Arp240
Galaxy in Virgo
About
Two spiral galaxies in Virgo, NGC 5257 and NGC 5258, pull on each other and are linked by a tidal bridge. Wikipedia gives distances of about 342 to 345 million light-years. Arp listed the pair under "Galaxies with the appearance of fission".
Imaging tips
- Each galaxy is under 2′ across (1.8 × 0.9′ and 1.7 × 1.1′), so the pair is too small to frame by focal length alone: use a long focal length and a fine pixel scale.
- Faint at 23.1 mag/arcsec², so plan many hours of broadband data. One imager collected 4 hours: 150 minutes of luminance plus 30 minutes each of red, green and blue.
- That 4-hour frame covered a 38.6′ field and held both galaxies.
- Best around April and May; it stays below 41° from 50°N.
Facts
- Size
- 3′ × 2′
- Magnitude
- 12.5
- Coordinates
- RA 13h 39.9m, Dec +0° 50′
- Framing, APS-C
- longer than 4000 mm
- Framing, full frame
- longer than 4000 mm
- Best months
- Apr, May
- Peak altitude
- 41° from 50°N, 56° from 35°N