August 19, 2018
ALMA Spots Steam Jets In Outer Space Coming From A Protostar

The Atacama Large Millimeter/submillimeter Array (ALMA) in Chile has just reached a new milestone, reports Science Daily, citing the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia.

For the first time in its six-year career, scientists have tested ALMA's highest-frequency capabilities, specifically the telescope's Band 10 receivers, and have made two exciting discoveries.

Led by NRAO chemist Brett McGuire, the team used ALMA's Band 10 receivers to scope out an intriguing star-forming region within the Cat's Paw Nebula and spotted streams of heavy water (Hydrogen Deuterium Oxide, or HDO) coming from a still-forming star.

On top of that, the ALMA observations "also detected the 'fingerprints' of an astonishing assortment of molecules near this stellar nursery," NRAO announced in a news release.

According to the observatory, this 10th (and last) "band" of ALMA's antennas studies the highest frequencies (or shortest wavelengths) of the electromagnetic spectrum. The telescope's Band 10 receivers pick up wavelengths from 0.3 to 0.4 millimeters (787 to 950 gigahertz), which "straddles the line between infrared light and radio waves," explains NRAO.

"High-frequency radio observations like these are normally not possible from the ground," says McGuire. "They require the extreme precision and sensitivity of ALMA, along with some of the driest and most stable atmospheric conditions that can be found on Earth."

The results of this first-of-its-kind ALMA study were published on August 17 in the Astrophysical Journal Letters.

The team made their ground-breaking ALMA observations on the evening of April 5, when the required atmospheric conditions were met. On that occasion, the scientists pointed ALMA's instrument at the Cat's Paw Nebula and zoomed in on one specific region inside this fascinating nebula.

Located 5,500 light-years away in the Scorpius constellation, this emission nebula is also called Bear Claw Nebula or NGC 6334 and is home to stars ten times more massive than the sun, notes NASA.

With the help of ALMA's Band 10 receivers, the researchers took a highly detailed look at a star-forming region known as NGC 6334I, which lies 4,300 light-years from Earth.

"Previous ALMA observations of this region at lower frequencies uncovered turbulent star formation, a highly dynamic environment, and a wealth of molecules inside the nebula," explains NRAO.

The telescope's highest-frequency capabilities yielded impressive images of water vapor jets, which the astronomers believe are spewing either from a massive protostar dubbed MM1B or from an entire cluster of newly forming stars.

"Normally, we wouldn't be able to directly see this particular signal at all from the ground," said Crystal Brogan, NRAO astronomer and study co-author on the paper.

"This is something no other telescope on Earth can achieve," she added.

These heavy water jets are part of the material expelled by the still growing star as it amasses gas from the region's molecular cloud and streams outward, flowing north to south — in a different direction from other larger and older jets coming from NGC 6334I.

Follow-up observations with the National Science Foundation's Very Large Array uncovered that these HDO emissions also trigger low-frequency water masers — naturally occurring microwave versions of lasers, explains NRAO.

The second huge discovery made possible by ALMA's highest-frequency receivers revealed that NGC 6334I is teeming with a diversity of molecules, including glycolaldehyde, or the simplest sugar-related molecule.

"We detected a wealth of complex organic molecules surrounding this massive star-forming region," said McGuire, who noted that his team's results "show once again how ALMA will reshape our understanding of the universe."

Until now, the record for best-in-the-world observations of the area was held by the European Space Agency's Herschel Space Observatory. ALMA has now managed to shatter that record, reporting a 10-fold increase in spectral line observations.