Plot the amount of light detected by a spacecraft as it observes a planet transiting a star.

Background: There are several ways to find new planets.  First, scientists can sometimes measure the wobble of the parent star caused by the gravity of the hidden offspring planet.  Second, they can detect a Doppler shifting of the star's light spectrum as the orbiting planet repeatedly moves toward us, then away.  Third, they can look for dips in brightness that reveal planets blocking out a little light as the planets orbit the star within our plane.

The Kepler spacecraft is monitoring over 150,000 stars simultaneously as it looks for planets around distant stars. For comparison, imagine looking down from a skyscraper at 150,000 streetlights that are miles away and you hope to see some gnats flying in front of a few lights. If the insect passes in front of the streetlight along your line of sight, the amount of light you see will dip by a minute amount.  It may be too little for your eyes to notice, but the spacecraft is capable of discerning such small dips in brightness.

In this activity, the light from a star covers several pixels on a simulated computer chip.  From afar, the star would appear as a mere point of light, but the closer you get the more you can see and count distinct pixels.  For simplicity, students will count the number of pixels that reach the sensor for the duration of a transit.  A recurring, periodic dip in brightness suggests a planet is orbiting the host star, whereas a random dip in brightness may indicate any object, such as a nearby asteroid in our own solar system, is intersecting the light path between the star and the spacecraft. 

To Do:  Print or display the 15 snapshots, left, of a transit.  On graph paper, plot the numbers of yellow squares (y-axis) per unit of time (x-axis).  You may want to begin with multiple t=0 pixel counts to show the normal state of the scene with no transit, from which the curve can begin.  The units of time are not defined for this activity, but a transit may last for several hours. Compare the graph derived by the students with actual data from a transit, right.  To speed up the activity in a class, assign each kid the t=0 time frame just to make sure they are all on the same track.  Then have the kids choose a partner to count the lone second snapshot you designate for them. 

Read more: Activity: Pixel Count

Party like it's 2012! 

If you are hosting a Transit of Venus celebration, here are some items to consider.  See the 2004 Celebration in Mishawaka, IN, for scenes of an observing site. 

Months before:

• Scout out event sites, with consideration given to unobstructed sight-lines, security, parking, restroom availability, electricity, internet access, and absence of lights with glare (for telescope viewing later that night). 
  
• Secure permission from landowner or government entity to conduct event at that site. 
  
• Get approval for tents or trailers to be set up adjacent to or near scopes, especially for telescope owners who come from afar.
  
• Invite amateur astronomers with telescopes and solar filters to set up their scopes for public viewing. Ask them to stay beyond twilight for stargazing session and planet-viewing (Mars and Saturn).
  
• Invite local musicians or school bands to perform John Phillip Sousa's Transit of Venus March or other ToV music.
  
• Put out a call for Transit of Venus art through a local art organization or advocate.  
• Purchase solar viewing equipment, whether simple or major.  Realize that with just solar shades, Venus is small--near the limit (about a minute of arc) of what the human eye can discern.  Don't wait for last minute when supplies are hard to get.

  Read more: Plan a Community Celebration

The Harris Branch Library at 51446 Elm Road in Granger, IN, will be the site of two special events leading up to the 2012 transit of Venus. 

From May 1 to June 9, 2012, the Northern Indiana Pastel Society will coordinate an art exhibit by its members that features the transit of Venus and the curious realm of exo-planets.  The call for art invites members to use ideas such as Venus, planets, sun, moon, stars, space, sky, sunset, new worlds, habitable planets or related themes.

Concurrently, the exhibit cases flanking the library entrance foyer will house historical artifacts from previous transits of Venus, including original contents from the US Naval Observatory (USNO) expeditions. 

The two events support a collection of transit of Venus attractions, known as TROVE, in the Michiana region.  Plan a visit to to this and other TROVE sites for a complete transit of Venus experience. 

For the location, contact information, and hours of operation, see the Harris Branch at http://www.mphpl.org/newSite/general/contact_branch.html. 

View Mishawaka - Penn - Harris Public Library in a larger map

A Special Session of the American Astronomical Society (AAS)
History of Astronomy Division (HAD)
Sunday, Jan 08, 2012, 1:00 PM - 3:40 PM

Details

The June 6, 2012, transit of Venus, completing the pair that began on June 8, 2004, will represent the last chance to observe one of these rare events from Earth until the next pair, December 11, 2117, and December 8, 2125. This year’s transit will be extremely advantageous as almost all the most populated areas of the Earth will be able to see at least some of the transit: the only land masses from which no part of the transit will be visible are the western Iberian peninsula, the western part of Africa, the eastern part of South America, and Antarctica. We invite presentations on both important historical aspects of the transits of Venus and modern applications. From a historical point of view, the occasion is of importance in providing a point of departure for a reconsideration of the singular importance of the transits in the history of astronomy and in the geographical exploration of the Earth, which led to massive preparations and far flung expeditions in the eighteenth century in pursuit of the Halleyan project of determining the solar parallax. The nineteenth-century transits also played out against a background rivalries among the great European world empires (England, Russia, France, and the U.S.) then at their height and then sliding imperceptibly but ineluctably toward the Great War. The 2012 transit offers an opportunity to revisit the important expeditions of the past—many of which have been catalogued and some noted by markers or restored—and to engage in “experimental archaeology,” the reconstruction of past observations, including of the Black Drop and luminous aureole, about which it was and is often mistakenly stated that, particularly for the earliest observations, it is produced by refraction by the atmosphere of Venus. Possible observations of special historical interest in 2012 could include some using historical instruments and techniques or observing from the same locations as earlier observers. But far from being an entirely retrospective exercise, the history of transit observations defines critical problems to be addressed by modern high-resolution observations from Earth and space. These include the detailed profiling of the atmosphere of Venus with ground-based and space-based observations (from satellites meant to study the Sun) and the study of a local analogue to exoplanet transits across their parent stars, the focus of many contemporary astrophysical investigations and space missions whose key astrophysical goals are to understand the prevalence and structure of planetary systems very different from our own solar system. In short, though often said to be of strictly historical interest owing to the fact that the Halleyan solar parallax method has long since been superseded, transits of Venus continue to be of great importance to astronomers and astrophysicists working at the cutting edge of important problems of our own day. See http://www.transitofvenus.info and http://www.transitofvenus.org.

Read more: Transits of Venus: Looking Forward, Looking Back

Cleveland Astronomical Society Meeting
Thursday, March 1, 2011
Speaker: Chuck Bueter

Observers on the North Coast are well-positioned to see the last transit of Venus in our lifetimes on Tuesday, June 5, 2012.  The celestial phenomenon begins shortly after 6:00 p.m. EDT, when the inner planet appears to straddle the solar limb and is visible until the sun sets with Venus halfway across the sun.  In past centuries, transits of Venus were significant as nations collaborated to quantify the size of the solar system and embarked on global expeditions.  Today the rare alignment exemplifies how astronomers detect planets orbiting distant stars using the transit method.  We have a front row seat, and can view with our eyes what the NASA Kepler Mission hopes to capture many light years away with its sensitive photometer.  With some tips, caveats and legal disclaimers, Chuck's presentation will encourage you to do what Momma (and smart astronomers) generally advise against--stare at the sun. Bring safe observing opportunities to your community, participate actively in a transit of Venus experiment and marvel at the solar system in motion on June 5, 2012.

Details at http://www.clevelandastronomicalsociety.org/Mar%201%20Meeting.htm.