New ALMA observations show there is ordinary table salt in a not-so-ordinary location: 1,500 light-years from Earth in the disk surrounding a massive young star. Though salts have been found in the atmospheres of old, dying stars, this is the first time they have been seen around young stars in stellar nurseries. The detection of this salt-encrusted disk may help astronomers study the chemistry of star formation as well as identify other similar protostars hidden inside dense cocoons of dust and gas.

Salty star

A team of Dutch and American astronomers and chemists has detected the chemical fingerprints of sodium chloride (NaCl) and other similar salty compounds. The salts emanated from the dusty disk surrounding Orion Source I, a massive, young star in a dusty cloud behind the Orion Nebula.

New horizons

Ciriaco Goddi, affiliated to Radboud University and the European ALMA Regional Center node in the Netherlands (ALLEGRO, Leiden Observatory) has been working on this particular object since 2007. The old data helped the team interpret the structures revealed in the disk by the new ALMA data. However, Goddi was stunned when he received the findings reporting the identifications of the salts by co-author Brett McGuire, a chemist at NRAO in Charlottesville, Virginia. 'Every time there is an unexpected discovery, new horizons open up in the field', Goddi said.

Unusual environment

'It’s amazing we’re seeing these molecules at all', said Adam Ginsburg, a Jansky Fellow of the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, and lead author of the paper appearing in the Astrophysical Journal. 'Since we’ve only ever seen these compounds in the sloughed-off outer layers of dying stars, we don’t fully know what our new discovery means. The nature of the detection, however, shows that the environment around this star is very unusual.'

Detection

The salty signatures were found about 30 to 60 astronomical units (AU, or the average distance between the Earth and the Sun) from the host stars. Based on their observations, the astronomers infer that there may be as much as one sextillion (a one with 21 zeros after it) kilograms of salt in this region, which is roughly equivalent to the entire mass of Earth’s oceans. The researchers speculate that these salts come from dust grains that collided and spilled their contents into the surrounding disk.

Next steps

'Our next step in this research is to look for salts and metallic molecules in other regions. This will help us understand if these chemical fingerprints are a powerful tool to study a wide range of protoplanetary disks, or if this detection is unique to this source,' said Ginsburg.

Publication

Orion SrcI’s disk is salty. By: Adam Ginsburg, Brett McGuire, Richard Plambeck, John Bally, Ciriaco Goddi, Melvyn Wright. Accepted for publication in The Astrophysical Journal (free preprint).

This article is based on the press release by The National Radio Astronomy Observatory.