Paolo Sirtoli

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Astronomy in Maldives

This corner of paradise is widely renown for the beautiful sea, coral beaches and breathtaking sunsets, giving us never-ending emotions. But we should consider that every sunset opens the curtains of a fantastic sky without light pollution and full of wonders we cannot see from our latitudes.

In these pages we will present some astronomical observations that can be done during your stay in Maldives. Contrary to popular belief, you can do astronomy even in broad daylight!
You can also skip to the following pages:
The maldivian sky in January-February-March
The maldivian sky in July-August-September

These pages come from the author's decades of experience as a popularizer of astronomy, in collaboration with magazines, websites, publishers and resorts worldwide.

Contacts:
paolo.sirtoli@gmail.com

In daytime

The motion of the Sun Near the equator you see the sun rising and setting ... almost vertically.
As shown in the figure below, the path of the Sun in Europe is a line inclined at about 45 degrees above the horizon. Instead, near the equator the apparent motion of the Sun is perpendicular to the horizon.

This has a remarkable consequence: sunrise and sunset complete in little more than twenty minutes. It?s amazing to be talking in the middle of broad daylight and find yourself in a pitch dark shortly after ...
The following figure shows the hours of light (yellow), of darkness (gray), twilight (pink), and dawn (blue) for the cities of Milan and Male. The glitch in the graph of Milan is due to daylight saving time. In Maldives instead, the lines are continuous because that country does not observe daylight saving time.

As you can see from the thickness of the blue and pink lines, the duration of sunrise and sunset in Maldives (about 20 minutes) is significantly lower than in Europe (about 30 minutes).

In addition, you will immediately notice that sunrise and sunset times in Maldives are practically constant. To know the rise and set times of the sun and moon, see this link.
Please be aware that most of the Maldivian resorts add one hour to local time, to better exploit daylight.

Another consequence of this strange journey of the Sun: our star rises high in the sky, almost to the zenith, the point overhead. We must therefore be very careful with the effects of its radiation and use a highly protective sunscreen. A protection factor of 30 may seem absurd: why go to the Maldives, wearing a shirt ...? Yet people get very well tanned even so, and, moreover, without skinburns.

Observations of the Sun must be performed only through special filters that block almost all of its light.
If you are lucky, you will see black spots on the solar disk: the sunspots. They are also visible to the naked eye, but only the biggest ones and when the Sun is effectively filtered by the thick layer of atmosphere near the horizon. Sunspots are likely to appear in the vicinity of the peaks of the solar activity, which has a cycle of eleven years. The next maximum will occur around 2024.

DO NOT EVER try to observe the Sun through binoculars or a telescope without solar filters!

Tides

As everyone knows, tides are periodic changes of the sea level.
Every day you will see two high tides and two low tides, separated by about 12 hours.
Day by day you can observe that tides get late by 50 minutes. Moreover, also the difference between high and low tide varies with a period of about two weeks (spring and neap tides). If one day we have the maximum excursion, a week later it will be minimal, then one week later the tide will be back to maximum, and so on.

High and low tides in Maafushivaru, Ari atoll

Tides can be attributed for two-thirds to the Moon and for the remaining third to the Sun. The cause of tides is the gravitational field, which decreases with the square of the distance.
If we stand on a scale, it will record our weight, which is the attraction force that Earth exerts on us. At twice the distance from the center of the Earth (we should climb up to 6380 km height!), we would weight only one quarter of our actual weight. At a triple distance, the weight would be reduced by nine, and so on.

To understand tides, let?s consider a person standing on the Earth's surface. As we just said, their feet will be attracted by the Earth with some force. Their head is slightly farther from the Earth and then it will perceive a slightly minor attraction. Result: there is a very small force which tends to "stretch" the person along its height, just like a ... torture rack.

Our planet, then, in the gravitational field of the Moon, suffers such a stretch. The solid part is only slightly deformed: about 30 cm; instead, the liquid part is much more deformed, because the water is free to flow and then it collects in two lobes, called the sublunar and antilunar lobes.
The different amplitude of tidal excursion is explained by the combined influence of the Sun and Moon.
When the two celestial objects are aligned (new or full Moon) the Earth will be stretched along the same direction and therefore the tidal excursion will be maximum.
If Sun and Moon are in quadrature (first or last quarter) the Earth will be stretched in perpendicular directions, the larger effect being due to the Moon. In those cases the difference between high and low tide will be minimal.

There is another effect to consider: since the Earth rotates on its axis in 24 hours, every point passes through two high and two low tides, but also through four tidal currents.
These currents must be taken into consideration not only for navigation but also for scuba diving. These currents are minimal in periods of high and low tides, the ideal phases for diving.

If we compare the theory and the actual pattern of tides, we will find significant differences.
The truth is that the shape of the Earth and seabeds, extremely complicated, makes tide prediction very difficult. As a result, the only way to predict the tides is to rely on the local harbor master and require a pilot book with the predictions of the tides.

One more thing. Corals, which are the creators of Maldives, are the silent witnesses of the past of our planet. Their cycle of growth, stimulated by the alternance of day and night and of the seasons, was impressed into their limestone.
Indeed, we can read in a section of coral the alternance of day and night in the form of thin lines, and the alternance of the seasons in the form of thicker lines. As you would think, within a year (the distance between larger stripes), we can count 365 thin lines.
But if we study a fossil coral dating back to 500 million years ago, we note a very strange thing: between the lines, we can count about 400 thin lines. What does this mean?

It means that, in one year, there was a greater number of days, so every day lasted only 20 hours!
This is due to the fact that the rotation of the solid Earth within tidal lobes dissipates energy, so that the Earth gradually slows down its rotation.
However, the physics teaches us that the Earth-Moon system cannot lose rotation (physicists call it ?conservation of angular momentum?) as if it were a clock that exhausts. The angular momentum is conserved, because the Earth-Moon system is isolated.
Then the angular momentum lost by the Earth is gained by the Moon, which passes to orbit farther and farther away from Earth. We deduce then that the Moon once stood closer to the Earth. Today is moving away at a rate of about 2 inches per century.

The great writer Italo Calvino wrote a series of short stories called Cosmicomics, the first of which is entitled The distance to the Moon, and talks about the age when the Moon was much closer to Earth, just enough for a ladder climb;-)

I know for sure! - Exclaimed the old Qfwfq - you cannot remember but I do. We had always her, the Moon, huge, when it was full ? nights clear as by day, but on a light colored like butter - it seemed as if she were to crush us; when it was New Moon she rolled through the sky like a black umbrella led by the wind, and in waxing Moon she came forward with horns so low that it seemed just about to pierce the crest of a hill and get anchored. But the whole mechanism of the phases was unlike nowadays: because the distances from the Sun were different, and the orbits, and the inclination can not remember what. Not to speak about eclipses! being the Earth and the Moon so close, there were eclipses all the times: imagine if these two beasts could not find a way to cast shadow over each other constantly.

[Italo Calvino, Le cosmicomiche, Mondadori]

The green ray

The Sun near the horizon is a reddish placid figure distorted by the atmosphere in a sort of oval. When the sky is very clear you can possibly see a beautiful phenomenon: the green ray. The last rays of sun will appear deep green: unforgettable.
A Scottish legend says that those who can see the green ray will never be disappointed by love!
The cause of this phenomenon is the Earth's atmosphere, which not only distorts the shape of the Sun, but is also able to decompose it in different colors, more or less like a rainbow.
When we see the sun touching the horizon we're looking at a mirage because actually the Sun is physically already below the horizon. The atmosphere near horizon is thicker, thus is able to deflect the image of our star by a good half a degree, in fact its diameter.

In addition to the image deflection, the atmosphere is able to break it down, so we'll have different images of the Sun, differently colored and almost perfectly superimposed.
At the bottom there is the red image, just above the yellow one, and the highest is the green. If the atmosphere is exceptionally clean, as sometimes happens in the Nordic countries, we could even see the blue component of the solar disk.
We must prepare ourselves for the green beam when we look at a very clear sunset. In order for the green beam to be visible, the Sun must be as white as possible and get to the sunset without being filtered by the atmosphere. If we are lucky, we will see the last rays of sun bright green for about a second.

The green ray, captured in this beautiful photo by Danilo Pivato

The International Space Station (ISS)

In the hour following sunset or before dawn, it may happen to witness a very strong light in the sky, slowly moving across the constellations.
Yet it's not a plane: it does not flash and, viewed through binoculars, it remains a dot. Sometimes this object becomes redder until it disappears, as if it was swallowed by a shadow.
Well, you just witnessed a pass of the International Space Station, or ISS.
Who would have ever thought of being able to see it at naked eye?
After its completion in 2010, it?s a very large structure: it extends for about 110 meters and is home to six astronauts on board. From an altitude of 350 km the station orbits around the Earth in about an hour and a half: in one day, the astronauts onboard admire sixteen sunrises and sixteen sunsets!
Expert and well-equipped observers from earth can take extraordinary photos of ISS, such as the one on the right. To know in advance when the ISS and other satellites will pass above us, you can go to http://www.heavens-above.com enter your location, timezone (be careful about the additional hour with respect to Male time, applied by most of the resorts!) and check for results.

The column ?mag? is important: it tells us how bright the space station will be. The scale is reversed: the lower the number, the better. The passage of 7 March will therefore be spectacular!
On that day, according to the table, we shall be ready at 18:51 and look north-west (NW). We will see the space station rise until 72 degrees above the west-southwest (WSW) horizon.
Clicking on the date we will have a convenient map of the sky, which should be kept above the head and properly oriented according to the cardinal points.
Sometimes the ISS track in the sky is interrupted: it is the entrance of the ISS in the shadow cast by the Earth. We then will see the space station becoming redder and dimmer.
In those moments, the astronauts aboard the ISS will be admiring a beautiful sunset from space.

A spectacular ISS passage on march 7th 2007 (actually observed!).

Night time

A breath-taking maldivian sunset. Venus already shines hign in the sky.

The sun sets the western horizon to fire and greets us with a wonderful show. Almost unnoticed, the first stars light up the sky, promising a great night.
Minute after minute, the timid lights take courage and the sky is finally filled with stars. Some are bright as Sirius and Canopus, others just enough to draw in the sky the path of the Milky Way, our galaxy. The silence makes these unforgettable moments perfect.

The motion of the sky

Imagine to go to the North Pole: one can easily guess that we will have the North Star above our heads, and all of the stars will be rotating around it, running parallel to the horizon.
To make a useful comparison, it is as if the sky was an umbrella that we keep vertical and we do slowly rotate.

At our latitudes (about 45 °) the imaginary umbrella will be tilted by the same angle. Then the polar star will be high only 45 degrees above the horizon. All the stars will rise and set at an angle of about 45 degrees.
In Maldives, the imaginary umbrella shall be set almost completely to the side.
The polar star is almost swallowed by the Indian Ocean, to the north. All the stars rise and set at right angles to the horizon. The observer of the sky used to our latitudes will have the impression of looking at the sky "sideways".

The Moon

Like the Sun and all of the stars, in Maldives also the Moon rises and sets vertically.
The result is a curious effect: the "horns" will be facing upwards or downwards. We'll see ... in short, the Moon sideways.
The photograph on the left shows precisely a Maldivian Moon with horns facing almost exactly upwards.
Unfortunately, the Moon and the wonders of the sky do not go hand in hand, indeed. The lunar light disturbs the observations, which should be performed in the waning phase of the moon or near New Moon.

New Moon
The Moon is in the same direction as the Sun and is therefore invisible. This period is good for stargazing all night long.
First Quarter
The moon is illuminated by half: it sets at midnight local time. It is the ideal situation for public observations: in the first part of the night we can observe the Moon, and one hour after its set, we can observe the deep sky.
Full Moon
A very strong light that outshines the sky background. It rises when the Sun goes down and so it will be visible throughout all night. Better to devote to night dives.
Last Quarter
The moon rises at midnight and then we can take advantage of the first part of the evening for deep sky observations.

To learn about the phases of the moon for the current month, see this link. Just at the naked eye, the moon already reveals the rounded dark areas on its surface that in the past centuries were called seas. Today we know that there is no water on the Moon: unfortunately our satellite is an arid desert of dust and rocks.
Among the thousands of bodies that have impacted with the Moon, some were so massive that caused a fracture of the lunar crust, causing a leakage of magma. This lava filled the crater floor, leveling as a concrete floor. Here is the origin of the seas.
Normally what remains of an impact is a more or less large crater and possibly a halo of debris. The craters observed even with a modest telescope are simply extraordinary.
With a telescope we shall look at the terminator, which is the line that separates the dark from the enlightened hemispheres of the Moon. As a matter of fact, in that area the sunlight is grazing, enhancing the relief effect of the lunar mountains.
With adequate magnification, the vision will be as exciting as a trip into orbit around the Moon!

Finally, a very nice effect is visible in the days around the New Moon, when you see only a thin crescent. Actually in Maldives the air is so clear that the phenomenon can be perceived for several days.
The rest of the lunar disk is not dark, but it is dimly lit. The first impression is that the Moon has become ... almost transparent. This phenomenon is called Earthshine and it was explained for the first time by Leonardo da Vinci.
During the new moon, from our satellite the fully illuiminated Earth dominates the sky. We have to imagine a white-blue disk four times larger than the Moon. All that light illuminates the desolate expanses of the moon and we see precisely this "light of the Earth" as reflected by the Moon Earthshine.

The planets

The ancient Greeks had called by the name of wanderers (plančtes) those lights similar to stars but not fixed in the constellations. To the naked eye we can see five planets, the other two were discovered in modern times using telescopes.
It?s very easy to identify a planet in the sky: its light is absolutely steady. Instead, the light coming from stars twinkles.
Not all the planets are visible because sometimes they are to pass close to the Sun and then are outshined by its light. To find out which planets are visible on a certain date and time, you should consult a star chart, for example, the one you can get at http://www.skymaps.com

Some observational notes:
Mercury
He spends most of the time hidden in the glare of the Sun, but when he walks away from the Sun, it is quite bright in the pre-dawn or post-sunset sky.
Venus
Wonderful morning or evening star. A small telescope will show the crescent, just like the Moon. Before dawn, in the pure blue of the eastern sky, it is a really mesmerizing vision. One could recall the triplets of the first canto of the Purgatorio, where Dante says:

Dolce color d'oriental zaffiro,
che s'accoglieva nel sereno aspetto
del mezzo, puro infino al primo giro

a li occhi miei ricominciň diletto,
tosto ch'io usci' fuor de l'aura morta
che m'avea contristati li occhi e 'l petto.

Lo bel pianeto che d'amar conforta
faceva tutto rider l'oriente,
velando i Pesci ch'erano in sua scorta.

Soft coloring of oriental sapphire,
Collecting in the calm face of the sky,
Clear right up to the edge of the horizon,

Brought back delight again into my eyes
As soon as I stepped out from the dead air
Which overburdened both my sight and breast.

The beautiful, love-provoking planet
Was making the whole east break into smiles,
Veiling the Fishes that follow in her train

Mars
It reveals for its distinctly orange-red color and when you see it late at night, it is very bright. A good telescope will show some surface detail: the white polar caps and some dark region.
Jupiter
Very bright ?star?: using binoculars the four main satellites discovered by Galileo are clearly visible, lined up on its equatorial plane. Through a telescope the atmosphere shows brown and white stripes and the famous great red spot.
Saturn
Breathtaking, beautiful vision of a planet surrounded by a magnificent ring system. If the atmosphere is clear, you can catch a glimpse of the Cassini division as a dark break in the ring.
Uranus and Neptune
The two farthest planets of the solar system are never visible to the naked eye. Even with a large telescope, they show no more than a small blue-greenish disk.

Constellations

The Maldivian sky, at first, dazzles both layman and astronomers. The ?first time? is equal for everyone: at first one remains open-mouthed, unable to recognize any constellation.
There are so many stars and so brilliant (for us accustomed to gray-orange skies) that any reference vanishes. One could even recall that tremendous phrase of book "2001: A Space Odyssey ", when astronaut Bowman is the presence of the monolith, before slipping in the interstellar trip ...

David Bowman barely had time to utter a sentence that stuttering men waiting at mission control , millions of miles away fifty eighty minutes in the future, must never forget: " The thing's hollow ? it goes on forever ? and, oh my God, it's full of stars!

[Arthur C. Clarke, 2001: A Space Odyssey]
In the northern hemisphere there is a group of constellations called circumpolar because they never set. This is the main reference of the sky, a starting point to find all the constellations.
In Maldives there is no such a thing: all the stars rise and set, so it?s necessary to get a sky map.

The maldivian sky in January-February-March

The maldivian sky in July-August-September