TL;DR
- NASA’s Parker Solar Probe reached the sun’s extended solar atmosphere, known as the corona, and spent five hours there. The spacecraft is the first to enter the outer boundaries of our sun.
- Astronomers have found no trace of dark matter in the galaxy AGC 114905, despite taking detailed measurements over a course of forty hours with state-of-the-art telescopes.
- Astrophysicists have made a breakthrough discovery in our understanding of the cosmic forces that shape the heliosphere.
- A powerful cosmic burst dubbed AT2018cow, or ‘the Cow,’ was much faster and brighter than any stellar explosion astronomers had seen. They have now determined it was likely a product of a dying star that, in collapsing, gave birth to a compact object in the form of a black hole or neutron star.
- A team of astronomers has discovered the fastest optical flash of a Type Ia supernova.
- Scientists have discovered a new object orbiting a Sun-like star that had been missed by previous searches. The object is very distant from its host star — more than 1,600 times farther than the Earth is from the Sun — and is thought to be a large planet or a small brown dwarf, a type of object that is not massive enough to burn hydrogen like true stars.
- Astronomers spying on a stellar system located dozens of lightyears from Earth have, for the first time, observed a troubling fireworks show: A star, named EK Draconis, ejected a massive burst of energy and charged particles much more powerful than anything scientists have seen in our own solar system.
- A cosmic object originally classified as a gas and dust cloud actually consists of three stars and could resolve a controversy among astronomers.
- Milky Way’s central black hole has a leak. This supermassive black hole looks like it still has the vestiges of a blowtorch-like jet dating back several thousand years. NASA’s Hubble Space Telescope hasn’t photographed the phantom jet but has helped find circumstantial evidence that it is still pushing feebly into a huge hydrogen cloud and then splattering, like the narrow stream from a hose aimed into a pile of sand.
- Upcoming industry events. And more!
Space industry in numbers
The global smart space market size is projected to grow from USD 9.4 billion in 2020 to USD 15.3 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 10.2% during the forecast period. The increasing venture capital funding and growing investments in smart space technology to drive market growth.
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
- Roscosmos selects first cosmonaut for commercial crew flights
- Mexico joins Artemis Accords
- Space Force official: U.S. has a broad range of options to respond to space aggression
- China sends classified Shijian satellites into orbit with milestone Long March launch
- Albedo wins license to sell 10-centimeter imagery
- Space traffic control startup Kayhan Space raises $3.7 million in seed funding
- Rocket Lab to acquire SolAero Holdings
- Satellite operators criticize “extreme” megaconstellation filings
- BlackSky to begin transition to higher-resolution imaging satellites in 2023
- New launch vehicles face schedule pressure
- South Korea, Australia sign MOU on space cooperation
- Parsons to develop ground operations center for DARPA’s Blackjack satellites
- Blue Origin launches first six-person New Shepard suborbital flight
- FAA to end commercial astronaut wings program
- Virgin Orbit adds Spire satellite to next launch
- South Australia’s Oculus Observatory hosts passive radar to track space objects
- DoD has to explain to Congress how it will buy low-latency satellite broadband
- Third consortium gets UK funds to study potential deorbit mission
- Planet shares begin trading on New York Stock Exchange
- Space Development Agency to acquire 28 missile-tracking satellites to launch in late 2024
- Europe awards study contract for disruptive satellite constellation ideas
- ST Engineering leads $30 million fundraising for satellite IoT startup
- GHGSat to launch three spacecraft on Falcon 9
- Soyuz launches Japanese private astronauts to ISS
- Tomorrow.io to grow weather constellation through SPAC deal
- Valley Tech Systems wins $94 million missile defense contract
- China’s SAR satellite surge continues with new constellation plan
- Andesat taps Astranis for Peru’s first dedicated telecoms satellite
- India, Russia agree to enhance space cooperation
- NASA announces new astronauts as safety panel recommends strategic planning for space exploration
- Chinese private firm Galactic Energy puts five satellites in orbit with second launch
- ULA launches STP-3 mission with national security and NASA payloads
- Rocket engine supplier Ursa Major raises $85 million in new funding round
Latest research
Parker Solar Probe Enters the Magnetically Dominated Solar Corona
by J. C. Kasper, K. G. Klein, E. Lichko, Jia Huang, C. H. K. Chen, S. T. Badman, J. Bonnell, P. L. Whittlesey, R. Livi, D. Larson, M. Pulupa, A. Rahmati, D. Stansby, K. E. Korreck, M. Stevens, A. W. Case, S. D. Bale, M. Maksimovic, M. Moncuquet, K. Goetz, J. S. Halekas, D. Malaspina, Nour E. Raouafi, A. Szabo, R. MacDowall, Marco Velli, Thierry Dudok de Wit, G. P. Zank in Physical Review Letters
NASA’s Parker Solar Probe reached the sun’s extended solar atmosphere, known as the corona, and spent five hours there. The spacecraft is the first to enter the outer boundaries of our sun.
“This marks the achievement of the primary objective of the Parker mission and a new era for understanding the physics of the corona,” said Justin C. Kasper, the first author, Deputy Chief Technology Officer at BWX Technologies, and a professor at the University of Michigan. The mission is led by the Johns Hopkins University Applied Physics Laboratory (JHU/APL).
The probe made the first direct observations of what lies within the sun’s atmosphere, measuring phenomena previously only estimated.
The sun’s outer edge begins at the Alfvén critical surface: the point below which the sun and its gravitational and magnetic forces directly control the solar wind. Many scientists think that sudden reverses in the sun’s magnetic field, called switchbacks, emerge from this area.
“The concept of sending spacecraft into the magnetized atmosphere of the sun — sufficiently close that the magnetic energy is greater than both ion and electron kinetic and thermal energy — predated NASA itself,” said Kasper.
In 2018, NASA launched Parker Solar Probe with the goal of finally reaching the sun’s corona and making humanity’s first visit to a star. This past April, the probe spent five hours below the Alfvén critical surface in direct contact with the sun’s plasma. Below that surface, the pressure and energy of the sun’s magnetic field was stronger than the pressure and energy of the particles. The spacecraft passed above and below the surface three separate times during its encounter. This is the first time a spacecraft has entered the solar corona and touched the atmosphere of the sun.
Surprisingly, the researchers discovered that the Alfvén critical surface is wrinkled. The data suggest that the largest and most distant wrinkle of the surface was produced by a pseudostreamer — a large magnetic structure more than 40 degrees across, found back on the innermost visible face of the sun. It is not currently known why a pseudostreamer would push the Alfvén critical surface away from the sun.
Researchers noticed far fewer switchbacks below the Alfvén critical surface than above it. The finding could mean that switchbacks do not form within the corona. Alternatively, low rates of magnetic reconnection on the sun’s surface could have pumped less mass into the observed wind stream, resulting in fewer switchbacks.
The probe also recorded some evidence of a potential power boost just inside the corona, which may point to unknown physics affecting heating and dissipation.
“We have been observing the sun and its corona for decades, and we know there is interesting physics going on there to heat and accelerate the solar wind plasma. Still, we cannot tell precisely what that physics is,” said Nour E. Raouafi, the Parker Solar Probe Project Scientist at JHU/APL. “With Parker Solar Probe now flying into the magnetically-dominated corona, we will get the long-awaited insights into the inner workings of this mysterious region.”
The observations took place during Parker Solar Probe’s eighth encounter with the sun. All data is publicly available in the NASA PSP archive. Several previous studies predicted the probe would first pass within the sun’s boundaries in 2021.
The fastest known object built by humans, Parker Solar Probe has made many new discoveries since its launch, including on explosions that create space weather and the dangers of super-speedy dust.
The new findings suggest that direct observations by spacecraft have much to illuminate about the physics of coronal heating and solar wind formation. Having achieved its goal of touching the sun, Parker Solar Probe will now descend even deeper into the sun’s atmosphere and linger for longer periods of time.
According to Gary Zank, a coinvestigator on the probe’s Solar Wind Electrons Alphas and Protons (SWEAP) instrument and a member of the National Academy of Sciences, “It is hard to overstate the significance of both the event and the observations made by Parker Solar Probe. For over 50 years, since the dawn of the space age, the heliospheric community has grappled with the unanswered problem of how the solar corona is heated to well over a million degrees to drive the solar wind. The first measurements of the sub-Alfvénic solar wind may represent the most major step forward in understanding the physics behind the acceleration of the solar wind since the formative model by Parker.”
“This event is what many heliophysicists have dreamed about for most of their careers!” Zank added.
No need for dark matter: resolved kinematics of the ultra-diffuse galaxy AGC 114905
by Pavel E. Mancera Piña, Filippo Fraternali, Tom Oosterloo, Elizabeth A. K. Adams, Kyle A. Oman, Lukas Leisman in Monthly Notices of the Royal Astronomical Society
An international team of astronomers led by researchers from the Netherlands has found no trace of dark matter in the galaxy AGC 114905, despite taking detailed measurements over a course of forty hours with state-of-the-art telescopes.
When Pavel Mancera Piña (University of Groningen and ASTRON, the Netherlands) and his colleagues discovered six galaxies with little to no dark matter, they were told “measure again, you’ll see that there will be dark matter around your galaxy.” However, after fourty hours of detailed observations using the Very Large Array (VLA) in New Mexico (United States), the evidence for a dark matter-free galaxy only became stronger.
The galaxy in question, AGC 114905, is about 250 million light-years away. It is classified as an ultra-diffuse dwarf galaxy, with the name ‘dwarf galaxy’ referring to its luminosity and not to its size. The galaxy is about the size of our own Milky Way but contains a thousand times fewer stars. The prevailing idea is that all galaxies, and certainly ultra-diffuse dwarf galaxies, can only exist if they are held together by dark matter.
The researchers collected data on the rotation of gas in AGC 114905 for 40 hours between July and October 2020 using the VLA telescope. Subsequently, they made a graph showing the distance of the gas from the centre of the galaxy on the x-axis and the rotation speed of the gas on the y-axis. This is a standard way to reveal the presence of dark matter. The graph shows that the motions of the gas in AGC 114905 can be completely explained by just normal matter.
“This is, of course, what we thought and hoped for because it confirms our previous measurements,” says Pavel Mancera Piña. “But now the problem remains that the theory predicts that there must be dark matter in AGC 114905, but our observations say there isn’t. In fact, the difference between theory and observation is only getting bigger.”
In their scientific publication, the researchers list the possible explanations for the lack of dark matter one by one. For example, AGC 114905 could have been stripped of dark matter by large nearby galaxies. Mancera Piña: “But there are none. And in the most reputed galaxy formation framework, the so called cold dark matter model, we would have to introduce extreme parameter values that are far beyond the usual range. Also with modified Newtonian dynamics, an alternative theory to cold dark matter, we cannot reproduce the motions of the gas within the galaxy.”
According to the researchers, there is one more assumption that could change their conclusions. That is the estimated angle at which they think they are observing the galaxy. “But that angle has to deviate very much from our estimate before there is room for dark matter again,” says co-author Tom Oosterloo (ASTRON).
Meanwhile, the researchers are examining a second ultra-diffuse dwarf galaxy in detail. If again observe no trace of dark matter in that galaxy, it will make the case for dark matter poor galaxies even stronger.
The research of Mancera Piña and colleagues is not an isolated case. Earlier, for example, the Dutch American Pieter van Dokkum (Yale University, USA) discovered a galaxy with hardly any dark matter. The techniques and measurements of Mancera Piña and colleagues are more robust.
Evidence for a compact object in the aftermath of the extragalactic transient AT2018cow
by Pasham, D.R., Ho, W.C.G., Alston, W. et al. in Nature Astronomy
In June of 2018, telescopes around the world picked up a brilliant blue flash from the spiral arm of a galaxy 200 million light years away. The powerful burst appeared at first to be a supernova, though it was much faster and far brighter than any stellar explosion scientists had yet seen. The signal, procedurally labeled AT2018cow, has since been dubbed simply “the Cow,” and astronomers have catalogued it as a fast blue optical transient, or FBOT — a bright, short-lived event of unknown origin.
Now an MIT-led team has found strong evidence for the signal’s source. In addition to a bright optical flash, the scientists detected a strobe-like pulse of high-energy X-rays. They traced hundreds of millions of such X-ray pulses back to the Cow, and found the pulses occurred like clockwork, every 4.4 milliseconds, over a span of 60 days.
Based on the frequency of the pulses , the team calculated that the X-rays must have come from an object measuring no more than 1,000 kilometers wide, with a mass smaller than 800 suns. By astrophysical standards, such an object would be considered compact, much like a small black hole or a neutron star.
Their findings strongly suggest that AT2018cow was likely a product of a dying star that, in collapsing, gave birth to a compact object in the form of a black hole or neutron star. The newborn object continued to devour surrounding material, eating the star from the inside — a process that released an enormous burst of energy.
“We have likely discovered the birth of a compact object in a supernova,” says lead author Dheeraj “DJ” Pasham, a research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. “This happens in normal supernovae, but we haven’t seen it before because it’s such a messy process. We think this new evidence opens possibilities for finding baby black holes or baby neutron stars.”
AT2018cow is one of many “astronomical transients” discovered in 2018. The “cow” in its name is a random coincidence of the astronomical naming process (for instance, “aaa” refers to the very first astronomical transient discovered in 2018). The signal is among a few dozen known FBOTs, and it is one of only a few such signals that have been observed in real-time. Its powerful flash — up to 100 times brighter than a typical supernova — was detected by a survey in Hawaii, which immediately sent out alerts to observatories around the world.
“It was exciting because loads of data started piling up,” Pasham says. “The amount of energy was orders of magnitude more than the typical core collapse supernova. And the question was, what could produce this additional source of energy?”
Astronomers have proposed various scenarios to explain the super-bright signal. For instance, it could have been a product of a black hole born in a supernova. Or it could have resulted from a middle-weight black hole stripping away material from a passing star. However, the data collected by optical telescopes haven’t resolved the source of the signal in any definitive way. Pasham wondered whether an answer could be found in X-ray data.
“This signal was close and also bright in X-rays, which is what got my attention,” Pasham says. “To me, the first thing that comes to mind is, some really energetic phenomenon is going on to generate X-rays. So, I wanted to test out the idea that there is a black hole or compact object at the core of the Cow.”
The team looked to X-ray data collected by NASA’s Neutron Star Interior Composition Explorer (NICER), an X-ray-monitoring telescope aboard the International Space Station. NICER started observing the Cow about five days after its initial detection by optical telescopes, monitoring the signal over the next 60 days. This data was recorded in a publicly available archive, which Pasham and his colleagues downloaded and analyzed.
The team looked through the data to identify X-ray signals emanating near AT2018cow, and confirmed that the emissions were not from other sources such as instrument noise or cosmic background phenomena. They focused on the X-rays and found that the Cow appeared to be giving off bursts at a frequency of 225 hertz, or once every 4.4 milliseconds.
Pasham seized on this pulse, recognizing that its frequency could be used to directly calculate the size of whatever was pulsing. In this case, the size of the pulsing object cannot be larger than the distance that the speed of light can cover in 4.4 milliseconds. By this reasoning, he calculated that the size of the object must be no larger than 1.3x108 centimeters, or roughly 1,000 kilometers wide.
“The only thing that can be that small is a compact object — either a neutron star or black hole,” Pasham says.
The team further calculated that, based on the energy emitted by AT2018cow, it must amount to no more than 800 solar masses.
“This rules out the idea that the signal is from an intermediate black hole,” Pasham says.
Apart from pinning down the source for this particular signal, Pasham says the study demonstrates that X-ray analyses of FBOTs and other ultrabright phenomena could be a new tool for studying infant black holes.
“Whenever there’s a new phenomenon, there’s excitement that it could tell something new about the universe,” Pasham says. “For FBOTs, we have shown we can study their pulsations in detail, in a way that’s not possible in the optical. So, this is a new way to understand these newborn compact objects.”
A Wide Planetary Mass Companion Discovered through the Citizen Science Project Backyard Worlds: Planet 9.
by Jacqueline K. Faherty, Jonathan Gagné, Mark Popinchalk, et al in The Astrophysical Journal
Citizen scientists have discovered a new object orbiting a Sun-like star that had been missed by previous searches. The object is very distant from its host star — more than 1,600 times farther than the Earth is from the Sun — and is thought to be a large planet or a small brown dwarf, a type of object that is not massive enough to burn hydrogen like true stars.
“This star had been looked at by more than one campaign searching for exoplanet companions. But previous teams looked really tight, really close to the star,” said lead author Jackie Faherty, senior scientist in the American Museum of Natural History’s Department of Astrophysics and co-founder of the citizen science project Backyard Worlds: Planet 9, which led to the object’s discovery. “Because citizen scientists really liked the project, they found an object that many of these direct imaging surveys would have loved to have found, but they didn’t look far enough away from its host.”
The Backyard Worlds project lets volunteers search through nearly five years of digital images taken from NASA’s Wide-field Infrared Survey Explorer (WISE) mission to try to identify new worlds inside and outside of our solar system. If an object close to Earth is moving, it will appear to “jump” in the same part of the sky over the years, similar to an object “moving” in a flipbook. Users can then flag these objects for further study by scientists.
In 2018, Backyard Worlds participant Jörg Schümann, who lives in Germany, alerted scientists to a new co-moving system: an object that appeared to be moving with a star. After confirming the system’s motion, scientists used telescopes in California and Hawai’i to observe the star and object separately and were immediately excited by what they saw.
The new object is young and has a low mass, between 10 and 20 times the mass of Jupiter. This range overlaps with an important cutoff point — 13 times the mass of Jupiter — which is sometimes used to distinguish planets from brown dwarfs. But scientists still aren’t sure how heavy planets can be, which can make relying on this cutoff challenging. “We don’t have a very good definition of the word ‘planet,” said Faherty.
Another defining feature is how they form: planets form from material gathering in disks around stars, while brown dwarfs are born from the collapse of giant clouds of gas, similar to how stars form. But the physical properties of this new object do not provide any clues to its formation. “There are hints that maybe it’s more like an exoplanet, but there’s nothing conclusive yet. However, it is an outlier,” said Faherty.
What surprised the team the most is the new object’s relationship to its host star. The object is farther away from the star than expected based on its comparatively low mass — over 1,600 times farther than the Earth is from the Sun. Few objects with such different masses from their host star have been found this far apart.
Ultimately, this discovery may help scientists get a better sense of how solar systems form, which is crucial to understanding the origins of life in the universe.
“You had an exoplanet community just staring so close to it,” said Faherty. “And we just pulled out a little, and we found an object. That makes me excited about what we might be missing in giant planets that might exist around these stars,” said Faherty. “Sometimes, you need to broaden your scope.”
Probable detection of an eruptive filament from a superflare on a solar-type star
by Kosuke Namekata, Hiroyuki Maehara, Satoshi Honda, Yuta Notsu, Soshi Okamoto, et al in Nature Astronomy
Astronomers spying on a stellar system located dozens of lightyears from Earth have, for the first time, observed a troubling fireworks show: A star, named EK Draconis, ejected a massive burst of energy and charged particles much more powerful than anything scientists have seen in our own solar system.
The study explores a stellar phenomenon called a “coronal mass ejection,” sometimes known as a solar storm. Notsu explained that the sun shoots out these sorts of eruptions on a regular basis — they’re made up of clouds of extremely-hot particles, or plasma, that can hurtle through space at speeds of millions of miles per hour. And they’re potentially bad news: If a coronal mass ejection hit Earth dead on, it could fry satellites in orbit and shut down the power grids serving entire cities.
“Coronal mass ejections can have a serious impact on Earth and human society,” said Notsu, a research associate at the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder and the U.S. National Solar Observatory.
The new study, led by Kosuke Namekata of the National Astronomical Observatory of Japan and formerly a visiting scholar at CU Boulder, also suggests that they can get a lot worse. In that research, Namekata, Nostu and their colleagues used telescopes on the ground and in space to peer at EK Draconis, which looks like a young version of the sun. In April 2020, the team observed EK Draconis ejecting a cloud of scorching-hot plasma with a mass in the quadrillions of kilograms — more than 10 times bigger than the most powerful coronal mass ejection ever recorded from a sun-like star.
The event may serve as a warning of just how dangerous the weather in space can be.
“This kind of big mass ejection could, theoretically, also occur on our sun,” Notsu said. “This observation may help us to better understand how similar events may have affected Earth and even Mars over billions of years.”
Notsu explained that coronal mass ejections often come right after a star lets loose a flare, or a sudden and bright burst of radiation that can extend far out into space. Recent research, however, has suggested that on the sun, this sequence of events may be relatively sedate, at least so far as scientists have observed. In 2019, for example, Notsu and his colleagues published a study that showed that young sun-like stars around the galaxy seem to experience frequent superflares — like our own solar flares but tens or even hundreds of times more powerful.
Such a superflare could, theoretically, also happen on Earth’s sun but not very often, maybe once every several thousand years. Still, it got Notsu’s team curious: Could a superflare also lead to an equally super coronal mass ejection?
“Superflares are much bigger than the flares that we see from the sun,” Notsu said. “So we suspect that they would also produce much bigger mass ejections. But until recently, that was just conjecture.”
To find out, the researchers set their sights on EK Draconis. The curious star, Notsu explained, is about the same size as our sun, but, at just 100 million years old, it’s a relative youngster in a cosmic sense.
“It’s what our sun looked like 4.5 billion years ago,” Notsu said.
The researchers observed the star for 32 nights in winter and spring 2020 using NASA’s Transiting Exoplanet Survey Satellite (TESS) and Kyoto University’s SEIMEI Telescope. On April 5, Notsu and his colleagues got lucky: The researchers looked on as EK Draconis erupted into a superflare, a really big one. About 30 minutes later, the team observed what appeared to be a coronal mass ejection flying away from the star’s surface. The researchers were only able to catch the first step in that ejection’s life, called the “filament eruption” phase. But even so, it was a monster, moving at a top speed of roughly 1 million miles per hour.
It may also not bode well for life on Earth: The team’s findings hint that the sun could also be capable of such violent extremes. But don’t hold your breath — like superflares, super coronal mass ejections are probably rare around our getting-on-in-years sun.
Still, Notsu noted that huge mass ejections may have been much more common in the early years of the solar system. Gigantic coronal mass ejections, in other words, could have helped to shape planets like Earth and Mars into what they look like today.
“The atmosphere of present-day Mars is very thin compared to Earth’s,” Notsu said. “In the past, we think that Mars had a much thicker atmosphere. Coronal mass ejections may help us to understand what happened to the planet over billions of years.”
Tracing the Milky Way’s Vestigial Nuclear Jet
by Gerald Cecil, Alexander Y. Wagner, Joss Bland-Hawthorn, Geoffrey V. Bicknell, Dipanjan Mukherjee in The Astrophysical Journal
Our Milky Way’s central black hole has a leak. This supermassive black hole looks like it still has the vestiges of a blowtorch-like jet dating back several thousand years. NASA’s Hubble Space Telescope hasn’t photographed the phantom jet but has helped find circumstantial evidence that it is still pushing feebly into a huge hydrogen cloud and then splattering, like the narrow stream from a hose aimed into a pile of sand.
This is further evidence that the black hole, with a mass of 4.1 million Suns, is not a sleeping monster but periodically hiccups as stars and gas clouds fall into it. Black holes draw some material into a swirling, orbiting accretion disk where some of the infalling material is swept up into outflowing jets that are collimated by the black hole’s powerful magnetic fields. The narrow “searchlight beams” are accompanied by a flood of deadly ionizing radiation.
“The central black hole is dynamically variable and is currently powered down,” said Gerald Cecil of the University of North Carolina in Chapel Hill. Cecil pieced together, like a jigsaw puzzle, multiwavelength observations from a variety of telescopes that suggest the black hole burps out mini-jets every time it swallows something hefty, like a gas cloud.
In 2013 evidence for a stubby southern jet near the black hole came from X-rays detected by NASA’s Chandra X-ray Observatory and radio waves detected by the Jansky Very Large Array telescope in Socorro, New Mexico. This jet too appears to be plowing into gas near the black hole.
Cecil was curious if there was a northern counter-jet as well. He first looked at archival spectra of such molecules as methyl alcohol and carbon monosulfide from the ALMA Observatory in Chile (Atacama Large Millimeter/ Submillimeter Array), which uses millimeter wavelengths to peer through the veils of dust between us and the galactic core. ALMA reveals an expanding, narrow linear feature in molecular gas that can be traced back at least 15 light-years to the black hole.
By connecting the dots, Cecil next found in Hubble infrared-wavelength images a glowing, inflating bubble of hot gas that aligns to the jet at a distance of at least 35 light-years from the black hole. His team suggests that the black hole jet has plowed into it, inflating the bubble. These two residual effects of the fading jet are the only visual evidence of it impacting molecular gas.
As it blows through the gas the jet hits material and bends along multiple streams. “The streams percolate out of the Milky Way’s dense gas disk,” said co-author Alex Wagner of Tsukuba University in Japan. “The jet diverges from a pencil beam into tendrils, like that of an octopus.” This outflow creates a series of expanding bubbles that extend out to at least 500 light-years. This larger “soap bubble” structure has been mapped at various wavelengths by other telescopes.
Wagner and Cecil next ran supercomputer models of jet outflows in a simulated Milky Way disk, which reproduced the observations.
“Like in archeology, you dig and dig to find older and older artifacts until you come upon remnants of a grand civilization,” said Cecil. Wagner’s conclusion: “Our central black hole clearly surged in luminosity at least 1 millionfold in the last million years. That sufficed for a jet to punch into the Galactic halo.”
Previous observations by Hubble and other telescopes found evidence that the Milky Way’s black hole had an outburst about 2–4 million years ago. That was energetic enough to create an immense pair of bubbles towering above our galaxy that glow in gamma-rays. They were first discovered by NASA’s Fermi Gamma-ray Space Telescope in 2010 and are surrounded by X-ray bubbles that were discovered in 2003 by the ROSAT satellite and mapped fully in 2020 by the eROSITA satellite.
Hubble ultraviolet-light spectra have been used to measure the expansion velocity and composition of the ballooning lobes. Hubble spectra later found that the burst was so powerful that it lit up a gaseous structure, called the Magellanic stream, at about 200,000 light-years from the galactic center.
To get a better idea of what’s going on, Cecil looked at Hubble and radio images of another galaxy with a black hole outflow. Located 47 million light-years away, the active spiral galaxy NGC 1068 has a string of bubble features aligned along an outflow from the very active black hole at its center. Cecil found that the scales of the radio and X-ray structures emerging from both NGC 1068 and our Milky Way are very similar.
“A bow shock bubble at the top of the NGC 1068 outflow coincides with the scale of the Fermi bubble start in the Milky Way. NGC 1068 may be showing us what the Milky Way was doing during its major power surge several million years ago.”
The residual jet feature is close enough to the Milky Way’s black hole that it would become much more prominent only a few decades after the black hole powers up again. Cecil notes that “the black hole need only increase its luminosity by a hundredfold over that time to refill the jet channel with emitting particles. It would be cool to see how far the jet gets in that outburst. To reach into the Fermi gamma-ray bubbles would require that the jet sustain for hundreds of thousands of years because those bubbles are each 50,000 light years across!”
The Apparent Tail of the Galactic Center Object G2/DSO
by Florian Peißker, Michal Zajaček, Andreas Eckart, Basel Ali, Vladimír Karas, Nadeen B. Sabha, Rebekka Grellmann, Lucas Labadie, Banafsheh Shahzamanian in The Astrophysical Journal
What was previously identified as a gas and dust cloud at the centre of our galaxy actually consists of three very young stars. That is the result of a new study led by scientists from the University of Cologne’s Institute of Astrophysics. The European Southern Observatory’s Very Large Telescope (VLT) — a telescope with mirror diameters of 8.20 metres on the summit of Cerro Paranal in Chile — provided the data for the study. The stars began to form less than 1 million years ago, which is very young in astrophysical terms. By comparison, our sun is just under 5 billion years old.
In 2011, an object was found by means of the infrared data measured by the Very Large Telescope, promising to reveal an unprecedented process at the centre of our galaxy. Based on a multi-wavelength analysis, scientists determined that it must be a cloud of gas and dust, which was named G2. The interaction with the black hole at the centre of our galaxy, SgrA*, should have torn G2 apart and caused proverbial fireworks. The researchers assumed that when G2 collided with SgrA*, various processes would cause the gas and dust to make the black hole flare up. But that did not happen.
In addition, there were other factors that gave astronomers around the world a headache and fuelled controversial discussions. Studies showed that the temperature of G2 is almost twice as high as that of surrounding dust sources. One possible explanation for G2’s temperature is the extreme number of stars at the centre of our galaxy. So these stars could have heated up G2. The only question is why all other known dust sources at the centre of the galaxy show a much lower temperature. The black hole, SgrA*, was also ruled out as a heat source. The temperature of G2 should have increased the closer the supposed dust cloud came to the black hole — like we would feel if we approached a radiator. However, the temperature remained constant over a long period of time, although the distance to the black hole varied. The more closely G2 was observed around the world, the more it became apparent that the cosmic object had to be more than just a cloud of gas and dust. The new results show that G2 actually consists of three individual stars.
Together with the data from the Southern Observatory archive, we were able to cover a period from 2005 to 2019,’ said lead author Dr Florian Peißker from the Institute of Astrophysics. The unusual structure of the data was also helpful in locating G2. Each pixel of the captured image has an associated spectrum that covers a very specific and detailed waveband. For the scientists, this offers an enormous level of detail. ‘That G2 actually consists of three evolving young stars is sensational. Never before have stars younger than the ones found been observed around SgrA*,’ Peißker said.
The results open the door to many more fascinating research questions — for example where these young stars come from. The radiation-intensive environment of a supermassive black hole is not necessarily the best place to produce young stars. Peißker concludes, ‘The new results provide unique insights into how black holes work. We can use the environment of SgrA* as a blueprint to learn more about the evolution and processes of other galaxies in completely different corners of our Universe.’
A Turbulent Heliosheath Driven by the Rayleigh–Taylor Instability
by M. Opher, J. F. Drake, G. Zank, E. Powell, W. Shelley, M. Kornbleuth, V. Florinski, V. Izmodenov, J. Giacalone, S. Fuselier, K. Dialynas, A. Loeb, J. Richardson in The Astrophysical Journal
A multi-institutional team of astrophysicists headquartered at Boston University, led by BU astrophysicist Merav Opher, has made a breakthrough discovery in our understanding of the cosmic forces that shape the protective bubble surrounding our solar system — a bubble that shelters life on Earth and is known by space researchers as the heliosphere.
Astrophysicists believe the heliosphere protects the planets within our solar system from powerful radiation emanating from supernovas, the final explosions of dying stars throughout the universe. They believe the heliosphere extends far beyond our solar system, but despite the massive buffer against cosmic radiation that the heliosphere provides Earth’s life-forms, no one really knows the shape of the heliosphere — or, for that matter, the size of it.
“How is this relevant for society? The bubble that surrounds us, produced by the sun, offers protection from galactic cosmic rays, and the shape of it can affect how those rays get into the heliosphere,” says James Drake, an astrophysicist at University of Maryland who collaborates with Opher. “There’s lots of theories but, of course, the way that galactic cosmic rays can get in can be impacted by the structure of the heliosphere — does it have wrinkles and folds and that sort of thing?”
Opher’s team has constructed some of the most compelling computer simulations of the heliosphere, based on models built on observable data and theoretical astrophysics. At BU, in the Center for Space Physics, Opher, a College of Arts & Sciences professor of astronomy, leads a NASA DRIVE (Diversity, Realize, Integrate, Venture, Educate) Science Center. That team, made up of experts Opher recruited from 11 other universities and research institutes, develops predictive models of the heliosphere in an effort the team calls SHIELD (Solar-wind with Hydrogen Ion Exchange and Large-scale Dynamics). Since BU’S NASA DRIVE Science Center first received funding in 2019, Opher’s SHIELD team has hunted for answers to several puzzling questions: What is the overall structure of the heliosphere? How do its ionized particles evolve and affect heliospheric processes? How does the heliosphere interact and influence the interstellar medium, the matter and radiation that exists between stars? And how do cosmic rays get filtered by, or transported through, the heliosphere?
“SHIELD combines theory, modeling, and observations to build comprehensive models,” Opher says. “All these different components work together to help understand the puzzles of the heliosphere.”
A paper reveals that neutral hydrogen particles streaming from outside our solar system most likely play a crucial role in the way our heliosphere takes shape. In their latest study, Opher’s team wanted to understand why heliospheric jets — blooming columns of energy and matter that are similar to other types of cosmic jets found throughout the universe — become unstable.
“Why do stars and black holes — and our own sun — eject unstable jets?” Opher says. “We see these jets projecting as irregular columns, and [astrophysicists] have been wondering for years why these shapes present instabilities.”
Similarly, SHIELD models predict that the heliosphere, traveling in tandem with our sun and encompassing our solar system, doesn’t appear to be stable. Other models of the heliosphere developed by other astrophysicists tend to depict the heliosphere as having a comet-like shape, with a jet — or a “tail” — streaming behind in its wake. In contrast, Opher’s model suggests the heliosphere is shaped more like a croissant or even a donut.
The reason for that? Neutral hydrogen particles, so-called because they have equal amounts of positive and negative charge that net no charge at all.
“They come streaming through the solar system,” Opher says. Using a computational model like a recipe to test the effect of ‘neutrals’ on the shape of the heliosphere, she “took one ingredient out of the cake — the neutrals — and noticed that the jets coming from the sun, shaping the heliosphere, become super stable. When I put them back in, things start bending, the center axis starts wiggling, and that means that something inside the heliospheric jets is becoming very unstable.”
Instability like that would theoretically cause disturbance in the solar winds and jets emanating from our sun, causing the heliosphere to split its shape — into a croissant-like form. Although astrophysicists haven’t yet developed ways to observe the actual shape of the heliosphere, Opher’s model suggests the presence of neutrals slamming into our solar system would make it impossible for the heliosphere to flow uniformly like a shooting comet. And one thing is for sure — neutrals are definitely pelting their way through space.
Drake, a coauthor on the new study, says Opher’s model “offers the first clear explanation for why the shape of the heliosphere breaks up in the northern and southern areas, which could impact our understanding of how galactic cosmic rays come into Earth and the near-Earth environment.” That could affect the threat that radiation poses to life on Earth and also for astronauts in space or future pioneers attempting to travel to Mars or other planets.
“The universe is not quiet,” Opher says. “Our BU model doesn’t try to cut out the chaos, which has allowed me to pinpoint the cause [of the heliosphere’s instability]…. The neutral hydrogen particles.”
Specifically, the presence of the neutrals colliding with the heliosphere triggers a phenomenon well known by physicists, called the Rayleigh-Taylor instability, which occurs when two materials of different densities collide, with the lighter material pushing against the heavier material. It’s what happens when oil is suspended above water, and when heavier fluids or materials are suspended above lighter fluids. Gravity plays a role and gives rise to some wildly irregular shapes. In the case of the cosmic jets, the drag between the neutral hydrogen particles and charged ions creates a similar effect as gravity. The “fingers” seen in the famous Horsehead Nebula, for example, are caused by the Rayleigh-Taylor instability.
“This finding is a really major breakthrough, it’s really set us in a direction of discovering why our model gets its distinct croissant-shaped heliosphere and why other models don’t,” Opher says.
Discovery of the Fastest Early Optical Emission from Overluminous SN Ia 2020hvf: A Thermonuclear Explosion within a Dense Circumstellar Environment
by Ji-an Jiang, Keiichi Maeda, Miho Kawabata, Mamoru Doi, et al in The Astrophysical Journal Letters
A team of astronomers has discovered the fastest optical flash of a Type Ia supernova.
Many stars end their lives through a spectacular explosion. Most massive stars will explode as a supernova. Though a white dwarf star is the remnant of an intermediate mass star like our Sun, it can explode if the star is part of a close binary star system, where two stars orbit around each other. This type of supernovae is classified as Type Ia supernovae.
Because of the uniform and extremely high brightness of the Type Ia supernova, which is about 5 billion times brighter than our Sun, they are widely used by researchers as a standard candle for distance measurements in astronomy. As the most successful example Type Ia supernovae helped researchers discover the accelerating expansion of our universe. But despite the great success of the Type Ia supernova cosmology, researchers are still puzzled by basic questions such as what the progenitor systems of Type Ia supernovae are, and how Type Ia supernova explosions are ignited.
To figure out these long-standing issues, a team of astronomers, led by Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Project Researcher Ji-an Jiang, attempted to catch Type Ia supernovae within one day of their explosions, called early-phase Type Ia supernovae, using new-generation wide-field survey facilities, including the Tomo-e Gozen camera, the first wide-field mosaic CMOS sensor imager in the world. By regularly checking early-phase supernova candidates discovered by the Tomo-e transient survey, one transient, Tomo-e202004aaelb, caught Jiang’s attention.
“Tomo-e202004aaelb was discovered with high brightness on April 21 in 2020. Surprisingly, its brightness showed significant variation in the next two days and then behaved like a normal early-phase Type Ia supernova. We have discovered several early-phase Type Ia supernovae that show interesting excess emission in the first few days of their explosions but have never seen such a fast and prominent early emission in optical wavelengths. Thanks to the high-cadence survey mode and the excellent performance of Tomo-e Gozen, we can perfectly catch this amazing feature for the first time. Such a prompt early flash should originate from a different origin compared to previously discovered early-excess Type Ia supernovae,” said Jiang.
Computational simulations by Kyoto University Associate Professor Keiichi Maeda showed that the origin of the mysterious fast optical flash can be explained by the energy released from an interaction between supernova ejecta and a dense and confined circumstellar material (CSM) soon after the supernova explosion.
“We have not seen such a short and bright flash from Type Ia supernovae before, even with a recently increasing number of very early discoveries soon after the supernova explosion in the last few years, including those discovered by our team. The nature of the CSM must reflect the nature of the progenitor star, and thus this is a key to understanding what kind of a star explodes and how they do so. A question is what makes this supernova so special,” said Maeda.
Through spectroscopic observations by the Seimei telescope of Kyoto University, the team found that the SN is a variant of brightest Type Ia supernovae.
“At the first look of the spectrum taken just after the initial flash, it stood out as something different from normal supernovae. We noticed that a brightest class of Type Ia supernovae might look like this one if they would be observed in such an early phase. Our classification was subsequently confirmed as the spectra evolve to look more and more similar to the previously found bright Type Ia supernovae,” said Kyoto University Project Researcher Miho Kawabata.
The team’s result shows at least a fraction of Type Ia supernovae originate from a dense CSM environment, which provides a stringent constraint on the progenitor system of these spectacular phenomena in our universe. Given that Tomo-e202004aaelb (SN 2020hvf) is much brighter than typical Type Ia supernovae used as the distance indicator, the discovery will enable Jiang and his collaborators to test various theories which have been proposed for these peculiar overluminous Type Ia supernovae.
“Previously, we have constructed theoretical models of super-Chandrasekhar-mass rotating white dwarfs and their explosions. Such massive models can be consistent with the peak brightness of SN 2020hvf, but more theoretical work is necessary to explain the detailed observational properties. SN 2020hvf has provided a wonderful opportunity of collaboration between the theory and observations.” said Kavli IPMU Senior Scientist Ken’ichi Nomoto.
Jiang’s team will continue looking for the answer of the long-standing origin issue of Type Ia supernovae by carrying out transient surveys with telescopes all over the world.
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