Spiral and Elliptical Galaxies

 

Spiral Galaxy M81

 

Elliptical Galaxy M87

Galaxies come in two different types: Spirals and Ellipticals. When most people think of a galaxy, they think of the classic spiral galaxy with a twisted arm shape (like M81 pictured above). These bright spiral arms contain most of the stars in the galaxies, which is why they are so bright. The number of spiral arms, how compact they are, and the direction they face varies between galaxies. Most spiral galaxies have a central black hole where all the spiral arms meet. Elliptical galaxies (like M87 pictured above) don't really look like a galaxy at all. They are essentially a huge collection of stars, often in an oval shape, and look like a bright fuzzy cloud, or out of focus star. These galaxies have little structure, other than the density of stars increases towards the center, where a black hole often lives. The next ADYK will discuss Edwin Hubble's galaxy classification scheme, a way of categorizing these types of galaxies based on there shape and structure.

The Christmas Tree Cluster

 

 Visible image of the Christmas Tree Cluster

I hope everyone is enjoying the holiday season! To keep with the spirit, today I present the Christmas Tree Cluster! The Christmas Tree cluster is another name for the young star forming region NGC 2264. It's main feature, the cone nebula, has a tree like shape with a bright star on top, mimicking a Christmas tree.  The triangle shaped object is a cloud of gas and dust in which stars are currently forming. The bright star above it has recently formed and has just begun to burn hydrogen in its core. This star appears so bright because it is a B-type star (very bright and hot) which is 10 times the size of our sun! Merry Christmas!

Image Credit: ESO

Active Galactic Nuclei

Active Galactic Nuclei…. You may not know what they are, but you have to admit that they sound pretty crazy!  Many galaxies have bright centers due to stars bunched up around a super massive black hole. Active galactic nuclei (AGN) are the super bright cores of distant galaxies. AGN have supermassive black holes that are actively accreting a lot of matter. This in fall of matter creates heat, turns the region around the black hole into plasma, and emits copious amounts of light. The image above is what the active nucleus of NGC 5141 looks like in X-rays! The bright yellow center means lots of x-rays are being emitted, and therefore this region must be very hot and active. AGN are so bright that we can see ones (with good telescopes) that are as far as 12 billion light years away! When we look at AGN, we are most likely seeing light from very large and compact galaxies that existed in the beginning of the universe. There are three main types of AGN: Syefert, Blazars and Quasars. The differences lie in the type of radiation emitted.  Astronomers think that there may only be one "type" of AGN, and they look different because we are viewing them at different angles. Seyferts, Blazars and Quasars will be discussed more in future ADYK.

Image credit: Radomski, J. et al.  2003, AJ 587, 117

Kepler's First Earth Size Planets!

The Kepler space telescope has identified over 1200 potential exoplanets after only 1 year of operation. Kepler searches for exoplanets vi the transit method, i.e. watching for small dimming of stars as planets cross in front of them. Recently, members of the Kepler team confirmed the existence of a multi-planet system that contains two roughly Earth sized planets! 

Kepler 20 has 5 five, and maybe more, planets orbiting it. Kepler 20-b,c and d are 2-3 times the size of Earth, while Kepler 20-e and f are 0.87 and 1.02 times the size of Earth! All of these planets sit within 0.4 AU of the host star, closer than Mercury sits to our sun. The image above shows the five planets and their position in relation to Mercury's orbit. The sizes are roughly to scale as well. It's unlikely that these planets host life because of their close proximity to the sun. NASA just released the data to the astronomy community today, so I'll keep you updated on any future discoveries about this system!

Image Credit: David A. Aguilar (CfA) 

Comet Lovejoy

Named after the amateur astronomer who made the discovery, comet Lovejoy has been making headline news lately. The comet belongs to the Kreutz family of comets, and is most likely a small piece of the Great Comet of 1106 which broke apart in our solar system way back in the 12th century. Comet Lovejoy is on a very eccentric or oval shaped orbit which brings it very close to the sun. It's closest approach to the sun occurred a few days ago, passing only 120,000km (75,000 miles) above the sun's surface, which is extremely close!  Astronomers expected comet Lovejoy to burn up in the sun's atmosphere, but to their surprise Lovejoy survived! The comet's path was captured by both SOHO and SDO, which are satellites monitoring the sun's activity. Below is a video of a compilation of images taken by both satellites. The blue images show the comet approaching the sun towards the bottom left. The yellow images also show the comet approaching the sun, then exiting the sun's atmosphere. The final set of images have an arrow pointing out the comet, which again enters and exists the sun's atmosphere!  The fact that this comet survived means that it's probably much bigger than astronomers predicted; maybe even as larger as 0.5 miles!

Mercury, a Solar Flare and a Spaceship?!

 There has been lots of talk in the news lately surrounding a video released by NASA's STEREO spacecraft of a solar flare hitting mercury. Here's an image of the event.

 

In the image, you're seeing a solar flare released from the sun smack right into Mercury! It appears in the image that there is some bright object to the right of Mercury that is also being hit by the flare! UFO theorists think that this could be a spaceship, with a protective shield, that is being irradiated by the solar flare! This sure sounds and looks like a good theory, but it's not correct. What you're actually seeing in the video is a "ghost image" of Mercury, not a space ship. Now I'm not an expert on ghost imaging or STEREO data reduction, but here's the basic idea. You take an image of mercury on a "normal" day, and use a model of the planets brightness to subtract away the planet. Unfortunately, your model overestimates, slightly, the brightness of the planet. Now you have an image of a noisy background and an extra dark spot where mercury was. Today, the solar flare hits mercury and you take an image right when it hits. To clean up the image and make both the solar flare and the planet visible, you again subtract mercury (it fits accurately the model this time) and then subtract the "normal" image from today's image. This results in a new image where the planets position is extra bright. In other words, dark spots in the original image are now bright. But remember, you over-subtracted the brightness of mercury in your "normal" image, and the planet has moved a little bit in space between the time that the two images are taken. So what does this mean? Your resulting image will show Mercury's current position very brightly, and a ghost image of the old Mercury nearby. This is exactly what you are seeing in the video above, the ghost image of mercury. Long story short, data processing is very difficult, and these sorts of over-subtractions occur all the time in astronomy. Normally, astronomers further correct the final result and remove any ghost images, but they did not in the image above. Sorry to destroy the hopes of all you Star-Trek fans, but we didn't discover a spaceship.

Kepler 22-B

The newly discovered and confirmed exoplanet Kepler 22-B has made big news lately. Why? Well, it's the first confirmed exoplanet discovered by the Kepler space telescope that is roughly the size of Earth and sits in the habitable zone of it's host star! Now don't get too excited, this doesn't mean we've found Earth's twin, or that aliens exist. Being in the habitable zone doesn't imply that life actually exists there, it just means that the planet is the right distance from the host star such that it could harvest liquid water, if any exists in the system.

 Artists impression of Kepler 22-B

The star, Kepler 22, is very similar to our sun in size and composition. The planet, Kepler 22-B, is about twice as large as Earth, and sits a little bit closer to its host star than Earth does to our sun. Astronomers don't yet know anything about the planets structure or composition. Due to its size and proximity to its host star, it's likely that the planet is rocky, but we need more information to confirm that.  We also need more observations to see if the planet has an atmosphere and ,if it does, what that atmosphere is made of. One thing we must also keep in mind is that this system is 600 light-years away! At the speed of the space shuttle, it would take over 10 million years to get there! So all these news stories that suggest traveling to this planet are quite optimistic to say the least. Regardless, this is an amazing discovery, and astronomers expect to discover more planets like this in the near future. Could Kepler 22-B be very similar to Earth? Is there an alien species there? Only time will tell!

Credit: NASA/Ames/JPL-Caltech

New Horizons Breaks Pluto Approach Record

New Horizon's is the spacecraft that's currently on its way to Pluto. The spacecraft will never land on Pluto, it's just going to fly by and take photographs of both Pluto and its moons. New Horizon's has recently become a "world record" holder; it is now closer to Pluto than any spacecraft has ever been! Voyager 1 used to hold this record. In 1986 it was 982 million miles from Pluto. This may seem like  a large distance, but in astronomical terms, this is actually very close!

  

New Horizon's launched in January of 2006, and has been traveling at a whooping 34,000mph towards the edge of our solar system. The path of new Horizons and it's current position are shown in green above. The predicted path is shown in red. It's closest approach to Pluto (~8,000 miles away) will occur in July 2015. At this time, New Horizons will be close enough to Pluto to resolve objects the size of a football field! New Horizons will give us our first ever close up view of Pluto and its moons!

Image Credit: NASA/JPL/New Horizons Team

'Tis the Season!

If you're in the northern hemisphere, then you are currently experiencing late fall/early winter type weather. But why do we even have seasons? And why is it warmer near the equator in winter than it is at the poles? The answer is because Earth is tilted!

Most astronomical pictures project Earth as an "upright" body, with the north celestial pole at the top and the south celestial pole at the bottom. But actually, Earth is tilted 23.44 degrees from the poles being perpendicular to Earth's orbit. Earth's orbit around the sun is almost a perfect circle, so if the Earth was upright, it would be very hot at the equator, very cold at the poles, and every day and night would have exactly the same length. But since the Earth is tilted, we experience seasons. Let's look at the image above. Currently, the Earth is just about at the far left position on the diagram. This is how the Earth appears during winter for the northern hemisphere, and summer for the southern hemisphere. Because the north is tilted away from the sun, it's receiving less direct sunlight and is therefore colder. The south is currently angled towards to sun and receiving more direct sunlight, so it's warmer. As the Earth orbits the sun counterclockwise, we reach northern spring and southern fall, a point where neither hemisphere is angled more towards the sun. This is what gives us our intermediate seasons. On the far right, it's northern summer and southern winter, for the same reasons discussed previously, only now the north receives more direct sunlight. Temperatures at the equator don't fluctuate much at all, because the angle at which it faces the sun doesn't change much. So if you are currently freezing cold in the snow, or basking in the sunlight, you have Earth's tilt to thank or blame!

Solar Basics

 

Today we are going to cover the basics about our sun! The sun is a star, and it's the only star associated with our solar system. It's about 93million miles away from Earth, and about 110x the size of Earth. The sun is a giant ball of gas, and has a temperature of over 5800 degrees! It's corona, or surrounding gaseous "atmosphere", can get up to 2 million degrees! The suns composition is about 3/4 hydrogen, 1/4 helium, and a tiny fraction is elements heavier than helium. Fusion reactions of hydrogen into helium in the suns core release energy, which is why the sun emits light. All stars have fusion in their cores and therefore emit light. Objects such as moons and planets do not emit their own light, they reflect light from a nearby star. The sun is about 5 billion years old, and will survive for another 5 billion years. At this point, the sun will expand, engulfing the inner planets, and then shed its outer layers and create a planetary nebula. (But don't worry, that's many years away!) The image above is what the sun looks like today! (For more fun facts about the sun, see the post entitled Our Friend, the Sun)

Image credit: SOHO/ESA/NASA

A "Not So Amateur" Image of the Disk Around Beta Pictoris

We've discussed circumstellar disks around young stars multiple times in this blog, but we haven't discussed how they are observed. Circumstellar disks are best visible at infrared and optical wavelengths. This is because the disks are made of dust and gas, which reflect optical starlight and emit thermal infrared light. Astronomers have used telescopes such as Hubble (optical) and Spitzer (infrared) to image  many disks of young stars, but you don't necessarily need a space telescope to see these disks.  An amateur astronomer named Ralf Olsen proved this by imaging the disk around the nearby young star Beta Pictoris! Armed with his backyard 10inch telescope, a PC webcam and no filters, Olsen was able to image the disk of Beta Pictoris by following a procedure outlined in a 1993 paper by Lecavelier Des Etangs and collaborators. Basically, Olsen imaged Beta Pictoris and a very similar star called Alpha Pictoris, then subtracted the Alpha image from the Beta. Since the stars have similar properties, subtracting the images effectively erased the light of Beta Pictoris, making its disk visible. The image below is the final result from Olsen.

 

The black circle is where Beta Pictoris was removed in the image, and its disk is the extended white region near the star that the dotted lines point to. It's really amazing what an amateur astronomer can do with a basic telescope! Olsen is living proof that you don't need to be a rocket scientist to understand, and even contribute research to the field of astronomy!

Image Credit: Rolf Olsen

http://www.pbase.com/rolfolsen/image/139722640/original

The Slingshot Maneuver

Getting spacecrafts from one planet to another is no easy task. Sure it may sound easy, just fire off a rocket aimed towards the planet of your choice and eventually you will get there. There are many problems with this "point and shoot" method. One is that you would need a lot of fuel to rocket yourself  all the way from Earth to another planet, both to get you there and to keep the ship aimed properly. The more rocket fuel you have though, the harder it is to successfully launch yourself away from Earth, and the more money it costs to fly the space craft. The second major problem comes about once you've reached your destination. Assume you've aimed properly and had enough fuel to make it to the planet in question, now how do you slow down so that you can either safely land on the planet's surface, or orbit it in a stable orbit? More fuel, high tech gadgets, and lot of luck are needed to succeed then. So how do astronomers get spacecrafts from one planet to another? They use the sun! Since the sun is such a massive body, it can be used both to slow spacecrafts down, or speed them up. This is called a gravity assist or slingshot maneuver. When we want to get to Venus or mercury for example, we send spacecrafts around the sun multiple times. The gravitational attraction between the two objects slows the spacecraft down so that it can casually approach the planets. When we want to travel to Jupiter, or the outer edges of our solar system, we use the sun as a slingshot! By sending spacecrafts around the sun at the right distance, the pull of the sun can give the craft angular momentum and increases its speed. As the craft rounds the sun it shot out towards to outer solar system. The key here is to approach the sun with the correct speed, distance and angle, so you get the increase or decrease in speed you desire. Below is the path the Cassini-Huygens mission took around the sun before it was shot out towards Saturn. Carefully planned gravity assists via the sun and inner planets are what got Cassini to Saturn successfully.

 Image Credit: NASA

Jupiter's Ice Moon Europa: Part 2

We discussed Europa's icy surface and possible sub-surface ocean last week. Some images that Galileo sent back showed bumpy features on Europa's surface, almost like blisters. These features (shown below)  look similar to places on Earth where glaciers sit on top of undersea volcanoes. Basically, these underwater vents heat the water above them which melts the overlaying ice. Since these volcanoes are not active all the time, there are periods where the water can re-freeze on the surface. This re-freezing does not leave a smooth sheet, but rather a chaotic frozen pattern, much like the pattern seen on Europa. So what does this all mean? It suggests that there is some sort of internal heating mechanism within the moon, and therefore a subsurface ocean! The depth of this ocean, and the thickness of the ice sheet is still unknown, but further observations and hopefully future missions will enlighten us on Europa's mysterious structure.

 

Thera Macula (false color) is a region of likely active chaos production above a large liquid water lake in the icy shell of Europa. Color indicates topographic heights relative to background terrain. Purples and reds indicate the highest terrain. Image Credit: Paul Schenk/NASA

Jupiter's Ice Moon Europa: Part 1

 Image of Europa taken by the Galileo spacecraft showing surface ice and cracks

The Galileo spacecraft was launched in 1989, and in the 1990's gave astronomers their first up close and personal interview with Jupiter and its moons. One of many big discoveries was that Jupiter's 2nd closest moon, Europa, is a giant ball of ice! And the best part… it's water ice! Astronomers know the surface is water ice because of two main features. One is that albedo (reflectivity) of the planet is what we would expect for a planet covered in ice. Second, spectroscopy of Europa done in the infrared from the earth shows strong water absorption lines. Now that we know what the surface of Europa is made of, the question becomes "is there liquid water underneath that icy surface?" Astronomers speculate that the answer is yes. Based on Galileo images (above), Europa has a mostly smooth surface but exhibits large surface cracks as well (brown lines in the image). This is indicative of something like plate tectonics, where the ice plates sit on top of a liquid ocean and move around due to the motion of the sub-surface ocean. The only way to know for sure if there is a liquid ocean is to send a probe there to drill through the ice. This sort of probe may be in NASA's future, but recent discoveries based on the old Galileo observations suggest that liquid water has already been discovered! Tune in next time to learn more about this amazing discovery!

Image Credit: NASA/JPL

Earth from the ISS

Many pictures have been published on the web of Earth from outer space. Astronauts often take images of Earth from the International Space Station (ISS). The ISS is a satellite in low Earth orbit that houses up to 15 astronauts at one time. It is used to conduct low gravity experiments, monitor Earth's weather and learn how humans and plant life survive in outer space. Using onboard cameras and other instrumentation, astronauts can image every inch of Earth as they fly by. Below is a video compilation of  many images taken from the ISS from August-October of 2011. Note the beautiful aurora which forms at the top of Earth's atmosphere (defined by what looks like a thin yellow shell around Earth). You can also see city lights across all countries, and flashes of lightening within clouds.

Video credits are listed  here: http://vimeo.com/32001208

Earth | Time Lapse View from Space, Fly Over | NASA, ISS from Michael König on Vimeo.

Did the Moon Form From Earth?

Artists impression of the impact which formed our moon

There are many theories out there as to how Earth's moon formed. Some think the moon formed right with the earth out of the circumstellar disk of material around our young sun, others think that it is a captured object that got caught up in Earth's gravity and became our moon. The leading theory is that a Mars sized object crashed into Earth during the Late Heavy Bombardment, and broke off a chunk of earth that formed into the moon. But why do we think this is the case? Well first of all, measurements of  the amount of Tungsten-182 (decay product  of Halfnium-182) in returned moon rocks suggest that the moon appears to be ~100 million years younger than the Earth. I know that sounds like a long time, but it's really fairly short, considering the Earth is 4.6 billion years old. The age of the moon suggests that after the Earth was hit, the moon formed in a short period of time, but it took an extra 100Myrs for Earth to recuperate and reform back into a spherical planet. So this rules out the "same time formation" theory (the moon is younger). So what about the "captured rock" theory? Well, based on analysis of moon rocks and the lunar composition via satellite missions to the moon, we know that the moon is made almost solely of molecules that consist of oxygen (silica, alumina, iron oxide, sodium oxide, etc.). Measurements of the oxygen isotope ratios in rocks tell us that this ratio is almost exactly the same as that on Earth. It's very unlikely that a random captured rock would have exactly the same oxygen isotope ratios as we do on Earth, so the moon probably formed from a piece of the Earth!

Image Credit: Fahad Sulehria

GOES-R

Artists impression of GOES-R

Besides taking awesome pictures with telescopes and studying deep space, astronomers often work with geologists to study the structure of Earth and our weather patterns. One such endeavor is the Geostationary Operational Environmental Satellite (GOES) project, run by the US Environmental, Satellite, Data, and Information Service. Their job is to launch satellites that constantly study weather patterns on different part of the Earth so that the weather man can give us an "accurate" forecast each morning. The GOES satellites are in a geosynchronous orbit around earth. That means they orbit the Earth at the same speed at which the Earth rotates, allowing the satellite to appear stationary in space from a given spot on Earth. Currently there are 5 functional satellites (GOES 11-15), with the next generation (GOES-R, artists impression above) pending launch in 2015. Want to learn more about GOES, GOES-R and their mission pgoals? Have children that are interested in space and weather? Check out the GOES-R page for kids: scijinks.gov, or download the free game app: Satellite Insight.

Image credit: Lockheed Martin

Free Astronomy Apps

If you have an iphone or other smartphone, you've probably discovered that there are quite a few astronomy apps out there. Most of them cost a few bucks,  but there are some pretty cool free ones out there. Here's what I have downloaded to my iphone that you should check out for yourself:

Exoplanet Database: This is an awesome app if you're into exoplanets! It's a database with information about all the different exoplanets that have been discovered, and includes size, period, distance, and other useful information. You can read news about exoplanets, view where any exoplanet is located in the galaxy, make handy graphs of exoplanet properties, and even get links to scientific papers about the exoplanets. The coolest part about this app… it sends a text message to your phone every time a new exoplanet is discovered!

APOD Viewer Lite: An application that lets you view the astronomy picture of the day. It shows you the image, explanation, and lets you look back at previous images. Very nice app to quickly view today's APOD.

NASA: Basically this is NASA.gov in app form. You can find news,  launch schedules, pictures, videos, telescope info, and anything astronomy you can imagine. Excellent educational app.

ArXiv: This app allows you to search the astrophysics arXiv for scientific papers, and download the pdf to your iphone (using a pdf reader app). This is more for the serious astrophysicists, but anyone can peruse through the papers and maybe you'll find something interesting.

Galaxy Collider Lite: A cute app that shows you what would happen if two galaxies collided. I'm not sure how scientifically accurate the simulations are, but it's cool to watch the galaxies interact regardless. You can set the number of stars, mass of the galaxies, speed of collision, etc. and observe how that changes things

If you've discovered any other cool free apps, post them in the comments section below! Also feel free to leave your opinion about different non-free apps as well!

Near Earth Asteroid 2005 YU55

Most asteroids sit peacefully in the asteroid belt between Mars and Jupiter. Occasionally, some get kicked out due to tidal or gravitational forces between space objects, giving them their own orbit around the sun. Some of the stray asteroids pass fairly close to earth, and when they do we call them near earth asteroids. 

2005 YU55 imaged with the Arecibo radio  telescope

You may have heard talk on the news of a near earth asteroid called 2005 YU55 (pictured above). There's been a bit of hype about this object lately, but its just another member of the group of 8500+ near Earth objects that pass safely by Earth all the time. Now, "near" in the case of 2005 YU55 means that it will be 202,000 miles away from earth at its closest approach on November 8th, 2011. That's just a little bit closer than the moon is to Earth. So don't be alarmed by the news stories entitled "huge asteroid headed for close encounter with Earth"; there's nothing to worry about! NASA has assigned it a risk of 0 on their danger scale (ie. it's no big deal!)

Image credit:  NASA/JPL-Caltech

Acceleration Due To Gravity

We experience gravity everyday. It's the force that keeps our feet on the ground, makes apples fall from trees, and is occasionally cursed when you drop and break something. Newton may have "discovered" the theory of gravity, but it was Galileo (back in the 16th century) who claimed that all objects, regardless of their weight, shape, and size, fall at the same rate. In other words, the acceleration due to gravity is the same for all objects! Gravitational acceleration is governed by the size of the object causing the gravity. So here on Earth, gravitational acceleration (g) is 9.8m/s. So if I drop a hammer and a feather from the same height, they should reach the ground at the same time… right? Well scientifically, yes, but that often doesn't happen on Earth. Why? Well that's because we have a thick atmosphere and wind which causes air resistance. Lighter objects are more easily affected by wind, where as heavy objects are much less affected. So If do the hammer-feather experiment on Earth, the feather gets caught up in the wind and falls much slower that the hammer. But what happens in a place like the moon where there is  less gravity (1.8m/s) but no atmosphere and thus no air resistance. Do the hammer and the feather fall at the same rate? Let's find out…..

Video Credit:Apollo 15 Crew, NASA

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.

Spaghettification!

Earlier this week, a second grader asked me what would happen if an astronaut fell into a black hole. "Well, what do you think might happen?" I responded back. Another anxious second grader waved his hand high. "You would get stretched out like a noodle!" he said. Very good! These second graders know more about black holes than I thought! If an astronaut were to fall into a black hole, the gravity at the persons feet would be stronger than at their head, effectively stretching their bodies as thin as spaghetti. So guess what astronomers call that effect…. Spaghettification! No joke!

Black Holes Don't Suck!

I'm sure you've heard of a black hole before (If you've been reading ADYK you definitely have!) But what technically is a black hole? What is it made of? What does it do? Astronomers are still a bit uncertain about all of this, but here's what we think…

 

A black hole is defined as a singularity in space. This means that it is a point in space that is infinitely small and has infinite density. It's hard to think of an object like this in real life; one that can continually gain matter but stays extremely small. Most people have the impression that black holes "suck" in all the material around them. While black holes do attract matter, they are not like vacuums in outer space. Black holes warp the space time around them into giant funnels (like the cartoon above). This causes material to orbit black holes and fall towards the center, eventually falling past the point of no return. Because black holes have acquired so much mass, they have a very strong gravitational field. It's so strong that not even light can escape their grasp. This is why astronomers call them black holes. Astronomers still have so much more to learn about these bizarre objects, and as technology improves our knowledge will approve along with it.

Saturn's Rings and Enceladus

We all know Saturn as the big outer planet with the rings. Why does Saturn have such beautiful ring structure? Astronomers aren't entirely sure, but they must have formed back when Saturn was just an infant planet. Astronomers can, however, explain the existence of Saturn's outermost ring, the E ring. Where did this ring come from? The culprit is Saturn's Moon Enceladus!

Above is a recent image taken by the Cassini spacecraft which is currently orbiting Saturn and its moons. As you can see, there appears to be some material erupting from the surface of the moon, and indeed there is! Enceladus experiences what we call cryovolcanism, which means that it has volcanoes which spew water and ammonia when they erupt instead of hot rocky lava. These eruptions are so intense that the material actually leaves the planet and travels into outer space! Since Saturn's rings are so close to Enceladus, the water and other molecules get caught up in Saturn's gravitational field and form the outermost ring. This ring is technically unstable, which means the material will stay for a short time, but then be lost forever into space. That's no big deal though, because Enceladus is continually erupting and adding new material to the E ring.
Image credit: NASA/JPL-Caltech/Space Science Institute

Neutrinos Break the Speed Limit!

 It's by far the hottest news in physics and astronomy right now: neutrinos were found to move faster than the speed of light!

What are neutrinos and where do they come from?

Neutrinos are a subatomic particles. They are essentially the building blocks of atomic particles such as protons and neutrons which are inside atoms. Neutrinos come in different types (or flavors as particle physicists call it) and are often the result of nuclear reactions or radioactive decay of an atom. They are created in stars and supernova explosions, and we can also create them here on Earth using particle accelerator labs. Neutrinos are electrically neutral which means that they don't interact with things often and can therefore travel far distances and through thick objects without ever being bothered. As an example, the sun creates so many neutrinos that every square cm of our body is being hit with 65 billion neutrinos every second! That's right every second! And we never feel anything.

How do you measure the speed of neutrinos?

The first task at hand is to build a device that can detect neutrinos. It's very hard to stop a neutrino, but particle physicists have figured out a way to detect there presence. I'm not going to go into the details here, so you'll just have to take my word for it. The next task is measuring their speed, and that theory is simple. Velocity, or speed in a given direction, can be calculated by taking the distance traveled and dividing by the time it took to move that distance. It's the same concept as driving a car. The distance from point A to point B, divided by the time I took to get there, gives me my average traveling speed in miles per hour. Now imagine a very long underground vacuum tube like the one particle physicists have at CERN. Neutrinos are created at point A at a given time, travel down the tube, and are detected at point B some amount of time later. We know how long the tube is, and we know the departure and arrival time of the neutrinos, so we can calculate a speed!

Faster than light?

Assuming that neutrinos travel at the speed of light (which is the current theory), particle physicists knew how long it should take for the neutrinos to get form point A to point B. When they looked at the timestamps given by the computers, the neutrinos actually arrived at point B ~60 nanoseconds too early! (That's 0.000000060 seconds) This implies that they traveled faster than the speed of light! (By a very tiny amount, but still measurable). The team that conducted the experiment has been checking for any possible errors that they may have made, and have yet to find any.

If no mistakes were made, what does this mean?

Attempting to interpret this result has some pretty cool implications in the world of physics. What does it mean if a neutrino travels faster than the speed of light? Well it sort of means that the neutrino traveled backwards in time! Our sense of time is defined around the speed of light, so if something moves faster than light, it can be observed before it even occurs. Very weird to think about! Another option is that the neutrinos took "short cuts" through higher dimensions during their travels. In this sense, the neutrinos didn't travel faster than light, they just took a shorter path from point A to B that we as humans can not perceive. The final option is that certain parts of the theory of relativity are incorrect and objects can move faster than the speed of light, without traveling back in time or entering different dimensions. Which one of these solutions is right? Well we will have to wait for the next Einstein to come along and figure it out!

The Speed of Light

One of the first things you learn in physics or astronomy 101 is that the speed of light is a constant. We call it by the letter "c", and it's equal to 299,792,458 meters/second or 670,616,629 mph. According to the theory of relativity, nothing can travel faster than the speed of light. Why? It's not something Einstein made up, it comes from the theory of physics. Light has properties of both particles and waves. It tends to travel like a wave (similar to a sound wave), but interacts like a particle (like two objects bumping into each other). The crucial piece to all of this is that light has no weight. It can interact with objects, and it has energy, but no weight. So what does this have to do with speed? Physics says that as you move faster, your mass (how "heavy" you are in a sense) increases. Now I don't mean speeding up from 0 to 60mph in a car, I mean traveling very close to the speed of light. The closer you get to c, the "heavier" you get. If a person were to travel at the speed of light, their mass would be infinity. This is why people, or other massive objects, can't travel at light speed. But since light waves/particles have no mass, they can travel at the speed of light no problem! Experiments show us that light has no mass, and travels a given speed "c". Therefore, any object with zero mass can travel at a maximum speed of c. And since objects can not have negative mass, there is no physical way for anything to travel faster than c. Or is there?.... Tune in later this week to learn about objects called neutrinos that may somehow have the ability to travel faster than the speed of light!

UARS has landed!

You're safe! UARS landed around midnight EST. The map above shows the path the satellite mostly likely took before it hit the ground early this morning.  NASA is still unsure about exactly where it hit, but speculates it was somewhere in the ocean along the green path above since no one reported seeing the crash.

UARS crash landing

 

 Images of UARS tumbling through the atmosphere

Have you heard on the news lately about a NASA satellite that's crashing to Earth this Friday? This object is called the Upper Atmosphere Research Satellite (UARS). It was put into orbit around Earth back in 1991, and spent 14 years studying Earth's ozone layer and our atmosphere in general. In 2005, the satellite was decommissioned because only half of the instruments on board were still functional, and the satellite had already lasted 11 years longer than it's original planned science mission. UARS had some fuel on board which it used as thrust to place itself on a decaying orbit, causing it to eventually fall back to Earth. The satellite will crash land on Earth this Friday afternoon, September 23rd, 2011. As UARS flies through the atmosphere, it is expected to burn up into as many as 26 different pieces ranging from a few pounds up to 400 lbs. These pieces will crash to Earth at speeds of up to 240mph, and are expected to be scattered over a 500mile wide area. NASA does not yet know exactly where the satellite will crash land, but they think it will land somewhere East of North America. If the satellite were to land in a populated area anywhere in the world, the estimated death rate is 1/3200. Hopefully UARS will land harmlessly in the middle of the ocean! Check out Spaceweather.com for more information on where UARS will land, and when you will be able to see it cross the sky. This fireball of a satellite should be visible on Friday even in broad daylight!

What is Space Like?

Ed White, the first American to perform a space walk. Image credit: NASA

You've learned so much about planets, moons, stars, galaxies, and all sorts of other astronomical objects, but do you have any idea about what space is really like? Outer space in general is very very cold. It's temperature is roughly 2.7 Kelvin, or -455 degrees F. Space is almost a perfect vacuum. A perfect vacuum is defined as an area of space with zero gas molecules. Outer space contains about 5 Hydrogen atoms per cubic meter. For comparison, on Earth there is about 10^25 gas molecules per cubic meter (that's a 1 with 25 zeros after it!). Space may be empty of molecules, but it's filled with light, most of which our eyes can't perceive. In the solar system, the sun emits all different types of light, from X-rays to microwaves. Earth's atmosphere blocks a majority of this light, but in outerspace there is nothing to block this light.  These are some of the many reasons why astronauts must wear space suits. With essentially no air to breathe, freezing temperatures, and deadly radiation, an astronaut would survive about 30 seconds if they took off their space suit. NASA has spent many years building spacecrafts and spacesuits that can withstand the harsh conditions in Space. They have done a pretty good job so far, but space is also very unpredictable. You never know what's going to happen out there!

The First Tatooine!

Anyone who has seen Star Wars remembers Tatooine, the home of Luke and Anakin Skywalker. Astronomers have found a real Tatooine! Well, they have found a planet with two suns at least. It's probably nothing like how George Lucas portrayed it though. 

Kepler 16-b is the first circumbinary planet ever discovered. It was first observed by the Kepler Space telescope on July 7th, 2011. The planet orbits a binary star system (Kepler-16) where one star is 70% the mass of the sun and the other is about 25%. In the system, the two stars orbit around each other, and the planet has an orbit surrounding the both of them . The planet is believed to be half rock and half gas,  roughly the size of Saturn, and orbits the stars in about 228 days. An interesting point of the discovery is that the three objects all orbit in the same plane. It's as if the stars and planets are balls on a table, orbiting each other but sitting on an imaginary flat surface. This supports the theory that this planet formed from a circumbinary disk; a disk of gas and dust that surrounded the binary star system as they were forming. Until now, astronomers weren't sure that the conditions were stable enough around a binary star system for a planet to form. The discovery of Kepler 16-b will help astronomers improve their star formation models, and maybe we will find more circumbinary planets in the future!

Image Credit: NASA

Exoplanet Update

Artists impression of a "puffy" planet. A comparison to Jupiter is in the bottom right

Exoplanets just fascinate me. The fact that there are potentially millions of other planets and planetary systems in outer space just blows my mind. Planets are being discovered literally on a daily basis. In the past week almost 100 new exoplanets were discovered or confirmed by various telescopes and space agencies. So today I thought I'd talk about a few of the most interesting ones.

Corot-2b: This planet was discovered back in 2007, but a huge discovery about it's interaction with its host star has just been made. The Chandra X-ray observatory just discovered that this planet is being pummeled by X-rays from Corot-2! X-rays are not good for humans, and they are not good for planets either! This roughly 3 Jupiter mass planet is being hit by 100,000 times more X-rays than the earth gets hit with every day. These harmful rays are evaporating the gas that the planet is made of at a rate of 5 million tons per second! Now I know that sounds like a lot, but the planet is so massive that at this rate of evaporation it will still survive for over 30 billion years!

HAT-P 32b, 33b, 24b and others: These are what I like to call "puffy" planets. Puffy planets are half to one Jupiter mass in weight but two Jupiter radii or larger in size and orbit their host star on the order of days. Essentially they are really big, lightweight, fast orbiting planets. They are peculiar because one would expect the planets to be smaller either due to solar wind/X-rays stripping material from them, or just general gravitational collapse of their small amount of gas. Astronomers are currently working on models to describe such planets.

HD 85512-b: This is today's newest possibly habitable planet. HD 85512-b is orbiting a star about 3/4 the size of our sun with an orbital period of 58 days. It's technically too close to the star to be in the habitable zone, but if the planet is rocky, and has sufficient cloud cover, it could potentially be habitable. Much more work needs to be done before we will know if it has the potential to support life.

Image Credit: D. Aguilar

GRAIL

Artists impression of GRAIL

Even though the space shuttle program has ceased, NASA is still alive and active with eyes towards the moon. On Saturday, September 10th around 9am EST, NASA launched the Gravity Recovery and Interior Laboratory (GRAIL) spacecraft from Cape Canaveral, FL. GRAIL is a set of two satellites that will orbit the moon and map its gravitational field. The moon has about 15% the amount of gravity we experience here on Earth, mainly because it is only about a quarter of the size of Earth. Understanding the moons gravitational field will help scientists understand the moons interior structure reconstruct its past. We will be able to answer questions like: Does the moon have a molten core? Why do the craters on the light side of the moon appear to be filled with solid magma, while those on the dark side do not? One interesting thing about the launch of GRAIL is its journey to the moon. A trip to the moon for the space shuttle took about 3 days, but GRAIL is going to take 3.5 months! The rocket was actually aimed in the direction of the sun, and with the help of small thrusters the trajectory will be corrected so that the satellites will reach the moon. This is called a low-energy trajectory and was done intentionally to save fuel, and to leave time for the satellites and equipment to adjust for space conditions. Think about it like this: if we hurtle towards the moon in three days, it will take a lot of fuel and energy to slow the satellites descent so they don't crash into the moon. But if instead we go the "long way around" and leisurely approach the moon, we can just float into orbit using very little fuel only to adjust trajectory. In these hard economic times, NASA is trying to save every penny they can!

Image credit: NASA/JPL/MIT

Solar Spectrum

So how do we know that the sun is made mostly of Hydrogen, Helium and a handful of other elements? Astronomers use a technique called spectroscopy and here is how it works.

White light really consists of all the colors of the rainbow. You can make the colors appear by shining a light through a prism (just like the cover of that Pink Floyd album).  Astronomers use a device called a spectrograph which is mounted on a telescope and has the ability to split light into all the colors of the rainbow. What's the purpose of all this? The sun generates white light in its core as Hydrogen fuses into Helium. Each light particles (called a photon) has a slightly different amount of energy. This is what actually causes the rainbow. Red light has a certain energy, while blue light has a little bit more energy, and we perceive this energy difference as a difference in color.

 The chemical elements within the sun are made of protons, neutrons, and electrons. Thinking back to your chemistry days, the electrons orbit the outside of the atom, while the protons and neutrons make up the core or nucleus. These electrons sit in "energy levels" and light (photons) have the ability to excite these electrons to higher energy levels. When a photon hits an atom, if that light has just the right amount of energy, the electron will absorb the photon and be "excited". Electrons around different elements require different amounts of energy to get excited.

So here's the connection. If the Sun is made of lots of Hydrogen, then colors of light that excited Hydrogen electrons will be absorbed by the Hydrogen atoms in the sun. So when we look at the Sun's spectrum (above) we see black lines where color has been absorbed by different elements. These are called absorption lines. In chemistry labs we can see what absorption lines Hydrogen, Helium and other elements produce. Then when we have a spectrum from the sun, we can look for specific absorption lines from different elements and decipher what the sun is made of! Spectroscopy is used to figure out what stars are made of, along with the atmospheres of planets, and even giant clouds of gas in outer space! The image above is the entire visible spectrum of the sun. We see many absorption lines caused by Hydrogen, Helium, and other heavier elements.