The Science of Solar Eclipses

By JoEllen McBride, PhD 

As the sky darkens on August 21st, we will stand in awe of the first total solar eclipse to cross over the contiguous U.S. in almost 40 years. This is also a chance for scientists to do what they do best– science!

 

Total Eclipse of the Sun

Every month, the Moon passes between the Earth and Sun during its New Moon phase. We can’t see the New Moon because the side that faces us isn’t illuminated by the Sun but it’s up there. Solar eclipses happen only when the Moon is in the New Moon phase and crosses the plane created by the Earth-Sun orbit. All other New Moons are either too high or too low in the orbit, to cover Sun.

 

A total solar eclipse is even more special. The cosmos has gifted us with a spectacular coincidence. The distance between the Moon and Earth is 400 times less than the distance between the Sun and Earth. This wouldn’t be interesting except for the fact the Moon is also 400 times smaller than the Sun. Once the Moon hits that sweet spot in its orbit around Earth, it completely covers the Sun.

 

That also means that sometimes a solar eclipse occurs and the Moon doesn’t completely cover the Sun. These are partial or annular eclipses and it just means that the Moon was too far from Earth to hide the Sun completely.

 

A solar eclipse occurs approximately every year and a half (give or take a few months). What makes them seem so rare is our planet is mostly ocean, so the chances of the solar eclipse passing over land with people on it is reduced. That’s why Monday’s total solar eclipse passing over the entire mainland U.S. is such a big deal! Don’t let Neil deGrasse Tyson put a damper on it!

 

Predicting Eclipses

It is true that for centuries solar eclipses were thought of as omens and bringers of terrible things by many human societies. But once we figured out that they were predictable, we quickly used them to learn about the universe. The first predicted eclipse was done by Thales of ancient Greece around 610 or 585 BCE. Thales made the prediction using the idea of deductive geometry borrowed from the Egyptians. Euclid, much later, formalized this into what is now known as Euclidean Geometry. The historical record shows that Thales’s prediction only worked one time though because there are no other accounts of anyone successfully predicting an eclipse until Ptolemy used Euclidean geometry in 150 CE.

 

So how can scientists use this periodic alignment of celestial bodies to their advantage? The Sun is a pretty reliable part of our day, so having it gone for a few moments allows us to study the reaction of animals to an abrupt change in their environment. You’ll hear birds stop singing and frogs and crickets will begin chirping as the sky darkens. Mammals will begin their bedtime rituals also. But we can learn the most about the Sun itself from a solar eclipse.

 

Image of the corona created by placing a disc over the Sun to mimic a solar eclipse. These instruments, called coronagraphs, still allow a little sunlight to get through which can mess up measurements of the corona. So scientists still rely on real deal total solar eclipses to study the corona in detail.
Image of the corona created by placing a disc over the Sun to mimic a solar eclipse. These instruments, called coronagraphs, still allow a little sunlight to get through which can mess up measurements of the corona. So scientists still rely on real deal total solar eclipses to study the corona in detail.

Grab a Corona

The Sun has an outer atmosphere extending millions of miles above its surface called the corona. At temperatures reaching a few million degrees Fahrenheit, the corona significantly hotter than the Sun’s surface. The corona was first observed in 968 CE during a solar eclipse and for many centuries, scientists debated whether this bright wispy envelope was part of the Sun or the Moon. It wasn’t recognized as being part of the Sun until the eclipse in 1724 and then verified over a century later in 1842. Then, during 1932 and 1940 solar eclipses, scientists determined that the corona is significantly hotter than the surface of the Sun. Iron atoms in the corona are stripped of their electrons, which can only happen if the atoms are heated to millions of degrees. This discovery still summons solar physicists to all parts of the planet to observe solar eclipses. This solar eclipse is no different. They’re still not sure why the corona is so hot.

 

Get You Some Flare

Solar eclipses also allow scientists to study another extremity of the Sun, solar flares. Solar flares or prominences are as spectacular as they are dangerous– especially today. They can disrupt satellites and other communications devices as well as short out electrical grids. So it is crucial that we understand as much as we can about them. The first solar prominence was observed, with the naked eye, during a partial solar eclipse in 334 CE. Knowing this probably would have helped Birger Wassenius during the total solar eclipse in 1733. He noticed solar flares but suspected they were coming from the Moon. It wasn’t until a solar eclipse in 1842 that scientists verified the ejections were coming from the Sun.

 

The Sun goes through cycles of solar flare activity about every 11 years. This year, the Sun is approaching a low point in its activity, so scientists will use this total eclipse to study how flares differ from when the Sun is more active.

 

Other Notable Discoveries Thanks to Solar Eclipses

In 1868 the element Helium was discovered in the Sun’s light during the 1868 and 1869 solar eclipses and named after the Sun (Helios = Sun in Greek). Helium wasn’t identified on Earth until 1895. Another big win for physics came during the 1919 solar eclipse. Scientists used the darkened sky to verify that the Sun is massive enough to bend the light of faraway stars before it reaches us. Stars that should have been behind the Sun– and therefore not visible during the eclipse– were clearly seen. This proved part of Einstein’s theory of relativity that massive objects bend space around them.

 

Solar eclipses are awe inspiring and also useful to science. So make sure you grab your eclipse glasses or pinhole cameras or fists and get out there!

 

The WTF Star: Alien Mega Structure or Mega Version of Jupiter System?

 

JoEllen McBride, PhD

 

The Kepler telescope, despite technical issues, has observed over 100,000 stars in our galaxy. Its database is full of stars that show the tell-tale sign of an orbiting planet– a periodic and repeatable dimming of the starlight. But one stellar dimming sequence doesn’t follow the expected protocol and it has astronomers getting creative to explain why.

 

Flux Lost

Tabby’s star, or more fondly, the WTF (Where’s the Flux?) star, is a yellow star slightly larger than our Sun located over 1200 light-years away in the constellation Cygnus the Swan. You can’t see it with your eyes but looking through a small 5-inch telescope you can see it just fine.

 

Kepler continuously observed the region of space where WTF lives from 2009 to 2013. Then in 2015, Citizen scientists analyzing the data noticed something very peculiar about WTF’s brightness. In March of 2011, the star dimmed by 22% of its original brightness, suggesting something big was passing in front of it. Then 700 days later in 2013, the star dimmed significantly again, but this time did so irregularly– suggesting that not just one but many large objects were passing in front of the star. This is where the science gets interesting.

 

By JohnPassos (Own work) CC BY-SA 4.0, via Wikimedia Commons Light curve for Tabby’s star.
By JohnPassos (Own work) CC BY-SA 4.0, via Wikimedia Commons
Light curve for Tabby’s star.

 

When astronomers study the light from stars we create graphs that are called light curves. Light curves describe how the brightness of a star changes over a period of time. We choose a star, take images of it periodically and measure how bright it is. If the star’s brightness decreases, we will record a lower brightness value than in previous measurements.

 

Usually, when a star has planets orbiting it, the dimming will be periodic– tied to the orbit of the planet. So we will measure a smooth dip in the brightness of the star at regular intervals as the planet passes in front. What’s so spectacular about WTF’s brightness is that there is a single, smooth dip in brightness followed 700 days later by  irregular but large decreases that lasted for 100 days before the brightness returned back to normal levels.

 

After ruling out issues with the Kepler telescope and the variability of WTF, the lead scientists considered more celestial explanations for the irregular dimming. Debris from a violent collision like the one that formed our Moon would probably create enough large particles to recreate the dimming– but the likelihood of us catching such a one-off event is extremely small. A large conglomerate of comet fragments also seemed like a reasonable and likely cause. But we’ve never observed this before so can only make educated guesses as to what that light curve would look like.

 

Other scientists have jumped in on the task of explaining these dips with suggestions ranging from weird internal variations with the WTF star itself to unfinished alien megastructures. But recently, a group of researchers has proposed an explanation that’s a little more familiar and easily testable.

 

Follow the Gravity Train

To understand their proposal, we need to discuss a little-known fact (at least, I didn’t know this) about our solar system’s largest planet, Jupiter. All massive bodies in our solar system exert a gravitational force on other massive bodies. If we think of space as a bed sheet held taut at its corners and place a bowling ball at the center, the ball would create a pit or well in the sheet due to the mass of the ball. If we then place a baseball somewhere else on the sheet, the sheet will also bend due to the mass of the baseball. The larger well in the sheet due to the bowling ball will overlap in some places with the well in the sheet due to the baseball. This is sort of how gravitational forces interact with each other.

 

But space is a bit more complicated. The interaction of the gravitational forces of two massive bodies ends up creating what are known as Lagrange points. In our sheet analogy, these would appear as five additional wells created at specific locations around the bowling ball-baseball system. In space, these points orbit the more massive body at the same speed as the smaller body. Any objects living at these points are stuck following the smaller body around the larger one, never catching up or falling behind.

 

In the case of the Sun-Jupiter system, there are three Lagrange points that lie along Jupiter’s orbit and are home to thousands of asteroids. The two large ”Trojan” swarms are located on either side of Jupiter in its orbit around the Sun and the smaller “Hilda” swarm is always located on the opposite side of the Sun from Jupiter.

 

There is evidence for Trojan-type regions in other exoplanet systems and planet formation theory shows that these regions can exist long after planets form in solar systems. So this makes their detection more probable than one-off events like planetary collisions or never observed events like swarms of comet fragments.

 

Computer, Enhance

Researchers in Spain took a known idea and made it bigger to explain the weird dimming of the WTF star. Their proposal suggests the first, smoother dimming event is due to a large, ringed planet– almost five time larger than Jupiter. This large planet would also have larger Trojan swarms which would explain the irregular dips in brightness 700 days later. Since the Jovian system has two Trojan regions, the astronomers expect there to be another irregular dimming episode again in February 2021 which would correspond to the second Trojan region. Then two years later in 2023, the giant ringed planet should pass in front of the star again, starting the approximately 12 year cycle over.

 

Their hypothesis even accounts for a smaller May 2017 dimming event which occurred at the same time their theoretical planet would have been passing behind the WTF star. If this system is similar to Jupiter, the dimming could be explained by a Hilda-like swarm of asteroids which would dim the star but not as significantly as the Trojan swarm.

 

You should still hold some reservations about this prediction though. The number of asteroids needed to produce such a large dimming is huge– like the same mass as Jupiter huge. No one has a clue if this sort of configuration would even be stable. The team is working on a computer model for the system and plans on releasing those results in a forthcoming paper. But the key to a successful hypothesis is that it is easily testable and the Trojan hypothesis gives us something to look forward to in 2021. We only have to wait 4 years to see if these researchers are right or if we need to go back to the drawing board to figure out what’s going on with the WTF star.

Halos on Mars

By JoEllen McBride, PhD

Curiosity Discovery Suggests Early Mars Environment Suitable for Life Longer Than Previously Thought.

 

We have been searching desperately for evidence of life on Mars since the first Viking lander touched down in 1976. So far we’ve come up empty-handed but a recent finding from the Curiosity rover has refueled scientists’ hopes.

 

NASA’s Curiosity rover is currently puttering along the Martian surface in Gale Crater. Its mission is to determine whether Mars ever had an environment suitable for life. The clays and by-products of reactions between water and sulfuric acid (a.k.a. sulfates) that fill the crater are evidence that it once held a lake that dried up early in the planet’s history. Using its suite of instruments, Curiosity is digging, sifting and burning the soil for clues to whether the wet environment of a young Mars could ever give rise to life.

 

On Tuesday, scientists announced that they discovered evidence that groundwater existed in Gale Crater long after the lake dried up. Curiosity noticed lighter colored rock surrounding fractures in the crater which scientists recognized as a tell-tale sign of groundwater. As water flows underground on Earth, oxygen atoms from the water combine with other minerals found in the rock. The newly-formed molecules are then transported by the flowing water and absorbed by the surrounding rock. This process creates ‘halos’ within the rock that often have different coloration and composition than the original rock.

 

Curiosity used its laser instrument to analyze the composition of the lighter colored rock in Gale Crater and reported that it was full of silicates. This particular region of the crater contains rock that was not present at the same time as the lake and does not contain the minerals necessary to produce silicates. So the only way these silicates could be present is if they were transported there from older rock. Using what they know about groundwater processes on Earth, NASA scientists determined that groundwater must have reacted with silicon present in older rock creating the silicates. These new minerals then flowed to the younger bedrock and seeped in resulting in the halos Curiosity discovered. The time it would take these halos to form provide strong evidence that groundwater persisted in Gale Crater much longer than previously thought.

 

Credit: NASA/JPL-Caltech Image from Curiosity of the lighter colored halos surrounding fractures in Gale Crater.
Credit: NASA/JPL-Caltech Image from Curiosity of the lighter colored halos surrounding fractures in Gale Crater.

This news also comes on the heels of the first discovery of boron by Curiosity on Mars. Boron on Earth is present in dried-up, non-acidic water beds. Finding boron on Mars suggests that the groundwater present in Gale Crater was most likely at a temperature and acidity suitable for microbial life. The combination of the longevity of groundwater and its acceptable acidity greatly increases the window for microbial life to form on young Mars.

 

These two discoveries have not only extended the time-frame for the habitability of early Mars but lead one to wonder where else groundwater was present on the planet. We hopefully won’t have to wait too long to find out. Curiosity is still going strong and NASA has already begun work on a new set of exploratory Martian robots. The next rover mission to Mars is set to launch in 2020 and will be equipped with a drill that will remove core samples of Martian soil. The samples will be stored on the planet for retrieval at a later date. What (or who) will be sent to pick up the samples is still being determined.

 

Although we haven’t found evidence for life on Mars, the hope remains. It appears Mars had the potential for life at the same time in its formation as Earth. We just have to continue looking for organic signatures in the Martian soil or determine what kept life from getting its start on the Red Planet.

 

Cassini’s Sacrifice

 

By  JoEllen McBride, PhD

Our solar system is full of potential. From Earth to the frozen surface of Pluto, hydrocarbons and other complex organic molecules are surprisingly common. With every new space mission, we find the ingredients of life on more of our celestial neighbors.

 

The newest location to add to our list of places with potential for life comes from NASA’s Cassini spacecraft which began its study of Saturn in 2004. In the 13 years that Cassini has studied Saturn and its moons, it solved many mysteries and discovered some startling similarities to our own planet.

 

Saturn, at first glance, seems nothing like Earth. It is a gas giant, full of hydrogen and helium, with a possible Earth-sized core at the center. But Cassini revealed that there are phenomena occurring in the gas giant’s atmosphere that also occur on Earth. Cassini recorded video of lightning strikes on Saturn— the first taken on a planet other than our own. Since Saturn doesn’t have interference from mountains and other land features, jet streams can flow unimpeded forming a continuous hexagonal shape at the poles. But scientists are still unsure why that specific shape is created. Saturn also develops a planet-wide storm every 30 years that just happened to show up while Cassini was around in 2011– 10 years early. From the data collected by Cassini, scientists were able to determine that the storms form in a similar way to thunderstorms on Earth. Instead of adjacent hot and cold fronts mixing on Saturn, layers of warm water vapor and cool hydrogen gasses mix. The storms take time to develop because water vapor is much heavier than hydrogen so it is normally positioned below the hydrogen fog. This gives the elevated hydrogen gas time to cool. Once it cools down enough, it becomes more dense which causes it to sink into the warmer water vapor. The two mix and voila!, a Saturnian thunderstorm is born. The storm also kicked up hydrocarbons from the lower atmosphere which surprised scientists.

 

Although Saturn probably can’t harbor life, two of Saturn’s moons, Titan and Enceladus, are ripe with the ingredients. The Cassini spacecraft made numerous orbits around Titan and even sent a probe (Huygens) down to the surface. Titan has land features similar to Earth, with lakes, mountains, ice caps, and deserts. The difference is methane and ethane are the chemical building blocks of the complex molecules found on the moon instead of carbon.

 

Enceladus was the biggest surprise to come out of the Cassini mission. This moon is essentially a smaller version of Jupiter’s moon Europa. Both are covered in a liquid ocean topped with a thick layer of ice that surrounds the moon. There is one big difference: Enceladus has hydrothermal vents deep within its oceans, just like on Earth, and these vents violently force liquid through cracks in the ice. The plumes are huge and powerful, extending hundreds of miles into space and traveling at hundreds of miles an hour. The Cassini spacecraft revealed that these plumes are chock full of hydrocarbons, which are the building blocks necessary for life. This tells scientists that there is the potential for life in the oceans of Enceladus and possibly Europa.

 

The other moons that Cassini visited revealed some startling information. Tethys has bright arcs of light which can only be seen at infrared wavelengths. Scientists are puzzled as to what they are and what is causing them. The spongy-looking moon Hyperion builds up a static charge as it tumbles around Saturn. Mimas, aka the Death Star Moon, was thought to be a dead world but shows evidence of a liquid ocean underneath its cratered surface. The moon is the same size as Enceladus but has no visible jets or plumes, so the liquid is trapped beneath the surface. Why these two moons are so different and whether Mimas’ ocean is full of hydrocarbons is something scientists hope to study in the future.

 

The potential of life in the Saturnian system is the main reason Cassini’s mission will come to a destructive end. The spacecraft is running out of fuel, meaning that scientists on Earth will eventually lose the ability to control the spacecraft. Our own planet is surrounded by defunct satellites whizzing around our planet– just waiting to crash into other orbiting objects. The scientists in charge of the mission worry that if Cassini were left to orbit Saturn, it could potentially crash into Enceladus. This could introduce foreign microbes and chemicals, devastating any microbial life on the moon or ruining the chances of it ever forming. Instead, Cassini is performing its last dance with Saturn, orbiting the planet so closely that it is between the rings and the gaseous atmosphere. After 22 orbits, the spacecraft will take a dive into Saturn’s clouds on September 15, 2017, sacrificing its own metallic body for the sake of billions of potential life forms on the moons of Saturn.

 

Once Thought Elusive, A Black Hole Will Get A Close-up

 

By JoEllen McBride, PhD

Light can’t escape it but Matthew McConaughey can use it to ‘solve gravity’. They’re the most massive things in our universe but we can’t actually see them. Black holes were theorized by Einstein in the early 1900s and have intrigued both scientists and the public for over a century. Up until recently, we could only see their effects on visible matter that gets too close but an Earth-sized telescope is about to change all that.

 

The term black hole sounds silly but it’s pretty descriptive of this invisible phenomenon. Astronomers call things black or dark because we can’t actually see them with current technology. Black holes form when a star is so massive that its own force of gravity pushes in harder than the molecules and atoms that make it up can push out. The star collapses; decreasing its size to almost nothing. But matter can’t just disappear so this incredibly small object still has mass which can exert a gravitational influence on stars or gases that get too close. If our Sun became a black hole out of nowhere (don’t worry, this can’t happen), the Earth and other planets would not notice a difference gravitationally. We’d all continue orbiting as before; things would just get a lot colder. I guess that’s one way to wash away the rain.

 

So that’s how a single black hole forms but you’ve probably heard references to ‘supermassive’ black holes before. These black holes have masses of many millions or billions of suns. So what died and made that massive of a ‘hole’? Supermassive black holes are not the product of a single object but are most likely formed by the merging together of many smaller black holes. We recently found evidence of this process from the ground based gravitational wave detector, LIGO, which can detect the waves that are produced when two smaller black holes merge. We also know supermassive black holes exist because we have seen their influence on other luminous objects such as stars and gas that’s been heated. We see jets of gas being shot out of the centers of galaxies at close to light speed. There is something incredibly massive at the center of our own galaxy that causes stars nearby to orbit at incredible speeds. The simplest explanation for these observations is that galaxies have supermassive black holes at their centers.

 

But there is another way we could ‘see’ a black hole which was impossible before this year. As stated before, light cannot escape a black hole but anything that becomes trapped in the gravitational well has to orbit for some time before it disappears. So there must be a point where we can still see material just before it’s lost forever; like an object that swirls around the edge of a whirlpool just before falling down the drain. This region is known as the event horizon and it’s basically the closest we can get to seeing a black hole. Currently, the supermassive black hole at the center of our galaxy, named Sagittarius A*, isn’t taking any material in but that doesn’t mean the event horizon is empty. Luminous material can orbit in the event horizon for a very long time, we just need to look at the right wavelength with a big enough camera.

 

The center of our galaxy is 8 kiloparsecs or 1,50,000,000,000,000,000 miles away. To put that in perspective, that’s about 1014 times larger than the distance between the U.S. coasts, 1011 times larger than the Earth-Moon distance and 100,000 times larger than the distance to the next closest star, Alpha Centauri. It’s really far away. The width of Sagittarius A*’s event horizon is estimated to be between the width of Pluto and Mercury’s orbit around our Sun. At its widest estimate, the event horizon of Sagittarius A* would span one-millionth of a degree on the sky. For comparison, the full moon spans about half a degree. So we’re gonna need a bigger telescope– an Earth-sized one.

 

Enter the Event Horizon Telescope (EHT). This network of telescopes operates at radio wavelengths and uses a technique that increases the size of a telescope without having to build a huge dish. The EHT combines telescopes in Arizona, Hawaii, Mexico, Chile, Spain and the South Pole to create an Earth-sized radio dish. A good analogy I’ve found is to picture you and five other friends are standing at various locations at the edge of a pond. You all know where you are located with respect to each other and the pond surface. Each of you also has a stopwatch and placed a bobber in the water directly in front of you. If a pebble gets dropped somewhere in the middle of the pond each of you will wait until you see the bobber start moving and begin recording the time and the up and down motions the bobber makes as the peaks and troughs of the wave passes by. After you’ve recorded enough bobs, you can meet back up with your friends to determine where the pebble was dropped and its size based on the ripples and when they reached each of your respective locations. The EHT will work similarly except the friends are telescopes pointed at Sagittarius A* and the water ripples are light waves.

 

Over 10 days at the beginning of April, these telescopes were in constant contact, monitoring the weather at each site, to coordinate their observations as best they could. Radio waves can usually penetrate everything but the wavelengths that these telescopes were looking at are blocked by water vapor, so clouds and rain mean no observing. On April 15th, they finished their run by successfully obtaining 5 days worth of observations. Now each site has to mail hard drives with their data to a central location, where the images can be properly aligned. The South Pole Telescope can only send out packages after their winter season ends in October, but data is already coming in from the other sites.

 

If everything went as planned, the images should add up to the highest resolution images ever taken of a black hole. This arrangement allows them to measure objects as small as a billionth of a degree. The estimated size of Sagittarius A*’s event horizon is larger than this, so a faint ring surrounding darkness should be visible in the final images. Hopefully, Sagittarius A* was ready for its close-up because humans are eager to see how their own depictions of black holes match up.

 

 

Want to Watch History Burn? Check Out a Meteor Shower!

 

By JoEllen McBride, PhD

 

Fireballs streaking across the sky. Falling or shooting stars catching your eye. Meteors have fascinated humans as long as we’ve kept records. Depending on the time of year, on a clear night, you can see anywhere from 2 to 16 meteors enter our atmosphere and burn up right before your eyes. If you really want a performance, you should look up during one of the many meteor showers that happen throughout the year. These shows can provide anywhere from 10 to 100 meteors an hour! But what exactly is burning up to create these cosmic showers?

 

To answer this question we need to go back in time to the formation of our solar system. Our galaxy is full of dust particles and gas. If these tiny particles get close enough they’ll be gravitationally attracted and forced to hang out together. The bigger a blob of gas and dust gets, the more gas and dust it can attract from its surroundings. As more and more particles start occupying the same space, they collide with each other causing the blob to heat up. At a high enough temperature the ball of now hot gas can fuse Hydrogen and other elements which sustains the burning orb. Our Sun formed just like this, about 5 billion years ago.

 

Any remaining gas and dust orbiting our newly created Sun coalesced into the eight planets and numerous dwarf planets and asteroids we know of today. Even though the major planets have done a pretty good job clearing out their orbits of large debris, many tiny particles and clumps of pristine dust remain and slowly orbit closer and closer to the Sun. If these 4.5 billion year old relics cross Earth’s path, our planet smashes into them and they burn up in our atmosphere. These account for many of the meteors that whiz through our atmosphere unexpectedly.

 

The predictable meteor showers, on the other hand, are a product of the gravitational influence of the larger gas giant planets. These behemoths forced many of the smaller bodies that dared to cross them out into the furthest reaches of our solar system. Instead of being kicked out of the solar system completely, a few are still gravitationally bound to the Sun in orbits that take them from out beyond the Kuiper belt to the realm of the inner planets. As these periodic visitors approach our central star, their surfaces warm, melting ice that held together clumps of ancient dust. The closer the body gets to the Sun, the more ice melts– leaving behind a trail of particulates. We humans see the destruction of these icy balls as beautiful comets that grace our night skies periodically. But the trail of dust remains long after the comet heads back to edge of our solar system.

 

The dusty remains of our cometary visitors slowly orbit the Sun along the comet’s path. There are a few well-known dust lanes that our planet plows into annually. Some of these showers produce exciting downpours with over a hundred meteors an hour and others barely produce a drip. April begins the meteor shower season and the major events for 2017 are listed below.

Shower Dates

Peak Times

(UT)

Moon Phase At Peak Progenitor
Range Peak
Lyrid (N) Apr 16-25 Aprl 22 12:00 Crescent Thatcher 1861 I
Eta Aquarid (S) Apr 19-May 28 May 6 2:00 Gibbous 1P/Halley
Delta Aquarid (S) Jul 21-Aug 23 Jul 30 6:00 First Quarter 96P/Machholz
Perseid (N) Jul 17-Aug 24 Aug 12/13 14:00/2:30 Third Quarter 109P/Swift-Tuttle
Orionid Oct 2-Nov 7 Oct 21 6:00 First Quarter 1P/Halley
Taurids Sep 7-Nov 19

Nov 10/11

Nov 4/5

12:00

Crescent

Full

2P/Encke
Leonid Nov Nov 17 17:00 New 55P/Tempel-Tuttle
Geminid Dec 4-16 Dec 14 6:30 Crescent 3200 Phaethon*
Quadrantid (N) Dec 26-Jan 10 Jan 3 14:00 Full 2003 EH1

S= best viewed from Southern Hemisphere locations

N= best viewed from Northern Hemisphere locations

*This is an asteroid with a weird orbit that takes it very close to the Sun!

 

Here is a list of things you can do to ensure the best meteor viewing experience.

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  • Check the weather. If it’s going to be completely overcast your meteor shower is ruined.
  • Is the Moon up? Is it more than a crescent? If the answer to both of these is yes you will have a more difficult time seeing meteors. The big, bright ones will still shine through but those are rare.
  • When trying to catch a meteor shower, make sure the constellation the shower will radiate from is actually up that night. Hint: Meteor showers are named after the constellation they appear to radiate from.
  • You need the darkest skies possible. So get away from cities and towns. The International Dark Sky Association has a dark sky place finder you can use. Your best bet is to find an empty field far from man-made light pollution.
  • Make sure trees and buildings aren’t obscuring your view.
  • It takes about 30 minutes for your eyes to completely adjust to the darkness. If you have a flashlight, cover it with red photography gel to help keep your eyes adjusted.
  • Ditch the cell phone. Cell phones ruin your night vision. Every time you look at your screen your eyes have to readapt to the dark when you look back up at the sky. There are apps you can download that dim your screen (iPhone, Android) but your eyes will still need time to adjust to the darkness if you glance at your phone. Also looking away almost guarantees the biggest meteor will streak by at just that moment.
  • Dress comfortably. In the fall and winter, wear warm clothes and have hot chocolate and coffee on hand. In the spring and summer, some cool beverages will enhance your experience. Make sure you have blankets to lay on or comfortable chairs so you can keep your eyes on the skies.

[/unordered_list]

Follow these guidelines and you’ll have the best chance of watching 4.5 billion years of history burn up before your very eyes.

A Short History of Fast Radio Bursts

 

By JoEllen McBride, PhD

Humans have gazed at the stars since the beginning of recorded history. Astronomy was the first scientific field our distant ancestors recorded information about. Even now, after thousands of years of study, we’re still discovering new things about the cosmos.

Fast radio bursts (FRBs) are the most recent astronomical mystery. These short-lived, powerful signals from space occur at frequencies you can pick up with a ham radio. But don’t brush the dust off your amateur radio enthusiast kit just yet. Although they are powerful, they do not occur frequently and happen incredibly fast. Which is exactly why astronomers only recently noticed them. The first FRB was discovered in 2007 from data taken in 2001. The majority of FRBs are found in old data. Their short duration meant astronomers overlooked them as background signals but closer inspection revealed a property unique to radio signals originating from outside our galaxy.

 

Signal or Noise?

Radio signals are light waves with very long wavelengths and low frequencies. Visible light (the wavelengths of light that bounce off objects, hit our eyes and allow us to see) happens on wavelengths that are a few hundred times smaller than the thickness of your hair. The wavelength of radio waves can be anywhere from a centimeter to kilometers long. The longer the wavelength, the lower the frequency  and more the signal is delayed by free-floating space particles. This is because space is not a perfect vacuum. There is dust, atoms, electrons and all kinds of small particles floating around out there. As light travels through space, it can be slowed down by these loitering particulates. Larger distances mean more chances for the light to interact with particles and these interactions are strongest at the lowest frequencies where radio waves happen.

Radio signals from within our own galaxy are close enough that they are not really affected by this delay. But sources far outside of the Milky Way have very large distances to travel so by the time the signal reaches our telescopes, it has interacted with many particles. This produces a streak or a ‘whistle’ where the higher radio frequencies in the signal reach our telescopes first and the lower ones arrive shortly afterwards.

When astronomers started noticing these whistles at unexpected frequencies, they no longer believed they were background noise but signals from the far reaches of space. They needed another piece to the puzzle though to determine exactly what was causing these interstellar calls.

 

It Takes Two to Find a FRB

The signals discovered in previous data appeared to be one-and-done events, which meant they could not be observed again with a bigger telescope to get a more precise location. Without a precise position on the sky, astronomers couldn’t tell where the signals were coming from, so had no idea what was producing them. What astronomers needed was a signal detected by two different telescopes at the same time. One telescope to broadly search for the signal and a second, much larger telescope to accurately determine its location. So they began to meticulously watch the sky for new FRBs. The first real-time observation of an FRB was in May of 2014. Although it was observed by only one telescope so its precise location was unknown, it gave astronomers a way to detect future ‘live’ bursts. In May and June of 2015 a search by another team of astronomers yielded the first ever repeating FRB.

The Arecibo radio telescope (yes the one from Goldeneye) detected the first signals then they requested follow-up observations from the Very Large Array to more precisely pin-down the location. Once they had a location, yet another team of astronomers could take pictures at visible frequencies to see what was lurking in that region of space. They found a teeny tiny galaxy, known as a dwarf galaxy, at a distance of 3 billion light years from Earth. This galaxy is full of the cold gas necessary to create new stars which means many stars are being born and the huge, bright ones are living quickly and dying.

 

Who or What is Calling Us?

Where the FRBs are coming from is important because it allows astronomers to pick between the two plausible theories for what causes FRBs. The energy produced by these bursts is impressive, so the most likely culprits take us into the realm of the small and massive: supermassive black holes (SMBH) and neutron stars. One idea suggests that FRBs could be the result of stars or gas falling into the SMBH at the center of every galaxy. If this were the case, we would expect the FRBs to occur in the central regions of a galaxy, not near the edges. Neutron stars, on the other hand, are formed after the death of massive stars. These stars are typically 10 to 30 times more massive than our Sun, so do not live for long. Astronomers expect a galaxy creating lots of new stars to also create lots of neutron stars as the most massive stars die first. Star formation can occur anywhere in a galaxy but is most commonly observed in the outer regions.

This repeat FRB is located pretty far from the center of a galaxy going through a period of intense star birth so this lends credence to neutron stars being the source. Of course, we are looking at a single data point here. There is no reason to suspect that there is a single cause for FRBs. We need more real-time observations of FRBs so we can figure out where they are located and whether or not they always come from dwarf galaxies. FRB searches have been added to three radio frequency surveys, known as CHIME, UTMOST and HIRAX, that will detect and locate these powerful signals with great precision.

It looks like we can continue to look forward to another few millennia of cosmic discoveries.

Twinkle, Twinkle, Christmas Star, How I Wonder What You Are!

 

By Knicole Colon, PhD

While not all people celebrate Christmas, it is commonly known that in the Christian religion, the “Christmas Star” or the “Star of Bethlehem” is what led the wise men to find the newborn baby Jesus in Bethlehem. The story goes that the wise men saw the Christmas Star and believed it signified the birth of the King of the Jews. They traveled to Jerusalem to ask King Herod where they might find such a child, and the king’s advisors informed him that Bethlehem was the likely birthplace of the baby Jesus. So, the wise men traveled to Bethlehem, and indeed found the baby Jesus there. It is said in the Gospel of Matthew that “the star which [the wise men] had seen in the East went before them, till it came and stood over where the young Child was.” The wise men were overjoyed to find that the star marked the location of the baby Jesus because it meant they had indeed found the Messiah.

I find this story interesting because, as an astronomer, I cannot help but wonder if the Christmas Star was a real astronomical object. I am not the first to wonder this by any means. In the early 1600s, the astronomer Johannes Kepler calculated that a conjunction of Jupiter and Saturn occurred in the year of Jesus’ birth. Such a conjunction (i.e. that the planets appear to be close in the sky) could have made the two planets appear as one bright object in the sky. However, recent calculations suggest that Jupiter and Saturn were far enough apart that they would not have appeared as an exceptionally bright single object. However, conjunctions between Venus (the brightest planet in the sky) and Jupiter might have instead been the source of the Christmas Star. The astronomical timeline of the conjunctions of these two planets fits the story pretty well, though there is still some controversy since these planets (which would appear as a single planet in the sky at this time) would have been visible only around sunset and not through the night. Still, such conjunctions are rare, so we are left with an almost supernatural feeling if the conjunctions really did happen around the time of Jesus’ birth. What are the odds of such rare events happening at the same time as the birth of someone who is arguably one of the most famous and important people in history?

However, it has also been suggested that the so-called star was actually a comet. Halley’s comet was visible around that time frame (12 BC) as was another bright object noted by Chinese and Korean astronomers (around 5 BC). While of unknown origin, the object seen by the Chinese and Koreans was apparently observed for over two months and did not appear to move. Such an object might have not been a comet but could have been a nova (a sudden brightening of a white dwarf star due to accretion processes that effectively cause an explosion and an increase in brightness that lasts days to weeks). While a comet or nova is a possible explanation for the Christmas Star, historians do not believe a cometary origin is likely. Comets were seen as bad omens back then, and certainly no one would associate the birth of Jesus with a bad omen.

An alternate explanation for the Christmas Star is that it was not a nova but rather a supernova, an explosion that indicates the death of a massive star. In this stage, a star will be extremely luminous as it expels most of its material. The remnant of such an event is either a neutron star or a black hole. Since supernovae are very bright and can be visible for several weeks or even months, it is probable that such an event would be noted by anyone observing the sky at the time of Jesus’ birth. However, it is difficult for astronomers in the present-day to say whether or not a supernova took place at that time, and there appears to be no records of such an event (which most certainly would have been noticed by someone, considering that supernovae are so bright that they can even be seen during the day when the sun is out!).

There is also the possibility that the Christmas Star was simply an ordinary star. But, astronomers can determine how the night sky appeared at the time of Jesus’ birth, and there is no obvious bright star that would be considered as a guide for the wise men. However, a part of the problem with understanding the origin of the Christmas Star is that the exact year of Jesus’ birth is not known. Based on various records, it is now believed to be between 7 BC and 2 BC, but there is some uncertainty there as even today different sources give different ranges of years for his birth. That said, something like Halley’s Comet, which appeared earlier in 12 BC, still seems an unlikely candidate for the Christmas Star.

Of course, some think the star may simply be a fictional aspect of the story of the birth of Jesus. This is because there are many facts that don’t add up. For instance, since Jerusalem and Bethlehem are just 10 km apart, a star would not be needed to guide the wise men in their travels. It is also likely that Jesus was not born in Bethlehem, but rather in Nazareth or elsewhere. The location of his birth would affect what star (if any) the wise men followed in their travels. Finally, we cannot rule out the possibility that the Christmas Star was of a supernatural origin, and truly occurred to signify the birth of a king. Furthermore, in some stories, the star was actually an angel. Needless to say, there is quite a bit of controversy in deciphering the nativity story. At this point, historians and astronomers have done pretty much all they can to solve this mystery. We may never know the true origin of the Christmas Star, but don’t let that stop you from celebrating Christmas (if you do that). To everyone else, happy holidays!

Space: the Spooky Frontier

 

By Knicole Colon, PhD

Have you ever thought about how spooky space is? Sure, the stars in the night sky are beautiful to look at, and it’s amazing to see the Moon and know that mankind has (literally) left footprints there. But, when you really think about it, you will realize that space is incredibly spooky.

First of all, the Sun is an unfathomably hot ball of gas that randomly emits bursts of radiation (known as flares). Luckily, the Earth’s atmosphere protects us from this radiation. Satellites orbiting above the Earth aren’t so lucky. The radiation from the Sun can affect their operation and effectively cause radio blackouts. Such blackouts can interrupt GPS and other satellites that help us communicate. Considering that we are all addicted to constant communication through our cell phones and the internet, this is pretty scary. On the plus side, such intense flares are really not that common (so try not to get too creeped out by this).

Besides the Sun, there are quite a few asteroids out there that could swing by and impact Earth. This really is a rare occurrence, but it’s still creepy to think of some impact event that is explosive enough to send us back to the stone age. In this day and age, anything that deprives us of technology is pretty scary. And then there are things like black holes or stars that explode and go supernova that could easily destroy the entire Earth. We wouldn’t even stand a chance against them. Luckily astronomers don’t think these will affect us anytime soon (at least not in our lifetime).

There are also some pretty creepy aspects of space travel. In particular, the movie Gravity comes to mind. From the previews of the movie alone, you could see how an astronaut may end up in a really bad situation – floating in space, unconnected from everything, destined to die alone. I definitely like my alone time now and again, but floating into nothingness, waiting to die? Not so fun.

Thinking of the bigger picture and just how vast the universe is, it is quite spooky to think of how small and insignificant each human is in the grand scheme of things. Space is big. Absolutely enormously and insanely big. It takes decades just to travel to the outer edges of the Solar System from Earth, so imagine how long it would take to travel to the nearest star (hint: it would take tens of thousands of years with current technology). Not only that, but what else is out there (besides scary rogue asteroids and black holes)? Are there other intelligent beings, devising a way to attack us? Starting in the late 1800s, people truly believed that Martians existed. People saw “canals” and an infamous “face” on Mars that they thought had been constructed by some intelligent life form. These were actually optical illusions (and people seeing what they wanted to see), but still these observations led to stories like “War of the Worlds” where the main goal of Martians was apparently to destroy humans. We now know that no intelligent life exists on Mars (which is probably good since it means there are no interplanetary wars we have to watch out for). But, what if there is no other intelligent life at all? How scary is it to think we might be alone in the universe?

To end things on a positive note, at least from this post you know you are not alone in thinking that space is a really spooky frontier.

Boldly Going Where No One Has Gone Before

 

By Knicole Colon, PhD

Launched more than a decade ago, the European Space Agency’s Rosetta spacecraft  has finally reached its destination. For the first time, humans have maneuvered a spacecraft through the vastness of space to meet up with a comet and, believe it or not, that spacecraft will soon enter in orbit around that comet. Rosetta will then travel along with the comet for over a year and provide us with never-before-seen access to the life of a comet.

This now famous comet is known as Comet 67P/Churyumov-Gerasimernko. Comets are generally named for their discoverers, hence the lengthy surnames. This comet (which we will call 67P for short) is also the 67th periodic comet discovered, and it was discovered in 1969. The periodic part refers to the orbit of the comet. Periodic comets will continue to orbit the Sun as long as they aren’t burned alive (like Comet ISON was in late 2013) or don’t collide with other objects in the Solar System (like Comet Shoemaker-Levy 9 did when it collided with Jupiter in 1994). For those comets that have highly elliptical orbits and survive dangerously close encounters to the Sun, the comet’s proximity to the Sun is what results in the evaporation of cometary material. This effectively creates a temporary atmosphere around the comet, which can form the cometary tails that we all know and love.

Besides having exciting deaths and awesome-looking tails, comets are quite interesting objects since they contain complex organic compounds made up of carbon, hydrogen, oxygen, and nitrogen. It has been hypothesized that the building blocks of life on Earth came from comets that deposited organic molecules and water on Earth. If this is the case, then we need to understand how exactly this happened. Given the high interest in the composition of comets, they have been heavily studied for years. For example, there have been a number of spacecraft that had flybys of different comets in the past. However, this is the first time that a spacecraft will enter in orbit and travel along with a comet for a significant amount of time. We will be able to see firsthand how a frozen comet (that potentially contains original material from the formation of the Solar System) is affected over time by the Sun. On top of that, the Rosetta spacecraft is home to a little lander called Philae which will in fact land on the nucleus of Comet 67P this November. Prior to landing, data from Rosetta will help astronomers determine an optimal and safe landing site for Philae. This may be a bit more difficult than anticipated, given that as Rosetta approached Comet 67P, it discovered that the comet has a double nucleus with very variable terrain (as shown here  and here).

Once Philae has landed and secured itself to the comet’s surface with harpoons (necessary due to the extremely low surface gravity, estimated to be about one ten-thousandth of Earth’s surface gravity), it will send back to Earth an incredible amount of information. Philae has ten instruments installed to do this (not to mention the numerous instruments installed on Rosetta). Some of these will take close-up pictures and run tests to determine the chemical composition of the comet’s surface. A drill system will obtain soil samples at different depths and a mass spectrometer will analyze those samples. A radar will be used to determine the internal structure of the comet. Needless to say, these little spacecrafts are going to tell us a great deal about this comet.

Currently, the Rosetta spacecraft is less than 62 miles from the comet’s surface. By mid-September it will be just 19 miles from the surface, and then it will be maneuvered to officially enter orbit around the comet at that time. Philae’s landing on the surface is currently scheduled for November 2014, so keep an eye out for news on that. Just like landing men on the Moon and rovers on Mars, this landing will be one for the record books. Beyond that, stay tuned for when Comet 67P has its closest approach to the Sun in August 2015, with Rosetta in tow.