One of the best shows in the night sky is coming up next week. The Perseid meteor shower peaks on Wednesday night, and this year it is not to be missed!
Right now, as Earth travels along its orbit around the Sun, the planet is passing through a stream of debris left behind by a comet known as 109P/Swift-Tuttle. This comet only passes through the inner solar system once every 133 years or so. However, each year we are treated to a reminder that it’s out there, as Earth sweeps up the bits of icy debris it leaves behind on each pass. When these tiny bits of ice and rock plunge into the atmosphere, they produce the streaks of light we call the Perseid meteor shower.
In this 30-second exposure taken with a circular fish-eye lens, a meteor streaks across the sky during the annual Perseid meteor shower on Friday, Aug. 12, 2016, in Spruce Knob, West Virginia. Photo Credit: (NASA/Bill Ingalls)
According to the International Meteor Organization (IMO), under ideal conditions, observers typically see anywhere from 50-75 meteors per hour during the Perseids peak, which occurs around the 12th of August every year. Sometimes, this shower can deliver as many as 100 meteors per hour or more.
The Perseids radiant — where the meteors appear to originate from — is located in the northern sky, near the constellation Perseus. It never sets below the horizon at this time of year. So, rather than having to wait for the radiant to rise during the night, we can start watching for Perseids as soon as the Sun has completely set.
The location of the Perseids radiant at around midnight on August 11-12. Credit: Stellarium/Scott Sutherland
Even now, a week before the meteor shower peak, viewers can see perhaps 10-20 Perseids per hour throughout the night. The peak on August 11-12 is the absolute best night to watch. If skies are cloudy that night or the timing isn’t good, NASA says that the most likely time to see meteors, otherwise, is a couple of days on either side of the peak.
Whatever night you get out to watch, the best time to see the Perseids during the night is usually in the hours between midnight and dawn. That is when the sky tends to be the darkest. Also, the meteor shower radiant is high in the sky at that time, which means that we are looking more or less straight into the path of the meteoroid stream.
This graph shows the average Perseid meteor activity from 2014-2020. Credits: Graph and background image courtesy NASA
This year, viewing will likely be better than we’ve seen for the past few years, due to the Moon. With the shower peaking only a few days after the New Moon, there will only be a thin crescent Moon in the sky that night, which will set just a few hours after nightfall. This will leave behind a nice dark night sky, which will make it easier for us to see the show!
Read on for tips on how to get the most out of watching a meteor shower.
WHAT’S GOING ON HERE?
Meteor showers happen when Earth encounters a stream of ice, dust, and rock left behind from a comet (or sometimes a special kind of asteroid). As Earth sweeps through the stream, the bits of debris plunge into the planet’s atmosphere, travelling anywhere from 54,000 to 255,000 kilometres per hour. At that speed, these meteoroids compress the air molecules in their path, squeezing them together until they glow white-hot.
The bigger the piece of debris, the brighter and longer-lasting the meteor will be.
Watch below: Dozens of Perseid fireballs captured by NASA in 2020
The Perseids occur every year between July 17 and August 26, as Earth passes through the stream of debris from Comet Swift-Tuttle. 109P/Swift-Tuttle was last seen in the inner solar system in 1992. Right now, it’s far out in the solar system, near the orbit of Neptune, and still headed even farther out. It will return in late 2125.
METEOR? METEOROID? METEORITE?
The bright streaks seen from these showers are called meteors.
A meteoroid is a piece of dust, rock or ice floating through space, left over from the formation of our solar system. The smallest – only a few millimetres wide – tend to be called __micrometeoroids. Anything larger than a metre in diameter is usually called an asteroid.
A primer on meteoroids, meteors and meteorites. Credits: Scott Sutherland/NASA JPL (Asteroids Ida & Dactyl)/NASA Earth Observatory (Blue Marble)
The more massive an object is as it enters Earth’s atmosphere, the brighter the resulting meteor will be. The brightest are called fireballs, while a fireball that ends with an explosion is known as a bolide.
Some fireballs and bolides result in bits of the meteoroid reaching to the ground. When these are found, they are called meteorites.
The Perseids are one of the strongest meteor showers of the entire year, and this alone makes it worth watching. However, there are two other ways this meteor shower distinguishes itself.
First, it has the most fireball meteors of any annual shower.
In the Royal Astronomical Society of Canada’s Observer’s Handbook 2021, Philip McClausland writes “Fireballs are exceptionally bright meteors that are spectacular enough to light up a wide area and attract public attention.”
Watch below: An all-sky camera captures a brilliant Perseid fireball
The second is the ability of some Perseid meteors to leave behind a phenomenon known as a persistent train.
Meteors typically flash for a second and are gone. Fireballs can last up to 10 seconds. Every once in a while, though, a meteor will leave behind a trail of glowing ‘smoke’. These can remain visible for up to several minutes or possibly for more than an hour.
Spotting persistent trains is pretty common, depending on the meteor shower. They have only rarely been recorded, though. Studies of them go back decades, but there is little hard evidence to study the phenomenon. Still, scientists have narrowed their cause to one of two likely reasons: ionization or chemiluminescence.
Ionization means that an atom or molecule gains or loses electrons and thus takes on a negative or positive charge. In the case of a persistent train, a fast-moving meteoroid strips away electrons from air molecules along their path. When these ionized molecules pick up a stray electron to balance out their charge, they release a small burst of light.
Chemiluminescence is the production of light through a chemical reaction. When metals like iron and nickel vaporize off the surface of a meteoroid, they can chemically react with ozone and oxygen to produce a glow. Since these processes take much longer than the original meteor flash, the train can persist for some time after the flash goes out.
Watch below to see a persistent train produced by a December Geminids meteor
One of these explanations may account for these glowing trains, or both may cover different occurrences, at different times, and even between individual meteors. It will apparently take more sightings and recordings of this phenomenon to explain them fully.
TIPS FOR WATCHING A METEOR SHOWER
Here is an essential guide on how to get the most out of meteor shower events.
First off, there’s no need to have a telescope or binoculars to watch a meteor shower. Those are great if you want to check out other objects in the sky at the same time — such as Jupiter and Saturn, which are up all night these days. When watching a meteor shower, though, telescopes and binoculars actually make it harder to see the event because they restrict your field of view.
Here’s the three things needed for watching meteor showers:
Dark skies, and
Even a few hours of cloudy skies can ruin an attempt to see a meteor shower. Since the weather is continually changing, be sure to check for updates on The Weather Network on TV, on our website, or from our app.
Living in cities makes it very difficult to see meteor showers. Those living in suburban areas, with dark back yards shielded from street lights by trees and surrounding houses, may see the brightest meteors. Rural areas offer the best viewing, though, as they are far away from city light pollution.
For most Canadians, simply driving out into the surrounding rural areas is usually good enough to get under dark skies. However, if you live anywhere from Windsor to Quebec City, that will be more difficult. Unfortunately, getting far enough outside of one city to escape its light pollution tends to put you under the light pollution dome of the next city over.
Watch below: What light pollution is doing to city views of the Milky Way
In these areas, there are a few dark sky preserves. A skywatcher’s best bet for dark skies is usually to drive north and seek out the various Ontario provincial parks or Quebec provincial parks. Even if you’re confined to the parking lot, after hours, these are usually excellent locations to watch (and you don’t run the risk of trespassing on someone’s property).
Once you have verified you have clear skies, and you have limited your exposure to light pollution, this is where having patience comes in.
For best viewing, give your eyes time to adapt to the dark. Typically, this takes about 30 minutes of avoiding any sources of bright light (includes cellphone screens). Just looking up into the sky during this time works fine, and you may even catch some of the brighter meteors in the process.
Lastly, the graphics presented for meteor showers often give a ‘radiant’ point on the field of stars, showing from where the meteors appear to originate. Meteors can flash through the sky anywhere above your head, though. So, don’t focus on any particular point in the sky. Instead, just look straight up and take in as much of the sky as you can, all at once. Also, since our peripheral vision tends to be better at night, you may be surprised at how many meteors you can catch from the corner of your eye!
Dark Energy Could Be Responsible for Mysterious Experiment Signals, Researchers Say – Gizmodo
A team of physicists at the University of Cambridge suspects that dark energy may have muddled results from the XENON1T experiment, a series of underground vats of xenon that are being used to search for dark matter.
Dark matter and dark energy are two of the most discussed quandaries of contemporary physics. The two darks are placeholder names for mysterious somethings that seem to be affecting the behavior of the universe and the stuff in it. Dark matter refers to the seemingly invisible mass that only makes itself known through its gravitational effects. Dark energy refers to the as-yet unexplained reason for the universe’s accelerating expansion. Dark matter is thought to make up about 27% of the universe, while dark energy is 68%, according to NASA.
Physicists have some ideas to explain dark matter: axions, WIMPs, SIMPs, and primordial black holes, to name a few. But dark energy is a lot more enigmatic, and now a group of researchers working on XENON1T data says an unexpected excess of activity could be due to that unknown force, rather than any dark matter candidate. The team’s research was published this week in Physical Review D.
The XENON1T experiment, buried below Italy’s Apennine Mountains, is set up to be as far away from any noise as possible. It consists of vats of liquid xenon that will light up if interacted with by a passing particle. As previously reported by Gizmodo, in June 2020 the XENON1T team reported that the project was seeing more interactions than it ought to be under the Standard Model of physics, meaning that it could be detecting theorized subatomic particles like axions—or something could be screwy with the experiment.
“These sorts of excesses are often flukes, but once in a while they can also lead to fundamental discoveries,” said Luca Visinelli, a researcher at Frascati National Laboratories in Italy and a co-author of the study, in a University of Cambridge release. “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.”
“We first need to know that this wasn’t simply a fluke,” Visinelli added. “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.”
Despite constituting so much of the universe, dark energy has not yet been identified. Many models suggest that there may be some fifth force besides the known four known fundamental forces in the universe, one that is hidden until you get to some of the largest-scale phenomena, like the universe’s ever-faster expansion.
Axions shooting out of the Sun seemed a possible explanation for the excess signal, but there were holes in that idea, as it would require a re-think of what we know about stars. “Even our Sun would not agree with the best theoretical models and experiments as well as it does now,” one researcher told Gizmodo last year.
Part of the problem with looking for dark energy are “chameleon particles” (also known as solar axions or solar chameleons), so-called for their theorized ability to vary in mass based on the amount of matter around them. That would make the particles’ mass larger when passing through a dense object like Earth and would make their force on surrounding masses smaller, as New Atlas explained in 2019. The recent research team built a model that uses chameleon screening to probe how dark energy behaves on scales well beyond that of the dense local universe.
“Our chameleon screening shuts down the production of dark energy particles in very dense objects, avoiding the problems faced by solar axions,” said lead author Sunny Vagnozzi, a cosmologist at Cambridge’s Kavli Institute for Cosmology, in a university release. “It also allows us to decouple what happens in the local very dense Universe from what happens on the largest scales, where the density is extremely low.”
The model allowed the team to understand how XENON1T would behave if the dark energy were produced in a magnetically strong region of the Sun. Their calculations indicated that dark energy could be detected with XENON1T.
Since the excess was first discovered, the XENON1T team “tried in any way to destroy it,” as one researcher told The New York Times. The signal’s obstinacy is as perplexing as it is thrilling.
“The authors propose an exciting and interesting possibility to expand the scope of the dark matter detection experiments towards the direct detection of dark energy,” Zara Bagdasarian, a physicist at UC Berkeley who was unaffiliated with the recent paper, told Gizmodo in an email. “The case study of XENON1T excess is definitely not conclusive, and we have to wait for more data from more experiments to test the validity of the solar chameleons idea.”
The next generation of XENON1T, called XENONnT, is slated to have its first experimental runs later this year. Upgrades to the experiment will hopefully seal out any noise and help physicists home in on what exactly is messing with the subterranean detector.
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
‘Happy’ SpaceX tourist crew spend first day whizzing around Earth (2021, September 17)
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