Two extraordinary astronomical events await us in May of this year: Mercury passes in front of the Sun and Mars comes close to Earth.
Stuttgart – In mid-April, Mercury, which is close to the Sun, briefly appeared in the western sky at dusk. Already on Monday, 9. May the nimble planet overtakes Earth on its inner orbit. This is usually nothing special. Because every four months Mercury overtakes the Earth. But this time, Mercury’s orbit, tilted by seven degrees, is such that the Benjamin of planets passes in front of the solar disk as a dark dot. Such an event is called a transit or passage of Mercury.
Mercury transits are even rarer than solar and lunar eclipses. In the 21. Century Mercury steps only fourteen times before the sun. Not all Mercury transits can be observed from Central Europe. Because some of them take place when the sun has already set in our region. The last Mercury transit visible from Germany occurred on 7. May 2003. Should the passage of Mercury on 9. If we miss the first Mercury transits on May 11 because of cloudy skies, we will not be able to see them until May 11. November 2019 and thereafter on 13. November 2032 an opportunity to observe Mercury as a dark dot in front of the sun.
Cosmic shadow play
The cosmic shadow play begins in Stuttgart and surroundings at 13.12 o’clock and 13 seconds daylight saving time with the entry of Mercury at the eastern edge of the sun. The shortest distance from the center of the solar disk will be around 16.56 o’clock and 25 seconds is reached, with Mercury a little more than five arc minutes away from the center of the solar disk. The transit of Mercury ends with the exit of Mercury at 20.40 o’clock, 33 seconds. Mercury’s disk is tiny, measuring only 158 kilometers across. Part of the apparent solar diameter. Therefore the transit is not visible with naked eyes.
To see Mercury as a dark spot in front of the sun, you need a telescope with a stable tripod and at least fifty times magnification. Without suitable protective measures like lens filters or projection equipment you must not look into the sun with binoculars or telescope under any circumstances! It is best to visit an observatory to watch this celestial spectacle. The exact times of beginning and end of the transit of Mercury depend on the location, but differ within Germany only by a few seconds.
In May Mars dominates the night sky as a bright, conspicuous star. Only Jupiter is still a little brighter than Mars. The shiny whitish giant planet can be seen high in the southwestern sky in the constellation Leo during the first half of the night. Earth reaches its closest distance from reddish Mars at the end of May. At 22. Mars and the sun are opposite each other on the terrestrial firmament, the expert speaks of opposition. When the sun sets, Mars appears in the southeast. At midnight it can be seen in the southern sky and in the morning it sets in the southwest. Our neighboring planet is in the constellation of Scorpio, whose main star Antares also has a reddish glow. Antares means something like "mars-like star". It was sometimes confused with Mars, because it is also in the zodiac. Now one can compare well both celestial bodies with each other.
Shortest distance to Mars
Due to the elliptical orbits of Earth and Mars, the closest distance to our outer neighbor planet will be reached only one week after the opposition date. On 30. May only 75 million kilometers separate us from Mars, which is about half the distance from the Earth to the Sun. The light or a radio signal of a Mars rover is then four minutes and eleven seconds on the way to earth. With a diameter of just under 6800 kilometers, Mars is only half as large like the earth. Its mass is only eleven percent of the Earth’s mass. A Martian day is only forty minutes longer than an earthly day. Since the Mars axis is inclined like that of the earth by 25 degrees to its orbit, also on Mars seasons occur. They last however twice as long as the terrestrial ones. Because Mars needs almost two years for one revolution around the sun. On 4. July 2016 will mark the beginning of spring in the Martian northern hemisphere.
Saturn in the constellation of the serpent bearer gradually becomes the planet of the whole night. The yellowish ring planet rises at the beginning of the month half an hour before midnight, but at the end of May already a quarter of an hour after 9 p.m., i.e. shortly before sunset. Venus has retreated from the morning sky and stays in the daytime sky. It remains unobservable below the horizon at night. At the beginning of June Venus will catch up with the sun in the constellation Taurus. Mars receives on 21. Visit of the full moon. One day later the moon passes north of Saturn.
Shooting stars at the end of May
From the beginning of the month until the end of May the shooting stars of the Aquarid stream are to be expected. Its radiant point is in the constellation of Aquarius, hence its name. They are fast meteors, entering the Earth’s atmosphere at 65 kilometers per second. The peak of the Aquarid activity will be on 6. May at new moon reaches, whereby up to sixty shooting stars per hour light up. Since no moonlight disturbs, this time the observing conditions are especially favorable. The Aquarids are fragments of Halley’s comet. The best observation time are the hours starting from 3 o’clock in the morning.
New moon occurs on 6. at 21:30. Few hours before the moon comes with 357 830 kilometers near the earth, which leads again to high spring tides with maximum tidal range also of the solid earth surface. Full moon will be on 21. reached at 23:14. As the moon moves in the night of 18. on 19. with 405 930 kilometers in earth distance is located, one sees this time the smallest full moon disk of the year 2016. It stays in front of the Scorpio starry backdrop.
Spring triangle in the south
The celestial chariot stands high above our heads when viewing the starry sky in the evening after dark. Easily you can make out the spring triangle, now visible high in the south. It is composed of Regulus, Arcturus and Spica, the three main stars of the constellations Leo, Bootes and Virgo, respectively. A bright star shines in Leo, the giant planet Jupiter mentioned earlier. Scorpio is rising in the southwest right now, with red-yellow Mars shining brightly in it. The sun almost reaches the peak of its annual orbit. Their midday altitudes increase by nearly seven degrees, and the length of the day increases by one hour and 17 minutes in Stuttgart. On 14. the sun enters the constellation Taurus and passes the Golden Gate of the ecliptic at the end of May. On 20. May it changes into the zodiac sign of the twins. It does not reach the constellation Gemini until 21. June at 10 am.