Spooky Space

Below is a collection of Halloween themed space objects… Enjoy!

The Witches Nebula: Shaped strangely like the head of a witch, this reflection nebula shines brightly in blue because it's reflecting starlight from the large B star Rigel in the constellation Orion.

 

Ghost of the Cepheus Flare: This collection of dust in space is starting to trigger young star formation

Little Ghost Nebula: This strange looking object is a planetary nebula, the result of a star like our sun reaching the end of its life and shedding its outer layers of material.

 

Ghost Head nebula: This star forming region is located in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way.

The Northern Lights

If you live within 20 degrees latitude of Earth's magnetic north pole, seeing the northern lights (or aurora) is a common occurrence. For those of us that live in Rochester, NY, a glimpse of the aurora was a treat this past Monday night. So what are the northern lights and how do they occur? Well, the aurora on Monday was the result of a coronal mass ejection (CME) hitting Earth's magnetic field. A CME is a large outburst of charged particles that is suddenly released from the sun. A quick search for CME on YouTube will get you lots of nice videos. When the CME hit Earth's magnetic field, the particles were directed to the north and south magnetic poles, essentially "grounding" this stream of charged particles. The colorful lights in the sky occur due to an interaction of the electrons and energy in the CME and the oxygen and nitrogen in the atmosphere.

 Chemical elements can be in one of many states. In the ground state, they have the required number of electrons orbiting their nucleus and are stable and happy. Elements can also be in an excited state where the electrons are all there, but they sit in what chemists call higher energy levels. Basically the atom gained some energy and the electrons are holding onto that energy, making the atom slightly less stable. Another thing that can happen is that an atom gains so much extra energy that an electron gets "kicked out" and lost completely from the atom. This is called ionization. When a CME full of energy and electrons hits Earth, it can bump atoms into higher energy states, ionize atoms, and also give back electrons to ionized atoms making them more stable. When an atom goes from being excited back to the ground state, or when it regains an electron, it releases excess energy in the form of light. Different elements release different amounts of energy due to their physical properties, and therefore emit different colors of light. Oxygen often emits green light, while nitrogen emits blue or red light, depending on whether it's regaining an electron or falling to the ground state. This emission of light by the elements in our atmosphere due to interactions with particles in the CME is what causes the northern lights! Below are some images taken by members of the Rochester Academy of Sciences Astronomy Chapter of the aurora visible from upstate NY.

Images courtesy of: Dave Bradley (left) and Larry Arbeiter (right)

 

Images courtesy of: Kevin Zwiebel (top) and Nick Lamendola (bottom)

The Kelvin Temperature Scale

 

Here in the United States, we measure temperature in Fahrenheit. Most of the rest of the world uses the metric system and measures temperature in Celsius. In the mid 1800's, scientists came up with a new system  to measure temperature called the Kelvin scale. The Kelvin scale ranges from absolute zero (the point at which all movement inside atoms ceases) to infinity. This type of "absolute" temperature scale is more scientifically accurate than Fahrenheit or Celsius as "0" is the coldest an object could ever theoretically get. This scale is easier to understand conceptually, and works nicely when doing calculations. We can relate the three scales by noting that the freezing point of water (0 C, 32 F) is equivalent to ~273 Kelvin (K), and "room temperature" is about 300K. The Kelvin scale is handy for astronomy as it helps put the temperature of astronomical objects into perspective. The cosmic microwave background (which is what "fills" what we perceive as outer space) is about 2.7K. The surface of the sun is ~6000K, and the sun's corona is about 2,000,000K! When put into perspective, humans are only accustomed to living in a temperature range that spans ~40K, whereas the universe has objects whose temperatures range from practically zero to billions of Kelvin!

Observations of a Disturbed Circumstellar Disk

Planets are thought to form in the circumstellar disks around young stars. Astronomers have simulated this with computer model, and have been able to replicate (to a pretty good extent) the formation of our solar system via the circumstellar disk around our sun when it was very young. Planet formation is evident around nearby young stars as well. The caveat is that we can not directly see the planet forming inside the disk. Instead, astronomers use infrared and radio data to infer the a gap in the disk, probably due to the formation of a planet. Recently, astronomers were able to catch a rare glimpse or what appear to be a circumstellar disk around a star that's been distorted due to the presence of a planet.

 

Now we can't see the planet directly, but the fact that the disk has a spiral shape and not a circular shape suggests that a planet has been gravitationally disturbing the disk material. The image was taken with the Subaru telescope, an optical and infrared 8.2m scope in Mauna Kea, HI. The light from the star has been intentionally blocked out in the image, so that we can see the disk glowing in infrared. The disk is bright in the infrared because it is colder than the star it surrounds. How are we able to see such a disk? It's a combination of the fact that the telescope is very large, it uses very high tech adaptive optics to remove atmospheric affects, and the star is relatively close to us (~450 ly away). Astronomers are not certain that these arms are due to planets, but modeling shows that planets do have the capability of causing such structure. More modeling observations will need to be done to confirm these ideas.

Image credit: NASA's Goddard Space Flight Center/NCSA

Living in the Local Bubble

3D view of the local bubble (white) and pieces of adjacent parts of the interstellar medium (purple and blue)

Did you know that we live inside a bubble? Believe it or not, the solar system, along with many other stars, sits inside what astronomers call the Local Bubble. It's a region of space that is less dense than the surrounding area of space, and contain very hot gas ( greater than 1,000,000 degrees!) that emit soft x-rays. Inside the bubble, space has about 0.01 hydrogen atoms per cubic inch (compare this to the ~10^20 atoms per cubic inch here on earth!). The bubble is shaped like an egg or a cylinder that is about 10x as tall as it is wide (30x200 parsecs), and sits upright with the plane of our galaxy crossing through the bottom third of the bubble. The solar system itself sits inside a thin sheet of cloud called the Local Fluff (no joke!), that is slightly more dense than the surrounding bubble. So where did this bubble come from? Astronomers are not a hundred percent sure, but the leading theory says that a supernova must have went off somewhere near the sun and essentially "blew" the bubble and heated up the gas inside. This probably happened around 10 million years ago, way after the sun and planets had already formed! So in a sense we survived a supernova explosion! Now the big question is this: are we living inside a supernova remnant that is still actively heating and removing material from the area? Or has the remnant material disappeared and left behind an "empty" bubble. Astronomers are actively trying to answer this question. But for now we are living happily in a sheet of fluff inside our own little galactic bubble!

Birthday Star

Today is my Birthday! So I thought I would write a birthday themed ADYK. I came across this cute website that finds your birthday star. The link is here. Now I didn't check it's scientific accuracy, but regardless it's a neat application. All you have to do is tell the program your birthday (month, day and year), and it will give you the name, coordinates and some information about a star whose distance in light years is close to your current age. Remember a light year is the distance light can travel in one year. So if a star is ten light years away, the light that you see tonight is actually ten years old. It's the light that star emitted 10 years ago, and it took that long to reach us here on Earth. So what's special about this birthday star? Well if the star is as far away in light years as your current age, then the light you are seeing from that star today was emitted on the exact day you were born! It's almost like looking back in time at what the universe looked like on the day of your birth. Below is my birthday star for today. Try it out, it's pretty cool!

Solar Neutrino Problem

Not understanding the actions of neutrinos seems to be a common theme for scientists. As discussed in last weeks ADYK, claims that neutrinos travel faster than the speed of light are currently stumping scientific theory, but neutrinos have always been mysterious particles...  

 

We discussed last week that neutrinos are neutral subatomic particles that are created in large quantities inside the sun. Astronomers in the 1940's hypothesized this, and decided to build detectors on Earth that would measure the amount of incoming solar neutrinos here on Earth. Based on the then current theories of solar fusion, astronomers predicted how many neutrinos they would expect to see in their detectors. Long story short, they measured only one third of the expected number of neutrinos, and the solar neutrino problem was born. Astronomers spent the next 50+ years trying to figure out where their theories went wrong. It was originally thought that neutrinos were massless particles, like light, and therefore existed in one form only. This turned out to be the problem, as was hypothesized by particle physicists in the 1960's and 1970's. If neutrinos had a tiny bit of mass, then quantum theory says that they have the ability to switch between three different "flavors" of neutrinos (electron, muon, tau), each with slightly different properties. If this were true, electron neutrinos would be created and released by the sun, then on their travels towards Earth, probability suggests that 33% would switch to tau neutrinos, and 33% would switch to the muon neutrinos. The detectors in the 1940's were only sensitive to electron neutrinos, and thus never detected the other two types (aka the other 66% of the missing neutrinos!). This sounded like a fantastic solution, but astronomers and physicist had to wait until the years 1962 and 2000 for the first detection of the muon and tau neutrino, respectively, thus confirming the theory. It was a long wait, but proving that neutrinos come in three flavors allowed scientists to refine the standard model of particle physics, and astronomers to really understand what was happening in the interior of stars.