Solar System

(The Crane)

Representing a bird that Ancient Egyptians used to symbolise astronomers, Grus is a faint constellation that was devised by Johannes Bayer in 1603. It is surrounded by equally as faint constellations but it lies below the lonesome beacon of light that is the bright star Fomalhaut in Piscis Austrinus.

It contains many faint galaxies that need dark skies and large telescopes to see in any detail.

Grus Quartet:

A group of faint galaxies that need large apertures to see clearly. Three of them,
NGC 7582, NGC 7590 and NGC 7599 are close together with the fourth one, NGC 7552 being slightly further away from the others.

The most active members are NGC 7552 and NGC 7582 which are interacting with each other. This is evidenced by the high rate of star formation in both galaxies as well as a tidal stream stretching from NGC 7582. This stream can only be seen in photographs but might be visible in the largest amateur telescopes.

NGC 7424:

A large barred spiral galaxy that is one of the brightest and best in Grus. Majestic sweeping spiral arms whirl off a tiny golden bar. Bouquets of massive star clusters adorn the spiral arms, they are so large that they span 700 light years!

NGC 7424 is similar in size to the Milky Way at a 100 000 light year diameter, the galaxy lies at a reasonably nearby distance of 40 million light years.

IC 5148:

IC 5148 is a very large planetary nebula with an interesting structure. Unfortunately it is almost invisible at magnitude 13, so an OIII filter is crucial. It can be found near the star Lambda Gruis and it was discovered in 1894 by an amateur astronomer called Walter Gale.

The structure is an overlapping of two shells, it is possible that the pole of IC 5148 is the part that is facing us. In the middle is a 'hole' where no gas is present. This is likely caused by radiation pressure or stellar winds blowing the gas outwards from the central star.

There is some confusion over the designation of this planetary nebula as it also has IC 5150 asssigned to it. This planetary was also observed in 1899 by an American amateur called Lewis Swift who based the position on widefield images. The IC 5148 designation is based on the position given by Lewis Swift whereas IC 5150 is based on Walter Gale's observations. To further add to the debate, the description given by Gale is more accurate and describes the planetary as large and annular.