The Disc Of The Milky Way Is Bigger Than We Thought

Spiral galaxies such as the Milky Way have discs which are really thin, in which the major fraction of their stars are found. These discs are limited in size, so that beyond certain radius there are very few stars left.

In our Galaxy we were not aware that there are stars in the disc at distances from the centre more than twice that of the Sun. This means that our own star was apparently orbiting at about half the galactic radius. However now we know that there are stars quite a bit further out, at more than three times this distance, and it is probable that some stars are at more than four times the distance of the Sun from the Galactic centre.

“The disc of our Galaxy is huge, around 200 thousand light years in diameter” says Martín López-Corredoira, a researcher at the IAC and the first author of the article recently published in the journal Astronomy & Astrophysics and whose authors come from both the IAC and the NAOC.

In broad terms we can think of galaxies like the Milky Way as being composed of a rotating disc, which includes spiral arms, and a halo, spherical in shape, which surrounds it. This piece of research has compared the abundances of metals (heavy elements) in the stars of the Galactic plane with those of the halo, to find that there is a mixture of disc and halo stars out to the large distances indicated.

The researchers came to these conclusions after make a statistical analysis of survey date from APOGEE and LAMOST, two projects which obtain spectra of stars to extract information about their velocities and their chemical compositions. “Using the metallicities of the stars in the catalogues from the high quality spectral atlases of APOGEE and LAMOST, and with the distances at which the objects are situated, we have shown that there is an appreciable fraction of stars with higher metallicity, characteristic of disc stars, further out than the previously assumed limit on the radius of the Galaxy disc” explains Carlos Allende, a researcher at the IAC and a co-author of this publication.

Francisco Garzón, an IAC researcher who is another of the authors of the article explains that “We have not used models, which sometimes give us only the answers for which they were designed, but we have employed only the statistics of a large number of objects. The results are therefore free from a priori assumptions, apart from a few basic and well established ones.”

System With Three Earth-Sized Planets Discovered

The information about these new exoplanets has been obtained from the data collected by the K2 mission of NASA’s Kepler satellite, which started in November 2013. The work, which will be published in the Monthly Notices of the magazine Royal Astronomical Society (MNRAS), reveals the existence of two new planetary systems detected from the eclipses they produce in the stellar light of their respective stars. In the research team led jointly by Javier de Cos at the University of Oviedo, and Rafael Rebolo at the IAC, participate, along with researchers from these two centres, others from the University of Geneva and the Gran Telescopio Canarias (GTC).

The first exoplanetary system is located in the star K2-239, characterized by these researchers as a red dwarf type M3V from observations made with the Gran Telescopio Canarias (GTC), at the Roque de los Muchachos Observatory (Garafía, La Palma). It is located in the constellation of the Sextant at 50 parsecs from the Sun (at about 160 light years). It has a compact system of at least three rocky planets of similar size to the Earth (1.1, 1.0 and 1.1 Earth radii) that orbit the star every 5.2, 7.8 and 10.1 days, respectively.

The other red dwarf star called K2-240 has two super-Earth-like planets about twice the size of our planet. Although the atmospheric temperature of red dwarf stars, around which these planets revolve, is 3,450 and 3,800 K respectively, almost half the temperature of our Sun. These researchers estimate that all planets discovered will have temperatures superficial tens of degrees higher than those of the planet Earth due to the strong radiation they receive in these close orbits to their stars.

Future observation campaigns with the new James Webb space telescope will characterize the composition of the atmospheres of the discovered planets. Spectroscopic observations with the ESPRESSO instrument, installed in the Very Large Telescope (VLT), of the European Southern Observatory (ESO), or with future spectrographs in the GTC or in new astronomical facilities, such as the ELT or the TMT, will be crucial to determine the masses, densities and physical properties of these planets.

The Gran Telescopio Canarias (GTC), installed at the Roque de los Muchachos Observatory (Garafía, La Palma) is part of the Singular Scientific and Technical Infrastructure network (ICTS) of Spain.

Multiple Alkali Metals In Unique Exoplanet

The extrasolar planet WASP-127b is one of the least dense exoplanets ever found. It has a radius 1.4 times greater than Jupiter, but only 20% of its mass. Such a planet has no analogue in the solar system and is rare even within the exoplanet diversity. It takes just over four days to complete an orbit around its parent star and its surface temperature is around 1400 K (1127 ° C).

The observations of WASP-127b reveal the presence of a large concentration of alkali metals in its atmosphere, allowing simultaneous detections of Sodium, Potassium and Lithium, for the first time in an exoplanet. The Sodium and Potassium absorptions are very broad, which is a characteristic shape in relatively clear atmospheres, and model fits indicate that the skies of WASP-127b are approximately 50% clear.

Guo Chen, a postdoctoral researcher at the IAC and first author of the article, explains “the particular characteristics of this planet allowed us to perform a detailed study of its rich atmospheric composition.” And adds that “The presence of Li is very valuable to understand the evolutionary history of the planetary system and could shed light on the mechanisms of planet formation.” In fact, the planet’s host star, WASP-127, is also Li rich, which could point to an AGB star or supernovae having enriched the cloud of material from which this system originated.

Enric Pallé, a researcher at the IAC and co-author of the study, points out that they also found possible signs of water. “While this detection is not statistically significant, as water features are weak in the visible,” he says, “our data indicates that additional observations in the near-infrared should detect it with high significance.”

The results obtained indicate the great potential of ground-based telescopes for the study of planetary atmospheres. “In particular, the detection of a trace element such as Li in a planetary atmosphere is a major breakthrough and motivates new follow-up observations and detailed theoretical modelling to corroborate the findings,” says Nikku Madhusudhan, from the University of Cambridge.

We are just starting to probe the atmospheres of these planets with ground-based telescopes, but Chen believes that this “will also be a reference exoplanet for future studies with space telescopes such as the James Webb.” These future studies will reveal the detailed nature of WASP-127b as a benchmark for this new class of very low density exoplanets.

Tropical Storm Aletta May Become the First Hurricane of 2018; Second Eastern Pacific Storm Likely to Form This Weekend

Tropical Storm Aletta is expected to become the first hurricane of the 2018 Eastern Pacific hurricane season, and another area off the Mexican coast could become the second named storm next week.

Aletta is just over 400 miles off the Mexican coast and well south of Mexico’s Baja Peninsula.

Infrared satellite imagery indicates that showers and thundershowers are become better located near Aletta’s center of circulation.

Given that, Aletta is expected to strengthen to the season’s first hurricane either Thursday or Friday.

Fortunately, a dome of high pressure aloft over northern Mexico will steer Aletta away from the Mexican coast on a general west-northwest track into early next week.

To the east of Aletta, another area of low pressure, a tropical wave, is given high odds by the NHC to develop into at least a tropical depression this weekend south of the Mexican Riviera.

If it eventually becomes a tropical storm, it would earn the name Bud.

It’s too soon to determine whether this second system will eventually pose a direct threat to parts of the Mexican Pacific coast next week.

For now, interests along the Mexican coast from Acapulco to Zihuatanejo, Manzanillo, Puerto Vallarta and Los Cabos should monitor the progress of this second system into next week.

At least some peripheral impacts are possible near the coast from each system, even if the centers of both systems remain offshore.

Some outer rainbands could push ashore, at times, through next week, possibly triggering local flash flooding if they persist in any area for a few hours at a time.

High surf will be generated, propagating first to the southern Mexican coast, then pushing northward toward the Baja Peninsula, including Los Cabos. Breaking waves and rip currents will be a threat along those beaches into at next week.

The average date when the first named storm forms in the Eastern Pacific Basin is June 10, according to NHC data from 1971 to 2009.

UPDATE : Guatemala: Volcano Search And Rescue Resumes With Nearly 200 People Missing

Emergency crews have cautiously resumed search and rescue operations in towns and villages devastated by the eruption of Guatemala’s Volcano of Fire, but time was quickly running out to find survivors of a disaster that killed more than 75 people with another nearly 200 still missing.

Thousands of people displaced by the eruption have sought refuge in shelters, many of them of with dead or missing loved ones and facing an uncertain future, unable to return to homes destroyed by the volcano.

Firefighters said the chance of finding anyone alive amid the still-steaming terrain was practically non-existent 72 hours after the volcanic explosion on Sunday. The thick gray ash covering the stricken region was hardened by rainfall, making it even more difficult to dig through the mud, rocks and debris that reached to the rooftops of homes.

“Nobody is going to be able to get them out or say how many are buried here,” said Efraín Suárez, standing amid the smoking holes dotting what used to be the village of San Miguel Los Lotes on the flanks of the mountain.

“The bodies are already charred,” the 59-year-old truck driver said. “And if heavy machinery comes in they will be torn apart.”

Once a verdant collection of canyons, hillsides and farms, the area was reduced to a moonscape of ash by the avalanche of fast-moving molten rock, mud and debris.

Rescuers poked metal rods into the ground, sending clouds of smoke pouring into the air in a sign of the super-hot temperatures still remaining below the surface, which firefighters said reached as high as 750 to 1,300F (400 to 700C) in some places.

At a shelter in the Murray D Lincoln school in the city of Escuintla, about 10 miles (15km) from the volcano’s peak, Alfonso Castillo said he and his extended family of 30 had lived on a shared plot in Los Lotes where each family had its own home.

Everyone was accustomed to the volcano, one of Central America’s most active, rumbling and spewing smoke, the 33-year-old farm worker said, so at first nothing seemed abnormal on Sunday. But then a huge cloud of ash came pouring out.

“In a matter of three or four minutes the village disappeared,” Castillo said, smothered in what he described as a “sea” of muck that came crashing into homes, inundating people, pets and wildlife.

The family holed up in a house that heated up “like a boiler” inside before making their way on to the roof and then to the upper story of another concrete home. After a cellphone call to Castillo’s brother, rescuers arrived and brought the family to safety. But the life they knew was gone.

“Nobody wants to go back there. My children say they would rather be in the streets … There are many people who are helping us, but we have absolutely nothing. We could not get anything out,” Castillo said. “For us, there is no tomorrow.”

A day after a new evacuation was ordered due to increasing activity by the volcano, a red alert remained in place for the departments of Escuintla, Sacatepéquez and Chimaltenango, and people were advised not to linger near the affected zones.

Authorities warned that the rain had also increased the chance of deadly flows of ash, mud and debris.

The recovery effort was slow, with only nine bodies recovered on Wednesday, according to media reports. An Associated Press journalist witnessed five stretchers carrying bags containing human remains being carried out of Los Lotes.

A man whose rescue in the town of El Rodeo was shown on video as he was pulled out caked in mud with third-degree burns over 50% of his body died at a hospital on Wednesday, according to the country’s social security institute.

The official death toll, which stood at more than 75, was sure to rise, with at least 192 people reported missing. Another 3,319 were in shelters, their homes and livelihoods destroyed.

Lava Flow Evaporates Hawaii’s Largest Freshwater Lake Within Hours

Steam billowed up from Hawaii’s largest freshwater lake as lava flow evaporated its placid waters within a few hours and made it the latest casualty from the Big Island’s Kilauea volcano.

A steam plume first appeared around 10 a.m. Saturday as lava poured into Green Lake in Kapoho, but by 3 p.m. a Hawaii County Fire Department overflight confirmed to the US Geological Survey that the lake had filled with lava and the body of water was no more.

A Hawaii County Fire Department photo shows how lava flows evaporated the waters of Green Lake.

Green Lake — a popular swimming spot — once reached about 200 feet deep, according to CNN affiliate KHNL/KGMB.

“I couldn’t believe it,” Hawaii Community College geography instructor Drew Kapp told the TV station. “I’ve never even heard of anything like that happening before.”

It’s been more than a month since lava began its slow, destructive path after Kilauea erupted. About 7.7 square miles of land have been covered by lava.

Residents also have had to contend with poisonous gases given off by the lava, which can include laze — hydrochloric acid and volcanic glass particles.

Green Lake isn’t the only part of the Big Island that the recent volcanic activity has transformed. Kapoho Bay, famous for its tide pools, was completely filled by lava Tuesday.

Typhoon Signal No 3 Issued As Tropical Storm Ewiniar Brings Floods To Hong Kong

The Hong Kong Observatory issued the typhoon signal No 3 at 12.40pm on Thursday – the first strong wind warning since last October – as tropical storm Ewiniar strengthened.

With mean wind speeds of 41km/h to 62km/h expected, the forecaster advised the public to stay away from the shoreline, not do any water sports and to avoid staying in areas exposed to high winds.

Drivers using motorways and flyovers should be alert to violent gusts, the weather authority added.

At 7pm, Ewiniar was about 270km west-southwest of the city. It was expected to move north or northeast at about 10km/h, edging closer to the western coast of Guangdong province on Thursday.

The Observatory said Ewiniar would make its third landfall in the coastal areas near Yangjiang over the western part of Guangdong on Thursday. The signal No 3 was expected to remain in force on Thursday night.

The authority would take into account the variation of local wind strengths in considering whether to change the warning signal on Friday.

It said the storm’s associated rainbands would bring squalls and heavy showers to the Pearl River estuary.

The maximum sustained wind speed near its centre could be as high as 75km/h.

The chance of the typhoon signal No 8 being issued on Thursday was relatively low, the Observatory added.

The Education Bureau announced that classes at kindergartens, schools for children with physical disabilities and schools for children with intellectual disabilities had been suspended.

“These schools, however, should keep their premises open and implement contingency measures to look after arriving students. They should ensure that conditions are safe before allowing students to return home,” a bureau spokesman said.

Flooding was reported in many areas of the city in the morning as heavy rain continued to fall.

In Tai Po, a junction near Kam Shan Road was submerged in brownish water. Tai Po residents uploaded photos of the mud-filled area to a Facebook group at about 7am, showing a vehicle trying to pass through, as it was the only road leading to Kam Shan.

Exit A2 at Diamond Hill MTR station was closed due to flooding at a nearby construction site. Flooding was also reported at Man Kam To interchange bus station.

Police received reports of falling trees. An incident in Tai Wai involved a tree smashing the windscreen of a vehicle. There were no reports of any injuries.

Due to big waves, red flags had been hoisted at several beaches in the city, the Leisure and Cultural Services Department announced. These included Stanley Main Beach, Turtle Cove Beach, Shek O Beach and Big Wave Bay Beach in Southern district, and Hap Mun Bay Beach, Clear Water Bay First Beach and Clear Water Bay Second Beach in Sai Kung district.

“Beachgoers are advised not to swim at these beaches,” a spokesman for the department said.

The Observatory issued a special announcement on flooding in the northern New Territories at 6.50am, after more than 100mm of rainfall was recorded in the area in the hours before.

“Residents in the northern New Territories, who are likely to be affected, are advised to take necessary precautions to avoid possible flood damage,” the weather authority said, warning that heavy rain could bring flash floods.

More than 70mm of rainfall was recorded in Sha Tin between 5.35am and 6.35am, and was cited as a flood risk.