HVC 127-41-330 is a high-velocity cloud. The three numbers that compose its name indicate, respectively, the galactic longitude and latitude, and velocity towards Earth in km/s. It is 20,000 light years in diameter and is located 2.3 million light years from Earth, between M31

Andromeda Galaxy

The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...

 and M33

Triangulum Galaxy

The Triangulum Galaxy is a spiral galaxy approximately 3 million light years from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598, and is sometimes informally referred to as the Pinwheel Galaxy, a nickname it shares with Messier 101...

. This cloud of neutral hydrogen (detectable via 21 cm H-I emissions

Hydrogen line

The hydrogen line, 21 centimeter line or HI line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation is at the precise frequency of 1420.40575177 MHz, which is equivalent to the vacuum...

), unlike other HVCs shows a rotational component and dark matter. 80% of the mass of the cloud is dark matter. It is also the first HVC

HVC

HVC may refer to:*High velocity cloud, a common astronomical phenomenon*High vocal center, an area in the brain of a songbird controlling song*Himachal Vikas Congress, an Indian political party*Holographic Versatile Card, a piece of computer hardware...

 discovered not associated with the Milky Way galaxy or subgroup (subcluster).

Astronomer Josh Simon considers it a candidate for being a dark galaxy

Dark galaxy

A dark galaxy is a hypothetical galaxy composed of dark matter. Dark galaxies receive their name because they have no detectable stars and are theoretically invisible...

. With its rotation, it may be a very low density dwarf galaxy

Dwarf galaxy

A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Way's 200-400 billion stars...

 of unused hydrogen (no stars), a remnant of the formation of the Local Group

Local Group

The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...

.