This weekend brings us one of 2018's best astronomical events: the Perseid meteor shower. The Perseids are one of the most rewarding showers of the year, frequently delivering bright fireballs exhibiting long, persistent trails. While the shower recurs every year around this time, moonlight can spoil the fun. But for 2018, the moon will be in its new phase during the peak of the shower — leaving our night skies dark for meteor-seeking skywatchers. And ad bonus is that the peak occurs on a warm summer weekend!
Finding the ideal viewing location and knowing where and when to look will increase the number of meteors you see. In this edition of Mobile Astronomy, we'll focus on how to use your mobile app to plan your observing session, offer tips for seeing the most meteors, and point out some special features to look for. [Perseid Meteor Shower 2018: When, Where & How to See It]
Meteor shower basics
Many people use the phrase "shooting star" to describe a meteor, but that's misleading. Meteors are happening right here at home, above Earth's surface, and are independent of the distant background stars. The light we see streaking across the sky is occurring within Earth's atmosphere.
Meteor showers occur when Earth's orbit carries us through zones of debris left in interplanetary space by periodic comets (and, in some cases, asteroids). Over centuries, the pparticles, which weigh about 1 to 2 grams and range in size from sand grains to small pebbles, accumulate and spread out into an elongated "cloud" along the comet's orbit. (A good analogy is the material tossed out of a dump truck as it rattles along. The roadway gets quite dirty if the truck drives the same route many times!) If Earth's orbit intersects the comet's orbit, we experience a meteor shower that repeats annually because Earth returns to the same location in space on the same dates every year.
As we traverse the debris, our planet's gravity attracts the particles, and they burn up as "shooting stars" while falling through Earth's atmosphere. The particles enter the atmosphere at speeds ranging from 25,000 to 160,000 mph (40,000 to 256,000 km/h). And each particle's kinetic energy hionizes the air molecules it encounters, leaving a long trail of glowing gas that is less than a few feet wide, but many miles long. Most trails occur in the thermosphere, the region of the atmosphere about 50 to 75 miles (80 and 120 km) above the ground. Slower meteors need to reach the denser atmosphere at lower altitudes before forming a trail. Viewed from the Earth's surface on a clear, dark night, we see the trails glowing briefly as they streak in front of distant stars.
The colors that meteor watchers see come from a combination of factors. Red light is emitted by the glowing air molecules. The meteor itself is also burning up during its high-speed passage, and oranges, yellows, blues, greens and violets are produced when minerals in the particles — such as sodium, iron and magnesium — are vaporized. Scientists can analyze the color spectrum in a meteor trail and determine the particle's composition. If anything survives to land on the ground, it becomes a meteorite. An easy way to remember the difference is to recall that many rock names end with "-ite," like granite.
The duration of a meteor shower depends on the width of the debris zone — that is, how many days or hours it takes Earth to pass through it. A meteor shower commences on the date when the Earth first enters the debris zone. The shower then builds to a peak when Earth passes through the densest portion of the cloud, and then tapers off, ending on the date when the planet exits the zone.
The number of meteors produced during a shower depends on whether Earth passes through the densest region of the zone, or merely skirts the edges. Since that debris is also orbiting the sun, the density of the particles varies on a time scale that is related to the source comet's orbital period and shaped by the pull of other planets; producing years when more, or less, material is encountered. Planetary scientists create models of the debris distribution to help predict the intensity of showers each year. Apps designed for observing meteor showers take those variations into account.
The brightness of a shower's meteors is dictated by the average size of the grains in the zone. Some showers are known for having fewer, but brighter meteors, while others are dimmer, but much more prolific. Most showers are global events, but certain showers are better for observers in the Northern or Southern Hemisphere due to Earth riding high or low through the cloud. [How to See the Best Meteor Showers of 2018]
During a shower, meteors can appear anywhere in the sky, but they will all be traveling away from a particular locationy, called the radiant, that lies within the constellation that gives the shower its name; in this case, Perseus for the Perseids. The radiant simply marks the direction in the sky that Earth is heading toward while the planet is traversing the debris zone. (This direction-of-travel rule can be broken when two showers are underway at the same time, with two different radiants, and by random meteors, called sporadics, which aren't part of the main debris field, but are isolated particles drifting in interplanetary space.)
Several factors affect how many meteors you will see during a shower. If Earth happens to traverse the densest part of the cloud while it's daytime, you'll be looking for meteors the night before or after the peak, somewhat reducing the numbers.
Because most meteors are dim, a dark sky is essential to see them. Unfortunately, the moon can ruin an otherwise terrific show. The new-moon phase, when the moon is near the sun, will leave the night sky dark. First-quarter moons set in early evening, and last-quarter moons don't rise until the wee hours, so meteor hunters can work around them. Full moons stay up all night and can spoil a shower. Thankfully, phases of the moon vary year from year, so every shower gets good years and bad. (Last year, the moon was just past full on the Perseids' peak night.) Your astronomy app will tell you the phase of the moon at the peak of a meteor shower. Look at all the dates around the peak to find nights when the moon is less of a factor.
How and when to see Perseid meteors
The source of the Perseid meteor shower is a 133-year periodic comet named Comet 109P/Swift-Tuttle. You can use the SkySafari app to see the comet's orbit rendered in 3D. Select the sun and tap the Orbit icon. The app will display a 3D model of the solar system. If the planets' orbits are not plotted, enable them in the Settings / Solar System menu. In the same menu, enable the Selected Object Orbit option. Now use the search menu and type "109P." When that comet's information screen appears, tap the Center icon. You can enlarge and rotate the view to see how the comet passes through the inner solar system and adjust the years to watch how the comet moves over time.
The highest number of Perseid meteors is expected from Sunday night through Monday morning (Aug. 12 to 13), when Earth will be closest to the core of the debris zone. The active period for this shower runs from July 13 through Aug. 26, so keep an eye out for Perseids before and after this peak weekend, too.
This shower is known for producing 60 to 80 meteors per hour, or more, at the peak — many manifesting as bright, sputtering fireballs with long, persistent trails. Watch for trails that linger for a few minutes while dissipating, like jet contrails!
The Perseid shower's radiant lies between the constellations Camelopardalis the giraffe and Perseus the hero, but the meteors can streak across any part of the sky. The radiant is low in the northeastern sky during mid-August evenings, and nearly overhead by dawn. Meteor showers are best observed in the dark skies before dawn because that's when the sky overhead is leading the Earth as it plows directly into the oncoming debris field, like a moving car's windshield getting splattered with bugsd. And when the radiant is overhead, around 4 a.m. local time, the entire sky is available for meteors that are no longer hidden from view by Earth's horizon. When observing a meteor shower, don't focus your attention on the radiant. Meteors from that location will be heading directly toward you and will have very short trails.
For best results, try to find a safe and dark viewing location with as much open sky as possible. Even a 30-minute drive to a park or a rural site away from ncity lights will help a lot. You can start watching as soon as it is dark to catch the very long meteors that are produced by particles skimming the Earth's upper atmosphere. These are rarer, but they feature longer trains.
Bring a blanket for warmth and a chaise lounge (or something similar) to avoid neck strain, plus snacks and drinks. Try to keep watching the sky even when chatting with friends or family — they'll understand. And call out when you see a meteor; a bit of friendly competition is fun! If folks nearby don't mind, use your mobile device to add a musical accompaniment.
Meteor showers are a screen-free activity. But before you put your phone away, use the SkySafari app to find out where the radiant is. Use the list of Meteor Showers in the Search menu or type the name "Perseid" into the search bar. On the shower's information screen, tap the Center icon and then enable the app's Compass mode (in the toolbar). Then hold your device up and pan around until you find the constellation Perseus. The distinctive "W" of Cassiopeia will be above it.
Once you are ready to look for meteors, try to avoid looking at your phone or tablet — the bright screen will spoil your adaptation to the dark. If you must look, minimize the brightness or cover the screen with red film. Disabling app notifications will also reduce the chances of unexpected bright light. And remember that binoculars and telescopes will not help you see meteors because they have fields of view that are too narrow.
Meteor showers are excellent opportunities to take wide-field, long-exposure images of the sky. Mount your camera on a tripod and take a series of exposures a few tens of seconds long. Or use a simple equatorial tracking mount to avoid star trails. See NASA's tips for photographing a meteor shower for more information.
SkySafari 6 and similar sky-charting apps will allow you to search for other meteor showers by name and will display their radiant location on the sky. The app will provide information about the source comet or asteroid; the start, end and peak dates; and some history. You can adjust the app's time to visualize when the radiant will be above the horizon for your location.
If you snap an awesome photo of Perseid meteors that you'd like to share with Space.com and our news partners for a potential story or gallery, send images and comments to email@example.com.
The past four years have been the hottest on record, but new research shows the Earth was actually in a global warming "hiatus" that is about to end. And when it does, natural factors are likely to help an already warming planet get even hotter over the next four years, according to a new forecasting model.
Rising CO2 levels have caused the temperature of the planet to rise, said lead author of the Nature Communications paper, Florian Sevellec, a professor of ocean and Earth science at the University of Southampton in the United Kingdom and a scientist at France's National Centre for Scientific Research.
Records show 2017 marked the 41st consecutive year with global temperatures at least marginally above the 20th century average, with 2016 being the record-holder. And it's likely that global temperatures in 2018 will be another one for the record books.
However, Earth's natural cycles, which include events like El Nino and La Nina, can also influence global temperatures.
And while Earth seems to have been running a fever for almost a decade straight, the natural cycles have been in their "cooling" phase, Sevellec says — and that's about to shift, raising the global temperature further.
"It will be even warmer than the long-term global warming is inducing," Sevellac said.
This cooler phase of the planet's natural variability is responsible for what is often referred to as a global warming "pause" or "hiatus." While the planet continued to warm, it seemed to plateau.
But that had to end sometime.
John Fyfe, senior research scientist at the Canadian Centre for Climate Modelling and Analysis at Environment and Climate Change Canada, says that multiple issues were at play but mainly the natural variability of the planet.
"I'm not at all surprised by the results," Fyfe said of the new study, in which he was not involved. "And the reason for that is that we have gone down this long slowdown period primarily due to internal variability, and the expectation was that we'd come out of it."
With the Earth continuing to warm, the chances increase for events like heat waves. (Yves Herman/Reuters)
Though CO2 levels were still increasing in Earth's atmosphere, natural cycles like the El Nino Southern Oscillation (ENSO) in the Pacific Ocean were cooler than normal and offset rising global temperatures.
But, Sevellac says, "the long-term trend was building up."
This doesn't mean, however, that we can point to a specific area and better forecast, say, heat waves. Instead, this is a global measurement. But with the Earth continuing to warm, the chances increase for these events.
And global warming doesn't mean that every location on the planet warms uniformly — there are some regions that can be colder than normal — nor does it mean that each year is hotter than the previous one. Instead, it's an overall trend that can play out within a decade or more, with the temperature of the entire planet rising over time.
Probability vs. certainty
In order to test the ability to predict future climate outcomes, the model employs a method that looks backward. In this case, it was able to predict with accuracy the climate slowdown that occurred around 1998 and onward to roughly 2014.
But it's important to note that this is a probability, not a certainty.
The model shows a higher temperature than what was predicted based just on the increased CO2: the probability is 58 per cent for global surface air temperature and 75 per cent for sea surface temperatures.
"Because we tested it over the last century, we know that we are accurate for the likelihood," Sevellac says. "But the likelihood doesn't mean it will occur … there exists a small chance of being cold."
There's no telling how long the cycle will last, if it does manifest: it could be five years or 10. But what's important to note, Sevellac says, is that rising CO2 is still the key player in the warming of the planet.
While the study shows that the Earth's natural variability can have an influence in the short term, Sevellac says, "I think it's also a demonstration that global warming will still be there after all this natural variability."
A dream solution is that humans could develop a way to suck as much CO2 from the atmosphere as we release, and combined with greenhouse gas emission reductions, we could slow or reverse the tide of climate change.
Scientists have found a way to rapidly create the mineral magnesite in a lab both inexpensively and potentially at scale. This could be coupled with carbon sequestration, a process in which carbon is injected and stored underground, typically in depleted oil and gas fields. Reducing the concentration of CO2 in the atmosphere can be both a result of reducing input as well as increasing output of carbon dioxide from the atmosphere.
If implemented at scale, the potential for another tool of CO2 removal via magnesite becomes a possibility, removing carbon dioxide from the atmosphere and storing it long-term in the mineral magnesite.
To explain the above equations, carbon dioxide from the atmosphere is injected into water, which is then dissociated to form carbonic acid. From there, elemental magnesium combines with the carbonic acid to form magnesite (MgCO3).
At this time, most carbon capture and storage options are difficult to implement at scale due to high costs and difficulties scaling. With this new method, however, the rate of magnesite formation goes from hundreds to thousands of years in nature to within 72 days in a lab and at low temperatures.
Based on previous studies, magnesite can remove about half its weight in carbon dioxide from the atmosphere. Estimates put our current CO2 emissions at about 40 billion tons per year. That would mean to remove the equivalent amount of carbon emitted per year solely through magnesite formation, 80 billion tons would have to be produced per year. It becomes increasingly apparent that this cannot be the only lever we pull in mitigating climate change.
By speeding up the process, magnesite could be a legitimate resource for removing carbon dioxide from the atmosphere. However, the research is still in an experimental phase and will need to be continually tested before it could ever be implemented at industrial scales. In addition, the process will rely on the current price of carbon and financial incentives to remove carbon from the atmosphere.
New research published by the Royal Tyrrell Museum on Thursday has sunk previous claims that a swimming dinosaur once paddled the rivers of the Earth.
The paper, published in scientific journal PeerJ, uses computer modelling to conclude the Spinosaurus was not adapted to swim as previously thought.
Research published in 2014 by Nizar Ibrahim and others in the journal Science proposed the dinosaur was partly aquatic, meaning it could both swim and walk on land, a first for any dinosaur.
But using different techniques that relied on physics-based testing methods, the Royal Tyrrell Museum’s curator of dinosaurs, Donald Henderson, found that the 95-million-year-old species would not have been able to survive living in water.
Henderson created three-dimensional, digital models of Spinosaurus and other predatory dinosaurs in order to test their centres of mass buoyancy and equilibrium when immersed in water. He also tested the software using models of semi-aquatic animals such as an alligator and emperor penguin, for comparison.
His models showed the Spinosaurus would have been able to float with its head above water and breath freely, just like other dinosaurs analyzed in the study.
But unlike semi-aquatic animals like alligators, which can easily self-right themselves when tipped to the side in water, the Spinosaurus rolled over onto its side when tipped slightly. The finding implied that the dinosaur species would have easily tipped over in water, forcing it to rely on its limbs to constantly maintain an upright position.
Its centre of mass was also found to be close to its hips, between its hind legs, as opposed to the centre of the torso, which had been proposed by Ibrahim’s 2014 research.
Henderson’s model found the Spinosaurus to be unsinkable underwater, something that would have severely limited its ability to hunt aquatic prey. This differentiates it from traits commonly demonstrated by living aquatic birds, reptiles and mammals, which can submerse themselves to pursue prey underwater.
“The combination of mass close to the hips, an inability to sink underwater, and a tendency to roll onto its side unless constantly resisted by limb use, suggest that Spinosaurus was not specialized for a semi-aquatic mode of life,” the researchers stated.
“Spinosaurus may have been specialized for a shoreline or shallow water mode of life, but it would have still have been a competent terrestrial animal,” added Henderson.