Comets from other star systems, such as 2019 Borisov, visit the sun’s neighborhood more frequently than scientists had thought, a new study suggests.
The study, based on data gathered as Borisov zipped by Earth at a distance of about 185 million miles (300 million kilometers) in late 2019, suggests that the comet repository in the far outer solar system known as the Oort Cloud might be full of objects that were born around other stars. In fact, the authors of the study suggest that the Oort Cloud might contain more interstellar material than domestic stuff.
Named after famous Dutch astronomer Jan Oort, who first proved its existence in the 1950s, the Oort Cloud is a spherical shell of small objects — asteroids, comets and fragments — far beyond the orbit of Neptune. The cloud’s inner edge is thought to begin about 2,000 astronomical units (AU) from the sun, and its outer edge lies about 200,000 AU away. (One AU is the average Earth-sun distance — about 93 million miles, or 150 million kilometers.)
No spacecraft has ever visited the Oort Cloud, and it will take 300 years for NASA’s farflung Voyager 1 probe to even glimpse the cloud’s closest portion.
Astronomers have very limited tools to study this intriguing world, as objects in the Oort Cloud don’t produce their own light. At the same time, these objects are too far away to reflect much of the sun’s light.
So how exactly did the scientists figure out that there must be so many interstellar objects in the Oort Cloud, and what did Borisov have to do with it?
Amir Siraj, a graduate student at Harvard University’s Department of Astronomy and lead author of the study, told Space.com in an email that he could calculate the probability of foreign comets visiting the solar system simply based on the fact that the Borisov comet had been discovered.
“Based on the distance that Borisov was detected at, we estimated the implied local abundance of interstellar comets, just like the abundance of ‘Oumuamua-like objects was calibrated by the detection of ‘Oumuamua,” Siraj said.
The mysterious ‘Oumuamua, first spotted by astronomers in Hawaii in October 2017, was the first interstellar body ever detected within our own solar system. The object passed Earth at a distance of 15 million miles (24 million km), about one-sixth of the distance between our planet and the sun. An intense debate about ‘Oumuamua’s nature ensued, as it wasn’t clear at first whether the object was a comet or an asteroid.
Even the detection of a single object can be used for statistical analysis, Siraj said. The so-called Poisson method, which the astronomers used, calculates the probability of an event happening in a fixed interval of time and space since the last event.
Taking into consideration the gravitational force of the sun, Siraj and co-author Avi Loeb, an astronomer at Harvard, were able to estimate the probability of an interstellar comet making its way to Earth’s vicinity. They found that the number of interstellar comets passing through the solar system increases with the distance from the sun.
“We concluded that, in the outer reaches of the solar system, and even considering the large uncertainties associated with the abundance of Borisov-like objects, transitory interstellar comets should outnumber Oort Cloud objects (comets from our own solar system),” Siraj added.
So why have astronomers seen just one interstellar comet so far? The answer is technology. Telescopes have only recently gotten powerful enough to be able to spot those small but extremely fast-travelling bodies, let alone study them in detail.
“Before the detection of the first interstellar comet, we had no idea how many interstellar objects there were in our solar system,” said Siraj. “Theory on the formation of planetary systems suggests that there should be fewer visitors than permanent residents. Now we’re finding that there could be substantially more visitors.”
The astronomers hope that with the arrival of next-generation telescopes, such as the Vera C. Rubin Observatory, currently under construction in Chile, the study of extrasolar comets and asteroids will truly take off.
The new study was published in the journal Monthly Notices of the Royal Astronomical Society on Monday (Aug 24).
Follow Tereza Pultarova on Twitter @TerezaPultarova. Follow us on Twitter @Spacedotcom and on Facebook.
Scientists may have accidentally detected dark energy – CTV News
Dark energy, a mysterious force believed to be causing the universe to expand at an accelerated rate, may have been detected by scientists for the first time.
In a new study, published Wednesday in the journal Physical Review D, the authors suggest certain unexplained results from an experiment designed to detect dark matter could have been caused by dark energy.
“Despite both components being invisible, we know a lot more about dark matter, since its existence was suggested as early as the 1920s, while dark energy wasn’t discovered until 1998,” Sunny Vagnozzi, of the University of Cambridge’s Kavli Institute for Cosmology, said in a story posted by the university. “Large-scale experiments like XENON1T have been designed to directly detect dark matter, by searching for signs of dark matter ‘hitting’ ordinary matter, but dark energy is even more elusive.”
Nearly everything we can see and interact with, from bacteria to entire galaxies, is considered ordinary matter and energy, and makes up about five per cent of our universe, according to scientists. The rest is made up of dark matter (27 per cent), an invisible attractive force that holds the cosmos together, and dark energy (68 per cent), a repulsive force considered to be responsible for the accelerating expansion of the universe.
The XENON research project is a collaboration of 160 scientists from around the world who have come together to perform a series of experiments aimed at detecting dark matter particles. These experiments involve the use of ultra-pure liquid xenon, a colourless, dense, odourless noble gas found in trace amounts in Earth’s atmosphere.
Experiments are performed at the Gran Sasso National Laboratory, the largest underground laboratory in the world, located approximately 1.4 kilometres beneath the Gran Sasso mountains in central Italy, about 120 kilometres northeast of Rome.
The XENON1T experiment was the latest phase of the project. About a year ago, it detected an unexpected signal, or excess, over the expected background profile.
“These sorts of excesses are often flukes, but once in a while they can also lead to fundamental discoveries,” Luca Visinelli, researcher at Frascati National Laboratories in Italy, said. “We explored a model in which this signal could be attributable to dark energy, rather than the dark matter the experiment was originally devised to detect.”
The researchers created a physical model that used a type of screening mechanism known as chameleon screening to show that dark energy particles produced in the Sun’s strong magnetic fields could explain the XENON1T signal.
“It was really surprising that this excess could in principle have been caused by dark energy rather than dark matter,” Vagnozzi said. “When things click together like that, it’s really special.”
A discovery such as this would mean that experiments designed to detect dark matter, including those performed during the XENON project, could also be used to detect dark energy. But further research is required to confirm these findings.
“We first need to know that this wasn’t simply a fluke,” Visinelli said. “If XENON1T actually saw something, you’d expect to see a similar excess again in future experiments, but this time with a much stronger signal.”
'Happy' SpaceX tourist crew spend first day whizzing around Earth – Phys.org
SpaceX’s all-civilian Inspiration4 crew spent their first day in orbit conducting scientific research and talking to children at a pediatric cancer hospital, after blasting off on their pioneering mission from Cape Canaveral the night before.
St Jude tweeted its patients got to speak with the four American space tourists, “asking the questions we all want to know like ‘are there cows on the Moon?'”
Billionaire Jared Isaacman, who chartered the flight, is trying to raise $200 million for the research facility.
Inspiration4 is the first orbital spaceflight with only private citizens aboard.
Earlier, Elon Musk’s company tweeted that the four were “healthy” and “happy,” had completed their first round of scientific research, and enjoyed a couple of meals.
Musk himself tweeted that he had personally spoken with the crew and “all is well.”
By now, they should have also been able to gaze out from the Dragon ship’s cupola—the largest space window ever built, which has been fitted onto the vessel for the first time in place of its usual docking mechanism.
Most humans in space
The Inspiration4 mission also brings the total number of humans currently in space to 14—a new record. In 2009, there were 13 people on the International Space Station (ISS).
There are currently seven people aboard the ISS, including two Russian cosmonauts, and three Chinese astronauts on spaceship Shenzhou-12, which is bound home after its crew spent 90 days at the Tiangong space station.
Isaacman, physician assistant Hayley Arceneaux, geoscientist Sian Proctor and aerospace data engineer Chris Sembroski are whizzing around the planet at an altitude that at times reaches 590 kilometers (367 miles).
That is deeper in space than the ISS, which orbits at 420 kilometers (260 miles), and the furthest any humans have ventured since a 2009 maintenance mission for the Hubble telescope.
Their ship is moving at about 17,500 mph (28,000 kph) and each day they will experience about 15 sunrises and sunsets.
Their high speed means they are experiencing time slightly slower than people on the surface, because of a phenomenon called “relative velocity time dilation.”
Apart from fundraising for charity, the mission aims to study the biological effects of deep space on the astronauts’ bodies.
“Missions like Inspiration4 help advance spaceflight to enable ultimately anyone to go to orbit & beyond,” added Musk in a tweet.
The space adventure bookends a summer marked by the battle of the billionaires Richard Branson and Jeff Bezos to reach the final frontier.
But these flights only offered a few minutes of weightlessness—rather than the three full days of orbit the Inspiration4 crew will experience, before splashing down off the coast of Florida on Saturday.
© 2021 AFP
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Chinese astronauts return after 90-day mission to space station – Al Jazeera English
Shenzhou-12 mission carrying three Chinese men landed safely in the autonomous region of Inner Mongolia in northern China.
Three Chinese astronauts have returned to earth after a 90-day visit to an unfinished space station in the country’s first crewed mission since 2016.
In a small return capsule, the three men – Nie Haisheng, Liu Boming and Tang Hongbo – landed safely in the autonomous region of Inner Mongolia in the north of China at 1:34pm (05:34 GMT), state media reported.
The Shenzhou-12 mission was the first of four crewed missions planned for 2021-2022 as China assembles its first permanent space station. The process requires 11 missions, including the launches of the station’s three modules.
Construction kicked off in April with the launch of the Tianhe module, the future living quarters of the space station. Slightly larger than a city bus, Tianhe was where Nie, Liu and Tang have stayed since mid-June, marking China’s longest spaceflight mission.
While in orbit, the astronauts conducted spacewalks, validated Tianhe’s life-support system, tested the module’s robotic arm, and sorted supplies for upcoming crewed missions.
The second crewed mission is planned for October, with the next batch of astronauts expected to stay on Tianhe for six months.
Ahead of that Shenzhou-13 mission, China will send an automated cargo spacecraft – Tianzhou-3 – to Tianhe carrying supplies needed by the next crew.
Tianzhou-3 will be launched in the near future, state media said recently.
Blocked by US law from working with NASA and by extension on the US-led International Space Station (ISS), China has spent the past 10 years developing technologies to construct its own space station.
China’s space station, expected to be completed by the end of 2022, will be the sole alternative to the 20-year-old ISS, which may be retired in 2024.
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