Observing Calendars

April Observing Calendar   February and March were devoted to the constellations Orion, Cancer, and the Gemini Twins. This month Leo, The Lion, is climbing up the ecliptic from the east and Ursa Major, The Big Dipper, is coming into easy view. Find Regulus in Leo. Locate Sirius the bright star almost due south in the constellation Canis Major (see March Calendar). Scan east at the same elevation and about half-way between Sirius and the Big Dipper is a bright star. The moon may be just east of it. This is Regulus, the marker star in Leo. It is sometimes referred to as "The Little King" or "The Lion's Heart." Leo is inclined almost perpendicular to the horizon facing the zenith (a point directly overhead). Visualize Regulus as the lower chest of the lion and you will see the curved outline of the Lion's head north and east of Regulus. Scan toward the horizon and you see the three stars forming a right triangle. These make up the hind quarters with the lowest star, Denebola, forming the tail. Now scan back toward Regulus and the right-hand star in the triangle. This is Chort, or Chertan. Notice the two fainter stars below and to the right, the lower one being almost parallel with Denebola and the horizon. Carefully scan from Chort to the first star on the "leg." About halfway, you should come to two faint, fuzzy, elongated smudges. These are M65 and M66 respectively M656 (Use BACK button on Browser to return). These spiral galaxies are about 29 million light-years away. M65 is about 60,000 light-years in diameter, and M66 is about 50,000 light-years in diameter. M65 can be detected with binoculars. Telescopes of eight-inch diameter and above will begin to resolve some detail. These galaxies are separated by about a half degree and so can be seen in the same field of view. About one-half degree north is an edge-on spiral galaxy which may also be seen in the same field of view. These three galaxies are often referred to as the Leo Trio. Split the distance between Chort and Regulus. Scan toward the horizon about two degrees and three more galaxies may be seen in eight-inch or larger telescopes. These are M105, M96, and M95. All are about 29 million light-years distant. Now let,s move to the Big Dipper. Remember this is Ursa Major, The Big Bear. The bowl forms the hind quarter with the handle as the tail. The head is the brighter stars up from the bowl, and the legs are pointing toward you. Start with the star topmost and furthest from you in the bowl. Going clockwise around the bowl are Dubhe, Merak, Phad, and Megrez. If you did this correctly, you are at the star connecting the bowl and the handle. Move down the handle: first Megrez, then Alioth, Mizar (at the crook to the east) then Alkaid. You can verify Mizar since it is a fine double, or binary star. Extend an imaginary line from Phad through Dubhe. Note the length of the line. Now continue in the same direction and about the same distance. Scan carefully to the left (north) and you should come to two galaxies, M81 and M82. M81 is larger and appears oval. M82 is smaller and appears cigar shaped. M81 & M82 Both are about 11.4 million light-years away. M82 is estimated to contain 50 billion suns, about one-fifth the mass of M81. Now move to Merak, the top star nearest you in the bowl. Draw an imaginary line to Phad, the star at the bottom of the bowl. Carefully scan down this imaginary line. About one-fifth the way toward Phad,and slightly to the east you will come to M108, another spiral galaxy seen edge-on. Its distance is about 35 million light-years. Further down and perhaps in the same field of view is M97, the Owl Nebula. This is a large planetary nebula named for the two dark circular areas in its center, giving it the appearance of an owl's eyes. Continue along the same imaginary line to Phad. Move just past Phad and M109 should appear. You may have to move Phad out of the field of view so its brightness doesn't obscure the dim glow of this spiral Galaxy about 38 million light-years away. Follow the stars down the handle...Megrez at the bowl, then Alioth, then Mizar. Note the distance between Alioth and Mizar. Now move to the last star in the handle, Alkaid. Draw an imaginary line from Mizar to Alkaid. Now draw a perpendicular line east from Alkaid. Scan east about the same distance as you measured between Alioth and Mizar. You should come to M51, the Whirlpool Galaxy. This beautiful object appears to be a "close encounter of the cosmic kind" since it looks like two galaxies are merging. NGC5195, the smaller galaxy, is actually nearer to us. The most prevalent view is that these galaxies past near enough to each other that the larger one robbed the smaller galaxy of some of its stars resulting in the bridge we see between them. Merging galaxies is not an unusual phenomenon. M51 is a face-on spiral galaxy and is similar in size and appearance to the Milky-Way Galaxy. It is about 35 million light-years away. Visualize an equilateral triangle pointing west from Mizar and Alkaid. You should find another spectacular face-on spiral galaxy M101. All of these objects in Ursa Major are visible through small telescopes and binoculars.