3D view of the Milky Way

(ORDO NEWS) — There are about 200 billion suns in our Milky Way, as well as a huge amount of gas, some of which is the raw material for the birth of stars. The gas can collect in compact lumps, but it can also manifest itself as extended molecular clouds. Astronomers used the upper submillimeter telescope in Chile to look deep into the galactic plane and measure the interstellar medium. They studied the distribution of cold molecular gas in the inner region of the Milky Way with unprecedented precision. Researchers have cataloged over 10,000 interstellar clouds.

They found that currently only about 10% of them contain stars. The project is called SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic Interstellar Medium) and covers an area of ​​84 square degrees in the southern sky.

The map contains data from 2013 to 2017 collected by the 12-meter Apex telescope in the Chilean Andes. “With the publication of this most detailed map of the coldest molecular clouds in the Milky Way to date, the long-term observational project is beginning to bear fruit,” says Frederick Schuller of the Max Planck Institute for Radio Astronomy, project leader for SEDIGISM.

Scientists were able to observe the southern part of the inner Milky Way with an angular resolution of 30 arc seconds, which corresponds to 1/60 of the apparent diameter of a full moon in the earth’s sky. They also obtained valuable information about the structure, distance and speed for all galactic molecular clouds in about two-thirds of the inner disk of the Milky Way.

The researchers observed the spectral lines of carbon monoxide molecules, including the rare isotopes 13CO and C18O, and deduced the mass and three-dimensional distribution of cold and dense molecular gas in the interstellar medium. Various structures have been found such as threads and grooves; they are the result of various physical effects.

Molecular clouds contain the raw material from which new stars are formed. Therefore, mapping these clouds is necessary to determine such important parameters as the efficiency of star formation in the Milky Way. The structures and physical conditions within the clouds provide the fundamental basis for theories of star formation.

The key to its success was the 12-meter telescope “Apex” with its high-precision surface and one of the world’s best locations for submillimeter astronomy. The device is located at an altitude of 5100 meters on the Chinantor Plain in the Chilean Atacama Desert. It has an extremely low water vapor content and therefore excellent atmospheric transparency.

The new data complements a series of mid- and far-infrared maps of the galactic plane over the past decade. This was done with space telescopes such as Spitzer, Herschel (for medium waves), and Apex (for longer waves). However, these projects lacked the information about the speed that SEDIGISM now has. Reanalysis of the data obtained allows a more detailed study of star formation, and therefore the structure and dynamics of the Milky Way itself.


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