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