Category: Galaxy

Late in 1774, the German astronomer Johann Bode began to look for nebulae and star clusters. On the last day of the year he was credited with the original discovery of two galaxies, later to become known as M81 and M82. Just 38′ apart, they make a fine pair in the northern sky of Ursa Major. The target of this picture is M82.

An irregular galaxy, M82 shows signs of disruption and star formation caused by a recent encounter with M81 and is a strong radio source as well .

The Breckland 20″ telescope was used for this image with a Canon 350D. Sub frames were kept short at 20 seconds using ISO 1600 to avoid star trailing and this is the result of a stack of 14.

Most of the GRAS telescopes have monochrome cameras so I haven’t done much with the one shot colour cameras. However, when I was looking for a telescope / camera combination for imaging M33 I realised that GRAS-003 (a Takahashi TOA-150 with an FLI 8300) fitted the bill exactly with the galaxy filling the frame.

Five 10 minute exposures later and this is the result:

M33 has a very low surface brightness due to the fact that it’s light is spread out over a large area. This makes it a difficult visual target but it responds well to long exposure photography.

While visible to the naked eye (given a low enough level of light pollution) no pre-telescope notes are made of it; you’d be unlikely to notice it unless you already knew it was there. It was catalogued by Messier in 1764 and was one of the first ‘Spiral nebulae’ observed by Lord Rosse.

At a distance of 2.8 million light years it is 50,000 light years across and contains around 30 – 40 billion stars.

Once you get past the members of the Local Group, the next nearest galaxies are in the Sculptor cluster. Back in November last year I posted an image of  NGC 253 and this time it’s the turn of NGC 247 in the constellation of Cetus.

 At a distance of about 12 million light years this is a rather distorted spiral galaxy, with a prominent star at one end and a sparce void at the other. Being relatively close, the galaxies in this group appear quite large, this one is about 2/3 of the diameter of the full moon in length but is too faint to be visible to the naked eye. The small galaxy in the lower right of the image is PGC002795 (ESO540-026).

This is a picture taken with GRAS-006 in Australia and consists of 3 five minute exposures. GRAS-006 is an RCOS 16? – FL 3654mm @ f/9.0 with an SBIG STL-1001E NABG camera.

Many people are familiar with the Leo Triplet of galaxies, M65, M66 and NGC 3628. In the Southern skies there’s a similar formation in the constellation Pavo of NGCs 6769, 6970 & 6971 at a distance of 190 million light years. All three galaxies are interacting and whilst the cores consist of elderly reddish stars the spiral arms are lit up with clumps of new stars formed by the gravitation interactions.

Many other members of the Pavo galaxy group are also visible in this picture.

This image was obtained with GRAS-008 and is a composite of 10x 5 minute exposures. The image has ben scaled down by a factor of 3 for display on this blog.

The constellation Draco is well placed, high in the sky at this time of year and contains some little known objects including this group of galaxies, NGC 5985, NGC 5982 & NGC 5981 (from left to right in the image).

NGC 5985 is classified as a barred spiral, 5982 an elliptical and 5981 is an edge on barred spiral. All three are about 100 million light years away and the field of view in this image is 23.6 arc minutes square.

I’ve had these images on my PC since the beginning of April while I tried to resolve an issue with calibrating them. Thanks to Arnie at GRAS, this is now solved and was due to a buggy camera driver not subtracting the camera pedestal value from each pixel.

Telescope is GRAS-1 with an FLI 1024 DM camera and this image is composed of eight 3 minute exposures.

I’ve now added another 20 minutes of luminance frames and 12 minutes each of red, green and blue to this data set and stacked with the original 20 minutes of luminance to create a colour image.

Just to the right of M83, 2 background galaxies are just visible. These are PGC724525 (closest to M83) and PGC48132 and are about magnitude 16.

M101 is another spiral galaxy in Ursa Major but because it is presented face on it is rather faint and difficult to see in binoculars unless you have a very dark sky. Overall, the spiral arms cover an area almost the size of a full moon. However, in small telescopes only the central core will be visible.

27 million light years away, it’s discovery is credited to  Pierre Méchain in 1871 and it’s spiral structure was first described by Lord Rosse in the 19th century using his 72″ reflector. It’s diameter of 170,000 light years is about twice the size of our own Milky Way galaxy. An unusual feature of this galaxy is the large number of star forming areas in the spiral arms. Some of these can be seen in this image as small bright regions with the characteristic blue tint of hot young stars.

Ongoing problems with tracking  limited the maximum sub-exposure times to 120 seconds and a lot of these still had trailed stars leaving me with a stack of 16. As a result, the final image is rather noisy.

Friday evening was clear with some haze low in the sky, but, with Ursa Major high in the sky, presented an opportunity to try imaging M81 again. The CG-5 mount had some problems with intermittent tracking resulting in a lot of trailed images which had to be discarded and the corrector plate of the Celestron 9.25″ was fogging on the inside due to the high humidity. None of the images obtained were of good quality and I suspect the secondary mirror had fogged as well.

Despite the problems, 19 2 minute images were stacked  and processed for this image:

Much more detail is apparent than in my earlier attempt. The Celestron is now drying out in a room with a de-humidifier running so hopefully the fogging problems won’t be repeated next time out.

The first galaxy to be discovered, outside of the local group, M83 was first catalogued as Lac.I.6 by Nicholas Louis de la Caille from his Cape of Good Hope observatory in 1752. It was re-catalogued by Charles Messier in 1781 who, observing from Paris, noted “it appears as a faint & even glow, but it is difficult to see in the telescope, as the least light to illuminate the micrometer wires makes it disappear. One is only able with the greatest concentration to see it at all”.

This monochrome image is a stack of 10 2 minute exposures using GRAS-15 in Australia processed in Maxim DL. Despite the near full moon this image clearly shows the dust lanes that wind their way down the spiral arms to the compact nucleus.

If the previous images of merging galaxies looked rather gentle then this is anything but. Several hundred million years ago, these galaxies were both spirals, rather similar to our own. Now, as the first image shows, they are almost totally disrupted with clumps of new stars ignited by the gravitational interaction.

The second image has been processed to over-expose the galactic cores and show the features that give this pair of galaxies their common name. Two gravity waves have produced long streams of stars, dust and gas stripped from the merging galaxies.

For astonomers wanting to study galactic interaction this pair present an ideal target as they’re are close neighbours at 45 million light years distance.

These images were produced on GRAS-15 and are a combination of 10x 300 second luminance frames binned at 1×1 and 6 each of red, green and blue filtered images binned at 2×2.