By Brian Cuthbertson
Lions and hydras and bears, oh my! The springtime sky could almost make a great setting for Judy Garland’s famous line in “The Wizard of Oz.” Well, except of course for that sea serpent. Leo, the Lion, dominates the evening sky this time of year, with Hydra, the Sea Serpent, wrapping across the sky to the south. And of course Ursa Major, the Great Bear, is well placed up north. It’s a perfect time to get out and show your munchkins the celestial zoo above our heads. There’s lots to see as always, including the samples below. So get the heck out of Oz on any convenient yellow brick road, find a nice dark sky, and enjoy!
Zeta Hydrae rating EASY
Head of Hydra
RA 08h 55.4m Dec +05d 56.6′ (2000)
Magnitude 3.1
Hydra, the sea serpent, is the largest of the 88 modern constellations, as well as one of the original 48 constellations listed by Ptolemy. Covering over 1300 square degrees, Hydra literally leads us from winter to summer across the spring sky. It begins at the western borders of Canis Minor and Monoceros in the winter Milky Way. From there Hydra snakes eastward, south of Sextans, Crater, Corvus, Virgo, and Libra. It eventually ends just west of Scorpius, which heralds summer’s Milky Way.
Hydra’s western winter end is marked by its “head,” which lies about 15 degrees due east of Procyon (Alpha CMi). The head is a roughly circular asterism of 5 naked-eye stars over 4 degrees in diameter, conspicuous in the general emptiness of the immediate area. At magnitude 3.1, Zeta Hydrae is the head’s brightest star. Zeta is a K0 giant about 220 light years distant. It marks the eastern “neck,” where the serpent’s first body segment begins, extending 6 degrees ESE to Theta Hya. From Zeta going clockwise around the head, the other stars are Epsilon, Delta, Sigma and Eta. Of these, Epsilon is 3rd magnitude like Zeta; the others are all 4th.
Epsilon is an outstanding example of a multiple star system. 140 light years distant, it has 4 visible components with a 5th known to exist. Components A and B (magnitudes 3.7 and 4.8) are a close pair discovered by Schiaparelli in 1888. A-B is a rapid binary with a 15.3-year period and average separation of only 0.2 arcseconds – definitely not a binary for your typical amateur scope! Component C, a 7.8 magnitude F7 dwarf star, orbits A-B with a 650-year period at 3.1″. Component D, a K0 dwarf, lies 19.3″ from A-B.
Finally, of the other stars in Hydra’s head, Eta is notable as a Beta Cephei variable. Not to be confused with Cepheid variable stars, Beta Cephei variables are aging blue giant stars of spectral type B0-B3 which pulsate slightly with periods of a few hours. Their point of maximum brightness roughly matches the maximum contraction of the star. For its part, Eta is type B3 and varies from magnitude 4.27 to 4.33 over a period of 4 hours. Now that’s a good definition of slightly! So don’t bother trying to “catch a max” unless you have a photometer.
NGC 3115 rating: MEDIUM
Edge-on galaxy in Sextans
RA 10h 05.2m Dec -07d 43.0′ (2000)
Magnitude 9.2
Nicknamed the “Spindle Galaxy,” NGC 3115 is one of the feature attractions of the little constellation of Sextans, which lies directly south of Regulus in Leo. Located about 32 million light-years away, the galaxy is notable for its unusually high surface brightness, which withstands fairly high powers. It appears to the eye in amateur telescopes much as it does in photographic and CCD images. Its apparent length grows from about 3′ in 3-inch scopes to 5′ in 12-inch scopes. Its edges are also notably sharp. In any scope, its disk remains featureless, without a hint of dust or spiral arms.
NGC 3115 is usually classed as a lenticular (S0) galaxy because it contains a disk and a central bulge of stars, but without a detectable spiral pattern. Hubble Space Telescope velocity studies of the galaxy’s innermost regions find stars whirling around the core at nearly 300 km/second, suggesting that it hosts a 2-billion-solar-mass central black hole. This makes NGC 3115 the nearest billion-solar-mass black hole to Earth.
Discovered in 1787 by William Herschel, NGC 3115 is actually one of two galaxies nicknamed the “Spindle Galaxy”; the other is NGC 5866 in Draco. Like NGC 3115, NGC 5866 is also a lenticular galaxy seen almost edge-on, but is slightly dimmer (9.9) and slightly farther away (40 MLY).
Despite its brightness, no supernova has yet been seen in NGC 3115. So get out that scope, and be the first on your block to find one.
NGC 3067 rating HARD
Spiral galaxy in Leo
RA 09h 58.3m Dec +32d 22.7′ (2000)
Magnitude 11.7
Look for NGC 3067 in extreme northern Leo, just south of the Leo Minor border. The galaxy is just visible in a 6-inch with a star-like center. In a 10-inch scope it’s a circular spot 1.5′ in diameter with a faintly mottled core.
NGC 3067 is notable as the first published case of a foreground galaxy with what at least appears to be a bridge of matter connecting it to a quasar, 3C 232 in this case. NGC 3067 has a redshift of only 0.0049 and is only 95 million LY distant. 3C 232, a strong radio source only 2′ north, is 100 times farther away IF we believe its redshift of 0.5303, which implies a 9 billion LY distance.
The 3C 323/NGC 3067 pair is one of 5 known similar QSO/galaxy pairs. If you’re interested in such oddities, the other pairs include (1) quasar PKS 2020-370, 20″ from Klemola 31, a spiral in a close group of 6 galaxies; (2) quasar 0446-208, 13″ from a probable S0 galaxy in the rich Abell galaxy cluster A514; (3) quasar 1327-206, 38″ from galaxy 1327-2041; (4) quasar PHL 1226, 55″ from galaxy IC 1746. Whatever you may think about such systems, they all demonstrate the quirkiness of the universe.
