Leo I (dwarf galaxy)

Leo I (dwarf galaxy)

Leo I is a small, round galaxy in the sky area called the constellation Leo. It is very far away, about 820,000 light-years from us. This puts it in a group of galaxies named the Local Group, which includes our own Milky Way galaxy. Scientists think Leo I might be one of the farthest objects moving around our Milky Way.

Leo I was first seen in 1950 by a scientist named Albert George Wilson. He noticed it while looking at pictures taken with a big camera at Palomar Observatory. These pictures were part of a project to map the night sky, and they helped find many interesting faraway objects.

Visibility

Leo I is found just 12 arc minutes away from Regulus, the brightest star in the constellation Leo. Because of this, it is sometimes called the Regulus Dwarf. The light from Regulus makes it harder to study the galaxy.

Because Regulus is very bright and Leo I does not shine very strongly, it can be tricky to see. You usually need a medium-sized telescope, like one that is 15 cm or bigger, and a very dark sky to spot it.

Mass

Scientists looked at how some bright stars move in Leo I. They found its mass is at least (2.0 ± 1.0) × 10⁷ M_☉. We do not know if there is a lot of invisible material, called dark matter, around the galaxy. One study thought there might be a very big black hole in the center, but another study did not find this. Among the small galaxies close to the Milky Way, Leo I has a lot of dark matter.

Some people think Leo I might be part of the outer edge of the Milky Way, but this is not certain.

Star formation

Leo I has very few heavy elements, only about one percent of what our Sun has. The Hubble Space Telescope shows that most of its stars formed between 6 and 2 billion years ago. Before that, there were almost no stars.

About a billion years ago, star formation in Leo I slowed down. This may have happened because it passed close to the Milky Way and lost the gas it needed to make new stars. A small amount of star formation might have continued until 200 to 500 million years ago. Because of this, Leo I is one of the youngest small galaxies near our Milky Way. It might also be surrounded by a cloud of glowing gas.