Surprise Surprise, the Asteroids Visit

     Dear Diary...

     An asteroid will make a near-miss-fly-by today (january 27, 2012) around 1600 GMT, you can convert that to your timezone here.
     Now, what's an asteroid? it's a bad neighbor, and basically a body that orbits the Sun. Astronomers also like to call them planetoids or NEOs (Near Earth Objects). The appellation 'asteroid' was proposed by Herschel, the man behind the discovery of Uranus in the 1800s. They're scattered around our solar system like concentric circles around the sun, forming belts. For example, the Asteroid Belt, forming a ring of asteroids between Mars and Jupiter, and the Kuiper Belt, an other ring that's beyond Neptune.

Asteroid belt: ring of asteroids between Mars and Jupiter

   
     Let's talk about crazy numbers, the Asteroid belts contains nearly 1.5 million asteroids with diameters larger than 1 Km (3,280 feet) and millions of smaller ones, and that's just one the belts. More than half the mass of the main belt is contained in the four largest objects: Ceres, Pallas, Vesta, and Hygiea. All of these have mean diameters of more than 400 km.
     The most recent visitor is asteroid 2012 BX34 (obviously, astronomers shouldn't be allowed to name things) and it's only 11m long in diameter (36 feet), about the size of a city bus, and it's going to pass within about 60,000 Km of Earth, that's about less than the fifth of the distance from the Blue Planet to the moon. No risk of 2012 Armageddon there.
Click here for a video from space.com simulating the asteroid's visit.
     2012BX34 is one of the 20 closet asteroid approaches, it's traveling at the speed of 8,9 Km/s (20,000 mph), its brightness is identical to the maximal brightness of Pluto, making it impossible to see with the naked eye.

     These chains of rock are the way they are due to the gravitational forces exerted by the Sun and Jupiter, obviously because of their masses and relative closeness to the belts. Moreover, there's a class of asteroids called the Potentially Hazardous Asteroids, think of those as harmless stalkers, these are a bunch of rocks moving around the sun at a distance quite similar to the Earth's, they're not necessarily going to hit us, but they're there. Astronomers and other cool scientists have telescopes around the earth, scanning the sky along the ecliptic, discovering new PHAs and calculating their orbits. The biggest threat in the past decade was probably the 2004 asteroid that was 30m long in diameter, that announced its visit only three days early and passed by the Earth at a distance that's tenth the distance between the Earth and the moon.
     According to NASA, (in september 2011) there are 980 large near-Earth asteroids.

    For a tour of the asteroid belt and the rotation of some of the most popular asteroids, here's a video with some good greek music in the background, make sure you watch it.

References and credits:
www.bbc.co.uk
www.space.com
www.youtube.com
thewatchers.adorraeli.com
jpl.nasa.gov

Venus, the Blue Planet’s Twin

Venus Planet ID

Planet size comparison, from left to right: Mercury, Venus, Earth, Mars

     Dear Diary...

     Let's talk about the second rock from the Sun, Venus. Now, why did I call it Earth's twin? First of all, its size of course, and secondly, its closeness to us, we get closer to Venus that we get close to any other world in the Solar System. When Venus is illuminated by the Sun, we see it as we see the moon, as a crescent. When the Sun's light doesn't reach it, however, we see it like a really bright flickering star. 'Flickering' is because of our atmosphere, think of it like an optical illusion. 'Really bright' is because the planet's constant volcanic activity.

Its glow has affected many human culture over the centuries.

• In Babylonian mythology, the planet is Ishtar, the personification of womanhood and the goddess of love. 
• In Greek mythology, the planet is Aphrodite, the goddess of love, beauty, pleasure and procreation,
• In Phoenician mythology, the planet is Astarte, goddess of fertility, sexuality, and war.
• In Roman mythology, the planet is Venus, the goddess beauty, sex, fertility, prosperity and military victory.
• In Persian mythology, the planet is Anahita, a name that has the following meanings: divine, pure or immaculate, and mighty. She was a worshipped maiden.

     Wow, were these people wrong. Venus is as hostile as a place can be. To kick things off, it's the hottest planet in our solar system (you might think it's Mercury, but the green house effect on Venus tilts the odds). Here's a list of how Venus might try to kill you:

• The atmospheric temperature is so high, it could melt Iron 480 °C (894 °F), so standing there could be somewhat...unpleasant. Making things more fun, are plate tectonics, not also does the melting surface beneath you move all the time, the heat weakens the entire crust, and there are times of intense volcanism where the whole terrain gets resurfaced. The last time Venus resurfaced was 5 million years ago, but I don't advise you to visit anyway.
  
• There is rain on Venus! Rain made of sulfuric acid, also called oil of vitriol, and it's what is used for lead-acid batteries for vehicles. Sulfuric acid exists as a liquid, and thick sulfuric acid clouds completely obscure the planet's surface when viewed from above, making it very hard for astronomers to map the terrain. The permanent Venusian clouds produce a concentrated acid rain, as the clouds in the atmosphere of Earth produce water rain.
• The atmospheric pressure on Venus is close to 92 atmospheres. The atmospheric pressure on Earth is 1 atmosphere. To give you a better idea, on Earth, if you ever go diving, the atmospheric pressure increases by 1 atmosphere for every 10 meters you dive. So, to experience what it would be like to stand on Venus, you'll have to go nearly 1 kilometer below the water's surface.
• The Venusian magnetosphere is not as strong as you'd think it would be, UV light will probably grill you. The Sun-Venus interactions are always going strong. There is a satellite trying to acquire more information about the planet's atmosphere and magnetic field, it's ESA's Venus express, click here for more info on the artificial moon.
• Super fast storms, storms that go around the whole planet in 4 days, and remember, it's a planet almost as big(or as small) as the Earth! Winds are 100m/s (220 mph) fast on average.

     By all means, never visit the pretty goddess.

Venusian Surface

     Venus has a few astronomical particularities. First of all, a day on Venus is longer than year on Venus. (The time the planet needs to rotate around its axis is greater than the time it needs to rotate around the sun, so it's less than a Venusian sunset per year). A side from the fact that it rotates excruciatingly slowly, it's one of the two planets in our solar system that rotate clockwise (the other is Uranus). Why? Astronomers are not sure, but it's probably due to a huge collision that knocked it out and rotated it backwards, maybe with a moon that Venus might have had in the past, or a really big asteroid. The sad thing is, it's impossible to prove a collision because like I said earlier, the planet keeps resurfacing. Other theories include the planet flipping, in a way that its north pole is now its south pole and vice versa, or due to plate tectonics, gravity and tidal forces.

     Finally, make sure you observe it when you get the chance, you can see it with the naked eye, and right now (January 2012), it's quite close to the moon every evening, right after sunset. I'll publish an article on the transit Venus before its occurrence in early June 2012, until then, happy stargazing.

Reference and credits:

www.space.com

www.esa.int

www.nasa.gov
wikipedia.fr
www.pantheon.org

Aurorae, the dancing rainbows

     Dear diary...

     An aurora is a natural light display in the sky, caused by the collision of particles with the Earth's high atmosphere. These charges particles that hit our Blue Planet originate from the sun, or CMEs (Coronal Mass Ejections) to be more precise. It's a simple physical phenomena; the earth has a magnetic field line, and when high-energy particles, or in fact any particles, from the solar wind interact with this magnetic field, the charged particles will tend to follow the magnetic field lines back down toward the surface of the earth. As they collide with things in the atmosphere, you end up with a light show.

     Solar activity is really high right now (January 2012) and on its way to reach its peak around Pebruary 2013, the more matter it chunks our way, the more nighttime entertainment we get! Aurorae (pronounced orori, FYI, that is not an actual word) are only visible in high latitude regions, like Antarctica, Alaska, and Norway, and can reach lower latitudes (like Scotland and Ireland, and as far as Arizona during one huge solar storm in January 2012) when the CMEs are more massive.

     The sight of an Aurora is pure magic, it's how you'd imagine angels dancing, or rainbows trying to play music, just curtains of colorful flames. Watch the following video, my personal favorite time-lapse video, so far, showing a Finnish Aurora:

     Aurorae also occur on neighboring planets, the ones that have an actual magnetosphere like Jupiter and Saturn, and some their moons like Io and Titan, and unlike Mars. Pictures are similar to those of the Earth taken by the ISS (International Space Station).

Aurora on Jupiter's north pole

Aurora on Earth, picture taken by the ISS

     The light show actually comes from stuff that’s in our atmosphere. As these high-energy particles are blasting through our atmosphere, they have a chance to hit an atom here or there. Our atmosphere is filled with things that give off light when you hit them just right. We have atomic oxygen which gives off red light. We have molecular nitrogen which is blue and molecular oxygen which is green. What happens is you’ll end up with one of these high-energy particles whipping itself into say an atomic oxygen molecule. And when this happens, one of the electrons in the atomic oxygen molecule can jump to a higher energy level. So now we have excited atomic oxygen in the upper levels of the atmosphere. That excited atomic oxygen can only stay excited so long. Then it drops to a lower energy level. When it drops to a lower energy level, it gives off a very precise photon of color, a very precise, in this case, red photon of color. And that is what we see as the red aurora that seems to always be the northern-most part of the aurora. That is where the aurora has first started in the highest parts of the atmosphere.

     Contrary to popular belief, these mesmerizing sights aren't harmful to Earth's people. They may be harmful to astronauts in some cases, and satellites lurking in space, though when a CME is emitted, satellites are ordered to shut themselves off as a precaution.

     This physical phenomena has mesmerized humans for centuries, in ancient Roman mythology, Aurora is the goddess of the dawn, renewing herself every morning to fly across the sky, announcing the arrival of the sun. The persona of Aurora the goddess has been incorporated in the writings of Shakespeare, Lord Tennyson and Thoreau. In Norse mythology, the Valkyrior (aurorae) are warlike virgins, mounted upon horses and armed with helmets and spears.


     On my to-do list, there's an Aurora-viewing mission that I want to accomplish as soon as I'm done with college, it should be one of your goals too! Even if the best places to view auroras are miserable, cold, and moonless.

Cool tip: some auroras are visible during flights, while you're in a plane!

'BOOM' goes the Sun

Dear Diary...

     If you live on planet Earth (I’m assuming you do), every one of your celestial neighbors, like the moon, the sun, and Venus visits your sky following some kind of cycle. Let’s talk about the solar cycle! First, an infographic:

     So, the cycle is 11 years long and noticeable by a quiet phase, and an active phase, which are the lowest, and highest solar activity points. By solar activity, I mean the substance that the Sun chunks towards us. The Sun interacts with our planet by sending out energy, for which the technical term is solar flares, that need almost eight minutes to reach us, and/or by throwing matter our way, a large amount of charged particles, what astronomers call a coronal mass ejection, or CME to make things easier, these are classified as following: A, B, C, M and X (X being the greatest). Predictions of solar activity can be found here.

     Solar maximum is that point when the Sun’s magnetic field is its most tangled, when you have field lines that are poking through the surface, and when you see sunspots. The sunspots often come in pairs, and one of them is the point where the field line is coming through the surface, and other one is the point where the field line is going back into the surface, and as the field line twists itself around, it actually channels plasma, and so these footprints can be connecting plasma loops, they can be the cause of giant CMEs.

Now, coronal mass ejections are basically the big, angry brother of solar flares. So solar flares are fairly well understood; they’re tied to magnetic field lines, they’re rearranging. Coronal mass ejections we’re still trying to sort all the things that trigger them. They’re also triggered at times by breaking the field lines, breaking the tangled up field lines, clusters of sunspots, and when these go off, we also can get a blast of particles heading towards us at various different velocities. So sometimes we’ll only get half a day’s warning that there’s this cloud of particles heading toward us, and sometimes it’s a couple of days, and these are the things that we do have to worry about because, well, all of those ionized particles, those can pose danger to astronauts. All of the high energy radiation tangled up with this –that can pose danger, well, to just about everything on orbit. Luckily, the light gets to us before the particles, so thanks to spacecraft like STEREO and SDO that are watching the Sun for us… SDO actually takes an image of the Sun every 10 seconds. These spacecraft are allowing us to do better modeling, are allowing us to see the stuff on our way, and as we continue to watch these things, it’s a matter of building up models, of “if we see this, then this is going to occur; if we see this, then this other thing is going to occur.” And between STEREO and SDO’s constant vigilance, we’re getting better at predicting when large solar flares are coming our way.

Watch this video, it pretty much tells you everything you need to know in a matter of minutes:

References and credits:

nasa.gov

astronomycast.com

universetoday.com

space.com

youtube.com

http://helios.gsfc.nasa.gov/cme.html