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Nature Science Stargazing Universe

The Lyrids Meteor Shower

Shooting Star
Shooting Star

Stargazers (almost) all around the world, get ready for an amazing stargazing event which starts tomorrow: the Lyrids meteor shower! Keep on reading to discover what a meteor shower is, and to find out how to see the Lyrids and other interesting facts about them! And don’t forget to prepare your wishes – maybe they will get granted, once you see the Lyrids!

What is a meteor shower?

A meteor shower on Earth usually occurs when our planet’s path intersects with the orbit of a comet. When a comet approaches the Sun, some of its ice vaporizes, leaving behind a stream of dust and debris, called a “dust trail” (which is different from a comet’s tail). When such debris – called meteoroids or micrometeoroids, in function of the size, and which is most of the time the size of a grain of sand -, enters Earth’s atmosphere at very high speeds (typically 70 km/s), it heats up because of the friction with the air in the atmosphere, which causes the particles to light up and glow. This streak of light crossing the night sky is called a meteor, or shooting star. So no, a shooting star is not a real “star” 😉

Meteors usually occur in Earth’s atmosphere at an altitude of above 50 km, and under 100 km. The glow can be fainter and shorter for smaller particles and it becomes brighter and longer as the size of the particle increases. The colour of a meteor can also vary, in function of the chemical composition of the particle!

And, by the way, a meteor that doesn’t burn up and which finally hits Earth’s surface, is called a meteorite!

The radiant

What is very interesting is the fact that the meteor particles in a meteor shower originate from a point called the radiant, and are all travelling in parallel paths.

But if we look at the sky, we see the meteors radiate in all directions. So how can this be? This is the effect of perspective! For example, if you sit in the middle of a straight railroad track and you look along it, you see that the two tracks converge at a single point, somewhere far away. This is exactly what happens with meteors in a meteor shower, but the effect is a lot more intense, due to the great distances where the meteor shower occurs!

The two parallel tracks seem to converge at a single point.

The Lyrids

The Lyrids are a meteor shower starting on April 16 and lasting until April 26 every year. This spring, its peak will be on April 22, so make sure you go out around this date, if you’d like to see this meteor shower in all its beauty; weather permitting, of course!

To locate the radiant of the Lyrids, you will need to find the Lyra constellation in the night sky. It’s not so difficult to find it, as Vega, the brightest star of this constellation, is one of the brightest stars in the night sky, with a magnitude of around 0, thus easy to see even in light polluted areas.

One way of easily finding Vega, is by drawing an imaginary line between two stars forming the well-known Big Dipper asterism, as shown in the below image:

Extend this imaginary line in the arrow’s direction, until you reach your first (very) bright star, which will be Vega. Be sure not to extend the line too long, as you will reach another quite bright star – Altair.

However, to see the actual meteor shower, you would need to find a place away from light pollution, as the shooting stars are not as bright as Vega! Their magnitude average somewhere towards the value +2, sometimes culminating with “Lyrids Fireballs”, which is the name given to some brighter meteors of this event. In addition, the Moon may make it more difficult to see this year’s Lyrids, so, if our natural satellite is troublesome, just wait for it to set, before trying to spot the meteor shower.

Naming and predicting meteor showers

Meteor showers are named in function of the constellation where they originate. So, the Lyrids seem to originate in the constellation of Lyra, hence their name!

The source of the dust creating the Lyrids comes from the C/1861 G1 Thatcher Comet – a long-period comet (415 years).

The Lyrids is a predictable event – that is, they occur because of the crossing of Earth’s path with the orbit of the aforementioned comet, which was last visible from Earth in 1861, when it was discovered by A. E. Thatcher (and is expected to be seen again in 2283!). The intersection of Earth with this comet’s orbit occurs each year in April, thus, the Lyrids meteor shower is then expected!

Did you know?

The Lyrids are the oldest reported meteor shower – since 687 BC!

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Nature Science Universe

The Polar Night

Polar Blue during the Polar Night in Vadsø
Polar Blue during the Polar Night in Vadsø

This period of the year means the beginning of the end of the Polar Night for regions in the Arctic. The polar night in Vadsø will end on the 17 of January, when the Sun will rise for the first time this year in the Arctic sky, for only 50 minutes. After this date, each day will mean the Sun will come out higher and higher in the sky and for longer periods. And this until May 17, when the Sun will never set for almost 2 months, marking the beginning of the Polar Day.

But what is the polar night?

Earth carries out two types of rotations: one around the Sun, during the course of a year, and the second around its own axis, during 24 hours. At the same time, Earth is inclined in respect with the Sun, at an angle of approximately 23°, and remains tilted at this angle during the whole year.

This means that the Earth is illuminated by the Sun differently during one year. At and around the winter solstice (sometime around 22nd December each year), Earth is inclined in such a way that the North Pole and the region around the North Pole, points away from the Sun, meaning it is not illuminated by our star, which translates into a continuous night – phenomenon which we call the Polar Night.

Just take a look at the first part of this video from the California Academy of Sciences, and see how Earth is illuminated by the Sun during a whole year.

You can see that the length of the polar night varies in function of latitude: closer you are to the North Pole, longer the polar night is. At the exact location of the North Pole, the polar night lasts no less than 6 months! At lower latitudes, but still above the Arctic Circle, the Sun never rises for shorter periods. The shortest polar night occurs on regions exactly on the Polar Circle (at 66°N), where the Sun never rises for only 1 day, which is exactly the day of the Winter Solstice!

Moreover, in function of latitude, the Polar Night may be experienced differently, concerning the position of the Sun below the horizon. This means that during the polar night, closer to the Arctic Circle, the Sun will still be near the horizon (but still below it) during the normal “day” hours. Which means that twilight occurs – thus indirect light from the Sun beautifully illuminates these regions, and you are able to see the landscape and the surroundings. And it does it in a surreal blue lighting – which is what the amazing polar blue is! Vadsø in Northern Norway experiences this phenomenon during the whole period of the polar night.

Me during the Blue Hour outside of Vadsø, during the polar night
Dogsledding in the Varangerhalvøya National Park, during the Polar Night

Further up from the Arctic Circle, the Sun does not have time to get so close to the horizon, which means that no indirect light will illuminate these regions at all, which leads to a 24-hour long pitch-black night, which can last for months!

And the best part about the Polar Night? You can see the Northern Lights even during the “daytime”!

Regions below the Polar Circle experience a normal day/night cycle, which varies also in length, in function of the exact latitude.

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Nature Stargazing Universe

See the “Bethlehem Star” in the Night Sky

The Great Conjunction of Jupiter and Saturn occurs on 21 December 2020.
The Great Conjunction of Jupiter and Saturn occurs on 21 December 2020.

In astronomy, a conjunction means the “meeting” of two planets in the night sky. Jupiter and Saturn, the biggest planets in our Solar System, can meet as well, but when they do, their conjunction is a “great” one – hence the term Great Conjunction!

Jupiter and Saturn are one of the brightest objects in the night sky. They look just like two very bright stars – but don’t mistake them for stars! They are planets, so they don’t create light themselves just like the stars (like our Sun does for example). They are “lit” only because of the reflection of the sunlight. Which is the same reason why the Moon shines in the night sky!

The Great Conjunction of 2020

In their perpetual movement around the sun, it happens sometimes that planets “meet”. The word “meet” is quoted because the planets don’t actually meet in reality. It is just how we see things from here on Earth. In fact, the two planets are aligned in such a way in their orbits, that from Earth, we see them as if they came into contact with eachother. In reality though, they’re some million kilometres apart!

And why is this conjunction “great” you may ask? Well, this is because Saturn and Jupiter, due to their size, they are already bright even when they’re “apart”. When two bright lights touch each other, they are seen like only one light, even brighter! The same happens with the conjunction of Jupiter and Saturn.

When does it happen?

Jupiter and Saturn are already close in the night sky since quite some time now. But on December 21 (thus tomorrow!), the two planets will be so close (less than 0.1 degrees) that they will look like an elongated, very bright star. So, stargazers, get ready for a Christmas treat!

Why is the Great Conjunction so special this year?

The Great Conjunction occurs regularly, roughly every 20 years. But why is it so special this year?

In function on the position of the “meeting” with respect to the position of the Sun, the conjunction may be more or less bright. If this meeting place is too close to the Sun, the brightness diminishes. This year, the position is ideal for a very bright Great Conjunction!

Another thing to take into account is how close the two planets will appear to be. Not every 20 years the planets have such an apparent closeness! In fact, to get an idea of how rare this occurs, know that last time Jupiter and Saturn appeared so close, was in year 1226! It actually happened in 1623, but it was rather close to the Sun, which made it actually less visible.

Where and how to look?

You need to look in the night sky about 1 hour after sunset, almost anywhere on Earth, even in light polluted areas! In the Northern hemisphere look towards south-west. As for the Southern hemisphere, look towards the west. Needless to say that you will need a clear sky!

It will be impossible to miss such an impressive sight so, don’t worry, it will not be difficult to spot it!

“Christmas Star”

As the Great Conjunction this year happens very close to Christmas, it is also called the “Christmas Star“, or the “Bethlehem Star“. To go even further, some astronomers believe that the Star of Bethlehem which led the Three Wise Men to the place where Jesus was born, might have actually been a Great Conjunction! But there are other theories that suggest that a supernova might have occurred that time. Or, was it indeed a divine miracle?

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Nature Science Stargazing Universe

The Belt of Venus or the Anti-twilight Arch

Full moon rising underneath the Belt of Venus
Full moon rising underneath the Belt of Venus

You now know why sunsets and sunrises are red (if not, read this article and find out!). But did you know that another beautiful light phenomenon occurs at sunset and sunrise, besides the beautiful reddish skies? It actually occurs opposite of where the Sun is setting or rising, thus opposite of where all the beautiful reddish colors light up the sky! So, next time you have a clear sky, try looking away from the nice sunset, in order to see the anti-twilight arch! But what is this anti-twilight arch?

Let’s explain its name first

The Belt of Venus, which is a stylized name for the anti-twilight arch, is a pink glow above the horizon, right opposite of where the Sun sets/rises. This opposite place of the Sun is actually an imaginary point, which we will call from now on the antisolar point (anti means opposite).

The phenomenon takes place during twilight – thus before sunrise or after sunset respectively. It is represented by a pink glow that surrounds, just like an arch, the horizon opposite of where sunsets and sunrises occur.

So there you have it – the anti-twilight arch!

Concerning the name “Belt of Venus”, contrary of what you might guess, it’s got absolutely nothing to do with the planet Venus, or any of its belts or rings (…which do not exist anyway!). Planet Venus has a smaller orbit around the Sun than Earth does, and this makes Venus visible to our eyes only around sunsets and sunrises, similar to how the antitwilight arch becomes visible at sunset and sunrise. This is the only association that the Belt of Venus might have with the actual planet. The name Belt of Venus is, in fact, inspired from the girdle which was supposedly worn by the goddess Venus and which might resemble the pinkish arch around the antisolar point, at twilight.

So what exactly is this Belt of Venus?

After sunset (or before sunrise), the Sun is below the horizon, relative to an observer on Earth. In the figure below, the observer’s line of sight is represented by the thin grey line and the Sun is below this line of sight, thus below the observer’s horizon. The dotted circle around Earth represents our planet’s atmosphere. Even though the Sun is below the horizon, right after sunset, light rays from the Sun still make way to get to the observer and even further (red arrow), till above the antisolar point, where they get backscattered off Earth’s atmosphere (pink arrow). This region, where the backscattering takes place, has a belt shape, and this belt is nothing else but the antitwilight arch!

In this figure, notice that the backscattering “point”, at the tip of the red arrow, is a little above the line of sight for the observer. The small region between the backscattering point and the line of sight, is represented by a dark belt, which is our planet’s shadow.

What will you, as observer, see? Well, if you look right opposite where the Sun is setting, you will notice, right after sunset, a faint pinkish light, stretching around the antisolar point, like a belt, or arch. As time passes, this pinkish glow will rise. Right underneath it, you will see a darker belt, which is nothing else than Earth’s shadow! As time passes further, the pinkish glow will rise even more, as will our planet’s shadow, until night will take over entirely and it will become pitch black outside.

This effect is sometimes very faint, and in order to get a good view, you will need, first of all, a clear sky. Best is also to have a clear horizon above the antisolar point as well, in order to distinguish this effect as better as possible.

So, now that you know about the antitwilight arch, I dare you to ignore a beautiful sunset and look right opposite! But I promise that if you do, you will get to see another magnificent optical phenomenon, less known, but of equal beauty! Have you already seen the Belt of Venus?

The Belt of Venus. Image credit: Kent Duryee (https://commons.wikimedia.org/wiki/File:Belt-of-venus.jpg), „Belt-of-venus“, https://creativecommons.org/licenses/by/4.0/legalcode
The Belt of Venus.
Image credit: Kent Duryee (https://commons.wikimedia.org/wiki/File:Belt-of-venus.jpg), „Belt-of-venus“, https://creativecommons.org/licenses/by/4.0/legalcode
Categories
Nature Science Universe

Why are sunsets and sunrises red?

Beautiful sunset over the Dammen Pond on the Vadsøya island
Beautiful sunset over the Dammen Pond on the Vadsøya island

This period in Vadsø, as in much of the Arctic region, nights begin getting longer and longer. It’s not yet the Polar Night, which means that everyday, beautiful sunsets and sunrises mark the beginning and the end of the dark, cold Arctic nights. But what makes sunsets so beautiful? Why does the sky and the Sun turn red?

In order to answer this, we need to review the same concepts we took into account when answering the question “why is the sky blue?“.

Light is an electromagnetic wave, just like radio waves, microwaves, and even the radiation resulted from radioactivity! The only difference between all these different electromagnetic waves is their wavelength.

Even the light that we actually perceive with our own eyes is made up of multiple wavelengths. And to each and all of these wavelengths of light corresponds a different colour! So, the light that comes to us from the Sun and which we see, is made up of multiple colours! Of all colours, to be exact!

Just like an ocean’s waves, light travels the same way: in waves! Blue light travels in shorter waves (with a shorter wavelength) and red light travels in longer waves (longer wavelengths).

When the sunlight, with all its colours, reaches Earth, it meets the planet’s atmosphere! Thus, it starts interacting with various particles in the air, such as tiny ice crystals, dust, water droplets and even gas molecules that make up the air itself! And once the light waves interact with these particles, it gets scattered!

For a wave to interact with a particle, the two must be of the same order of size. Smaller particles scatter short wavelength light (blue) stronger. Small air molecules, which make up the entire atmosphere, scatter the blue component of sunlight the most, and in all directions, because of its short wavelength! And this is why, during a sunny day, everywhere you look, the sky is blue!

At sunrise and sunsets however, the Sun, relative to us, finds itself at low positions in the sky. From these low positions in the sky, sunlight needs to travel longer distances, through thicker amounts of the atmosphere in order to reach our eyes.

At sunset and sunrise, sunlight travels a longer distance (pictured as the thick yellow arrow) through the atmosphere until it reaches our eyes.

Because of this, the light gets scattered more strongly by the atmosphere. Blue light, which gets scattered easiest, is in fact scattered so much, that it is mostly removed before it actually reaches our eyes. Which in turn means that there is more red light (which gets scattered the least) left for our eyes to see.

Me at sunset, on the shore of the beautiful Varanger fjord.