Astronomers who observed a turbulent star-forming region using the Atacama Large Millimeter/submillimeter Array’s (ALMA) highest frequency capabilities detected jets of water vapor streaming from a massive newborn star approximately 4,300 light years away.
ALMA uses an array of very precise antennas to study high-frequency radio light waves and was recently equipped with shortwave capabilities, enabling it to see a region in the electromagnetic spectrum at the boundary between infrared and radio wavelengths.
Located in the direction of the constellation Scorpius, the region observed, a section of the Cat’s Paw Nebula or NGC 63341, is an active stellar nursery. Previous ALMA observations of it at lower frequencies revealed it to be an active environment that harbors complex organic molecules.
On April 5, 2018, a team of scientists used ALMA to observe this region with the new, high-frequency technology. The Chilean observatory does this by assigning a series of “bands” designated one through 10, each of which studies a very small part of the spectrum. Band 10, the highest frequency, was used to look at the nebula’s star-forming region.
Two major discoveries were made from these observations–water vapor streaming away from a newborn star in jets and the fingerprints of a variety of molecules.
“High-frequency radio observations like these are normally not possible from the ground. 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,” explained Brett McGuire of the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia.
ALMA detected the submillimeter wavelengths that are the fingerprints of light emitted by heavy water, a form of water in which some or all of the hydrogen molecules are replaced by the hydrogen isotope deuterium.
“Normally, we wouldn’t be able to directly see this particular signal at all from the ground. Earth’s atmosphere, even at remarkably arid places, still contains enough water vapor to completely overwhelm this signal from any cosmic source. During exceptionally pristine conditions in the high Atacama Desert, however, ALMA can in fact detect that signal. This is something no other telescope on Earth can achieve,” said Crystal Brogan, also of NRAO.
Most of the material in the protoplanetary disks surrounding baby stars falls onto them. However, a small amount of this material, including heavy water, gas, and other molecules, is instead directed away from these stars in the form of jets traveling in opposite outward directions.
A paper on the findings has been published in Astrophysical Journal Letters.