NASA’s TESS, or Transiting Exoplanet Survey Satellite has one main job: finding exoplanets. But it’s also helping astronomers study a strange type of star that has so far defied thorough explanation. Those stars are Delta Scuti stars, named after their prototype.
Delta Scuti stars exhibit strange pulsating patterns, and they rotate rapidly. So far, astronomers haven’t been able to figure out whey they pulsate the way they do. But a new study based on TESS data is revealing some of the detail of these puzzling stars, if not explaining them completely.
“This really is a breakthrough. … But it’s also shown us that this is just a stepping-stone in our understanding of Delta Scuti stars.”
Simon Murphy, Co-Author, University of Sydney
TESS watches stars and looks for planets that transit in front of them. Those transits create dips in the starlight. To do that, it monitors huge patches of the sky, and all the stars in them, for 27-day periods. Those long observation times were helpful in this new study, even though it’s not focused on exoplanets, but on Delta Scuti stars.
Delta Scuti stars are larger than the Sun, about 1.5 to 2.5 times larger. Their namesake, the star Delta Scuti, was identified as a variable star back in 1900. Now astronomers know of thousands of them, many of which were discovered with NASA’s other planet-hunter, the Kepler spacecraft.
Delta Scutis are puzzling, compared to other variable stars. They rotate much faster than other stars, once or twice a day, which is at least a dozen times faster than our Sun. Because they rotate so fast, the stars are flattened at the poles, and the patterns of pulsation are scrambled. They’re complicated stars, and challenging to understand.
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“Delta Scuti stars clearly pulsate in interesting ways, but the patterns of those pulsations have so far defied understanding,” said Tim Bedding in a press release. “To use a musical analogy, many stars pulsate along simple chords, but Delta Scuti stars are complex, with notes that seem to be jumbled. TESS has shown us that’s not true for all of them.”
TESS, and its 27-day observations of many stars at a time, is just what Bedding and his team needed. TESS’s observing power means that astronomers can monitor many stars at once. TESS has four cameras, and in its normal mode, it captures and image with each of the four every thirty minutes. But those 30 minute exposures are too long to capture changes in Delta Scuti stars, which are variable every few minutes.
Fortunately, TESS also captures two-minute exposures of thousands of pre-selected stars. And some of those stars are Delta Scuti stars. Bedding and his team dug through TESS data, and they found a sub-set of Delta Scuti stars that have regular pulsation patterns. With that data in hand, they knew what to look for.
They then combed through Kepler data, and did follow-up observations with ground telescopes like the Keck. In the end, Bedding and the other astronomers found 60 Delta Scuti stars that had regular pulsation patterns. In their paper they write, “We discovered 60 stars with regular frequency spacings, which define a group of ? Scuti stars for which mode identification is possible.”
“This really is a breakthrough. Now we have a regular series of pulsations for these stars that we can understand and compare with models,” said co-author Simon Murphy, a postdoctoral researcher at the University of Sydney. “It’s going to allow us to measure these stars using asteroseismology in a way that we’ve never been able to do. But it’s also shown us that this is just a stepping-stone in our understanding of Delta Scuti stars.”
“Nearly all the physical processes that determine the structure and evolution of stars occur in their (deep) interiors.”
Gerald Hanlder, Copernicus Astronomical Center
Asteroseismology is the study of the internal structure of stars, based on a star’s oscillations. The idea is to determine the interior structure of stars by using their oscillations as seismic waves. Asteroseismology is a quickly-evolving field. In a 2012 paper discussing asteroseismology, Gerald Handler of the Copernicus Astronomical Center said, “Nearly all the physical processes that determine the structure and evolution of stars occur in their (deep) interiors. The production of nuclear energy that powers stars takes place in their cores for most of their lifetime.” In short, the interior of stars is where the business takes place, and asteroseismology is one method of investigating it.
As the team writes in their paper, “Asteroseismology probes the internal structures of stars by using their natural pulsation frequencies. It relies on identifying sequences of pulsation modes that can be compared with theoretical models, which has been done successfully for many classes of pulsators, including low-mass solar-type stars, red giants, high-mass stars and white dwarfs.” However, up until now, Delta Scuti stars have resisted efforts to understand their asteroseismology. That’s largely because they rotate so rapidly.
“We knew when we designed TESS that, in addition to finding many exciting new exoplanets, the satellite would also advance the field of asteroseismology.”
TESS Principal Investigator George Ricker, Massachusetts Institute of Technology.
Sound waves bouncing around inside a star cause it to expand and contract, which results in detectable brightness changes. This animation depicts one type of Delta Scuti pulsation — called a radial mode — that is driven by waves (blue arrows) traveling between the star’s core and surface. In reality, a star may pulsate in many different modes, creating complicated patterns that enable scientists to learn about its interior. Credits: NASA’s Goddard Space Flight Center
The team of researchers found that their Delta Scuti stars fell into two groups, and both types involve the build-up and then release of energy. In the first group, the entire star expands and contracts symmetrically. In the second group, opposite hemispheres of the star expand and contract alternately.
“Being able to find simple patterns and identify the modes of oscillation is game changing.”
Sarbani Basue, Professor of Astronomy, Yale University.
“Delta Scuti stars have been frustrating targets because of their complicated oscillations, so this is a very exciting discovery,” said Sarbani Basu, a professor of astronomy at Yale University in New Haven, Connecticut, who studies asteroseismology but was not involved in the study. “Being able to find simple patterns and identify the modes of oscillation is game changing. Since this subset of stars allows normal seismic analyses, we will finally be able to characterize them properly.”
In fact, the team’s data has already helped understand one puzzling star, and the stream of stars it belongs to.
Recently, astronomers discovered a stream of stars orbiting within the Milky Way. Scientists have debated the age of the stream, with some pinning it at about one billion years. That one billion year number was based on a red giant star in the stream. But other, later measurements of the stream showed that the stars are only about 120 million years old, a major discrepancy.
The team behind this study used the models they developed for Delta Scuti stars to examine a single star in the stream named HD 31901. Their new asteroseismological model confirmed HD 31901’s younger age, and showed that the earlier one billion year age is incorrect.
Their work is already paying off.
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According to the team, it’s the age of their sub-set of 60 Delta Scuti stars that’s responsible for the regular pulsation patterns. They’re younger than the others, and so they’ve only recently, in stellar terms, settled down to producing their fusion in only their cores. In these younger stars, the pulsations are more rapid.
But as the stars age, things get a little more complicated. The frequency of the pulstations slows, and the signal gets mixed up with signals coming from the star. Because HD 31901 had a clear, rapid pulsation pattern, it was confirmed as being relative young, settling the debate.
But as it turns out, studying Delta Scuit stars is not totally straight-forward. TESS’s viewing angle of the stars can lead to different measurements. When viewed pole-on, these stars may exhibit more regular pulsation patterns than when viewed at the equator, according to theoretical calculations. With over 1,000 Delta Scuti stars in the data, some of them are bound to be seen at their poles.
TESS observes the sky in 26 different sectors. Most of them will be observed for 27 day periods. Image Credit: By NASA – https://tess.gsfc.nasa.gov/images/tess_science_image3.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=64875510
The team will continue to work on their Delta Scuti models. Soon, TESS will switch from capturing 30 minute images to 10 minute images. That’ll happen in July, when TESS switches from its initial mission to its extended mission, and it should help the team find even more Delta Scutis.
Due to the way that TESS works, the people behind it knew that it would help advance the science of asteroseismology, even though that’s not the spacecraft’s primary mission.
“We knew when we designed TESS that, in addition to finding many exciting new exoplanets, the satellite would also advance the field of asteroseismology,” said TESS Principal Investigator George Ricker at the Massachusetts Institute of Technology’s Kavli Institute for Astrophysics and Space Research in Cambridge. “The mission has already found a new type of star that pulsates on one side only and has unearthed new facts about well-known stars. As we complete the initial two-year mission and commence the extended mission, we’re looking forward to a wealth of new stellar discoveries TESS will make.”
More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.
That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.
“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”
The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.
Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.
Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.
Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.
Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.
Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.
“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”
The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.
North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.
Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”
Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.
Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.
For Dello, the “fingerprints of climate change” were clear.
“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”
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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.
On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.
They call it “Big Sam.”
The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.
It didn’t die alone.
“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.
She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”
“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.
The head alone, she said, is about the size of a baby elephant.
The discovery was a long time coming.
The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.
“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.
When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”
“It contains about 100 to 300 bones per square metre,” she said.
Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.
About a year ago, they found the second adult: Big Sam.
Bamforth said both dinosaurs are believed to have been the elders in the herd.
“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.
“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”
The genders of the two adults are unknown.
Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.
The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.
She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.
“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.
“It’s pretty exciting.”
This report by The Canadian Press was first published Sept. 25, 2024.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
