When you look at the Moon, sometimes, besides the illumination of the crescent of the moon, you are able to see the rest of the disk of our planet’s natural satellite. That dim illumination of the darker disk is called earthshine.
What causes it?
But what causes this illumination? We all know that sunlight hits Earth, there’s no question there. But Earth is a globe, and a fraction of the light that hits our planet, is reflected back into space (and in the scientific literature is known as earthlight). Some of this light that gets reflected into space, hits the moon as well, and it is this what causes the lighting up of the dark disk besides the crescent moon. And this dim light gets reflected back to Earth and it’s what our eyes percieve.
Sunlight hits Earth (yellow arrow). A portion of this light gets reflected back into space (white arrow) and can cause earthshine, which is reflected back to Earth (grey arrow).
When to look?
When the moon is full, we’ve all seen that it can light up pretty well entire regions on our planet, from where the full moon is visible. From the surface of the moon, Earth can be also illuminated by the Sun (just like other planets of our Solar System). When Earth is “full” (from the moon’s night sky perspective), it means that our planet can light up an entire region on the moon as well. Why would it only be the other way around, anyway? This also means that earthshine is visible at its maximum when Earth is almost “full”, so, when the Moon is a very thin crescent.
Planetshine
This phenomenon occurs on other celestial bodies as well, not only on Earth! When a planet is illuminated by its star, and if that planet has a natural satellite, the phenomenon takes plase in the same waym just like in the Sun-Earth-Moon system. The only difference is the name – it’s generally called planetshine. And, of course, light reflected from a planet in general, is called planetlight.
Far away from mass tourism and way off the beaten track, Vadsø is a small municipality in the Varanger peninsula, located in the Finnmark county in the Norwegian Lapland, in northern Scandinavia.
The town of Vadsø has lots to offer to people visiting: breathtaking landscapes, small lively neighbourhoods, many cultural monuments or typical arctic phenomena, such as the Northern Lights and the Midnight Sun, in a total absence of atmospheric, light and phonic pollution. Here, live life differently while immersing yourself in the true Arctic rhythm. I tried to capture a bit of everything in my newest video, dedicated to this beautiful place! Check it out and discover also why Aurora Labs is located specifically here!
Visit Vadsø with Aurora Labs
For more information about Vadsø, check this link!
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!
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? 😉
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.
