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!

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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Curiosity did not kill the cat…

So as I’m sure you’ve all heard, NASA’s Curiosity rover successfully landed on the surface of Mars in the early hours of yesterday morning (east coast time). In an earlier post, I relayed the video by NASA of the harrowing entry that Curiosity needed to go through to reach the Martian surface safely and highlighted that the entire elaborate landing procedure was 100% automated since it takes double the time the landing would take to occur for information to be relayed back to Earth. And all the taxings of a mission so complicated, despite all the finesse and delicacy needed to execute such a bold attempt, and despite all the things that could go wrong, the scientists and engineers at NASA succeeded. Honestly, if you watch the 7 Minutes of Terror video, realize that scientists built and programmed a machine that could do that all automatically, millions of miles away from Earth (352 million to be exact) while moving at thousands of miles per hour and have it work flawlessly, and aren’t awed and impressed, then well you should probably check your pulse.

The Mars Science Laboratory’s mission is to investigate the interior of the Gale Crater for signs of microbial life. Top left: A profile of Curiosity’s landing site, Gale Crater. Top Right: A simulation of Curiosity’s proposed mission. Bottom: A map showing the distribution of NASA’s missions to the Martian surface. Credit: BBC News

In addition to being the largest rover we’ve ever sent to another world, twice as long (about 10 feet)  and five times as heavy as NASA’s twin Mars Exploration RoversSpirit and Opportunity, launched in 2003, Curiosity also has new equipment that allows it to gather samples of rocks and soil, process them, and then distribute them to various scientific instruments it carries for analysis; that internal instrument suite includes a gas chromatograph, a mass spectrometer, and a tunable laser spectrometer with combined capabilities to identify a wide range of organic (carbon-containing) compounds and determine the ratios of different isotopes of key elements. There’s clearly a reason why the mission is called the Mars Science Laboratory.

This illustration from NASA shows the size and instrumentation of Curiosity that will help it to investigate the possibility of microbial life on Mars. (A) Six independent wheels allowing the rover to travel over the rocky Martian surface. (B) Equipped with 17 cameras, Curiosity will identify particular targets and then zap them with a  laser to probe their chemistry. (C) If the signal is significant, Curiosity will swing over instruments on its arm for close-up investigation. (D) Samples drilled from rock, or scooped from the soil, can be delivered to two hi-tech analysis labs inside the rover body. (E) The results are sent to Earth through antennas on the rover deck. Return commands tell the rover where it should drive next. Credit: BBC News

According to NASA, Curiosity carries with it “the most advanced payload of scientific gear ever used on Mars’ surface, a payload more than 10 times as massive as those of earlier Mars rovers.” All that gear will be important as Curiosity investigates its main science objective: whether or not there is evidence of microbial life (past or present) in Martian rocks. Although both Spirit and Opportunity listed the search for life as among their scientific goals, neither rover was really equipped to search for microbial life; the twin early generation rovers were more specifically looking for water or the evidence of past water on the Martian surface and then whether that water could sustain life. Curiosity, on the other hand, is specifically equipped to look for microbial life (or evidence of it) in the rocks and soil of the Red Planet. More than just the roving explorer that its forebears were, Curiosity is for all intents and purposes a laboratory on wheels.

This image of Curiosity descending to the Martian surface with its parachute was taken by the High-Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter. The rover is descending toward the etched plains just north of the sand dunes that fringe Aeolis Mons. Credit: NASA

And it’s not just the instrumentation that Curiosity is equipped with that make NASA rover 2.0 better than previous generations, but the technology it used to get to the Martian surface is leaps and bounds ahead of how Spirit and Opportunity landed. If you watch this NASA movie that highlights the landing process for the Mars Exploration Rovers (which only had six minutes of terror), you’ll notice that most of the landing procedure seems similar to Curiosity’s. Extremely high-speed entry into the Martian atmosphere, heat shield, parachute, rocket thrusters, etc. Until you get to the last step, when Spirit and Opportunity wer basically dropped onto the Martian surface at nearly 60 mph, surrounded by huge air bags, and allowed to bounce three or four times until they settled. Compared to the fine precision placement of the Curiosity rover earlier this week, the previous rovers’ landings were downright barbaric, like trying to hunt a deer by throwing rocks.

This image, one of the first returned by Curiosity, shows the rover’s shadow on the Martian surface and one of the main targets of its mission, Aeolis Mons, on the distant horizon. Credit: CNN

Rather than violently smashing the $2.6 billion rover into the surface and hoping for the best, this descent involved a sky crane and the world’s largest supersonic parachute, which allowed the spacecraft carrying Curiosity to target the specific landing area that NASA scientists had meticulously chosen. That landing area is roughly 12 km (7.5 miles) from the foot of the Martian peak previously known as Mount Sharp. Aeolis Mons, as it’s now known, is the 18,000-foot (5,500-meter) peak at the center of Gale Crater, previously known as Mount Sharp. The stratified composition of the mountain could give scientists a layer-by-layer look at the history of the planet as Curiosity attempts its two-year mission to determine whether Mars ever had an environment capable of supporting life.

Possibly the biggest piece of the NASA Curiosity puzzle has been the enormous PR campaign that NASA has thrown behind the rover. Not only has the rover and it’s 7 Minute of Terror video been all over the internet, TV news, newspapers, and other media outlets, but NASA has even gone out of its way to get high-level stars in the fold. Last week they released this video (above) of William Shatner, most famously known as Capt. James Tiberius Kirk of Star Trek, narrating a preview of Curiosity’s “Grand Entrance” to Mars. There was also another video featuring narration by Wil Wheaton (Wesley Crusher from Star Trek: The Next Generation).

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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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Can Venus help us find exoplanets?…

This post is in response to loyal reader Jarman Day-Bohn’s question, which he left in a comment on the post “Today is transit day….”. Jarman asked:

How much do you think this [transit of Venus] will contribute to the current research experts are performing toward the study of possible earth-like planets out there? I know they were heavily using a technique measuring how much of a star’s light is blocked out by a planet to judge its size and other factors. Will this in any way help that process?

Great question Jarman, thanks for asking! Let’s look into that a little bit more.

But before we get too far into that, let’s think a little more about transits. Whether or not a transit occurs is all based on perspective. From Earth, only Mercury and Venus are interior planets- planets orbiting closer to the Sun- so they’re the only two that can we can see transit the Sun’s disk. If you were on Mars though, you could conceivably see Mercury, Venus, and Earth transits. And if you were on Pluto you could, in theory, see all eight planets transit the Sun. Remember though, as you get further away, even though more planets can be seen transitting the Sun from your perspective, you’re also getting further away, meaning the Sun is going to look smaller and smaller to you, as are the transitting planets. The Sun is only 93 million miles from the Earth (that’s really close astronomically speaking), so the enormous Sun, which is 1 million times larger in volume than the Earth, takes up a relatively large portion of the sky (~0.5 degrees). As you move further away from the Sun, its angular size in the sky will shrink. By the time you got to Pluto, which is 3.67 billion miles from the Sun, but still close astronomically speaking, our local star would look like a bright speck only ~0.01 degrees (50 times smaller than in the sky on Earth); probably something similar to the artist’s depiction below.

This artist’s depiction shows what the Sun might look like from an object, like Pluto, that’s in the solar system’s Kuiper Belt. Notice how the relatively close Sun differs from the background stars. Credit: NASA/JPL-Caltech/T. Pyle (SSC)

Now as you travel further from the Sun, let’s say to a planet orbiting another star, and look at our Sun, you could still in theory see all eight planets (and Pluto) transit the Sun, but now you’re trillions of miles from the Sun which is now just point of light in the sky, the same way other stars appear to us in the nighttime sky. The really astounding thing about looking at the other stars in our galaxy (Note: every star you see in the nighttime sky is in the Milky Way, we can’t resolve single stars in other galaxies.) is that they are so incredibly far away that no matter how large a telescope we use, we can never see the disk of the star like we can with the Sun, it just won’t have a large enough angular size. Now matter what, even through the Hubble Space Telescope, stars look like pinpricks of light that astronomers call “point sources“. Which makes actually seeing a planet transit a star, like we can see with Venus, impossible. I’ll remind you that in a previous post entitled “Baseballs, not umbrellas…” I explained the continuing search for exoplanets and covered all three of the main techniques which scientists employ to find these elusive celestial bodies around our galaxy. As Jarman indicated, the most successful and commonly used method of detection is the “transit method”. This is the method that NASA’s Kepler mission has already used to find the first Earth-like rocky exoplanet. However, since I just explained that we can’t actually see the exoplanet transitting the distant star, the only way we can detect the transit is by recording the change in light we see as the exoplanet crosses in front of the star. But again, we don’t actually “see” the transit happen, we just observe the dip in the brightness given off by the star. Similarly, if you were on a ship off the shore and someone walked in front of the lighthouse beacon, you wouldn’t be able to see the person, but you might be able to record the drop in brightness as they walked by.

This artist’s idea of NASA’s Kepler mission looking for exoplanets illustrates the main technique that scientists hope to use to find planets orbiting other stars- called the transit method- but no matter the size of the telescope we can’t actually see the exoplanets transitting the disk of the star. Credit: universetoday.com

But now let’s get back to Jarman’s actual question: can a transit in our solar system, like that of Venus, help scientists to find planets transitting other stars? It might. The transit of Venus is a well-documented and well-understood phenomenon, which scientists have been able to accurately predict and observe at least 6 times in the last 400 years. As I explained in “Looking to launch and preparing for transit…“, the transit of Venus helped us to determine the size of our solar system. And since we’ve actually been able to explore our solar system and have a very good grasp of the size of Venus and the Sun and the distances between the Earth and each of them, we can use the transit of Venus as a calibration tool in our search for extrasolar planets. For instance, scientist can say a planet like Venus, which is so big, transitting in front of a star like the Sun, which is so big, would cause a drop in brightness of this much at this distance. Then we can scale that distance out to other stars and we get some idea of what we need to look for in our search for exoplanets.

So Jarman, there’s your answer: while the spectacular crossing of Venus may not lead to groundbreaking new methods to find exoplanets, it does give us a rare opportunity to view a transit (that involves objects we know a lot about) and use that as a reference point as we continue our search!

Thanks again to Jarman for posing this question and if you, like Jarman, have a question that you’d like to have answered, please leave a comment or use the “Contact astroian” tab at the top of the page to send me an email!

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A glimpse of the transit…

Here’s a screen capture from the live NASA webcast of  visible (white) light image of the surface of the Sun. That black spot at about 3 o’clock is Venus. The other small black features are sunspots on the surface of the Sun. Some sunspots can be larger than the Earth. Credit: NASA

Hey everybody! So I hope all of you are watching the NASA live feed of the transit of Venus and seeing cool things like above.

So here is a mid-transit update of some very cool transit things.

First off, you should check out helioviewer.org a very cool website that allows you to make your own compilation of solar images or videos from a multitude of satellites and data from NASA, NOAA, ESA, and more!

Here’s another great shot in the extreme ultraviolet (EUV) from NASA’s Solar Dynamics Observatory (SDO). Again you can see the dark spot, Venus, about halfway across the Sun’s disk. You’ll notice that the EUV allows you to see a lot different detail than the visible light image above. Here we can see the solar corona, or atmosphere, as well as flux tubes (hot plasma trapped along magnetic field lines). That extremely bright region just below Venus with the massive flux tubes flowing out of it is associated with the sunspot you see in the same location on the visible light image above. Sunspots are caused by magnetic field lines on the surface of the Sun that cause a drop in surface temperature (from ~6000 K to only ~3000 K). That temperature drop causes the cooler region to seem dark compared to the rest of the Sun’s surface– hence, sunspots.

An extreme ultraviolet (EUV) image from NASA’s Solar Dynamics Observatory (SDO) of Venus transitting the Sun’s disk. Credit: NASA

And just in case that’s not enough, here’s a link to a movie of Venus’s progression during the transit from SDO, care of @Camilla_SDO.

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