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Object of the Week November 16, 2014 - ARP 78 The Fiddlehead Galaxy and the Discordant Quasar
Object of the Week November 16, 2014 ARP 78 The Fiddlehead Galaxy and the Discordant Quasar
ARP 78, NGC 772, PGC 7525, UGC 1466, MCG +03-06-011, Fiddlehead Galaxy
Unbarred Spiral Galaxy
RA: 01h 59m 20s Dec: +19° 00’ 27”
Size: 7.2’ x 4.3’
Mag: 10.3v
Surface Brightness: 14.0
The Satellite Galaxy
NGC 770, PGC 7517, UGC 1463, MCG+03-06-010, PGC 7517
Dwarf Elliptical Galaxy
RA: 01h 59m 13s Dec: +18° 57’ 19”
Size: 1.2’ x 0.9’
Mag: 13.0v
The Discordant Quasar
[HB89]0156+187
RA: 01h 59m 21s Dec: +19° 00’ 32”
Mag: 19.4
William Herschel first observed NGC 772 in November 1785 using his 18.7” speculum mirror telescope. In his discovery notes he recorded: “Very bright, large, round, with much brighter middle, not easily resolved, 4’ in diameter.” Nearly 50 years later Admiral William Henry Smyth in The Bedford Catalog, From A Cycle of Celestial Objects (1844) recorded a similar description: “Round nebula, closely following γ (Gamma Arietis) on the neck of the Ram, where it may be fished for on a line carried from Trianguli 4 below α (Alpha) Arietis. It is large and pale, but brightens in the centre.“
Locating NGC 772 is much easier if you don’t use Admiral Smyth’s directions! Instead start at γ (Gamma) Arietis or Mesarthim, which by the way is an attractive double star, and sweep ~1.5° east-southeast. In a 3° finder field by putting γ on the western edge it will place the galaxy nearly in the center of the field of view.
NGC 772, the 78th object in Arp’s Atlas of Peculiar Galaxies, was categorized by Halton Arp as a “spiral galaxy with a small high-surface brightness companion.”
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ARP 78 is an unbarred spiral galaxy about 115 million light-years from us in the constellation Aries. Its diameter is larger than 200,000 light years, which is about twice the size of the Milky Way. The most prominent feature of the galaxy is the dominant outer spiral arm that is much brighter and much stronger than it’s other arms. The strong arm is populated with faint HII regions indicating active star formation. The other smaller and more tightly coiled arms are well formed and there are few signs of star formation in them. Several satellite galaxies are found around Arp 78 – the closest being NGC 770 a dwarf elliptical galaxy, which Arp thought to be the reason for the asymmetrical appearance of the galaxy. NGC 770 is at the same redshift as ARP 78 indicating that it is truly a companion. A faint plume fans toward two other dwarf galaxies, PGC 7493 and PGC 7509. The one dominant arm coiling around the nucleus reminded Stephen O’Meara of a fiddlehead (fern) unfolding, hence the common name The Fiddlehead Galaxy.
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In the late 1980’s, a quasar cataloged as [HB89]0156+187 was discovered near the galactic core of ARP 78. NED lists the magnitude of this quasar as 19.43. The redshift of Arp 78 is z=0.008 (115 million light years) while the redshift of the quasar is z=2.61 which would supposedly place it far behind ARP 78 at a distance of well over 11 billion light years. The discordance here is that it doesn’t make sense how this faint quasar can shine through the densest portion of a giant galaxy like ARP 78. Better observations and measurements in the future may eventually help resolve this peculiar case of redshift discordance or they may force the reexamination of extragalactic redshifts and the validity of the expanding universe.
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NGC 770, the dwarf elliptical is peculiar in its own right. Its core is rotating in the opposite direction to its outer parts. A counter-rotating core would not be unusual if the galaxy was the primary galaxy in the area, but NGC 770 is a much smaller satellite galaxy of the much larger ARP 78 galaxy.
I’ve not yet had the opportunity to observe Arp 78 or NGC 770 so I am especially interested in hearing about your observations of these peculiar galaxies. Challenge yourself with high power on the asymmetrical arm and HII regions and also try to detect the faint plumes.
“GIVE IT A GO AND LET US KNOW”
GOOD LUCK AND GREAT VIEWING!
