In May, the spring constellations of Leo, Virgo and Bootes dominate the night sky. Astronomy teacher Uwe Schierhorn explains how the lion of mythology came into the sky and when, where and how Comet Johnson can be observed.
Spring brings not only warmer temperatures during the day, hopefully soon, but also the nights should become milder, making stargazing more pleasant. The day length increases thus in May further. While on 1. May the sun is 14 hours and 57 minutes above the horizon (SA 5.35 o’clock; SU 20.32 o’clock), the day lasts on 31. May already ca. 1.5 hours longer (SA 4.52 o’clock; SU 21.4 pm).
Leo, Virgo and Bootes
The evening sky is dominated in May by the spring constellations of Leo, Virgo and Bootes (Bear Keeper). The three brightest stars of these constellations Regulus, Spika and Arcturus are also called the spring triangle. In the evening we find the lion central in the southern sky. Because of its shape reminding of an iron, it can be easily found.
How the lion got to heaven
The Greeks saw in the constellation of Leo (see above) an invincible monster, the "Nemean Lion", which caused much destruction and was only slain by Hercules. Leo is also optically very conspicuous between its rather faint neighbor constellations in the spring sky, which is why also the Persians, Syrians and Babylonians already described the prominent constellation of the ecliptic. Also Ptolemy (around 100 n.Chr.) described the lion, whose representation in mythology at that time, however, included only those stars of its present torso. What today is the lion’s head in the spring sky, was for ancient observers a knife (resp. a crescent), the then tassel later became the constellation Hair of Berenice.
The stars of Leo
The main star of Leo is the star Regulus, which means "little king". With a brightness of 1m35 magnitudes it belongs to the 20 brightest stars of the sky. The next brightest lion star is Denebola, whose name comes from the Arabic and is an abbreviation of ðanab al-asad, which means "tail of the lion. The mane star Algieba (arab. Mane) is the third brightest star in Leo with 2m2 and actually the brighter part of a double star system. Zosma and Algenubi follow.
Hipparch invented the magnitude scale
The brightness scale goes back to the Babylonian astronomy, from which it was derived by the Greek Hipparcos (also Hipparch 190 – 120 B.C.).Chr.) for his star catalog. The stars were divided into six classes according to their brightness, with the brightest of the 1. size class (1m) and the just visible with the naked eye of the 6. size class (6m) were assigned. With the invention of the telescope and the objectification of observation through brightness measurements, decimals were introduced and stars were classified in more detail. This is how the negative brightness values were formed. The notation with the superscript m as "unit" and "comma" is thus historically grown. The 6. Magnitude class, however, remained the limit for the human eye.
Pull out the binoculars for comet Johnson
The bright star Arcturus (rank 2 in the brightness scale of the stars visible in our sky with 0m) belongs to the spring triangle. It can be found quickly by extending the drawbar of the "Big Dipper" in the direction of curvature and serves us as a finding aid for a relatively bright comet in May: Am 3. November 2015 discovered the astronomer Jess A. Johnson at the Catalina Sky Survey a comet, which since then carries his name beside the official catalog designation C/2015 V". This comet Johnson should reach its maximum brightness of less than 7m at the end of May. For observation a pair of binoculars or a telescope is necessary. small telescope necessary. The expected orbit of comet Johnson is shown in the following figure.
The planets in May
Of the planets Jupiter is still visible all night long. In the morning it will be replaced by the much brighter Venus, which will be visible around 4.30 o’clock rises before the sun. Saturn reaches at Venus rise only a maximum altitude of ca. 15° above the horizon in the south. You need a good view to the horizon to see the "Lord of the Rings".
The moon in May: first quarter at 3. May, full moon on 10. May; last quarter on 19. May, new moon on 25. May.