A photograph of the Milky Way rising above the horizon. Depositphotos.

Masers, “Cosmic Lasers” Detected From The Sagittarius Stellar Stream

Scientists searched for maser emissions, "cosmic lasers" from interstellar and circumstellar medium. A total of 21 maser emissions were detected using two telescopes.

The amplification of stimulated emissions produces maser emissions, “cosmic lasers” from the interstellar and circumstellar medium. When studying the Milky Way’s kinematics, bright and compact maser sources make good targets. Maser, now a word in its own right, is the microwave-wavelength version of the laserMicrowave Amplification by Stimulated Emission of Radiation. Spectral line emissions are caused by stimulated emission. Astrophysical environments contain a variety of masers. Molecules such as hydroxyl (OH), water (H2O), methanol (CH3OH), and silicon monoxide (SiO) are among the most common. SiO, OH and H2O masers are found in the circumstellar envelopes of oxygen-rich evolved stars, while OH, H2O and CH3OH emit light in star-forming regions. A megamaser is an extragalactic maser whose brightness is a million times greater than the Milky Way’s. In galaxies with far infrared brightness and active galactic nuclei, OH megamasers are found. The innermost few parsecs of AGN were detected to have H2O megamasers.

An NTSC research team conducted a 22GHz water maser survey in Sagittarius stellar stream to inspect star clusters with O-rich asymptotic giant branches. Asymptotic giant branch stars (AGBs) are low or intermediate mass stars at the end of their evolutionary cycle when they appear as red giants on the Hertzsprung–Russell diagram. A total of 21 maser emissions were detected using two telescopes, the Nobeyama 45m and Tidbinbilla DSS-43 70m, of which 20 were unique discoveries.

A prominent stellar stream around the Milky Way is the Sagittarius Stellar Stream, which results from the merger and accretion of the Milky Way with its satellite dwarf galaxy, the Sagittarius Dwarf Spheroidal Galaxy. In an orbit near the galactic poles, the Sagittarius Stream is a long, complex structure composed of stars that surround the Milky Way galaxy. After billions of years of merging with the Milky Way, it consists of tidally stripped stars from the Sagittarius dwarf elliptical galaxy. Prof. Wu Yuanwei, leader of the research team, said that investigating this stream could assist scientists in probing galactic evolution and dark matter distribution.

Sagittarius’ orbital plane exhibited an elongated structure based on the maser-traced H2O and SiO AGB distributions. The team further studied the motions of masers in 3D to verify their relationship with the Sagittarius tidal stream. Results suggested that these sources are still from the thick disk of the Milky Way, with a remarkable outward motion velocity of ~ 50 km s-1 away from the Galactic center. The team further studied the motions of masers in 3D to verify their relationship with the Sagittarius tidal stream. Observations indicated that these sources were still in the Milky Way’s thick disk, moving outward at a remarkable speed of 50 km s-1. The Sagittarius stream must have maser emissions, but we still cannot confirm that they are there because of the sensitivity of the survey and sample bias. “We’ll try more samples in our future study.”

The results of the finding were published in Monthly Notices of the Royal Astronomical Society.

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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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