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

Cecilia Payne-Gaposchkin

Cecilia Payne was born in England in 1900.  While attending Newham College at Cambridge University, Cecilia became interested in astronomy.  She studied physics at Cambridge, but was not awarded a degree, because Cambridge did not offer degrees to women at the time.  She received a fellowship to do research at the Harvard Observatory under the direction of Harlow Shapley, the director of the Harvard Observatory.  She started there in 1923.

Cecilia Payne-Gaposchkin

She received her PhD in astronomy from Radcliffe College, and became the first person (male or female) to receive a PhD in astronomy from Radcliffe.  Her dissertation is extremely highly regarded, and thought by some to be the most brilliant astronomy PhD thesis ever written.  Her dissertation was entitled “Stellar Atmospheres, A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars”, and it argued that the variations observed in the spectral absorption lines of stars are due to temperature, not due to different stellar compositions.  She also (correctly) suggested that stars were composed mainly of hydrogen.  The fact that we can determine the temperature of a star based on it’s spectrum is absolutely integral to astronomy.  However, many doubted Cecilia’s results because they thought that all astronomical bodies had the same relative amounts of elements.  In her thesis, deferring to those more highly regarded, she wrote that her results were almost certainly incorrect.  But within a few years, most astronomers accepted that hydrogen was more abundant in the sun than on earth.

After completing her thesis work, she was hired by Harvard to continue work in the Harvard Observatory.  In 1926, at age 26, she became the youngest person to ever be featured in American Men of Science.  She married Russian astronomer Sergei Gaposchkin in 1934.  Cecilia collaborated with Sergei in studying all variable stars brighter than 10th magnitude.  These results were published in 1938 in Variable Stars, which became a standard reference in the field.  However, Cecilia’s work was unrecognized and unappreciated at Harvard.  She taught courses, but until 1945, none of them were listed in the Harvard course catalog.  When Harlow Shapley was replaced by Donald Menzel as the director of the Harvard Observatory, Cecilia was given a raise, promoted to professor, and named the chair of the astronomy department.  She was the first woman at Harvard to hold a position that was not specifically for a woman.

Until her death in 1979, Cecilia wrote over 150 papers and published four books on stars and stellar evolution.  In 1934, she received the Annie Jump Cannon prize from the American Astronomical Society.  She received honorary doctorates from many colleges, and, in 1976, became the first woman to be granted the American Astronomical Society’s Henry Norris Russell Prize.

Cecilia Payne-Gaposchkin helped pave the way for women who came after her.  Women were rarely involved in the sciences in her time, and especially not women with children.  But Cecilia had three children and continued to do her research.  She once shocked superiors by giving a lecture while she was five months pregnant.  Her legacy lives on through her magnificent contributions to astronomy.

Sources: 1/2/3/4

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.

Annie Jump Cannon

Turns out I have wifi on my flight! Since I have about four more hours until my first flight lands in San Francisco, I have lots of time to kill.  In light of the American Astronomical Society Conference, I thought I’d write a short biography of Annie Jump Cannon, the astronomer who developed the Harvard Spectral Classification scheme for stars.

For those of you who are not familiar, the Harvard Spectral Classification scheme is arguably the most used scheme for classifying stars.  At the time it was developed, it contained 7 spectral types, O,B,A,F,G,K, and M.  Spectral type “O” corresponds to the hottest stars, with temperatures roughly above 30,000 K.  Spectral type “M” corresponds to very cool stars, with temperatures below 3,500 K.  Since even cooler stars have been discovered, the L and T spectral types have been added.

Annie Jump Cannon

 

Annie Jump Cannon (1863 – 1941) developed an interest in astronomy through her mother, who would show her constellations.  Annie attended Wellesley College, where she was a physics major.  While there, she also learned how to make spectral measurements and did observing.   In 1894, Annie became a junior physics teacher at Wellesley and studied astronomy at Radcliffe.  In 1896, she was hired by Edward Charles Pickering, the director of the Harvard College Observatory.  She was one of many women to be hired by Pickering. Known as “computers”, they were hired to reduce data and do calculations and classifications.  Nettie Ferrar had started developing a classification system, but only stayed at the Harvard Observatory for a few months.  Her work was picked up by Williamina Fleming, who developed a scheme that had classes A through Q.  Another woman, Antonia Maury, who did theoretical work, developed her own independent scheme.  Annie Cannon worked off of these schemes to develop the OBAFGKM scheme, which was theoretical like Maury’s, but simplified and elegant.

In addition to developing this classification scheme, Cannon published information about over 200,000 stars to the Henry Draper Catalog.  She later published the Henry Draper Extension, which brought her total number of classified stars to about 350,000.  She also discovered 300 variable stars.

Annie Jump Cannon was the first woman to receive an honorary degree from Oxford University.  She also received honorary doctorates from Wellesley College, Mount Holyoke College, Oglethorpe University, the University of Delaware, and Groningen University.  Harvard finally awarded her a professorship in 1938, 2 years before her retirement.

(Sources: Wellesley College, Harvard, San Diego Supercomputer Center)

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)