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Latest Website Update [2 April 2015] >> New Galaxy of the Month NGC 4330 >> New Double Stars for April >> It's back and NGC 2736 is Picture of the Month

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April 2015 - Picture of the Month

NGC 2736 (the Pencil Nebula) in Vela

NGC 2736 - Image Courtesy of Steve Crouch

Image Courtesy of Steve Crouch, Canberra, Australia. Please click on the image for the high resolution version.

Steve's Description

NGC 2736 is known as the pencil nebula and is an outlying filament of the Vela supernova remnant the centre of which being some 4 degrees to the west. It was discovered by John Herschel in 1834 and is sometimes called Herschel's ray.

Camera and Telescope
STXL6303 and 36.8 cm Ritchey Chretien
Exposure Details
Ha:OIII:OIII with LRGB data. About 31 hours total imaging time.

For more images from Steve please visit his CCD Astronomical Images from Canberra website.

Object of the Season (Spring 2015)

NGC 6572 in Ophiuchus

Planetary Nebula NGC 6572 in Ophiuchus will be announced in DSO 167, and the results will be published in DSO 169.

NGC6572 - Image Courtesy of Hubble Space Telescope (HST) This image was supplied by the Hubble Space Telescope (HST).

Position (2000)
18 12 06.4 +06 51 15 (Oph)
Visual magnitude
8.1 mag
Central Star
13.6 mag
Size
0.6' x 0.4'
Distance
2500 ly
Other Designations
Σ 6, h 2000, GC 4390, PK 34+11-1, VV 159, ARO 7

Wolfgang Steinicke - Nebulae and Clusters Section Director

April 2015 - Double Star of the Month

STF1555 (11 36 17.94 +27 46 52.7) is in Ursa Major in a fairly sparse part of the constellation down by the Bear's front foot. It is perhaps most eassily found by moving 5 degrees south-east from the bright binary xi UMa (STF1523). This was an easy pair for the small aperture at discovery at 1".4 but during the next one hundred years the two stars approached each other until minimum separation of about 0".1 was reached in the 1930s and since then they have been separating. The nature of this system is a little unclear but observations over the next decade or so will show whether it is an optical pair (as classified in the WDS, or a highly inclined binary system, as suggested by Docobo in 2007 when he derived an orbit of 916 years for it. The orbit predicts star B beginning to turn back towards A with the separation slowly decreasing again. In spring 2015 B can be found at 150°, 0".67. The stars are magnitudes 6.4 and 6.8, and a third component of magnitude 11.2 which is listed as HJ 503, can be seen at 158° 22".5, both values are slowly increasing.

RMK 14 (12 14 02.71 -45 43 26.1) can also be found by reference to a nearby bright binary star. It forms an isoceles triangle of side about 5 degrees with gamma and delta Centauri to the south. Unfortunately, as of early 2015, gamma is near closest separation and needs a large aperture to resolve but RMK 14 (D Cen) is a beautiful pair which is worth searching out. The primary is a K3 giant of visual magnitude 5.8 and is also known to be a spectroscopic binary. The companion can be found at 243° and 2".7 having closed up from 4" at discovery. This is a distant pair - Hipparcos lists the parallax as 5.71 mas which, as it happens, translates to 571 light years. The colours seem to be well determined. E. J. Hartung gives orange and white whilst more recently, Richard Jaworski finds yellowish-orange and white. Sissy Haas notes it as a showcase pair.

Bob Argyle - Double Star Section Director

April 2015 - Galaxy of the Month

NGC 4330 in Virgo

This interactive image of NGC 4330 was provided by the Sloan Sky Survey using Aladin Sky Atlas. This finder chart should help you locate this galaxy, and a few others too.

As spring rolls around it would be remiss not to choose the galaxy of the month from the Virgo cluster. As always with such a well-known cluster most people have their favourite galaxies but for this month I have chosen the little observed edge on galaxy NGC 4330.

Situated in a nice field of galaxies NGC 4330 was first discovered by Bindon Stoney is 1852 using Lord Rosse’s 72" at Birr. It was later independently rediscovered by d’Arrest using a 15.4" refractor. The other galaxies in the field NGC 4294, 4299 and 4313 were all discovered by William Herschel so this suggests that NGC 4330 is not going to be any easy target.

The galaxy itself is a late type spiral galaxy with a small bulge that is currently falling in towards the centre of the Virgo cluster as defined by M87. Because of this it is undergoing ram stripping of its gas, a process whereby the gas in the galaxy is stripped out by the interaction with the intra-cluster medium. As such NGC 4330 would appear to be transforming from a spiral galaxy into a lenticular galaxy. NGC 4330 appears to have a bright UV tail consisting of neutral Hydrogen (HI) gas which points directly away from M87. Currently NGC 4330 only appears to have about 15% of the expected HI mass of a similar field spiral which suggests that it is well on the way to becoming a lenticular. Although it is relatively close in spatial terms to the larger spiral galaxy NGC 4313 the stellar component of NGC 4330 does not look like it has been disturbed by gravitational interaction with it.

Observationally all four galaxies NGC 4294, 4299, 4313 and 4330 should fit in the same field of view of a medium power hyper wide field (100 degree field) eyepiece. For those with larger telescopes it may be possible to pick up the very much fainter galaxy IC 3209 near NGC 4313. IC3209 was discovered visually by Frost using a 24" refractor so it should be visible to observers with dark skies and a 20" telescope. It may also be picked up by those using electronic assistance.

Interestingly NGC 4330 is not mentioned in either the NSOG or L&S so a new challenge out there.

Owen Brazell - Galaxy Section Director

Deep-Sky Observer (DSO) No 153 - Free Sample

DSO153 Cover

This free journal is DSO 153 from 2010. You can download it as a PDF file onto your computer by right clicking the link below and choosing either 'Save Target As' or 'Save Link As'...

Download DSO 153 (2MB PDF file)

Clear Skies Observing Guides (CSOG)

Courtesy of Victor van Wulfen.

Clear Skies Observing Guides Banner

Webb Deep-Sky Society member Victor van Wulfen produces the CSOG. He's recently relaunched the website with version 2.1, so now would be a good time to take a look.

The Brightest Planetary Nebulae Observing Atlas - 2nd Edition

Massimo Zecchin has just completed the 2nd Edition of an atlas of planetary nebulae observed with small apertures and from suburban locations, entitled: "The Brightest Planetary Nebulae Observing Atlas".

Massimo has kindly made the atlas is freely available in two versions, Black (for display) and White (printer friendly with the images in negative).

The 2nd Edition contains:

  • Six additional objects.
  • Data of visual magnitude, central star magnitude and object size from the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (SEC catalogue) and in a few cases from the Saguaro Astronomy Club database (SAC catalogue).
  • Calculated surficial brightness for any object (in magnitude per square arcsec).
  • Six additionaltables showing the objects sorted by magnitude, surficial brightness, size, central star mag, constellation and declination.
  • A general position map.

Either version of the atlas can be downloaded as a PDF file onto your computer by right clicking the respective image above and choosing either Save Target As or Save Link As...

Please note that the Black version is 14MB and the White version 10MB