Arp104
Galaxy in Ursa Major
About
Keenan's System, the galaxies NGC 5216 and NGC 5218 in Ursa Major, tied together by stellar and gaseous material, a bridge roughly 22,000 light-years in extent. Philip Keenan published on the bridge in 1935, and Arp placed the pair among elliptical galaxies connected to spirals.
Imaging tips
- Too small to frame at typical focal lengths: use a long focal length and a fine pixel scale.
- Faint at 23 mag/arcsec², so plan many hours of broadband data.
- One imager collected 17.8 h through a 152 mm refractor over four nights: 81 × 600 s of luminance plus about 4 h of colour, with many other galaxies in the field.
- Another imager's 2 h 23 min of LRGB in a 33′ field held both galaxies.
- Best from March to May; it peaks near 77° altitude from 50°N.
Facts
- Size
- 3′ × 2′
- Magnitude
- 12.4
- Coordinates
- RA 13h 32.2m, Dec +62° 44′
- Framing, APS-C
- longer than 4000 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- Mar, Apr, May
- Peak altitude
- 77° from 50°N, 62° from 35°N