Tag Archives: starts

This is the best place in the world to see the cosmos at night — if you can bear it

The Dome A, the highest ice dome on the Antarctic Plateau, is the best place on the planet to study the stars, providing the clearest views of the sky at night, according to new research, which will probably trigger the interest of astronomers ready to cope with the Antarctic cold weather.

Credit Flickr

Ice domes are the uppermost portions of ice sheets and rise high above the frozen terrain. The Dome A is considered one of the coldest places on Earth, with temperatures that can be as low as -90ºC (-130 Fahrenheit). That’s actually similar to the nighttime weather found on Mars.

That means that while it may be a great place for astronomers, its remote location and extreme conditions present significant challenges. Scientists that want to visit the Dome A would have to travel 1,200 kilometers (740 miles) into the interior of the Antarctic continent — and that’s after traveling to Antarctica itself.

“The combination of high altitude, low temperature, long periods of continuous darkness, and an exceptionally stable atmosphere, makes Dome A a very attractive location for optical and infrared astronomy. A telescope located there would have sharper images and could detect fainter objects,” said Paul Hickson, co-author of the study, in a press release.

For astronomers, light pollution isn’t just the only problem when looking at the night sky. Atmospheric turbulence can also affect clear views into space. That’s when the telescopes located at mid and high elevations become very useful, taking advantage of the weaker turbulence found at those locations.

Astronomers calculate the quality of the night sky view using a metric called the seeing number, which they measure in arcseconds. The lower the number, the lower the turbulence and the better the view they can get from the stars and the galaxies. In the elevated telescopes in Chile and Hawaii, the seeing number is 0.6 to 0.8 arcseconds.

At Dome C, which is another dome on the Antarctic Plateau, the number is between 0.23 and 0.36 arcseconds. This means that the continent is an ideal place to watch the night sky. The level of turbulence there is lower as the boundary layer, the lowest part of the Earth’s atmosphere.

Working with researchers from China, Canada, and Australia, Hickson showed in his study that the Dome A is actually better than the Dome C. They took nighttime measurements at that location, something that hadn’t been done before, and found out that the median seeing number was 0.31 arcseconds.

The researchers compared the two Antarctic sites and found that the measurements from Dome A at eight meters (26 feet) were much better than the ones taken at the same height at Dome C. The measurements from Dome A at this height were equivalent to the ones made at 20 meters (66 feet) at Dome C.

Dome A “is a natural laboratory for studies of the formation and dissipation of turbulence within the boundary layer,” wrote the authors in their paper. “Future measurements of weather, seeing and the low-altitude turbulence profile could contribute to a better understanding of the Antarctic atmosphere.”

The study was published in the journal Nature.

Oldest material on Earth is stardust found in meteorite

The oldest material known to exist on Earth was just discovered by a group of researchers, working on a meteorite that fell fifty years ago in Australia. The space object, which felt on Earth in the 1960s, had dust grains within that were formed 5 to 7 billion years ago, preceding the formation of the solar system.

Some of the pre-solar grains in the Murchison meteorite (inset) could have come from evolved stars similar to the Egg Nebula (pictured). Credit ESA/Hubble/NASA

Stars have life cycles, born when dust and gas floating through space find each other and then collapse in on each other and heat up. They continue to burn for billions of years until they die, setting off a supernova explosion. When that happens, they create particles known as stardust that are expelled into the universe eventually forming new stars.

Researchers from the Field Museum, the University of Chicago, ETH Zurich and other universities found presolar grains in the meteorite, which are minerals formed before the Sun was born. The stardust was trapped in the meteorites and remained unchanged for billions of years.

Presolar grains are usually hard to find as they are only found in about 5% of the meteorites that have fallen to Earth. The Murchinson meteorite, which fell in Australia in 1969, was filled with them. The study, published in the journal Proceedings of the National Academy of Sciences, now took a closer look at them.

“It starts with crushing fragments of the meteorite down into a powder,” said co-author Jennika Greer, from the Field Museum and the University of Chicago. “Once all the pieces are segregated, it’s a kind of paste, and it has a pungent characteristic – it smells like rotten peanut butter.”

The researchers worked to determine the age of the grains by measuring how long they had been exposed to cosmic rays in space. The rays are high-energy particles that travel through the galaxy and penetrate solid matter.

Some of the grains in the sample were the oldest ever discovered, the study found. Most of them were 4.6 to 4.9 billion years old, and some were even older than 5.5 billion years, something never seen before. For context, the Sun is 4.6 billion years old, and Earth is 4.5 billion.

Lead author Philipp Heck said: “Only 10% of the grains are older than 5.5 billion years, 60% of the grains are “young” (at) 4.6 to 4.9 billion years old, and the rest are in between the oldest and youngest ones. I am sure there are older pre-solar minerals in Murchison and other meteorites, we just haven’t found them yet.”

The findings revive the debate over whether or not new stars are formed at a steady rate or whether there are highs and lows in the number of new starts over time. Also, thanks to the findings, researchers now know that pre-solar grains float through space together in large clusters.