In the deep dark of the universe,  there are by no means calm.

The famous Leo triplet is a case in point. This small group of galaxies is about 35 million light-years away and consists of three spiral galaxies of different shapes.

M65 on the southwest side (bottom right in the picture) is the least impressive, without much character, containing little gas and dust, with few new stars being formed, and the stars are so old that they look the most yellowish in color.

M66 to the southeast (lower left in the picture) is a different story. It has loose spiral arms, a dense dust belt, and large blue regions, implying the presence of bright young stars there. Over the past 50 years, astronomers have observed five supernovae in this galaxy, so it's safe to say that it's buzzing with activity.

NGC 3628, located to the north (top of the image), is not listed in the Messier catalog but is one of the most distinctive of the trio of galaxies. It faces us sideways, with a wide, thick band of dust splitting the galaxy in half, and is imaginatively called the Hamburger Galaxy.

At first glance, each of the 3 galaxies looks like it's in its element. But deeper exposures reveal fainter details that tell a history of violent rivalry between them.

The most obvious evidence is the long tail of the hamburger galaxy, which extends more than three times the diameter of the galaxy to the east (left in the picture), reaching 300,000 light-years long and containing material equivalent to about 500 million suns! This is the result of a close encounter with galaxy M66 about 800 million years ago.

According to astronomers' simulations, these two galaxies had leaned in as close as only 80,000 light-years back then and were almost about to collide. The two were fighting each other through gravity, and some of the material in the hamburger galaxy was thrown right out of the galaxy.

In fact, the "steaming" appearance of the hamburger galaxy, as well as the "X"-shaped bulge, are the consequences of that galactic collision.

With the extra squeeze on the gas and dust, star formation is happening on a large scale in the hamburger galaxy, and at the current rate, it won't be long (5-10 million years, a blink of an eye on galactic age scales) before the dust and gas, the raw materials for star formation, are depleted. For the rest of its long life, the galaxy will not be able to give birth to many new stars and will have to grow old in endless time.

Of course, the other side of the galaxy collision 800 million years ago, M66 on the lower left, despite having escaped to 300,000 light-years away, did not fare much better. In the deep exposure, we can see that its structure is extremely asymmetrical: the thick spiral arm extends far to the northwest (top right), but barely in the opposite direction; the core and brightest part of the galaxy is also off the center of the galaxy, and a large amount of gas has gathered at the core, with a mass 400 million times that of the Sun. These are the results of the gravitational backlash from the hamburger galaxy.

Only the inconspicuous M65 seems to be in a real calm as if it is completely untouched by the gravitational war between the other two galaxies. However, perhaps this is just a brief moment of calm before the storm. After all, its distance to M66 is only a mere 160,000 light-years, equivalent to the distance from the Milky Way to its companion galaxy, the Large Magellanic Cloud. The next galactic collision may already be unavoidable.