TL;DR
- The nearest exoplanets to us provide the best opportunities for study, including searching for evidence of life outside the Solar System. Astronomers have now detected a system of super-Earth planets orbiting the nearby star Gliese 887, the brightest red dwarf star in the sky. The newly discovered super-Earths lie close to the red dwarf’s habitable zone, where water can exist in liquid form.
- Astronomers have discovered the second-most distant quasar ever found. It is the first quasar to receive an indigenous Hawaiian name, Poniua’ena. Data show the supermassive black hole powering Poniua’ena is surprisingly massive, challenging current theories of how supermassive black holes formed and grew in the young universe.
- The sun’s convection zone plays a key role in the generation and evolution of the Sun’s magnetic field. Analyzing data sets spanning more than 20 years, researchers have obtained the most comprehensive picture of the north-south flow of plasma in the convection zone ever. The flow goes around the convection zone in each hemisphere in about 22 years.
- Astronomers study stars and planets much younger than the Sun to learn about past events that shaped the Solar System and Earth. Most of these stars are far enough away to make observations challenging, even with the largest telescopes. But now this is changing.
- The young star HBC 672 is known by its nickname of Bat Shadow because of its wing-like shadow feature. The NASA/ESA Hubble Space Telescope has now observed a curious ‘’flapping’’ motion in the shadow of the star’s disc for the first time. The star resides in a stellar nursery called the Serpens Nebula, about 1300 light-years away.
- A new study suggests that Pluto and other large Kuiper belt objects started out with liquid oceans which have been slowly freezing over time.
- Researchers have discovered what is either the heaviest known neutron star, or the lightest black hole.
- The Gemini Planet Imager on the Gemini South telescope looked at 104 young, nearby stars, 10–100 million years old, in search of debris disks. It found 26, 25 of which had inner holes indicating a planet. These debris rings, similar to the Kuiper Belt in our solar system, display amazing diversity in size and distance from the star. Such studies help astronomers understand the formation of planets and shed light on our system’s early history.
- Astronomers have seen what appears to the first light ever detected from a black hole merger.
- In a critical step toward creating a global quantum communications network, researchers have generated and detected quantum entanglement onboard a CubeSat nanosatellite weighing less than 2.6 kilograms and orbiting the Earth.
- The first all-sky X-ray map to be released in 30 years reveals new wonders of the hot and energetic universe.
- NASA scientist simulates sunsets on other worlds.
- Upcoming industry events. And more!
Space industry in numbers
Last summer, the Space Foundation published the second-quarter findings of its 2019 issue of The Space Report, revealing that:
- The global space economy grew 8.1% in 2018 to USA 414.75 billion, exceeding USD 400 billion for the first time.
- Global launches in 2018 increased by 46% over the number of launches a decade ago.
- Global launches in 2018 exceeded 100 for the first time since 1990.
Analysts at Morgan Stanley and Goldman Sachs have predicted that economic activity in space will become a multi-trillion-dollar market in the coming decades. Morgan Stanley’s Space Team estimates that the roughly USD 350 billion global space industry could surge to over USD 1 trillion by 2040.
Space industry news
China Reaches New Milestone in Space-Based Quantum Communications: The nation’s Micius satellite successfully established an ultrasecure link between two ground stations separated by more than 1,000 kilometers
Space Force more receptive to reusable rockets as it continues to review SpaceX missions
MDA to build robotic arm for lunar Gateway
Northrop Grumman receives $222 million contract to update aging missile-warning satellites
NOAA to buy commercial radio occultation data for operations
ESA starts search for next director general
ASTRA wins contract to study weather cubesat constellation
Ball Aerospace wins NOAA space weather contract
HASC Chairman adds $150 million in NDAA for space launch technology development
SpaceShipTwo makes second glide flight at Spaceport America
Maxar buying 3D geospatial company Vricon for $140 million
Space Adventures signs contract for Soyuz flight with spacewalk option
NGA signs research and development agreement with Capella
NASA using Demo-2 commercial crew astronauts to support ISS spacewalks
NASA expects to cover JWST launch slip with budget reserves
Griffin’s departure stirs questions about the future of the Space Development Agency
Relativity wins Iridium contract, selects West Coast launch site
New NASA Earth science director outlines challenges to implementing decadal survey
SASC NDAA authorizes $250 million for Air Force R&D partnerships with launch industry
NASA takes initial steps to fly personnel on commercial suborbital vehicles
Coalition of GPS user groups joins fight against FCC’s Ligado decision
FCC makes headway in legal battle with ABS, Hispasat and Arsat over C-band auction
Undersecretary of Defense Mike Griffin and deputy Lisa Porter stepping down
York Space and MSU Denver extend partnership through Air Force contract
Redwire acquires Made In Space
SkyWatch and AgIntegrated offer satellite imagery for precision agriculture
White House official recommends slow approach to high-speed suborbital transportation
HASC Strategic Forces advances its section of the 2021 NDAA
Eutelsat to order single replacement C-band satellite for FCC spectrum clearing
Thermal materials startup Carbice finds foothold in space industry
Virgin Galactic to work with NASA on private orbital spaceflight experiences
Space exploration
NASA Scientist Simulates Sunsets on Other Worlds
Have you ever wondered what a sunset on Uranus might look like?
As you can see in the animation above, a Uranian sunset is a rich azure that fades into royal blue with hints of turquoise. This blue-green color comes from the interaction of sunlight with the planet’s atmosphere. When sunlight — which is made up of all the colors of the rainbow — reaches Uranus’s atmosphere, hydrogen, helium and methane absorb the longer-wavelength red portion of the light. The shorter-wavelength blue and green portions of light get scattered as photons bounce off the gas molecules and other particles in the atmosphere. A similar phenomenon makes Earth’s sky appear blue on a clear day.
Geronimo Villanueva, a planetary scientist from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, created the sunset simulations while building a computer modeling tool for a possible future mission to Uranus, an icy-cold planet in the outer solar system. One day, a probe could descend through the Uranian atmosphere, with Villanueva’s tool helping scientists interpret the measurements of light that will reveal its chemical makeup.
To validate the accuracy of his tool, Villanueva simulated known sky colors of Uranus and other worlds, some of which are shown above. The animations show the Sun appearing to set from the perspective of someone on these worlds. As these worlds rotate away from the light of the Sun, which is what happens during a sunset, photons get scattered in different directions depending on the energy of the photons and the types of molecules in the atmospheres. The result is a lovely palette of colors that would be visible to those standing on these worlds.
The animations show all-sky views as if you were looking up at the sky through a super wide camera lens from Earth, Venus, Mars, Uranus, and Titan. The white dot represents the location of the Sun. The halo of light seen towards the end of the sunset on hazy Earth is produced because of the way light is scattered by particles, including dust or fog, that are suspended in the clouds. The same is true of the Martian halo. Also on Mars, the sunset turns from a brownish color to a blueish because the Martian dust particles scatter the blue color more effectively.
These sky simulations are now a new feature of a widely used online tool called the Planetary Spectrum Generator, which was developed by Villanueva and his colleagues at NASA Goddard. The generator helps scientists replicate how light is transferred through the atmospheres of planets, exoplanets, moons, and comets in order to understand what their atmospheres and surfaces are made of.
For a less technical and more contemplative perspective on alien sunsets, check out this short movie:
Pōniuā’ena: A Luminous z=7.5 Quasar Hosting a 1.5 Billion Solar Mass Black Hole
by Jinyi Yang, Feige Wang, Xiaohui Fan, Joseph F. Hennawi, Frederick B. Davies, Minghao Yue, Eduardo Banados, Xue-Bing Wu, Bram Venemans, Aaron J. Barth, Fuyan Bian, Konstantina Boutsia, Roberto Decarli, Emanuele Paolo Farina, Richard Green, Linhua Jiang, Jiang-Tao Li, Chiara Mazzucchelli, Fabian Walter in Astrophysical Journal Letters
Astronomers have discovered the second-most distant quasar ever found using three Maunakea Observatories in Hawai’i: W. M. Keck Observatory, the international Gemini Observatory, a Program of NSF’s NOIRLab, and the University of Hawai’i-owned United Kingdom Infrared Telescope (UKIRT). It is the first quasar to receive an indigenous Hawaiian name, Poniua’ena, which means “unseen spinning source of creation, surrounded with brilliance” in the Hawaiian language.
Poniua’ena is only the second quasar yet detected at a distance calculated at a cosmological redshift greater than 7.5 and it hosts a black hole twice as large as the other quasar known in the same era. The existence of these massive black holes at such early times challenges current theories of how supermassive black holes formed and grew in the young universe.
Quasars are the most energetic objects in the universe powered by their supermassive black holes and since their discovery, astronomers have been keen to determine when they first appeared in our cosmic history. By systematically searching for these rare objects in wide-area sky surveys, astronomers discovered the most distant quasar (named J1342+0928) in 2018 and now the second-most distant, Poniua’ena (or J1007+2115, at redshift 7.515). The light seen from Poniua’ena traveled through space for over 13 billion years since leaving the quasar just 700 million years after the Big Bang.
Spectroscopic observations from Keck Observatory and Gemini Observatory show the supermassive black hole powering Poniua’ena is 1.5 billion times more massive than our Sun. Poniua’ena is the most distant object known in the universe hosting a black hole exceeding one billion solar masses,” said Jinyi Yang, a postdoctoral research associate at the Steward Observatory of the University of Arizona and lead author of the study. For a black hole of this size to form this early in the universe, it would need to start as a 10,000 solar mass “seed” black hole about 100 million years after the Big Bang, rather than growing from a much smaller black hole formed by the collapse of a single star.
“How can the universe produce such a massive black hole so early in its history?” said Xiaohui Fan, Regents’ professor and associate department head of the Department of Astronomy at the University of Arizona. “This discovery presents the biggest challenge yet for the theory of black hole formation and growth in the early universe.”
Current theory holds the birth of stars and galaxies as we know them started during the Epoch of Reionization, beginning about 400 million years after the Big Bang. The growth of the first giant black holes is thought to have occurred during that same era in the universe’s history.
The discovery of quasars like Poniua’ena, deep into the reionization epoch, is a big step towards understanding this process of reionization and the formation of early supermassive black holes and massive galaxies. Poniua’ena has placed new and important constraints on the evolution of the matter between galaxies (intergalactic medium) in the reionization epoch.
“Poniua’ena acts like a cosmic lighthouse. As its light travels the long journey towards Earth, its spectrum is altered by diffuse gas in the intergalactic medium which allowed us to pinpoint when the Epoch of Reionization occurred,” said co-author Joseph Hennawi, a professor in the Department of Physics at the University of California, Santa Barbara.
Yang’s team first detected Poniua’ena as a possible quasar after combing through large-area surveys such as the UKIRT Hemisphere Survey and data from the University of Hawai’i Institute for Astronomy’s Pan-STARRS1 telescope on the Island of Maui.
In 2019, the researchers observed the object using Gemini Observatory’s GNIRS instrument as well as Keck Observatory’s Near Infrared Echellette Spectrograph (NIRES) to confirm the existence of Poniua’ena.
“The preliminary data from Gemini suggested this was likely to be an important discovery. Our team had observing time scheduled at Keck just a few weeks later, perfectly timed to observe the new quasar using Keck’s NIRES spectrograph in order to confirm its extremely high redshift and measure the mass of its black hole,” said co-author Aaron Barth, a professor in the Department of Physics and Astronomy at the University of California, Irvine.
First all-sky map from eRosita
The first all-sky X-ray map to be released in 30 years reveals new wonders of the hot and energetic universe
The eRosita space telescope, which launched in July 2019, has completed its first full sweep across the sky, mapping both hemispheres and cataloging more than 1 million X-ray sources. This is only the first all-sky map to be delivered: The mission plans to create seven more maps, combining them to achieve unprecedented sensitivity to the whole X-ray sky.
One of the key science goals of this mission is to find new galaxy clusters, more distant than ones discovered before, and use them to track the growth of cosmic structure over time. But the multiple maps enable the mission to study other sources, too, including ephemeral ones like flares of light coming from around black holes.
The eRosita telescope flies on the Spektrum-Röntgen-Gamma spacecraft, a joint German-Russian mission that operates at the L2 Lagrange point, 1.5 million kilometers (900,000 miles) away on the opposite side of Earth from the Sun. As the telescope rotates, it scans the X-ray sky with seven cameras, taking exposures of 150 to 200 seconds over most of the sky. (The poles have longer exposure times.) The images record photon energies between 300 and 5,000 electron volts.
In half a year, the mission has already doubled the number of known sources collected since the start of X-ray astronomy in the 1960s. Some of these sources are pointed out below:
This sky is decidedly different from the one we see at night. Only the hottest gases and the most extreme and active sources emit X-rays. While the mission sees some stars, whose magnetic activity creates X-ray-emitting flares, most of the sources are active galactic nuclei, in which hot gases swirl into the maw of supermassive black holes. Other X-ray sources include the hot gases released in supernovae explosions and the far more tenuous gas in and around our galaxy.
The active galaxies that pepper the sky — and account for more than three-quarters of the tally — outnumber eRosita’s true quarry: galaxy clusters. The hot gas spread out in the vast space between galaxies emits X-rays. So by looking for these X-ray blobs, the telescope can find galaxy clusters back to when the universe was only half its current age. Galaxy clusters mark junctures in the cosmic web, so by plotting a large number of clusters over billions of years, astronomers can watch large-scale structures evolve. With more than 20,000 clusters spotted so far, the mission is on track to find more than 100,000 when its surveys are complete.
The researchers continue to analyze the first results even as the mission begins its second round of sky-mapping. The eRosita mission will start making its data public around the summer of 2022, says eRosita principal investigator Peter Predehl (Max Planck Institute for Extraterrestrial Physics, Germany).
Meridional flow in the Sun’s convection zone is a single cell in each hemisphere
by Laurent Gizon et al. in Science
Solar activity fluctuates in a rhythm of about eleven years, which is reflected among other things in the frequency of sunspots. A complete magnetic period lasts 22 years. Scientists have long been puzzling over what causes this cycle. It must be related to the conditions beneath the “skin” of our star: A layer of hot plasma — electrically-conductive gas — extends from the surface to 200,000 kilometers below. The plasma within this convection zone is constantly in motion.
A team of scientists from the Max Planck Institute for Solar System Research, the University of Göttingen and New York University Abu Dhabi has now succeeded in drawing the most comprehensive picture of the plasma flows in nort-south-direction to date. The researchers have found a remarkably simple flow geometry: the plasma describes a single turnover in each solar hemisphere, which lasts for about 22 years. In addition, the flow in the direction of the equator at the bottom of the convection zone causes spots to form closer and closer to the equator during the solar cycle.
The number of sunspots on the visible solar surface varies; sometimes there are more, sometimes fewer. The distance between two sunspot maxima is about eleven years, after 22 years the sunspots are again magnetically polarized in the same way. During the maximum not only large sunspots appear, but also active regions. In addition, impressive arcs of hot plasma reach far into the solar atmosphere, particles and radiation are hurled into space in violent eruptions. At the activity minimum, however, the sun calms down noticeably.
“Over the course of a solar cycle, the meridional flow acts as a conveyor belt that drags the magnetic field along and sets the period of the solar cycle,” says Prof. Dr. Laurent Gizon, MPS Director and first author of the new study. “Seeing the geometry and the amplitude of motions in the solar interior is essential to understanding the Sun’s magnetic field,” he adds. To this end, Gizon and his team used helioseismology to map the plasma flow below the Sun’s surface.
Helioseismology is to solar physics what seismology is to geophysics. Helioseismologists use sound waves to probe the Sun’s interior, in much the same way geophysicists use earthquakes to probe the interior of the Earth. Solar sound waves have periods near five minutes and are continuously excited by near surface convection. The motions associated with solar sound waves can be measured at the Sun’s surface by telescopes on spacecrafts or on the ground.
In this study, Gizon and his team used observations of sound waves at the surface that propagate in the north-south direction through the solar interior. These waves are perturbed by the meridional flow: they travel faster along the flow than against the flow. These very small travel-time perturbations (less than 1 second) were measured very carefully and were interpreted to infer the meridional flow using mathematical modeling and computers.
Because it is small, the meridional flow is extremely difficult to see in the solar interior. “The meridional flow is much slower than other components of motion, such as the Sun’s differential rotation,” Gizon explains. The meridional flow throughout the convection zone is no more than its maximum surface value of 50 kilometers per hour. “To reduce the noise level in the helioseismic measurements, it is necessary to average the measurements over very long periods of time,” says Dr. Zhi-Chao Liang of MPS.
The team of scientists analyzed, for the first time, two independent very long time series of data. One was provided by SOHO, the oldest solar observatory in space which is operated by ESA and NASA. The data taken by SOHO’s Michelson Doppler Imager (MDI) covers the time from 1996 until 2011. A second independent data set was provided by the Global Oscillation Network Group (GONG), which combines six ground-based solar telescopes in the USA, Australia, India, Spain, and Chile to offer nearly continuous observations of the Sun since 1995.
“The international solar physics community is to be commended for delivering multiple datasets covering the last two solar cycles,” says Dr. John Leibacher, a former director of the GONG project. “This makes it possible to average over long periods of time and to compare answers, which is absolutely essential to validate inferences,” he adds.
Gizon and his team find the flow is equatorward at the base of the convection zone, with a speed of only 15 kilometers per hour (running speed). The flow at the solar surface is poleward and reaches up to 50 kilometers per hour. The overall picture is that the plasma goes around in one gigantic loop in each hemisphere. Remarkably, the time taken for the plasma to complete the loop is approximately 22 years — and this provides the physical explanation for the Sun’s eleven-year cycle.
Furthermore, sunspots emerge closer to the equator as the solar cycle progresses, as is seen in the butterfly diagram. “All in all, our study supports the basic idea that the equatorward drift of the locations where sunspots emerge is due to the underlying meridional flows,” says Dr. Robert Cameron of MPS. “It remains to be understood why the solar meridional flow looks like it does, and what role the meridional flow plays in controlling magnetic activity on other stars” adds Laurent Gizon.
A planet within the debris disk around the pre-main-sequence star AU Microscopii
by Plavchan, P., Barclay, T., Gagné, J. et al. in Nature
Astronomers study stars and planets much younger than the Sun to learn about past events that shaped the Solar System and Earth. Most of these stars are far enough away to make observations challenging, even with the largest telescopes. But now this is changing.
University of Hawai’i at Manoa astronomers are part of an international team that recently discovered an infant planet around a nearby young star. The discovery was reported Wednesday in the international journal Nature.
The planet is about the size of Neptune, but, unlike Neptune, it is much closer to its star, taking only eight and a half days to complete one orbit. It is named “AU Mic b” after its host star, AU Microscopii, or “AU Mic” for short. The planet was discovered using the NASA TESS planet-finding satellite, as it periodically passed in front of AU Mic, blocking a small fraction of its light. The signal was confirmed by observations with another NASA satellite, the Spitzer Space Telescope, and with the NASA Infrared Telescope Facility (IRTF) on Maunakea. The observations on Hawai’i Island used a new instrument called iSHELL that can make very precise measurements of the motion of a star like AU Mic. These measurements revealed a slight wobble of the star, as it moves in response to the gravitational pull of the planet. It confirmed that AU Mic b was a planet and not a companion star, which would cause a much larger motion.
AU Mic and its planet are about 25 million years young, and in their infancy, astronomically speaking. AU Mic is also the second closest young star to Earth. It is so young that dust and debris left over from its formation still orbit around it. The debris collides and breaks into smaller dust particles, which orbit the star in a thin disk. This disk was detected in 2003 with the UH 88-inch telescope on Maunakea. The newly-discovered planet orbits within a cleared-out region inside the disk.
“This is an exciting discovery, especially as the planet is in one of the most well-known young star systems, and the second-closest to Earth. In addition to the debris disk, there is always the possibility of additional planets around this star. AU Mic could be the gift that keeps on giving,” said Michael Bottom, an Assistant Astronomer at the UH Institute for Astronomy.
“Planets, like people, change as they mature. For planets this means that their orbits can move and the compositions of their atmospheres can change. Some planets form hot and cool down, and unlike people, they would become smaller over time. But we need observations to test these ideas and planets like AU Mic b are an exceptional opportunity,” said Astronomer Eric Gaidos, a professor in the Department of Earth Sciences at UH M?noa.
AU Mic is not only much younger than the Sun, it is considerably smaller, dimmer and redder. It is a “red dwarf,” the most numerous type of star in the galaxy. The TESS satellite is also discovering Earth-sized and possibly habitable planets around older red dwarfs, and what astronomers learn from AU Mic and AU Mic b can be applied to understand the history of those planets.
“AU Mic b, and any kindred planets that are discovered in the future, will be intensely studied to understand how planets form and evolve. Fortuitously, this star and its planet are on our cosmic doorstep. We do not have to venture very far to see the show,” Gaidos explained. He is a co-author on another five forthcoming scientific publications that have used other telescopes, including several on Maunakea, to learn more about AU Mic and its planet.
AU Mic appears low in the summer skies of Hawai’i but you’ll need binoculars to see it. Despite its proximity, the fact that it is a dim red star means it is too faint to be seen with the unaided eye.
Variability of the Great Disk Shadow in Serpens
by Klaus M. Pontoppidan, Joel D. Green, Tyler A. Pauly, Colette Salyk, Joseph DePasquale in The Astrophysical Journal
The young star HBC 672 is known by its nickname of Bat Shadow because of its wing-like shadow feature. The NASA/ESA Hubble Space Telescope has now observed a curious ‘’flapping’’ motion in the shadow of the star’s disc for the first time. The star resides in a stellar nursery called the Serpens Nebula, about 1300 light-years away.
Scientists present dual-epoch Hubble Space Telescope imaging of the great disk shadow in the Serpens star-forming region. The near-infrared images show strong variability of the disk shadow, revealing dynamics of the inner disk on timescales of months. The Great Shadow is projected onto the Serpens reflection nebula by an unresolved protoplanetary disk surrounding the young intermediate-mass star SVS2/CK3/EC82. Since the shadow extends out to a distance of at least 17,000 au, corresponding to a light-travel time of 0.24 yr, the images may reveal detailed changes in the disk scale height and position angle on timescales as short as a day, corresponding to the angular resolution of the images, and up to the 1.11 yr span between two observing epochs. They present a basic retrieval of temporal changes in the disk density structure, based on the images. Researchers find that the inner disk changes position angle on timescales of months, and that the change is not axisymmetric, suggesting the presence of a non-axisymmetric dynamical forcing on ~1 au size scales. They consider two different scenarios, one in which a quadrupolar disk warp orbits the central star, and one in which an unequal-mass binary orbiting out of the disk plane displaces the photocenter relative to the shadowing disk. Continued space-based monitoring of the great disk shadow is required to distinguish between these scenarios, and could provide unique and detailed insight into the dynamics of inner protoplanetary disks not available through other means.
A multiple planet system of super-Earths orbiting the brightest red dwarf star GJ887
by Jeffers et al. in Science
The nearest exoplanets to us provide the best opportunities for study, including searching for evidence of life outside the Solar System. Astronomers have now detected a system of super-Earth planets orbiting the nearby star Gliese 887, the brightest red dwarf star in the sky. The newly discovered super-Earths lie close to the red dwarf’s habitable zone, where water can exist in liquid form.
Exoplanets can interact gravitationally with other objects orbiting the same star, affecting their evolution and stability. Studying these effects requires locating systems with multiple planets. Monitoring the nearby red dwarf star GJ 887, Jeffers et al. detected periodic radial velocity signals, indicating the presence of two planets on orbits with periods of about 9 and 22 days and a further candidate planet (see the Perspective by Davies). The inclinations of the orbits are unknown, so only minimum masses could be determined, but those were consistent with both planets being super-Earths — more massive than Earth but less than Neptune. This system is only 3.3 parsecs from the Sun, which should facilitate follow-up with other techniques.
The closet exoplanets to the Sun provide opportunities for detailed characterization of planets outside the Solar System. Scientists report the discovery, using radial velocity measurements, of a compact multiplanet system of super-Earth exoplanets orbiting the nearby red dwarf star GJ 887. The two planets have orbital periods of 9.3 and 21.8 days. Assuming an Earth-like albedo, the equilibrium temperature of the 21.8-day planet is ~350 kelvin. The planets are interior to, but close to the inner edge of, the liquid-water habitable zone. We also detect an unconfirmed signal with a period of ~50 days, which could correspond to a third super-Earth in a more temperate orbit. The observations show that GJ 887 has photometric variability below 500 parts per million, which is unusually quiet for a red dwarf.
Evidence for a hot start and early ocean formation on Pluto
by Carver J. Bierson, Francis Nimmo, S. Alan Stern in Nature Geoscience
A new study suggests that Pluto and other large Kuiper belt objects started out with liquid oceans which have been slowly freezing over time.
Pluto is thought to possess a present-day ocean beneath a thick ice shell. It has generally been assumed that Pluto accreted from cold material and then later developed its ocean due to warming from radioactive decay; in this ‘cold start’ scenario, the ice shell would have experienced early compression and more recent extension. Here researchers compare thermal model simulations with geological observations from the New Horizons mission to suggest that Pluto was instead relatively hot when it formed, with an early subsurface ocean. Such a ‘hot start’ Pluto produces an early, rapid phase of extension, followed by a more prolonged extensional phase, which totals ~0.5% linear strain over the last 3.5 Gyr. The amount of second-phase extension is consistent with that inferred from extensional faults on Pluto; they suggest that an enigmatic ridge–trough system recently identified on Pluto is indicative of early extensional tectonics. A hot initial start can be achieved with the gravitational energy released during accretion if the final stage of Pluto’s accretion is rapid. A fast final stage of growth is in agreement with models of the formation of Kuiper belt objects via gravitational collapse followed by pebble accretion, and implies that early oceans may have been common in the interiors of large Kuiper belt objects.
Entanglement demonstration on board a nano-satellite
by Aitor Villar, Alexander Lohrmann, Xueliang Bai, Tom Vergoossen, Robert Bedington, Chithrabhanu Perumangatt, Huai Ying Lim, Tanvirul Islam, Ayesha Reezwana, Zhongkan Tang, Rakhitha Chandrasekara, Subash Sachidananda, Kadir Durak, Christoph F. Wildfeuer, Douglas Griffin, Daniel K. L. Oi, Alexander Ling in Optica
In a critical step toward creating a global quantum communications network, researchers have generated and detected quantum entanglement onboard a CubeSat nanosatellite weighing less than 2.6 kilograms and orbiting the Earth.
Global quantum networks for secure communication can be realized using large fleets of satellites distributing entangled photon pairs between ground-based nodes. Because the cost of a satellite depends on its size, the smallest satellites will be most cost-effective. This Letter describes a miniaturized, polarization entangled, photon-pair source operating on board a nano-satellite. The source violates Bell’s inequality with a Clauser–Horne–Shimony–Holt parameter of 2.60±0.06. This source can be combined with optical link technologies to enable future quantum communication nano-satellite missions.
A Candidate Electromagnetic Counterpart to the Binary Black Hole Merger Gravitational Wave Event GW190521g
by M. J. Graham et al. in Physical Review Letters
Astronomers have seen what appears to the first light ever detected from a black hole merger
A team consisting of scientists from The Graduate Center, CUNY; Caltech’s Zwicky Transient Facility (ZTF); Borough of Manhattan Community College (BMCC); and The American Museum of Natural History (AMNH) spotted what appears to be a flare of light from a pair of coalescing black holes. The event (called S190521g) was first identified by the National Science Foundation’s (NSF) Laser Interferometer Gravitational-wave Observatory (LIGO) and the European Virgo detector on May 21, 2019. As the black holes merged, jiggling space and time, they sent out gravitational waves. Shortly thereafter, scientists at ZTF — which is located at the Palomar Observatory near San Diego — reviewed their recordings of the same the event and spotted what may be a flare of light coming from the coalescing black holes.
“At the center of most galaxies lurks a supermassive black hole. It’s surrounded by a swarm of stars and dead stars, including black holes,” said study coauthor Ford, a professor with the Graduate Center, BMCC and AMNH. “These objects swarm like angry bees around the monstrous queen bee at the center. They can briefly find gravitational partners and pair up but usually lose their partners quickly to the mad dance. But in a supermassive black hole’s disk, the flowing gas converts the mosh pit of the swarm to a classical minuet, organizing the black holes so they can pair up,” she says.
Once the black holes merge, the new, now-larger black hole experiences a kick that sends it off in a random direction, and it plows through the gas in the disk. “It is the reaction of the gas to this speeding bullet that creates a bright flare, visible with telescopes,” said co-author McKernan, an astrophysics professor with The Graduate Center, BMCC and AMNH.
“This supermassive black hole was burbling along for years before this more abrupt flare,” said the study’s lead author Matthew Graham, a research professor of astronomy at Caltech and the project scientist for ZTF. “The flare occurred on the right timescale, and in the right location, to be coincident with the gravitational-wave event. In our study, we conclude that the flare is likely the result of a black hole merger, but we cannot completely rule out other possibilities.”
“ZTF was specifically designed to identify new, rare, and variable types of astronomical activity like this,” said NSF Division of Astronomical Science Director Ralph Gaume. “NSF support of new technology continues to expand how we can track such events.”
Such a flare is predicted to begin days to weeks after the initial splash of gravitational waves produced during the merger. In this case, ZTF did not catch the event right away, but when the scientists went back and looked through archival ZTF images months later, they found a signal that started days after the May 2019 gravitational-wave event. ZTF observed the flare slowly fade over the period of a month.
The scientists attempted to get a more detailed look at the light of the supermassive black hole, called a spectrum, but by the time they looked, the flare had already faded. A spectrum would have offered more support for the idea that the flare came from merging black holes within the disk of the supermassive black hole. However, the researchers say they were able to largely rule out other possible causes for the observed flare, including a supernova or a tidal disruption event, which occurs when a black hole essentially eats a star.
GW190814: Gravitational Waves from the Coalescence of a 23 Solar Mass Black Hole with a 2.6 Solar Mass Compact Object
by R. Abbott et al. in The Astrophysical Journal
Researchers have discovered what is either the heaviest known neutron star, or the lightest black hole
Now, in a new study from the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo detector in Europe, scientists have announced the discovery of an object of 2.6 solar masses, placing it firmly in the mass gap. The object was found on August 14, 2019, as it merged with a black hole of 23 solar masses, generating a splash of gravitational waves detected back on Earth by LIGO and Virgo. A paper about the detection is being published today, June 23, in The Astrophysical Journal Letters.
“We’ve been waiting decades to solve this mystery” says co-author Vicky Kalogera, a professor at Northwestern University. “We don’t know if this object is the heaviest known neutron star, or the lightest known black hole, but either way it breaks a record.”
“This is going to change how scientists talk about neutron stars and black holes,” says co-author Patrick Brady, a professor at the University of Wisconsin, Milwaukee, and the LIGO Scientific Collaboration spokesperson. “The mass gap may in fact not exist at all but may have been due to limitations in observational capabilities. Time and more observations will tell.”
The cosmic merger described in the study, an event dubbed GW190814, resulted in a final black hole about 25 times the mass of the sun (some of the merged mass was converted to a blast of energy in the form of gravitational waves). The newly formed black hole lies about 800 million light-years away from Earth.
Before the two objects merged, their masses differed by a factor of 9, making this the most extreme mass ratio known for a gravitational-wave event. Another recently reported LIGO-Virgo event, called GW190412, occurred between two black holes with a mass ratio of about 4:1.
“It’s a challenge for current theoretical models to form merging pairs of compact objects with such a large mass ratio in which the low-mass partner resides in the mass gap. This discovery implies these events occur much more often than we predicted, making this a really intriguing low-mass object,” explains Kalogera. “The mystery object may be a neutron star merging with a black hole, an exciting possibility expected theoretically but not yet confirmed observationally. However, at 2.6 times the mass of our sun, it exceeds modern predictions for the maximum mass of neutron stars, and may instead be the lightest black hole ever detected.”
When the LIGO and Virgo scientists spotted this merger, they immediately sent out an alert to the astronomical community. Dozens of ground- and space-based telescopes followed up in search of light waves generated in the event, but none picked up any signals. So far, such light counterparts to gravitational-wave signals have been seen only once, in an event called GW170817. That event, discovered by the LIGO-Virgo network in August of 2017, involved a fiery collision between two neutron stars that was subsequently witnessed by dozens of telescopes on Earth and in space. Neutron star collisions are messy affairs with matter flung outward in all directions and are thus expected to shine with light. Conversely, black hole mergers, in most circumstances, are thought not to produce light.
According to the LIGO and Virgo scientists, the August 2019 event was not seen by light-based telescopes for a few possible reasons. First, this event was six times farther away than the merger observed in 2017, making it harder to pick up any light signals. Secondly, if the collision involved two black holes, it likely would have not shone with any light. Thirdly, if the object was in fact a neutron star, its 9-fold more massive black-hole partner might have swallowed it whole; a neutron star consumed whole by a black hole would not give off any light.
Debris Disk Results from the Gemini Planet Imager Exoplanet Survey’s Polarimetric Imaging Campaign
by Thomas M. Esposito, Paul Kalas, Michael P. Fitzgerald, Maxwell A. Millar-Blanchaer, Gaspard Duchêne, Jennifer Patience et al. in The Astronomical Journal
The Gemini Planet Imager on the Gemini South telescope looked at 104 young, nearby stars, 10–100 million years old, in search of debris disks. It found 26, 25 of which had inner holes indicating a planet. These debris rings, similar to the Kuiper Belt in our solar system, display amazing diversity in size and distance from the star. Such studies help astronomers understand the formation of planets and shed light on our system’s early history.
The images were obtained over a period of four years by a precision instrument, the Gemini Planet Imager (GPI), mounted on the 8-meter Gemini South telescope in Chile. The GPI uses a state-of-the-art adaptive optics system to remove atmospheric blur, providing the sharpest images to date of many of these disks.
Ground-based instruments like GPI, which is being upgraded to conduct similar observations in the northern sky from the Gemini North Telescope in Hawaii, can be a way to screen stars with suspected debris disks to determine which are worth targeting by more powerful, but expensive, telescopes to find planets — in particular, habitable planets. Several 20-, 30- and 40-meter telescopes, such as the Giant Magellan Telescope and the Extremely Large Telescope, will come online in the next couple of decades, while the orbiting James Webb Space Telescope is expected to be launched in 2021.
“It is often easier to detect the dust-filled disk than the planets, so you detect the dust first and then you know to point your James Webb Space Telescope or your Nancy Grace Roman Space Telescope at those systems, cutting down the number of stars you have to sift through to find these planets in the first place,” said Tom Esposito, a postdoctoral fellow at the University of California, Berkeley.
The debris disks in the images are the equivalent of the Kuiper Belt in our solar system, a frigid realm about 40 times farther from the sun than Earth — beyond the orbit of Neptune — and full of rocks, dust and ice that never became part of any planet in our solar system. Comets from the belt — balls of ice and rock — periodically sweep through the inner solar system, occasionally wreaking havoc on Earth, but also delivering life-related materials like water, carbon and oxygen.
Of the 26 images of debris disks obtained by the Gemini Planet Imager (GPI), 25 had “holes” around the central star that likely were created by planets sweeping up rocks and dust. Seven of the 26 were previously unknown; earlier images of the other 19 were not as sharp as those from GPI and often didn’t have the resolution to detect an inner hole. The survey doubles the number of debris disks imaged at such high resolution.
“One of the things we found is that these so-called disks are really rings with inner clearings,” said Esposito, who is also a researcher at the SETI Institute in Mountain View, California. “GPI had a clear view of the inner regions close to the star, whereas in the past, observations by the Hubble Space Telescope and older instruments from the ground couldn’t see close enough to the star to see the hole around it.”
The GPI incorporates a coronagraph that blocks the light from the star, allowing it to see as close as one astronomical unit (AU) from the star, or the distance of the Earth from our sun: 93 million miles.
The GPI targeted 104 stars that were unusually bright in infrared light, indicating they were surrounded by debris reflecting the light of the star or warmed by the star. The instrument recorded polarized near-infrared light scattered by small dust particles, about a thousandth of a millimeter (1 micron) in size, likely the result of collisions among larger rocks in a debris disk.
“There has been no systematic survey of young debris disks nearly this large, looking with the same instrument, using the same observing modes and methods,” Esposito said. “We detected these 26 debris disks with very consistent data quality, where we can really compare the observations, something that is unique in terms of debris disk surveys.”
The seven debris disks never before imaged in this manner were among 13 disks around stars moving together though the Milky Way, members of a group called the Scorpius-Centaurus stellar association, which is located between 100 and 140 parsecs from Earth, or some 400 light years.
“It is like the perfect fishing spot; our success rate was much greater than anything else we have ever done,” said Paul Kalas, a UC Berkeley adjunct professor of astronomy who is second author of the paper. Because all seven are around stars that were born in the same region at roughly the same time, “that group itself is a mini-laboratory where we can compare and contrast the architectures of many planetary nurseries developing simultaneously under a range of conditions, something that we really didn’t have before,” Esposito added.
Of the 104 stars observed, 75 had no disk of a size or density that GPI could detect, though they may well be surrounded by debris left over from planet formation. Three other stars were observed to host disks belonging to the earlier “protoplanetary” phase of evolution.
The extent of the debris disks varied widely, but most ranged between 20 and 100 AU. These were around stars that ranged in age from tens of millions of years to a few hundred million years, a very dynamic period for the evolution of planets. Most were larger and brighter than the sun.
The one star, HD 156623, that did not have a hole in the center of the debris disk was one of the youngest in the group, which fits with theories of how planets form. Initially, the protoplanetary disk should be relatively uniform, but as the system ages, planets form and sweep out the inner part of the disk.
“When we look at younger circumstellar disks, like protoplanetary disks that are in an earlier phase of evolution, when planets are forming, or before planets have started to form, there is a lot of gas and dust in the areas where we find these holes in the older debris disks,” Esposito said. “Something has removed that material over time, and one of the ways you can do that is with planets.”
Because polarized light from debris disks can theoretically tell astronomers the composition of the dust, Esposito is hoping to refine models to predict the composition — in particular, to detect water, which is thought to be a condition for life.
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