Morning sky

Under morning sky astronomers understand, natural and astronomers the sight of the starry sky of the respective season in the hours before sunrise .

In contrast to the evening sky , the term is used less frequently in common parlance because outside the winter months fewer people raise their gaze to the sky before dawn . Morning sky observation is also more arduous, because the air during the night cools down by a few degrees compared to the evening and often thick dew falls, from which telescopes and other devices - especially electronic ones - have to be protected. The dew also makes the environment look colder. When observed, they offer some differences to the evening sky.

Before dawn it is usually colder and wetter, but often less cloudy. Because in Central Europe, cloud cover occurs on many clear afternoons and often only dissolves in the second half of the night.

Eastern morning sky in Egypt on the day of the heliacal rising of Sirius (right). Mercury and Venus as morning stars above the sun , Orion above right, the Big Dipper on the left. After sunrise , the stars (except for Venus) are no longer visible to the public.

 Aktuell: Planetenparade im März 2020

The brightest outer planets Jupiter, Mars and Saturn are 6–10 ° apart, which only happens every 20 years! The three are best seen around 5 a.m. (sunrise is on March 20th at around 6 a.m.).
Mars (1.1 mag) overtook on March 20th first Jupiter, on March 31st also Saturn. On March 18 the moon moves only 1 ° south past Mars and Jupiter, on the 19th at 1 o'clock past Saturn.

Interesting in the morning sky

The early morning hours are of particular interest to astronomy ,

to avoid annoying moonlight (when the moon is waxing),
to observe the waning moon in half or narrow phase (crescent moon), where its mountains and craters are illuminated from the east (instead of from the west, as with increasing phase);
for observing the inner planets Mercury or Venus when they are the morning star ,
for other planets if they are west of the sun
to avoid the greater unrest in the evening sky (rapid cooling of air and instruments);
for long exposure times in astrophotography (short nights in summer!) or
for the Messier marathon (in which all Messier objects are observed in one night);
for most meteor streams (shooting star swarms ), which in the morning - on the "front" of the earth's rotation - have higher fall rates and initial speeds (especially the Quadrantids in January, the Perseids in August and the Geminids in December),

for heliacal rising of bright stars (see picture above)

with comets that are only visible in the morning or newly discovered novae ,

if you want to see objects in the winter sky again at more pleasant temperatures after summer

and for special events such as lunar eclipses , planetary constellations or rare star occultations .

Since the earth rotates around 15 ° to the east every hour, the term “morning sky” cannot be clearly defined. The visible half of the sky depends on the geographical latitude and moreover shifts by almost 1 degree every day. Because the earth does not rotate in 24 hours, but 4 minutes faster, the so-called sidereal day . Our time is of course based on the sun , which in turn moves every year - as a mirror image of the earth year - through the 12 constellations of the zodiac (see ecliptic ).

Seasonal change

As an example of the dependence of the view of the sky on the date and time , two star maps are placed side by side, showing the morning sky for Frankfurt am Main at 4 a.m. CET in autumn (beginning of October) and in winter (beginning of January).
The two pictures are also valid 1 month later if you choose 2 a.m. as the comparison time for the beginning of November or February:

Morning autumn sky over Frankfurt: at the beginning of October 4:00 am CET , at the end of October already at 2:00 am CET. The sight corresponds to the evening winter sky .

Morning winter sky over Frankfurt: at the beginning of January 4 hours CET , or at the end of January at 2 hours CET. The sight corresponds to the evening spring sky .

When comparing the two celestial sections, only the northern constellations - the " circumpolar stars " around the celestial north pole or polar star - are the same, but rotated by 90 ° (6 hours of the earth's rotation or a quarter of the earth's orbit). On the other hand, this means that the two sky sections not only correspond to the morning sky in autumn and winter, but can also be seen 6 hours earlier after 3 months - i.e. in the evening.

Winter and summer sky

In the early morning in autumn the big winter hexagon slowly rises in the east and southeast - consisting of the 6 brightest stars of the constellations Carter, Taurus, Orion, Big or Small Dog and Gemini. By the beginning of winter , this striking hexagon - named after the typical view of the sky on winter evenings - had shifted to the western sky and soon went under (except for the star Capella (α in the carter), which is circumpolar).

The same applies to the evening summer sky , which with its typical summer triangle can be seen in the morning in the spring.

The seasonal change in the starry sky can also be seen in the most famous constellation, the Big Dipper : On the cool autumn morning we have to look for it to the right of the North Star (in the northeast), while its counterpart, the big W of Cassiopeia, is on the left (in the northwest) . During the autumn, the Big Dipper climbs a little higher every week until it is over our heads at the beginning of winter. It seems just as steep to us in the evening sky in spring - and because this position is unfamiliar for less experienced sky viewers, some people cannot find the constellation or only after a long search.

More natural phenomena

In addition to the purely astronomical aspects, morning observations of the sky also give you the opportunity to do other nature observations almost "on the side":

Phenomena of meteorology , e.g. B. in the dew. It is noticeable on the telescope much earlier than in the great outdoors, often as early as midnight. That is why telescopes are usually equipped with a dew cap to prevent excessive fogging on the optics and the metal tube .

Otherwise, the dew usually only falls in the morning hours, when the night-time cooling of the air falls below the dew point and the atmospheric water vapor condenses.

The formation of ground fog (albeit unpleasant) can often be observed directly . If a hobby astronomer prefers the open field to a location in the city, he is sometimes exactly up to his knees in the fog at dawn.

Anyone who observes until dawn for the first time will remember the physical phenomena. Suddenly you can feel your veins start to tingle. This hormonal phenomenon also begins when you have not noticed the approaching dawn while observing through the telescope.

The so-called bird watch . The first timidly singing bird falls to a z. B. in insomnia, but how varied the onset of the other bird calls is, not everyone knows.

News for 2015/16

Venus is the morning star from September until around March 2016
Mercury clear-eyed only 2 × briefly (beginning of February, end of October)
Jupiter, however, since October; in November near Venus as a "double morning star"

Heaven of the 4 seasons

literature

The sky year . Sun, moon and stars in the course of the year . Franckh-Kosmos-Verlag, Stuttgart 2015, ISBN 978-3-440-13097-1 (published annually)
Austrian sky calendar, Astroverein Wien (published annually)
Stars and Space , "Objects of the Month" section. Spektrum-Verlag, monthly
A. Rigutti, E. Albisetti: The great book of astronomy , p. 86–97 (star maps by season). Kaiser-Verlag, Florence and Klagenfurt 2004
Rudolf Brandt et al .: Sky Observations with Binoculars - An Introduction for Star Friends . German publisher, 2006
Current star map (for computer time) , Himmelsvorschau.org

Web links

Wiktionary: Morgenhimmel - explanations of meanings, word origins, synonyms, translations

Monthly overview December 2010 and soon in early 2011
Current star map (for computer time)