Small, Hardy Planets Most Likely To Survive Death Of Their Stars

Small, hardy planets packed with dense elements have the best chance of avoiding being crushed and swallowed up when their host star dies, new research from the University of Warwick has found.

Astrophysicists from the Astronomy and Astrophysics Group have modelled the chances of different planets being destroyed by tidal forces when their host stars become white dwarfs and have determined the most significant factors that decide whether they avoid destruction.

Their ‘survival guide’ for exoplanets could help guide astronomers locate potential exoplanets around white dwarf stars, as a new generation of even more powerful telescopes is being developed to search for them. Their research is published in the Monthly Notices of the Royal Astronomical Society.

Most stars like our own Sun will run out of fuel eventually and shrink and become white dwarfs. Some orbiting bodies that aren’t destroyed in the maelstrom caused when the star blasts away its outer layers will then be subjected to shifts in tidal forces as the star collapses and becomes super-dense. The gravitational forces exerted on any orbiting planets would be intense and would potentially drag them into new orbits, even pushing some further out in their solar systems.

By modelling the effects of a white dwarf’s change in gravity on orbiting rocky bodies, the researchers have determined the most likely factors that will cause a planet to move within the star’s ‘destruction radius’; the distance from the star where an object held together only by its own gravity will disintegrate due to tidal forces. Within the destruction radius a disc of debris from destroyed planets will form.

Although a planet’s survival is dependent on many factors, the models reveal that the more massive the planet, the more likely that it will be destroyed through tidal interactions.

But destruction is not certain based on mass alone: low viscosity exo-Earths are easily swallowed even if they reside at separations within five times the distance between the centre of the white dwarf and its destruction radius. Saturn’s moon Enceladus — often described as a ‘dirty snowball’ — is a good example of a homogeneous very low viscosity planet.

High viscosity exo-Earths are easily swallowed only if they reside at distances within twice the separation between the centre of the white dwarf and its destruction radius. These planets would be composed entirely of a dense core of heavier elements, with a similar composition to the ‘heavy metal’ planet discovered by another team of University of Warwick astronomers recently. That planet has avoided engulfment because it is as small as an asteroid.

Dr Dimitri Veras, from the University of Warwick’s Department of Physics, said: “The paper is one of the first-ever dedicated studies investigating tidal effects between white dwarfs and planets. This type of modelling will have increasing relevance in upcoming years, when additional rocky bodies are likely to be discovered close to white dwarfs.”

“Our study, while sophisticated in several respects, only treats homogenous rocky planets that are consistent in their structure throughout. A multi-layer planet, like Earth, would be significantly more complicated to calculate but we are investigating the feasibility of doing so too.”

Distance from the star, like the planet’s mass, has a robust correlation with survival or engulfment. There will always be a safe distance from the star and this safe distance depends on many parameters. In general, a rocky homogenous planet which resides at a location from the white dwarf which is beyond about one-third of the distance between Mercury and the Sun is guaranteed to avoid being swallowed from tidal forces.

Dr Veras said: “Our study prompts astronomers to look for rocky planets close to — but just outside of — the destruction radius of the white dwarf. So far observations have focussed on this inner region, but our study demonstrates that rocky planets can survive tidal interactions with the white dwarf in a way which pushes the planets slightly outward.

“Astronomers should also look for geometric signatures in known debris discs. These signatures could be the result of gravitational perturbations from a planet which resides just outside of the destruction radius. In these cases, the discs would have been formed earlier by the crushing of asteroids which periodically approach and enter the destruction radius of the white dwarf.”

The research received support from the UK’s Science and Technology Facilities Council.

Off The Coast of Portugal, The Earth’s Crust Might Be Peeling In Two

In 1969, a giant earthquake off the coast of Portugal kicked up a tsunami that killed over a dozen people. Some 200 years prior, an even larger earthquake hit the same area, killing around 100,000 people and destroying the city of Lisbon.

Two earthquakes in the same spot over a couple hundred years is not cause for alarm. But what puzzled seismologists about these tremors was that they began in relatively flat beds of the ocean — away from any faults or cracks in the Earth’s crust where tectonic plates slip past each other, releasing energy and causing earthquakes.

So what’s causing the rumbles under a seemingly quiet area? [In Photos: Ocean Hidden Beneath Earth’s Crust]

One idea is that a tectonic plate is peeling into two layers — the top peeling off the bottom layer — a phenomenon that has never been observed before, a group of scientists reported in April at the European Geosciences Union General Assembly held in Vienna. This peeling may be creating a new subduction zone, or an area in which one tectonic plate is rammed beneath another, according to their abstract.

The peeling is likely driven by a water-absorbing layer in the middle of the tectonic plate, according to National Geographic. This layer might have undergone a geological process called serpentinization, in which water that seeps in through cracks causes a layer to transform into soft green minerals. Now, this transformed layer might be causing enough weakness in the plate for the bottom layer to peel away from the top layer. That peeling could lead to deep fractures that trigger a tiny subduction zone, National Geographic reported.

This group isn’t the first to propose this idea, but it’s the first to provide some data on it. They tested their hypothesis with two-dimensional models, and their preliminary results showed that this type of activity is indeed possible — but is still yet to be proven.

This research has not yet been published in a peer-reviewed journal.

Tsunami Alert Issued, 7.5 Quake Hits New Guinea

A powerful earthquake struck Papua New Guinea late Tuesday evening, triggering a tsunami alert for coastal areas up to 1,000 kilometers (620 miles) away.

The U.S. Geological Survey said the quake measured magnitude 7.5 and was located 45 kilometers (28 miles) northeast of Kokopo, a remote town with a population of about 26,000. It was centered at a relatively shallow depth of 10 kilometers (6 miles), it said.

Shallow earthquakes tend to cause more damage on the Earth’s surface, but the USGS estimated that damage and injuries would be low because of the area’s sparse population.

The U.S. Pacific Tsunami Warning Center said tsunami waves of up to 1 meter (3.3 feet) were possible along coastal areas up to 1,000 kilometers (620 miles) from the epicenter, including Papua New Guinea and the nearly Solomon Islands. It later said the tsunami threat had largely passed and no waves had been observed, but that there were no sea level gauges in the area for measurement.

It said there was no tsunami threat to Hawaii or Guam.

Papua New Guinea is located on the eastern half of the island of New Guinea, to the east of Indonesia.

It sits on the Pacific’s “Ring of Fire,” the arc of seismic faults around the Pacific Ocean where much of the world’s earthquakes and volcanic activity occurs.

A magnitude 7.5 earthquake in February 2018 in the nation’s central region killed at least 125 people and forced another 35,000 from their homes. That quake hit areas that are remote and undeveloped, and assessments about the scale of the damage and injuries were slow to filter out.

Australian Scientists Help With Key Volcano Study Using Hawaii’s Kilauea Disaster

Australian scientists have helped shed new light on volcanic eruptions, using Hawaii’s months-long Kilauea disaster which destroyed hundreds of homes. After analysing the eruption on Hawaii’s Big Island beginning in May 2018, researchers from France, the UK, US and Tasmania say changes in the speed of vibrations travelling through a volcano could be used to pinpoint its imminent eruption.

Ten days before the eruption of Kilauea, the University of Tasmania’s Gerrit Olivier says he and his colleagues found these vibrations inside the volcano’s magma chamber changed dramatically.

“The volcano is constantly bulging and contracting as the pressure inside the magma chamber changes,” Dr Oliver said.

“The behaviour of the seismic wave speeds are initially quite predictable.

“When the volcano bulges, the speed at which the vibrations travel through the volcano increase slightly as material is compressed. On the other hand, when the volcano contracts these wave speeds decrease.”

Days before the May 3 eruption, Kilauea was still bulging because of a build-up of pressure, but the vibrations stopped speeding up and instead slowed right down.

“This is a good indicator that the volcano isn’t able to sustain the pressure inside the magma chamber anymore, that the bulge is too big and it starts breaking the material around the magma chamber which ultimately leads to the eruption,” Dr Oliver said.

These changes have been recorded before, but the study said it was the first time it showed them occurring because of a weakening of material inside the volcano just before an eruption.

Dr Oliver and his colleagues hope this method could be used to help predict when other volcanoes will erupt, after Kilauea spewed out 800 million cubic metres of lava destroying more than 700 homes.

With Hurricane Season Approaching, Researchers Work To Better Predict Storm Intensity

Many residents in the southeast U.S. and along the Gulf Coast are already thinking about the 2019 Atlantic hurricane season, which begins on June 1. Last year brought two of the most destructive storms to ever hit the U.S.: Hurricane Florence and Hurricane Michael.

There have been dramatic improvements in hurricane forecasting over the past 20 years. The greatest progress has been made in forecasting a hurricane’s track, including where and when it will make landfall. But the harder challenge is predicting a storm’s intensity, especially for hurricanes like Michael that continue to strengthen as they approach the coast.

As the next hurricane season approaches, researchers are working on new tools to help forecast the intensity of forthcoming storms, enabling residents and emergency managers to be more prepared.

For Hurricane Michael, the National Hurricane Center began issuing advisories five days before it struck Florida’s panhandle, when it was just a disturbance moving toward the Gulf of Mexico. Two days later it was a hurricane, one that continued to strengthen.

No forecasts anticipated how powerful the storm would be at landfall, slamming into Mexico Beach, Fla., as a Category 5 hurricane. It’s one of only four storms that powerful ever to hit the U.S. mainland. “The intensity forecasts were too low,” says Eric Blake, a meteorologist with the National Hurricane Center in Miami. “They’re better than they would have been 20 years ago but still too low.”

Three days before Michael made landfall, it was just a tropical storm. Forecasters warned residents along Florida’s Gulf Coast to prepare for a possible Category 2 hurricane with 100 mile-per-hour winds. A day later, as Michael strengthened, the forecasts upgraded it to Category 3. But as Michael neared Florida’s panhandle, it kept getting stronger, taking even seasoned meteorologists by surprise when it came ashore as a Category 5, with 160 mile-per-hour winds and a 14-foot storm surge.

Blake says a more accurate forecast of Michael’s intensity would have helped emergency managers and residents make decisions about evacuating. “It would have gotten the message out earlier,” he says. “If we were saying right off the bat, ‘Here it is. We’re expecting … Category 4, Category 5,’ that’ll catch people’s attention.”

Researchers with the National Oceanic and Atmospheric Administration are working on the problem with improved hurricane models. One is the Hurricane Weather Research and Forecasting model. It uses data gathered from satellites and aircraft to better understand what’s going on inside a hurricane. It has been in operation for only about a decade but has improved every year.

Meteorologist Jason Sippel says that like other models, HWRF underestimated Hurricane Michael. But it got some key things right.

“From the very first forecast HWRF issued, it showed a rapidly intensifying major hurricane making landfall on the U.S. Gulf Coast,” he says. “So, you have to kind of keep things in perspective. Yes, the errors were large. But all those forecasts did show a major hurricane making landfall and were getting the warning out.”

Frank Marks, the director of NOAA’s Hurricane Research Division, has overseen HWRF’s development. Other countries have global weather forecast models that sometimes outperform the main U.S. model, known as GFS. But no other countries have a regional hurricane model like HWRF, which still needs to be improved.

But, Marks says, HWRF is already helping save lives. “The day before the storm hit, there were 250 people still on Mexico Beach. But by the next morning, the morning before when the storm made landfall, there were only 25. So the messaging got through.”

While researchers are making progress, efforts to improve NOAA’s hurricane models have had setbacks. Some involve science, but some are political. As they prepared for the upcoming hurricane season, researchers had to suspend work earlier this year for six weeks because of the partial government shutdown. Some are worried now about another possible government shutdown in October at the height of hurricane season.

March-Like Storm To Blast California With Drenching Rain, Mountain Snow And Severe Weather

After sunshine and pleasant weather grace California early this week, a powerful storm system will barrel into the state during the middle to latter part of the week.

The return of a March-like weather pattern, driven by a large dip in the jet stream, will be the culprit for driving this rare storm into the West Coast.

Rain will first move into Northern California on Wednesday before overspreading the rest of the state by Wednesday night and Thursday.

By the time the storm moves into the Four Corners region later on Friday, the foothills of the Sierra Nevada and parts of Northern and coastal California will receive between 1 to 3 inches of rain.

The hardest-hit locations may receive as much as 4 or 5 inches of rain.

Between 1 and 2 inches of rain is expected in San Francisco, with 0.50 to 1 inch of rain possible in Los Angeles. San Diego may even receive up to 0.50 of an inch of rain from this system.

Even parts of the San Joaquin Valley will have to deal with showers and thunderstorms from Wednesday night into Thursday that could produce localized heavy downpours and some incidents of small hail.

It is extremely unusual for a storm system to bring this amount of rainfall across the state this late in the spring season.

Average rainfall during the month of May ranges from just under 0.75 of an inch in Sacramento to just under 0.50 of an inch in San Francisco and Fresno. San Diego typically receives around 0.10 of an inch for the month.

These cities, as well as many other locations across the state, will receive two to three times their normal monthly rainfall in the span of only two or three days later this week.

Travel will turn slippery with numerous delays on the roadways after the recent stretch of generally dry weather. Motorists traveling on Interstates 5 and 80, as well as secondary roadways, should allow extra time to reach their destination and reduce speed to lessen the risk of hydroplaning.

Lengthy flight delays and cancellations both into and out of the major hubs along the West coast will also be likely, and some flights may have to be rerouted as gusty winds accompany the rain.

In addition, flash flooding of streets and poor drainage areas, as well as smaller streams and creeks, will be a danger to anybody living in flood-prone areas.

Abnormally chilly air will accompany the clouds and rain later this week, with high temperatures struggling to reach the lower to middle 60s F across the Central Valley on Thursday. Normal highs during the middle of May are in the 80s.

Showers may even reach Death Valley on Thursday and keep high temperatures only in the upper 70s after they soar above the century mark early this week.

Accumulating snow is likely at and above 6,000 feet in the Sierra Nevada by Thursday and Thursday night, and up to a foot of snow is possible at the highest elevations.

Snow may fall as low as 5,000 feet for a time, but is likely struggle to accumulate on paved surfaces at that elevation.

Motorists traveling across I-80’s Donner Pass may even have to deal with snow on the roadway for a brief time if snowfall rates become high enough.

Geomagnetic Storm Headed For Earth Could Mean Auroras Will Be Visible Over Parts Of U.S.

A geomagnetic storm warning has been issued following three coronal mass ejections (CME) from a giant sunspot. The National Oceanic and Atmospheric Administration’s Space Weather Prediction Center said that a minor geomagnetic storm watch is in effect for May 15 and May 16.

As a result of the storm, northern parts of the U.S. may be able to see auroras over the next few nights. A forecast map showing where the auroras may be visible can be seen below.

CMEs come from our sun’s outer atmosphere. This is a region that has extremely strong magnetic fields. When these fields close, they can suddenly eject matter in a huge explosion—a CME. This matter—sometimes a billion tons of it—is ejected into space, impacting any object it comes across.

When a CME explodes in the direction of Earth, the solar material interacts with atoms and molecules in our atmosphere. The collisions produce auroras.

The three CMEs responsible for the latest geomagnetic storm came from the sunspot group Region 2741. The series started on May 10 and material from the first two is expected to arrive on May 15. The third will likely reach Earth on May 16.

“The source location for the CMEs has been associated with disappearing solar filaments (DSF) along areas of the magnetic neutral line in the vicinity of the unipolar sunspot group, Region 2741,” an NOAA statement said.

A solar filament is a long line of colder material that hovers above the sun’s corona. NASA notes that these filaments can float along like this for days before they disappear. “Sometimes they also erupt out into space, releasing solar material in a shower that either rains back down or escapes out into space, becoming a moving cloud known as a coronal mass ejection, or CME,” the space agency noted.

Sunspots are temporary regions on the surface of the sun that are darker and colder than the surrounding area—around 4,500 degrees Celsius cooler.

According to SpaceWeather, the sunspot that the latest three CMEs came from appears to be disintegrating and is no longer able to produce huge CMEs that pose a greater risk to Earth. When the sun does produce large explosions, a strong geomagnetic storm has the potential to cause disruption to GPS systems, satellites and power grids.

At the moment, the sun is in a period of quiet known as the solar minimum. The sun’s activity increases and decreases on an 11-year cycle. The solar maximum, when activity peaks, sees an increase in the number of sunspots. The next solar maximum is expected to peak around 2024.