Corvus and Crater Arps - Arp22, Arp 244, Arp 289

[Mike JW]

Last night I cruised the length of Hydra picking up many galaxies. Conditions low down were good enough to allow for a look at Corvus and Crater.

Arp 22 (NGC 4027) in Corvus was classified by Dr Arp as a “one armed spiral”. Closer inspection suggests there is a second but much smaller arm. It is a barred spiral (SBc). There are different estimates of its distance. Sky Safari suggests 77 million lyrs away. The interesting question is why the galaxy has one very large arm and a much smaller second arm. Something in the past has messed up the galaxy. It is now suggested that nearby NGC 4027A (mag 14) may have passed by in the past and caused the disruption. It too has been messed up – type IB (irregular blue dwarf).  NGC 4027A is the irregular patch with a star knot just below the inset. Other folk have suggested NGC 4027 is a result of a merger.

 

Arp 244 (NGC 4038/39) – the Antennae Galaxies (63 million lyrs away or maybe even nearer at 45million lyrs away). These guys are busy colliding (an interacting galaxy pair) and in time the cores will become one giant core in a giant galaxy. I would love to have picked up the two streamers but at -18 DEC it is rare to get clear sky so low down. (I am sure the neighbours would have thought I was trying to see into their bedroom window!!!!!). Great to see the bursts of star formation. The collision began about 900 million years ago and they passed through each other and about 300 million years ago the two star streams began to form.

 

Arp 289 (NGC 3981) – “double galaxy with wind effect” in Crater. About 79 million lyrs away and mag 11.0. There is no obvious second galaxy. High resolution images show plumes, so what disrupted the galaxy to cause these star streams? But, these plumes maybe the nature of this galaxy, just faint extensions of the arms and not due to some interaction.

 

[Martin Meredith]

Nice write-up Mike. Arp 22 looks particularly intriguing.

I was looking through my very disorganised collection of Arps to see if I have any of these three but could only find the Antennae. This needs a long exposure and a big stretch.... (preferable with a clean sensor). This is the best I've been able to achieve to date. I have the advantage of observing at a lower latitude of course....

[Mike JW]

Thanks Martin, Your shot gives me an idea of the exposure needed. If there is another very transparent night I shall try again. Good to know it can be done using the EAA approach.

[roelb]

Arp 244 with a Lodestar X2 on a 6 SE @ F/5

8 x 30 s