“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.


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 Cosmic Distance Ladder, part 2…

Let’s continue our explanation of how astronomers are able to gauge the distances to celestial objects. In my first post on this topic, we talked about how radar ranging and stellar parallax are used to determine distances in the solar system. Now we’ll continue working our way up the Cosmic Distance Ladder.

Beyond our solar system

As we leave our local planetary neighborhood, our solar system, we can still use stellar parallax up to a point. In fact, I received an email from Scott in Placentia, CA, asking “What maximum distance an object can be reliably determined by parallax measurement using the latest  technology?” As I explained to Scott in my response, it’s hard to answer that question with a single number. Ideally, stellar parallax should always work, because the stars close to us will always move at least a little bit with respect to the background stars. Unfortunately as we look at stars farther and farther away, the angle that the near-ground star moves gets smaller and smaller. As you can imagine there is going to be a point where that slight angular movement is almost imperceptible. However, technology is always improving. In 1989, the European Space Agency (ESA) launched the Hipparcos mission which was specifically designed for astrometry- determining the position and location of stars. The Hipparcos mission found the positions of nearly 100,000 stars as far away as 1,600 lightyears. Expanding on that mission’s success with new technology, another mission named Gaia is slated to launch this summer and claims to have the ability to find distances to stars tens of thousands of lightyears using stellar parallax. Some sources claim that stellar or trigonometric parallax is limited by current technology to around 1,000 parsecs or roughly 3,260 lightyears.

Examining other Suns

Once we reach that upper limit for the use of stellar parallax, where we can no longer accurately measure the angular shift of the star with reference to the background stars, we have to turn other methods for determining distances. The next technique we need to rely on is called spectroscopic parallax. Now, confusingly this new type of parallax is totally different from and unrelated from actual (stellar) parallax, it just uses the word “parallax” because it’s a technique used to find distances, like parallax. (That’s not confusing at all…) Okay, so how does this spectroscopic parallax work? Well you might remember in The Cosmic Distance Ladder, part 1… I talked about an important instrument used by astronomers called a spectrometer (a.k.a. “spectrograph” or “spectroscope”). These extremely useful devices break white light up into all the colors of the rainbow- this resultant array of colored light is called a spectrum. You’ve probably seen this phenomenon before. Well spectroscopic parallax, as the name implies, is all based on being able to take a good spectrum of a star. This is what sets the upper limit on the maximum distance of objects that we can determine using this technique; with current technology, spectroscopic parallax is limited to roughly 10,000 parsecs (1 parsec = 3.26 lightyears = 19.2 trillion miles). For distances where both spectroscopic and stellar (trigonometric) parallax can work, we generally use stellar parallax because it’s more precise- you’ll see why in a bit.

A prism is an example of a very simple spectrometer. Also known as “spectrographs” or “spectroscopes”, these instruments break down white light into its component colors and are integral to astronomers. Credit: Montana Space Grant Consortium

You might also remember in my recent post about stellar classification, that I explained how each stellar class has a spectrum that is unique to that class.So that means that if you look at a nearby B-type star and a far away B-type star, they should have the spectra that are nearly identical. The difference between the two measured spectra will be their intensity, which correlates to the brightness or luminosity of a star. But now we have to be careful because there are two types of brightness: apparent magnitude and absolute magnitude. Absolute magnitude is how bright an object actually, intrinsically is, while apparent magnitude is how bright it appears to be at Earth if you ignore the atmosphere. So basically absolute magnitude is how bright an object would be if you were at it and apparent magnitude takes into account how far away you might be from the object. Think about a lightbulb: absolute magnitude would be the physical amount of light that the bulb puts out and apparent magnitude is the amount of light you measure from the bulb when you stand on the opposite side of the room. As you can imagine, the bulb will appear less bright the farther away from it you are. Same with stars.

Now, once you’ve measured the apparent magnitude (using some sort of light collecting device) to see how bright the star appears to be, you have to figure out the absolute magnitude. This can be a little tricky and involve some guesswork, but the main tool we use is the Hertzsprung-Russell diagram.

A Hertzsprung-Russell diagram like this makes it easy to determine the absolute magnitude range of each stellar class. Credit: Swinburne University

As you can see, when you plot the H-R diagram, you can easily determine a range of absolute magnitudes that apply to each spectral class. Unfortunately that means there isn’t one right answer, so you can’t get an exact distance for the star…but you can get a pretty good range. Once you determine an appropriate value of absolute magnitude (M), you need to use some math and a mathematical formula known as the distance modulus.

Yay math!

Now that we have the apparent magnitude (m), which we measured, and the absolute magnitude (M), which we inferred from the H-R diagram because we know the star’s spectral type, we can now use both to get the distance modulus: m – M. You might ask, “How does that help?” Well if you think about it, the difference between the absolute brightness and apparent brightness of a star is determined by distance; naturally then there is a mathematical relation that proves that.

Distance Modulus formulaWoah, that probably seems like a lot of math…but it’s not so bad. The lefthand-side of the equation is our distance modulus (m – M), that gives us a dimensionless number (since neither m or M has a unit of measurement like feet or grams) that’s the difference between the absolute and apparent magnitudes. Since the lefthand-side has no units, then that means the righthand-side can’t have them either, that works out as long as we say that the 10 in the denominator is in the unit of parsecs, hence the “pc“. Then our distance (d) will be in units of parsecs and everything is balanced out correctly. So rearranging this equation to solve for the distance, we get:

Distance formulaAnd calculating that gives us the distance to the star, d. Now granted, we might need to do that for a high and low value of M, based on how we read the H-R diagram, meaning we’d get a range of distances and not a single answer, but it still gives us a much better idea than we had about these far away stars. This is why we’d choose trigonometric parallax over spectroscopic parallax for distances where both can work, but for distances beyond the reach of stellar parallax, then spectroscopic parallax is better than nothing! Somewhere “between A and B lightyears away” is much better than “really far”!


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The Cosmic Distance Ladder, part 1…

For the past few months, I’ve been spending a lot of time in my position as Manager of the UNH Observatory, in helping to prepare for the 2012 New England Fall Astronomy Festival. The event, lovingly known as NEFAF, is a family-friendly astronomy-related event that will be hosted by the UNH Physics Department in partnership with the New Hampshire Astronomical Society. As you can imagine, this is quite an undertaking, but in an incredibly exciting turn of events, we just found out that Dr. Alex Filippenko, noted astronomer from UC-Berkeley and member of the research team that won the 2011 Nobel Prize in Physics, will be giving the keynote talk at NEFAF 2012! In addition to being a highly acclaimed professor, Filippenko is also the co-author of an extremely popular astronomy textbook and a frequent contributor to the documentary series The Universe on The History Channel.

Dr. Alex Filippenko, the newly announced keynote speaker for the 2012 New England Fall Astronomy Festival to be held at the UNH Observatory.

That extremely exciting news has inspired me to do a couple of posts about the expansion of the universe, the area of research that Dr. Filippenko works on. But before we can really get into talking about that, we need to cover a very basic aspect of astronomy, but something that most non-astronomers don’t really know about. I was at a public session at the Observatory this weekend when a guest who had never studied astronomy before asked me what she thought might be an “ignorant” question: she wanted to know how exactly astronomers knew the distances to objects in space. This is by no means an ignorant question, in fact it’s a very fundamental and very involved question that really gets at the very nature of astronomy.

Astronomy by definition is an observational science. Unlike many other scientific disciplines, astronomers can’t really do experiments in a laboratory (although some do). But the stereotypical astronomer can’t throw his subject (a star or galaxy) on a lab bench and dissect it or set up an experiment to test it, so astronomers need to observe and record data. Okay, so we observe light, that tells us what something looks like, where it is, and how bright it is. Big deal, is that really that helpful scientifically. Well, not really. So we have to come up with ways to get more information from observing the light. The main way we do that is by breaking the light up in a spectrometer, an instrument that breaks light down into a spectrum of colors. This breakdown of light can reveal an abundance of new information including what the object is made up of, how hot it is, how fast and in what direction it’s moving, how old it is, and more.

The question of how astronomers calculate the distance to an astronomical object varies depending on how far away the object is. Because most of these techniques only work up to a certain distance, there is actually a progression of different approaches that astronomers use to measure distance to celestial objects. This list of methods of measuring astronomical distances is known as the Cosmic Distance Ladder (or less poetically, the extragalactic distance scale).

A graphical representation of the distance-measuring techniques that make up the Cosmic Distance Ladder. “1 A.U.” is 1 astronomical unit or approximately 93 million miles, the distance from the Earth to the Sun. A “pc” is a parsec, equal to 3.2 lightyears (206,265 A.U.) or about 20 trillion miles. “Mpc” stands for “Megaparsec” or millions of parsecs. Credit: University of Rochester

In our solar system

The first step in our exploration of the universe was to our own celestial neighborhood. The first step was precise measurement of the size scale of the solar system, which started with the determination of the distance between the Earth and the Sun. As I’ve explained before, this measurement was originally calculated via observations of transits of the planet Venus across the disk of the Sun. Early on in the 20th century, observations of asteroids also played an important role in this measurement. But today the distance from the Earth to the Sun, defined as 1 Astronomical Unit or “AU”, is measured with high precision using radar ranging. By bouncing a radar beam off another planet, usually Venus, and measuring the time that beam takes to return to Earth, scientists can very accurately determine the difference in the size of the two planets’ orbits. Using that difference and the ratio of the two orbital sizes, we can very easily calculate the distance the Earth must be from the Sun. We use a similar process even closer to home. During the Apollo missions of the late 1960s-early 1970s, astronauts deployed the lunar laser ranging experiments, arrays of mirrors that allowed scientists to measure the distance to Earth’s only natural satellite with extreme precision using lasers. This radar ranging is how we’ve calculated the distance to most of the objects in our solar system. More recently, we can also use spacecraft in orbit around other planets as a tape measure by measuring the time it takes for a signal to travel from the spacecraft to its controllers on Earth.

Another  way we can get measure the distance to the planets and to nearby stars is a phenomenon known as stellar parallax. This method is less accurate than radar ranging for planets, but is very good for stars in our local stellar neighborhood. Parallax is something you experience almost every day. Hold your thumb up at arm’s length. Close one eye, then open that one and close the other. Notice how your thumb appears to shift with respect to the objects far off in the distance? That’s parallax! Astronomers take measurements of a planet or star a two points in Earth’s orbit (6 months apart) and measure the angular shift of an object with respect to the background stars between those two measurements. Then, because we know the distance the Earth is from the Sun, we can use some basic geometry to calculate the distance to that star or planet in the foreground.

This diagram shows how parallax is used to find the distance to planets in our solar system and nearby stars. Scientists make two observations 6 months apart, measuring the angle that an object (the red dot) makes with regard to the background stars between the two observations. Then using the distance from the Earth to the Sun (1 A.U.) and some simple geometry, the distance to the object (d) can be calculated. Credit: Hyperphysics

It was using parallax, that Italian astronomer Giovanni Domenico Cassini was able to roughly calculate the distance to Mars in 1672. His calculation was a little bit off though, because instead of taking two measurements 6 months apart, he sent his colleague to Cayenne, French Guiana (on the northern coast of South America) to make observations while he stayed in Paris. Then Cassini could make the same parallax calculation using the known distance between the two observation points (~4400 miles) instead of the distance from the Sun to the Earth. This single direct measurement of the distance to Mars, which is now easily calculated and heavily used by missions such as Curiosity, actually allowed for the calculation of the distances to all the planets. Since geometry and Kepler’s Laws governed the basic ratios the Sun-planet distances, you only needed to measure one Earth-planet distance to be able to easily calculate them all. This major contribution and several others in planetary science (including the discovery of four of Saturn’s moons and joint discovery of Jupiter’s Great Red Spot) prompted NASA to name the Saturn-bound spacecraft mission after the him.

Giovanni Domenico Cassini

[To be continued…]


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7 Minutes of Terror…

Hello all! So I made it successfully back to NASA Goddard from Snowmass Village, Colorado. The conference went well, but as with all scientific conferences, it was quite daunting. However to help me recover, this weekend I visited the Smithsonian National Air and Space Museum’s Steven F. Udvar-Hazy Center to see the recently retired Space Shuttle Discovery. As I’ve chronicled in the past, Discovery is by far the most accomplished of the five Shuttles that have flown (of which only three survive)– an impressive resume that puts it in the upper echelon of American vessels right alongside the USS Enterprise (that’s the Navy aircraft carrier, not the fictional starship…). Seeing Discovery in person was extremely impressive. Being able to see the scorch marks from reentry on the underbelly of the nose and then realizing that each individual tile is labeled was very cool. Up close, the Shuttle looked much more like a patchwork of different components than the sleek space-faring plane that I’m used to seeing in photos. The size also caught me off guard. I’m not sure why, but I’ve always assumed that the Space Shuttle must comparable in size to a commercial airplane that most of us are used to, like a Boeing 747, but it’s not, it’s much smaller. I guess in a way it was both bigger and smaller than I expected…if that makes any sense. Below are some pictures of Discovery.

Moving on to other cool space things. Have you ever wondered what it would be like travelling to Mars? Well a new short video from the great folks at NASA Jet Propulsion Laboratory (JPL) out in Pasadena, CA shows how harrowing the journey might actually be. The team working on the new Mars rover, Curiosity (part of the Mars Science Laboratory mission) have released a new video, entitled 7 Minutes of Terror, detailing the rover’s planned 7-minute descent through the Martian atmosphere and onto the surface of the Red Planet. If you’ve ever doubted the ingenuity or ability of NASA scientists and engineers then you should definitely watch this short video (it’s much less than seven minutes long). The sheer magnitude of the problem that they are attempting to tackle is impressive enough (aka landing something the size of a couch on an object millions of miles away), let alone the fact that they are doing it without any communication with the spacecraft (the entire landing process will have been completed in the time it takes communication to reach Earth from Mars) and dealing with insanely sensitive and delicate instrumentation. It’s just a great look at how insanely talented and inspiring the folks at NASA are. Kudos to them.

Curiosity will be the third functioning NASA rover on Mars, joining its Mars Exploration Rover brethren Spirit and Opportunity who landed in 2004 (Opportunity is still functioning), and will specifically be investigating the habitability of Mars. Curiosity was specifically designed to study layers in Martian mountains that hold evidence about wet environments of the planet’s early existence and assess whether Mars ever had an environment able to support microbial life forms. The rover, launched on November 26, 2011, is scheduled to land on the Martian surface, near the base of a mountain inside Gale Crater, close to the Martian equator, early on August 6, 2012 (EDT) to begin its two-year prime mission.

NASA’s next Mars rover, Curiosity, on a test drive. Credit: NASA/JPL


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Voting for the 3QD Science blogging competition is open!!…

ATTENTION Readers: Voting for the 3 Quarks Daily Science blogging competition is open!

Here’s how you can get involved:

1) Check out my nominated post: Saturn’s rings explained…

2) Go here and check out the other 100+ nominated blog posts that span all of the sciences

3) If you like my blog and think it worthy (or any of the others nominated), please go here and vote by 11:59pm on Saturday, June 16

4) Please share this with your friends, there’s tons of great science writing to be had!!


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Today is transit day…

Hello friends, don’t forget that this evening starting around 6pm EST you’ll be able to see Venus transiting the disk of the Sun, a phenomenon that won’t occur again until 2117!!

Remember, DO NOT LOOK AT THE SUN DIRECTLY WITHOUT PROPER PROTECTION! For safe tips on how to view the transit, click here. Or to be super safe (and mobile) you can check out NASA’s live webcast of the transit from the Keck Observatories at Mauna Kea, Hawaii. That broadcast will feature UNH alumnus and thesuntoday.org creator Dr. C. Alex Young of NASA Goddard Space Flight Center.

For more information about the transit, you can visit NASA’s official transit webpage, thesuntoday.org, or transitofvenus.org.

Also, to help you get super pumped about the transit, here are some fun tidbits.

Here’s a link to my friend and fellow grad student, Mark Zastrow from Boston University’s Department of Astronomy, detailing the amazing and harrowing tale of 18th century French astronomer Guillaume Le Gentil‘s trek to observe the pair of Venus transits in the 1760s: The Worst Observing Run Ever

And to prove that Venus is actually going to cross the disk of the Sun, here’s a video from NASA’s SOlar and Heliospheric Observatory (SOHO) satellite. The video is of a series of coronagraph images. Coronagraphs image the corona, or atmosphere of the Sun, and associated flares and coronal mass ejections by blocking out the extremely bright disk of the sun. You’ll notice the big empty blue spot in the middle of the picture, that’s the blocked out part and that white ring indicates the actual outline of the Sun’s circumference. The Sun’s really bright, so you need to block out a lot more than just the disk. You’ll see some big blobs of particles and plasma coming off the Sun, that’s normal solar activity. And finally you’ll see that bright image approaching the Sun from the left, that’s Venus, reflecting the incredibly bright light from the Sun.

Hope you like all that. Enjoy the transit! And if you have any cool transit-viewing pics or experiences, feel free to share them in the comments!


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