Andromeda I is a

dwarf spheroidal galaxy A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population. They are found in the Local Group as companions to the Milky Way and to systems that are comp ...

(dSph) about 2.40 million

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s away in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Andromeda. Andromeda I is part of the local group of galaxies and a

satellite galaxy A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy (also known as the primary galaxy). Satellite galaxies and their constituents are bound ...

of the

Andromeda Galaxy The Andromeda Galaxy (IPA: ), also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy with the diameter of about approximately from Earth and the nearest large galaxy to the Milky Way. The gala ...

(M31). It is roughly 3.5 degrees south and slightly east of M31. As of 2005, it is the closest known dSph companion to M31 at an estimated projected distance of ~40 kpc or ~150,000 light-years. Andromeda I was discovered by

Sidney van den Bergh Sidney Van den Bergh, OC, FRS (born 20 May 1929 in Wassenaar) is a retired Dutch-Canadian astronomer. He showed an interest in science from an early age, learning to read with books on astronomy. In addition to being interested in astronomy. ...

in 1970 with the

Mount Palomar Observatory Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

48-inch

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

. Further study of Andromeda I was done by the

WFPC2 The Wide Field and Planetary Camera 2 (WFPC2) is a camera formerly installed on the Hubble Space Telescope. The camera was built by the Jet Propulsion Laboratory and is roughly the size of a baby grand piano. It was installed by servicing mission ...

camera A camera is an Optics, optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), ...

of the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

. This found that the

horizontal branch The horizontal branch (HB) is a stage of stellar evolution that immediately follows the red-giant branch in stars whose masses are similar to the Sun's. Horizontal-branch stars are powered by helium fusion in the core (via the triple-alpha process) ...

stars, like other dwarf spheroidal galaxies were predominantly red. From this, and the abundance of blue

stars, along with 99

RR Lyrae RR Lyrae is a variable star in the Lyra constellation, figuring in its west near to Cygnus. As the brightest star in its class, it became the eponym for the RR Lyrae variable class of stars and it has been extensively studied by astro ...

stars detected in 2005, lead to the conclusion there was an extended epoch of

star formation Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space

. The estimated age is approximately 10 Gyr. The Hubble telescope also found a

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

in Andromeda I, being the least luminous galaxy where such a cluster was found.

References

External links

* {{DEFAULTSORT:Andromeda 01 Dwarf galaxies Dwarf spheroidal galaxies Peculiar galaxies Local Group Andromeda Subgroup Andromeda (constellation) 02666 Astronomical objects discovered in 1970 lt:Andromedos ūkas

See also

References

External links