March Images from the Blue Mountain Vista Observatory - II
Dick Steinberg
March 13, 2010
We continue with more images from the early March run of clear, moonless nights at the BMVO. Four images in this series were presented earlier.
Near the center of the first of today's images* lies PGC54559 in Serpens, better known as Hoag's Object, a ring galaxy discovered in 1950 by astronomer Arthur Hoag, who, at first, was unsure whether it was a planetary nebula or a peculiar galaxy. It is now known to be a galaxy with a redshift of z = .043, corresponding to a recession velocity of 12700 km/sec and a distance of 180 MPc (587 Mly). The ring, about 35 arc-sec in diameter, is clearly visible in the image, its position marked by the annotations. The apparent magnitude of Hoag's object is about 16. In contemplating the formation of this object, it seems likely that some type of galactic collision must have played a role, but no nearby galaxy seems present. It also seems a bit strange that the object is perfectly circular, not elliptical as would be much more likely, a priori.
An HST image of the object is available for comparison. It is interesting to note that we may be just detecting a couple of the fainter objects (at 1 o'clock and 9 o'clock) very clearly visible in the HST image. The much more distant and consequently much redder second ring galaxy in the HST image at 2 o'clock is not visible here.
SkyMap Pro map of the field containing Hoag's object.
The supernova remnant IC443 (the Jellyfish nebula), lies near the third magnitude star Propus in Gemini, the bright orange object to the right of the center of the image.
Propus, a cool M3 star, owes its high luminosity to its large radius (about 0.6 AU). Its name means "forward foot" in Greek, derived from its position at the bottom of the western twin, Castor. Propus has evolved off the main sequence, having largely exhausted both its original hydrogen and then helium fuels, and is now entering the asymptotic giant branch of the HR diagram on its way to formation of a planetary nebula and a remnant white dwarf.
IC443, at a distance of about 5000 ly, is considered to be the remnant of a supernova explosion. Its apparent diameter of 50 arc-min corresponds to about 70 ly, consistent with an age of 10,000 years and an expansion velocity of 2000 km/sec. A finder chart for the image is shown.
A few more images:
I. M49 , a giant elliptical galaxy (right of center), one of the brightest (magnitude 8.5) of the Virgo cluster. In the northeast corner (upper left) of the image note the beautiful spiral NGC 4535, notable in that it is one of the 18 galaxies whose Cepheid variables were carefully measured in a Hubble project to extend the extragalactic distance scale. Its distance was measured to be 16.0 +/- 1.9 Mpc.
II. M61 , a face-on spiral galaxy in Virgo with angular arms.
III. NGC2174 , an H II emission nebula near the outstretched right hand of Orion, 2 degrees southwest of Propus.
IV. NGC1909, the amusing Witchhead nebula in Eridanus, 2 degrees northwest of Rigel. (South is up in this image).
object finder charts from SkyMap Pro: M49, M61, NGC2174, NGC1909
Dick
*Please note that the images are 3000 x 2000 pixels in size and require a magnification of at least 2 (4 preferred) to render maximum detail on a typical monitor. Firefox add-on Image Zoom is recommended.
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current setup:
Televue NP101is @ f/5.4 FL 544mm -- Paramount ME -- Orion SS Pro v1 -- MoonLite CFL stepper motor focuser controlled by FocusMax -- acquisition and processing with MaxIm DL v5 -- automated acquisition with CCD Commander v1.6 -- all images acquired remotely using Radmin v3.4 -- 5 min subs unguided -- 2.95 arcsec/pixel
