By Brian Cuthbertson
This is a busy season for everyone; the holidays and related activities tend to crowd out time for observing. But of course the celestial parade continues unabated, and the night sky continues to offer up its own seasonal presents. Though they can’t be wrapped or put under a tree, they’re still worth checking out if you have the time. So if the sky is clear, the weather is tolerable,the shopping is taken care of, and a holiday party doesn’t take priority, consider a quick visit to a dark site to see those celestial gifts that always keep on giving. Incidentally, if you like to gamble but Las Vegas isn’t your style, you can always visit Menkib; details below. Enjoy!
California Nebula rating EASY
Emission nebula in Perseus
RA 04h 03.4m Dec +36d 25.3′ (2000)
Magnitude 5 (integrated)
Located in southern Perseus about 5 degrees north of 3rd magnitude Atik (Zeta Persei), the stately California Nebula (NGC 1499) may be the largest visual nebula you’ve never seen. Shaped impressively like the outline of the Golden State, the nebula was well known photographically, but not visually, before the age of deep sky filters. Visually, it was considered extremely difficult. But these days, with an OIII, UHC, or H-Beta filter in your hand, it can be seen with your unaided eye.
Which is not to say that it’s easy: although the total integrated visual magnitude of the California Nebula is about 5, the nebula is very large. That 5th magnitude brightness is spread over an area larger than 2.5 degrees. In general, even with a filter, it is best detected with small apertures that provide a field of view large enough to hold the entire nebula. Your eye, binoculars, and small fast rich field scopes may fill that bill, but larger scopes tend to lose out here.
The California Nebula is a glowing cloud of hydrogen gas, pumped into an energetic emission state by the blue 4th-magnitude star Menkib (Xi Persei), one of the hottest and intrinsically brightest stars visible to the naked eye. When the excited hydrogen drops to a lower energy state, it emits red light with the characteristic “hydrogen alpha” wavelength. But physical conditions in the nebula also result in strong emission of blue-green “hydrogen beta” light, a situation much like that in Orion’s Horsehead Nebula. Hence the utility of H-Beta filters for observing both these objects.
By galactic standards, the California Nebula is a relatively close neighbor, only 1500 light-years away in the Milky Way’s Orion arm, the same arm we inhabit. Lengthwise, it stretches about 100 light-years. Menkib, the illuminating star, sits on the western edge of the nebula. But geographically speaking, it lies just to the east, barely across the border near Reno, Nevada. So now you know why Reno is a hot spot.
Oh, and sorry folks – an internet search (correct me if I’m wrong) turns up no evidence of a Texas Nebula; so California seems to have us celestially beat on this one.
NGC 188 rating MEDIUM
open cluster in Cepheus
RA 0h 44.6m Dec +85d 20.4′ (2000)
Magnitude 8.1; dia 14′
NGC 188 stands out as an interesting open star cluster for a couple of reasons. First, it’s the most northerly cluster in the sky – it lies just 4 degrees from the north celestial pole, in a region that’s otherwise the exclusive domain of faint stars and galaxies. Consequently you can study it at your leisure, since it stays above the horizon year-round, even down here in Texas.
Second, with an age of about 5 billion years, NGC 188 is one of the oldest open clusters known; most open clusters dissipate before getting this old. Agewise it comes in third behind open clusters Melotte 66 in Puppis and NGC 6791 in Lyra, both more than 6 billion years old. All 3 of these open clusters are older than our solar system, a relative youngster at 4.5 billion years.
NGC 188 contains about 150 stars, most of which are fainter than 13th magnitude. However, it can be seen even with a small 2.4-inch refractor as a slightly grainy unresolved faint patch among several 8-10th magnitude field stars. In a 6- or 8-inch scope at low power it appears a large, dim luminous spot with just a few of the members glowing individually. You need a 10-inch scope to begin to distinguish a dim swarm of about 50 stars. In bigger scopes the cluster’s large size makes it less conspicuous, though you can see all the stars to 13th magnitude and fainter with no unresolved haze.
Incidentally, if you’re a fan of Patrick Moore’s “Caldwell” list of 109 notable non-Messier objects, you may already know of NGC 188 as the first object in that list – Caldwell 1.
NGC 1309 rating HARD
spiral galaxy in Eridanus
RA 03h 22.1m Dec -15d 24.0′ (2000)
Magnitude 11.5
Located in the center of a big westward loop of the celestial river, Eridanus, NGC 1309 is a beautiful face-on pinwheel spiral, at least in large scope images. One of the dramatic aspects of this galaxy is the large number of background galaxies visible in these images both in and around its spiral arms. It’s worthwhile to find an internet Hubble image of the galaxy just to checkout all these background systems.
For visual observers, the galaxy is fairly bright in a 10-inch class scope, with a faint stellar nucleus visible inside a smooth 1.5′ diameter halo. As an added incentive to occasionally take a look, NGC 1309 has hosted at least two recent supernovae(SN): type Ia SN 2002fk which reached a maximum magnitude of ~13.0, and rare type Iax SN 2012Z, which may have left behind a piece of the white dwarf that caused it.
NGC 1309 sits about 120 million light-years away, and spans about 75,000 light-years, or roughly 3/4 the diameter of our Milky Way. It’s one of a nearby loose group of about 200 galaxies with a mean distance of 75 million light-years in the direction of Eridanus. The group, sometimes called the Eridanus Cloud, covers the sky from RA 3h to 4.5h and from -10 to -30 degrees Declination; its brightest members include NGC 1232 (another beautiful face-on spiral) and NGC 1407 (a large elliptical). About 70% of the members are spirals and irregulars; elliptical and lenticular galaxies make up the rest. The whole cloud is thought to be slowly condensing into a real cluster whose ultimate size will be somewhere between that of the Ursa Major galaxy group and the Virgo cluster. But don’t hold your breath waiting to find out.
