Mercer 3 is a heavily obscured globular cluster

Globular cluster

A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers. The name of this category of star cluster is...

 embedded in the disk of the Milky Way

Milky Way

The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

 galaxy. It was discovered in 2008 in the data obtained by 2MASS

2MASS

Observations for the Two Micron All-Sky Survey began in 1997 and were completed in 2001 at two telescopes located one each in the northern and southern hemispheres to ensure coverage of the entire sky...

 and GLIMPSE

Spitzer Space Telescope

The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...

 infrared

Infrared

Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 surveys. The cluster is located in the Scutum constellation. It had avoided detection for such a long time due to the extremely strong foreground extinction

Extinction

In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 in its direction reaching 24 magnitudes in the visible light. Mercer 3 is probably situated at the distance from 4 to 8 kpc

KPC

KPC is an abbreviation for* kiloparsec, a unit of measurement used in astronomyKPC is an acronym for* Kaltim Prima Coal, A thermal coal mining in Kalimantan Timur, Indonesia....

 from the Sun and has a half-light radius of 0.7–1.5 pc.

Mercer 3 is an old globular cluster having the age of about 12 billion years. The mass of cluster is estimated at 2–3 hundred thousand solar mass

Solar mass

The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...

es.