The Star Book: Stargazing throughout the seasons in the Northern Hemisphere. Peter Grego

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       Cep / Cephei

       Highest at midnight: late February

      Cepheus contains several reasonably bright stars. Among the stellar delights of Cepheus is Beta Cep, a double star of magnitudes 3.2 and 7.9 that can be resolved through a small telescope. Beta Cep is a variable star, a blue giant whose brightness fluctuates by around one tenth of a magnitude over a period of just a few hours. Another variable, which is also a nice double, is Delta Cep. The prototype of the Cepheid variables. This is a pulsating yellow supergiant that varies between magnitudes 3.5 and 4.4 in a period of five days nine hours. Delta’s companion is a magnitude 6.3 blue star, and the pair is easy to separate through a small telescope.

      Mu Cep is a red supergiant whose striking colour has earned it the nickname of the Garnet Star. Binoculars will show its ruddy hue to good effect. The star is also variable, fluctuating between magnitudes 3.4 and 5.1 over a period of two to two and a half years. Mu Cep is one of the biggest stars visible with the unaided eye – if placed in the position of the Sun, the surface of its enormous bloated sphere would extend almost out to the orbit of Saturn.

      Xi Cep is a double star comprising a magnitude 4.4 blue star and a magnitude 6.5 orange giant, easily resolvable through a small telescope.

      T Cep, a red Mira-type variable star, has a period of more than a year. At its maximum brightness the star just pops into the range of the unaided eye, shining at magnitude 5.2.

      An extension of the Milky Way nudges into the southern part of Cepheus, and a couple of lovely open star clusters can be found in this vicinity – IC 1396 and NGC 7160 – both delightful to view through a 150mm telescope. IC 1396 is embedded within a sizeable patch of nebulosity; it is also known as the Elephant’s Trunk Nebula because of a prominent dark sinuous dust lane, which is visible on photographs. Large binoculars will reveal IC 1396 as a misty patch. NGC 7160 is a small, compact star cluster; around 30 of its stars are visible through a 200mm telescope, half a dozen of the brighter ones standing out from the rest.

       The Garnet Star in Cepheus, observed through a 100mm refractor by the author.

       Double star Delta Cephei.

       The Elephant’s Trunk Nebula in Cepheus, imaged through an 80mm refractor with an astronomical CCD camera (filters used).

       Ursa Major

       UMa / Ursae Majoris

       Highest at midnight: early March

      Seven of the brightest stars within Ursa Major make up an asterism variously called the Plough or the Big Dipper. While this asterism itself doesn’t much look like a bear, a little time spent in tracing the traditional outline comprising the remainder of the constellation’s bright stars will convince any stargazer that the ancients who named it had an extremely good eye for form.

      The two front stars of the Plough, Alpha UMa (Dubhe) and Beta UMa (Merak) are known as the Pointers, since an imaginary line extending from them leads to Polaris and the north celestial pole. Zeta UMa (Mizar), the second star of the Plough’s handle, has a fainter magnitude 4 partner, 80 UMa (Alcor), which is visible with the unaided eye. Mizar itself is a close double star, with components of magnitudes 2.2 and 3.8, separable with a small telescope.

      A pair of galaxies bright enough to be seen through binoculars, Bode’s Galaxy (M81) and the Cigar Galaxy (M82) lie in the far north. Just half a degree apart, the pair is visible in the same low-power telescopic field. While M82 is almost edge-on to us, M81 is tilted at less of an angle. Some ten million light years distant, these galaxies are interacting with each other. On the other side of the constellation, the face-on spiral galaxy M101 is visible through binoculars as a circular smudge, and appears mottled through a 200mm telescope.

      The Owl Nebula (M97), a faint planetary nebula, appears as a pale disk about twice the diameter of Jupiter through a 150mm telescope. The dark eyes of the owl, so obvious in many images, are rather elusive and require at least a 250mm telescope to discern. M108, a bright, sizeable and nearly edge-on galaxy, can fit into the same low-power telescopic СКАЧАТЬ