A whole night under the stars in January

A whole night under the stars in January

This accelerated video was taken in the International Dark Sky Reserve of the Cévennes while throughout the night from 31 December to 1 st January. It summarizes more than thirteen hours of night in three minutes and allows you to admire the race of the stars above the Lake of Pises. In a sky of remarkable purity, the brightness of the lunar crescent is not enough to hide the milky strip of the Milky Way and the stars of the Triangle of summer – Vega, Deneb and Altaïr – which dive towards the western horizon. 

The brightest point under the Moon is the planet Venus. The partially icy surface of the lake reflects the Venusian and lunar radiance at the start of the night, then it is the turn of the brightest stars to reflect on this imperfect mirror which magnifies their color; spot the splendid bluish trace projected by Rigel and Sirius before bedtime (2:15). After the moon leaves, the large Andromeda galaxy appears at the top of the field in the middle of the night, soon followed by the star cluster of the Pleiades, then comes the proud stars of Taurus, Orion and the Big Dog. Less luminous than its summer part, the winter Milky Way overlooks Orion and falls towards the horizon until dawn. 

A few shooting stars are visible over the hours, but most of the light lines are left by planes or satellites. At the start of the sequence, the lunar radiance is so intense that it causes the appearance of two artefacts opposite the field: a long green reflection and a large, dimly-lit arc. In the distance, there are a few bright flashes that betray the movements of observers from the Pisa astronomical observatory throughout the night. 

The sound was recorded on site: only the sound of the water flowing over the spillway of the lake diminished the absolute silence of this long winter night. Technique: accelerated video taken with a Sony Alpha 7s camera and a 14-24 mm Nikon lens used at 14 mm and diaphragm at 3; each exposure lasts 15 seconds at ISO 4,000 and video links more than 2,700 exposures between 6:20 p.m. and 7:30 a.m.

Winter nightsfully released are rare and you have to know how to taste them like a piece of fresh bread, right down to the last crumb! I invite you to follow me during New Year’s Eve, which I spent in the Cévennes International Dark Sky Reserve under a celestial vault populated with crisp stellar bursts. 

The Moon is the most dazzling star in the evening for a few more days, then it will gradually slide towards the second half of the night after the full moon of the 10 and will leave the foreground to Venus. The position of the second planet in the Solar System is more and more favorable in the evening sky and its brightness continues to grow. Venus is visible far above the southwest horizon just after sunset; when you know where to look for it, it is even possible to spot it in the blue afternoon sky. This month, you can use its conjunction with the crescent moon at the end of the month to help you spot it in broad daylight (see later in this post).

Towards the end of twilight, less than an hour and a half after the departure of the solar disc, you will notice in the west, on the right of Venus, the three stars which delimit the Triangle of summer: Véga, Deneb and Altaïr . 

A little later, and when the lunar glow is less present, a site protected from artificial lights will allow you to distinguish the Milky Way between these beautiful stars. Over the course of the evening, Altaïr and Véga go to bed, but if you live at more than 45 ° north latitude, Deneb descends to the northern horizon and grazes before going up: it is circumpolar, that is to say that she never goes to bed throughout the year. It is necessary to be at more than 52 ° of north latitude so that Véga also becomes circumpolar.

Image extracted from the video and showing the winter sky towards the end of twilight in January over Lac des Pises (Cévennes National Park). The dazzling lunar glow causes the appearance of a white arc and a green reflection on the objective lenses opposite the field. Near the horizon, Venus is reflected on the frozen crust of the lake. On the right, the Milky Way glows delicately above the Pisa astronomical observatory.
© Guillaume Cannat

Turning your back on the Summer Triangle at the end of twilight and looking east, you will easily notice the three aligned stars of the Orion belt because they are bright enough to be visible to the naked eye in the city despite the light pollution – still avoid observing under a lamppost! Around this trio that we often nicknamed the Three Kings, the stars Betelgeuse, Bellatrix, Rigel and Saiph draw a vast parallelogram. Betelgeuse is usually one of the brightest stars in the sky, but it is also a variable star and it is currently near its minimum brightness so that its neighbor Aldébaran du Taurus is more resplendent at the beginning of ‘year.

The arms of Orion enlarge this essential figure of the winter sky: in one hand, this hunter holds a club which rises towards Gemini, in the other he brandishes a shield or the skin of a beast in front of the bull’s muzzle; use the cards in this post to identify these stars and celestial figures. Later in the evening, when Orion walks above the southern horizon, it is easy to spot on his left and a little closer to the horizon the dazzling radiance of Sirius of the Big Dog, the most star brilliant of the celestial sphere, which the atmospheric turbulence makes sharply sparkle.

Betelgeuse, Sirius and Procyon (Small Dog) define the Winter Triangle. Replace Betelgeuse by Rigel and add Pollux of Gemini, Capella du Cocher and Aldébaran du Taur to draw the huge Winter Hexagon that I presented to you in this post. Even if you live under a sky degraded by light pollution, the very bright stars that border the Triangle and the Hexagon are generally visible to the naked eye. Devote an outing under a good quality sky to a more complete discovery of the winter constellations.

 With the wire of the night, the terrestrial rotation carries the stars towards the west and the constellations of the spring (Leo, Virgo, Raven) then of the summer (Swan, Lyre, Scorpion) make their return by the east. At the start of this year, the orange glow of the planet Mars is visible at dawn, not far from the red star Antares of Scorpio.

Some celestial meetings not to be missed
If you read this blog regularly, you know my passion for the Full Moon. I am not a werewolf, but I appreciate the serenity of the sunrises or sunsets of the lunar balloon as much as the luminous nocturnal atmospheres so particular that it can give birth. There are a dozen Full Moons each year, which may seem like a lot, but the vagaries of the weather and professional or family imperatives drastically limit the opportunities to contemplate our neighbor. 

So I can only hope that it will be sunny this Friday, January 10 because the Full Moon of the day will take advantage of it to flirt with the edge of the earth’s shadow. It is not a total eclipse, nor even a partial eclipse like that of July 16, 2019, only a passage of our satellite in the penumbra zone which envelops the shadow cone of the Earth, all this zone from which the disc solar is partially obscured by the terrestrial limb. We will have to be content with that because 2020 is a year of lean cows for lunar eclipses, with only partial eclipses by the dark – four in total. In mainland France, the Full Moon approaches darkness shortly after rising and sinks inside until the maximum, at 8 h 11 m, Paris time.

 The Moon is then at more than 25 ° in height above the eastern horizon and a beautiful difference in luminosity is perceptible with the naked eye between the north and the south of the selene globe. The northern polar region is in fact just outside the penumbra while the southern pole is almost in contact with the shadow. The lunar disc leaves the dark at 22 h 12 m.

At this start of the year, the observation of the Scorpion is all the more interesting as its main star, Antares, receives a visit from Mars. The name Antarès comes from the ancient Greek and means the equal or the rival of Mars, the glowing brightness of this supergiant star can be compared to that of the red planet. Antares is currently 1.5 times brighter than Mars, but that will not last because we are in a year of Martian opposition and the distance from Earth to Mars will decrease until October. 

In just over a month, Mars will become as bright as Antares and it will shine 25 times brighter this fall; it will then be located in Pisces, more than 130 ° away from Antarès, making their comparison delicate. On Monday 20 and Tuesday, January 21, an hour and a half before sunrise, the crescent moon joins the spectacle above the southeast horizon.

We had lost the luster of Jupiter in the twilight gleams in December and here it is, which returns at dawn in late January. On Thursday, January 23, the presence of a thin lunar crescent not far from it, at less than 3 °, is a good opportunity to try to spot it with the naked eye. One hour before sunrise, settle in front of the southeast horizon and watch for the appearance of this planet, which is bright enough to impose itself on a background of the sky already colored by the birth of the day. It is really important to choose a site offering a perfectly clear view because Jupiter is less than 2 ° in height, less than the thickness of your thumb with your arm extended. Easy if the atmosphere is clear, this observation can become particularly delicate if a layer of mist or pollution comes to spoil the party.

At the end of Januaryat sunset Venus shines more than 30 ° above the southwest horizon, a third of the distance at its zenith. For any other planet, this information would be of no great interest, but Venus is the most brilliant point star in our sky and, when we know where to look for it, this planet is clearly visible to the naked eye in the blue sky. clear. The most difficult is, in fact, to manage to take stock of this little spark because our eyes tend to lose focus infinitely on a blue sky without any markers, a bit like the autofocus of a camera that hesitates back and forth if you frame a uniform area of ​​sky. 

The presence of a beautiful lunar crescent at less than 5 ° on the left of Venus on Tuesday January 28 is therefore an asset to detect this planet as soon as possible, even before sunset. In any case, half an hour after the departure of the sun, the Venusian lighthouse will be obvious to locate, just like the crescent, and you will be able to take up another challenge: to find Mercury at the level of the western horizon- South West. The first planet in the Solar System is currently bright and is an easy target in a clear sky, even when it shines below 3 ° in height.

Phases of the Moon in January
The Moon is in the first quarter on the 3rd in the Whale, full on the 10th in Gemini, in its last quarter on the 17th in Virgo and new on the 24th in Capricorn.

Sky map visible in January 2020 towards the end of twilight at the latitude of metropolitan France. The position of Venus in relation to the Aquarian stars is accurate for the middle of the month. The cards in this post can be used in Europe and worldwide within a band extending from 38 ° to 52 ° north latitude. If you are more than 45 ° north, the North Star will be higher in your sky and, in the evening, the Pleiades cluster will be all the closer to the southern horizon. 

If you are less than 45 ° north, the North Star will be closer to the northern horizon and the Pleiades will be further from the southern horizon. Click on the map to enlarge it and print it for your personal use.

This map shows the sky visible in January 2020 at the edge of dawn at the latitude of metropolitan France. Notice the small orange ball of the planet Mars at the level of the east-south-east horizon, not far from the bright star Antares of Scorpio. Please note that the cards in this ticket are not upside down! They simply represent the stars which are located above our heads. If you lie down with your head to the north and your feet to the south, the east would be good on your left and the west on your right. Use these cards by printing them out and rotating them so that the name of the direction you are looking in is written on the spot. 

The constellations and stars that you will find in the portion of the sky that faces you are all those whose name is legible without bending your head too much. The names of the constellations and their main stars are indicated, as well as the layout of the most important constellations; this line is sometimes incomplete when the figure is partially hidden under the horizon. The sky is very large and the constellations that appear small on the maps are, in fact, very large: your open hand and outstretched arm barely hides the whole of the Big Dipper Chariot.

The diagrams and the text of the presentation of the celestial meetings announced in this post are adapted from my annual work The Sky with the naked eye , whose 2020 edition awaits you on the tables of bookstores. Superb astronomical phenomena will occur next year, several close approximations between the planets Mercury, Venus, Mars, Jupiter and Saturn – with in particular a sumptuous passage of Jupiter at 0.1 ° only from Saturn! -, Venus which will cross the star cluster of the Pleiades in April and will be obscured by the lunar crescent in June, a remarkable opposition of Mars and the most beautiful shooting stars of August, November and December which will melt in a very dark sky . To avoid missing any of these shows, use my 2020 Astronomical Calendar and learn how to observe or photograph them and read Heaven with the naked eye.

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