Astronomers have created a method to search for faint planetary nebulae in distant galaxies

In their work, the scientists used a filtering algorithm when processing image data. So method

observations opens up new possibilities for measuring cosmic distances - and thus also for determining the Hubble constant.

Recall that the Hubble constant is a coefficient included in the Hubble law, which links the distance to an extragalactic object with the speed of its removal.

As you know, the planetary nebula -an astronomical object that is a shell of ionized gas around the central star, a white dwarf. Formed by the ejection of the outer layers of a red giant or supergiant with a mass of 0.8 to 8 solar masses at the final stage of its evolution.

Unlike the continuous spectrum of a star, ionscertain elements in this gas envelope, such as hydrogen, oxygen, helium and neon, emit light only at certain wavelengths. Special optical filters tuned to these wavelengths can make faint nebulae visible. The closest object of this type to the Milky Way is the Helix Nebula, 650 light-years from Earth.

As the distance to the planetary increasesthe apparent diameter of the image decreases, and the total apparent brightness decreases in proportion to the square of the distance. In the neighboring Andromeda galaxy, the Spiral Nebula will be visible only as a point, and its apparent brightness will be 15 million times fainter. However, with modern large telescopes and long exposure times, such objects can be displayed and measured using optical filters or image spectroscopy.

AIP research team with colleaguesfrom the United States has developed a method for using MUSE to isolate and accurately measure extremely weak signals from planetary nebulae in distant galaxies with high sensitivity. This is where a particularly efficient filtering algorithm plays an important role in image data processing. Archival ESO data is available for the ring galaxy NGC 474, based on two very deep MUSE exposures, each with an observation time of 5 hours. Scientists have published the result of data processing: after applying the filtering algorithm, 15 extremely faint planetary nebulae became visible.

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Hubble's Law (the law of universal recession of galaxies) is a cosmological law that describes the expansion of the Universe.