Together with 40 other research institutions worldwide, the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS) released its latest discoveries on Wednesday, including the brightest gamma-ray burst (GRB) ever detected by humans.
With the unique observations made by two Chinese space telescopes, namely Insight-HXMT and GECAM-C, scientists were able to accurately measure how bright the burst was and how much energy it released.
Nearly 10,000 gamma-ray bursts have been detected since the first was detected in 1967. The mechanism of gamma-ray bursts and the radiation mechanism are still a mystery.
China’s first homegrown X-ray telescope, the Insight-HXMT, was launched in 2017 to observe celestial sources of X-rays.
As the most energetic explosion phenomenon in the universe, GRBs can be produced by the core collapse of a massive star or the merger of two compact stars. The latest burst, dubbed GRB 221009A, belongs to the former category. A GRB typically lasts less than two seconds and usually emits gravitational waves.
With the Insight-HXMT and GECAM-C space telescopes, an IHEP-led international team with researchers from over 30 institutes from China, the US, Italy, France and Germany, has made accurate measurements of the prompt emission and early afterglow of this unprecedented burst in the hard X-ray and soft gamma energy bands.
“It is a beautiful example of collaboration,” said Andrea Santangelo, professor of the University of Tuebingen. “And this will give leadership to China, Germany, and all the parties involved in the project in this field. Leadership is not just a political word. Leadership means that in the next 10 years, we expect to reach fantastic discoveries because nature will give us the possibility,” he noted.
“Based on the accurate data obtained by GECAM-C, we found that this burst set new records for both the observed brightness and the isotropic-equivalent energy of all detected bursts, making this burst exceptional,” Xiong Shaolin, the principal investigator of GECAM-C who led this study, told the Global Times on Wednesday. “This burst was 50 times brighter than the last record-holder,” Xiong added.
According to the joint observation by Insight-HXMT and GECAM-C, the early afterglow of GRB 221009A appeared to switch from slow decay to rapid decay very early in time, meaning that this burst launched an extremely narrow and luminous jet.
“These findings shed new light on the physics of these energetic explosions in the universe,” Bing Zhang, professor at the University of Nevada in Las Vegas, who led the theoretical interpretation in the project told the Global Times. “More detailed modeling is needed to understand how GRB engines manage to collimate the jets to produce such a huge isotropic equivalent energy in some cases.”
Filippo Frontera, principal investigator of the European BeppoSAX satellite payload Phoswich Detector System (PDS) and Gamma Ray Burst Monitor (GRBM), told the Global Times that the results obtained for GRB 221009A are unique among the numerous observations collected on this event. “The exceptional quality of such data is the result of smart design of the instruments aboard the HXMT and GECAM missions, which could be achieved only by a very experienced group,” he said.
China’s manned submersible Shenhai Yongshi (Deep-sea Warrior) placed underwater permanent survey markers at the core areas of two Ming Dynasty-era sunken ships in the South China Sea after conducting preliminary search and image recordings on Saturday, opening a new chapter in China’s deep-sea archaeology.
An underwater archaeological investigation formally kicked off on Saturday for the two ships discovered last October in the South China Sea, said China’s National Cultural Heritage Administration on Sunday.
The two ships were discovered in October 2022 in the South China Sea at a depth of about 1,500 meters. One site is mainly composed of about 100,000 porcelain relics. Based on a preliminary survey, the ship may have sunk during the Emperor Zhengde period (1506-21) of the Ming Dynasty.
The other site has a large number of timber logs, and the ship is believed to have been carrying overseas cargoes to China, dating back to the Emperor Hongzhi period (1488-1505) of the Ming Dynasty.
Archaeologists said the systematic archaeological investigation will last for about a year in three phases.
The first phase began on Saturday and will last until early June. Manned submersibles will be released to determine the distribution range of the sites for multi-angle and comprehensive data collection and archaeological recording, and to extract specimens of representative cultural relics and samples of the seabed sediment.
The second and third phases are planned to be implemented from August to September in 2023 and from March to April in 2024. After the archaeological surveys, the next step will be proposed on the basis of the sunken ships’ status and technical conditions.
The investigation of the two shipwrecks will provide evidence of ancient Chinese people’s activity in the South China Sea, making breakthroughs in the study of Chinese maritime history, ceramic history, overseas trade history and the Maritime Silk Road.
Shenzhou-16 crew members Jing Haipeng, Zhu Yangzhu and Gui Haichao successfully completed all the assigned tasks and safely returned to the space research module with the support of the robotic arm after about eight hours of their first extravehicular activity (EVA), the China Manned Space Engineering Office (CMSA) said on Thursday.
During the spacewalk, the astronauts completed tasks including bracket installation and lifting of panorama camera B in the core module and the unlocking and lifting of panorama cameras A and B of the Mengtian lab module.
Jing and Zhu went out for the spacewalk. Zhu has become the first space flight engineer to perform an EVA.
The Shenzhou-16 crew will also carry out a number of space science experiments and conduct multiple EVAs.
The Shenzhou-16 crew is composed of three types of astronauts: commander, flight engineer, and payload expert. They have been in orbit for 51 days since they entered the space station on May 30.
According to the CMSA, the radiation biology exposure experiment is significant for ensuring a healthy long-term stay in orbit for astronauts and promoting China’s crewed lunar landing plans.
With the installation of gas cylinders in the electric propulsion system in orbit, this is the first time the “gas exchange” method has been used to complete the replenishment of electric propellants for long-term orbit maintenance of the space station, making its operation more economic and efficient.
The CMSA said the Shenzhou-16 crew are in good condition, and the space station is running stably.
China launched the Shenzhou-16 manned spacecraft on May 30, sending three astronauts to its space station for a five-month mission.
In a new campaign to combat new types of illegal activities across telecommunications networks, as well as to punish cross-border illegal activities, the Xi’an police from Northwest China’s Shaanxi Province on Wednesday issued a disciplinary notice and disclosed information regarding more than 20 individuals from Chang’an district who are moving across areas such as northern Myanmar, the Golden Triangle, the United Arab Emirates, and Cambodia.
Starting from the date of the notice, these individuals who are illegally located overseas and involved in high-risk fraud are required to voluntarily return to China through proper channels before September 10, 2023. Within 14 days prior to their return, they must report to the local police station in their registered residence on their own or through their family members, the notice said.
Family members of those who are still stranded overseas and involved in high-risk fraud should actively cooperate with the public security organs, promptly contact and urge these individuals to return to China and surrender themselves. Those who voluntarily surrender and truthfully confess to their illegal activities may receive lenient or mitigated punishments according to law. Those with minor offenses may be exempted from punishment according to the law. However, those who persist in their refusal to return to China after the deadline will be subject to investigation and pursuit through legal means, the notice warned.
Xi’an police stated that the over 20 individuals involved in fraud will be publicly exposed and strictly punished according to the law. Their household registration will be frozen, and all household registration-related services, such as identity cards and driving licenses, will be suspended. Communication and banking services will be strictly controlled. All mobile phone cards will be deactivated, and non-counter services of their bank cards will be suspended. All government policy subsidies, social welfare benefits, and national assistance guarantees will be suspended.
Moreover, when these individuals or their direct three-generation family members undergo political reviews for joining the Communist Youth League, the Communist Party of China, joining the military, or applying for civil service positions or positions in public institutions, their reviews will be strictly conducted in accordance with the law and regulations.
Furthermore, the Xi’an police emphasized in the notice that any unit, organization, or individual that provides safe harbor, financial resources, transportation, or information, or engages in forgery, cover-ups, or other facilitation to help these individuals involved in overseas illegal activities evade punishment will be held legally accountable.
Two months after a “rebellion” by the Wagner Group was quickly quelled, the leader of the private military company Yevgeny Prigozhin was reportedly killed in a plane crash, leaving a trail of shock, mystery and speculation over the incident.
As of press time, the Kremlin did not release any details about the incident, which is still under investigation. However, Russia’s rivals, including the US and Ukraine, have pointed the finger at Russian President Vladimir Putin. Experts believe that although the existence of Prigozhin posed risks to all parties, the US and its allies are using the incident to launch a wave of public opinion and cognitive warfare against Russia in order to create more chaos and instability.
Russia’s Federal Agency for Air Transport confirmed on Wednesday that Prigozhin was killed in a plane crash in the Tver Region near Moscow. According to the name list released by the agency on its Telegram account, Prigozhin, as well as his right-hand man Dmitry Utkin, were among the 10 people who lost their lives in the crash earlier Wednesday.
The agency said earlier that an investigation had been launched into the cause of the plane crash.
The Telegram account Grey Zone linked to Wagner also reported Prigozhin’s death late on Wednesday, saying that the head of the Wagner Group “died as a result of the actions of traitors to Russia.”
US President Joe Biden said that he is “not surprised” about the incident, and strongly hinted at Putin’s involvement, according to media reports.
Mykhailo Podolyak, Ukrainian presidential adviser, directly named Putin as being right behind the “demonstrative elimination” of Prigozhin, which is “a signal to Russia’s elites ahead of the 2024 elections.”
The prime minister of Estonia Kaja Kallas, Polish foreign minister Zbigniew Rau, and chair of the UK Parliament’s Foreign Affairs Committee Alicia Kearns also suggested Russian president’s involvement to “eliminate opponents.”
Chinese experts said that based on public information and video materials so far, there was little chance that Prigozhin’s death was just an accident. They added that continuous debate and recriminations are inevitable regardless of the final outcome of the Russian investigation, as Prigozhin’s existence generally posed a kind of “threat” to all sides.
Zhao Long, deputy director of the Institute of Global Governance at the Shanghai Institute for International Studies, told the Global Times that for the US, although the “Wagner rebellion” created chaos in Russia, the group’s influence in Africa is an obstacle to the US’ global strategic layout. Wagner’s bloody campaign in Bakhmut and its deterrence also led NATO countries to identify Prigozhin as a threat.
Ukraine had called for Prigozhin to be held accountable over “war crimes”, and his death coincides with Ukraine’s warning of retaliation against Russia on Kiev’s Independence Day, Zhao said.
In addition, internal strife within Wagner and the conflict between Prigozhin and the Russian Defense Ministry may also have been factors and even motives leading to the “accident,” Zhao said.
While the results of the investigation are still not clear, the US and its allies pointed the finger at Putin, which is aimed at discrediting him at home and disrupting Russia’s internal unity and stability, Chinese military expert Song Zhongping told the Global Times.
This is cognitive and information warfare against Russia launched by the West, Song added.
The Kremlin needs more trust from Russian society, including confidence in winning the war and confidence in domestic order and security, some other experts commented, adding that there may be more attempts and actions aimed at undermining this trust.
When the plane crash took place, Putin appears to have been attending a concert in the city of Kursk to mark the 80th anniversary of the victory in the Battle of Kursk — the Soviet Union’s victory over Nazi Germany, according to media reports. Video clips on Twitter shows the Russian President’s motorcade speeding through Moscow toward the Kremlin after his trip to Kursk.
Zhang Hong, an associate research fellow at the Institute of Russian, Eastern European and Central Asian Studies of the Chinese Academy of Social Sciences, said that Russia is likely to investigate the incident before choosing a new head of Wagner.
If those responsible were Russian side, the appointment of a successor by the Russian government would provoke a revolt from some senior personnel in Wagner, but if the West was responsible, the impact on Russian domestic affairs would likely be limited, Zhang said.
According to experts, after the Prigozhin incident, the Russian legislature is likely to pass a new bill to fully regulate the activities of private military companies, and the Russian defense authorities may speed up the “recruitment” and integration of most Wagner personnel, and may also supervise and punish those who refuse to carry out orders through a unified military decision-making and command system.
The incident is unlikely to have a huge impact on the Russia-Ukraine battlefield, Zhao said, noting that Wagner’s offensive role in Bakhmut does not play a prominent part in the Russian military’s current strategic thinking of constantly depleting Ukraine’s military.
The Russia-Ukraine conflict is a strategic game between Russia and US-led NATO. Since the “rebellion,” Wagner is no longer the main force of the Russian military, Zhang said.
Waterlily beetles (Galerucella nymphaeae) literally fly across water, high speed videography and a bit of mathematical modeling reveals.
The beetles have a combination of hydrophobic hairs that line their legs and hydrophilic claws that grip the surface of water without getting too wet. Prior to “take off,” the insects lift their middle pair of legs. Then, the insects beat their wings extremely fast and fly horizontally across a pool of water. It looks a lot like water-skiing. In lab tests, waterlily beetles reached 0.5 meters per second — without an active brake system. Surface tension keeps the insects afloat, they found. The insects create ripples in the water, which generates drag at speeds greater than 0.23 meters per second (more drag than when the beetles just fly through air). Thus, for these beetles, skiing across a pond at breakneck speeds costs a lot of energy and requires greater wing thrust than normal flying. However, this mode of getting around could be more advantageous for foraging and help them avoid underwater predators like fish, the researchers speculate March 2 in the Journal of Experimental Biology.
After the Exxon Valdez dumped more than 10 million gallons of oil into the Gulf of Alaska, hairdresser Phil McCrory got an idea.
He gathered up human hair from his salon, stuffed it into a pair of pantyhose and dunked the bundle into a solution of motor oil and water. The hair sopped up the oil — a discovery that has since inspired environmentalists to create “hair blankets” to clean up oil spills. It’s not the most bizarre use of hair that Kurt Stenn describes in his new book, Hair: A Human History, or even the most surprising. From the felted wool covers of tennis balls to the horse-tail hair of a violin’s bow, Stenn, a former dermatologist and hair follicle scientist, digs up the myriad ways that hair has threaded its way into humans’ lives — and history.
A thriving wool trade starting in the 13th century, for example, helped some Italians amass enough wealth to later support famous artists of the Renaissance, including Michelangelo. And in 17th century Europe, beaver fur was so in demand (felted hats were a must for stylish gentlemen) that traders hunted beavers to near extinction.
Stenn jams an encyclopedia’s worth of material into a mere 256 pages, all the while shedding facts like a golden retriever sheds fur. But the book has more than just history. Stenn details the molecular biology of hair, those packed piles of cells that push out of nearly every square inch of human skin (except for the palms, soles and a few other areas). Hair conditioner, he explains, works by leaving positively charged molecules on strands, so that they repel each other rather than tangling together.
Stenn roots his story in science, discussing evolution, development and disease, among other topics. (The book could give readers a sure win for any hair category on Jeopardy!.) But Hair shines when Stenn steps out of the lab and into the world. He visits a wigmaker’s workshop in London, tours a modern barbering institute in Pennsylvania and learns about synthetic fibers at the laboratories of a Tokyo-based wig company.
These interludes are subtle highlights in a densely woven tale. But throughout, Stenn manages to convey a sense of wonder for a seemingly mundane material so tough, so strong and so versatile that it can be used for virtually anything — even mopping oil from the sea.
Ancient Assyrians sent their dead to the afterlife with fearsome companions: turtles. Excavations of a burial pit in southeastern Turkey revealed skeletons of a woman and a child, plus 21 turtles, a team led by archaeologist Rémi Berthon of France’s National Museum of Natural History reports in the February Antiquity.
The burial is part of an Assyrian site called Kavuşan Höyük that dates to between 700 and 300 B.C. The turtle bonanza included shells from one spur-thighed tortoise (Testudo graeca) and three Middle Eastern terrapins (Mauremys caspica), plus bones from 17 Euphrates soft-shelled turtles (Rafetus euphraticus). Butchering marks on the R. euphraticus bones indicate that the turtles may have been eaten in a funerary feast, Berthon and his colleagues write. Back then, turtles were not a regular meal in Mesopotamia. Turtle bones, however, were thought to ward off evil. The abundance of R. euphraticus turtles, a notoriously aggressive species, in this burial pit suggests the deceased had high social status.
To ancient Assyrians, these ferocious reptiles probably represented eternal life and served as psychopomps — mythical guides to the afterlife, the team writes.
Editor’s Note: This story was updated on 4/15/16 to note that turtles were a rare part of the Mesopotamian diet.
Earth sciences reporter Thomas Sumner recalls seeing the documentary film An Inconvenient Truth when he was in high school. The climate science presented in the movie didn’t surprise him too much — a science-minded student, he had already read about many of the issues. But, he says, the film started a broader dialog about global warming. “People started caring,” he says, noting that he remembers his own family talking about it (and not always harmoniously) at the time. Revisiting the dramatic predictions made in the film proved an interesting journey for Sumner. “The main criticism I heard was that the film had watered down the science,” he says. Climate science is amazingly complex, and so is modeling effects of change — from how much sea level might rise to how a warming climate could alter hurricane patterns. Even more striking to Sumner were the sheer number of uncertainties that remain. Those uncertainties are not about whether the climate is changing, but about the details of what such changes will mean for the oceans, the atmosphere and the living things on land — and when the various dominoes might fall. Telling the future is hard, especially about interrelated complex systems, but as Sumner reveals in his story, scientists have made steady progress in the last decade.
Another interesting point is the documentary’s (and Al Gore’s) role in politicizing climate science, which is fair to assume was one of the aims. “Gore was polarizing,” Sumner says. “He created a conversation about global warming, but he also cemented it as a political issue.”
Teeth and gums are neither political nor talked much about. But, as contributing correspondent Laura Beil reports, scientists studying a possible role for gum disease in what ails the body must contend with a slew of uncertainties, not unlike those faced by climate scientists. The bacteria that cause gum disease, some studies find, can travel to the arteries, heart, brain and other sites where they can cause havoc. Not all studies agree, and proving the oral bacteria–disease link beyond a doubt may not yet be within scientists’ grasp. But the fix is relatively simple, even if avoided by many: frequent flossing and regular visits to the dentist.
Keeping things simple was the underlying goal of the team of scientists attempting to build, from scratch, a synthetic organism with the least possible number of genes, as Tina Hesman Saey reports. After many tries, the effort succeeded, but not without first humbling the researchers involved. In the initial attempts, their computer-designed minimal genomes didn’t take. What ultimately worked was putting back some of the unknowns — genes with no known cellular job to do. Only then did the DNA inserted into the shell of a microbial cell yield a synthetic microbe capable of growing and reproducing.
Telling a good story about complex science, whether in a film or in a report on the latest research, requires some simplification. But sometimes the most interesting part lies in the uncertainty.
Our galaxy is teeming with planets. Over the last 25 years, astronomers have cataloged about 2,000 worlds in 1,300 systems scattered around our stellar neighborhood. While most of these exoplanets look nothing like Earth (and in some cases, like nothing that orbits our sun), the bonanza of alien worlds implies a tantalizing possibility: There is a lot of real estate out there suitable for life.
We haven’t explored every corner of our solar system. Life might be lurking beneath the surface of some icy satellites or in the soil of Mars. For such locales, we could conceivably visit and look for anything wriggling or replicating. But we can’t travel (yet) to worlds orbiting remote suns dozens of light-years away. An advanced alien civilization might transmit detectable radio signals, but primitive life would not be able to announce its presence to the cosmos. At least not intentionally. On Earth, life alters the atmosphere. If plants and critters weren’t around to keep churning out oxygen and methane, those gases would quickly vanish. Water, carbon dioxide, methane, oxygen and ozone are examples of “biosignatures,” key markers of a planet crawling with life as we know it. Setting aside questions about how recognizable alien life might be, detecting biosignatures in the atmosphere of an exoplanet would give astronomers the first strong clue that we are not alone. Biosignatures aren’t proof of thriving ecosystems. Ultraviolet light from a planet’s sun can zap water molecules and create a stockpile of oxygen; seawater filtering through rocks can produce methane. “We’ll never be able to say 100 percent that a planet has life,” says Sarah Rugheimer, an astrophysicist at the University of St. Andrews in Scotland. But astronomers hope that, given enough information about an exoplanet and the star it orbits, they can build a case for a world where sunlight and geology aren’t enough to explain its chemistry — one where life is a viable possibility. Finding a planet similar to Earth is probably still decades away, but thanks to a couple of upcoming telescopes, astronomers might be on the verge of spying on habitable worlds around nearby stars.
NASA’s Transiting Exoplanet Survey Satellite, or TESS, will launch in 2017 on a quest to detect many of the exoplanets that orbit the stars closest to us. One year later, the James Webb Space Telescope will launch and peek inside some of these newfound atmospheres. With their powers combined, TESS and James Webb could identify nearby planets that are good candidates for life. These worlds will probably be quite different from Earth — they’ll be a bit larger and orbit faint, red suns — but some researchers hope that a few will offer hints of alien biology. Eyes on the sky Over the next decade, several telescopes will join existing observatories in the hunt for exoplanets and hints of alien life.
Exoplanets don’t give up their secrets easily; they are distant, tiny and snuggled up to blazing stars. With some exceptions, current telescopes can’t directly see exoplanets, so astronomers use other means to infer their existence. In rare cases, a remote solar system is oriented so that its planets pass between their sun and Earth, an event known as a transit. During a transit, the star temporarily dims as a planet blocks some of its light.
Transits are powerful tools; not only can they help reveal a planet’s density — a way to distinguish gas planets from solid ones — but they also can allow astronomers to inventory the molecules floating in an exoplanet’s atmosphere. During a transit, molecules in the planet’s atmosphere absorb certain wavelengths of the star’s light, leaving a chemical fingerprint. By deciphering that fingerprint, researchers can deduce the chemical makeup of an alien world.
Pushing Hubble Astronomers so far have used the transit technique primarily with space-based telescopes such as the Hubble Space Telescope to investigate the atmospheres of more than 50 exoplanets, most of them worlds the size of Jupiter and Neptune (SN: 11/15/14, p. 4). The puffy atmospheres of giant planets are easier to detect than the relatively slim atmospheres of small rocky worlds. As tools have improved, researchers have started to check out super-Earths, planets that are smaller than Neptune but larger than ours. Though no such planets exist in our solar system, they appear to be one of the most common types in the galaxy.
Only three super-Earths have come under telescope scrutiny so far: GJ 1214b, HD 97658b and 55 Cancri e. These worlds are nothing like Earth. Two of them orbit dim, red suns, all of them whip around their stars in a few days (or even hours) and none are in the coveted habitable zone — the region around a star where a planet’s temperatures are just right for liquid water. Around GJ 1214b and HD 97658b, astronomers found no signs of molecules absorbing starlight, leading researchers to conclude that both worlds are blanketed in clouds or haze (SN Online: 1/2/14).
In February, researchers reported signs of hydrogen cyanide on 55 Cancri e. If confirmed, it would be the first detection of any molecule in the atmosphere of a super-Earth. “These are very challenging measurements, at the limit of [the Hubble Space Telescope’s] capabilities,” cautions Heather Knutson, an astrophysicist at Caltech. “We’re still learning about the performance of the telescope at this level of precision.”
Astronomers will undoubtedly try to squeeze more information out of similar worlds. But, says Kevin France, an astrophysicist at the University of Colorado Boulder, “we’ve pushed Hubble about as far as we can.” And Hubble won’t be around forever (SN: 4/18/15, p. 18). To continue sniffing around in exoplanet atmospheres, researchers are looking toward Hubble’s successor, the James Webb Space Telescope.
James Webb “is going to be a revolution in astronomy,” says Jonathan Lunine, an astrophysicist at Cornell University. The infrared observatory boasts a mirror 2.7 times as wide as Hubble’s. James Webb will seek out the first generation of stars, track how galaxies grow and — most relevant to the search for life — poke around in planetary atmospheres. Analyzing the atmospheres of planets the size of Neptune and Jupiter should be a breeze for James Webb. These large planets block enough light to make transits readily detectable, and the fluffy atmospheres are easier to measure. Super-Earths, which are smaller with thin atmospheres, are more challenging, but James Webb should be able to investigate a few. Although replicas of Earth are beyond even James Webb’s capabilities, there will be plenty for the observatory to do. “Even if we can’t get biosignatures on planets the size of Earth, we’re going to find out so much about the nature of exoplanets,” Lunine says. “It’s going to open up a huge number of doors.”
The trouble with an Earth-like world is that it doesn’t transit often and both the planet and its atmosphere are tiny. It’s the same kind of problem an alien group would experience trying to detect us. When viewed from afar, Earth blocks less than 0.01 percent of the sun’s light, and only a few percent of that is due to the atmosphere. To an alien astronomer, Earth crosses the sun once a year for, at most, 13 hours. And that’s assuming the aliens live in the right part of the galaxy to witness an Earth transit. Telescopes operated by the bulk of the Milky Way’s citizens will never line up with both the sun and Earth.
Focus on M dwarfs The odds of finding life improve if astronomers focus their efforts on M dwarfs, which make up about three-quarters of the stars in the galaxy. The dim red orbs are small, so a transiting planet blocks a relatively large fraction of the star’s light, making transits easier to detect. Habitable worlds also transit more frequently. To sustain liquid water, a planet must huddle close to one of these cool stars to stay warm. An orbit in the habitable zone of an M dwarf is much shorter than a comparable trip around the sun. Rather than wait for a year between transits, astronomers might have to wait for only a few weeks or months. Plus, a planet on a cozy orbit is more forgiving when it comes to getting the viewing geometry just right to see a transit. There are potential downsides to M dwarfs. Most of the light they radiate is infrared, so photosynthesis on orbiting planets would be very different compared with photosynthesis on Earth. There’s no guarantee that biosignatures from vegetation that thrives on infrared light would look anything like those from local varieties. Many M dwarfs also emit occasional blasts of ultraviolet radiation — blasts made even more dangerous because any habitable planet sits close to the star. Habitable worlds need to be so close, in fact, that the star’s gravity might prevent the planet from rotating, which could give rise to extreme climate differences between day and night. Recent research, though, indicates that none of these issues are necessarily deal breakers (SN: 2/7/15, p. 7). “There’s no reason why a planet around an M star couldn’t be like Earth,” says Lisa Kaltenegger, an astrophysicist at Cornell.
James Webb should be able to poke around in the atmospheres of a few habitable super-Earths around M dwarfs, though it’s going to need some targets first (SN: 5/17/14, p. 6). NASA’s premier planet hunter, the Kepler space telescope, (SN: 12/27/14, p. 20) found 1,039 exoplanets during its four-year primary mission, with 4,706 additional candidates awaiting confirmation. But most of Kepler’s finds are too distant for James Webb. That’s where TESS comes in. It will catalog all the short-period transiting worlds around the sun’s nearest neighbors. “Those are the ones that astronomers even decades from now are going to want to focus on,” says George Ricker, an MIT astrophysicist and principal investigator for the TESS mission.
Unlike Kepler, which gazed in one direction at 150,000 stars, TESS will spend two years monitoring 200,000 stars all around the sky. To cover that much ground, TESS will stare at one spot for about 27 days before moving onto a new patch. That’s not great for finding Earth twins on year-long orbits, but it’s good for finding worlds in the habitable zones of M dwarfs.
Based on Kepler’s results, astrophysicist Peter Sullivan, then at MIT, and colleagues calculated in 2015 that TESS should discover about 1,700 exoplanets. Of these, more than 500 could be less than twice the size of Earth, of which about 50 would lie in the habitable zones of their host stars. But picking biosignatures, or any signatures, out of those atmospheres is going to be difficult. Estimates vary, but James Webb will need roughly 200 hours to study one super-Earth around a nearby M dwarf, and those hours count only when the planet is passing in front of its star.
There’s a debate happening right now over how hard to chase that dream, Caltech’s Knutson says. Given its sluggish pace, James Webb might get to look at only a couple of habitable super-Earths. Astronomers could lavish large amounts of time on one or two systems that might not even pan out. Or they could focus telescope resources on Neptunes, Jupiters or hot super-Earths, where researchers can amass a lot of other data about a wide variety of worlds. While James Webb might get lucky and spy some biosignatures, the dream of finding another planet like Earth will probably have to wait a few decades for a larger observatory to come along. Snapping a pic The transit technique is powerful but inefficient. From our vantage point, most planets don’t transit their suns, and those that do transit only once every orbit.
“To really give us the best probability of detecting life, we need to build a telescope that can do direct detection,” Rugheimer says. Direct detection requires snapping a picture of an exoplanet and looking for biosignatures such as oxygen and methane imprinted on light reflecting off its surface. Since this technique doesn’t require alignments between planets and suns, it can, in principle, work for any world around any star. But to catch an Earth 2.0, astronomers are going to need a bigger telescope.
Consider again those aliens who are looking for us. They would struggle to see Earth even if they set up camp 4.2 light-years away at the star next door, Proxima Centauri (an M dwarf, by the way). It’s like trying to see the head of a quilting pin 28 meters to the right of a basketball while standing about 7,500 kilo-meters away — roughly the distance from Honolulu to Pittsburgh. And the basketball is 10 billion times as bright as the pin.
No observatories come close to being able to capture an image of an Earth-like planet around a sunlike star. But astronomers are thinking about what it would take. One idea is to put a gigantic mirror in space equipped with a device that can block the light of the star, such as the High-Definition Space Telescope proposed by the Association of Universities for Research in Astronomy. To see a few dozen Earth twins and characterize their atmospheres, that telescope would need a mirror 12 meters across. That’s bigger than any optical telescope currently on the ground and has 25 times the light-collecting area of Hubble.
Such an observatory “would be a huge undertaking relative to what we’ve done in space before,” Lunine says. “But relative to other programs this country has undertaken, it’s not.” One of the keys to success with the high-definition telescope is a coronagraph, a disk that blocks the light from any star the telescope points at. Many telescopes already use coronagraphs, especially spacecraft designed to look at the sun. James Webb will be outfitted with a coronagraph, though not one designed to search for other Earths.
The downside to a coronagraph is that it requires exceptional control of light that enters the telescope, which complicates the design. Other proposals to detect Earth-like planets, such as the NASA-commissioned Exo-S concept, use a starshade, a separate spacecraft shaped, appropriately, like the petals of a sunflower. The starshade flies tens of thousands of kilometers away from the telescope and maintains perfect alignment to prevent starlight from hitting the mirror (SN: 7/12/14, p. 11).
Since a starshade is free-floating and does all the lightsuppression work, it should be able to partner up with any telescope, even a relatively small one already in use. But no one has attempted formation flying in space at this scale. And every time astronomers want to look at a new star, the starshade would have to move around the telescope to maintain alignment, which could take days or weeks. All that movement will require fuel, which limits how many stars astronomers can search. Today these missions and others like them exist only in papers and PowerPoint slides posted online. The concepts, the fruits of a community-wide brainstorming session on how to allocate funding in the 2030s and beyond, will require massive financial and logistical resources, but some astronomers think it will be worth it once TESS and James Webb can point to where the nearest habitable locales might be. “Once we know where the potential habitable worlds are in our sky, I hope that will change a lot of people’s curiosity,” Kaltenegger says. “I would want to know if there are other habitable worlds. I wouldn’t want to just guess.”
Everyone agrees that finding a world teeming with life elsewhere in the galaxy is going to be exceptionally difficult. “Maybe nature needs to be on our side,” says Mark Clampin, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “But it won’t stop people from trying very hard. And we’ll probably make a lot of discoveries along the way.”