ESO VLT Atacama: Largest yellow hypergiant star observed

HR 5171, the brightest star just below the centre of this wide-field image, is a yellow hypergiant, a very rare type of stars with only a dozen known in our galaxy. 

Its size is over 1,300 times that of the Sun -- one of the 10 largest stars found so far. 

Observations with ESO's Very Large Telescope Interferometer have shown that it is actually a double star, with the companion in contact with the main star. 

Credit: ESO/Digitized Sky Survey 2

ESO's Very Large Telescope has revealed the largest yellow star—and one of the 10 largest stars found so far.

This hypergiant has been found to measure more than 1,300 times the diameter of the Sun, and to be part of a double star system, with the second component so close that it is in contact with the main star.

Observations spanning over 60 years also indicate that this remarkable object is changing very rapidly.

Olivier Chesneau

Using ESO's Very Large Telescope Interferometer (VLTI), Olivier Chesneau (Observatoire de la Côte d'Azur, Nice, France) and an international team of collaborators have found that the yellow hypergiant star HR 5171 A is absolutely huge—1300 times the diameter of the Sun and much bigger than was expected.

This makes it the largest yellow star known. It is also in the top ten of the largest stars known, 50% larger than the famous red supergiant Betelgeuse and about one million times brighter than the Sun.

"The new observations also showed that this star has a very close binary partner, which was a real surprise," says Chesneau.

"The two stars are so close that they touch and the whole system resembles a gigantic peanut."

The astronomers made good use of interferometry to combine the light collected from multiple individual telescopes, effectively creating a giant telescope up to 140 metres in size.

The new results prompted the team to thoroughly investigate older observations of the star spanning more than sixty years, to see how it had behaved in the past.

Chesneau concludes "The companion we have found is very significant as it can have an influence on the fate of HR 5171 A, for example, stripping off its outer layers and modifying its evolution."

This new discovery highlights the importance of studying these huge and short-lived yellow hypergiants, and could provide a means of understanding the evolutionary processes of massive stars in general.

More information: This research was presented in a paper "The yellow hypergiant HR 5171 A: Resolving a massive interacting binary in the common envelope phase", by Chesneau et al., to appear in the journal Astronomy & Astrophysics. arxiv.org/pdf/1401.2628v2.pdf

JAXA ALOS Image: Heart of the Atacama from orbit

The Japanese Advanced Land Observation Satellite (ALOS), captured this image on 30 May 2010.

Credit: JAXA/ESA

This ALOS satellite image shows the heart-shaped Miscanti lake and smaller Miñiques lake in northern Chile.

The lakewater is brackish – meaning that it's saltier than freshwater, but not as much as seawater.

This is due to the salinity in the soil. Chile's largest salt flat, the Salar de Atacama, lies to the west (not pictured).

Two partially snow-covered volcanoes can be seen above and below the lakes on the right, while plains stretch out to the west in a nearly vegetation-free environment.

The area pictured is part of the Atacama Desert, which runs along part of South America's central west coast.

It is considered one of the driest places on Earth, as moisture from the Amazon Basin is blocked by the Andes to the east, as well as from the Pacific Ocean by the Chilean Coastal Range to the west.

Pacific Ocean currents and wind circulation also play a major role in the desert climate.

Because of the Atacama plateau's high altitude, low cloud cover and lack of light pollution, it is one of the best places in the world to conduct astronomical observations and home to two major observatories.

The European ESO ALMA Observatory is located on the Atacama Plateau.

Some areas of the desert have been compared to the planet Mars, and have been used as a location for filming scenes set on the red planet.

Just last year, ESA tested a self-steering rover in the Atacama, which was selected for its similarities to martian conditions.

ESA MARS Rover: Atacama Desert the site of a Mars simulation

In early October 2013, the Atacama Desert became the site of a Mars simulation for a week, as a team of scientists and engineers visited the area to test out their prototype Mars rover.

The test site is located close to European Southern Observatory’s (ESO) Paranal Observatory and was selected due to its harsh climate and its physical resemblance to the red planet.

Additionally, the Atacama Desert is known for its virtually sterile soil, largely due to the lack of moisture in the region: this makes the area particularly suitable for simulating the lifeless Martian environment.

The recent trials in Chile have featured a rover named Bridget (provided by EADS Astrium, Stevenage in the UK), which is part of the SAFER field trials (Sample Acquisition Field Experiment with a Rover).

ESA’s 2018 ExoMars mission is acting as the reference mission for the trial.

The project aims to give the science team first-hand experience of remotely operating a rover, and acquiring field data from the three instruments during a field trial.

The rover operation will be run so as to be as near to a real mission as possible for the science team and the remote control centre.

Parallel testing is taking place from the UK’s remote control centre based at the Satellite Applications Catapult Centre in Harwell.

The three instruments on trial are CLUPI (a close-up imager), which is the equivalent of a geologist’s hand lens used for examining the fine details of rocks, a PanCam (panoramic camera) emulator called AUPE-2, and a ground penetrating radar called WISDOM, which will provide a detailed view of the Martian subsurface structure.

NASA tests Zoe, the new Mars rover prototype, in Chile

NASA scientists said Friday they were testing a prototype of a robot the US space agency hopes to send to Mars in 2020 in Chile's Atacama desert.

NASA hopes to use this kind of rover to explore life-friendly sites found by Curiosity, the rover already searching for signs of life on Mars.

It has been there since last August.

The researchers say the desert, the driest spot on Earth, mimics the conditions of the Red Planet, and the agency has used it in the past to test space-bound equipment.

The robot, controlled remotely from the US, will continue testing through Sunday.

The solar-powered 771-kilogram (1,700-pound) machine is equipped with cameras and a drill able to dig up to a meter (three feet) deep.

It is testing its sensors, its cameras, its ability to store energy, as it searches for evidence of microbial life in the desert.

The Zoe robot will use a one-meter drill, shown here protruding above the robot's solar cell deck, to search for subsurface life in Chile's Atacama Desert. 

Carnegie Mellon University's Robotics Institute and the SETI Institute are leading the NASA-sponsored field experiment. 

Credit: Carnegie Mellon University

ESO: Snow Falling on ALMA Telescopes

Credit: ESO/José Francisco Salgado

This image shows a wintry La Silla Observatory in Chile’s Atacama Desert sitting beneath the Milky Way.

Despite the telescopes’ location in one of the best areas for astronomical observation, at an altitude of 7800 feet (2400 meters), the desert cannot completely escape winter weather, including snow blanketing the mountain peak and telescope domes.

The high altitude sites operated by the ESA European Southern Observatory (ESO) can experience both hot and cold temperatures through the year, including sometimes harsh conditions.