Astronomers from the European Southern Observatory (ESO) on Monday released a colorful image of a small galaxy in the constellation of Sagittarius.
The Sagittarius Dwarf Irregular Galaxy. Image credit: ESO / M. Bellazzini et al.
The snapshot, taken with the VIsible Multi-Object Spectrograph (VIMOS) instrument on ESO’s Very Large Telescope in Chile, shows the faint and fuzzy blue group of stars, which is just 3,000 light-years in diameter.
The object is officially known as the Sagittarius Dwarf Irregular Galaxy, or ‘SagDIG’ for short.
Don’t confuse it with another nearby dwarf galaxy, the Sagittarius Dwarf Elliptical Galaxy (SagDEG).
SagDIG is classified as an irregularly shaped — hence the name — dwarf galaxy.
It was discovered by French astronomer Diego Cesarsky and colleagues on a photographic plate obtained on June 13, 1977, with the 1-m Schmidt telescope at ESO’s La Silla observatory.
At a distance of 3 million light-years, SagDIG is the most distant member of the Local Group of galaxies, of which our own Milky Way Galaxy is a member.
This wide-field view shows the sky around the Sagittarius Dwarf Irregular Galaxy. Image credit: ESO / M. Bellazzini et al.
Unlike normal galaxies, dwarf galaxies are typically smaller and host a relatively small number of stars.
Gravitational tugs from nearby galaxies can often distort the spherical and disc-like shapes of these fragile objects — this very process may be responsible for SagDIG’s rectangular shape.
What’s more is that its brightest blue stars are asymmetrically distributed, being concentrated on the eastern side of the galaxy.
SagDIG is not only distorted and very small but also has relatively few elements more massive than helium.
The lack of heavy elements might mean that SagDIG is very young, so that component stars had little time to create and disperse massive elements.
Conversely, SagDIG’s small size could indicate that it formed in the early Universe, being a surviving building block of modern large galaxies.
