Unidentified forces disturbing the outer Milky Way, scientists say they have found the source

The galaxy's size, distance, position, and motion of the stars in the Milky Way can be obtained by scientists using a variety of observation devices.

In 2013, the Gaia satellite was successfully launched, its mission is to observe the many stars in the Milky Way galaxy with high-precision equipment, so far, the satellite has returned about 2 billion stars observation data, making a significant contribution to a deeper understanding of the Milky Way galaxy.

In the process of studying the data returned by Gaia, scientists have found that the outer part of the galaxy seems to be disturbed by some unknown force, and as a result, strange tremors appear, which are manifested by a large number of stars in the outer region of the galaxy's disk structure " The stars are "oscillating" and "undulating" (relative to the galactic disk).

Scientists have described this phenomenon as if the Milky Way were a flat, tranquil pool of water, and a large rock had fallen into the "pool" and rippled. Why are there strange tremors on the outer side of the galaxy, and where are the unknown forces disturbing the galaxy coming from? With these questions in mind, scientists have conducted more in-depth research.

A team of researchers from Lind University in Sweden recently published a paper in the Monthly Notices of the Royal Astronomical Society saying that scientists have found the source of the disturbance in the outer regions of the Milky Way.

According to the researchers, the team used observations from the Gaia satellite to build a "wave model" and the simulations suggest that the strange tremors in the outer part of the Milky Way must have started hundreds of millions of years ago and that the phenomenon is caused by A satellite galaxy of the Milky Way, the Sagittarius Dwarf Elliptical Galaxy (Sag Deg), is responsible for this phenomenon.

The Sagittarius Dwarf Elliptical Galaxy is a dwarf galaxy about 10,000 light-years in diameter, first discovered in 1994, in the sky in the direction of Sagittarius, about 70,000 light-years from Earth. "(Saudi), which is only about 340 light-years from Earth, was discovered, it became the "second closest".

Observations show that the Sagittarius dwarf elliptical galaxy orbits the center of the Milky Way along a polar orbit at a distance of about 50,000 light-years from the galactic center, which means that during its orbit around the galactic center, the galaxy passes directly through the Milky Way, and the region it passes through is located on the outer side of the galactic disk structure.

Researchers note that the Sagittarius dwarf elliptical galaxy has passed through the Milky Way many times in the past, and hundreds of millions of years ago was the last time the Sagittarius dwarf elliptical galaxy passed through the Milky Way.

During this process, a large number of stars in the outer regions of the Milky Way were shifted from their original equilibrium positions by the gravitational effects of the Sagittarius Dwarf Elliptical galaxy, but they do not move away but oscillated in their original equilibrium positions due to the gravitational binding of the Milky Way, which causes them to push and undulate like waves in the whole, which in turn causes the region to exhibit a significant tremor effect, and even now This tremor still has not subsided.

The "unknown force" causing the strange tremors in the outer part of the Milky Way has its source in the Sagittarius dwarf elliptical galaxy.

Scientists believe that the Sagittarius dwarf elliptical galaxy is not "unscathed" during its passage through the Milky Way, but on the contrary, it is swallowed up by the Milky Way every time it passes through the galaxy, and it is estimated that the Sagittarius dwarf elliptical galaxy lost at least 20% of its mass during the last passage through the Milky Way. So it is not difficult to imagine that sooner or later, as time passes, this dwarf galaxy will be swallowed up by the Milky Way.

It is worth mentioning that the vast Milky Way galaxy that we see now has grown up through intergalactic cannibalization and mergers, and it will grow again in the distant future, because about 2.54 million light-years away, there is a galaxy larger than the Milky Way - Andromeda galaxy, is approaching the Milky Way at a speed of about 120 kilo meters per second.

In 3.75 billion years, the Andromeda galaxy is expected to meet the main structure of the Milky Way, after which the two galaxies will pass through each other several times and eventually merge into a huge elliptical galaxy.

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