Perseid Meteor to Light Up Night Sky

The Perseids are here! This annual meteor shower is one of the best and brightest, but this year it’s predicted to be even more spectacular. So, if you’re in a dark place tonight, look up. You may see a 4.5-billion-year-old remnant from the solar system burn up in our atmosphere.

Astronaut Ron Garan took this picture from the International Space Station. It shows a Comet Swift-Tuttle particle burning up in Earth's atmosphere. Credit: Ron Garan, NASA

Astronaut Ron Garan took this picture from the International Space Station. It shows a Comet Swift-Tuttle particle burning up in Earth’s atmosphere. Credit: Ron Garan, NASA

Comets are conglomerations of ice and dust leftover from our solar system’s formation. A lot of the material that swirled around our young sun developed into the eight planets and numerous dwarf planets and asteroids. Some of the smaller bodies that formed were forced into elongated orbits by gravitational interactions with the larger planets. These trajectories take them out to the extreme edges of our solar system, then the Sun’s gravitational embrace usually pulls them back in for a warm hug.

In 1992, Comet Swift-Tuttle passed through Earth’s orbit as it came in for a visit. As the comet approached the Sun, the rise in temperature vaporized some of the ice, leaving a trail of small chucks of rock and ice. These icy particles still remain in the inner solar system today.

Every year, between mid-July and mid-August, the Earth slams into the debris trail left by Comet Swift-Tuttle at 67,000 mph. As the ice and rock enters our atmosphere, it burns up, and a meteor shower occurs. The streaks of light appear to originate from the constellation Perseus — hence the name Perseids. Earth will pass through the densest part of the trail on August 12th , and this year’s shower is predicted to be more amazing than previous years.

Computer simulations of Jupiter’s gravitational influence on the icy trail show that the gas giant has caused the material in Earth’s path to bunch up. This means that instead of the normal peak activity of 60 meteors per hour, it could double to 120 meteors per hour! Even though more meteors are predicted this year, the debris that makes them is incredibly small — about the size of the grain of sand. This means you need to find a dark place, away from city lights, to get the best views.

In order to see the most meteors you need to give your eyes about 30 minutes to adapt to the dark. Use a flashlight with red photography gel over the beam to help keep your eyes dark-adjusted. You also need to put down the cell phone. Any concentrated light will undo all the sensitivity you gained by letting your eyes adapt. There are apps you can download that filter out the bright blue light emitted from your screen, but it will still take some time for your eyes to readjust to the darkness every time you check your Facebook.

The constellation Perseus rises in the northeast between 9 and 10 PM local time. On August 12th, the Moon will be three-fourths illuminated, meaning it will be pretty bright. If you want to get the most out of your Perseid viewing experience, wait until the Moon sets around 1 AM in Chapel Hill.

Even if you can’t catch the peak, Earth will be passing through the path of Comet Swift-Tuttle through August 24th. So, there’s a good chance you can watch 4.5 billion years of history burn.

Peer edited by Caddy Hobbs.

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The End of A Planetary Road Trip

Recently, NASA’s JUNO spacecraft slowed down by 1,212 miles per hour in a carefully coordinated 35 minute maneuver. This slowdown is similar to you slamming on the brakes to stop your car on the highway in 2 seconds. Braking to the exact right speed allowed JUNO to be captured by Jupiter’s gravity and start orbiting the giant planet. Just like a long road trip, as spacecraft travel from Earth to their destination, they often cruise at high speed to reach their destination in a relatively short amount of time. But that means if you want to orbit or land on the planet, you must slow down a lot. Here are three ways NASA has dealt with the tricky task of ending a planetary road trip.

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The Physics Behind the Newest OK Go Video

I first heard of the band OK Go when they released their music video for ‘Here It Goes Again,’ which features the band members cruising back and forth over treadmills. I soon discovered that many of their other music videos are equally captivating and involve cool applications of physics. For example, their video for ‘This Too Shall Pass’ involves an elaborate Rube Goldberg machine, a complex device designed to perform a simple task. This is the same type of device the kids use in ‘The Goonies’ to open the gate for Chunk.

A few weeks ago, they released the video for their song ‘Upside Down & Inside Out,’ which might be the most fun so far. This video involves the band members floating about in an airplane like astronauts. Go ahead and watch it, then continue below and I will explain some of the physics behind the video.

How They Did It

The flight path of aircraft

The flight path of aircraft simulating weightlessness. Image credit: NASA

First of all, the members of OK Go are not in space or in zero gravity. They are in a plane flying at altitudes similar to commercial aircraft. This plane, however, flies in parabolic trajectories, as shown in the figure, to simulate weightlessness within the plane. NASA has a similar plane called the Weightless Wonder to help astronauts train and perform science experiments. The figure to the left shows how this works. As the plane starts to fly higher, everything on board feels heavier than normal (0-20 seconds in the image). Once the plane reaches a certain altitude, the pilots slow down the engines and the plane begins to move only under the influence of gravity (20-45 seconds in the image). This is just like what happens when you throw a ball into the air. You apply a force to throw the ball, but once it leaves your hand, it moves only under the influence of gravity. It goes up a little ways before coming back down.

In the OK Go video, the people and objects inside the plane are like the ball thrown into the air. But since the people are moving at the same rate as the plane, it simulates weightlessness. You do not feel this way when you skydive, for example, because you can feel the air pushing on you as you fall down. Inside the plane, however, you feel weightless because the air is falling at the same rate as you.

Typically, these parabolic trajectories that create weightlessness can only last up to about 30 seconds. For a song that is 3:21 long, this means OK Go had to shoot the video in multiple segments and then edit it to make it look smooth. You can see that at certain times everything falls to the floor of the plane (most obvious at 2:03, 2:27, 2:46, and 3:08). At these moments the plane is coming out of the parabola so gravity is, in a way, turning back on. OK Go released a short video describing some of the challenges they faced filming in this type of environment and how they solved those problems.

 Other Neat Physics

This whole video is full of great examples of introductory physics; I bet many teachers are already writing questions based on this video. Here are three of my favorite parts of this video from a physics point-of-view.

  1. One of the coolest visual aspects of the video is at 2:51 when the balloons full of paint appear. The band members start popping the balloons and paint goes everywhere. On Earth, if you pop a balloon full of anything, the contents are going to fall straight down to the ground. But in weightlessness, the direction the paint goes depends on a few things.
    The lead singer first pops a purple balloon with orange paint that he holds in his hand. He takes his finger, pushes almost straight down to pop the balloon and the orange paint moves upwards. It moves up because of the conservation of momentum. Since the balloon is stationary and his hands moves downwards, the paint goes up. In the same situation on Earth, the paint would try to go up as well. But the effect of gravity is strong enough to overcome this motion and would force the paint to fall to the ground.
    You have experienced something similar to this if you have ever tried to push someone while rollerblading or ice skating. If you are standing still and give someone a push, you will start moving the opposite way.
  2. At 1:38 the flight attendant in front starts spinning with her legs out before bringing them in and spinning more quickly. She is conversing her angular momentum, which is exactly the same thing ice skaters do when they spin.  If you are spinning and have your arms out you will spin faster when you bring them in, and vice versa. You can do this in most office chairs too, but it is helpful to have a friend spin you.
  3. Disco balls are released around 2:37. You can see a couple of them bouncing off each other and all of them hit the walls of the airplane. Just like in the game of pool, the direction they each travel depends on the speed and direction of the collision. Calculating the trajectories of pool balls is a common physics question. Calculating the trajectories of the disco balls would be a fun extension of that.

Like most OK Go videos, this one took a lot of work to put together. They have released a few videos detailing how it all came together. This band keeps finding ways to include great physics demonstrations in their videos.


 

Peer edited by Kayleigh O’Keeffe & Ashley Fuller

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Biology and Physics Meet in the Middle

Scientists thrive on “aha” moments— breakthroughs in knowledge that come from careful planning or perhaps fortuitous luck. For a team of researchers led by Josh Lawrimore, a fourth-year graduate student in Kerry Bloom’s lab at UNC, their “aha” moment came about by approaching their research question in a new way.

Josh’s research is focused on what happens to a chromosome—a long molecule of DNA wrapped around proteins—when a parent cell divides into two daughter cells. To study chromosomes, the Bloom lab uses baker’s yeast as an experimental model. The centromere region in yeast cells has been well-studied, and their chromosomes are similar in structure to human chromosomes. Amazingly, through working with this simple organism, Josh has solved a long-standing mystery in the field of cell biology.

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Discovering New Horizons

Humans need to explore. Not because it is in our DNA – the gene for exploration hasn’t been discovered yet – but because it is essential to our survival and well-being as a species. Scarcity of food and changing weather most likely pushed our ancient ancestors from their African homelands. Religious persecution forced many to flee Europe in search of a safe place to practice. The political pressure of the Cold War prompted us to send men to the Moon. The exploration of space is often sold as “the final frontier,” but there are real discoveries and knowledge attained from these expeditions that can benefit our species.

What We’ve Learned From Other Planets

Information gathered from Venus’s atmosphere showed us the effects that chlorofluorocarbons (CFCs) have on Earth’s ozone layer. Planetary scientists were trying to understand how CO2 remained present in such large quantities in the atmosphere of Venus. They thought chlorine and fluorine molecules may have had something to do with it. Models that incorporated reaction rates between chlorine, fluorine and O3 did not significantly affect the amount of CO2 trapped in Venus’ atmosphere, but when the same reaction rates were modeled in Earth-like conditions, the depletion of the ozone layer was discovered. This led to a worldwide effort to reduce CFCs in Earth’s atmosphere.
Measuring the effects of dust storms on Mars prompted a team of scientists to model the effects of a global nuclear war. During the Mariner 9 mission to Mars, a planet-wide dust storm obscured the surface of the planet. Instruments on the probe measured temperatures in the upper atmosphere higher than they should have been and temperatures at the surface much lower than expected. Theoretical models at the time predicted that large amounts of debris would be lifted into the atmosphere during nuclear explosions that could block sunlight from reaching Earth for an extended period of time. Using the Martian data and the theoretical nuclear dust clouds, a team of 5 scientists (Richard Turco, Owen Toon, Thomas Ackerman, James Pollack and Carl Sagan) calculated the effect this dirt shroud would have on our planet. They dubbed the results a “Nuclear Winter” and used this information to convince politicians to use caution when discussing nuclear solutions and to reduce our nuclear weapons stockpile.
The human race has now sent probes to all of the major planets and some of their moons. Each mission has accrued a wealth of data that may once again be used to benefit our planet. The most recent mission that we are receiving data from is the New Horizons mission to Pluto.

New Horizons

Artist conception of New Horizons Spacecraft. Credits: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Artist conception of New Horizons Spacecraft.
Credits: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Launched on January 19, 2006, the New Horizons satellite has a suite of instruments ready to tackle many scientific questions concerning planetary bodies that lie beyond Neptune in the region known as the Kuiper Belt. These instruments will study the geology, temperature and composition of the surface of these pristine worlds. The satellite will initially study Pluto and its moon Charon, then continue deeper into the Kuiper Belt to study other icy bodies. Some of the major questions New Horizons will answer are:
  • Why are Kuiper Belt Objects (KBOs) composed differently than the major planets?
  • What formation mechanisms occurred in the Kuiper belt?
  • How did bombardment of KBOs change throughout the Solar System’s history?
  • How did the Earth lose its primordial atmosphere?
As of August 2006, Pluto is no longer considered a major planet. But that does not affect New Horizons’ mission or change the significance of its findings. Pluto still holds the answers to many questions we have about our planet.

What Could We Learn About Earth from Pluto?

Pluto and its Kuiper Belt companions are relics from the formation of our Solar System. They are a pristine conglomeration of materials that orbited our newly formed Sun. This material could have been bombarded by ejecta from a nearby supernova explosion, enriching it and our planet with heavier elements. The chemical composition of these bodies could include organic material that was used to seed our planet with life. There is a lot to learn about the formation of our home from these icy worlds.
One of the main goals of New Horizons is to study Pluto’s atmosphere. The atmosphere of the recently formed Earth was full of hydrogen that rapidly dissipated into space. The removal of hydrogen from the Earth’s atmosphere may have played a role in making it hospitable for life. This process is currently happening on Pluto allowing us to study this process in real-time and note its effects on the surface.
Organic molecules have also been detected on Pluto and are thought to be present on all KBOs. This could indicate that organic compounds were present at the very beginning of our Solar System’s formation. Where these compounds are located and how much is present in the Pluto-Charon system could reveal if KBOs carried the seeds for life as they were forced towards the inner planets.

Recent New Horizons Results

True color image of Pluto taken by New Horizons. Image Credit: NASA/JHUAPL/SwRI

True color image of Pluto taken by New Horizons.
Image Credit: NASA/JHUAPL/SwRI

The first ever images of Pluto’s surface revealed that it is comprised of both regions unaltered since the formation of the Solar System and those that have been created in the last 10 million years. The range of surface age indicates that Pluto is geologically active, like Earth. So far, glaciers and possible active ice volcanoes have been discovered on Pluto. The beautiful heart shaped region was partially shaped by flowing nitrogen, carbon monoxide and methane-rich ice, just as glaciers shaped parts of North America here on Earth.
Images of Pluto revealed a surprising reddish colored surface attributed to the presence of complex hydrocarbon compounds (mixtures of hydrogen and carbon). As New Horizons sped past Pluto, it turned around to capture a backlit image allowing scientists to see in detail, for the first time, the atmosphere. Methane, present in Pluto’s atmosphere, is exposed to UV radiation that breaks down the molecule. This allows the formation of more complex hydrocarbons, which are heavier and fall down to the surface, creating the swaths of red seen in these images. Similar processes could have occurred on a recently formed Earth, creating a chemical mixture of life that rained down onto our planet.
Some insight into the formation of Pluto and other KBOs has been gleaned from this new information. There is a surprising lack of small (<1 mile wide) craters on Pluto and Charon, suggesting that the bodies that formed KBOs were much larger than expected. The widely accepted theories have KBOs forming from much smaller objects to create larger ones. This new information has now shifted the focus to those models that used objects approximately 10 miles wide to create the KBOs we see today. This has scientists excited for New Horizon’s next target.

The Future of New Horizons

Hubble Space Telescope image of MU69. Image Credit: NASA, ESA, SwRI, JHU/APL, and the New Horizons KBO Search Team

Hubble Space Telescope image of MU69.
Image Credit: NASA, ESA, SwRI, JHU/APL, and the New Horizons KBO Search Team

New Horizons has been placed on a trajectory to fly by the 30 mile wide KBO MU69 in January of 2019. MU69 is located in the central regions of the main part of the Kuiper Belt and is considered to be an ancient object due to its relatively circular orbit. Unlike Pluto, which was probably ejected into its current inclined orbit by the gas giants, MU69 most likely spent its entire life in the Kuiper Belt. MU69’s surface is expected to hold an untouched story of the very beginnings of our Solar System. Scientists are also excited by the possibility to study a potential building block of larger KBOs such as Pluto.
New Horizons is still transmitting data back to Earth and will be for many years to come. At the time of its closest approach to Pluto, it took 4 hours and 25 minutes for information to travel from the probe to Earth. As New Horizons speeds towards its next target, that time will increase. By the time it reaches MU69, which is over a billion miles from Pluto, it will take 6 hours to receive information from the probe.
Scientists are actively analyzing information as it streams in from New Horizons. Who knows what seemingly mundane piece of information will lead to a direct application to a process here on Earth? Just as processes on Venus and Mars opened our eyes to the effects of human activity in our atmosphere, processes on Pluto and MU69 could lead to insights into our planet that benefit our species once again.
To learn more about the New Horizons mission and Pluto, visit NASA’s website.

Peer edited by Christine Lee & Kelsey Noll

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The Pillars of Creation and Destruction

We like to think of the Universe as static. Our time is very short compared to the age of the Universe. But there are processes in space that happen on the time scales we inhabit. The variation in brightness of certain types of stars allow astronomers to measure the distances from the Earth to the galaxies where they reside. By taking images at different times over the course of a few years, the trajectories of stars orbiting the supermassive black hole at the center of our galaxy can be followed. And, using instruments like Hubble Space Telescope, we can see the destruction of large structures such as the Pillars of Creation.

Image courtesy of the National Science Foundation's 0.9-meter telescope on Kitt Peak using the NOAO Mosaic CCD camera.

Image courtesy of the National Science Foundation’s 0.9-meter telescope on Kitt Peak using the NOAO Mosaic CCD camera.

The Pillars of Creation are a small part of the Eagle Nebula (pictured above), a huge expanse of gas (mostly hydrogen) and dust where stars are created. The entire structure is estimated to be 5 million years old. The Nebula is 38 quadrillion miles from Earth in the constellation Serpens and is approximately 400 trillion miles at its widest point. The Eagle Nebula is so far away that when viewed from Earth, it would barely span the thickest part of the crescent Moon on the sky. In Hubble Telescope image shown below, we are zoomed in on a small part of the Eagle Nebula, highlighted in a yellow box in top most image. At 23 trillion miles in length, the leftmost pillar would stretch from the Sun to our closest stellar neighbor, Alpha Centauri.

The Pillars get their shape from a group of young, hot stars that were recently created. We can imagine that at one time the Eagle Nebula was a vast expanse of gas and dust with some regions having higher density than others. Gravity works quickly in these situations and the denser portions of the nebula begin to condense further, pulling in more of the surrounding material. Eventually, the densely packed gas ignites and a star is born. These newly formed stars blast away at the remaining gas, heating up and dissipating everything in their path.

Hubble Space Telescope image of the Pillars of Creation taken in 2014.

Hubble Space Telescope image of the Pillars of Creation taken in 2014.

The Hubble images are a bit deceiving, although the pillars appear to be straight up and down, they are actually angled towards the young, hot stars that are illuminating their structure. As viewed from Earth the leftmost pillar is behind the young stars and angled towards them, causing it to appear brighter than the rest of the structure. The remaining pillars are in front of the young stars and angled towards them and appear darker. At the top of each pillar resides a thicker, denser pocket of gas which shields the remaining gas from the intense stellar radiation. This is why the gas formed ‘pillars’ instead of completely dissipating.

1995 and more recent Hubble images for comparison.

1995 and more recent Hubble images for comparison.

In 1995, five years after its launch, Hubble snapped the first highly detailed image of the Pillars. Twenty years later, for Hubble’s 25th anniversary, an even more detailed picture has been released by NASA. After just 19 years, there are visible differences between the two images, revealing how quickly the gas is being blown away. According to some astronomers, the Pillars should last another 3 million years, possibly dissipating into space before the group of young, hot stars run out of fuel and explode as supernovae. There are a few astronomers that believe the Pillars have already been eradicated by a supernova explosion, the light of which has yet to reach us. Whether or not they still exist, the Pillars of Creation are being destroyed right before our very eyes, but they will not passively disappear into space. Instead, they will live on through the stars they are creating within their dense insides, leaving behind a beacon to their once impressive existence.


Peer edited by Chelsea Boyd & Christina Lee

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This article was co-published on the TIBBS Bioscience Blog and on Jo’s blog AstroPunkin.

The Trouble with Reproducibility in Science

As scientists, many of us have read a paper, been inspired by the glamorous data, carefully followed the methods section in order to replicate the results in our own hands, and failed to validate the original results. I’ve often attributed these issues to my own inexperience and naiveté as a young scientist, but over the past several years, the irreproducibility of published data has become a widespread problem. This lack of reproducibility could be perceived as a manifestation of poor experimental design and faulty interpretation of results by researchers. However, this seems counterintuitive in that so much of a scientist’s reputation rests upon the quality of his or her publication record.

Just how rampant is the reproducibility problem?

A 2012 study led by C. Glenn Begley (then the head of cancer research at Amgen, Inc.) probed the boundaries of reproducibility in cancer literature by investigating 53 landmark publications from reputable labs and high impact journals. Despite closely following the methods sections of those publications, and even consulting with the authors and sharing reagents, Begley et al. found that the data in 47 of the 53 publications could not be reproduced; only 6 held up under scrutiny. A similar study performed at Bayer Healthcare in Germany replicated only 25% of the publications examined. These reproducibility issues do not only plague the clinical sciences. The field of psychology recently came under scrutiny during an effort called the ‘Reproducibility Project: Psychology.’ Of 100 published studies, only 39 could be reproduced by independent researchers. These facts are at once shocking, depressing, and infuriating, especially when considering preclinical publications that spawn countless secondary publications, which may lead to expensive and faulty clinical trials that inevitably fail. Unfortunately, the increasing number of flawed publications has led to a precipitous decline in the public’s trust in science and medicine.

What’s causing all of these issues?

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