Tag Archives: arecibo

The first indirect detection of gravitational waves: the road to LIGO

Gravitational waves are disturbances in space-time generated by some of the largest and most energetic events in the universe. They propagate as waves from a source at the speed of light.

Artistic depiction of gravitational waves. Image credits: Charly W. Karl.

In Einstein’s general theory of relativity, gravity is considered a curvature of spacetime — a curvature caused by the presence of mass. The larger and more compact the mass is, the greater the curvature. For physicists, gravitational waves are also the wave-like solution of Einstein’s equations and the only way through which some phenomena in the universe can be observed.

For instance, when the orbits of two massive bodies change over time, this seemingly results in a loss of energy. But energy can’t be lost, so it must go somewhere — and the only way to explain that loss is that the energy is used to produce waves in space-time, emitting gravitational radiation.

The theory lined up well, but there was a problem: for decades, researchers couldn’t truly detect these gravitational waves, and without validation, the theory couldn’t be confirmed. That all changed in 2015, with the first gravitational waves (GW150914) being directly observed by the two Laser Interferometer Gravitational Wave Observatory (LIGO) detectors. Three years later, the three main scientists behind the detection received the Nobel Prize for the discovery. But researchers may have discovered gravitational waves way earlier, in 1982.

Hulse–Taylor binary

This image shows pulsed gamma rays from the Vela pulsar as constructed from photons detected by Fermi’s Large Area Telescope. Credits: Goddard Space Flight Center.

In 1974, two astrophysicists, (Russell Alan Hulse and Joseph Hooton Taylor Jr) were carrying out a pulsar survey at the Arecibo Observatory, a radio telescope with a 305 meter (1,000 ft) dome. You may remember Arecibo as that big telescope that collapsed to rubble in late 2020 due to underfunding and neglect. Pulsars are a type of compact stars that emit radio or X-ray radiation — they’re a sort of cosmic lighthouse that spins, and whenever it emits a signal towards the Earth, we can detect.

There’s an important reason why Arecibo was so big. The goal of radio telescopes is to detect radio waves — waves for which the wavelength can measure even more than the Earth’s radius. The sources of radio waves outside the solar system are really weak, so we need very big dishes to detect those objects — and Arecibo successfully detected something.

The scientists detected a ‘weird’ pulsar, later named PSR B1913+16 or the “Hulse-Taylor binary”. Researchers noticed that the pulsation period of this pulsar is not stable — it changes and returns to the original state every 7.75 hours. The only explanation for that change was that the pulsar is in a binary system, the pulsar was completing an orbit every 7.75 hours. They knew that thanks to the Doppler effect.

When a light source is moving away from us, its frequency is shifted to the red side of the visible spectrum — and when it moves towards us it is shifted to blue. By measuring the pulsar period, Taylor and Hulse were able to plot a velocity curve to help analyze the orbit and try to figure out who was the pulsar’s companion.

Two stars of different sizes orbiting the same center of mass. The spectrum can be seen to split depending on the position and velocity of the stars. The shift of Star A is greater than that of Star B because the tangential velocity is higher. The line width of Star B is greater than that of Star A because Star B is larger and more luminous. Wikimedia Commons

In their analysis, they observed that system does not have a circular orbit but an ellipse. In the end, they concluded the pulsar lived in a binary system with another compact star, but they could yet not conclude if it was also pulsar or not.

Gravitational waves

By now, you’re probably wondering what this all has to do with gravitational waves. We’re almost there.

Eight years later, without stopping the observations, Taylor and Joel M. Weisberg realized the orbital velocity was increasing, meaning the stars were accelerating. They had also improved their knowledge of the system and figured that both stars have nearly the same mass of 1.4 solar masses and that their orbit is tight, around 4.5 times the Sun’s radius (or 9 times the distance from the Earth to the Moon). The pulsar’s companion is probably another pulsar, they concluded, but we just cannot get its radio signal because the beams it emits are never pointed towards Earth.

The binary was the perfect candidate to test the gravitational waves solution to Einstein’s equations, but because we couldn’t get direct information from the waves themselves, Taylor and Weisberg used theory to indirectly connect the observations from the pulse’s period. They noticed that the orbital period between the stars was decreasing with time, which means it was losing energy — presumably to gravitational waves.

While Arecibo was still working, the observations continued, and 30 years later, the same theory continued to fit the estimated loss of the orbital period, hinting more and more that the binary is emitting gravitational waves. The jaw-dropping conclusion of the study is the almost perfect agreement between the points (in red below) and the theory (blue line) almost as if there isn’t a minimal mistake in Einstein’s theory. Although they didn’t have any direct observation, astronomers had most likely detected gravitational waves indirectly.

Orbital decay of PSR B1913+16.The data points indicate the observed change in the epoch of periastron with date while the parabola illustrates the theoretically expected change in epoch according to general relativity.

The discovery of the binary pulsar resulted in a Nobel prize in 1993 for Taylor and Hulse, but not for the gravitational waves indirect detection. PSR1913+16 has always been the observation that paved the way for the gravitational waves interferometer, with the binary it was almost certain that the theory was correct, scientists just needed to be lucky enough to observe the phenomenon. It happened and in 2017, the Nobel prize in physics was awarded to LIGO researchers for the first solid detection.

The Arecibo Observatory in Puerto Rico. Credit: NAIC Arecibo Observatory, a facility of the NSF

The Arecibo radio telescope collapsed a year ago. The iconic telescope that made the first detection of binary pulsars, and many others, fell to rubble as it struggled to obtain funding in recent years. The data collected by the telescope is still used by scientists, the most recent was published exactly one year after its collapse, the research tries to understand the history of galaxies with their stellar mass.

2020: A Year in Space

It’s difficult to mention the year 2020 without referencing COVID-19, but as more human beings than ever before were wishing they could take a break from the surface of the planet, space research continued to push our knowledge of the stars. Whilst much of the scientific community was consumed with combating a pandemic, physicists, astronomers, cosmologists, and other researchers were further pushing our understanding of space and the objects which dwell there.

These are some of my personal favourite space-related breakthroughs and research that have come about this year. The list is by no means exhaustive. 

Black Holes go silent

In terms of black hole science, 2019 was always going to be a difficult year to top being the year that brought us the first direct image of a supermassive black hole (SMBH). That doesn’t mean that 2020 has been a slow year for black hole developments, however.

One of the most striking and memorable examples of black hole research announced this year was the discovery of a ‘silent’ black hole in our cosmic ‘back yard.’ An international team led by researchers from European Southern Observatory (ESO) including found the black hole in the system HR 6819, located within the Milky Way and just 1,000 light-years from the Earth.

A silent and thus invisible black hole discovered lurking in our ‘solar backyard’ could be an indicator of a much larger population. (ESO/L. Calçada) Background: This wide-field view shows the region of the sky, in the constellation of Telescopium, where HR 6819 can be found. (ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin)

The observation marks the closest to Earth a black hole has ever been discovered and Dietrich Baade, Emeritus Astronomer at ESO in Garching believes that it is just ‘the tip of the Iceberg’. 

“It’s remarkable because not only is it the first of its kind found, but it’s also so nearby,” said Baade. “Discovering a first only an astronomical stone’s throw away is the biggest surprise one can probably imagine.”

The black hole was described as ‘silent’ by the team because it is not current accreting material — the destructive process that creates powerful x-ray emissions and makes these light-trapping objects observable. 

Close-up screen capture image of the LB-1 which, like HR 6819, could also host a silent black hole (Hubble/Public Domain)

“If there is one, there ‘must’ be more,” Baade remarked in May. “If the Earth is not in a privileged position in the Universe — and all available evidence suggests without a doubt it is not — this means that there must be many more silent black holes.”

Baade also remarked that as current cosmological models suggest that the number of stellar-mass black holes is between 100,000,000 to 1,000,000,000 and we have observed nowhere near this many objects, more quiet black holes are “badly needed” to confirm current models. “HR 6819 is the tip of an iceberg, we do not yet know how big the iceberg is.”

Silent black holes weren’t the only examples of this hind of science making noise in 2020, however. Long-missing Intermediate Mass Black Holes were discovered. And just like a proverbial bus, you wait decades for one and then two turn up at once.

Intermediate mass black holes found and found again

Missing black holes were the subject of another piece of exciting space science in September 2020, when researchers from the VIRGO/LIGO collaboration discovered the tell-tale signal of an intermediate-mass black hole (IMBH) in gravitational-wave signals. To add to the excitement, the signals originated from the largest black hole merger ever observed.

An artistic interpretation of the binary black hole merger responsible for GW190521. The space-time, figured by a fabric on which a view of the cosmos is printed, is distorted by the GW190521 signal. The turquoise and orange mini-grids represent the dragging effects due to the individually rotating black holes. The estimated spin axes, or self-rotations, of the black holes, are indicated with the corresponding coloured arrows. The background suggests a star cluster, one of the possible environments where GW190521 could have occurred. Credits: Raúl Rubio / Virgo Valencia Group / The Virgo Collaboration.)

The merger — identified as gravitational wave event GW190521 —was detected in gravitational waves and is the first example of a ‘hierarchical merger’ occurring between two black holes of different sizes, one of which was born from a previous merger.

“This doesn’t look much like a chirp, which is what we typically detect,” Virgo member Nelson Christensen, a researcher at the French National Centre for Scientific Research (CNRS) said when announcing the team’s observation. “This is more like something that goes ‘bang,’ and it’s the most massive signal LIGO and Virgo have seen.”

The black hole birthed in the detected merger appears to have a mass of between 100–1000 times that of the Sun — most likely 142 solar masses — putting it in the mass range of an IMBH — a ‘missing link’ between stellar-mass black holes and much larger SMBHs. 

Earlier in 2020, another team had used the Hubble Space Telescope X-ray data collected in 2018 to identify what they believed to be an IMBH with a mass 50,000 times that of the Sun named 3XMM J215022.4−055108 (or J2150−0551 for short). 

This Hubble Space Telescope image identified the location of an intermediate-mass black hole (IMBH), weighing over 50 000 times the mass of our Sun (NASA, ESA, and D. Lin (University of New Hampshire))

Whether GW190521 or J2150−0551 will go down in history as the first discovered IMBH is currently a little muddy, but what is less questionable is that 2020 will go down as the year in which these ‘missing link’ black holes were first discovered, bringing with them exciting implications for the future investigation of black holes of all sizes. 

“Studying the origin and evolution of the intermediate-mass black holes will finally give an answer as to how the supermassive black holes that we find in the centres of massive galaxies came to exist,” said Natalie Webb of the Université de Toulouse in France, part of the team that found J2150−0551. And IMBHs weren’t the only missing element of the Universe that turned up in 2020.

Discovering the Universe’s missing mass

In May astronomers, including Professor J. Xavier Prochaska of UC Santa Cruz, announced that they had found the missing half of missing baryonic matter demanded by cosmological models. 

“The matter in this study is ‘ordinary’ matter — the material that makes up our bodies, the Earth, and the entirety of the periodic table. We refer to this matter as ‘baryonic’–matter made up of baryons like electron and protons,” Prochaska said when he spoke exclusively to ZME Science earlier this year. “Of particular interest to astronomers is to ascertain the fraction of the material that is tightly bound to galaxies versus the fraction that is out in the open Universe — what we refer to as the intergalactic medium or cosmic web.”

The matter the team discovered isn’t ‘dark matter’ — which accounts for roughly 85–90% of the Universe’s matter content — but rather ‘ordinary’ matter that has been predicted to exist by our models of universal evolution but has remained hidden.

The team made the discovery using mysterious Fast Radio Bursts (FRBs) and the measurement of the redshift of the galaxy from which they originate as a detection method. FRBs can be used as a probe for baryonic matter because as they travel across the Universe, every atom they encounter slows them down by a tiny amount.

This means that they carry with them a trace of these encounters along with them in the spectral splitting as seen above. This allowed the team to infer the presence of clouds of ionised gas that are invisible to ‘ordinary’ astronomy because of how diffuse they are. 

Asteroid Samples Returned by Hayabusa2

Japan’s Hayabusa2 probe and its continued investigation of the asteroid Ryugu has been the gift that has just kept giving in 2020. Just this month the probe returned to Earth samples collected from an asteroid — which has an orbit that brings it between Earth and Mars — for the first time.

Though probes have landed on asteroids and collected samples before, these samples have been examined in situ. Thus this is the first time researchers have been able to get ‘up close and personal’ with matter from an asteroid.

Artist’s impression of the Hayabusa2 probe achieving touchdown on Ryugu. Image credit: JAXA

Hayabusa2 arrived at Ryugu in late June 2018, making its touch-down on the surface of the asteroid in February of the following year after months careful manoeuvring conducted by the Japan Aerospace Exploration Agency (JAXA) and the selection of an optimal region from which to collect samples. 

Ahead of the return of samples on December 5th, the probe sent back some stunning images of the asteroid’s surface. These images were more than purely aesthetic, however. Examination of dust grains on the surface of Ryugu gave the team, including Tomokatsu Morota, Nagoya University, Japan, indications of a period of rapid heating by the Sun. 

The surface of near-Earth carbonaceous asteroid 162173 Ryugu, as observed by the Hayabusa2 spacecraft just before its landing. This image was produced from images obtained by ONC-W1 at the bottom and ONC-W2 on the side of the spacecraft. The spacecraft’s solar ray paddle casts a shadow on Ryugu’s surface. Image credit: JAXA/U. Tokyo/Kochi U./Rikkyo U./Nagoya U./Chiba Inst. Tech./Meiji U./U. Aizu/AIST

“Our results suggest that Ryugu underwent an orbital excursion near the
Sun,” said Morota in May. “This constrains the orbital transition processes of asteroids from the main belt to near-Earth orbit.”

Impressive though this achievement is, its the collection of samples from the asteroid and their subsequent safe return to earth that is the ‘main course’ of the Hayabusa2 mission. “The most important objective of the touchdown is sample collection from Ryugu’s surface,” Morota explained. 

Animation created from CAM-H and ONC-W1 data obtained during the 1st touchdown operation (Feb. 21, 2019). Image credit: JAXA/U. Tokyo/Kochi U./Rikkyo U./Nagoya U./Chiba Inst. Tech./Meiji U./U. Aizu/AIST

It is hoped that access to these samples will help answer lingering questions about asteroid composition as well as assisting researchers to confirm Ryugu’s suspected age of 100 million years old — which actually makes it quite young in terms of other asteroids. 

Asteroids like Ryugu can act as a ‘snapshot’ of the system’s in which they form at the time of that formation. This is because whereas planets undergo a lot of interaction with other bodies, asteroids remain pretty much untouched. 

Whilst researchers will no doubt be elated by the return of the Ryugu samples and the continuing success of the Hayabusa2 mission, 2020 wasn’t all good news for fans of asteroid research. 

Goodbye to Arecibo

The iconic radio telescope at the Arecibo Observatory in Puerto Rico collapsed at the beginning of December, ahead of its planned demolition. The telescope which will be familiar to moviegoers as the setting of the climactic battle in Pierce Brosnan’s first outing as James Bond, 1995’s Goldeneye, had been in operation up until November, playing a role in the detection of near-Earth asteroids and monitoring if they present a threat to the planet.

An image of the radio telescope before its December 1st collapse (NSF)

The collapse of the radio telescope’s 900-tonne platform which was suspended above the telescope’s 305-metre-wide dish, on December 1st, followed the snapping of one of its main cables in November.

The US National Science Foundation (NSF), which operates the observatory had announced that same month that the telescope would be permanently closed citing ‘safety concerns’ after warnings from engineers that it could collapse at any point.

Following the collapse, the NSF release heart-wrenching footage of the radio telescope collapsing recorded by drones. The footage shows cables snapping at the top of one of the three towers from which the instrument platform was suspended. The platform then plummets downward impacting the side of the dish. 

Video shows the radio telescope’s instrument platform fall and collision into the side of the dish (NSF)

The observatory had played a role in several major space-science breakthroughs since its construction in 1963. Most notably, observations made by the instrument formed the basis of Russell A. Hulse and Joseph H. Talyor’s discovery of a new type of pulsar in 1974. The breakthrough would earn the duo the 1993 Nobel Prize in Physics. 

Some good could ultimately come out of the collapse of Arecibo. Questions had been asked about the maintenance of the radio telescope for some time and the fact that the cable which snapped in November dated back to the instrument’s construction 57 years ago has not escaped notice and comment.

As a result, various space agencies are being encouraged to make efforts to better maintain large-scale equipment and facilities so that losses like this can be avoided in the future.

This aerial view shows the damage at the Arecibo Observatory after one of the main cables holding the receiver broke in Arecibo, Puerto Rico, on December 1, 2020. – The radio telescope in Puerto Rico, which once starred in a James Bond film, collapsed Tuesday when its 900-ton receiver platform fell 450 feet (140 meters) and smashed onto the radio dish below. (Photo by Ricardo ARDUENGO / AFP) (Photo by RICARDO ARDUENGO/AFP via Getty Images)

For most of us, 2020 is going to be a year that we would rather forget. Whilst very few of us come honestly comment that we have had anything approaching a ‘good year’ space science has plowed ahead, albeit mildly hindered by the global pandemic.

Our knowledge and understanding of space science are better off at the end of 2020 than it was twelve months earlier, and that is at least something positive that has emerged from this painful year.

12 times the Arecibo telescope helped us figure out the universe

The Arecibo telescope in 2019. Image credits: University of Central Florida.

The collapse of the Arecibo radio telescope in Puerto Rico sent ripples through the world of science. Many mourned the loss of a telescope that helped us learn so many important things about the universe, with local researchers even tearing up during interviews.

The telescope, which was built in 1963, was still doing science — here are just some of the important discoveries made thanks to the Arecibo telescope.

Discovering the first-ever exoplanet

Artist’s impression of pulsar PSR B1257+12 and the planets orbiting it. The one in the foreground is planet “C”. Image credits: NASA/R Hurt.

In 1990, researchers working at Arecibo discovered a millisecond pulsar, a kind of neutron star, with a rotation period of 6.22 milliseconds (9,650 rpm).

In 1992, subsequent measurements found the first-ever extrasolar planets: two planets orbiting the pulsar. Two years later, more refined methods found one more planet orbiting the pulsar.

The origins of water ice on Mercury

Mercury, the nearest planet to the Sun, isn’t the first place you’d expect to find water (or anything) frozen. But in 1991, astronomers at the Arecibo Observatory discovered “extremely reflective” material radiating from Mercury’s surface — which many interpreted as evidence of ice.

Images from Messenger confirmed the Arecibo findings. Image credits: NASA.

In 2017, data from the Messenger spacecraft around Mercury confirmed the existence of pockets of ice on Mercury, in cratered areas which are permanently shaded. Mercury doesn’t have an atmosphere, which means the heat doesn’t diffuse, so you can have scorching hot temperatures in close proximity to sub-freezing temperatures.

The Arecibo message

The Arecibo telescope was heavily involved in the SETI project, looking for potential signals from alien civilizations. In 1974, humanity even sent an interstellar radio message carrying basic information about humanity and the Earth (the message was aimed at the globular star cluster M13). It was meant to serve as a demonstration of human technological achievement, a way to show we can send out interstellar messages, rather than a real attempt to start a conversation.

A demonstration of the message with color added to highlight its separate parts. The binary transmission sent carried no color information.

The message was designed by Frank Drake, with the help of Carl Sagan and other astronomers and broadcast at Arecibo. Among others, it carried information about the numbers from 1 to 10 (white), the atomic numbers of chemical elements that make up DNA (purple), the dimension of an average human (blue/white), the graphic figure of a human (red), a graphic of the solar system (yellow), and a graphic of the Arecibo radio telescope (purple, white, and blue).

Discovering the first binary pulsar

Pulsars are highly magnetized rotating compact stars that emit beams of electromagnetic radiation out of their magnetic poles. Sometimes, pulsars have companions, like a white dwarf or a neutron star, in which case it’s called a binary pulsar. The first pulsar was discovered in 1967, but it was Russell A. Hulse and Joseph H. Taylor in 1974 that discovered the first binary pulsar.

Pulsars, like the Crab Nebula depicted in this composite optical/X-ray image, have been extensively studied by the Arecibo telescope. Jocelyn Bell discovered the first pulsar in 1967. Image credits: NASA.

The two researchers at the Arecibo telescope discovered the binary pulsar using gravitational physics, paving the way for the discovery of the fabled gravitational waves. Their work was rewarded with a Nobel Prize.

Finding a dark matter galaxy

In 2006, astronomers discovered a mysterious cloud of hydrogen 50 million light-years from Earth. They called it VIRGOHI 21. Much to the surprise of astronomers, VIRGOHI 21 turned out to be a dark matter galaxy that didn’t emit any visible light (which is why a radio telescope turned out to be so useful).

Animation of Arecibo data. VIRGOHI 21 is the structure in the center. Source and full story here.

While there is still some controversy about what this galaxy really is (or if it even is a galaxy at all), data from Arecibo allowed its discovery and analysis, taking us one step closer to understanding one of the more exotic astronomical phenomena out there.

Understanding the ‘Weird!’ signal

In 2017, a weird signal (formally named ‘Weird!’ by astronomers) was reported. As if often happens, people’s imagination immediately went to aliens, but it turns out this wasn’t the case. Astronomers suspected a signal from a dim red dwarf, but this also didn’t turn out to be true.

Using data from the Arecibo telescope, researchers found that the signal was much more prosaic: it was interference from a nearby satellite.

Studying an asteroid close to Earth

Arecibo Radar images of the asteroid (101955) Bennu and the physical model of the asteroid developed from those images.

The Bennu asteroid was intercepted by the NASA OSIRIS-REx spacecraft, which closed in and captured an image from a distance of 600 metres (2,000 ft) from Bennu’s surface. But before NASA could get up close and personal with the asteroid, Bennu was studied extensively with the Arecibo telescope, helping to better prepare the mission.

In 2000, researchers at Arecibo also captured the first images of near-Earth asteroids.

Mosaic image of Bennu consisting of 12 images collected by OSIRIS-REx from a range of 24 km (15 mi).

Radio maps of Venus and Titan

The first radar maps of Venus were done with the Arecibo telescope in the late 1970s, showing some of the Venusian relief and geology, and showing that its surface is less than one billion years old.

The maps were constantly refined and finessed. Many features, including mountain ranges, volcanic domes, and craters can be seen.

This is a radar image of the planet Venus made by transmitting a signal at 13 cm wavelength from Arecibo. Credit: Donald Campbell, Jean-Luc Margot, Lynn Carter, and Bruce Campbell

Titan, the largest moon of Saturn, is a weird place. It’s an icy world whose surface is completely obscured by a golden hazy atmosphere — and, as we’ve learned thanks to the Arecibo telescope, it has liquid hydrocarbon lakes on its surface.

As it is often the case, observations by Arecibo inspired future missions that analyzed things in greater detail. Here, the Cassini mission surveyed Titan and snapped the beautiful image below.

Radar images from NASA’s Cassini spacecraft reveal many lakes on Titan’s surface, some filled with liquid, and some appearing as empty depressions. Image credits: NASA/JPL/USGS.

Neutron stars can be very large, but forming black holes is difficult

Neutron stars and black holes are the two most massive objects known in the universe. But they’re not always what they seem to be. In fact, neutron stars can be considerably more massive than previously believed, and it is more difficult to form black holes, according to 2008 research from Arecibo.

“The matter at the center of the neutron stars is the densest in the universe. It is one to two orders of magnitude denser than matter in the atomic nucleus. It is so dense we don’t know what it is made out of,” said Paulo Freire, an astronomer from the observatory, who presented the research. “For that reason, we have at present no idea of how large or how massive neutron stars can be.”

The most metal-poor galaxy in the known universe

In astronomy, metalicity is the abundance of elements present in an object that are heavier than hydrogen or helium. Galaxies with low metallicity are of special importance for astronomers as they could provide crucial insights about chemical evolution of stars and astrophysical processes occurring in the early universe.

In 2016, astronomers found the galaxy with the lowest known metallicity, which could offer a glimpse into the early days of the universe, and also mark a paradigm shift in the search for metal-poor galaxies.

Distant galaxies could hold ingredients for life

In 2008, astronomers from the Arecibo Observatory detected the molecules methenamine and hydrogen cyanide — two ingredients that build life-forming amino acids — in a galaxy some 250 million light-years away.

The fact that they could be observed at such a huge distance suggests that the compounds are highly abundant in the galaxy. It’s remarkable that we can make any observations about a galaxy this far away, let alone that we can tell that it has potentially life-forming molecules.

Solving the mystery of vanshing pulsars

The pulsar pictured here, which resides in the Messier 82 galaxy 12 million light-years away, sends out X-ray beams that pass Earth every 1.37 seconds. Credit: NASA/JPL-Caltech

Pulsars are often considered the orderly ticking clocks of the universe. A 2017 survey carried out at Arecibo contradicted that view, finding that sometimes, pulsars undergo a “vanishing act”.

“These disappearing pulsars may far outnumber normal pulsars,” said Dr. Victoria Kaspi of McGill University in Canada and the principal investigator on the PALFA project. “In fact, they may redefine what we think of as normal.”

In addition to all these discoveries (and many which we’ve missed), Arecibo was also an iomportant part of NANOGrav, the orth American Nanohertz Observatory for Gravitational Waves (NANOGrav), a consortium of astronomers who aim to detect gravitational waves via regular observations of an ensemble of pulsars. The NANOGrav group posted this statement:

“The NANOGrav Collaboration is greatly saddened by the impact of the planned decommissioning of the 305-m Arecibo telescope on the staff and scientists who have worked so hard for so many years to ensure its success. We will miss the telescope itself, as one of our own. Many of our scientific careers began with the training we received and camaraderie we enjoyed at Arecibo, for which we will be forever grateful. We also stand in solidarity with our fellow citizens in Puerto Rico for whom Arecibo has been an inspiration and source of pride for so many years. We urge the National Science Foundation to identify uses for the site and staff, as soon as practicable, that benefit from Arecibo’s unique characteristics and promote its continued inspirational role in STEM fields.”

The iconic Arecibo Observatory has now collapsed to rubble

Less than two weeks after officials announced it’s too dangerous to attempt repairs, the Arecibo telescope has completely collapsed. The 900-ton platform of the world’s second-largest single-dish radio has broken down, leaving the telescope unrepairable.

Staff member Jonathan Friedman, who lives near the telescope, reported to the Associated Press that he heard a large rumble and rushed to the telescope. When he reached the top of a nearby hill, he saw the collapsed structure and a cloud of dust rising from it.

“It sounded like a rumble. I knew exactly what it was,” he told AP. “I was screaming. Personally, I was out of control… I don’t have words to express it. It’s a very deep, terrible feeling.”

The Arecibo Observatory’s main feature was the huge radio telescope. Built inside a karst sinkhole, the telescope had a shape of a spherical cap 1,000 feet (305 m) in diameter. Astronomers would brag that Pierce Brosnan was too afraid to run up the telescope in the James Bond movie — something they do every day. It had almost 40,000 perforated aluminum panels supported by a mesh of steel cables.

The neglect of these cables are what ultimately brought its demise.

The telescope before its collapse. Image credits: University of Central Florida.

It started with a cable break in August 2020, which threatened the structural integrity of the whole structure. Another break in November 2020 made it too dangerous to repair the telescope. Each cable was made of 160 wires but drone footage of the remaining cables showed that these wires were breaking almost daily.

The National Science Foundation (NSF), who manages the telescope, announced that it would start dismantling the telescope, while still supporting the other on-site facilities, such as the LIDAR facility for geospace research and the Ángel Ramos Foundation Visitor Center.

Arecibo Observatory, Puerto Rico, in 2019. The telescope had a 869-foot (265 m) radius of curvature and was built over shade-tolerant vegetation, to minimize the environmental impact.

The platform was built in the 1960s, but several instruments were added in the 1990s, making the entire structure much heavier. Even so, it’s not clear exactly why the structure collapsed, as it was still active and undergoing active maintenance.

 “[It] should not have failed the way it did,” says Ashley Zauderer (NSF), according to Sky and Telescope. “The team is looking very closely at why that happened.”

“Our focus is now on assessing the damage, finding ways to restore operations at other parts of the observatory, and working to continue supporting the scientific community, and the people of Puerto Rico,” says NSF director Sethuraman Panchanathan. 

Twitter user Deborah Martorell also shared a photo of the collapsed structure.

Translation: “Friends, it is with deep regret to inform you that the Arecibo Observatory platform has just collapsed.”

The telescope will now be dismantled. The NSF is under contract to return the site to its original natural state. There seems to be no plan for rebuilding the telescope or replacing it with another scientific instrument. Not much (if anything) can be saved from the scientific equipment.

Many scientists and Puerto Ricans mourned the announcement, with some tearing up during interviews.

The Arecibo telescope was still doing good science

Arecibo was very storied during the SETI days, but while those days are long behind, the telescope was still very active in recent years. Arecibo was the first radio telescope to discover a repeating Fast Radio Burst (FRB), it helped us better understand our planetary neighbors, and even gave us the discovery of the first binary pulsar, which was offered a Nobel Prize.

In recent days, however, the NSFW was struggling to get the funding to properly maintain it. In 2017, Arecibo faced closure after the NSF found its budget hacked and slashed. Radio astronomy funding in general is struggling in the US. It’s still speculation at this point, but this underfunding may very well be a cause for the telescope’s collapse.

It’s a sad day for science when, after surviving hurricanes and earthquakes, a landmark telescope collapses due to underfunding and neglect. Our understanding of the universe will be a little bit poorer after the collapse of this telescope.

The telescope after the first cable failure in August. Image credits: University of Central Florida.

How a broken cable almost destroyed a thousand-foot telescope

The Arecibo Observatory in Puerto Rico, one of the largest radio telescopes in the world, was severely damaged during a tropical storm, with problems starting from a broken cable.

This is just the latest in a string of recent misfortune that the telescope suffered in recent years.

A photo of the damages. Credit University of Central Florida

One of the auxiliary cables that helps support a metal platform in place above the observatory broke on August 10, triggering a 100-foot-long gash on the telescope’s reflector dish. The damage happened during the Tropical Storm Isaias, but it isn’t clear yet just how the damage occurred.

“We have a team of experts assessing the situation,” said Francisco Cordova, the director of the observatory, in a statement. “Our focus is assuring the safety of our staff, protecting the facilities and equipment, and restoring the facility to full operations as soon as possible.”

The break occurred early in the morning when the storm was kicking in, according to Cordova. When the three-inch cable fell it also damaged about six to eight panels in the Gregorian Dome and twisted the platform used to access the dome. The observatory is now closed pending an investigation.

The observatory is managed by the University of Central Florida and it began operating in 1963. Over the years, it has produced many scientific discoveries in the solar system and beyond, being considered one of the most powerful telescopes in the world at the time. It’s also where SETI, the search of extraterrestrial intelligence, began. Nowadays, Arecibo is used by scientists around the world to conduct research in the areas of atmospheric sciences, planetary sciences, radio astronomy and radar astronomy. It is also home to a team that runs the Planetary Radar Project supported by NASA’s Near-Earth Object Observations Program.

While the damage was shocking to everyone, it’s far from the first time that Arecibo had to deal with technical difficulties. Back in September 2017, Puerto Rico was severely hit by Hurricane Maria, which knocked power across the island for months. An antenna suspended over the observatory fell and punctured a dish. The hurricane came at a difficult time for the observatory. The National Science Foundation, which owns Arecibo, was already considering giving the observatory to someone else so it could focus on other projects. The foundation finally did an agreement with a group of three institutions to take over the operations.

Then, earthquakes hit the island in January of this year. The tremors were as strong as 6.4 magnitudes and it made it impossible to carry out observations, with no visitors allowed on-site. The dish wasn’t damaged but operations couldn’t be restarted until the tremors fully stopped.