the city with the worst ozone pollution, as it has been for 26 of the last 27 years.
“Californians face the most significant smog and soot challenges in the nation, but our air agencies have followed the science to build policies and programs to make real headway,” Barrett said. The state’s latest assessment “speaks to the need for ongoing local efforts while the federal government ignores the science and opens the door for more pollution. California must continue to invest in things like cleaning up truck fleets, broader public education and the underlying science to guide policies to protect health.”
Thursday’s announcement kicks off a 45-day public comment period, after which the draft assessments may be revised before undergoing additional public comment, peer review by the state’s Scientific Review Panel on Toxic Air Contaminants, and eventual adoption.
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