Planets, planets everywhere!

Wow, it’s been a longg time since I last posted.  I attribute this to my crazy semester (hard classes + applying for graduate schools = close to no free time).  I still have one final left, but I really wanted to post about the exciting planet news that came out today!

In case you haven’t heard, NASA has confirmed the discovery of the FIRST Earth-sized exoplanets (exoplanets are planets outside our solar system)!  There have been a lot of planet discoveries in the news lately.  A lot of this is due to NASA’s Kepler satellite, which looks for exoplanet candidates.  Kepler detects small dips in the brightness of stars, which can be due to objects passing in front of them.  If a dip occurs regularly and in even intervals, you  know there is an object orbiting that star.  One then needs to conduct follow up observations with another telescope to confirm that the object is a planet.

Today, two new confirmed exoplanets – Kepler 20e and Kepler 20f – were announced.  Kepler 20f has a radius 1.03 times that of Earth’s, and Kepler 20e is even smaller – it has a radius of .87 times that of Earth’s.  Although both planets are Earth-sized, they aren’t as hospitable as our home planet.  Kepler 20e and 20f are both close to their sun-like host star, meaning they are very hot.  Kepler 20e is more than 1400 degrees F, and Kepler 20f is about 800 degrees F.

NASA chart showing how the sizes of Kepler-20e and Kepler-20f compare to Earth and Venus. (http://www.nasa.gov/mission_pages/kepler/multimedia/images/kepler-20-planet-lineup.html)

Although these two planets aren’t exactly the Earth-twin we’ve been searching for, it seems that it’s only a matter of time before we find it!

To read more follow this link!

Planetary Nebulae

Today is International Astronomy Day!  So, I’ve decided to discuss one of the coolest, most aesthetically pleasing astronomical phenomena – planetary nebulae.

Planetary nebulae arise at the end stages of a sun-like star’s lifetime.  Generally, stars that are between .8 and 8 solar masses will result in a planetary nebula.  Stars are powered by nuclear fusion in their cores.  When a sun-like star fuses all the hydrogen in it’s core to helium, it burns hydrogen in a shell surrounding the core. It eventually gets hot enough for the helium in the core to start fusing heavier elements.  The star burns helium and hydrogen alternately, causing instability in the star.  These instabilities cause the star to eject its outer layers in a planetary nebula.  The planetary nebula lasts about 10,000 years, and at the end, all that is left is a white dwarf.

Planetary nebulae come in a wide range of shapes.  Some are round, some are hourglass, some look like barrels.  It is still unknown how the most complex planetary nebulae get their shapes, although it is thought that it may be due to magnetic fields, binary star systems, or both.

An example of a beautiful, round planetary nebula.

An example of a crazy looking planetary nebula.

Planetary nebulae are one way in which elements are distributed throughout our universe.  As the planetary nebula fades away, the elements contained within it stay in the interstellar medium, possibly enriching future generations of stars.

My boyfriend calls this the (one-armed) turtle nebula.

Another crazy looking nebula.

All images taken from the Planetary Nebula Image Catalogue.

Happy 21st Anniversary Hubble!

The Hubble Space Telescope

Today is the 21st anniversary of the Hubble Space Telescope!  21 years ago, Hubble was carried into orbit, and since then, it has given us some of the most spectacular images of our universe and making incredible contributions to science.

Some of Hubble’s contributions include:

• Helping to narrow the age of the universe to between 13 and 14 billion years
• Making the first direct measurement of the chemical makeup of an exoplanet’s atmosphere
• Capturing extremely detailed images of the comet Shoemaker-Levy 9 exploding in Jupiter’s atmosphere
• Showing the wide variety of planetary nebulae morphologies that exist

Here are some exquisite images taken by the Hubble Space Telescope.

This image of two interacting galaxies was released in honor of Hubbles 21st anniversary.

The Hubble Ultra Deep Field, which contains galaxies formed just 700 million years after the Big Bang

The Eagle Nebula, a tower of gas and dust

The Cat's Eye Nebula - a planetary nebula with an amazingly complex shape

Messenger spacecraft goes into orbit around Mercury

Mercury

This morning, the Messenger spacecraft became the first spacecraft to go into orbit around Mercury.  Mercury is our solar system’s smallest planet, and it is also the closest planet to the sun.  Mercury has a highly elliptical orbit, with it’s distance from the sun varying between 28.5 million miles and 43 million miles (for perspective, Earth is 93 million miles away from the sun).  It took Messenger 6 and a half years to reach Mercury and then position itself in such a way that it could go into orbit.  Messenger will get as close as 124 miles to the surface of Mercury. Mercury has an average surface temperature of 336 degrees Fahrenheit, but can get as hot as 800 degrees Fahrenheit and as cold as -280 degrees Fahrenheit.

During its entire mission, Messenger will complete 730 orbits around Mercury, completing one orbit every 12 hours.  Messenger will collect data about Mercury’s composition, surface features, magnetic field, and exosphere.  Mercury’s gravity is not strong enough to maintain an atmosphere, but it does have an unstable exosphere containing a variety of elements and water vapor.

Messenger's orbit around Mercury (from http://messenger.jhuapl.edu/index.php)

Before Messenger, the last spacecraft to visit Mercury was Mariner 10 in the 1970s.  Mariner 10 flew past Mercury three times and provided a lot of new information, but left the majority of Mercury’s surface un-mapped.  Messenger has already flown by Mercury three times, in order to achieve the proper alignment for going into orbit.  It has already achieved a great deal, including finishing much of the mapping and drawing out Mercury’s magnetic field.

Artist's impression of Messenger (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

Now that it is in orbit, Messenger can begin to collect data that can help us solve unanswered questions.  Scientists want to learn more about Mercury’s composition to help understand its 5.3 g/cm³ density, the highest in our solar system.  Scientists also want to study the structure and dynamics of Mercury’s core.  Mercury’s magnetic field suggests a partially molten core, but as of now, little is known about it.

Exciting exoplanet news!

Today, the Kepler mission announced the discovery of over 1,200 exoplanet candidates, bringing the total number of planets candidates found by Kepler to 1,235!

Kepler Exoplanet Candidates (image from nasa.gov)

The planet candidates break down as such:

• 68 ~Earth size
• 288 Super-Earth size
• 662 Neptune size
• 165 Jupiter size
• 19 larger-than-Jupiter size

And here’s the really exciting part: 54 of these planet candidates are in the habitable zones of their stars, and of those, 5 are near Earth sized.

These planet candidates are based on about 4 months of observing, and Kepler’s field of view only covers about 1/400th of the sky.  So just imagine how many Earth sized, habitable-zone planets there are in all of our galaxy!

They have also found a system of six confirmed planets orbiting the sun-like star, Kepler-11.  All six of the planets are bigger than Earth and all have orbits smaller than the orbit of Venus.  This is one of two confirmed multiple-planet systems, the other being Kepler-9, which has 3 confirmed planets orbiting the star.

A bit about exoplanet detection: Kepler locates planets by searching for a small dip in the brightness of a star, which is caused by an object crossing in front of it.  If that dip occurs in regular intervals, it tells you that there is an object in orbit around that star.  The amount that the star’s brightness decreases tells you how big the orbiting planet is.  Kepler also uses ground based telescopes and the Spitzer Space telescope for follow up observations on candidates.

Planets that are in the habitable zones of sun-like stars will probably take a few years to detect; you would only see a transit about once a year, and three transits are required for exoplanet verification.

AAS 217 Highlights

I’ve spent the better part of this week in Seattle at the American Astronomical Society Conference in Seattle, so I decided to write a post about some of the highlights.

I got to attend lots of great talks at the meeting.  Here are some summaries:

• “Cassini Eyes the Rings of Saturn“, a talk given by Carolyn Porco, discussed some recent discoveries by the Cassini spacecraft, which is orbiting Saturn.  Little moons embedded in Saturn’s rings can actually clear spaces in the rings (360-degree gaps or partial gaps).  This is the first time moons have been tracked while inside disks.  It is believed that ~100 large bodies are currently in orbit inside Saturn’s A ring.
• “Chandra’s First Decade of Discovery”, given by Harvey Tananbaum, talked about some important findings made by the space based Chandra X-Ray Observatory since it started operating.
• The session “Super Earths and Terrestrial Planets” contained several mini talks about recent discoveries by the Kepler space-based telescope.  In a talk given by William Borucki, it was announced that Kepler has recently discovered its first confirmed rocky planet! The planet, Kepler-10b, has a radius 1.42 times that of Earth, and has a temperature of 1833 K.
  

  Panel about Kepler-10b from the Kepler booth at AAS

• “The First Supermassive Black Holes”, given by Mitchell Begelman, was dedicated to discussing two different schools of thought about supermassive black hole formation.  One theory is that they formed from Population III stars.  The alternate theory discussed was that they formed from the direct collapse of gas clouds.
• My favorite talk was “New Science with Old Stars” given by Anna Frebel, this year’s recipient of the Annie Jump Cannon Award.  Anna Frebel does high resolution spectroscopy, and she has discovered the oldest known star, and the most metal-poor star.  She researches these extremely old stars to try to answer questions about the formation of our galaxy.  Metal poor stars, having formed before the universe was significantly enriched with metals by supernovae, can help us put together the history of our galaxy’s formation and aid us in understanding the origin and evolution of chemical elements.  The metallicity of a star is defined as its iron to hydrogen ratio.  The most metal poor star has an iron to hydrogen ratio that is 1/250,000 that of the sun.  The oldest known star is dated at around 13 billion years.

While in Seattle, I also got to do some sightseeing, which was exciting since I’ve never been there.  My friends and I went up to the top of the Space Needle, but it was so windy that we couldn’t stay out very long.  We could even feel the building swaying back and forth.  Apparently it sways about an inch for every 10 mph of wind.

The Space Needle

The poster sessions where people display their work on posters are also a lot of fun to go to.  Various organizations, telescopes, and companies have booths at the poster sessions, and some are pretty elaborate.  They also give away wall posters, pens, pamphlets, and things like that, so now I can cover my wall with posters of galaxies and stars.  Overall, I had a great time in Seattle; I learned a lot and got to see a lot of great talks and posters.  I can’t wait for next year’s AAS!

From a display at AAS

10 yr. old girl becomes youngest to discover a supernova!

Kathryn Gray, age 10, discovered a supernova in an image taken by amateur astronomer David Lane.  The supernova is in the galaxy UGC 3378, which is 240 million light years away.  Kathryn began searching for supernovae last year after she learned about a 14 year old who had discovered one.  Lane had sent images to Kathryn’s father, and she found it when checking over the images.  (Source: cnn.com)

The recently discovered supernova.

Supernovae are generally classified into one of two types.

1. Type Ia: These supernovae occur in a binary system consisting of a white dwarf and a companion star.  The white dwarf accretes matter from its companion star.  As the white dwarf gets more massive, its temperature rises, and uncontrolled fusion of carbon and oxygen occurs, detonating a supernova.
2. Type II: These occur in stars that are about 8 times as massive as the sun.  These stars are capable of fusing elements up to iron, and thus have iron cores.  When the iron core reaches the Chandrasekhar Limit (1.4 solar masses), the electron degeneracy pressure can no longer support it, and it collapses. As outer layers collapse inward, a shock wave rebounds and the star explodes in a supernova.

(Source: NASA)

Lunar Eclipse Tonight!

I just wanted to remind everyone that tonight there will be a lunar eclipse.  A lunar eclipse occurs when the sun, earth, and moon are aligned such that the earth blocks the sun’s rays from the moon.  Instead of being illuminated by the sun, the moon will fall into earth’s shadow and will have a really cool dark reddish hue.  The lunar eclipse will occur over approximately three and a half hours, beginning around 1:30 AM (EST).  It will reach totality around 2:40 AM.  If you can, definitely set your alarm, bundle up, and go take a look – there won’t be another one until 2014.  Tonight’s eclipse is also extra special because it falls on the winter solstice – December 21st – for the first time in centuries.  Unfortunately for me, the eclipse will be interrupting some much-needed sleep before my quantum mechanics final Tuesday afternoon.  I think it’s worth it