Tag: Night sky

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Nature Science Stargazing Universe

The Perseids Meteor Shower

A meteor shower in the Night sky
A meteor shower in the Night sky

You can start preparing for an amazing stargazing event: the Perseids meteor shower! The event has already started in mid-July, and can still be observed until the 24th of August. Its peak will occur on August 12, so make sure you organize a stargazing session soon! Thus, if the weather is clear and the nights are dark – make sure you go out somewhere and look up in the night sky, in the direction of the Perseus constellation!

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

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!

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 Perseids

Concerning the Perseids now, you should also know that meteor showers are named in function of the constellation where they originate. So, the Perseids seem to originate in the constellation of Perseus, hence their name! The same goes for another well-known meteor shower: the Lyrids, which seem to originate in the constellation Lyra.

Moreover, the Perseids is a predictable event – that is, they occur because of the crossing of Earth’s path with the orbit of the Swift-Tuttle comet, which was last visible from Earth in 1992 (and will next be visible in 2126!). The intersection of Earth with Swift-Tuttle’s orbit occurs each year around July-August, thus, the Perseid meteor shower is then expected!

So, what should you do?

Go outside, away from big cities. Ideally, avoid any source of nearby lighting, including your car’s lights or your phone’s screen. Make, of course, sure that the sky is clear of clouds and try to find the Perseus constellation. To do this, guide yourself with bright stars (with lower magnitudes), such as the Big Dipper asterism and the Cassiopeia constellation: imagine a very thick line between the two and look just below this line, towards the “W”-shaped Cassiopeia. There will be Perseus, and the Perseids will seem to originate from there.

Best is to use your own eyes to see, in order to have a larger field of view, thus no binoculars or telescopes. And make sure you let your eyes adapt to the darkness first! And then comfortably sit somewhere and just look at the sky and let the show begin!

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Stargazing Universe

Magnitude in Astronomy

The Full Moon has a -13 magnitude
The Full Moon has a -13 magnitude

You will often hear the term “magnitude” in Astronomy. Have you ever wondered what it meant? In this article, we’ll try explaining this term and we’ll see how to use correctly the “apparent magnitude” or “absolute magnitude” when talking about astronomic objects in the sky.

What is magnitude?

To keep things simple, in astronomy, “magnitude” refers to the brightness of an object in the sky. What we need to be particularly careful about, is the fact that the brighter the object, the smaller its magnitude! For example: a star with magnitude 1 is brighter than a star with magnitude 2! …And you guessed it, magnitude is unitless, that’s why we say “magnitude 2” or “2 magnitude”.

Apparent and absolute magnitude

Let’s imagine that we are on the top of a hill and we look at a very distant street light, down in the valley; let’s say this street light is 5 km away. From the top of the hill, we can see that the light is of a certain brightness. Now, imagine we start walking towards the street light. As we approach it, it seems that it gets brighter and brighter. So, how can we quantify the brightness of the street light if it seems to vary in function of where we are, relative to it?

In Astronomy, this issue is addressed by using two types of brightness – or, more correctly, two types of magnitude – for a celestial object: its apparent magnitude and its absolute magnitude. Most of us – at least in the near future! – will probably see the Moon, the stars, the planets and any other bright object in the night sky from our own planet, from Earth. All these objects will have a certain brightness, as they are seen from Earth, and this brightness is characterized by the apparent magnitude. So, the apparent magnitude of an astronomical object is the brightness of that object as seen from Earth.

As for the absolute magnitude, it is defined as the apparent magnitude of an astronomical object, as seen from a distance of approximately 310.000.000.000.000 km (the equivalent of 10 parsecs). The “usual” astronomer will just stick to the apparent magnitude; however, the absolute magnitude is important in research and studies, for example, for comparing the “real” luminosities of two or more objects.

Also, when talking about just “magnitude” – thus without specifying “apparent” or “absolute” – it’s the apparent magnitude which we refer to.

Magnitude values

Remember that a lower magnitude means a brighter object. But brighter of how much exactly?

The magnitude scale is logarithmic. Which means that the values which are to be displayed and compared on this scale are very far apart: the largest numbers are very much larger than the smallest numbers to be compared. To get a sense of it, magnitude 1 is 100 times brighter than a magnitude 6 (and not just 6 times brighter, as it would be the case on a “normal” scale).

Here are a few examples of magnitudes, to get an idea how this works:

  • The Sun has a magnitude of -27
  • The full Moon has a magnitude of -13
  • The International Space Station, when brightest, has a magnitude of -6
  • Planet Venus, when visible and when brightest, has a magnitude of -5
  • Sirius, the brightest star in the sky, has a magnitude of -1
  • Vega, the brightest star located in the Lyra constellation, has a magnitude of 0
  • The human eye, unaided, can normally see up to magnitudes of +3 – +6 (in function of the light pollution)

Can you now imagine how much brighter is the Sun (of magnitude -27), which you can’t even look directly at, compared to a Full moon (of magnitude -13)?

Magnitudes can be negative or positive, and the same rule applies: lower the magnitude – brighter the object.

And you guessed it: all “bright” objects have a magnitude, even the Sun, natural satellites or artificial objects (such as the ISS)!

The star Vega, besides being one of the brightest stars in the night sky and besides guiding us to find the Lyrids meteor shower each year in April, is also the reference point on the magnitude scale, having a value of 0.

Categories
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!

Categories
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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Aurora Labs Vadsø

Vadsø Sky Lights

Northern Lights in the Arctic Night Sky
Northern Lights in the Arctic Night Sky

During autumn, a typical day here in Vadsø starts with the Sun rising in the morning, just like anywhere else on Earth. But, after just a few hours of daylight, during which beautiful clouds color the heavens in white and greyish shades… it’s time for the Sun to set around noon, in its typical red and yellow sights, making room for the polar blue evenings.

And a short while after that… the amazing night show starts! Northern Lights turn the sky green, and, along with the stars and the Milky Way, they create an outworldly atmosphere, and you can easily imagine you’re… well… somewhere out of this world! Yes, it’s that beautiful!

Just look at my new video and picture yourself here, in the Arctic wilderness, with your head turned up towards the heavens, and just start dreaming!