Itty Bitty Planetary System

Astronomers are working very hard to confirm the existence of potential exoplanets identified by the Kepler space telescope. One such confirmation was made recently, and it's the "smallest" one yet!

 

KOI-961 is a red dwarf star. This means that it still has fusion in its core, but it's much smaller than the sun. In fact, it's only 13% the mass of the sun, and is slightly larger than Jupiter in size! The image above shows KOI-961 and its three planets (to scale) next to Jupiter and four of its moons for a comparison of size. KOI-961 was not originally identified by Kepler as having an exoplanetary system. Astronomers from CalTech looked at the public data released by Kepler, and saw something suspicious in the light curve. They observed this star using both the Palomar Observatory and Keck Observatory, and their results confirmed the existence of a 3 planet system! The planets masses are unknown, but their sizes are ~0.57, 0.73 and 0.78 Earth radii. This suggests that they are rocky planets similar in size to Mars. Planets 1 and 2 are too close to the star to harvest life, but planet 3 is just on the inner edge of the habitable zone! Much more work is needed before we can truly speculate the existence of life on this planet, but the more discoveries we make, the better chance we have of finding a planet just like Earth!

Image Credit: CalTech

GalaxyZoo

If you're following ADYK, you've just learned about spiral and elliptical galaxies, and the Hubble classification scheme for galaxies. Astronomers have so many pictures of galaxies from various telescopes, and need help classifying all of them. Don't worry, there's no need to memorize the Hubble tuning fork or even know anything about galaxies! If you can look at pictures and answer some simple questions then you're good to go!

GalaxyZoo.org is part of NASA's zooniverse project. Zooniverse is a website where the general public can help astronomers study real astronomical data from telescopes. Basically you chose from a variety of tasks, such as classifying galaxies, measuring moon craters, looking for supernova, searching for exoplanets, etc., go through a short training session, and now you are the astronomer! The general public has helped astronomers make many new discoveries, just by spending a little time on zooniverse.  Check out GalaxyZoo today, maybe you will be the next one to make a big discovery!

Hubble Classification of Galaxies

The Hubble tuning fork diagram was developed by Edwin Hubble as a way of classifying galaxies based on their shape. Basically, astronomers look through a telescope at a galaxy, and classify it as an elliptical, spiral, or barred spiral. These classifications were discussed in the last ADYK. If the galaxy looks like a fuzzy bright blob, it's classified as an elliptical (E), and a number is assigned based on how round it looks (1=circle, 9=cigar shaped). If a galaxy has deifned circular rings, but not exactly spiral arms, then it's an "S0".  If the galaxy appears to have spiral arms, it's either a regular spiral galaxy (S), or a spiral with a bar like structure through the center (SB). They are also assigned a letter based on how tightly wound the spiral is. "Sa" means tightly wound arms, while "Sc" is very loosely wound arms. These classifications are handy for astronomers, as they can relate the properties of galaxies to their classification. Hubble originally thought that this diagram represented a time sequence, i.e. all galaxies started as round ellipticals (E0), and evolved over time into spirals (SBc or Sc). Astronomers are now able to measure the ages of many galaxies, and we've found some young ellipticals and old spirals, so the tuning fork diagram does not represent a galaxy evolution sequence. One thing to remember is that this classification is based on actual galaxy shape, not observed. For example, from Earth's perspective, you might view a spiral galaxy edge on, but think it's an E7 elliptical because it appears that way. Because of this, it's not easy to classify these galaxies accurately. You can actually help astronomers do this! Check out the next ADYK!

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)