13 times per century
Thanks to Squarespace for sponsoring today's article. On November 11, 2019, Mercury will cross the sun from our point of view on earth. This will not be noticeable to the naked eye, but with the right equipment you can see the silhouette of Mercury against the sun.
I'm Alex McColgan, and you're watching Astrum, and in this article I'm going to go over the what, when, and where of this transit and also explain why it doesn't happen much more regularly. A transit is when a celestial object passes in front of another object from our perspective, but perspective makes the next body too small to eclipse the farthest one. So while the moon eclipses the sun, only Mercury and Venus are at this distance to be able to pass the sun.
This is because they are the only planets that orbit closer to the sun than we do. When the earth and either Mercury or Venus align between us and the sun, this is called a subordinate conjunction - the sun is a planet, the shorter its year means for Mercury that a year is only 89 earth days. This means that in the time it takes the earth to circle the sun once, it will dash to the sun a few times.
If so, then why doesn't Mercury transit happen a couple of times? Times a year? This is because, while planets in our solar system all orbit roughly at the level of the solar system, not all of them have perfectly flat and circular orbits. Their orbital eccentricity is not great, but it is enough if you take this into account to explain the great distances between these relatively small objects. So for most orbits, from our perspective, Mercury is either too high or too low to be directly in front of the sun.
Every now and then, however, the alignment is just right for a transit to take place, unlike Venus, which has a very fixed time span between transits, 2 eight years apart and then a long gap of 121 and 105 years. Unfortunately, if you wanted to see a Venus transit but haven't done it yet, you've probably missed it forever, the next one is now a hundred years away. Mercury on the other side has a strange pattern, although there are usually around 13 transits per century .
Interestingly, each Mercury transit only happens in May or November. If that's what you want to see, I wouldn't miss the one this year or you will have to wait 13 years. These articles you see now were captured by the Solar Dynamics Observatory, a NASAspace telescope that constantly monitors the sun, from the last transit in 2016.
So how can you see this transit for yourself? The first stop I would suggest is to see if there are any local astronomy clubs nearby. They are usually very interested in observing such phenomena and are generally happy to see the public come on such occasions, if this is not for you, you can observe it with a telescope. Note, however, that you will need to use a solar filter or you will definitely be self-dazzling, you need to see if your telescope can use a solar filter attachment, I wouldn't strongly recommend using a homemade one just in case it's not done right and you're still damaging your eyes.
You can use the same glasses that you used to view a solar eclipse, although you need to have pretty good eyesight to see Mercury for what it is so small. My final suggestion would be to build my own optical projection camera. A simple pinhole camera won't work in this case because Mercury is again too small.
All you need are two thick cardboard boxes and a pair of binoculars. Hold the binoculars in place and cut holes in one of the sheets so you can attach them seamlessly around the lenses. This is to block the sunlight from everyone but the lens.
Block one of the lenses, you don't need two projections. Using the second sheet, hold it about 30 cm from the viewfinder and you should get a projection of the sun. Adjust the position of the blade and adjust the focus on the binoculars until you get a nice, sharp image.
With a bit of luck, you can see the silhouette of Mercury! But here too, don't look at the sun itself through the binoculars, just look at the projected image. So November 11th, 2019. When can I see it? Well, that depends on where you are in the world.
It starts at 12:35 UTC for Europe. Africa and the Middle East. During the day it will become visible in America.
Sorry Russia, Asia and Australasia, you are out of luck. When you are at the South Pole, you have a good view from start to finish. So there you have it, Mercury's upcoming 2019 transit.
Hope you will enjoy it and enjoy some of the more unusual sights of our solar system! Thanks again to Squarespace for sponsoring this article. Squarespace gives people a powerful and beautiful online platform from which to build your own website. I've had good experiences with their platform myself for building my own website and I have to say how easy it is for me to create a professional looking website with their templates and tools is impressive, I can easily link my social media accounts and emb ed articles seamlessly, so if you want to create a website, give it a try! If you use the link squarespace.com/astrum you can try it for free and get 10% off your first purchase, thanks for watching ! Don't forget to subscribe so as not to miss any future space articles.
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Mercury transits occur 13 times per century, and the next one is slated for Nov. 13, 2032, although that one won't be viewable from the United States. Mercury transits typically happen in May or November. That's mainly because of how Earth aligns with Mercury's orbit. .
A transit of Mercury across the Sun takes place when the planet Mercury passes directly (transits) between the Sun and a superior planet, becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Mercury appears as a tiny black dot moving across the disk of the Sun.
Mercury began its journey across the sun at 7:35 a.m. EST (1235 GMT), and the entire transit took roughly 5 and a half hours, ending at 1:04 p.m. EST (1804 GMT), according to NASA. The planet currently looks like a tiny, traveling blemish on the sun's face as it passes in front of the sun. .
Mercury is the closest planet to the Sun. As you would expect, this makes it pretty hot. But it's pretty cool too.
There are seven solar system objects in the sky with the naked eye: Mercury, Venus, Mars, Jupiter, Saturn, the Sun, and the Moon. Seven. Each of them was associated with a god in ancient times.
Mercury was the Roman messenger of the gods, light-footed - he literally had wings on his shoes - and a quick traveler. For anyone who has seen Mercury in the sky, this belonging to the Swift God is no surprise. The planet Mercury moves fairly quickly and visibly changes its position relative to the background stars even after a single night.
Despite its speed, the planet never gets very far from the sun. At best, it can reach a distance of about 28 °. This is roughly three times the apparent size of your outstretched fist.
In 1639, Italian astronomer Giovanni Zupi used a telescope to observe Mercury, and he discovered that it goes through a full phase cycle over time, just like the moon that can happen when Mercury orbits the sun rather than the earth - another Check mark in the column for heliocentrism, which kept looking better. And of course things really are like that. Mercury is the innermost of the planets in the solar system.
It orbits the sun at an average distance of about 58 million kilometers, about a third the distance of the earth from the sun. That's why we never see his tray far from the sun. From our point of view, it keeps its smaller orbit closer to our star.
That's why we see it so quickly; it is closer to the sun, so the gravity from the sun is stronger and therefore its orbital speed is faster than that of the earth. It orbits the sun once every 88 days. And that is also the reason why we go through phases.
When it's between us and the sun we look at its dark side, and when it's on the other side of the sun we look at its fully lit half. In between it goes through the same phases as the moon: half moon, half full, arched etc. Not that this is so easy to observe.
Since it is never far from the sun, it is always low on the horizon after sunset or before sunrise. When we watch it, we look through all the dirt and turbulence in our air, so it's usually pretty blurry. To make matters worse, it is a tiny planet that is only about 4900 kilometers in diameter and about a third the width of the earth.
One benefit of all of this is that due to its proximity to the sun, it is heavily lit and can be quite bright even near the horizon. If you ever get the chance to see it, really do it. It's pretty cool.
Mercury's orbit is strange. It has the most elliptical orbit of any planet, ranging from 46 to nearly 70 million kilometers from the Sun. When it is closest to the sun, it receives more than twice as much light and heat as it is furthest away! Mercury is too small and difficult to observe to see surface features on it, which made it impossible to figure out how long it was for a long time Day is.
Astronomers believed that the tides of the sun had fixed the rotation of Mercury so that its day corresponded to its year, just as our moon rotates once for each orbit of the earth. However, in 1965, astronomers were using Doppler radar to observe Mercury and measure its rotation directly, and they got a surprise: its day was only 59 Earth days, not 88. But that, too, is a respectable number.
More precisely, the actual length of the Mercury year is 87.97 days and the actual length of its day is 58.65 earth days.
If you divide these two numbers, you can see that their ratio is almost exactly 2/3! It turns out that there is more than one way to lock a planet's rotation to its orbit. Remember earlier when I said that Mercury's orbit is highly elliptical? The tides from the Sun are much stronger on Mercury when it is in perihelion, the point in its orbit closest to the Sun, than in aphelion, which is the furthest point in its orbit. After Mercury first formed, the sun's tides slowed its rotation, just as the Earth's tides on the moon slowed the moon down.
But at some point the rotation of Mercury slowed to happen 2/3 of its orbital period, one side of Mercury is facing the sun. Then, about 88 days later, it approaches perihelion again. But it's rotated 1.5 times, and that means the exact opposite side of Mercury is facing the Sun on this closest approach. 88 days later, Mercury spun again 1.5 times and the whole thing repeats itself.
It turns out that this is a perfectly legitimate stable configuration, just like the one-on-one spin / orbit setup. The way physics works are tides like simple multiples. When the day became 2/3 of the year period, forced by Mercury's elliptical orbit, the tides stopped slowing and things have been so very, very strange day on Mercury ever since.
If you stay in one place, it takes the sun two Mercury years, 176 days for the sun to go around the sky once! That's because if you're on the side of Mercury facing the Sun at one perihelion, the other side is facing it a year later. You can only watch the sun again after the second year has elapsed. But it gets stranger.
Mercury's spin is constant; it doesn't speed up or slow down. However, its movement around the sun is faster in perihelion than in aphelion. In aphelion, Mercury's spin is slightly faster than its orbital speed, so the sun moves quickly west across the sky.
But in perihelion, the movement of Mercury around the sun more than compensates for its rotation, so that the sun appears to be in the sky and actually moves backwards for a few days! Then, as Mercury moves away from the Sun, its orbital speed slows and the Sun begins to move west again as the planet's rotation dominates. If you are in exactly the right place on the planet's surface, you can actually watch the sun rise, slowly, stop, set again, and then rise again! And you think time zones on Earth are torture. Mercury is difficult to observe from Earth, and much of what we know about it can be traced back to observations from space probes that were sent there.
Mariner 10 made three flybys of Mercury in the 1970s and mapped about half of the surface. We learned that it had almost no atmosphere and was therefore unsurprisingly covered in craters. In 2011, the MESSENGER probe entered orbit around Mercury after a series of closeflybies.
The images it brought back were breathtaking, revealing a world that has seen much beatings over the eons. It's covered in craters, pole to pole, a few hundred kilometers in diameter. The largest is called Caloris Basin, an incredible impact of 1,600 kilometers in diameter.
There are also some smoother plains on the planet's surface that appear to be older than the crater the regions. These plains are covered with cracks called rupes. These are compression folds, like folds on a dried-out fruit peel.
Apparently, the planet was shrinking as the interior of Mercury cooled after its formation, and the crust also cracked when it tried to shrink. Several of the craters have extensive systems of rays. As on our moon, these occur when long clouds of material are thrown out during impacts, which then settle on the surface.
One of my favorite things about Mercury: craters are named after artists. Musicians, writers, painters and more, so we have craters like Botticelli, Chekov, Debussy, Degas, Okyo, Sibelius, Vivaldi and Zola. There's even one named Tolkien! By diving below the surface, we can only deduce the internal structure of Mercury.
But the planet is dense, almost as dense as the earth. We know the surface is rocky, so it must have a large iron core that is much larger in relation to the planet than that of the earth. The core of Mercury can reach ¾ of the way to the planet's surface! Why does it have such a high iron content? Mercury may have formed as a larger planet and then was blasted by a huge grazing impact that blew away the lighter materials that had risen to the surface, leaving the denser part behind.
Or maybe the heat of the still forming sun has evaporated the lighter materials from their surface. Mercury has a measurable magnetic field, which is a bit of a surprise since it rotates so slowly - rotation plays a big role in the sun and earth's magnetic fields. But that goes with the fact that so much of its interior is molten iron; the larger core can enable a stronger field despite its slow spin.
It doesn't have much of an atmosphere, but there is a trace of one, largely due to its magnetic field, which traps the solar wind, and due to material being thrown up from the surface after violent impacts from comets and asteroids. Much of this material, blown away from the surface, escapes the planet and is blown away by the solar wind and pressure from sunlight. It forms a long, comet-like tail that is tens of millions of kilometers long.
This tail is made up of elements like sodium, calcium, and magnesium, a material known to be abundant on the surface. Speaking of which, here's a fun fact: pound for pound, impacts on Mercury are more severe than on Earth. Mercury has weaker gravity, so it doesn't attract impactors as much as Earth, but it orbits the Sun much faster than Earth, so asteroids and comets tend to hit at higher speeds.
This increases the explosive energy and makes the craters larger. And there's one more surprise that Mercury has, and it's really surprising: even though it's so close to the Sun and has a surface temperature of 430 ° C - 800 ° Fahrenheit - astronomers have found water, ice on Mercury! It exists in the depths of deep craters near the poles of Mercury, where sunlight never gets. These are called 'cold traps' and the temperatures there do not rise above -170 ° C.
It is not certain where the water is coming from, but it is likely from comets and asteroids that hit the planet and scattered the water across the surface. Of course, in the harsh heat, that water just goes and goes away. But in these deep craters it can persist and accumulate for eons.
There may be billions of tons of it! It's bizarre to think that in one of the hottest places in the solar system there can be conditions that make cold ice possible, but one thing we've learned time and again about nature: it has a lot more imagination than we do. Today you learned that Mercury is the closest to the sun. It is evacuated and dense and covered with craters.
Its rotation is tied to its orbit in a ratio of 2 to 3 and, along with its elliptical orbit, makes a day on Mercury very long and very strange. And although it is very hot, there is actually water ice in deep craters at its poles. Crash-Kurs Astronomy is produced in collaboration with PBS Digital Studios.
Visit her channel to discover more great articles. This episode was written by me, Phil Plait. The script was edited by Blake de Pastino and our consultant is Dr.
Michelle Thaller. Directed by Nicholas Jenkins, edited by Nicole Sweeney, and the graphics team is Thought Café.
The order of the planets in the solar system, starting nearest the sun and working outward is the following: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and then the possible Planet Nine. .
During this retrograde cycle, Mercury will be backspinning through its home sign of Gemini and because it's also currently Gemini season 2021, the retrograde effects may be amplified. .
So with Mercury in Cancer, their approach is to feel out the dilemma. They are more emotional than other star signs. So they focus on the mood of a situation rather than a logical explanation. They trust their gut reaction above their head.
When Mercury is in Cancer, it has a subtler approach to communication. Instead of relying on the spoken word, it is more intuitive and emotional based. Cancer is a mute sign because it belongs to the water element. Therefore, you can expect to struggle with how to express your sentiments over the next few weeks. .
No, Mercury has been visited by spacecraft from Earth, but no human has ever gone into orbit around Mercury, let alone stepped on the surface. However, the temperatures on Mercury are much greater. During the daytime, the surface of Mercury at the equator rises to 700 Kelvin (427 degrees C). .
A planet's day is the time it takes the planet to rotate or spin once on its axis. Mercury rotates very slowly compared to Earth so a day on Mercury is much longer than a day on Earth. A day on Mercury is 58.646 Earth days or 1407.5 hours long while a day on Earth is 23.934 hours long.
On Mercury a day lasts 1,408 hours, and on Venus it lasts 5,832 hours. On Earth and Mars it's very similar. Earth takes 24 hours to complete one spin, and Mars takes 25 hours. The gas giants rotate really fast.