The James Webb Space Telescope has reached another major milestone in its mirror alignment process as the team has successfully worked through the second and third phases of the process and completed Segment Alignment.
Completed Segment Alignment
Earlier this month, NASA shared the first photo ever taken by the James Webb Space Telescope and while the moment was impressive, the actual quality of the photo was far from complete. It depicted a mosaic of 18 randomly organized dots of starlight, which were created by reflecting light from the same star back at Webb’s misaligned secondary mirror. This would serve as the starting point from which the team would focus its efforts on properly aligning those dots.
“The team’s challenge was twofold: confirm that NIRCam was ready to collect light from celestial objects, and then identify starlight from the same star in each of the 18 primary mirror segments,” NASA explains.
This hexagonal image array captured by the NIRCam instrument shows the progress made during the Segment Alignment phase, further aligning Webb’s 18 primary mirror segments and secondary mirror using precise movements commanded from the ground. | Credit: NASA/STScI
Now with the second and third stages of the process out of seven complete, the 18 scattered dots of the Webb telescope’s signature hexagonal formation are more refined and aligned. The completion of this process, known as Segment Alignment according to NASA, was a key step prior to overlapping the light from all the mirrors so that they can work in unison.
This gif shows the “before” and “after” images from Segment Alignment, when the team corrected large positioning errors of its primary mirror segments and updated the alignment of the secondary mirror. | Credit: NASA/STScI
Focus Stacking 18 Segments
NASA says that once Segment Alignment was achieved, the focused dots reflected by each mirror segment were stacked on top of each other and combined on the same location on the Webb’s NIRCam’s sensor. The team activated sets of six mirrors at a time and commanded them to repoint their light to overlap until all the starlight was overlapped with each other.
The result is the image below, which shows significant progress from the state of the images coming out of Webb less than a month ago.
During this phase of alignment known as Image Stacking, individual segment images are moved so they fall precisely at the center of the field to produce one unified image instead of 18. In this image, all 18 segments are on top of each other. After future alignment steps, the image will be even sharper. | Credit: NASA/STScI
“We still have work to do, but we are increasingly pleased with the results we’re seeing,” Lee Feinberg, optical telescope element manager for Webb at NASA’s Goddard Space Flight Center, says. “Years of planning and testing are paying dividends, and the team could not be more excited to see what the next few weeks and months bring.”
Even though the segments are properly aligned, each of the mirror segments are still acting as 18 small telescopes instead of one big one, as is the final intent. NASA says that these segments now need to be lined up to each other with an accuracy smaller than a the wavelength of light.
The next step, phase four of seven, is known as Coarse Phasing, where the NIRCam will be used to capture light spectra from 20 separate pairings of the mirror segments.
“[Coarse Phasing] helps the team identify and correct vertical displacement between the mirror segments, or small differences in their heights,” NASA explains. “This will make the single dot of starlight progressively sharper and more focused in the coming weeks.”
Astronomers have spotted a pair of black holes that are heading for an epic collision. One is a supermassive black hole, the enormous type of black hole which is found at the center of most galaxies, and the other is a smaller companion that is orbiting around its partner and spiraling closer in. Eventually, the two will merge, and studying them now could give clues about how supermassive black holes come to be.
Researchers aren’t sure exactly how supermassive black holes, which are millions or even billions of times the mass of the sun, are created. They think that they might form from the merging of two smaller supermassive black holes, but it’s very rare to spot such a pair, so this new discovery could shine a light on this process.
In this illustration, light from a smaller black hole (left) curves around a larger black hole and forms an almost-mirror image on the other side. The gravity of a black hole can warp the fabric of space itself, such that light passing close to the black hole will follow a curved path around it.Caltech-IPAC
The pair were spotted by a team of astronomers led by Sandra O’Neill from Caltech. The team observed the pair in a galaxy called PKS 2131-021 using radio telescopes on Earth which can see jets that are ejected from black holes’ event horizons when hot gas hits them. These jets are so powerful they can be detected from Earth, especially if the jets are pointed toward us, forming what is called a blazar.
The team looked at observations of the blazar stretching back over 45 years to identify the pair. They found variations in the brightness of the blazar which fitted a very distinct pattern. “When we realized that the peaks and troughs of the light curve detected from recent times matched the peaks and troughs observed between 1975 and 1983, we knew something very special was going on,” said O’Neill in a statement.
By comparing observations from five different observatories dating back to 1975, the researchers were able to confirm the variations were due to a second black hole tugging on the orbit of the supermassive black hole, as the two orbit each other approximately every two years.
“This work is a testament to the importance of perseverance,” said co-author Joseph Lazio of NASA’s Jet Propulsion Laboratory in a statement. “It took 45 years of radio observations to produce this result. Small teams, at different observatories across the country, took data week in and week out, month in and month out, to make this possible.”
Mycobacterium tuberculosis (Public Health Image Library, NIAID, Image ID: 18139)
A remarkable discovery has made within the field of microbiology – the largest bacterium ever recorded, in terms of overall size. The organism is the approximate size of a fly. That is whether the term ‘microbiology’ remains appropriate, given that the organism is visible with the naked eye.
The giant string-like bacterium has been isolated from Caribbean mangroves and the cell can grow up to 2 centimetres in length. This places the organism around 5,000 times larger than most bacteria. The discovery challenges the accepted understanding of bacteriology in that the organism goes beyond what was hitherto considered biologically possible for a single-celled organism.
The bacterium has been named Thiomargarita magnifica by the consortium of scientists who have discovered it, based at the Lawrence Berkeley National Laboratory in the U.S. and from CNRS in France.
The discovery came about when Olivier Gros, a marine biologist at the University of the French Antilles, Pointe-à-Pitre, first came across the atypical organisms appearing as thin filaments on the surfaces of decaying mangrove leaves in a local swamp five years ago. Subsequent isolation and research established the organism as bacterial.
While other large bacteria have been isolated in the past, T. magnifica exceeds these other classified organisms by around 50-fold.
Stained microphotograph of Thiomargarita bacteria. Image: NASA, via Wikipedia CC 2.0 licence
Physical size is not the only feature in relation to size, as labelling the organism’s DNA with fluorescent tags has revealed. Whereas the typical bacterial genomes are about 4 million bases and about 3900 genes, T. magnifica boasts 11 million bases harbouring some 11,000 distinguishable genes.
The genus Thiomargarita includes vacuolate sulphur bacteria species (the cell cytoplasm is surrounded a central vacuole). The genus is only found in extreme environments on Earth, including methane seeps, mud volcanoes, brine pools, and organic-rich sediments. These niches are essential for energy production: the bacteria reduce inorganic species of sulphur to produce energy for the fixation of carbon.
Deeper research will be required to ascertain how the organisms are so large. It is established that the genome possesses several unusual features for a bacterium, such as the largest number of metacaspases (cysteine proteases) and introns (pathways used to assemble new genes) ever reported. There are also a large number of mobile genetic elements, which are essential to the core metabolism.
There is also a taxonomical conundrum, since the newly discovered microbe blurs the established line between prokaryotes and eukaryotes. This is because it is the first and only bacterium found to unambiguously segregate its genetic material in membrane-bound organelles in the manner of eukaryotes.
The bacterium contains two membrane sacs, one of which contains all the cell’s DNA. The other sac helps to keep the bacterium’s cellular contents pressed up against the outer cell wall in order for the molecules it needs can diffuse in and out. These sacs have been dubbed these sacs ‘pepins’, according to Nature, a name inspired by the pips in fruit.
The research paper describing T. magnifica can be accessed here, titled in somewhat understated fashion: “A centimeter-long bacterium with DNA compartmentalized in membrane-bound organelles.”
Long-term radio monitoring of a supermassive black hole at the center of a galaxy some 9 billion light years distant appears to show it has a massive unseen partner. The Caltech-led observations were made over a 13-year period by the Owens Valley Radio Observatory in Northern California and reveal that the radio black hole will soon merge with a companion black hole to form a supermassive black hole binary (SMBHB).
These two supermassive black holes appear to be orbiting around each other every two years, reports Caltech. The two giant bodies each have masses that are hundreds of millions of times larger than that of our Sun, and the objects are separated by a distance roughly 50 times that which separates our sun and Pluto, notes Caltech, but When the pair merge in roughly 10,000 years, the titanic collision is expected to shake space and time itself, sending gravitational waves across the universe.
The observations are detailed in a paper appearing this week in The Astrophysical Journal Letters.
The observed quasar, PKS 2131-021, is part of a subclass of quasars called blazars in which the jet is pointing toward the Earth. It’s now only the second known candidate for a pair of supermassive black holes caught in the act of merging.
“From an astrophysics perspective, we expect there to be supermassive black hole binaries,” Joseph Lazio, an astrophysicist at NASA’s Jet Propulsion Laboratory and one of the paper’s co-authors, told me. “Most, if not all, large galaxies have supermassive black holes in their centers, galaxies are observed to be undergoing mergers, so there should be supermassive black hole binaries that result.”
PKS 2131-021 is only one of 1,800 blazars that a group of researchers at Caltech in Pasadena has been monitoring at the Owens Valley Observatory as part of a general study of blazar behavior, Caltech notes. But this particular blazar exhibits a strange behavior: Its brightness shows regular ups and downs as predictably as the ticking of a clock, which researchers now think this regular variation is the result of a second black hole tugging on the first, Caltech reports.
After learning that two other radio telescopes had also studied this system – the University of Michigan Radio Observatory (1980 to 2012) and the Haystack Observatory (1975 to 1983) – they dug into the additional data and found that it matched predictions for how the blazar’s brightness should change over time, says Caltech.
The telltale evidence came from radio observations of PKS 2131-021 that span 45 years, notes Caltech.
A powerful jet emanating from one of the two black holes within PKS 2131-021 is shifting back and forth due to the pair's orbital motion; this, in turn, causes periodic changes in the quasar's radio-light brightness, Caltech reports.
Five different observatories registered these oscillations, including Caltech’s Owens Valley Radio Observatory (OVRO), the University of Michigan Radio Astronomy Observatory (UMRAO), MIT's Haystack Observatory, the National Radio Astronomy Observatory (NRAO), Metsähovi Radio Observatory in Finland, and NASA's Wide-field Infrared Survey Explorer (WISE) space satellite.
Why are such merging supermassive black holes so difficult to detect?
On astronomical scales, even though the black holes might be “supermassive,” their separation is tiny. The other is that the black holes themselves don’t emit any radiation of course, says Lazio. The radiation results either from material that is in the process of falling into a black hole or from a (powerful) jet that results from some of the material that doesn’t fall into the hole, he says. If there’s material around only one of the black holes and not the other, then it could be easy to be confused about whether there is one or two black holes present, says Lazio.
What can be learned from these observations?
“This discovery emphasizes the importance of the simple act of monitoring the brightness of celestial objects,” said Lazio. “While apparently a simple task, keeping such a project running for the better part of a decade, day in, day out, requires considerable dedication and stamina.”
This artist’s concept shows two candidate supermassive black holes at the heart of a quasar called PKS 2131-021. In this view of the system, gravity from the foreground black hole (right) can be seen twisting and distorting the light of its companion, which has a powerful jet. Each black hole is about a hundred million times the mass of our sun, with the black hole in the foreground being slightly less massive. Credit: Caltech/R. Hurt (IPAC)
Astronomers find evidence for the tightest-knit supermassive black hole duo observed to date.
Locked in an epic cosmic waltz 9 billion light years away, two supermassive black holes appear to be orbiting around each other every two years. The two giant bodies each have masses that are hundreds of millions of times larger than that of our sun, and the objects are separated by a distance roughly 50 times that which separates our sun and Pluto. When the pair merge in roughly 10,000 years, the titanic collision is expected to shake space and time itself, sending gravitational waves across the universe.
A Caltech-led team of astronomers has discovered evidence for this scenario taking place within a fiercely energetic object known as a quasar. Quasars are active cores of galaxies in which a supermassive black hole is siphoning material from a disk encircling it. In some quasars, the supermassive black hole creates a jet that shoots out at near the speed of light. The quasar observed in the new study, PKS 2131-021, belongs to a subclass of quasars called blazars in which the jet is pointing toward the Earth. Astronomers already knew quasars could possess two orbiting supermassive black holes, but finding direct evidence for this has proved difficult.
Two supermassive black holes are seen orbiting each other in this artist’s loopable animation. The more massive black hole, which is hundreds of millions times the mass of our sun, is shooting out a jet that changes in its apparent brightness as the duo circles each other. Astronomers found evidence for this scenario in a quasar called PKS 2131-021 after analyzing 45-years-worth of radio observations that show the system periodically dimming and brightening. The observed cyclical pattern is thought to be caused by the orbital motion of the jet. Credit: Caltech/R. Hurt (IPAC)
Reporting in The Astrophysical Journal Letters, the researchers argue that PKS 2131-021 is now the second known candidate for a pair of supermassive black holes caught in the act of merging. The first candidate pair, within a quasar called OJ 287, orbit each other at greater distances, circling every nine years versus the two years it takes for the PKS 2131-021 pair to complete an orbit.
The telltale evidence came from radio observations of PKS 2131-021 that span 45 years. According to the study, a powerful jet emanating from one of the two black holes within PKS 2131-021 is shifting back and forth due to the pair’s orbital motion. This causes periodic changes in the quasar’s radio-light brightness. Five different observatories registered these oscillations, including Caltech’s Owens Valley Radio Observatory (OVRO), the University of Michigan Radio Astronomy Observatory (UMRAO), MIT’s Haystack Observatory, the National Radio Astronomy Observatory (NRAO), Metsähovi Radio Observatory in Finland, and NASA’s Wide-field Infrared Survey Explorer (WISE) space satellite.
Artist’s animation of a supermassive black hole circled by a spinning disk of gas and dust. The black hole is shooting out a relativistic jet—one that travels at nearly the speed of light. Credit: Caltech/R. Hurt (IPAC)
The combination of the radio data yields a nearly perfect sinusoidal light curve unlike anything observed from quasars before.
“When we realized that the peaks and troughs of the light curve detected from recent times matched the peaks and troughs observed between 1975 and 1983, we knew something very special was going on,” says Sandra O’Neill, lead author of the new study and an undergraduate student at Caltech who is mentored by Tony Readhead, Robinson Professor of Astronomy, Emeritus.
Ripples in Space and Time
Most, if not all, galaxies possess monstrous black holes at their cores, including our own Milky Way galaxy. When galaxies merge, their black holes “sink” to the middle of the newly formed galaxy and eventually join together to form an even more massive black hole. As the black holes spiral toward each other, they increasingly disturb the fabric of space and time, sending out gravitational waves, which were first predicted by Albert Einstein more than 100 years ago.
The National Science Foundation’s LIGO (Laser Interferometer Gravitational-Wave Observatory), which is managed jointly by Caltech and MIT, detects gravitational waves from pairs of black holes up to dozens of times the mass of our sun. However, the supermassive black holes at the centers of galaxies have millions to billions of times as much mass as our sun, and give off lower frequencies of gravitational waves than those detected by LIGO.
Three sets of radio observations of the quasar PKS 2131-02, spanning 45 years, are plotted here, with data from Owens Valley Radio Observatory (OVRO) in blue; University of Michigan Radio Astronomical Observatory (UMRAO) in brown; and Haystack Observatory in green. The observations match a simple sine wave, indicated in blue. Astronomers believe that the sine wave pattern is caused by two supermassive black holes at the heart of the quasar orbiting around each other every two years. (A period of five years was actually observed due to a Doppler effect caused by the expansion of the universe.) One of the black holes is shooting out a relativistic jet that dims and brightens periodically. Note that data from OVRO and UMRAO match for the peak in 2010, and the UMRAO and Haystack data match for the peak in 1981. The magnitudes of the peaks observed around 1980 are twice as large as those observed in recent times, presumably because more material was falling towards the black hole and being ejected at that time. Credit: Tony Readhead/Caltech
In the future, pulsar timing arrays—which consist of an array of pulsing dead stars precisely monitored by radio telescopes—should be able to detect the gravitational waves from supermassive black holes of this heft. (The upcoming Laser Interferometer Space Antenna, or LISA, mission would detect merging black holes whose masses are 1,000 to 10 million times greater than the mass of our sun.) So far, no gravitational waves have been registered from any of these heavier sources, but PKS 2131-021 provides the most promising target yet.
In the meantime, light waves are the best option to detect coalescing supermassive black holes.
The first such candidate, OJ 287, also exhibits periodic radio-light variations. These fluctuations are more irregular, and not sinusoidal, but they suggest the black holes orbit each other every nine years. The black holes within the new quasar, PKS 2131-021, orbit each other every two years and are 2,000 astronomical units apart, about 50 times the distance between our sun and Pluto, or 10 to 100 times closer than the pair in OJ 287. (An astronomical unit is the distance between Earth and the sun.)
Sandra O’Neill. Credit: Caltech
Revealing the 45-Year Light Curve
Readhead says the discoveries unfolded like a “good detective novel,” beginning in 2008 when he and colleagues began using the 40-meter telescope at OVRO to study how black holes convert material they “feed” on into relativistic jets, or jets traveling at speeds up to 99.98 percent that of light. They had been monitoring the brightness of more than 1,000 blazars for this purpose when, in 2020, they noticed a unique case.
“PKS 2131 was varying not just periodically, but sinusoidally,” Readhead says. “That means that there is a pattern we can trace continuously over time.” The question, he says, then became how long has this sine wave pattern been going on?
The research team then went through archival radio data to look for past peaks in the light curves that matched predictions based on the more recent OVRO observations. First, data from NRAO’s Very Long Baseline Array and UMRAO revealed a peak from 2005 that matched predictions. The UMRAO data further showed there was no sinusoidal signal at all for 20 years before that time—until as far back as 1981 when another predicted peak was observed.
“The story would have stopped there, as we didn’t realize there were data on this object before 1980,” Readhead says. “But then Sandra picked up this project in June of 2021. If it weren’t for her, this beautiful finding would be sitting on the shelf.”
O’Neill began working with Readhead and the study’s second author Sebastian Kiehlmann, a postdoc at the University of Crete and former staff scientist at Caltech, as part of Caltech’s Summer Undergraduate Research Fellowship (SURF) program. O’Neill began college as a chemistry major but picked up the astronomy project because she wanted to stay active during the pandemic. “I came to realize I was much more excited about this than anything else I had worked on,” she says.
With the project back on the table, Readhead searched through the literature and found that the Haystack Observatory had made radio observations of PKS 2131-021 between 1975 and 1983. These data revealed another peak matching their predictions, this time occurring in 1976.
“This work shows the value of doing accurate monitoring of these sources over many years for performing discovery science,” says co-author Roger Blandford, Moore Distinguished Scholar in Theoretical Astrophysics at Caltech who is currently on sabbatical from Stanford University.
Tony Readhead. Credit: Caltech
Like Clockwork
Readhead compares the system of the jet moving back and forth to a ticking clock, where each cycle, or period, of the sine wave corresponds to the two-year orbit of the black holes (though the observed cycle is actually five years due to light being stretched by the expansion of the universe). This ticking was first seen in 1976 and it continued for eight years before disappearing for 20 years, likely due to changes in the fueling of the black hole. The ticking has now been back for 17 years.
“The clock kept ticking,” he says, “The stability of the period over this 20-year gap strongly suggests that this blazar harbors not one supermassive black hole, but two supermassive black holes orbiting each other.”
The physics underlying the sinusoidal variations were at first a mystery, but Blandford came up with a simple and elegant model to explain the sinusoidal shape of the variations.
“We knew this beautiful sine wave had to be telling us something important about the system,” Readhead says. “Roger’s model shows us that it is simply the orbital motion that does this. Before Roger worked it out, nobody had figured out that a binary with a relativistic jet would have a light curve that looked like this.”
Says Kiehlmann: “Our study provides a blueprint for how to search for such blazar binaries in the future.”
Reference: “The Unanticipated Phenomenology of the Blazar PKS 2131–021: A Unique Supermassive Black Hole Binary Candidate” by S. O’Neill, S. Kiehlmann, A. C. S. Readhead, M. F. Aller, R. D. Blandford, I. Liodakis, M. L. Lister, P. Mróz, C. P. O’Dea, T. J. Pearson, V. Ravi, M. Vallisneri, K. A. Cleary, M. J. Graham, K. J. B. Grainge, M. W. Hodges, T. Hovatta, A. Lähteenmäki, J. W. Lamb, T. J. W. Lazio, W. Max-Moerbeck, V. Pavlidou, T. A. Prince, R. A. Reeves, M. Tornikoski, P. Vergara de la Parra and J. A. Zensus, 23 February 2022, The Astrophysical Journal Letters. DOI: 10.3847/2041-8213/ac504b
The Astrophysical Journal Letters study titled “The Unanticipated Phenomenology of the Blazar PKS 2131-021: A Unique Super-Massive Black hole Binary Candidate” was funded by Caltech, the Max Planck Institute for Radio Astronomy, NASA, National Science Foundation (NSF), the Academy of Finland, the European Research Council, ANID-FONDECYT (Agencia Nacional de Investigación y Desarrollo-Fondo Nacional de Desarrollo Científico y Tecnológico in Chile), the Natural Science and Engineering Council of Canada, the Foundation for Research and Technology – Hellas in Greece, the Hellenic Foundation for Research and Innovation in Greece, and the University of Michigan. Other Caltech authors include Tim Pearson, Vikram Ravi, Kieran Cleary, Matthew Graham, and Tom Prince. Other authors from the Jet Propulsion Laboratory, which is managed by Caltech for NASA, include Michele Vallisneri and Joseph Lazio.
This artist's concept shows two candidate supermassive black holes at the heart of a quasar called PKS 2131-021. In this view of the system, gravity from the foreground black hole (right) can be seen twisting and distorting the light of its companion, which has a powerful jet. Each black hole is about a hundred million times the mass of our sun, with the black hole in the foreground being slightly less massive. Credit: Caltech/R. Hurt (IPAC)
Locked in an epic cosmic waltz 9 billion light years away, two supermassive black holes appear to be orbiting around each other every two years. The two giant bodies each have masses that are hundreds of millions of times larger than that of our sun, and the objects are separated by a distance roughly 50 times that which separates our sun and Pluto. When the pair merge in roughly 10,000 years, the titanic collision is expected to shake space and time itself, sending gravitational waves across the universe.
A Caltech-led team of astronomers has discovered evidence for this scenario taking place within a fiercely energetic object known as a quasar. Quasars are active cores of galaxies in which a supermassive black hole is siphoning material from a disk encircling it. In some quasars, the supermassive black hole creates a jet that shoots out at near the speed of light. The quasar observed in the new study, PKS 2131-021, belongs to a subclass of quasars called blazars in which the jet is pointing toward the Earth. Astronomers already knew quasars could possess two orbiting supermassive black holes, but finding direct evidence for this has proved difficult.
Reporting in The Astrophysical Journal Letters, the researchers argue that PKS 2131-021 is now the second known candidate for a pair of supermassive black holes caught in the act of merging. The first candidate pair, within a quasar called OJ 287, orbit each other at greater distances, circling every nine years versus the two years it takes for the PKS 2131-021 pair to complete an orbit.
The telltale evidence came from radio observations of PKS 2131-021 that span 45 years. According to the study, a powerful jet emanating from one of the two black holes within PKS 2131-021 is shifting back and forth due to the pair's orbital motion. This causes periodic changes in the quasar's radio-light brightness. Five different observatories registered these oscillations, including Caltech's Owens Valley Radio Observatory (OVRO), the University of Michigan Radio Astronomy Observatory (UMRAO), MIT's Haystack Observatory, the National Radio Astronomy Observatory (NRAO), Metsähovi Radio Observatory in Finland, and NASA's Wide-field Infrared Survey Explorer (WISE) space satellite.
The combination of the radio data yields a nearly perfect sinusoidal light curve unlike anything observed from quasars before.
"When we realized that the peaks and troughs of the light curve detected from recent times matched the peaks and troughs observed between 1975 and 1983, we knew something very special was going on," says Sandra O'Neill, lead author of the new study and an undergraduate student at Caltech who is mentored by Tony Readhead, Robinson Professor of Astronomy, Emeritus.
Ripples in Space and Time
Most, if not all, galaxies possess monstrous black holes at their cores, including our own Milky Way galaxy. When galaxies merge, their black holes "sink" to the middle of the newly formed galaxy and eventually join together to form an even more massive black hole. As the black holes spiral toward each other, they increasingly disturb the fabric of space and time, sending out gravitational waves, which were first predicted by Albert Einstein more than 100 years ago.
The National Science Foundation's LIGO (Laser Interferometer Gravitational-Wave Observatory), which is managed jointly by Caltech and MIT, detects gravitational waves from pairs of black holes up to dozens of times the mass of our sun. However, the supermassive black holes at the centers of galaxies have millions to billions of times as much mass as our sun, and give off lower frequencies of gravitational waves than those detected by LIGO.
In the future, pulsar timing arrays—which consist of an array of pulsing dead stars precisely monitored by radio telescopes—should be able to detect the gravitational waves from supermassive black holes of this heft. (The upcoming Laser Interferometer Space Antenna, or LISA, mission would detect merging black holes whose masses are 1,000 to 10 million times greater than the mass of our sun.) So far, no gravitational waves have been registered from any of these heavier sources, but PKS 2131-021 provides the most promising target yet.
In the meantime, light waves are the best option to detect coalescing supermassive black holes.
The first such candidate, OJ 287, also exhibits periodic radio-light variations. These fluctuations are more irregular, and not sinusoidal, but they suggest the black holes orbit each other every nine years. The black holes within the new quasar, PKS 2131-021, orbit each other every two years and are 2,000 astronomical units apart, about 50 times the distance between our sun and Pluto, or 10 to 100 times closer than the pair in OJ 287. (An astronomical unit is the distance between Earth and the sun.)
Revealing the 45-Year Light Curve
Readhead says the discoveries unfolded like a "good detective novel," beginning in 2008 when he and colleagues began using the 40-meter telescope at OVRO to study how black holes convert material they "feed" on into relativistic jets, or jets traveling at speeds up to 99.98 percent that of light. They had been monitoring the brightness of more than 1,000 blazars for this purpose when, in 2020, they noticed a unique case.
"PKS 2131 was varying not just periodically, but sinusoidally," Readhead says. "That means that there is a pattern we can trace continuously over time." The question, he says, then became how long has this sine wave pattern been going on?
The research team then went through archival radio data to look for past peaks in the light curves that matched predictions based on the more recent OVRO observations. First, data from NRAO's Very Long Baseline Array and UMRAO revealed a peak from 2005 that matched predictions. The UMRAO data further showed there was no sinusoidal signal at all for 20 years before that time—until as far back as 1981 when another predicted peak was observed.
"The story would have stopped there, as we didn't realize there were data on this object before 1980," Readhead says. "But then Sandra picked up this project in June of 2021. If it weren't for her, this beautiful finding would be sitting on the shelf."
O'Neill began working with Readhead and the study's second author Sebastian Kiehlmann, a postdoc at the University of Crete and former staff scientist at Caltech, as part of Caltech's Summer Undergraduate Research Fellowship (SURF) program. O'Neill began college as a chemistry major but picked up the astronomy project because she wanted to stay active during the pandemic. "I came to realize I was much more excited about this than anything else I had worked on," she says.
With the project back on the table, Readhead searched through the literature and found that the Haystack Observatory had made radio observations of PKS 2131-021 between 1975 and 1983. These data revealed another peak matching their predictions, this time occurring in 1976.
"This work shows the value of doing accurate monitoring of these sources over many years for performing discovery science," says co-author Roger Blandford, Moore Distinguished Scholar in Theoretical Astrophysics at Caltech who is currently on sabbatical from Stanford University.
Like Clockwork
Readhead compares the system of the jet moving back and forth to a ticking clock, where each cycle, or period, of the sine wave corresponds to the two-year orbit of the black holes (though the observed cycle is actually five years due to light being stretched by the expansion of the universe). This ticking was first seen in 1976 and it continued for eight years before disappearing for 20 years, likely due to changes in the fueling of the black hole. The ticking has now been back for 17 years.
"The clock kept ticking," he says, "The stability of the period over this 20-year gap strongly suggests that this blazar harbors not one supermassive black hole, but two supermassive black holes orbiting each other."
The physics underlying the sinusoidal variations were at first a mystery, but Blandford came up with a simple and elegant model to explain the sinusoidal shape of the variations.
"We knew this beautiful sine wave had to be telling us something important about the system," Readhead says. "Roger's model shows us that it is simply the orbital motion that does this. Before Roger worked it out, nobody had figured out that a binary with a relativistic jet would have a light curve that looked like this."
Kiehlmann says their "study provides a blueprint for how to search for such blazar binaries in the future."
More information:
S. O'Neill et al, The Unanticipated Phenomenology of the Blazar PKS 2131–021: A Unique Supermassive Black Hole Binary Candidate, The Astrophysical Journal Letters (2022). DOI: 10.3847/2041-8213/ac504b
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Colossal black holes locked in dance at heart of galaxy (2022, February 23)
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NASA’s ambitious $10 billion James Webb Space Telescope launched from the European Space Agency’s Arianespace ELA-3 launch complex and began its journey to outer space in late December 2021. After traveling over 1 million miles since its initial launch, the James Webb Space Telescope reached L2, the second sun-Earth Lagrange point, on Jan. 24.
Lagrange points, in solar system exploration, are defined as “positions in space where objects sent there tend to stay put.” With its arrival to L2, the telescope will remain in place due to gravitational stability and close proximity to both Earth and the sun. In this setting, it will also be able to orbit the sun, from a million miles away, at the same pace of Earth’s own orbit.
As a project initiated by NASA, the telescope has since become a hallmark international collaboration between the European Space Agency (ESA) and Canadian Space Agency (CSA). NASA is responsible for the Webb mission, taking note of photos, statistics and other areas of progress of the telescope on a daily basis. The ESA has provided the near infrared spectrograph, mid-infrared instrument optics assembly and Ariane launch vehicle for the project while the CSA has provided equipment, such as the fine guidance sensor/near infrared imager and slitless spectrograph.
With the legacy of the Hubble Space Telescope, the James Webb Space Telescope’s mission hopes to build upon the findings of Hubble with revolutionized imaging capabilities. However, the biggest difference between the two powerful machines lies in the type of light they can absorb.
Since the James Webb Space Telescope will be farther away from Earth than Hubble, the light the Webb telescope will come into contact with is more red shifted and is classified as infrared light. With four instruments to absorb such light, the telescope will be able to capture clear images of galaxies that encompass hidden stars and planets that emit infrared light. Through its folding telescope design, the tennis-court size sunshield will provide necessary protection from heat and light from the sun on one side while the 21.3 feet segmented mirror captures infrared light on the other side.
With its longer wavelength coverage and improved sensitivity capacity, the purpose of the telescope’s mission can be described and divided into four categories: first light and reionization, an observation on the assembly of galaxies, the birth of stars and protoplanetary systems, and the origins of life.
Oftentimes, telescopes are described as time machines because they can observe events from the past. Based on the distance of the object or system that is being studied, a telescope can display how those systems became what they are today. Since the farthest stars and galaxies have high redshifts that are only able to be seen through the near and mid-infrared light component of the electromagnetic spectrum, the James Webb Space Telescope will aid astronomers in understanding how the first stars and galaxies were formed over a billion years ago.
As our solar system continues to develop, the telescope will also provide more information on other planetary systems within the universe that are being born today. With the progression of space and life exploration on planets like Mars, the telescope will aim to continue researching the possible building blocks of life in other parts of our universe as well.
At UCI, professors like Dr. Asantha Cooray, who teaches physics and astronomy for the School of Physical Sciences, are fueling the field of infrared astronomy with more knowledge and research findings on the subject altogether.
In comparison, the James Webb Space Telescope is estimated to last a minimum of five years in space. Due to its successful launch in which the Ariane five rocket saved onboard fuel, NASA believes it has the ability to remain in orbit for more than 10 years. Its first images are expected to be generated by the summer of 2022.
To read more about the science tools encompassing the telescope, how it works in space and receive updates through its mission timeline, visit the James Webb Space Telescope website.
Korintia Espinoza is a STEM staff writer for the winter 2022 quarter. She can be reached at korintie@uci.edu.
A spectacular head-on collision between two galaxies fueled the unusual triangular-shaped star-birthing frenzy, as captured in a new image from NASA's Hubble Space Telescope. The interacting galaxy duo is collectively called Arp 143. The pair contains the glittery, distorted, star-forming spiral galaxy NGC 2445 at right, along with its less flashy companion, NGC 2444 at left. Credit: NASA, ESA, STScI, Julianne Dalcanton (Center for Computational Astrophysics / Flatiron Inst. and University of Washington)
A spectacular head-on collision between two galaxies fueled the unusual triangular-shaped star-birthing frenzy, as captured in a new image from NASA's Hubble Space Telescope.
The interacting galaxy duo is collectively called Arp 143. The pair contains the glittery, distorted, star-forming spiral galaxy NGC 2445 at right, along with its less flashy companion, NGC 2444 at left.
Astronomers suggest that the galaxies passed through each other, igniting the uniquely shaped star-formation firestorm in NGC 2445, where thousands of stars are bursting to life on the right-hand side of the image. This galaxy is awash in starbirth because it is rich in gas, the fuel that makes stars. However, it hasn't yet escaped the gravitational clutches of its partner NGC 2444, shown on the left side of the image. The pair is waging a cosmic tug-of-war, which NGC 2444 appears to be winning. The galaxy has pulled gas from NGC 2445, forming the oddball triangle of newly minted stars.
"Simulations show that head-on collisions between two galaxies is one way of making rings of new stars," said astronomer Julianne Dalcanton of the Flatiron Institute's Center for Computational Astrophysics in New York and the University of Washington in Seattle. "Therefore, rings of star formation are not uncommon. However, what's weird about this system is that it's a triangle of star formation. Part of the reason for that shape is that these galaxies are still so close to each other and NGC 2444 is still holding on to the other galaxy gravitationally. NGC 2444 may also have an invisible hot halo of gas that could help to pull NGC 2445's gas away from its nucleus. So they're not completely free of each other yet, and their unusual interaction is distorting the ring into this triangle."
NGC 2444 is also responsible for yanking taffy-like strands of gas from its partner, stoking the streamers of young, blue stars that appear to form a bridge between the two galaxies.
Credit: NASA's Goddard Space Flight Center
These streamers are among the first in what appears to be a wave of star formation that started on NGC 2445's outskirts and continued inward. Researchers estimate the streamer stars were born between about 50 million and 100 million years ago. But these infant stars are being left behind as NGC 2445 continues to pull slowly away from NGC 2444.
Stars no older than 1 million to 2 million years are forming closer to the center of NGC 2445. Hubble's keen sharpness reveals some individual stars. They are the brightest and most massive in the galaxy. Most of the brilliant blue clumps are groupings of stars. The pink blobs are giant, young, star clusters still enshrouded in dust and gas.
Although most of the action is happening in NGC 2445, it doesn't mean the other half of the interacting pair has escaped unscathed. The gravitational tussle has stretched NGC 2444 into an odd shape. The galaxy contains old stars and no new starbirth because it lost its gas long ago, well before this galactic encounter.
"This is a nearby example of the kinds of interactions that happened long ago. It's a fantastic sandbox to understand star formation and interacting galaxies," said Elena Sabbi of the Space Telescope Science Institute in Baltimore, Maryland.
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This artist's impression shows how WASP-121b is getting bent out of shape.
NASA/ESA/J. Olmsted (STScl)
The exoplanet WASP-121b, which resides about 900 light-years from Earth, is an egg-shaped scorcher. Temperatures on the planet's day side can reach up to 4,600 degrees Fahrenheit. It's so hot that heavy metal elements, like iron and magnesium, exist as gases and are constantly streaming out of the atmosphere and into space.
But the planet's night side has, until now, remained in the dark (sorry).
Telescopes at the South African Astronomical Observatory discovered WASP-121b in 2015. The planet, which is a little bigger and heavier than Jupiter, is on the verge of being ripped apart by the gravitational forces of its home star, known as WASP 121. It makes a full orbit of that star once every 1.3 days and is tidally locked -- one side is perpetually bathed in starlight, the other is forever staring out into space.
"This is one of the most extreme systems we have," says Ben Montet, an astrophysicist at the University of New South Wales who was not affiliated with the study. He notes its extremely hot day side is hotter than some stars.
Hubble has been instrumental in learning more about WASP-121b's atmosphere, first revealing in 2017 that it contains water vapor and suggesting the planet contains a stratosphere -- a first. The new study turned to Hubble once again and reveals, in detail, the planet's atmosphere and how the temperature change from day to night affects the elements that fly around the hot Jupiter's upper layers.
Hubble trained its cosmic eye on WASP-121b for two full orbits of its home star, once in 2018 and a second time a year later. Hubble's "eye" collects light data, which scientists can break down into wavelengths that correspond to particular elements and molecules. The team looked for water vapor on the night side of WASP-121b and used it to determine how "cold" the dark side gets.
The answer: The night side gets down to about 2,200 degrees Fahrenheit. Not very cold in Earth terms, but super cold compared to WASP-121b's day side. They were also able to calculate wind speeds on the planet exceeding 11,000 miles per hour.
With this information, the team then modeled what other kinds of chemicals and molecules might exist in the exoplanetary atmosphere. They found the night side likely contains exotic clouds made of iron and titanium, as well as corundum, the same mineral that is found in ruby and sapphire gemstones on Earth. The clouds get whipped from the night side to the day side and find themselves in an extremely hostile environment where they condense and fall, like rain.
"All of these exotic compounds are raining out of the planet's atmosphere," said Montet. Essentially, if you could survive in WASP-121b, you might see the liquid version of rubies and sapphires fall out of the sky.
NASA's recently launched James Webb Space Telescope is expected to observe WASP-121b later this year. The telescope will assess the planet in infrared and analyze its atmospheric chemistry, allowing scientists to get a better understanding of how hot Jupiters might form and exactly what its atmosphere is composed of.
A SpaceX Falcon 9 rocket lifts off from launch complex 39A at the Kennedy Space Center in Florida on November 15, 2020. (Photo by Gregg Newton / AFP)
On the 3rd of February, SpaceX (Elon Musk’s aerospace company) launched 49 satellites to add to their Starlink internet mega constellation. A day later, 40 of those newly launched satellites were doomed – expected to be out of commission due to geomagnetic storms.
A SpaceX Falcon 9 rocket lifts off from launch complex 39A at the Kennedy Space Center in Florida on November 15, 2020. (Photo by Gregg Newton / AFP)
For those who aren’t familiar with Starlink, space.com describes it as “a satellite network developed by the private spaceflight company SpaceX to provide low-cost internet to remote locations.” When the first set of satellites were launched in 2019, there were hopes to have as many as 42,000 table-sized satellites in a mega constellation floating in low orbit. Today in early 2022, there are more than 1,800 functional satellites in Starlink, with more to come soon.
However, when a SpaceX rocket launched 49 satellites to join Starlink last February 3, 40 of those satellites were hit by a geomagnetic storm just a day later. These storms are intense solar winds that can affect the atmospheric density and thus also affects satellites in low orbit.
SpaceX’s satellites get launched around 130 miles above Earth, but it turns out that the geomagnetic storms affect the atmosphere in those heights. The storm increased the atmospheric drag up to 50 percent, causing most of the newly launched satellites to veer way off course – going too high and eventually falling out of orbit. Those unlucky 40 satellites will float around like space debris, but according to SpaceX, they won’t collide with other satellites.
It is important to note that the Starlink project and megaconstellations, in general, have faced criticisms from astronomers due to the light that they emit. These large amounts of light can interfere with galactical observation. Piero Benvenuti, Former General Secretary of the International Astronomical Union (IAU), had this to say about megaconstellations:
“In the past, the main source of interference was the light pollution produced by the urban illumination, the so-called artificial light at night. But more recently, the impact of the large constellations of communication satellites became a more serious concern because of their ubiquitous invasiveness.”
The United States' human spaceflight program got a much-needed shot in the arm 60 years ago today.
On Feb. 20, 1962, NASA astronaut John Glenn launched from Florida's Cape Canaveral inside a tiny capsule named Friendship 7. The Mercury spacecraft circled Earth three times, ultimately splashing down near the Turks and Caicos Islands four hours and 55 minutes after liftoff.
It was the United States' first-ever crewed orbital spaceflight — a milestone that the nation's Cold War rival, the Soviet Union, had notched 10 months earlier, with the landmark mission of Yuri Gagarin.
The Friendship 7 capsule carrying NASA astronaut John Glenn launches on the United States' first crewed orbital spaceflight on Feb. 20, 1962. (Image credit: NASA)
The U.S. played catch-up quite a bit during the early days of the Cold War space race. For example, the Soviet Union was the first country to launch a satellite to orbit (Sputnik 1, in October 1957), the first to send an animal to orbit (Laika the dog, in November 1957) and the first to return living creatures to Earth from an orbital mission (a menagerie headlined by the dogs Belka and Strelka, in August 1960; Laika did not survive her flight).
And then there was Gagarin's epic mission. On April 12, 1961, the cosmonaut became the first person to reach space and also the first to orbit Earth, dealing another blow to the psyche of American policymakers, national security officials and the public at large.
The jolt went beyond mere embarrassment, for the Soviet Union seemed to be significantly ahead of the U.S. in a key area of technological capability. Rockets carrying animals or people to space aren't so different from missiles outfitted with nuclear warheads.
So Glenn's 5-hour jaunt off the planet was huge for NASA and the nation.
"His flight on Friendship 7 on Feb. 20, 1962, showed the world that America was a serious contender in the space race with the Soviet Union," NASA officials wrote in a profile of Glenn a few years ago. "It also made Glenn an instant hero."
The U.S. built on that momentum, ultimately winning the space race's grand prize with the successful completion of the Apollo 11 moon mission in July 1969.
And Glenn, one of NASA's original Mercury 7 astronauts, didn't exactly fade into obscurity after the hoopla surrounding his landmark flight died down. He retired from NASA in January 1964 but returned to public service a decade later, winning election to the U.S. Senate from Ohio in 1974. He won re-election in 1980, 1986 and 1992, serving a total of four terms in the body.
"He was considered one of the Senate's leading experts on technical and scientific matters, and won wide respect for his work to prevent the spread of weapons of mass destruction," NASA officials wrote in the profile. "He took pride in using his position on the Governmental Affairs Committee to root out waste in government and to clean up the nation's nuclear materials production plants."
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And Glenn ended up going to orbit again. In October 1998, at the age of 77, he spent nine days aboard the space shuttle Discovery, becoming the oldest person ever to travel to the final frontier. That record stood until July 2021, when aviation pioneer Wally Funk went to suborbital space aboard Blue Origin's New Shepard spacecraft at the age of 82. "Star Trek" actor William Shatner then wrested the title from Funk just three months later, flying on a New Shepard mission at 90.
New Shepard, by the way, is named after Glenn's Mercury 7 colleague Alan Shepard, who in May 1961 became the first American to reach space. Shepard flew on a 15-minute suborbital mission, quite a different experience than Glenn's orbital trek.
Glenn died on Dec. 8, 2016, at the age of 95. His long, productive and inspiring life left a large imprint on the history books and the American consciousness. NASA's Glenn Research Center in Ohio is named after the pioneering astronaut, for instance. And his Freedom 7 capsule is on display at the Stephen F. Udvar-Hazy Center of the Smithsonian Institution's National Air and Space Museum in Virginia.
Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or on Facebook.
