M 109 Deep sky · Galaxy in Ursa Major · M 109 · NGC 3992
Vacuum Cleaner Galaxy
A barred spiral just beside Phecda, the bottom corner of the Big Dipper’s bowl nearest the handle.
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- Type
- Galaxy
- Designations
- M 109 · NGC 3992
- Constellation
- Ursa Major
- Apparent magnitude
- 9.9
- Apparent size
- 8′ × 5′
- Position (J2000)
- RA 11h 58m · Dec +53° 22′
The full Moon, about 31′ across, is 4.1 times as wide. The Sun comes no nearer to it than 47°, around late August, so it is never lost in the Sun’s glare, which reaches about 15° out.
When to see it
On the night of Fri 19 Mar 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT | Never sets | 00:10 · 88° | — |
| New York EDT | Never sets | 01:04 · 77° | — |
| Singapore GMT+8 | 19:09 | 01:15 · 38° | 07:21 |
| Sydney GMT+11 | 23:22 | 01:06 · 3° | 02:50 |
Common questions
- Can I see it from 50° north?
- Yes, on any clear night of the year. From there it never sets: it is circumpolar, circling the pole and still 13° up at its lowest.
- Can I see it from 35° south?
- Only just. At its highest it is 2° above the northern horizon, so it needs a clear, flat view that way and clean air.
- When is the best time of year to see it?
- Around mid March, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by mid June it is highest in the early evening, and in mid December not until the hours before dawn.
- How bright is it?
- Magnitude 9.9 in total, but that light is spread over 8′ × 5′ of sky: on average 22.4 magnitudes per square arcsecond. Against a dark country sky that average stands out; a city’s glow drowns all but its brightest parts.
- Naked eye, binoculars or telescope?
- Binoculars. At magnitude 9.9 it is past the eye, but a 50 mm pair under a dark sky reaches about magnitude 11.0.
Look for
It sits just south-east of Phecda, whose glare makes it harder than its brightness suggests. A small telescope shows an oval glow with a brighter bar across it.
Science
Its bar is a straight lane of stars across the centre, with the arms trailing from its ends — the same shape astronomers now think the Milky Way has.
Look for
From 50° north it is circumpolar and never sets; from 35° north it climbs to 72°; from the equator it climbs to 37°; from 35° south it barely clears the horizon, at 2°.
Look for
Magnitude 9.9 against the faintest star each can show: the eye under a city sky, 4.5 (5.4 short); the eye under a dark country sky, 7.0 (2.9 short); 50 mm binoculars under that dark sky, 11.0 (1.1 to spare); a 100 mm telescope there, 12.5 (2.7 to spare). Those limits are for a point of light; its light is spread over its whole size, so it needs some of that margin in hand. Through 7×50 binoculars, whose field is about 7.1° across, it spans 2% of the field’s width; through a 100 mm telescope at 50×, a field about 1° across, it spans 13% of the field’s width.