The Leo I Dwarf Galaxy is a diffuse, low-surface-brightness dwarf galaxy that presents one of the more demanding targets for deep-sky imagers. With an integrated apparent magnitude of 10 mag but a surface brightness spread thin at 23.9257 mag/arcsec², its light is scattered across an angular extent of roughly 11′, making it appear as little more than a subtle brightening against the background sky. Long total integration times, dark skies, and careful gradient handling are essential to coax its ghostly glow out of the noise. Compounding the challenge, the galaxy sits extremely close to the brilliant star Regulus, whose glare demands meticulous flat-fielding and light-pollution control to keep stray light from washing out the faint stellar haze.
Names and Catalog numbers
- Leo I Dwarf Galaxy
- UGC 5470
- PGC 29488
Position and the cosmic neighborhood
The Leo I Dwarf Galaxy is located in the constellation Leo at a right ascension of 10h 08m 28.12s and a declination of +12° 18′ 23.4″, placing it only a short distance from the bright star Regulus. This proximity makes it easy to locate in a star-hopping sense but notoriously difficult to photograph cleanly, as the star’s intense brightness floods the surrounding field. Also cataloged as PGC 29488 and UGC 5470, the galaxy spans about 2,760 light-years across and belongs to the family of dwarf companions that populate our own galactic neighborhood, offering imagers a rare glimpse of a small, faint stellar system so nearby.
Nice to Know
- Despite its overall magnitude of 10 mag, the galaxy’s very low surface brightness of 23.9257 mag/arcsec² makes it a genuine test of imaging skill and sky quality.
- It lies right next to Regulus, so managing that star’s glare is one of the biggest practical hurdles when photographing this target.
- At around 828,000 light-years, it is one of the closer dwarf galaxies, yet it still spans only about 2,760 light-years in physical diameter.
- Its measured radial velocity of 282.5 km/s corresponds to a redshift of z = 0.000942763, reflecting its motion relative to us.
Brightness, distance and size
The object has an apparent magnitude of 10.0 mag, it lies about 828,000 light-years from Earth and spans roughly 2,760 light-years across. On the sky it appears about 11′ in size.
