In Cumbria, UK – an area with excellent nighttime sky quality – ecologists charted the effects of varying levels of light pollution by tracking the singing behaviour of robins. Over a three-month period, samples of birdsong were taken in paired sites consisting of one light and one dark site.
The study’s findings indicated that artificial lighting, especially uncontrolled or unshielded lighting fixtures, caused earlier singing and calling in robins and other songbird species. Both song repertoire and UV light are used by animals for mate selection and if mating strategies are changed by light levels, females run the risk of choosing lesser fit males.
According to Jack Ellerby, project officer for Cumbria Dark Skies, fieldwork tracing the impact of light pollution and wildlife tends to fall under the radar, because the effects on animals are more incremental than that of other pollution, such as sewage, oil spills or plastic litter.
While light pollution can’t be blamed for the entirety of wildlife behavioural change, Stephanie Holt, a bat expert at the UK’s Natural History Museum, believes it may be a “tipping point”. She notes that some of the most important impacts of lighting on invertebrates are still largely unknown. “[A]s the cornerstone of all of our ecosystems, we should be targeting research and conservation in that direction,” she says.
However, lighting legislation, at least in the UK, is slow to get off the ground. As few ecologists are employed at the planning authority level, artificial lighting schemes are often swept to the back of the pile of government priorities, Holt says.
Elsewhere in the world, strides are being taken to protect wildlife at night. In the Netherlands, LED street light schemes in towns and cities are supporting rare bats species, while France has adopted one of the most progressive light pollution policies to date. Enshrined in the 2018 law are technical requirements for the design and operation of outdoor lighting installations used in both public and private property.
UK campaigners are hoping that 2020’s first meeting of the All Party Parliamentary Group for Dark Skies, which resulted in a 10-point policy plan for improving provisions for dark skies, could be the country’s gateway into artificial lighting control.
In the meantime, the baton is held by individuals, who can lobby local politicians and authorities, create nocturnal corridors for wildlife, and ensure that their own homes and offices do not contribute to additional sources of light pollution, says Holt.
A rogue black hole wandering the space lanes of our Milky Way galaxy alone could be the smallest black hole yet found, according to one estimate of its mass.
Earlier this year, astronomers led by Kailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland, announced the discovery of the first known isolated stellar-mass black hole.
The black hole is 5,000 light-years away and was discovered thanks to the power of its gravity to act as a gravitational lens, magnifying the light of a background star 19,000 light-years away. It was initially spotted by two ground-based surveys, the Polish-led Optical Gravitational Lensing Experiment (OGLE) which mostly uses the Las Campanas Observatory in Chile, and the Microlensing Observations in Astrophysics (MOA) project at the Mount John University Observatory in New Zealand.
Related: A ‘trove’ of black hole discoveries emerge from dwarf galaxies
Sahu’s team used the Hubble Space Telescope to follow up on the discovery, and the degree of gravitational lensing allowed them to conclude that the black hole has a mass about 7.1 times greater than the sun’s mass.
However, a second team has now come forward with a different mass calculation. The group, led by Casey Lam of the University of California, Berkeley, concluded that the object has a mass between 1.6 and 4.4 times the mass of the sun. If correct, then this could have intriguing implications.
Stellar-mass black holes are the product of the supernovae of stars with masses 20 times greater than the Sun. On the other hand, when stars with between 8 and 20 solar masses go supernovae, they leave behind a neutron star instead.
Neutron stars can theoretically have masses up to about 2.3 solar masses. Observations of stellar-mass black holes detectable in binary systems have not turned up any with less than 5 solar masses, creating a gap between the most massive neutron stars and the least massive black holes. If the black hole is at the upper end of Lam’s mass range, it would help plug this gap. (Several candidate gravitational-wave events have also been detected involving objects that fall into this mass gap.)
“Whatever it is, the object is the first dark stellar remnant discovered wandering through the galaxy unaccompanied by another star,” said Lam in a NASA statement (opens in new tab).
A composite image captured by the Hubble Space Telescope shows the change in brightness of a star caused by a foreground black hole drifting in front of it. The apparent brightening of the background star is caused by gravitational lensing. (Image credit: NASA, ESA, Kailash Sahu (STScI) IMAGE PROCESSING: Joseph DePasquale (STScI))
(opens in new tab)
Even though stars with more than 20 solar masses account for just 0.1% of all the stars in the Milky Way, there are so many stars in the Milky Way (an estimated 100–200 billion), and the Milky Way is so old (approximately 13 billion years) that there should now be 100 million or more stellar-mass black holes in our galaxy.
Many of these are found in binary systems, where their presence is evident from their gravitational pull on their companion star and their accretion of matter from their neighbor. One has even been found inside a star cluster, NGC 1850 in the Large Magellanic Cloud. However, many others will be wandering between the stars, going unnoticed until a chance alignment with a background star means we spot them creating a gravitational lens.
This discovery is just the tip of the iceberg. NASA’s Nancy Grace Roman Space Telescope, which is planned for launch in 2027, will survey large swathes of the Milky Way and is expected to identify several thousand microlensing events, many of which could be black holes.
Both papers from Sahu’s team (opens in new tab) and Lam’s team (opens in new tab) are published online.
Follow Keith Cooper on Twitter @21stCenturySETI. Follow uson Twitter @Spacedotcom (opens in new tab) and on Facebook (opens in new tab).
The Emmy Award-winning star hit the red carpet at Radio City Music Hall in a textured black gown by Thom Browne. Light’s Browne number featured a long-sleeved silhouette in a satin-like texture that caught the light, elevated with horizontal panels that created a modern take on the classic ribbed texture. Finishing Light’s piece were sharp structured shoulders and a floor-length skirt.
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Finishing Light’s ensemble, styled by Kevin Michael Ericson, was a gleaming silver link necklace studded with diamonds from Briony Raymond New York, as well as a sparkling Verdura cocktail ring.
Judith Light attends the Tony Awards 2022 at Radio City Music Hall in New York City on June 12, 2022. – Credit: Michael Buckner for WWD
Michael Buckner for WWD
When it came to shoes, Light’s footwear wasn’t fully visible beneath her gown’s long train. However, while raising her foot in a one-legged pose, the “Ugly Betty” star’s footwear was revealed to be black pointed-toe pumps. Creating a streamlined appearance, the sharp style was finished with thin stiletto heels totaling 2-3 inches in height.
Judith Light attends the Tony Awards 2022 at Radio City Music Hall in New York City on June 12, 2022. – Credit: Michael Buckner for WWD
Michael Buckner for WWD
The Tony Awards 2022, which celebrate the top theater performances on Broadway, are held at Radio City Music Hall in New York City and air on CBS. The ceremony, hosted by Ariana DeBose, was preceded by “The Tony Awards: Act One” on Paramount+, which introduced special performances.
The top nominations were led by “A Strange Loop (11), followed by “MJ” and “Paradise Square” with 10 nominations each, “Company” (9) and “The Lehman Trilogy” (8). The evening included performances from all six nominated shows for Best Musical (“Six,” “Paradise Square,” “MJ,” “Mr. Saturday Night,” “Girl From the North Country” and “A Strange Loop”), as well as “Company” and “The Music Man” revivals and Billy Porter, Bernadette Peters, The New York City Gay Men’s Chorus, and the original Broadway cast of 2007’s “Spring Awakening.”
In addition to the program’s traditional “In Memoriam” segment, the broadcast also included a tribute to the understudies and swings who worked throughout the 2021 Broadway season. Among the star-studded array of presenters were Andrew Garfield, Bowen Yang, Jessica Chastain, Jennifer Hudson, Cynthia Erivo, Vanessa Hudgens and Paris and Prince Jackson.
Discover more Tony Awards 2022 red carpet arrivals in the gallery.
Launch Gallery: All the Celebrity Arrivals at the Tony Awards 2022 Red Carpet
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image: Hubble Space Telescope image of a distant star that was brightened and distorted by an invisible but very compact and heavy object between it and Earth. The compact object — estimated by UC Berkeley astronomers to be between 1.6 and 4.4 times the mass of our sun — could be a free-floating black hole, one of perhaps 200 million in the Milky Way galaxy.
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Credit: Image courtesy of STScI/NASA/ESA
If, as astronomers believe, the death of large stars leave behind black holes, there should be hundreds of millions of them scattered throughout the Milky Way galaxy. The problem is, isolated black holes are invisible.
Now, a team led by University of California, Berkeley, astronomers has for the first time discovered what may be a free-floating black hole by observing the brightening of a more distant star as its light was distorted by the object’s strong gravitational field — so-called gravitational microlensing.
The team, led by graduate student Casey Lam and Jessica Lu, a UC Berkeley associate professor of astronomy, estimates that the mass of the invisible compact object is between 1.6 and 4.4 times that of the sun. Because astronomers think that the leftover remnant of a dead star must be heavier than 2.2 solar masses in order to collapse to a black hole, the UC Berkeley researchers caution that the object could be a neutron star instead of a black hole. Neutron stars are also dense, highly compact objects, but their gravity is balanced by internal neutron pressure, which prevents further collapse to a black hole.
Whether a black hole or a neutron star, the object is the first dark stellar remnant — a stellar “ghost” — discovered wandering through the galaxy unpaired with another star.
“This is the first free-floating black hole or neutron star discovered with gravitational microlensing,” Lu said. “With microlensing, we’re able to probe these lonely, compact objects and weigh them. I think we have opened a new window onto these dark objects, which can’t be seen any other way.”
Determining how many of these compact objects populate the Milky Way galaxy will help astronomers understand the evolution of stars — in particular, how they die — and of our galaxy, and perhaps reveal whether any of the unseen black holes are primordial black holes, which some cosmologists think were produced in large quantities during the Big Bang.
The analysis by Lam, Lu and their international team has been accepted for publication in The Astrophysical Journal Letters. The analysis includes four other microlensing events that the team concluded were not caused by a black hole, though two were likely caused by a white dwarf or a neutron star. The team also concluded that the likely population of black holes in the galaxy is 200 million — about what most theorists predicted.
Same data, different conclusions
Notably, a competing team from the Space Telescope Science Institute (STScI) in Baltimore analyzed the same microlensing event and claims that the mass of the compact object is closer to 7.1 solar masses and indisputably a black hole. A paper describing the analysis by the STScI team, led by Kailash Sahu, has been accepted for publication in The Astrophysical Journal.
Both teams used the same data: photometric measurements of the distant star’s brightening as its light was distorted or “lensed” by the super-compact object, and astrometric measurements of the shifting of the distant star’s location in the sky as a result of the gravitational distortion by the lensing object. The photometric data came from two microlensing surveys: the Optical Gravitational Lensing Experiment (OGLE), which employs a 1.3-meter telescope in Chile operated by Warsaw University, and the Microlensing Observations in Astrophysics (MOA) experiment, which is mounted on a 1.8-meter telescope in New Zealand operated by Osaka University. The astrometric data came from NASA’s Hubble Space Telescope. STScI manages the science program for the telescope and conducts its science operations.
Because both microlensing surveys caught the same object, it has two names: MOA-2011-BLG-191 and OGLE-2011-BLG-0462, or OB110462, for short.
While surveys like these discover about 2,000 stars brightened by microlensing each year in the Milky Way galaxy, the addition of astrometric data is what allowed the two teams to determine the mass of the compact object and its distance from Earth. The UC Berkeley-led team estimated that it lies between 2,280 and 6,260 light years (700-1920 parsecs) away, in the direction of the center of the Milky Way Galaxy and near the large bulge that surrounds the galaxy’s central massive black hole.
The STScI group estimated that it lies about 5,153 light years (1,580 parsecs) away.
Looking for a needle in a haystack
Lu and Lam first became interested in the object in 2020 after the STScI team tentatively concluded that five microlensing events observed by Hubble — all of which lasted for more than 100 days, and thus could have been black holes — might not be caused by compact objects after all.
Lu, who has been looking for free-floating black holes since 2008, thought the data would help her better estimate their abundance in the galaxy, which has been roughly estimated at between 10 million and 1 billion. To date, star-sized black holes have been found only as part of binary star systems. Black holes in binaries are seen either in X-rays, produced when material from the star falls onto the black hole, or by recent gravitational wave detectors, which are sensitive to mergers of two or more black holes. But these events are rare.
“Casey and I saw the data and we got really interested. We said, ‘Wow, no black holes. That’s amazing,’ even though there should have been,” Lu said. “And so, we started looking at the data. If there were really no black holes in the data, then this wouldn’t match our model for how many black holes there should be in the Milky Way. Something would have to change in our understanding of black holes — either their number or how fast they move or their masses.”
When Lam analyzed the photometry and astrometry for the five microlensing events, she was surprised that one, OB110462, had the characteristics of a compact object: The lensing object seemed dark, and thus not a star; the stellar brightening lasted a long time, nearly 300 days; and the distortion of the background star’s position also was long-lasting.
The length of the lensing event was the main tipoff, Lam said. In 2020, she showed that the best way to search for black hole microlenses was to look for very long events. Only 1% of detectable microlensing events are likely to be from black holes, she said, so looking at all events would be like searching for a needle in a haystack. But, Lam calculated, about 40% of microlensing events that last more than 120 days are likely to be black holes.
“How long the brightening event lasts is a hint of how massive the foreground lens bending the light of the background star is,” Lam said. “Long events are more likely due to black holes. It’s not a guarantee, though, because the duration of the brightening episode not only depends on how massive the foreground lens is, but also on how fast the foreground lens and background star are moving relative to each other. However, by also getting measurements of the apparent position of the background star, we can confirm whether the foreground lens really is a black hole.”
According to Lu, the gravitational influence of OB110462 on the light of the background star was amazingly long. It took about one year for the star to brighten to its peak in 2011, then about a year to dim back to normal.
More data will distinguish black hole from neutron star
To confirm that OB110462 was caused by a super-compact object, Lu and Lam asked for more astrometric data from Hubble, some of which arrived last October. That new data showed that the change in position of the star as a result of the gravitational field of the lens is still observable 10 years after the event. Further Hubble observations of the microlens are tentatively scheduled for fall 2022.
Analysis of the new data confirmed that OB110462 was likely a black hole or neutron star.
Lu and Lam suspect that the differing conclusions of the two teams are due to the fact that the astrometric and photometric data give different measures of the relative motions of the foreground and background objects. The astrometric analysis also differs between the two teams. The UC Berkeley-led team argues that it is not yet possible to distinguish whether the object is a black hole or a neutron star, but they hope to resolve the discrepancy with more Hubble data and improved analysis in the future.
“As much as we would like to say it is definitively a black hole, we must report all allowed solutions. This includes both lower mass black holes and possibly even a neutron star,” Lu said.
“If you can’t believe the light curve, the brightness, then that says something important. If you don’t believe the position versus time, that tells you something important,” Lam said. “So, if one of them is wrong, we have to understand why. Or the other possibility is that what we measure in both data sets is correct, but our model is incorrect. The photometry and astrometry data arise from the same physical process, which means the brightness and position must be consistent with each other. So, there’s something missing there. “
Both teams also estimated the velocity of the super-compact lensing object. The Lu/Lam team found a relatively sedate speed, less than 30 kilometers per second. The STScI team found an unusually large velocity, 45 km/s, which it interpreted as the result of an extra kick that the purported black hole got from the supernova that generated it.
Lu interprets her team’s low velocity estimate as potentially supporting a new theory that black holes are not the result of supernovas — the reigning assumption today — but instead come from failed supernovas that don’t make a bright splash in the universe or give the resulting black hole a kick.
The work of Lu and Lam is supported by the National Science Foundation (1909641) and the National Aeronautics and Space Administration (NNG16PJ26C, NASA FINESST 80NSSC21K2043).
Journal
The Astrophysical Journal Letters
Method of Research
Observational study
Article Title
An isolated mass gap black hole or neutron star detected with astrometric microlensing
Yet black holes by their very nature can be very hard to detect, especially if they are isolated. After all, a black hole has such powerful gravity that light doesn’t escape, so we generally detect them by their gravitational influence on other objects or by radiation created by the surrounding matter they are devouring. Without nearby objects or accreting matter, there could be hundreds of millions of black holes throughout our galaxy that are essentially invisible to astronomers.
If, as astronomers believe, the death of large stars leaves behind black holes, there should be hundreds of millions of them scattered throughout the Milky Way galaxy. The problem is, isolated black holes are invisible.
Now, a team led by
The team, led by graduate student Casey Lam and Jessica Lu, a UC Berkeley associate professor of astronomy, estimates that the mass of the invisible compact object is between 1.6 and 4.4 times that of the sun. Because astronomers think that the leftover remnant of a dead star must be heavier than 2.2 solar masses in order to collapse to a black hole, the UC Berkeley researchers caution that the object could be a
Hubble Space Telescope image of a distant star that was brightened and distorted by an invisible but very compact and heavy object between it and Earth. The compact object — estimated by UC Berkeley astronomers to be between 1.6 and 4.4 times the mass of our sun — could be a free-floating black hole, one of perhaps 200 million in the Milky Way galaxy. Credit: Image courtesy of STScI/NASA/ESA
“This is the first free-floating black hole or neutron star discovered with gravitational microlensing,” Lu said. “With microlensing, we’re able to probe these lonely, compact objects and weigh them. I think we have opened a new window onto these dark objects, which can’t be seen any other way.”
Determining how many of these compact objects populate the Milky Way galaxy will help astronomers understand the evolution of stars — in particular, how they die — and of our galaxy, and perhaps reveal whether any of the unseen black holes are primordial black holes, which some cosmologists think were produced in large quantities during the
Because both microlensing surveys caught the same object, it has two names: MOA-2011-BLG-191 and OGLE-2011-BLG-0462, or OB110462, for short.
While surveys like these discover about 2,000 stars brightened by microlensing each year in the Milky Way galaxy, the addition of astrometric data is what allowed the two teams to determine the mass of the compact object and its distance from Earth. The UC Berkeley-led team estimated that it lies between 2,280 and 6,260 light years (700-1920 parsecs) away, in the direction of the center of the Milky Way Galaxy and near the large bulge that surrounds the galaxy’s central massive black hole.
The STScI group estimated that it lies about 5,153 light years (1,580 parsecs) away.
Looking for a needle in a haystack
Lu and Lam first became interested in the object in 2020 after the STScI team tentatively concluded that five microlensing events observed by Hubble — all of which lasted for more than 100 days, and thus could have been black holes — might not be caused by compact objects after all.
Lu, who has been looking for free-floating black holes since 2008, thought the data would help her better estimate their abundance in the galaxy, which has been roughly estimated at between 10 million and 1 billion. To date, star-sized black holes have been found only as part of binary star systems. Black holes in binaries are seen either in X-rays, produced when material from the star falls onto the black hole, or by recent gravitational wave detectors, which are sensitive to mergers of two or more black holes. But these events are rare.
“Casey and I saw the data and we got really interested. We said, ‘Wow, no black holes. That’s amazing,’ even though there should have been,” Lu said. “And so, we started looking at the data. If there were really no black holes in the data, then this wouldn’t match our model for how many black holes there should be in the Milky Way. Something would have to change in our understanding of black holes — either their number or how fast they move or their masses.”
When Lam analyzed the photometry and astrometry for the five microlensing events, she was surprised that one, OB110462, had the characteristics of a compact object: The lensing object seemed dark, and thus not a star; the stellar brightening lasted a long time, nearly 300 days; and the distortion of the background star’s position also was long-lasting.
The length of the lensing event was the main tipoff, Lam said. In 2020, she showed that the best way to search for black hole microlenses was to look for very long events. Only 1% of detectable microlensing events are likely to be from black holes, she said, so looking at all events would be like searching for a needle in a haystack. But, Lam calculated, about 40% of microlensing events that last more than 120 days are likely to be black holes.
“How long the brightening event lasts is a hint of how massive the foreground lens bending the light of the background star is,” Lam said. “Long events are more likely due to black holes. It’s not a guarantee, though, because the duration of the brightening episode not only depends on how massive the foreground lens is, but also on how fast the foreground lens and background star are moving relative to each other. However, by also getting measurements of the apparent position of the background star, we can confirm whether the foreground lens really is a black hole.”
According to Lu, the gravitational influence of OB110462 on the light of the background star was amazingly long. It took about one year for the star to brighten to its peak in 2011, then about a year to dim back to normal.
More data will distinguish black hole from neutron star
To confirm that OB110462 was caused by a super-compact object, Lu and Lam asked for more astrometric data from Hubble, some of which arrived last October. That new data showed that the change in position of the star as a result of the gravitational field of the lens is still observable 10 years after the event. Further Hubble observations of the microlens are tentatively scheduled for fall 2022.
Analysis of the new data confirmed that OB110462 was likely a black hole or neutron star.
Lu and Lam suspect that the differing conclusions of the two teams are due to the fact that the astrometric and photometric data give different measures of the relative motions of the foreground and background objects. The astrometric analysis also differs between the two teams. The UC Berkeley-led team argues that it is not yet possible to distinguish whether the object is a black hole or a neutron star, but they hope to resolve the discrepancy with more Hubble data and improved analysis in the future.
“As much as we would like to say it is definitively a black hole, we must report all allowed solutions. This includes both lower mass black holes and possibly even a neutron star,” Lu said.
“If you can’t believe the light curve, the brightness, then that says something important. If you don’t believe the position versus time, that tells you something important,” Lam said. “So, if one of them is wrong, we have to understand why. Or the other possibility is that what we measure in both data sets is correct, but our model is incorrect. The photometry and astrometry data arise from the same physical process, which means the brightness and position must be consistent with each other. So, there’s something missing there. ”
Both teams also estimated the velocity of the super-compact lensing object. The Lu/Lam team found a relatively sedate speed, less than 30 kilometers per second. The STScI team found an unusually large velocity, 45 km/s, which it interpreted as the result of an extra kick that the purported black hole got from the supernova that generated it.
Lu interprets her team’s low velocity estimate as potentially supporting a new theory that black holes are not the result of supernovas — the reigning assumption today — but instead come from failed supernovas that don’t make a bright splash in the universe or give the resulting black hole a kick.
Reference: “An isolated mass gap black hole or neutron star detected with astrometric microlensing” by Casey Y. Lam, Jessica R. Lu, Andrzej Udalski, Ian Bond, David P. Bennett, Jan Skowron, Przemek Mroz, Radek Poleski, Takahiro Sumi, Michal K. Szymanski, Szymon Kozlowski, Pawel Pietrukowicz, Igor Soszynski, Krzysztof Ulaczyk, Lukasz Wyrzykowski, Shota Miyazaki, Daisuke Suzuki, Naoki Koshimoto, Nicholas J. Rattenbury, Matthew W. Hosek Jr., Fumio Abe, Richard Barry, Aparna Bhattacharya, Akihiko Fukui, Hirosane Fujii, Yuki Hirao, Yoshitaka Itow, Rintaro Kirikawa, Iona Kondo, Yutaka Matsubara, Sho Matsumoto, Yasushi Muraki, Greg Olmschenk, Clement Ranc, Arisa Okamura, Yuki Satoh, Stela Ishitani Silva, Taiga Toda, Paul J. Tristram, Aikaterini Vandorou, Hibiki Yama, Natasha S. Abrams, Shrihan Agarwal, Sam Rose and Sean K. Terry, Accepted, The Astrophysical Journal Letters. arXiv:2202.01903
The work of Lu and Lam is supported by the National Science Foundation (1909641) and the National Aeronautics and Space Administration (NNG16PJ26C, NASA FINESST 80NSSC21K2043).
2004’s sequel to the original Baldur’s Gate: Dark Alliance — which saw a remastered release on Switch and other platforms back in May 2021 — is getting the same treatment; Baldur’s Gate: Dark Alliance 2 is pencilled in for a “Summer 2022” release on Switch and other platforms.
Developer Black Isle Studios teased earlier this year that it was coming “sooner than you think”. For Nintendo-exclusive gamers who never had an Xbox or PS2, this will be the first opportunity to play the action-RPG sequel as it skipped Nintendo platforms originally — a disappointment to GameCube owners who enjoyed the original Dark Alliance.
The game features five playable characters and classes across four difficulty levels. ranging from Easy to Extreme (our italics there, added for extreme emphasis).
Support for local co-op play is included, as you can see from this list of features from the official PR blurb:
Whether choosing the barbarian, monk, necromancer, rogue or cleric, players will have to actively fight through hordes of monsters ranging from Hobgoblins, Ghouls, Golems and dreaded Dragons while dodging attacks and evading deadly traps. Key Features: Hack your way or cast powerful spells through over 80 perilous levels Hidden areas, secret characters, and hundreds of items to discover, customize, and use Forge unique magical weapons and armor to maximize the damage you inflict in battle Conquer hordes of beasts and armies of Hobgoblins, Ghouls, Golems and dreaded Dragons Compelling single or two-player cooperative modes of play Four difficulty levels to challenge even the hardiest adventurer; “Easy”, “Normal”, “Hard” and “Extreme”. Fully voice-acted by an all-star cast and two secret characters; Drizzt Do’Urden and Artemis Entreri. Verified Steamdeck certification. Local co-op support! Fully voice-acted by an all-star cast
No word on a precise release date just yet, but we’ll let you know when we can.
Do you have good memories of this one? Will you be playing for the first time this ‘summer’? Let us know below.
Hubble Space Telescope image of a distant star that was brightened and distorted by an invisible but very compact and heavy object between it and Earth. The compact object—estimated by UC Berkeley astronomers to be between 1.6 and 4.4 times the mass of our sun—could be a free-floating black hole, one of perhaps 200 million in the Milky Way galaxy. Credit: Image courtesy of STScI/NASA/ESA
If, as astronomers believe, the deaths of large stars leave behind black holes, there should be hundreds of millions of them scattered throughout the Milky Way galaxy. The problem is, isolated black holes are invisible.
Now, a team led by University of California, Berkeley, astronomers has for the first time discovered what may be a free-floating black hole by observing the brightening of a more distant star as its light was distorted by the object’s strong gravitational field—so-called gravitational microlensing.
The team, led by graduate student Casey Lam and Jessica Lu, a UC Berkeley associate professor of astronomy, estimates that the mass of the invisible compact object is between 1.6 and 4.4 times that of the sun. Because astronomers think that the leftover remnant of a dead star must be heavier than 2.2 solar masses in order to collapse to a black hole, the UC Berkeley researchers caution that the object could be a neutron star instead of a black hole. Neutron stars are also dense, highly compact objects, but their gravity is balanced by internal neutron pressure, which prevents further collapse to a black hole.
Whether a black hole or a neutron star, the object is the first dark stellar remnant—a stellar “ghost”—discovered wandering through the galaxy unpaired with another star.
“This is the first free-floating black hole or neutron star discovered with gravitational microlensing,” Lu said. “With microlensing, we’re able to probe these lonely, compact objects and weigh them. I think we have opened a new window onto these dark objects, which can’t be seen any other way.”
Determining how many of these compact objects populate the Milky Way galaxy will help astronomers understand the evolution of stars—in particular, how they die—and of our galaxy, and perhaps reveal whether any of the unseen black holes are primordial black holes, which some cosmologists think were produced in large quantities during the Big Bang.
The analysis by Lam, Lu and their international team has been accepted for publication in The Astrophysical Journal Letters. The analysis includes four other microlensing events that the team concluded were not caused by a black hole, though two were likely caused by a white dwarf or a neutron star. The team also concluded that the likely population of black holes in the galaxy is 200 million—about what most theorists predicted.
Same data, different conclusions
Notably, a competing team from the Space Telescope Science Institute (STScI) in Baltimore analyzed the same microlensing event and claims that the mass of the compact object is closer to 7.1 solar masses and indisputably a black hole. A paper describing the analysis by the STScI team, led by Kailash Sahu, has been accepted for publication in The Astrophysical Journal.
Both teams used the same data: photometric measurements of the distant star’s brightening as its light was distorted or “lensed” by the super-compact object, and astrometric measurements of the shifting of the distant star’s location in the sky as a result of the gravitational distortion by the lensing object. The photometric data came from two microlensing surveys: the Optical Gravitational Lensing Experiment (OGLE), which employs a 1.3-meter telescope in Chile operated by Warsaw University, and the Microlensing Observations in Astrophysics (MOA) experiment, which is mounted on a 1.8-meter telescope in New Zealand operated by Osaka University. The astrometric data came from NASA’s Hubble Space Telescope. STScI manages the science program for the telescope and conducts its science operations.
Microlensing parallax πE vs. Einstein crossing time tE (left) and maximum astrometric shift δc,max (right). Points are from the PopSyCLE simulation. Contours are 1 − 2 − 3σ (39.3-86.5-98.9%) credible regions from the microlensing model fits to the five BH candidates. There are two fits for OB110462 (default weight (DW) and equal weight (EW).The OB110462 DW solution has a smaller πE than the OB110462 EW solution, and has a correspondingly more massive lens mass. Both solutions fall solidly in the NS-BH mass gap, making OB110462 the best BH-candidate. MB09260 and OB110310 are most likely white dwarfs or neutron stars, although due to uncertainty in πE and δc,max higher and lower mass lenses cannot be definitively ruled out. OB110037 and MB10364 are not BHs as they have very large πE, as well as relatively short tE and small δc,max. Credit: The Astrophysical Journal Letters (2022). DOI: 10.48550/arXiv.2202.01903
Because both microlensing surveys caught the same object, it has two names: MOA-2011-BLG-191 and OGLE-2011-BLG-0462, or OB110462, for short.
While surveys like these discover about 2,000 stars brightened by microlensing each year in the Milky Way galaxy, the addition of astrometric data is what allowed the two teams to determine the mass of the compact object and its distance from Earth. The UC Berkeley-led team estimated that it lies between 2,280 and 6,260 light years (700-1920 parsecs) away, in the direction of the center of the Milky Way Galaxy and near the large bulge that surrounds the galaxy’s central massive black hole.
The STScI group estimated that it lies about 5,153 light years (1,580 parsecs) away.
Looking for a needle in a haystack
Lu and Lam first became interested in the object in 2020 after the STScI team tentatively concluded that five microlensing events observed by Hubble—all of which lasted for more than 100 days, and thus could have been black holes—might not be caused by compact objects after all.
Lu, who has been looking for free-floating black holes since 2008, thought the data would help her better estimate their abundance in the galaxy, which has been roughly estimated at between 10 million and 1 billion. To date, star-sized black holes have been found only as part of binary star systems. Black holes in binaries are seen either in X-rays, produced when material from the star falls onto the black hole, or by recent gravitational wave detectors, which are sensitive to mergers of two or more black holes. But these events are rare.
“Casey and I saw the data and we got really interested. We said, ‘Wow, no black holes. That’s amazing,’ even though there should have been,” Lu said. “And so, we started looking at the data. If there were really no black holes in the data, then this wouldn’t match our model for how many black holes there should be in the Milky Way. Something would have to change in our understanding of black holes—either their number or how fast they move or their masses.”
When Lam analyzed the photometry and astrometry for the five microlensing events, she was surprised that one, OB110462, had the characteristics of a compact object: The lensing object seemed dark, and thus not a star; the stellar brightening lasted a long time, nearly 300 days; and the distortion of the background star’s position also was long-lasting.
The length of the lensing event was the main tipoff, Lam said. In 2020, she showed that the best way to search for black hole microlenses was to look for very long events. Only 1% of detectable microlensing events are likely to be from black holes, she said, so looking at all events would be like searching for a needle in a haystack. But, Lam calculated, about 40% of microlensing events that last more than 120 days are likely to be black holes.
“How long the brightening event lasts is a hint of how massive the foreground lens bending the light of the background star is,” Lam said. “Long events are more likely due to black holes. It’s not a guarantee, though, because the duration of the brightening episode not only depends on how massive the foreground lens is, but also on how fast the foreground lens and background star are moving relative to each other. However, by also getting measurements of the apparent position of the background star, we can confirm whether the foreground lens really is a black hole.”
According to Lu, the gravitational influence of OB110462 on the light of the background star was amazingly long. It took about one year for the star to brighten to its peak in 2011, then about a year to dim back to normal.
Following six years of meticulous observations, the NASA/ESA Hubble Space Telescope has provided, for the first time ever, clear evidence for a lone black hole drifting through interstellar space. This is the first time the mass of an isolated black hole has been measured. Credit: ESA/Hubble
More data will distinguish black hole from neutron star
To confirm that OB110462 was caused by a super-compact object, Lu and Lam asked for more astrometric data from Hubble, some of which arrived last October. That new data showed that the change in position of the star as a result of the gravitational field of the lens is still observable 10 years after the event. Further Hubble observations of the microlens are tentatively scheduled for fall 2022.
Analysis of the new data confirmed that OB110462 was likely a black hole or neutron star.
Lu and Lam suspect that the differing conclusions of the two teams are due to the fact that the astrometric and photometric data give different measures of the relative motions of the foreground and background objects. The astrometric analysis also differs between the two teams. The UC Berkeley-led team argues that it is not yet possible to distinguish whether the object is a black hole or a neutron star, but they hope to resolve the discrepancy with more Hubble data and improved analysis in the future.
“As much as we would like to say it is definitively a black hole, we must report all allowed solutions. This includes both lower mass black holes and possibly even a neutron star,” Lu said.
“If you can’t believe the light curve, the brightness, then that says something important. If you don’t believe the position versus time, that tells you something important,” Lam said. “So, if one of them is wrong, we have to understand why. Or the other possibility is that what we measure in both data sets is correct, but our model is incorrect. The photometry and astrometry data arise from the same physical process, which means the brightness and position must be consistent with each other. So, there’s something missing there.”
Both teams also estimated the velocity of the super-compact lensing object. The Lu/Lam team found a relatively sedate speed, less than 30 kilometers per second. The STScI team found an unusually large velocity, 45 km/s, which it interpreted as the result of an extra kick that the purported black hole got from the supernova that generated it.
Lu interprets her team’s low velocity estimate as potentially supporting a new theory that black holes are not the result of supernovas—the reigning assumption today—but instead come from failed supernovas that don’t make a bright splash in the universe or give the resulting black hole a kick.
First ever free-floating black hole found roaming through interstellar space
More information:
Casey Lam et al, An isolated mass gap black hole or neutron star detected with astrometric microlensing, The Astrophysical Journal Letters (2022). DOI: 10.48550/arXiv.2202.01903
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Aliens: Dark Descent has been announced, and it looks like a squad-based, top-down shooter.
Revealed at Summer Game Fest, Aliens: Dark Descent was revealed in a cinematic trailer very reminiscent of James Cameron’s take on the Aliens universe, with hordes of Xenomorphs hunting down a team of space marines.
The trailer ends with a brief look at the gameplay where squads of Marines are shown fighting off waves of Aliens in a top-down perspective.
It’s unclear how these marines will be controlled and whether it is co-op, but this appears to be taking a squad-based approach to combat rather than a solo adventure like in games like Alien: Isolation.
Aliens: Dark Descent – Summer Game Fest 2022
In 1986, James Cameron released a bigger and badder sequel with more Xenomorphs hunting down a larger team of armed space marines. It was a very different tone than the horror-vibe of Ridley Scott’s original Alien, but some prefer the different flavor of Cameron’s sequel,
Check out IGN for a full rundown of all the new announcements from Summer Game Fest.
Matt T.M. Kim is IGN’s News Editor. You can reach him @lawoftd.
In the 2000 science fiction film Pitch Black (now streaming on Peacock!), the prisoner Richard B. Riddick, is being escorted on a small spaceship which crash lands on an alien planet. Despite having three suns in the sky, a rare eclipse event bathes the planet in total darkness and the crash survivors find themselves at the mercy of a predatory alien species. Luckily, Riddick has surgically modified eyes which allow him to see clearly in the dark. If you’re going to find yourself on a lightless world with ravenous monsters, it helps to have a superpowered Vin Diesel in your corner.
Here on Earth, we also have a sort of superpower when it comes to seeing in the dark. The pupils in our eyes are capable of opening and closing as needed, depending on the amount of light we perceive. We can, quite literally, adjust our vision in order to match our environment. At least, that’s how we feel about what’s happening.
A new illusion comprised of a dark central hole surrounded by a gradient on a field — pictured above — presents evidence that our eyes aren’t actually reacting to the light in our environment. Bruno Laeng from the Department of Psychology at the University of Oslo, and colleagues, studied the new illusion designed by co-author Akyoshi Kitaoka. They found that looking at it caused most people’s pupils to dilate as if they were entering a darker environment. Their findings were published in the journal Frontiers in Human Neuroscience.
Laeng, the study’s lead author, previously studied another illusion created by Kitaoka which featured what appeared to be a bright light emerging from a gradient. Despite the fact that the center of that illusion is the same color and brightness as the background, its position within the gradient makes it appear and feel as if it is almost painfully bright.
“That led me to study the possibility that our eyes are actually adjusting to the illusions, not to the reality, but to what we think the reality is or is about to be,” Laeng told SYFY WIRE.
What’s striking about this new illusion is that even though it’s a totally static image, it creates a sense of movement toward the center, as if you’re moving into a dark hole or tunnel. It’s that sensation which causes your pupils to dilate. Your brain believes you’re about to enter into a darker environment and prepares your eyes to handle the decreased level of light it expects.
That tells scientists something about how our visual centers work, namely that they are building our picture of the world upon expectations, not upon actual physical stimuli. Ultimately, it’s for the best that our vision centers work this way. If they didn’t, we probably wouldn’t have survived very long. That’s because sometimes the world moves more quickly than our brains can process. It gets around that limitation by making informed estimates about the most likely outcome of events and feeding that information to you as if it already happened. Most of the time your brain’s predictive engines are right and you don’t notice. Illusions, however, mess with our wiring.
“This explains how we can react to events that happen at speeds which exceed the speed of the nervous system. That happens every day. You drive a car, or you play sports, you play tennis or table tennis, how can you do that? By the time the image of the ball hitting the table reaches the part of the brain that controls your planning of movement, it’s already several meters behind you. The solution is to correct by constructing the most probable representation of what the world would be like slightly in the future,” Laeng said.
That’s why 86% of people who look at this illusion have a physiological response and their pupils dilate. Your brain isn’t reacting to the level of light as it exists right now. It’s reacting to what it expects the level of light to be slightly in the future, and it expects the environment to be darker.
The remaining 14% of study participants didn’t have the same reaction, and that’s likely due to the way they process the image in their minds. If you remember the famous black and blue dress (or was it white and gold?) you have an idea of what’s happening here. The way you perceived the dress was dependent on some prior assumptions your brain made about whether it was photographed in full light or in shadow. The same thing might be happening here. Those individuals who don’t get the sensation of moving into a tunnel are making the correct prior assumption that the image is static. The rest of us are fooled by its visual trickery.
“We live in a virtual reality, really. What we see is what our nervous system is creating. Your solid belief in an incontrovertible reality and the reliability of your perceptions is not as it seems,” Laeng said.
If you were fooled by this new illusion, by the dress, or by any number of other illusions you may have encountered in your life, you shouldn’t feel bad. We are all, quite literally, making it up as we go along.
Out in the dark depths of space, our models of the Universe get messy. A new study looking at the ultra-diffuse dwarf galaxy AGC 114905 has revived a controversial theory (or more accurately a hypothesis) of gravity, and given us more questions than answers about what’s making our galaxies tick.
It all starts with dark matter – or in this case, no dark matter. Although most cosmologists agree there’s something out there called ‘dark matter’, causing spiral galaxies to rotate faster than they should, even dark matter doesn’t answer all the questions we need it to.
So, it’s not a bad idea to look at some alternative options. You know, just in case we are never able to find the stuff.
One alternative hypothesis to dark matter is called Modified Newtonian dynamics (MOND) or Milgromian dynamics framework. This hypothesis – first published in 1983 by physicist Mordehai Milgrom – suggests that we don’t need dark matter to fill in the Universe’s gravity gaps, if we calculate the gravitational forces experienced by stars in outer galactic regions in a different manner to how Newtonian laws suggest.
To test this idea, which involves working with proportionality to the star’s radius or centripetal acceleration, we need to be looking at the speeds of galaxies – specifically weird ones like ultra-diffuse galaxies.
These very faint, ugly ducklings of the galaxy world have a habit of not acting like a galaxy should. For example, some ultra diffuse galaxies seem to be made almost entirely of dark matter, whilst others are almost completely dark matter-less.
This is where AGC 114905 comes in. This ultra-diffuse dwarf galaxy around 250 million light years away had recently been looked at in detail in a paper published in 2021 investigating how fast it spins.
But this team found that the galaxy’s spin was extremely slow – slow enough that not only did they not need dark matter to confirm the models, but the rotation curve of the galaxy also cast huge doubt on the MOND framework. It doesn’t fit with either hypothesis.
“The very low reported rotation speed of this galaxy is inconsistent with both MOND and the standard approach with dark matter,” says University of St Andrews physicist and one of the researchers of the new paper, Hongsheng Zhao.
“But only MOND is able to get around this apparent contradiction.”
The new paper has ‘un-debunked’ the 2021 finding, suggesting that the issue isn’t with MOND, but instead with the inclination of the galaxy itself.
When we look at galaxies far away in the depths of space, it can sometimes be hard to confirm which angle we’re seeing. The original team found that AGC 114905 looked elliptical, suggesting that we’re looking at the galaxy from an angle.
But using simulations, researchers now suggest the galaxy could appear elliptical even when it’s facing us straight on. A change in the angle of the galaxy to us would also change how fast the galaxy is rotating, making all the MOND math add up after all.
“Our simulations show that the inclination of AGC 114905 might be significantly less than reported, which would mean the galaxy is actually rotating much faster than people think, in line with MOND expectations,” says lead author of the new paper, physicist Indranil Banik, also from the University of St Andrews.
Now, this is still an open question. We don’t know whether this new paper, or the 2021 paper is going to be crowned victorious – or at least most correct.
In the meantime, if this new finding holds, it seems that the MOND framework might live on for another day. As wild as MOND might be, with dark matter still elusive, and many other questions still to be answered, we need all the options we can get.
The research has been published in the Monthly Notices of the Royal Astronomical Society.
