Invisible Universe: Dark Matter, Galaxies & Dark Energy

[New Tang Dynasty Beijing Time August 15, 2025]Have you ever thought that the stars, planets and Milky Way that we can see with our naked eyes are just the tip of the iceberg of the universe? In fact, it can be seen that matter accounts for less than 5% of the universe, and the remaining 95% is dominated by a “invisible force”:Dark matterandDark energy。

Recently, astronomers found more than 250 “Mini galaxy”. These small galaxies may help scientists unravelDark matterThe secret.

What is “Mini galaxy”? Imagine the universe is like a huge hive with “hives” of all sizes – these are galaxies. The Milky Way is a “super hive” with hundreds of billions of stars. andDwarf systemIt is a small hive, only a fraction of the size of the Milky Way, or even smaller. Mini galaxies are smaller, and they usually surround dwarf galaxies, like “satellites in satellites.” For example, there are two friends in the Milky Way – the Big Magellanic Cloud and the Small Magellanic Cloud, which are themselves dwarf galaxies. Some of the mini galaxies discovered this time are comparable to the size of Magellan Clouds, but they are even dimmer and are invisible to ordinary telescopes before. Through ID-MAGE’s deep space image analysis, scientists identified 355 mini galaxy candidates, of which 264 are brand new. This almost tripled the number of known mini galaxies!

These small galaxies are like the “sensitive detectors” of the universe. Their gravity is very weak and is easily affected by the outside world, especially by the pulling of large galaxies. By studying how they form and interact, scientists can test the “building rules” of the universe. In addition to helping us understand how galaxies form, these interactions can also help scientists get important information about dark matter. Dark matter is a hypothetical, invisible matter that is believed to constitute a large part of the mass and energy of the universe.

The study was published in the Journal of Astrophysics, and scientists are continuing to observe and confirm with larger telescopes, such as the Green Bank Telescope. In the future, these data may disrupt our understanding of the universe, especially the part about dark matter.

Astronomical knowledge: Dark matter andDark energy

Dark matter is an invisible and intangible matter, but it affects everything through gravity. Why is it called “dark”? Because it does not emit light, reflect light, absorb light–not directly visible like stars or planets. Scientists have observed that galaxies rotate very quickly. If only visible stars and gases are counted, the periphery of the galaxy should fly away, but they are operating stably, which means that there is additional gravity “sticks” them. This extra gravity comes from dark matter, which accounts for about 27% of the mass of the universe. Without it, galaxies cannot be formed at all.

Dark energy plays the opposite role of dark matter, and it pushes away everything. Dark energy accounts for 68% of the total energy of the universe, which is the fundamental reason for the accelerated expansion of the universe. In 1998, scientists observed far-reaching supernova and found that the universe is not only expanding, but also expanding at an accelerated rate. This violated common sense at the time, that gravity should slow down the expansion of the universe. Scientists speculate that dark energy is like an antigravity that fills the entire space and always exists in an empty space. Dark matter pulls over galaxies, dark energy pushes them apart, forming a balance. But dark energy is stronger, so the universe is expanding faster.

(Reporter Li Siwen’s comprehensive report/Editor in charge: Lin Qing)

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