Category: Science

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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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Northern Lights Science

Aurora Mystery Solved by “Surfing” Electrons

A new mystery of the Northern Lights has been solved!
A new mystery of the Northern Lights has been solved!

At the moment, scientists know a lot about what causes the Aurora, how it forms, what colors it can have, they know how to forecast the Northern Lights, and many, many other interesting and useful things about this beautiful phenomenon. But there are still a few questions which scientists are trying to answer.

One of these questions found an answer very recently (on June 7, 2021), thanks to the work of physicists from UCLA, Wheaton College, the University of Iowa and the Space Science Institute!

What is the Aurora?

The temperature in the Sun’s core is huge (like millions of degrees Celsius). At this temperature, a nuclear fusion reaction of hydrogen occurs. As a result, electrically charged particles (electrons and protons) are thrown out from the Sun’s atmosphere and they escape into space and, at some point, they reach Earth and they interact with Earth’s magnetic field (called magnetosphere), creating a so-called disturbance in the magnetosphere. The electrons from the solar wind then accelerate along the magnetic field lines and then collide with the gases that make up Earth’s atmosphere (mostly oxygen and nitrogen). These collisions determine the emission of visible light. It is this visible light what we call the Aurora Borealis or the Northern Lights.

Mystery solved

The mystery – until a few days ago – was that it was not well understood how the acceleration of electrons along the magnetic field lines occurs.

But the mystery is now solved! After creating, with the help of special scientific equipment, the same conditions just like those in Earth’s magnetosphere, the research team concluded that the acceleration happens due to the fact that the electrons “surf” along the electric field of a wave (in this case a so-called Alfvén wave, see what this is below), which transfers the energy of the wave to the accelerated particles, through a process called Landau damping.

Put it simply and without fancy words, as one of the researchers that took part in this study said, “measurements revealed (that the) electrons undergo (…) acceleration by the Alfvén wave’s electric field, similar to a surfer catching a wave and being continually accelerated as the surfer moves along with the wave”.

Alfvén waves are launched along the magnetic field lines, towards our planet, at the moment of magnetic reconnection, which is a violent process when two magnetic field lines couple together (which happens during a geomagnetic storm for example). Electrons from the solar wind, which are ‘trapped’ in the magnetic field line, “surf” along the field line, being accelerated by this Alfvén wave.

The science behind the Aurora

In this article is presented only a very small part of the Aurora science.

Now you have the chance to completely understand this magnificent phenomenon, starting from beginner level! I designed for Aurora Labs the Learn the Aurora workshop (either the online version, or the workshop we can do together here in Vadsø) where you can learn, through simple experiments and explanations (suitable even for the non-scientists!), the complete science behind the Northern Lights!

So, be sure to take part in my online workshop now, during summer, and be prepared to see (and understand) this beautiful phenomenon next winter!

…Oh, and did you know Aurora Labs can even certify you as an expert in Northern Lights? 😉

Categories
Science Stargazing Universe

Solar Eclipses

Solar eclipses are dramatic events
Solar eclipses are dramatic events

A solar eclipse occurs when the Moon, in it’s own movement, finds itself between the Earth and the Sun. One of the consequences of this alignment will be the blocking of a part (or all) of the Sun’s light here on Earth, in areas where the eclipse is visible. This is due to the fact that the Moon covers the Sun’s disk partially, or sometimes even totally.

Solar eclipses can thus be of two types: partial (when the Moon covers only part of the Sun’s disk) or total (when the Sun’s disk is covered completely by the Moon).

Total Solar eclipse

A total solar eclipse, which is the most dramatic – because the sky turns dark just like at night for a few minutes during mid-day – is much more rare, as the conditions needed for such an eclipse to occur, are much more strict.

For a total eclipse to occur, the Moon needs to be closer to the Earth on its elliptical orbit, so that its apparent size can be large enough to cover the Sun’s disk. In addition, the totality (the period of only a few minutes when the Sun is completely covered by the Moon) occurs only along a very narrow path along the Earth’s surface.

Annular and partial Solar eclipses

So, most of the Solar eclipses are not total!

But even if the Sun’s disk is not covered completely by the Moon, the concentricity of the two disks can create another beautiful Solar eclipse – an annular one, when the Sun is visible around the moon, just like a ring – hence its name!

However, most of the times a Solar eclipse will be partial, when the Sun’s disk will be partially covered by the Moon, and not in a concentrical manner. This is the most common type of Solar eclipse that we see.

Visibility of a Solar eclipse

One solar eclipse (be it partial, annular or total) can’t be visible from everywhere on Earth. The Sun needs already to be visible – which narrows down the visibility of an eclipse to less than half of our planet! As the relative positions of the Moon and Sun in the sky, seen from our planet, are always changing, the alignment of the two for an eclipse to occur, narrow its visibility down even more.

Sizes of the Sun and the Moon

The Sun is much bigger than the Moon, that’s for sure. So how can it be completely covered by the Moon then?

To answer this question, we need to look at the distance of the Sun and Moon, from us, from our planet. The Sun is much more far away from Earth than the Moon is! Which makes it have an apparent size more or less equal to the apparent size of the Moon! The Moon moves along an elliptical orbit around Earth, which makes it, at times, be closer to our planet. Which translates itself into a bigger apparent size of the Moon, which actually becomes slightly larger than the Sun’s apparent size. Which finally, can lead to a total Solar eclipse, if the other conditions for this event to occur, are met!

Looking at an eclipse

Warning! Never look at a solar eclipse with the naked eye. Not even sunglasses aren’t enough! In order to see a solar eclipse, you need a special solar filter, which makes it safe to look directly at the Sun. Otherwise, you risk getting extreme eye damage, and even blindness!

The Annular eclipse of 10 June 2021

On June 10 this year, an annular solar eclipse is scheduled to occur! The actual annular eclipse will be visible from a narrow band along Earth, which crosses the North Pole and a few far-North regions of Canada and Russia.

In the rest of the Northern Hemisphere, the eclipse will be a partial one and will be visible from places such as the Eastern part of the US, almost the whole of Europe and parts of Asia.

If, by any chance, you’ll find yourself in Vadsø, you will see a partial Solar eclipse, with a maximum obscuration of 51%, occuring at 13:09, Norway time.

For other location and times, check out this map from NASA to see exactly where on Earth the eclipse will be visible from, in 2 days!

And by the way, did you know that with Aurora Labs you can discover the mysteries of our own Sun by observing it through our telescope? The eclipse seen through a telescope (with a special solar filter, of course!) is a magnificent sight!

A partial solar eclipse.

Update June 10, 2021:

The beginning of the partial solar eclipse on June 10, 2021.

Categories
Nature Science Universe

The Polar Day

The Midnight Sun shines 24/24h during the polar day
The Midnight Sun shines 24/24h during the polar day

Regions way above the Polar Circle, in the High Arctic, have already started to experience the polar day. Other Arctic regions are going to experience the phenomenon in the coming days. In Vadsø, the polar day already started on May 17 this year, and the Midnight Sun has been visible since, as well.

But what is the polar day?

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 summer solstice (sometime around 22nd June each year), Earth is inclined in such a way that the North Pole and the region around the North Pole, points towards the Sun, thus it is illuminated more and longer.

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

The Midnight Sun

The Midnight Sun is a wonderphul phenomenon. It is what makes the sky bright at “night time” during the polar day, just like the Northern Lights brighten the sky during the dark period. It is a typical Arctic (and Antarctic) phenomenon, which occurs only during the polar day.

As the name suggests, here in the Arctic, the sun is visible in the sky at midnight, as well as the whole night and day, and it never sets below the horizon during this period. In Vadsø, the Midnight Sun will be visible this year until July 26.

And did you know that Aurora Labs has a special activity dedicated to discovering the midnight sun differently? Check it out here!

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

And, by the way, the opposite of the polar day is the magnificent polar night! Have you ever experienced one or the other?

During the polar day, the Sun never sets below the horizon.
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!