Astrophysicists see mysterious dark galaxies in the early universe behind a thick layer of dust

(ORDO NEWS) — Using high-powered radio telescopes, researchers have been able to see several galaxies in the early universe that were previously obscured by the dust surrounding them.

Not every galaxy is easy to see with a telescope. Many of them are hidden behind a layer of dust, which is not so easy to break through.

Measuring the rate at which stars are born in galaxies is one of the fundamental ways in which astronomers describe the properties and evolution of galaxies.

Various methods are used to estimate this so-called star formation rate, usually depending on the light emitted either by the stars or by the matter that is illuminated by the stars.

However, the stars that form, in turn, tend to create dust particles made up of heavy elements such as carbon, silicon, oxygen, and iron. Dust appears as thick clouds in the space between the stars, completely hiding the stars from our eyes.

This makes it difficult to determine the rate of star formation, especially in young “starburst” galaxies where the dust has not yet had time to dissipate in regions where stars form very quickly.

When dust is heated by stars, it begins to emit long-wavelength infrared light, which, although invisible to the human eye, can be detected by telescopes designed to observe these wavelengths.

Invisible galaxies

But in the most compact, dust-shrouded stellar flares, scientists only see the surface of the clouds. Such galaxies are not only invisible at “human-perceptible” optical wavelengths, but also at lower infrared wavelengths, and even the Hubble Space Telescope cannot see them.

However, with the help of radio telescopes, astrophysicists in a new article were able to detect early galaxies hidden from view, shrouded in dust.

Radio and microwave observations have allowed astronomers to measure the rate of star formation and the temperature of the dust.

The study explains why these galaxies are so dark in the optical and infrared range: all because the dust clouds are thick and dense, due to which optical and near-infrared light cannot pass through them. Even far infrared light is partially absorbed by them.

“Our model takes into account the fact that infrared light does not come out directly from the center of dust clouds.

This shows us that previous gas mass estimates were overestimated by a factor of 2-3 for compact, dusty, star-forming galaxies,” explains one of the authors of the work, Shuoven Jin.

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