You Can Be a Guardian of the Galaxy!

 

By Knicole Colon, PhD

Scientists want you to help save the galaxy!

Well, not exactly…

What I am really referring to is known as “citizen science.” Scientists are constantly collecting data, and sometimes there are simply not enough scientists in the world to analyze all the data. In some cases computer algorithms provide a relatively simple solution, as a computer can be used to analyze gigabytes of data in a reasonable amount of time. However, there are some cases where human intervention is needed. Nature constantly surprises us, from revealing new species on Earth or unexpected properties of galaxies. Since we don’t know what we don’t know, it can help to have a human visually extract information from data. The Zooniverse was created for this very purpose.

The Zooniverse is home to a collection of various projects, relating to astronomy, the humanities, biology, and more. A user can sign up for free and participate in any project that interests them. This can range from identifying different types of galaxies to searching for near-Earth asteroids to reading historic ship weather logs to classifying different animals seen in the Serengeti to studying genetics by spotting worms laying eggs. This is science that is both fun and accessible to anyone, regardless of your field of expertise.

The details of each project are a bit different. For instance, Planet Hunters allows you to search for planets that transit (pass in front of) their host star by visually checking the light curves (i.e. the brightness over time) of these stars, using archived data from the Kepler space mission. If you identify a signal as a potential planet, and the Planet Hunters team ends up confirming the planetary nature of that signal, then you get to be acknowledged in the publication of those results. To date, over 60 new candidate planets have been found through the Planet Hunters project, including the confirmation of two new planets (now known as PH1 b and PH2 b). According to the Planet Hunters team, this is a result of the efforts of over 280,000 volunteers who searched through more than 21 million Kepler light curves since December 2010. This is equivalent to a cumulative total of 200 years of work.

Clearly, the Zooniverse is an amazingly successful platform that has allowed scientists and non-scientists alike to participate in different research projects. I highly recommend checking out the site, as it is quite fun and gives you a break from your daily research routine. Plus, by participating, you get to help “save” science (and the galaxy!) by helping scientists analyze the plethora of data they have gathered. New projects continue to be added, and who knows, maybe you are working on a project right now that could benefit from being added to the Zooniverse! The opportunities are endless, and it excites me to see how much citizen science continues to grow.

Critical Thinking Makes the World a Better Place

 

By Knicole Colon, PhD

As scientists, our primary job is to conduct research and present our results to both the general public and scientific communities. What should go without saying is that the results we present should be accurate to the best of our knowledge and should not be falsified in any way. However, there are cases where we run every test we can think of, and we get one result that we truly believe to be correct… but then, someone else comes along and runs some test we did not think of, and disproves our result. Ultimately, that person is another scientist just doing his or her job. That is, they use critical thinking to think of things that we did not. That does not mean we were wrong, or did “bad” science. It just means that scientists are not omniscient beings!

There have been a few recent examples in the astronomy world of (supposedly) critical findings that have been debunked by critical thinking from other scientists not involved in the original studies. For instance, a few years ago it was announced that a relatively nearby star known as GJ 581 had at least two planets in or near the so-called habitable zone. That suggested that these planets could have liquid water. Numerous studies of these planets followed this announcement, which together suggested that one of these planets was one of the most Earth-like planets found to date outside of our solar system. This is obviously a big deal, because we only know of one place in the universe where life exists (Earth, of course). By finding another planet that has an extremely similar temperature and size as Earth, it stands to reason that it may very well host life. Note that it may not be humanoid, but still, life could exist. If scientists have a reason to believe such a planet exists, then they will (and did) focus their efforts and resources on studying that planet. Well, as it so happens, some scientists have been using their critical thinking skills to question the existence of these planets since their discovery. Last month a paper was published by a group at Penn State  that definitively identified the signals from these planets as being artifacts of stellar activity (i.e. changes in the star’s spectrum are correlated with the rotation of the star, which resulted in a false periodic signal identified as a planet). Thus, these are not real planets after all.

Similarly, I recently reported results  from a project called BICEP2, which involved measurements that supported the theory of the inflation of the universe (shortly after its creation in the Big Bang). Since then, many scientists have critiqued those results, with some concluding that dust in our galaxy may have been the source of the so-called detection of gravitational waves. After the peer-review process, the scientists who worked on BICEP2 updated their paper to acknowledge that this is a possible explanation.

The point of this post is not to make people skeptical of scientific results. Instead, it should serve to inspire people to think critically about results, to understand how they were achieved, what methods were applied, what data was used, and so forth. If questions are raised during this process, then it could be worth following up with the authors of the paper, to see if they had considered x, y, and z. If they have not, then perhaps a new study should be done. In an ideal world, this x, y, and z should be addressed during the peer-review process (as with the BICEP2 paper). However, since scientists do not know everything, a reviewer may also miss some other explanation of a signal. Either way, it is important for all results to be confirmed, especially if they are particularly groundbreaking. And, during this process, new questions and new findings may come about and end up being even more interesting than the original results. The conclusion is that there is absolutely always something new to learn in the field of science!

The Earth and Moon Have Been Reunited, and It Feels So Good

 

By Knicole Colon, PhD

 

There has been a long-held theory that the proto-Earth was plowed by another proto-planet about the size of Mars some 4.5 billion years ago, and out of the debris from that collision the Moon was born.  Models of this giant collision predict that the Moon’s composition should include a significant fingerprint of this other planet, which is commonly referred to as Theia (who in Greek mythology is the mother of Selene, the goddess of the Moon).  However, the Earth and the Moon have always appeared to be very similar (at least chemically), and there has been no direct evidence to support the existence of Theia… until now!  This new evidence comes from a very detailed analysis of lunar rocks that were collected by astronauts that landed on the Moon back in the 1960s and 1970s.  This study has been published in Science and was led by Daniel Herwartz.

 

You might be asking yourself, if we have had these rocks in our possession for decades, why are we just studying them now?  Well, lunar rocks have indeed been studied before.  However, earlier analyses were not sensitive enough to measure any differences between the chemical composition of lunar rocks and rocks from Earth, differences that would be evidence of Theia.  The new analysis by Herwartz et al. involved the use of advanced electron microscopes and a precise laser-based method for analyzing the rock samples.  The end result was the measurement of 12 +/- 3 parts per million more of a rare isotope of oxygen (oxygen-17) in lunar rocks than is found in rocks on Earth.  This finding is what supports the idea that the lunar rocks contain remnants of the planet Theia.

 

It is really not surprising to find evidence that a Mars-size planet collided with Earth in the early days of the Solar System.  For reference, Mars is about half the size of Earth, and there were likely many similar objects swinging around the Solar System during its formation.  This is because planets form out of a swirling disk of gas and dust that is orbiting around a star.  Planet formation is ultimately a very chaotic process, and objects continuously collide and get destroyed and debris gets formed into new objects, like the Moon.  However, because of this chaos, an alternative theory for differing oxygen isotope abundances in the Moon and Earth is that Earth may have initially had an oxygen chemistry similar to the Moon/Theia but was affected post-collision by an impact from a water-rich comet or asteroid.

 

This is only one argument against the evidence presented by Herwartz et al.  Some scientists are questioning simply the significance of their measurements, since its such a small difference (12 +/- 3 parts per million).  Regardless of whether the results from Herwartz et al. hold up, a debate like this can be good since it can inspire more scientists to pursue similar studies.  To me, it also brings to light another debate, which is really the conspiracy theory that the Moon landing was a hoax.  The study by Herwartz et al. involved analyzing rocks that astronauts brought back from the Moon.  Yes, astronauts did in fact land on the Moon.  No, the landings were not a hoax.  An argument I often hear is, if we did go to the Moon, why haven’t we gone back?  The answer lies in the facts: humans did land on the Moon not once, but six different times.  Humans have not gone back to the Moon since the 1970s for many reasons, including that it is expensive and that we are looking towards exploring new parts of the Solar System now, like Mars.  Plus, we are clearly still learning from those manned missions to the Moon that took place decades ago thanks to studies like that led by Herwartz.  Now we may finally have the first direct evidence to support the existence of Theia.  I will say that since these findings are somewhat debatable, maybe this is a good selling point to send humans back to the Moon.  I would not object to seeing that happen in my lifetime!

Jill Tarter: A Leader for the Search for Life Beyond Earth

 

By Knicole Colon, PhD

 

I first knew I wanted to become an astronomer when I was 12 years old.  The main driver behind my desire to study the universe came from watching the movie Contact, which was released in 1997 and stars Jodie Foster and Matthew McConaughey.  The movie (based on the book of the same name by Carl Sagan), tells the tale of a female scientist fighting for her right to conduct research on a topic she is passionate about: the search for extraterrestrial life.  She faces heavy opposition from both scientists and politicians who believe her research ideas are more like science fiction than fact.  Spoiler alert: eventually she detects an extraterrestrial signal that leads to her traveling through a wormhole and visiting the extraterrestrial beings.  However, things are complicated and not many people believe her trip through the universe actually took place.  There is much more to the story, and I highly recommend seeing the movie or reading the book.  The story offers a fascinating (and fairly realistic) portrayal of the life of an astronomer while also exploring the never-ending debate of science versus religion (in light of making contact with an alien species).  For me, the best part is that the female protagonist in the story (Ellie Arroway) was actually inspired by the real-life scientist Dr. Jill Tarter.

 

Dr. Jill Tarter, who is now 70 years old, has been involved with the search for extraterrestrial life ever since her graduate school years (in the 1970s) at the University of California, Berkeley.  She has been involved in various projects like SERENDIP (Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations) and Project Phoenix (a search for extraterrestrial messages in radio signals).  The latter project was run by the SETI (Search for ExtraTerrestrial Intelligence) Institute, which Tarter helped found and where she was the Director from 1999 until 2012.  On top of that, she has received numerous awards and honors for her work, including being named one of the 100 most influential people in the world in 2004 by Time Magazine.  Clearly she has had a successful career, but not without some hardships.

 

Tarter’s career was just beginning in the 1970s, and she had to make her way through a field that was (and still is, but less severely so) dominated by males.  That alone is a daunting task, but then you add in trying to get funding for something that seems like science fiction — searching for signs of intelligent life beyond Earth.  In 1993 the  government decided to no longer fund SETI programs, so Tarter has been leading efforts to find private funding to support the research at the SETI Institute since then.  One major scientific breakthrough that has helped her cause is the discovery of extrasolar planets.  Before 1995, all the research at SETI was based on the statistical likelihood that intelligent life existed elsewhere in the universe, but there was no scientific evidence for planets that could host such life.  Now that over 1500 planets have been discovered orbiting other stars, astronomers at SETI are strategically searching stars that are known to have planets!  That makes this a very exciting time to search for signs of alien life.

 

These new prospects are in part what motivated Tarter to retire as Director at SETI and instead focus on the continuous task of finding funding for SETI research.  As she has discussed in recent interviews, the continued operation of SETI is important not just to know whether other intelligent life exists in the universe, but to know that it can survive and thrive for a significant amount of time.  If we can detect signs of intelligent life from a planet orbiting a star that is hundreds of light years away, then that gives us a glimpse of that civilization’s past (due to the time it has taken the signal to travel from that star and reach Earth).  Such a detection would suggest that advanced civilizations may be common and long-lasting, compared to the relatively young technological age of life on Earth.  Of course, a null detection would be just as significant.  That would suggest technologically-advanced civilizations are few and far between.  In either case, I think humans would be motivated to continue growing technologically because we will either know it is possible to survive, or because we will want to defy the odds by surviving.   Only time will tell what new discoveries will be made.  I have a feeling we will make a significant discovery in my lifetime, and I hope Dr. Jill Tarter is also able to enjoy the fruits of her labor!

 

Pack Your Bags – We Have Found Another Earth!

 

By Knicole Colon, PhD

 

Okay, the title of this post is a bit misleading.  It is true that astronomers have discovered an Earth-size planet located in the “habitable zone” of a nearby star.  Note that the habitable zone is the region around a star where a planet has a temperature that allows it to sustain liquid water on its surface.  This definition implies that liquid water is required for habitability, but since all life on Earth seems to require liquid water (as far as we know), this is a reasonable assumption.  Still, I would not pack my bags to head to this new planet just yet.  Besides the fact that the shuttle program is no more (which means we have no means of transportation to go visit this “other Earth”), this newly discovered planetary system is located some 500 light-years from Earth.  To put that in perspective, a single light-year (the distance light travels in a year) is equal to about 6,000,000,000,000 miles.  I think we can all agree that 500 light-years is kind of far.  Regardless, the discovery of this potentially habitable, Earth-size planet (dubbed Kepler-186f) suggests that there are many Earth-like worlds hiding out there, we just haven’t been able to detect them until now!

 

The Kepler mission is responsible for this exciting discovery, and the related paper published in Science and led by Elisa V. Quintana (of the SETI Institute and NASA Ames Research Center) can be found here.  The Kepler mission’s goal was to detect an Earth-size planet orbiting in the habitable zone of a Sun-like star by searching for a transit of such a planet (i.e. an event where the planet passes in front of the star and therefore blocks some of the starlight, making the star appear dimmer).  However, the nominal mission ended once one of the reaction wheels that stabilized the pointing of the telescope died.   Regardless, the Kepler team was able to detect transits of Kepler-186f in the available data, which led them to determine that the radius of Kepler-186f is quite similar to Earth (within 1-sigma).  Furthermore, the planet orbits its star every 130 days, which suggests that the planet has a temperature capable of sustaining liquid water.

 

You might have noticed Kepler-186f has an orbital period that is almost three times shorter than the Earth’s, yet it is believed that it lies in the habitable zone.  This difference lies in the fact that Kepler-186f does not orbit a Sun-like star, which means it is not really “another Earth” after all.  It actually orbits a very cool M dwarf star (named Kepler-186).  There are several classes of stars, with the Sun being a G-type star and having a temperature of about 5800 K (or 9980 degrees Fahrenheit).  Being an M dwarf star, Kepler-186 is about half the size of the Sun and has a temperature of about 3800 K (or 6380 degrees Fahrenheit).  That difference is enough to “move” the habitable zone closer to the star, compared to the location of the habitable zone around the Sun.  That Kepler-186 and the Sun are different types of stars also has other repercussions.  Even if Kepler-186f does have liquid water on its surface, it receives different types and amounts of radiation from its star.  This suggests that the atmosphere is likely extremely different than what we are used to here on Earth.  That does not mean other types of life forms can’t exist on Kepler-186f, but humans might have some problems breathing there.  There’s one other major caveat to calling Kepler-186f an “Earth twin.”  Its mass, and therefore density and composition, are not known.  Some research suggests it is likely to be a rocky planet like Earth, but we do not know for sure.  Unfortunately, it is possible we will never know, because measuring the mass of a tiny object that is so far away is really, really, really difficult to do.

 

One other fun fact about this new planetary system is that Kepler-186f is named as such because there are four other planets in the system, known as Kepler-186b, c, d, and e.  All these planets orbit closer to their host star than Kepler-186f, making them way too hot to have liquid water (their orbital periods are just 4, 7, 13, and 22 days!).  As far as astronomers know, there are no other planets orbiting further out than Kepler-186f.  Even if there were, they would be too cold to be habitable.  So, Kepler-186f is really in the sweet spot, the so-called Goldilocks zone where it’s not too hot, and not too cold, but just right!

 

It is exciting to think about how many other potentially habitable planets like Kepler-186f might be out there.  Now that some 1500 (or more, depending what criteria you use) planets have been found around other stars, astronomers have even started cataloguing planets that come close to being an Earth twin.  For example, there is The Habitable Exoplanets Catalog  and The Habitable Zone Gallery.  Just remember that as we get closer and closer to discovering a true Earth twin, just because a planet is in the habitable zone does not mean it is inhabited.  It is my opinion that there is definitely other life out there somewhere, but so many conditions have to be met that it is not clear how much *intelligent* life may be out there.  Then again, some people believe there is not much intelligent life here on Earth either…  Still, I hold the belief that (to paraphrase a quote from Contact by Carl Sagan) because the universe is so darn big, it would be an awful waste of space if it is just us.

 

Star Wars Planets: More Science Fact than Fiction

 

By Knicole Colon, PhD

The Star Wars universe is enormous, with hundreds of planets and moons that have a range of properties.  Given that astronomers have now discovered some ~1500 exoplanets along with, of course, the 8 planets and ~150 moons in our Solar System, it should be no surprise that astronomers are discovering more and more real planets that are similar to the fictional planets in the Star Wars universe.

 

First, let us look at Tatooine, the home planet of Anakin and Luke Skywalker.  The most unique feature of this planet is that it orbits around two stars.  In fact, one of the most iconic shots from the Star Wars movies is of Luke on Tatooine with two stars setting in the sky in the background.  Yet, up until a few years ago, astronomers were not sure if planets could actually exist in stable orbits around more than one star.  The Kepler mission changed everything when it discovered a planet orbiting two ordinary stars.  That planet, Kepler-16b, is most likely a gas giant planet that is more similar to Saturn than the rocky/desert planet that Tatooine is, but it is still exciting that planets with multiple stars like Tatooine do exist after all.  Plus, we now understand that there is no reason a planet can’t exist in a stable orbit, even in the habitable zone, around two or more stars.

 

Compared to Tatooine, Kamino is a bit less fantastical.  Kamino is an ocean planet where the clone army was created.  While I can’t speak to whether any clone armies exist somewhere in the real universe, it is a fact that water worlds like Kamino can exist.  GJ 1214b is an exoplanet that is a bit larger than Earth, and for awhile it was believed to be a pure ocean planet based on observations that probed its atmosphere.  It is now believed to have a uniform cloud layer high up in its atmosphere, but it is still possible that underneath that cloud layer, there exists one big ocean.  Maybe it’s even constantly raining there, just like in scenes on Kamino in Episode II!  Even though ocean planets really can exist, I don’t know that anyone would actually want to live on a water world where it’s potentially always raining.

 

If Kamino were further from its star and therefore a lot colder, it might be something like Hoth.  Hoth is (in)famous for being a frigid planet, covered by ice and snow.  During the so-called “polar vortex” this past winter, I recall hearing numerous references of Earth being very much like Hoth.  Since winter did eventually end here and summer is coming (unlike in Game of Thrones), Earth is not a good example of a real Hoth-like planet.  However, there is a growing number of small, potentially rocky exoplanets that orbit at very large distances from their host stars.  Being so far from the main source of heat in a planetary system means that these planets are quite cold, and could very well have Hoth-like climates.  One example is OGLE-2006-BLG-109Lc, which takes about 15 years to orbit its host star.  Based on the temperature of its host star and its orbital distance from its star, that planet has an estimated temperature of -360 degrees Fahrenheit.  I’m thinking that might be a bit too cold for anyone to survive there, so if anyone wanted to visit a “real” Hoth one day, we might need to find a planet that is a bit warmer.  Or, just wait until next winter comes.

 

On the opposite end, a lava planet like Mustafar is not an ideal place to settle down either.  Mustafar is the setting for the epic showdown between Darth Vader, (spoiler alert!) previously known as Anakin Skywalker, and Obi-Wan Kenobi.  In that fight scene, they have to take great care to avoid lava spewing at them.  Interestingly, the volcanic activity on Mustafar is supposed to be a result of the gravitational effect caused by two nearby gas giant planets.  This is very similar to the effect Jupiter has on its moons, in particular Io.  Because of gravitational stresses, Io is the most geologically active object in our Solar System, and images have even been taken of volcanic eruptions on its surface.  There are also known exoplanets that are so hot they probably have lava oceans, thanks to orbiting extremely close to their host stars.  One example is CoRoT-7b, which has an orbital period of just ~ 0.85 days or ~ 20 hours!  This was another discovery not expected by astronomers, simply because it was not believed that a planet could survive being so close to its host star.  While CoRoT-7b will likely be “eaten” by its star eventually, for now it is in a stable orbit, with lava likely flowing happily all over its surface.  For all we know, there is some villainous person like Darth Vader hiding there now, preparing to take over the universe.  We can only hope there is some Jedi-type person who is willing to brave the lava and take the villain down!

 

Last but not certainly not least, we have the Death Star.  Its name is quite misleading, since the Death Star is no star.  And, as Obi-Wan Kenobi also pointed out, “That’s no moon. It’s a space station.”  While the Death Star is a feat of engineering rather than an astronomical object, there was a bit of a ruckus in the astronomical community when pictures of Saturn’s moon Mimas were taken by the Cassini probe in 2005.  That’s because Mimas has a remarkably large crater on its surface, giving it a similar appearance as the Death Star.  Thankfully, the resemblance ends there.  Mimas does not have a powerful superlaser that is capable of destroying an entire planet.  But, if it did have a laser, and if it was used by villains to destroy the Earth, I imagine Earth’s  crumbled remains would eventually form what resembles an asteroid belt.  That is something to keep in mind – for any extrasolar asteroid belts that are discovered, we should consider that they could be the result of destruction by a Death Star.

 

As time goes on and astronomers keep hunting for planets, the fictional Star Wars planets are going to become increasingly realistic.  Still, we will never be able to find the “real” Tatooine or Hoth because those planets existed “a long time ago in a galaxy far, far away….”

Wherefore Art Thou Dwarf Planets?

 

By Knicole Colon, PhD
I love telling elementary school kids the story of how when I was their age, the Solar System had nine planets. Of course, after the International Astronomical Union (IAU) demoted Pluto, we now have just eight planets in our Solar System. These eight planets are massive enough to clear the area around their orbits of smaller bodies. This means that in one way or another, all the smaller objects remaining after a planet’s formation were captured. This fact is what separates a planet from a dwarf planet, and it is what motivated demoting Pluto from a planet to a dwarf planet.

 

To paraphrase another quote from William Shakespeare: What’s in a name? That which we call a dwarf planet by any other name would smell as sweet. In reality, using this quote to describe dwarf planets is misleading. This is because objects like Pluto that astronomers classify as dwarf planets are really not planets at all by definition, so they do not “smell as sweet” as planets do. Still, it is the official name that the IAU decided upon for objects that have similar sizes and orbits as Pluto, and so that is what we shall call them.

 

In any case, the entire concept of a dwarf planet came about when astronomers started discovering objects that were similar to Pluto in terms of their sizes and orbits. I can count on two hands the number of dwarf planets currently known. However, a letter by Chadwick Trujillo (Gemini Observatory) and Scott Sheppard (Department of Terrestrial Magnetism) was published recently in Nature that presented the discovery of a new dwarf planet, 2012 VP_113. The discovery was made by detecting the motion of the object compared to distant, stationary background stars in images taken with the Dark Energy Camera (DECam) at the Cerro Tololo Inter-American Observatory (CTIO) 4-meter telescope. However, this was not just another dwarf planet. In fact, it is not very similar to Pluto at all. It is actually quite similar to a different dwarf planet, known as Sedna. Sedna was discovered some ten years ago, and it immediately threw astronomers for a loop. Sedna’s orbit was further from the Sun than any other known object. Its closest approach to the Sun occurs at 76 astronomical units (AU), where an astronomical unit is the mean distance between Earth and the Sun. In comparison, Pluto’s closest approach is about 30 AU. With the discovery of 2012 VP_113, which has its closest approach at 80 AU, we now know of two sizable objects in the outer Solar System.

 

The existence of another Sedna-like object is significant for several reasons. First, it suggests that there are additional similar objects in the outer Solar System, but we have not been able to detect them yet simply because they are too faint. Trujillo & Sheppard use simulations to estimate that several hundred dwarf planets like Sedna and 2012 VP_113 exist in the outer Solar System. That’s a pretty significant number. Second, the existence of these objects helps us better understand the formation and evolution of the Solar System. Any new piece of this puzzle is critical, because current formation models cannot fully explain how the rocky planets (Mercury, Venus, Earth, Mars) and gas/ice giants (Jupiter, Saturn, Uranus, Neptune) formed a stable planetary system like what we observe today.

 

There is one other point made in the paper that really stood out to me, but not in a good way. Trujillo & Sheppard state that their numerical simulations describing orbits of objects similar to Sedna and 2012 VP_113 also suggest that a “massive outer Solar System perturber may exist.” They specifically considered a super-Earth-mass body at 250 AU, which would be too faint to detect with current technology. While the concept of such an object is scientifically sound, the problem I have is when the public hooks onto a concept like this and turns it into a conspiracy theory. Namely, some people believe there is a so-called “Planet X” (or sometimes referred to as Nibiru) in the Solar System. This planet is believed by some groups to be a large planet that will at some point in the near future encounter Earth and essentially cause the world to end. Because of these so-called theories, I believe scientists have to be extra careful with their wording. In this case in particular, it should be clarified that if such a large planet exists in the outer Solar System, the fact that we cannot detect it means it is so far away from the Earth that it will not affect the Earth in our lifetime, or even in our great-great-great-great-grandchildren’s lifetime, if at all. The moral of the story is, while there may be many dwarf planets and even “regular” planets in the outer Solar System, this is no cause for concern. You can sleep well, knowing the Earth will not be destroyed any time soon.

A Story about the Beginning of Everything

 

by Knicole Colon, PhD

The universe began with a bang.  A Big Bang, to be precise.  The Big Bang theory is a well-accepted theory, just like The Big Bang Theory is a well-loved television show.  However, one question astronomers still do not have a clear answer to is, what happened right after the Big Bang?  We know that regardless of which direction we look in the sky, the universe has the same temperature (also known as the cosmic microwave background) and there is a uniform distribution of galaxies and dust, but how is this possible?  It looks like recent results from a project called BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) support what we think happened to cause such uniformity, namely, that inflation happened!

 

The theory of inflation states that less than a trillionth of a second after the Big Bang, the universe was composed only of energy stored in a scalar field (it had no direction associated with it).  During inflation, this field expanded rapidly (faster than the speed of light!) and basically smoothed out the universe.  This is analogous to what happens when a balloon is filled with air.  While the balloon lays flat and unfilled, you can see irregularities on its surface.  However, once you expand the balloon by filling it with air, all those wrinkles are ironed out and the balloon ends up with a uniform surface.  Getting back to the theory of inflation, eventually the inflationary energy field decayed into a uniform universe, filled with particles that over time formed elements and galaxies  and all the other things we know and love.

 

While this was a nice, tidy theory, there was limited evidence for it.  So, a team of astronomers led by John Kovac at the Harvard-Smithsonian Center for Astrophysics used a polarimeter installed on a telescope at the South Pole to detect evidence of those so-called wrinkles or irregularities that were expected to be present right after the Big Bang but before the period of inflation ended.  These wrinkles were actually predicted by Albert Einstein, though he referred to them as gravitational waves.  So, what Kovac et al. did was use three years of data collected from a single patch of sky to search for a certain polarization mode of light within the cosmic microwave background radiation.  The specific polarization mode they ended up detecting is the B-mode, which is only expected to exist for gravitational waves.  Thus, they were able to find evidence for gravitational waves.  Their findings in turn constrain a parameter called “r” to be around 0.20.  Mathematically r is defined as the tensor-to-scalar ratio, which is essentially the ratio of gravitational waves to density fluctuations in the universe (i.e. that scalar energy field I mentioned earlier).  Basically,  a non-zero value of r is evidence for gravitational waves and therefore for inflation.  The results from BICEP2 ultimately indicate a significant detection of tensor modes, or gravitational waves, at a level of 5.3 sigma.  You can check out the paper from Kovac et al., which will be published in The Astrophysical Journal.

 

As with any experiment, we can’t just accept the results without corroborating them.  In this case, there is some controversy involving the value of r that Kovac et al. determined to best fit their data.  This is because r was measured to be less than 0.11 at 95% confidence by the Planck mission just last year.  Considering that the Planck mission consists of a space satellite built specifically to measure the cosmic microwave background to extremely high precision, it’s no surprise some people hold those results in high regard and are questioning the results from BICEP2.  At this point there is not much else to say on this matter, but it will be interesting to see what results come out next year, after additional data is collected and further analysis is completed.

 

What I found most interesting about this announcement is that shortly after the findings were presented to the entire scientific community, the universe exploded again, at least in terms of the ridiculous number of inflation-related papers that showed up on arXiv.org (an archive for new papers on physics and astronomy).  I find it difficult to believe that within only a day or two of the announcement of any result on any topic, people are capable of putting together a legitimate follow-up analysis and writing a full paper to boot.  Perhaps those people are geniuses… who knows.  At least in this process you do end up with some fun papers, like this one that was posted on April 1st: http://arxiv.org/abs/1403.8145.  In that paper, the authors suggest that the results from BICEP2 may be reconciled with the model from the Planck mission if the universe is in fact inside-out.  They make some valid points, and suggest that with some imagination we would be able to solve many mysteries of the universe under this assumption, but unfortunately the paper was only written as an April Fool’s Day joke!

 

When all is said and done, at least we now a better idea of what happened at the beginning of everything.  It’s not every day that you make progress towards learning how the universe began.  Now, if only Sheldon and Amy could make progress towards having a real adult relationship.

So Many Planets, So Little Telescope Time

 

 

By Knicole Colon

 

NASA’s Kepler mission just celebrated its fifth anniversary on March 6th, and it certainly has a lot to be proud of!  Since launching into space in 2009, the Kepler telescope has revolutionized the field of extrasolar planet research.  By monitoring the brightness of  some 150,000 stars over several years, Kepler has been able to detect the tiny dip in brightness caused by a planet that periodically transits (or passes in front of) a star.   With the recent announcement of 715 (!) new transiting planets by the Kepler team, Kepler has increased its total number of planet discoveries to 961 (discoveries that are documented here and here).  That is remarkable, considering that prior to this announcement the number of known extrasolar planets was hovering around 1000.  This recent announcement therefore nearly doubled the number of known extrasolar planets.  Amazing.

 

How did the Kepler team pull off a bulk discovery like this?  Nominally, each planet candidate that is detected (by any technique) must be confirmed by various methods.  This includes measuring the mass of the planet and determining the properties of the host star (since the derived planetary properties are highly dependent on the properties of the star).  The short story is that confirming that a planet is real requires a lot of additional data, and to get that data you need time on various telescopes.  Given that there are a finite number of telescopes suitable for confirming planets, and that there are a finite (actually quite small) number of nights a year when you can use these telescopes, there simply is not enough telescope time available to confirm every single known planet candidate.

 

To answer the question posed above, we have to look to statistics.  An important aspect of Kepler’s recent discovery is that the 715 newly-confirmed planets are all in multiple-planet systems.  This means that for the 305 stars that these planets orbit, a given star has more than one transiting planet that is orbiting around that star.  The statistical technique used to confirm these planets relies on this fact.  Given the few thousand planet candidates Kepler has detected by observing some 150,000 stars, logically one might think that on average most stars host just one (if any) planet.  However, that is assuming that planets are evenly distributed among different stars.  Clearly this is not the case, since the Kepler team identified a significant number of multiple-planet candidate systems.  Based on this observation, it is now logical to think that the probability of a planet in a multiple-planet candidate system not being real is very small (because what are the odds that you get multiple false signals from a single star?).  The Kepler team employs rigorous techniques to validate this logic, and they ultimately conclude that more than 99% of these systems are composed of real planets.

 

Another exciting aspect of this discovery is that nearly 95% of these 715 planets are smaller than Neptune (which is about four times larger than Earth).  A majority of the first extrasolar planets discovered were approximately the same size as Jupiter (which is the largest planet in our solar system, being about 11 times the size of Earth).   It is not surprising that astronomers used to think that Jupiter-size planets were the most common type of planet and because of this, our solar system was unique (as it is composed primarily of many small planets).  It turns out that with the various techniques astronomers have for detecting extrasolar planets, large, massive planets like Jupiter were simply the easiest to detect.  Improved observing techniques and data analysis eventually allowed for the discovery of an increasing number of small planets, but Kepler really hit a home run by providing definitive evidence that small planets are extremely common.  It looks like the solar system is not so unique anymore, which is a good thing!  It means that as astronomers continue to search for and discover new planets, it is safe to conclude that they will eventually find planetary systems that are very similar to our solar system.

 

The best part is, Kepler isn’t finished.  Its nominal mission is over, due to the failure of a wheel that was used to stabilize the pointing of the telescope.  But, there is now a secondary “K2” mission that is actively studying a new set of stars.  Plus, there are still thousands of planet candidates that need to be confirmed (with possibly more on the way, as the Kepler team has not finished analyzing the available four+ years of data).  This does not even include findings from other active planet-hunting surveys.  Given that there are so many planets, but there is so little telescope time, statistical techniques may become the key to future breakthroughs in extrasolar planet research.

 

Space Oddity

 

By Asu Erden

How social media tools can help scientists better understand meteorite impacts

Early in the morning of February 15th 2013, a small asteroid penetrated the Earth’s atmosphere and offered the one million residents of the Chelyabinsk region in Russia a spectacle worth remembering. This rude awakening was caused by a fireball brighter than the Sun traveling at over fifty times the speed of sound. Thirty seconds after entering the atmosphere, this asteroid disintegrated, causing an airburst with an energy equivalent to more than twenty times that of the Hiroshima atomic bomb. The last comparable event occurred in 1908 near the Tunguska river in Siberia and remains elusive to this day. Unlike Tunguska, social media provided a host of information about the Chelyabinsk incident, with over four hundred YouTube videos, Dash camera records, and countless social media reports documenting this outer space intrusion. A Twitter hashtag – #RussianMeteor – even went viral.

 

A few weeks after the impact, Dr. Peter Jenniskens – a research scientist who studies interstellar and interplanetary matter at the NASA’s Carl Sagan Center in Northern California – went to Chelyabinsk where he carried out a sixteen day-long field survey with colleagues from the Russian Academy of Sciences. They wanted to collect and analyze meteorite fragments and to use social media reports to characterize the physical and material damage caused by the airburst. “To my knowledge this is the first instance YouTube videos have been used for [meteor research] purpose[s],” said Dr. Stefan Nicolescu, meteor curator at the Yale Peabody Museum.

 

When Dr. Jenniskens and his team arrived in Chelyabinsk, the ground was covered in snow, which made locating the meteorites impossible. They relied on information gathered from social media and interviews with residents in order to draw out a site distribution map. They also conducted Internet social surveys, which allowed them to better assess the types of injuries that people endured. Surprisingly, the main culprit was not glass damage but rather UV radiation from the asteroid. The majority of people reported experiencing noticeable heat, ocular damage due to the brightness of the fireball, and being sunburnt.

 

Dr. Jenniskens’ team published its findings in the journal Science last November. Their report followed two papers published in Nature earlier the same month that documented parts of the incident, focusing on the damage caused by one of the asteroid fragments and the analysis of selected video records. The key contribution of Dr. Jenniskens’ study lies in the extensive data that it made available to better understand what happens when smaller near-Earth objects penetrate the Earth’s atmosphere. The importance of the asteroid fragmentation pattern caused by the airburst and its direct implication for the damage observed on the ground are now substantiated.

 

“The assumptions when you model these sorts of things are normally 100% speculative. In this case, it was extremely well-observed,” said Dr. Jenniskens. By integrating data from social media, Dr. Jenniskens and his colleagues were able to establish the trajectory, brightness, orbit, diameter, angle of entry, UV irradiation, and speed of the asteroid. It also helped them understand how each of these parameters affected the shockwave, damage distribution on the ground, and injuries caused by the airburst.

 

Scientists will now be able to fine-tune their meteorite impact models and predict how specific characteristics of a given asteroid and its trajectory can affect the damage it will cause on Earth. This in turn will help officials respond more quickly to damage in different regions near the impact site and anticipate the sort of injuries hospitals should be ready to treat. Big Brother might be helpful after all.