Astronomers have turned their eye towards the future following the US National Academies’ latest decadal survey of astronomy and astrophysics, which recommended a new generation of space telescopes. Keith Cooper explores their prospects, and the lessons learned from the troubled development of the James Webb Space Telescope
Compare and contrast The Pillars of Creation as seen by the Hubble Space Telescope and the James Webb Space Telescope (JWST). On the left is Hubble’s iconic view, taken in visible light in 2014. On the right is the JWST’s new near-infrared view, released in October 2022. (Courtesy: NASA, ESA, CSA, STScI)
Christmas Day 2021 was a happy occasion for most astronomers around the world, as it was when the much-delayed James Webb Space Telescope (JWST) was finally launched. However, the fanfare surrounding its unfurling in space over the next month, as well as the subsequent jubilation over its first images, has masked a troubling problem in observational astronomy – which is that much of the rest of NASA’s fleet of space-based orbiting observatories is ageing. The Hubble Space Telescope has been working since 1990, while the Chandra X-ray Observatory was launched nearly a decade later. Meanwhile, their infrared compatriot, the Spitzer Space Telescope, launched in 2003, is no longer operating, having been shut down in 2020.
That’s why astronomers are worried that should something happen to one or more of these increasingly rickety telescopes, they could be cut off from whole swathes of the electromagnetic spectrum. With the shutdown of Spitzer, the far-infrared (160 μm) is already out of reach as the JWST only ventures into the mid-infrared at 26 μm. Similarly, the JWST is not optimized for observing visible or ultraviolet wavelengths like Hubble does. Sure, the forthcoming Nancy Grace Roman Space Telescope – formerly the Wide Field InfraRed Survey Telescope (WFIRST) – is an optical and near-infrared telescope, but its field of view is much wider than Hubble’s, meaning it is not geared for close-up, detailed work; nor does it have Hubble’s ultraviolet coverage.
Great observatories
To ensure our view of the universe across the spectrum remains bright, US astronomers are currently picking and choosing the next cohort of space telescopes. The prime recommendation of the latest astronomical decadal survey from the US National Academies of Sciences, Engineering and Medicine – the 614-page report Pathways to Discovery in Astronomy and Astrophysics for the 2020s (Astro2020) – is for plans to be put in place for a new generation of “great observatories” to begin launching in the 2040s. This echoes when Chandra, Hubble, Spitzer and the Compton Gamma-Ray Observatory (which operated between 1991 and 2000 and was succeeded in 2008 by the Fermi Space Telescope) were being developed, and which were heralded as the “great observatories”.
Working alongside each other to study the universe, these telescopes have spearheaded NASA’s astrophysics research for decades. The reuse of this phrase “great observatories” in the new decadal survey is deliberate, says the survey’s co-chair, Fiona Harrison of the California Institute of Technology. “It’s to get across the point that panchromatic observations, from X-rays to infrared, are really essential for modern astrophysics,” she says. “A lot of the success of the [original] great observatories is that they were developed and launched one after the other, with overlapping observations.”
Building a successful space telescope is a long process, typically taking 25 years from the start of development to launch. Concept work for Hubble began in the 1960s, while plans for the JWST first came together in 1995, after the Hubble Deep Field images showed that the first galaxies are within reach of a larger telescope. The next generation of such space-based probes therefore won’t launch until the 2040s, at the earliest. But they will include the survey’s number one recommendation: a flagship mission to replace Hubble, drawing inspiration from two concepts – the Habitable Exoplanet Observatory (HabEx) and the Large UltraViolet, Optical and InfraRed (LUVOIR) telescope. Also on the drawing board are an X-ray mission and a telescope that can observe in the far-infrared.
Flagship missions Costs and timescales of past, current and future NASA missions. Cost is at launch, i.e. does not include servicing missions. Development timescale indicates time from survey recommendation to launch. For future missions, the estimated cost is a minimum, assuming immediate start and optimum budget profile. (Data taken from the NASA Astro2020 decadal survey)
But given the precarious health of our current crop of space telescopes, and knowing the new missions won’t launch for another 20 years, shouldn’t astronomers have started planning for new great observatories years ago? “For sure,” says Steven Kahn of Stanford University, who chaired one of the panels in the decadal survey looking at future space telescopes. He cites the Constellation-X observatory – an X-ray space probe that was recommended as a follow-up to Chandra in the 2000 decadal survey, but never came to fruition because of the drawn-out development of the JWST, which sucked up all the astrophysics budget. “The JWST basically dominated the great observatory programme at NASA for two-and-a-half decades,” explains Kahn. “As a result, there wasn’t room to do a follow-on X-ray mission, or the kind of pioneering far-infrared mission that we’re envisaging.”
Winner takes it all
Indeed, the JWST’s development saw many issues, including huge overruns in cost and development time, which almost saw the project cancelled. The memory of these mistakes looms large over the new decadal survey, influencing some of the recommendations made to restore balance to astrophysics in the US. But it wasn’t always like this. Kahn laments how, prior to the 2000 survey, just getting on the list of recommendations in a decadal survey was enough to virtually guarantee that your project or mission would happen. But in the modern era of $10bn telescopes, “you have to be number one or you’re not going to get it done” says Kahn. “The problem is that in this winner-takes-all environment, everybody wants to throw all the bells and whistles they can onto a project because if you think you’re only going to get one shot at a big mission in the next 50 years, you want to make it count.”
It’s this way of thinking that can lead to the problems the JWST both faced and caused. The more complex a mission design becomes, the more instruments and capability that you want it to have to make it worthwhile – which means that it grows more expensive and takes longer to develop. “All of which gets us back into this vicious cycle of winner takes all,” continues Kahn.
Harrison agrees, emphasizing that this new decadal survey is an attempt to try and change US astronomy’s approach. “For a decadal survey to say, this is the number-one thing, we need to do it no matter what, at whatever cost it ends up being, is not a responsible approach,” she says. In an attempt to counter this, the recent survey makes a number of new proposals. Among them is the idea that missions should be designed in tune with specific science priorities, rather than allowing the mission concept to run away with itself, with all the “bells and whistles”, to quote Kahn.
Out with the old The NASA decadal survey concluded that neither the Lynx X-ray Observatory (left) nor the Origins Space Telescope (right) fit the requirements that the panel was looking for. (Courtesy: NASA)
For example, one of the key science questions that Kahn’s panel looked at was the way in which active supermassive black holes in distant, dusty galaxies influence star formation. The accretion of matter onto such black holes would be detectable to a high-angular-resolution X-ray telescope, while a far-infrared spectroscopic mission would be able to peer through the dust and probe specific spectral lines related to star formation and feedback from black-hole winds. The hope is that the two missions could be launched within a few years of one another, and operate in unison. However, what shape those missions will take is still up in the air.
Prior to the decadal survey there were two mission concepts – the Lynx X-ray Observatory and the Origins Space Telescope – that would operate at mid- to far-infrared wavelengths, with a telescope mirror between 6 and 9 m in diameter. Each was estimated to cost about $5bn, but the decadal survey concluded that these costs were being underestimated and that their science capabilities didn’t quite fit into the requirements that the panel was looking for.
Flagship missions
And here enters one of the decadal survey’s other innovations – namely, a new class of space telescope referred to as “probe-class”, with budgets of a few billion dollars. “We have to acknowledge that if things were all going to be as expensive as JWST, it would be difficult to have all the great observatories operating at the same time,” says Marcia Rieke of the University of Arizona, who led the second panel on space telescopes, focusing on the optical and near-infrared regime. “The best way instead might be to have one flagship mission, and then have the other parts of the electromagnetic spectrum covered by probe missions.”
Indeed, any possible X-ray and far-infrared probe-class missions could also be joined by a probe-class ultraviolet telescope. Improvements in mirror coatings and detectors over the last few decades mean that a 1.5 m telescope could actually be more sensitive than Hubble at ultraviolet wavelengths. “That would provide some robustness against Hubble out-and-out failing,” says Rieke.
Projected plan Timeline for the medium and large programmes and projects recommended by the Astro2020 decadal survey. The location of the logos shows the projected start of science operations for a range of missions and observatories – from space- and ground-based observatories across the spectrum, to multimessenger probes as well as telescopes to study key phenomena such as exoplanets and the cosmic microwave background – or the start date of the programme. The survey has three broad science themes, each of which requires a range of facilities and programmes. (Adapted from original by NASA)
To help develop these future space telescopes, whether they proceed as $10bn behemoths or go forward as more modest (but still ambitious) probe missions, the decadal survey recommends that NASA creates a new Great Observatories Mission and Technology Maturation Programme. It would not just develop the technology, but also “mature the mission concepts”, says Harrison. For its part, NASA is already holding workshops as part of this new programme and has produced a draft call for probe missions.
If the X-ray and far-infrared missions – nicknamed “Fire” and “Smoke” for now – are to be probe-class, then the flagship great observatory will be the long-awaited direct replacement for the Hubble Space Telescope. The concept that leads the way is LUVOIR, and two versions of the telescope have been proposed: either a wildly ambitious 15 m telescope, or an 8 m telescope, the latter of which would still be the largest space telescope ever launched.
Other Earths
For cost and practicality reasons, the decadal survey recommended that the 15 m version fall by the wayside, and that the final design meld the best parts of both LUVOIR and HabEx. The key science goal of this telescope, explains Rieke, is that it has to be able to detect Earth-mass planets in the habitable zone of stars. To that end, Rieke’s panel engaged in a discussion with the exoplanet community about how many potentially habitable planets could be detected as a function of the size of the telescope.
Just the one The original 15 m design (A) for the LUVOIR (Large UV/Optical/IR Surveyor) observatory. The Astro2020 decadal survey recommends combining the LUVOIR and HabEx concepts into a single large telescope. (Courtesy: NASA GSFC)
“As a group, you ask: what are the key science goals? What level of sensitivity is needed? What’s the smallest telescope that will do the job?” says Rieke. The answer she got back was that a 6–8 m-aperture telescope is about as small as you dare go if you want to find potentially habitable exoplanets.
Success isn’t just about the size of the telescope though; its instruments have to be up to scratch too. Successfully imaging Earth-sized planets close to their stars will require a coronagraph as part of its design. Exoplanets the size of Earth normally cannot be imaged because the glare of their star is too overpowering. A coronagraph blocks the light of the star, making it easier to see any planets in attendance. They have been a staple of studies of the Sun for decades – their name comes from blocking the Sun’s disc so astronomers can see the solar corona. But devising a coronagraph that can precisely block the bright light of a star, which appears as essentially a point source, while allowing planets just milliarcseconds from the star to be visible by reducing the contrast between the star’s glare and the planets’ light to 10–10, is “quite a step beyond anything that we’ve done before”, says Rieke.
Beyond space, telescopes on the ground
Earth-bound Artist’s concept of the completed Giant Magellan Telescope which will be situated in the Atacama Desert, Chile. (Courtesy: GMTO Corporation)
Not all of the decadal survey’s recommendations are related to giant telescopes in space. Indeed, some of them are giant telescopes firmly rooted on Earth. For example, the controversial Thirty Meter Telescope to be built on Mauna Kea in Hawaii, despite the protests of some native Hawaiians, continues to move forward. So too is the Grand Magellan Telescope, which is under construction in Chile and will feature seven 8.4 m telescopes to give an effective diameter of 24.5 m.
The survey also recommends that the Next Generation Very Large Array – 244 radio dishes of 18 m diameter and 19 dishes of 6 m diameter spread across the US south-west – should start being built by the end of the decade. It will replace the ageing Very Large Array in New Mexico and the Very Long Baseline Array of dishes across the US. Upgrades to the Large Interferometer Gravitational-wave Observatory (LIGO) and plans for an eventual successor are also recommended.
Meanwhile, cosmologists will be heartened to hear that the survey also calls for a new ground-based observatory, dubbed the CMB Stage 4 observatory, to detect polarization in the cosmic microwave background radiation to search for evidence of primordial gravitational waves that resulted from cosmic inflation in the earliest moments of the universe.
Finally, back in space, the highest priority for medium-scale missions is a fast-response time-domain and multimessenger programme to replace NASA’s Swift spacecraft and detect supernovae, gamma-ray bursts, kilonovae and various other kinds of astronomical transients. Crucially, the missions in this new programme need to be able to work with and support the ground-based observations of LIGO, the Cherenkov Telescope Array and the IceCube neutrino detector, for which a “Generation 2” detector has also been recommended.
The next step is to convince politicians to part with the funds that will be needed to make the great observatories possible
Fiona Harrison, California Institute of Technology
“Certainly a focus now for myself and Robert Kennicutt [Harrison’s fellow co-chair from the University of Arizona and Texas A&M University] is to try and articulate to Congress the excitement of the compelling projects recommended by the survey,” she says. “It was a positive response from NASA, and it wants to make the recommendations happen, but the budget has to be there.”
Should that money be forthcoming, then Rieke estimates the funding required to mature the technology for the optical telescope to be about half a billion dollars. “We would then be poised, near the end of this decade, to have all the technology ducks sitting in a row and we’ll be able to enter the construction phase,” she says.
The timescales involved are phenomenal. If Hubble and Chandra are anything to go by, the next-generation telescopes launched in the 2040s could still be operational in the 2070s or beyond. The decadal survey’s recommendations are therefore not just important for the next 10 years of astronomy, but for their impact on much of this century. There was therefore tremendous pressure on the survey to have got it right.
“That’s where it’s important to pick ambitious goals,” says Rieke. “You have to identify something that’s so important that everyone agrees, and is enough of a step forward that something else isn’t going to overtake you while you’re doing it.” History will judge whether this decadal survey got its key decisions correct, but from today’s perspective, the future of astrophysics promises to be an exciting one.
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.”
