All posts by Alisa Vinzant

Stellar Evolution Part 3: Supergiant and Supernova

Most stars on the main sequence are relatively average: not too big and not too small. But every so often, a star begins its life as an absolute monster: a supergiant.

Supergiant

These supergiants do join the main sequence, but due to the sheer amount of gravitational force and pressure, they burn through the hydrogen in their cores in a fraction of the time that smaller stars do. They quickly leave the main sequence and expand in size to become thousands of times larger than the sun. Like smaller stars, these supergiants begin helium fusion in their cores and begin hydrogen fusion in shells around the core. But unlike smaller stars, which stop their fusion at this point, supergiants form several layers throughout the star of differently fusing gases, giving it an onion-type look.

Supergiant stellar evolution

Fusion in the core will eventually reach iron. At this point, nuclear fusion no longer produces energy, and so it stops. Without outward radiation pressure, the intense gravity causes the star to collapse. Protons and electrons get forced together in the core, turning it into a rigid sphere of neutrons. As the outer layers reach the limits of the neutron core, they rebound off and get propelled outward with huge amounts of energy. These shockwaves tear the star apart in a supernova.

Supergiant stellar

Credit: NASA, ESA, and G. Bacon (STScI) 

All that remains is the rigid sphere of neutrons, known as a neutron star. However, some supergiants are so massive that even the neutron star continues to collapse, creating an object so dense that it creates a singularity, also known as a black hole. Supergiants are rare in our universe, but their existence is crucial. Supernovas are so energetic that they create all of the elements heavier than iron, and many star systems, including our own, are made from the remnants of these explosions. Without them, life itself wouldn’t exist.

Written By: Scott Yarbrough

Additional Resource: Mouser

Stellar Evolution Part 2: Main Sequence Stars

When a protostar’s core reaches 15,000,000 degrees Celsius, nuclear fusion begins in its core. This ignition marks the star’s birth as it becomes a main sequence star.

Stars part 2

Main sequence stars have a ton of variety. They range from cooler red stars to hotly burning blue ones, and their size can range from a fraction of our sun’s mass up to several hundred times as large. The only thing that matters for the main sequence is the presence of hydrogen fusion in the core. Hydrogen fusion takes hydrogen ions and turns them into helium, creating massive amounts of energy in the process. The outwards radiation pressure resists the force of gravity, preventing the star from collapsing any further.

Stars Hydrogen Fusion

But once the core runs out of hydrogen, the star starts to contract again briefly, until a shell of hydrogen around the core becomes hot enough to fuse into helium. When this happens, the radiation pushes the outer layers of the star far out into space, turning the star into a red giant. The core continues to collapse, however, continuing to heat up until it reaches 200,000,000 degrees Celsius. At this point, the helium that now makes up the core begins to fuse into carbon. Eventually, the helium will also run out. When this happens, the outer layers of the star continues to expand and cool down until finally all that is left is a planetary nebula with the remnant of the core at the center. We call this remnant a white dwarf.

Stars Planetary Nebula

You may be surprised to not hear the word “supernova” being thrown around. This is because supernovae only occur in incredibly large stars. For most of the main sequence stars, their deaths will be relatively calm and quiet, going out not with a bang, but with a sigh.

Written By: Scott Yarbrough

 

Stellar Evolution Part 1: Nebulae and Protostars

In the vast emptiness of space, there are floating clouds of gas and dust called nebulae. These clouds are stellar nurseries, filled with material that will one day become multiple solar systems. stellar evolution When part of a nebula is slightly more densely packed than the rest, gravity is stronger in that region. It begins to pull the surrounding gas inwards. This increases gravity, which pulls even more stuff in. As this happens, the gas molecules rub against one another, heating up due to friction. When the gas heats up, it begins to give off light, illuminating the nebula with brilliant colors. Eventually, this region of the cloud takes on a rough spherical shape. The gas begins to ionize, separating electrons from their nuclei as the sphere heats up even further as it continues to collapse due to the massive gravitational forces at play. This spherical shape is known as a protostar! Stellar Evolution Stars This protostar will continue to collapse and heat up, eventually becoming a main-sequence star. For that to happen, nuclear fusion must begin in the core. When it starts, outwards radiation pressure is so strong that it prevents gravity from causing the star to collapse any further. We’ll talk about the life — and death — of main-sequence star in a future blog post, so keep your eyes open! Written By: Scott Yarbrough

Making Nitrogen Balloons Float

When you blow up a balloon with your breath, you’re filling it with a mixture of nitrogen, oxygen, and a little bit of carbon dioxide. And when you let go of it, it falls down to the floor. Why does it do this? And how could we prevent it from doing so?

Nitrogen Falling Balloon

Think of it like rocks in water. If you throw a stone into a river, it will sink to the bottom. This is because the rock is more dense than the water around it, due to its higher mass that’s concentrated in a smaller volume. The water tries to push back against the rock with a buoyant force, but the force of gravity is stronger, so the rock sinks. In our example, the balloon filled with nitrogen, oxygen, and carbon dioxide is the rock, and the atmosphere around us (made up of nitrogen and oxygen) is the water. Even though the gases inside and outside the balloon are approximately the same, the balloon material adds to the weight, causing it to sink down. If we wanted to get the balloon to float, we would have to either decrease its density or increase the density of the air around it. By putting a low-density gas like helium or hydrogen inside the balloon, we can make it light enough to float.

Nitrogen Helium

But the cooler thing to do is to change the density of the air around the balloon! We can do that here at AstroCamp by allowing dry ice to heat up and change into its gaseous form: carbon dioxide. The higher density of carbon dioxide makes it so that the buoyant force is way stronger on the balloon, which causes it to float!

Nitrogen CO2 Floating

Density experiments are really cool. You can actually learn a lot about them if you try it at home! Try mixing cooking oil and water with each other, then put object like rocks or pieces of wood inside! See what happens and let us know in the comments below!

Written By: Scott Yarbrough

Lights and Lasers: How the Glow Wall Glows

One of the most popular classes at AstroCamp is Lights and Lasers, where students learn about the different energies and properties of light. The Lights and Lasers room is easily recognizable because of its Glow-in-the-Dark Walls. Once you turn the lights off, these awesome walls glow a vibrant green, slowly dimming until you shine light on them again.

Lights and Lasers Glow Wall

These walls have a physical property known as phosphorescence. It is a type of photoluminescence: an emission of light occurring when an object absorbs and releases photons. Other common types include bioluminescence — a chemical reaction in living organisms that give off light — and electroluminescence — the process by which LEDs give off light.

Lights and Lasers

Phosphorescence works by absorbing photons into the object’s electrons. This bumps those electrons into a higher energy level. But the electrons cannot then easily reemit the photons to return to their ground state: the electron becomes “trapped” and it requires a “forbidden transition” to return to its lower energy.

Lights and Lasers Transition

However, due to quantum mechanics, this forbidden transition can still happen, but it does so at a fairly slow rate. This allows the material to “store” the light and let it out slowly, sometimes taking hours to let out all of its light! This same material that we use for our glow wall is what is used for things like glow in the dark stickers! So even though they seem simple, next time you see them you’ll know that there’s a lot more going on than what first appears!

Written By: Scott Yarbrough

Black Holes Explained (Sort of)

Black holes are a confusing topic in astronomy. You’ve heard about them starting from a young age, but whenever you ask someone for more information about them, there’s a whole lot of “I dunno”s. The truth is, black holes have been romanticized by science fiction, when in fact they are nothing more than an oddity of physics (albeit still pretty cool). Once you understand a few basic rules of physics, learning about black holes is easy.

Black Holes

 

Step 1: Gravity

The first step on the road to understanding black holes is understanding how gravity works. An object with mass will cause a bend in spacetime, affecting other objects around itself. This effect is what causes gravity. The more mass something has, the more gravity it produces. The force of gravity gets weaker the farther you get from the center of mass proportional to the inverse of its distance squared. Yeah, I know, that sounds confusing. Maybe it’s easier if you see the equation for calculating the force of gravity.

 

Black Hole Formula

In this equation, M is the mass of the larger object, m is the mass of the smaller object, G is the universal gravitational constant, and r is the distance between the two objects. If you double the distance between two objects, then the force of gravity is ¼ what it was before. If you triple it, then the force of gravity is only ⅑ the original.

Step 2: Escape Velocity

In order to escape the gravitational field of a massive object, you need to attain a specific speed, called its escape velocity. It’s calculated using the force of gravity, taking into account the mass of the large object and how far away you are. Once something is going at minimum the escape velocity, then it is no longer captured by the massive object.

Step 3: Singularity (or, infinite density)

Black holes (NASA)

Density is an easy calculation, as seen below.

Black Holes Singularity Formula

Where m is mass and V is volume. As mass increases or as volume decreases, density goes up. In a black hole, the volume is essentially 0, which causes the density to approach infinity. This creates what is called a singularity.

Putting it all Together

When the most massive stars in the universe go supernova, the force of the explosion causes the core of the star to get smaller and smaller, essentially packing it all into a volume of 0. This point of infinite density creates such a huge bend in spacetime that it creates a singularity. At a certain distance away from this singularity, the force of gravity the escape velocity reaches the speed of light.

As defined by the theory of relativity, nothing in the universe can go faster than the speed of light. So if the escape velocity of this object at a certain distance is higher than that, then not even light can escape the singularity. With no light escaping, the object and the space around it gives off no light.

This is the black hole.

There’s a lot more that goes into defining black holes, such as its mass, spin, etc., but that’s just icing on the cake. There you have it. There’s so much more to learn about black holes, but knowing even this much gives you the tools you need to understand them at a fundamental level.

Written By: Scott Yarbrough

3D Printing an Asteroid

NASA has always been about accomplishing crazy. In the 1960s, the idea of people walking around on the moon was ludicrous, but NASA got them there anyways. Now, NASA is performing another crazy feat: sending a probe to an asteroid, collecting rock samples, and returning that probe to Earth. Additionally, the probe has created a digital map of the asteroid which we can recreate, simply by using a 3D printer.

OSIRISREx - 3D Printing Asteroid

In September 2016, the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer space probe (OSIRIS-REx for short) was launched aboard an Atlas V rocket. It quickly made its way into space and began its journey towards the asteroid designated 101955 Bennu. This journey lasted over two years as the robe used low-power thrusters and gravity assists from Earth to reach its destination.

Side by Side - 3D Printing Asteroid

Side by Side – 3D Printing Asteroid

OSIRIS-REx reached Bennu in December of 2018, and as it approached, it used its long-range PolyCam sensors to map out the surface of the asteroid. After arriving, OSIRIS-REx used its short-range cameras to take even higher resolution images of Bennu’s surface. NASA scientists used that data to create 3D models and released them to the public!

Rotation - 3D Printing Asteroid

Since we’re lucky enough to have a number of 3D printers here at camp, we decided to print our very own Bennu asteroid! You can see the results below, but if you want to have your own version of the asteroid, you can find the files at https://www.asteroidmission.org/updated-bennu-shape-model-3d-files/

Written By: Scott Yarbrough

Busting the Misconception Between Gravity and Atmospheric Pressure

A common misconception we see at AstroCamp is how gravity and atmospheric pressure work. It makes sense! The two seem interchangeable at a glance, however they both get weaker as altitude increases, and there can’t even be an atmosphere without gravity. Despite their similarities, the two are very different.

Gravity is a property of anything with mass. It’s one of the four fundamental forces in the universe, and it’s caused by an object bending spacetime around itself. The larger the object, the greater a force it will exert.

Pressure isn’t even a force (technically). It’s a measurement of how much force is being applied per unit area. A lot of force can be spread out over a large surface area so that the pressure is overall small, and a small force can be focused onto a small enough point to cause a high pressure.

When talking about atmospheric pressure, we’re talking about the average force per unit area the gas molecules are exerting on objects in the air. The air molecules are zooming everywhere and bouncing into everything. Every time they impact, they push with a tiny force.

Atmospheric pressure changes with 1) the rate of collisions and 2) the force of impact. More molecules mean more collisions, which leads to a higher air pressure. Similarly, heavier gases or gases moving at higher speeds will cause a higher impact force, also increasing the atmospheric pressure.

Air at sea level is being compressed by all of the air above it, weighing it down and increasing its density. When you increase altitude, the less air you have above you, so pressure goes down. This is why atmospheric pressure gets weaker the higher in altitude you go.

After learning how they both work, it’s easy to see why the effects of gravity and atmospheric pressure can get confused. But their differences are also prevalent enough that you should be able distinguish between the two!

Written By: Scott Yarbrough

Homopolar Motorcar

A homopolar motor is a device that relies on flowing electricity, magnetic fields, and the interaction between the two. It consists of a voltage source, neodymium magnets, and a conductor that allows electricity to flow. And it’s super easy to make yourself!

What you’ll need:

  • 1 AA battery
  • 2 neodymium magnets
  • Thick copper wire

 

————

Step 1

Place one of your magnets onto the positive terminal of the battery.

Holompolar Motorcar Step 1

Step 2

Use the already attached magnet to test the poles of the second magnet. Figure out which sides are repelling each other, and place the second magnet so that the repelling side faces away from the battery. This way, either both South poles or both North poles are facing outwards! (Note: it doesn’t matter which, as long as they’re consistent with each other!)

Holompolar Motorcar Step 2

Step 3

Shape your copper wire so that it can hook easily on the inside of the magnets. Try to maximize the amount of contact it has with the magnets on BOTH sides, so as much electricity as possible can flow. When it’s been properly shaped, hook the wire onto the motor!

Holompolar Motorcar Step 3

Instead of using a wire, you could use a sheet of aluminum foil! Lay it as flat as you can on a level surface, away from any metals that might attract your magnets. Make sure there are no tears or holes in the aluminum. Then place your battery-magnet motor on top! The aluminum will allow electricity to flow!

————

When a magnetic field is applied to an object carrying electricity, it applies a force to that object. This is called the Lorentz Force. Due to the electricity flowing through the magnets, this force becomes a torque, causing the motor to rotate and drive forward!

Homopolar Motorcar Rollin

Written By: Scott Yarbrough

For Mimi by Twin Musicom is licensed under a Creative Commons Attribution license (https://creativecommons.org/licenses/by/4.0/)

Artist: http://www.twinmusicom.org/

What is Escape Velocity?

Escape Velocity is probably something you’ve heard on a TV show, or maybe you learned about it from NASA talking about their newest spacecraft. It is a commonly discussed term, but it isn’t the easiest thing to understand. Imagine you’re in a strange universe where only the Earth exists. The only gravity comes from its center, and it extends infinitely far away, getting weaker and weaker the further away you get. In order to get to that infinite point before you get pulled back by the Earth’s gravity, you need to be going at least 11.2 km/s (25,000 mph). This speed is the escape velocity!

escape velocity 1
This value depends on both the distance from the gravitational center of the object you’re escaping from and the mass of the object. The closer you are to a heavier object, the faster you need to go to reach escape velocity. For example, escape velocity from the Earth at a distance of the moon’s orbit is only 1.3 km/s (3,000 mph), but to escape from the sun’s gravity at the distance of the Earth is a whopping 44.7 km/s (100,000 mph)!

escape velocity moon

But since there’s no such thing as a universe where only the Earth exists, we have to worry about the gravity of other celestial objects! Once you escape from the Earth’s gravity, you’ll then be captured by the sun. If you escape that, then you’ll be captured by the Milky Way’s gravity! So the hypothetical infinite point is just that: hypothetical! No matter what, there’s always going to be something pulling on you with gravity.

Written By: Scott Yarbrough

WELCOME TO OUR ASTROCAMP BLOG

We would like to thank you for visiting our blog. AstroCamp is a hands-on physical science program with an emphasis on astronomy and space exploration. Our classes and activities are designed to inspire students toward future success in their academic and personal pursuits. This blog is intended to provide you with up-to-date news and information about our camp programs, as well as current science and astronomical happenings. This blog has been created by our staff who have at least a Bachelors Degree in Physics or Astronomy, however it is not uncommon for them to have a Masters Degree or PhD. We encourage you to also follow us on Facebook, Instagram, Google+, Twitter, and Vine to see even more of our interesting science, space and astronomy information. Feel free to leave comments, questions, or share our blog with others. Please visit www.astrocampschool.org for additional information. Happy Reading!

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