NEBULAE
From NGC 2077 to NGC 2055
— NGC 2048 to NGC 2081, in the Large Magellanic Cloud —
Processed by Nicolas Rolland, Paris. 70.7 hours gathered by Martin Pugh at El Sauce Observatory, Rio Hurtado, Chile.
Every glowing thing in this frame is in another galaxy. Nothing here belongs to the Milky Way except the foreground stars.
Nurseries in the Large Magellanic Cloud
These HII regions all sit in the Large Magellanic Cloud, 170,000 light-years away, close on the sky to the Tarantula Nebula. The Cloud is rich in gas and dust and forming stars at a rate our own galaxy no longer matches: around 60 globular clusters, 400 planetary nebulae and 700 open clusters have been catalogued in it. What looks like a scattering of separate nebulae is one galaxy's worth of star formation seen from outside.
Two thousand light-years across
The mosaic covers 39 by 42 arcminutes. At the distance of the Cloud that is close to two thousand light-years from one side of the frame to the other — a span that would reach most of the way from the Sun to the Orion Nebula. Everything catalogued below fits inside it, and the reason they are catalogued separately is that from here they are separate: at 170,000 light-years, the gaps between them are wide enough to name.
What is in the field
Seven objects carry their own designations, and the dates say something about how they were found: those from 1826 were catalogued in one survey of the southern sky, those from 1834 in another eight years later.
- NGC 2048: emission nebula, catalogued 1826
- NGC 2050: open cluster, catalogued 1834
- NGC 2055: open cluster, catalogued 1826
- NGC 2073: emission nebula, catalogued 1826, containing a group of very young stars
- NGC 2077: emission nebula, catalogued 1826
- NGC 2079: emission nebula, catalogued 1826, part of a group with NGC 2078, NGC 2083 and NGC 2084
- NGC 2081: open cluster with an associated emission nebula, catalogued 1834
Seventy hours, and two versions of them
The CDK17 was working at f/6.8 with adaptive optics ahead of the sensor, from Rio Hurtado in January 2022, across two panels. There are two images here, and they come from one dataset. The first is 51.2 hours: 19.5 in H-alpha, 19.5 in OIII, and 12 across red, green and blue for the star colours. The second adds 19.5 hours of SII and runs to 70.7. Those extra 19.5 hours buy no new structure — SII traces the same ionised gas as the other two lines and adds no detail the H-alpha does not already have. What they buy is a separation: three lines instead of two can be mapped to three channels, and gas at slightly different excitation states comes out in different colours. The slider shows what nineteen and a half hours of a third filter changes, which is a question of reading rather than of reach. Martin Pugh gathered the data at El Sauce.
- NGC 2048 : nébuleuse en émission, cataloguée en 1826
- NGC 2050 : amas ouvert, catalogué en 1834
- NGC 2055 : amas ouvert, catalogué en 1826
- NGC 2073 : nébuleuse en émission, cataloguée en 1826, qui renferme un groupe de très jeunes étoiles
- NGC 2077 : nébuleuse en émission, cataloguée en 1826
- NGC 2079 : nébuleuse en émission, cataloguée en 1826, membre d'un groupe avec NGC 2078, NGC 2083 et NGC 2084
- NGC 2081 : amas ouvert associé à une nébuleuse en émission, catalogué en 1834
