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3C 66A


 Annotated photo

This is what I photographed through my 254mm Newtonian, rotated and annotated to mark reference stars of known magnitudes.

Annotated photo of 3C66A

Canon EOS5DMkII 254mm Newtonian @ 1200mm 100 x 10s f/4.8 ISO3200 2010-3-2 19:26:17-19:52:20 UT
From Whitley Bay 55.1N 1.5W 10m asl. Suburban, significant light pollution (6.5 Bortles)

This is a busy region of the sky in which there are several galaxies, the fuzzier spots in the photo. (Also a satellite left a track across one of the 100 frames that make up the photo and I forgot to omit that frame when using GRIP to combine them.)

 What is it?

Identifiers that begin with 3C are from the 3rd Cambridge catalogue of celestial radio sources, published in 1959. Some of the radio sources have subsequently been identified with objects visible optically. 3C66 is one such, except that it comprises two components, A and B. 3C66B is a galaxy emitting at radio wavelengths but 3C66A is of a type known as BL Lac. The first example of the type was originally thought to be a variable star in the constellation Lacerta (Lac) and it had the designation BL. Such objects are now known not to be stars but Active Galactic Nuclei (AGN). These are very small regions (solar-system-sized) at the centres of galaxies and outshining their galaxies by far.

So 3C66A is an AGN, of a sub-type known as a blazar. It is thought that it is so bright because what we see is a jet of gas pointing roughly in our direction. Its intensity is highly variable and therefore worth measuring repeatedly. Its distance is immense: 5 billion (5 x 109) light years. However, there is some uncertainty in this distance measurement because it is based on a red-shift determination based on a single spectral line.

Anyway, this photo stretches my personal record distance for photography significantly further.

 How to find 3C 66A...

... by navigating from a naked eye star (60 And). North is up, east to the left.

Star chart for finding 3C66A

 How bright?

It is fairly easy to see in the annotated photo above that 3C66A is brighter than reference star L but not as bright as K. From the table below we can therefore see that its magnitude is about 13.5 or so.

Using GRIP's photometric capabilities to do a least squares fit to BAA VSS reference stars B, C, H, K, L, M and N (tabulated below) on my original photo (taken at JD 2455258.31896) produced mV = 13.87 ± 0.12 (95% confidence).

Cross-reference between BAA VSS chart 309-01 and AAVSO chart 2015wc

RA (2000)Dec (2000)BAA VSS idV magAAVSO idNotes
02h22m43.99s43d05m28.9sA13.693000-BBD-768May be variable - do not use
unknownunknownH12.8n/aIn BAA list but not AAVSO

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