“A rose by any other name…”

In my last post, “It seems the sky is falling…”, I talked about the Russian meteor event and flyby of asteroid 2012 DA14, both of which occurred on Friday, February 15, 2013. In that post I talked a lot about the various terms of things in space that can enter the Earth’s atmosphere and ultimately cause an “impact”. But there are a lot of terms and some of them have very minute differences, so I figured I’d devote a post just to explaining these terms. Specifically, I’d like to look at a few differences.

“Meteoroid” vs. “Meteor” vs. “Meteorite”

These words all share the same root, the Greek word meteōros, meaning “suspended in the air”, and look very similar, but they do mean different things. To start off, let’s think of a small piece of rock in space. We don’t care what kind of rock it is or where it comes from, let’s just call it a small rock. Now, let’s say that small rock is happily zipping around the solar system, obeying the law of gravity as it orbits the Sun, when suddenly it gets too close to Earth and the gravitational pull of the planet sends tugs it out of its original orbit and towards our planet. Now, that small piece of rock that’s on it’s way into the Earth’s atmosphere, that’s a “meteoroid”. Once that “meteoroid” hits the Earth’s atmosphere travelling at high speed it’s going to heat up and leave a trail in the sky. That heating up and the resulting streak in the sky is a “meteor”- commonly referred as a “shooting star”. If you get a whole bunch of associated “meteoroids”, say a whole bunch of little pieces of rock left over from an asteroid or comet that passed by, that enter the atmosphere at the same time, creating meteors, that’s called a “meteor shower”. So, the “meteoroid” is the small rock that causes streak of light and the “meteor” is the actual visible streak we see. Now as that “meteoroid” is hurtling through the atmosphere and heating up, it can literally blow up. That huge flash that’s caused by the disintegration of the “meteoroid” is known as a “fireball” and really bright “fireballs” are known as “bolides”. That huge flash of light is usually associated with a large deposit of energy into the atmosphere that causes a pressure wave like to ones seen in Tunguska and Chelyabinsk.

A meteor or “shooting star” streaking across the sky is really a piece of debris burning up in the atmosphere. Credit: Wikipedia

The solar system is full of little pieces of debris moving really fast and without the atmosphere that debris would constantly be pummeling the surface of the planet…and us. So the atmosphere protects us. Things are constantly entering the atmosphere and burning up, creating “meteors”. Most of these “meteoroids” are about the size of a pebble- much to small to reach the Earth’s surface. But it does happen occasionally. When large objects enter the atmosphere and make it down to Earth, that remaining piece of rock that reaches the ground is known as a “meteorite”. So yeah, if you’re one your way to work in the morning and see that there’s a huge piece of rock sitting on your car, that’s probably a “meteorite”…or there’s someone who really doesn’t like you. Don’t worry though, as Bad Astronomer Phil Plait writes, only one person has ever been hit by a meteorite and that occurred in Alabama in 1954.

This Canyon Diablo meteorite was part of the 50-meter asteroid that formed the mile-wide Meteor Crater in Arizona. Credit: Wikipedia

Now, not all “meteors” and “meteorites” are caused by natural objects in space. Think about all of the satellites and “space junk” orbiting the Earth. If any of that space junk were to re-enter the atmosphere it would burn up, just like a space rock, and cause a meteor. And another, less appealing example is astronaut waste. On the now-retired Space Shuttles, the urine was expelled out into the upper atmosphere to burn up/evaporate– this actually created a visible glow. Solid waste on the Space Shuttles was collected and removed once the Shuttle returned to the ground, unfortunately that’s not really an option on the International Space Station (ISS), where astronaut waste is stored, then loaded into a disposable space probe and ejected out to burn up in the atmosphere. So yeah, next time you wish on a shooting star, just think that it might actually be astronaut poop.

“Comet” vs. “Asteroid”

Okay so now we’ve talked about the differences between the things that enter the atmosphere. But beyond man-made sources, where do those “meteoroids” come from? Many of them are from rocky, metallic objects in the solar system known as “asteroids”. What are asteroids? According to NASA:

“Most asteroids are made of rock, but some are composed of metal, mostly nickel and iron. They range in size from small boulders to objects that are hundreds of miles in diameter. A small portion of the asteroid population may be burned-out comets whose ices have evaporated away and been blown off into space. Almost all asteroids are part of the Main Asteroid Belt, with orbits in the vast region of space between Mars and Jupiter.”

Most asteroids are actually leftover bits and pieces of planets that weren’t able to coalesce under gravity. As the NASA page describes, most asteroids live in the Asteroid Belt that orbits between Mars and Jupiter. However, as those asteroids travel around the Sun, they can bump into each other, causing a rogue asteroid to leave the Asteroid Belt and traverse the solar system. Sometimes those asteroids fall into the Sun, sometimes they collide with Earth or other planets.

Vesta, one of the largest asteroids in the solar system, was recently studied by NASA’s Dawn mission. Dawn was the first spacecraft ever to go into orbit around an asteroid. Credit: Wikipedia

So what’s the difference between an asteroid and a comet? A “comet” is an icy body that lives out in the farthest regions of the solar system. There is belief by scientists that many comets primarily live in a region at the edge of the solar system known as the Oort Cloud. As these icy bodies come into the inner solar system and approach the Sun, they increase in brightness as the heat from the Sun causes the ice to melt and reflect sunlight. Comets are generally much easier to view than asteroids due to the high reflectivity of the water vapor it releases as they travel through the inner solar system. Generally comets that pass by the orbit of the Earth leave a debris trail in their wake. When the Earth’s orbit takes it through one of those debris trails, it causes a meteor shower.

Comet West made a spectacular show for skywatchers in March 1976. This image shows a great example of the two types of tails that comets often have. One tail is caused by water vapor coming off from sunlight and the other is ionization caused by the solar wind of particles streaming off of the Sun. Credit: APOD/NASA

So comets are mostly icy bodies that live out at the very edge of the solar system and asteroids are rocky, metallic bodies that generally live in the Asteroid Belt in the region between Mars and Jupiter.

So what did we learn?

So let’s review in this handy table made by the great folks at NASA’s Near-Earth Object Program:

Asteroid A relatively small, inactive, rocky body orbiting the Sun.
Comet A relatively small, at times active, object whose ices can vaporize in sunlight forming an atmosphere (coma) of dust and gas and, sometimes, a tail of dust and/or gas.
Meteoroid A small particle from a comet or asteroid orbiting the Sun.
Meteor The light phenomena which results when a meteoroid enters the Earth’s atmosphere and vaporizes; a shooting star.
Meteorite A meteoroid that survives its passage through the Earth’s atmosphere and lands upon the Earth’s surface.

Advertisements

It seems the sky is falling…

Imagine driving in your car on a lovely Friday morning and seeing a flaming ball of death streaking across the sky and coming, as best you can tell, right at you.

This view from a Russian dashboard camera shows a terrifying view of the fireball as the meteoroid entered the atmosphere and hurtled over the city of Chelyabinsk. Credit: Discovery News

That’s what terrified citizens in the lovely Russian city of Chelyabinsk experienced on the morning of Friday, February 15. The multitude of videos and photos of this meteor are simply horrifying since many of them give the impression that this huge chunk of flaming interplanetary death is about to smash right into the camera. Not only did this fireball make a scary visual impression, but it packed a very literal punch as well. As the meteoroid hurtled through the atmosphere at 40,000 mph, the heat and pressure it felt caused it to break apart with a huge amount of energy, the equivalent of 470 kilotons of TNT (or 30-40 times the power of the atomic bomb dropped on Hiroshima). The deposition of that huge amount of energy into the sky caused a pressure wave that blasted the city. Over 1,000 people were injured by the blast, mostly due to cuts and scrapes from glass as windows shattered. Scientists have now come to the conclusion that the initial object was only 17 meters wide– that’s about the size of a tractor trailer. That’s pretty small cosmically speaking. Imagine the damage that could have been inflicted if something larger had hit the atmosphere. The last time a meteor had significant large-scale impact was in 1908, again in Russia. This impact, known as the “Tunguska event“, is the largest impact ever recorded- 20-30 times larger than the one that happened this month. This meteoroid, which is estimated to have been about 100 meters wide (the size of a football field), blew up in the air and released 10-15 megatons of energy, leveling 830 square miles of trees. Witnesses to the event said that the heat and pressure from the explosion made their skin feel like it was on fire.

The 1908 Tunguska event, the largest impact near or on Earth ever recorded, leveled trees over 830 square miles. Credit: nightsky.org

Luckily the 2013 Russian meteor was much smaller, so windows got knocked out but buildings weren’t leveled. The object was actually so small that astronomers didn’t even see it coming. NASA has a whole division of people who track objects that could potentially come close to Earth, it’s known as the Near-Earth Object Program. Unfortunately, for scientists to be able to see an object it needs to be large enough to reflect an observable amount of light. That didn’t happen here.

The meteor also came as a bit of a shock since scientists were so focused on another Near-Earth Object called 2012 DA14. This 45-meter wide asteroid was scheduled for a flyby of Earth on the same day, February 15. This relatively small piece of space rock flew closer to the Earth than any other celestial body. It was 17,200 miles away at its closest approach, that’s closer than satellites in geosynchronous orbit and much, much closer than the Moon. Although scientists were certain that DA14 wouldn’t impact the Earth, they were very excited to use the close flyby as an opportunity to study the asteroid.

This collage of 72 individual radar-generated images of asteroid 2012 DA14 was created using data from NASA’s 230-foot Deep Space Network antenna at Goldstone, CA. Credit: NASA

Of course it was ironic that after weeks of assuring the public that there was no threat of an impact from DA14 another huge impact happened in Russia the same day. Scientists from NASA’s Meteoroid Environment Office concluded that the Russian meteor and DA14 were totally unrelated, having come from two very distinct trajectories/orbits. This means it was a huge cosmic coincidence that they just happened to occur on the same day…weird.

This plot of the orbits of the Russian meteor and asteroid 2012 DA14 show that the two bodies came from very different parts of the solar system and were unrelated. The Russian meteoroid most likely originated from the Asteroid Belt out past Mars. Credit: NASA/Space.com

The world will not end today…

Okay, this is really getting pretty infuriating. I have friends, family, and strangers messaging me about when the planets will align tomorrow.

So let’s set the record straight…or at least as much as we can by answering a few simple questions regarding this Mayan end-of-the-world who-hah and why the world will NOT end today.

Where did this idea of the world ending even come from?

The ancient Maya civilization (aka the Mayans), that lived in Central America from roughly 1800 BC until the Spanish wiped the last of them out around 1700 AD were great astronomers. They had their own constellations, pre-telescopic knowledge of the Orion Nebula as a fuzzy object in the sky, and some of their sites are oriented to astronomical objects such as the Pleiades star cluster. Like many advanced cultures, the Mayans used a calendar. They didn’t invent the calendar, but they used it, like most Central American civilizations previous to Columbus coming to the New World; however, they did add on to it.

A view of a Mayan calendar wheel. Credit: www.epicpodquest.com

The Maya came up with a very different calendar from what we use. They have what we call “the Long Count”, which is made up of 13 “baktun”. Each “baktun” is comprised of 20 “katun”. Each “katun” is 20 “tun”, each “tun” is 18 “unial”, and each “unial” is 20 “kin”. What the heck does that mean? Well, we can easily make the metaphor that the Mayan “Long Cycle” is like a year in our very own modern day Gregorian calendar. Now, a “kin” to the Maya is equivalent to a modern day, so a Long Cycle is MUCH longer than a Gregorian year- it’s actually roughly 5,125 years. But here I’m using the analogy just to make a point.

Mayan: 1 Long Cycle = 13 baktun = 260 katun = 5,200 tun = 93,600 unial = 1,872,000 kin

Gregorian: 1 millennium = 10 centuries = 100 decades = 1,000 years = 12,000 months = 365,250 days

When you get a Gregorian calendar for your desk or wall, it usually only has a single year in it, for instance, your current calendar probably doesn’t extend into 2013. Of course that doesn’t mean that 2013 doesn’t exist, you just need a new calendar. Well, the same thing happened with the Maya, they stopped generating calendars beyond this current baktun, which would end in our modern Gregorian time at December 21, 2012 at 11:11 GMT. But like I said, this doesn’t mean the world is going to end. It’s this “reset” of the Mayan calendar that has fueled the plethora of end-of-the-world scenarios.

Looking at this another way, imagine if there WAS a cataclysmic end of the world tomorrow and then far in the future an advanced civilization found what was left our world and realized that there were no calendars that existed beyond 2013…what might they conclude? Oh no, the human calendar must have ended after January 31, 2013!? We all know that’s not true, but one could imagine how an ignorant futuristic civilization might be confused.

Based on this “end of the Mayan calendar”, people across the world and across the internet have tried to come up with ways and reasons that the world might end on December 21, 2012. Some of these catastrophes are minutely based on real things, many are not, and almost all of them are ridiculous. On top of that, the movie 2012 didn’t help the commotion.

What is a planetary alignment and is there going to be one?

A planetary alignment, or conjunction, is when planets appear to lineup in the sky from Earth and they occur fairly frequently. There are a lot of hoaxes related to the alignment of the planets and how that will impact Earth. There’s also another idea that the Earth and Sun will align with the center of the Milky Way galaxy and something cataclysmic will happen to destroy the Earth. This isn’t going to happen. Here’s an article by Francis Reddy of NASA Goddard Space Flight Center that explains why an alignment with the galactic center won’t mean the end of days. So no, don’t try to go outside and look for an alignment of planets in the sky, you won’t see anything.

Now, there was some more baloney going around the internet about a planetary alignment over the pyramids at Giza on December 3, 2012. That was also a hoax… aka NOT REAL!

This photo of a supposed December 3 planetary alignment of the pyramids quickly made the rounds all over the internet. Too bad it’s not real. Credit: Bad Astronomy

Is a rogue planet or asteroid going to crash into the Earth?

NO! Of course not! NASA has a whole division of scientists, in the Near-Earth Object Program, who work to identify and track objects that could pose potential danger to Earth. So far, they have no indication that anything will impact the Earth. There are stories of a rogue world called “Nibiru” that is supposedly going to crash into the Earth. This false claim of a rogue planet-destroyer has been warped and somehow now been misconstrued even further to include an actual dwarf planet, called Eris, that lives out in the Kuiper Belt. This planet was originally referred to as “Planet X”- another claimed possible bringer of Earth’s destruction. So recap: Eris is real, was once called Planet X, Nibiru is not real…and NONE OF THEM WILL IMPACT THE EARTH.

Although it might be a nice excuse to get out of work, don’t expect a killer planet to crash into Earth and obliterate it anytime soon. Credit: www.londonlovesbusiness.com

Is the Earth’s magnetic field or a polar shift going to kill us all?

Again, no. Scientists know from rocks on the floor of the oceans that the Earth’s magnetic field, which protects us from the harmful energetic particles that come streaming off the Sun, actually reverses fields. Now, generally the field of Earth does shift every 400,000 years and we’re sort of overdue for one. However, when the magnetic field does reverse (referred to as a polar shift), it won’t be instant- at least we don’t think so- and it probably won’t happen for a couple more millennia.

So there you have it, no the world will not end. Yes, scientists are pretty sure- here’s an official website from NASA addressing these issues and concerns in case you’re not convinced. And finally, yes, people on the internet are crazy. So I guess all that’s left to say then is happy new Long Cycle everyone!

Earth is not alone…

Continuing the lunar trend after my last post, which highlighted new multimedia from NASA that reviewed the stages of the Moon’s development and a tour of the Moon’s most notable features, now I’d like to share some more recent news about Earth’s only natural satellite…or so we thought.

Leading theories about the creation of the Moon is that an object about half the size of Earth (roughly Mars-sized) collided with the Earth roughly 4.5 billion years ago. This cataclysmic, near-Earth-ending impact (models show that an impactor only 10% larger would have completely destroyed the planet) ejected a large amount of debris that settled into a ring system around Earth. As the Earth cooled and gravity pulled the planet’s mass into its roughly spherical shape (technically an “oblate spheroid“), pieces of debris in that ring system began to collide and combine, eventually collecting almost all of the debris and forming the Moon. But now, as NPR reports, an international collaboration of researchers from the University of Hawaii, University of Finland, and Observatoire de Paris have written a computer simulation that calculates how many small asteroid-like objects may actually be in captured orbits around Earth. Their results, published in a recent issue of the scientific journal Icarus, conclude that at any given time, Earth may have one or more smaller captured objects, or additional “moons”, in orbit around it. The idea of a captured moon is not a new one, most scientists agree that the two irregularly-shaped moons of Mars, Phobos and Deimos, are most likely captured asteroids whose orbits were disturbed while out in the asteroid belt and were captured by the Red Planet after they strayed too close to it. And of course having a single moon would make Earth unique, of the 6 planets which have moons (Mercury and Venus lack them), Earth is the only planet with a singular moon, or so we thought. But even if these other natural satellites are in orbit around earth, will we consider them moons or will the International Astronomical Union (IAU) make some new kind of classification of “dwarf moons”?

The moons of Mars, Phobos (left) and Deimos (right) are thought to be captured asteroids. Credit: Encylcopedia Britannica

Speaking of the good ol’ IAU, as I detailed in one of my earliest posts, “Alas, poor Pluto“, part of the 2006 decision that de-planetized Pluto defined that a “planet” must clear its orbit of debris. I also mentioned that such a vague definition could leave open an argument for Jupiter to be demoted as well since it has Trojan asteroids which share its orbit. Well now, some could argue that Earth might not technically be a planet anymore either. A new study by NASA’s Wide-field Infrared Survey Explorer (WISE) mission located a Trojan asteroid that shares Earth’s orbit. As NASA explains, “Trojans are asteroids that share an orbit with a planet near stable points in front of or behind the planet. Because they constantly lead or follow in the same orbit as the planet, they never can collide with it. In our solar system, Trojans also share orbits with Neptune, Mars and Jupiter. Two of Saturn’s moons share orbits with Trojans.” Details about the tiny Trojan, designated 2010 TK7, were published in the July 28 issue of Nature. 2010 TK7, seen in the star field below, is only 1,000 feet (300 meters) in diameter is in a highly irregular orbit as it follows Earth around the Sun (click here for an animation of the little guy’s odd orbit). Thankfully though, the smart folks at NASA have done their research and the asteroid’s orbit is well-defined and for at least the next 100 years, so we know that it will not come closer to Earth than 15 million miles (24 million kilometers), which is more than 50 times the distance from the Earth to the Moon. So no end of the world asteroid impacts…from this asteroid, but I’ll leave that conversation for another post.

Earth’s only known Trojan asteroid, 2010 TK7, is shown here, in the green circle, among a field of stars. The asteroid was found by NASA’s WISE mission. Credit: NASA

————————————————————

Related Posts:

Close calls and Chinese Walls…

Hi there folks, here are two interesting tid bits of knowledge for you to chew on.

  • In an odd decision, the 2011 bill that dictates U.S. spending will cut off federal funds that support  scientific exchanges between China and the United States. Virginia congressman Frank Wolf (R), Chairman on the Commerce-Justice-Science subcommittee of the House Appropriations Committee, inserted two sentences into the legislation that prohibits the White House Office of Science and Technology Policy (OSTP) and NASA from coordinating any joint scientific activities with China. On the other hand though, President Obama’s administration has simultaneously said that the spending bill’s ban does not apply to any scientific coordination between China and the US conducted as part of foreign policy. So what scientific coordination are we doing that isn’t a part of foreign policy? Isn’t any connection with the Chinese (or any other government) some branch of foreign policy? In my opinion this is an awful idea. The politicians are basically telling scientists that they are going to be the ones deciding what projects can/cannot be worked on with the Chinese. The scientific community is supposed to be an open, accepting forum where any and all with the right credentials can work together, but instead the government seems to want to handcuff American scientists in a similar way (and of course on a much smaller scale) to the Soviet scientists of the Cold War era. As Ni Feng, director of the Institute of American Studies at the Chinese Academy of Social Sciences, rightly noted, “China and the US, the world’s two largest economies, are set to conduct more cooperation in an increasing number of fields in the future. Biased clauses such as the one Wolf inserted will gradually narrow down the possibility of new cooperation.” So why was this clause even allowed into the bill? Politics. The White House faced resistance from the Republicans when first pushed for the passing of the 2011 US spending bill, so this little diddy was allowed as a concession. Hopefully American won’t concede too much, but I can only see American science suffering from this decision.
  • NASA’s Jet Propulsion Laboratory out in Pasadena has made a very cool, but slightly alarming discovery. According to Don Yeomans, manager of JPL’s Near-Earth Object Program Office, “On November 8, asteroid 2005 YU55 will fly past Earth and at its closest approach point will be about 325,000 kilometers away.” To give you an idea of how close that is to Earth, the moon’s average orbital distance is roughly 385,000 kilometers. So yeah, that’s a close call in astronomical terms. Hopefully this news won’t cause any 2012 Apocalypsers to go crazy because as Yeoman assures, “YU55 poses no threat of an Earth collision over, at the very least, the next 100 years.” YU55 (pictured below) is about 400 miles in diameter and is one of the largest space rocks we’ve discovered that will come this close to Earth. Of course, Earth has had close encounters before, but as JPL scientist Barbara Wilson notes “we did not have the foreknowledge and technology to take advantage of [those previous opportunities].” She and many other scientists are extremely excited about the flyby because “it should be a great opportunity for science instruments on the ground to get a good look.” The asteroid should also be a nice sight for amateur star gazers to grab a look at.

The near-Earth asteroid 2005 YU55 — on the list of potentially dangerous asteroids — was observed with the Arecibo Telescope’s planetary radar on April 19, 2010, when it was about 1.5 million miles from Earth. Credit: Arecibo Observatory/Michael Nolan

%d bloggers like this: