With the help of a spherical radio telescope with a 500-meter aperture (FAST, Five-hundred-meter Aperture Spherical radio Telescope), astronomers
Planetary nebulae areexpanding gas-dust shells ejected by a star in the course of its evolution. They are relatively rare, but important to astronomers studying the chemical evolution of galaxies.
Located about 8,000 light years fromEarth IC 4997 is a young, compact and rapidly developing nebula in the constellation Sagittarius. Its temperature is about 20,000 Kelvin (19,726.85 °C) and its surface has a relatively high surface brightness. The planetary nebula has a prominent central star with a temperature of about 49,000 K (48,726.85 °C).
Planetary nebula IC 4997 Credit & Copyright: Howard Bond (STScI) and NASA/ESA
A team of astronomers led by Xu-Jia Ouyangfrom Sun Yat-sen University in Zhuhai, China recently made a radio observation of IC 4997 using the tracking mode of a 19-beam FAST receiver. The telescope allowed them to detect the absorption of neutral atomic hydrogen in this nebula, which may be important for understanding its nature.
Object IC 4997 is not like the others.There are very few planetary nebulae (PNs) with circumstellar neutral atomic hydrogen compared to the total number of tested galactic DMs (about 3800). The discovery and study of such features could improve scientists' knowledge of the mass and dynamics of the balance of atomic gas in objects of this type.
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