Some­thing extra­or­di­nary hap­pens this week. The plan­et Venus will move across the face of the Sun for the last time in our lives.

Tran­sits of Venus occur on a 243-year cycle, with pairs of tran­sits eight years apart sep­a­rat­ed by gaps of 121.5 and 105.5 years. The last Venus tran­sit hap­pened in 2004. The next won’t occur until Decem­ber of 2117. So if you want to see one, don’t put it off! “This is it, folks,” said Robert Naeye, Edi­tor in Chief of Sky & Tele­scope mag­a­zine. “Unless mod­ern med­i­cine comes up with a mir­a­cle to extend human lifes­pans, this tran­sit of Venus will be your final oppor­tu­ni­ty to watch our sis­ter plan­et cross the Sun’s fiery disk as seen from Earth.”

The event will take place tomor­row, June 5, or the next day, June 6, depend­ing on your loca­tion. In North Amer­i­ca the tran­sit will begin tomor­row, just after 6 p.m. East­ern Day­light Time. Because of the great dis­tance between the Earth and Venus, the dura­tion will be far longer than for a Solar eclipse: over six hours.

Here are six tips for mak­ing the most of this last-of-a-life­time event:

1: Read up about it. For a quick and neat­ly orga­nized overview your best bet is astronomer Chuck Bueter’s Tran­sit Of Venus.org. The site includes all kinds of use­ful and inter­est­ing infor­ma­tion, includ­ing the video above.

2: Find out when you can see it from your loca­tion. The inter­na­tion­al non-prof­it group Astronomers With­out Bor­ders has cre­at­ed an extreme­ly handy Web page that will auto­mat­i­cal­ly gen­er­ate a sched­ule of the tran­sit for your loca­tion, based on your com­put­er’s IP address. The site allows you to choose between a sim­ple graph­ic rep­re­sen­ta­tion (the default set­ting) or a more detailed data sheet. It even pre­dicts the like­li­hood of cloud cov­er where you are.

3: Pre­pare for safe view­ing. Look­ing direct­ly into the sun can cause severe and per­ma­nent eye dam­age. There are a num­ber of safe ways to view the tran­sit of Venus, but it’s essen­tial that you fol­low the advice of experts. Bueter has pub­lished an overview, “Six Ways to See the Tran­sit.” Rick Fien­berg of the Amer­i­can Astro­nom­i­cal Soci­ety has pub­lished a detailed arti­cle on how to build a “sun fun­nel.” And Doug Dun­can, direc­tor of the Uni­ver­si­ty of Col­orado’s Fiske Plan­e­tar­i­um, has cre­at­ed a video explain­ing a very sim­ple way to safe­ly project an image of a solar event onto a two-dimen­sion­al sur­face using a pair of binoc­u­lars.

4: Check for events in your area. If you fol­low the links in step three you should be able to watch the tran­sit on your own, but you might have more fun–and learn more–if you join a group. Astron­o­my clubs, plan­e­tar­i­ums and oth­er sci­ence groups will be host­ing tran­sit-view­ing events around the world. Check your local list­ings or go to the NASA Sun-Earth Day Web site for a com­pre­hen­sive round-up of events across the globe. Just scroll the map on the NASA site over to your own geo­graph­ic region and zoom in.

5: Down­load the app. If you have an Apple or Android device you can down­load a free Tran­sit of Venus phone app that will allow you to send your own obser­va­tions of the tran­sit to a glob­al exper­i­ment to mea­sure the size of the Solar Sys­tem. “In cen­turies past,” writes Steven van Roode of Astronomers With­out Bor­ders, which is orga­niz­ing the project, “explor­ers trav­eled around the globe to time the tran­sit of Venus to deter­mine the size of the solar sys­tem. We invite you to inspire inter­na­tion­al col­lab­o­ra­tion dur­ing the 2012 tran­sit of Venus by enabling a dig­i­tal re-cre­ation of those glob­al expe­di­tions. The phone app will allow cit­i­zens around the world to wit­ness this rare phe­nom­e­non and to con­tribute their obser­va­tion to a col­lec­tive exper­i­ment to mea­sure the sun’s dis­tance.” Also, Sky & Tele­scope is help­ing peo­ple make the most of the tran­sit by offer­ing free use of its Sky­Week astron­o­my app through June 7. You can down­load it for iPhone or Android.

6: Watch the web­cast. If you are unable to get a clear view of the tran­sit from your location–or even if you are–you should check out either of a pair of live web­casts which will be held dur­ing the event. Astronomers With­out Bor­ders will trans­mit its web­cast live from the Mount Wil­son Obser­va­to­ry in Cal­i­for­nia. The pro­gram will include inter­views with experts and con­tri­bu­tions from ama­teur astronomers, along with video tours of the his­toric obser­va­to­ry and its equip­ment, both antique and state-of-the-art. You can access the Astronomers With­out Bor­ders web­cast here. Anoth­er major web­cast will be broad­cast by NASA from Mau­na Kea, Hawaii begin­ning tomor­row at 9:45 p.m. UTC (Coor­di­nat­ed Uni­ver­sal Time) or 5:45 p.m. East­ern Time. You can access the NASA web­cast here. For a sched­ule of the pro­gram, which will include many videos and inter­views through­out the event, you can down­load a PDF.

British astronomer William Crab­tree, depict­ed observ­ing the 1639 tran­sit of Venus in a mur­al at Man­ches­ter Town Hall, paint­ed in 1903 by Ford Madox Brown.

Have you ever won­dered how astronomers fig­ure out the mind-bog­gling dis­tances between the Earth and var­i­ous astro­nom­i­cal objects? In this infor­ma­tive ani­mat­ed video from the Roy­al Obser­va­to­ry at Green­wich, we learn the fun­da­men­tals of the Cos­mic Dis­tance Lad­der, the suc­ces­sion of meth­ods used to deter­mine those dis­tances.

The video was made for “Mea­sur­ing the Uni­verse: from the tran­sit of Venus to the edge of the cos­mos,” an exhib­it that will be on dis­play at the obser­va­to­ry through Sep­tem­ber 2. The exhib­it is timed to coin­cide with this year’s rare tran­sit of Venus, which will be vis­i­ble from Earth on June 5 and 6 and won’t hap­pen again until 2117. The tran­sit of Venus played a key role in the his­to­ry of astrom­e­try. In 1663 the Scot­tish math­e­mati­cian and astronomer James Gre­go­ry pro­posed a method of tim­ing the move­ment of Venus across the Sun from two wide­ly sep­a­rat­ed points on the Earth and using the dif­fer­en­tial to cal­cu­late the sun’s mean equa­to­r­i­al par­al­lax and, by tri­an­gu­la­tion, the Sun’s dis­tance from the Earth.

Know­ing the dis­tance from the Earth to the Sun, we can then fig­ure out the dis­tances of some stars using the same method of trigono­met­ric par­al­lax. But as astronomer Olivia John­son explains in the video, that tech­nique can only be used to mea­sure the clos­est stars. For dis­tances greater than 500 light years, oth­er meth­ods are required. When the objects in ques­tion have a known luminosity–in oth­er words, when they are “stan­dard can­dles”–the inverse square law of light can be used to cal­cu­late dis­tances. Those mea­sure­ments, along with Hub­ble’s Law and the Doppler Effect, enable even fur­ther cal­cu­la­tions extend­ing to the edge of the known cos­mos.

“What’s most incred­i­ble to me,” says John­son, “is how all these mea­sure­ments build on each oth­er. It’s only by know­ing the scale of our Solar System–the dis­tance between the Earth and Sun–that we’re able to mea­sure dis­tances to near­by stars using par­al­lax. If we can learn how far it is to some near­by stan­dard can­dles using par­al­lax, we can then use com­par­isons between stan­dard can­dles to mea­sure the dis­tances to far­ther stars and galax­ies. Final­ly, by study­ing the motions of galax­ies with stan­dard can­dles, we learn we can use red­shift to mea­sure dis­tances through­out our expand­ing Uni­verse.”

via Devour

Relat­ed Con­tent:

The Hig­gs Boson, AKA the God Par­ti­cle, Explained with Ani­ma­tion

Imag­ine a star (like our sun) wan­der­ing close to a super­mas­sive black hole and find­ing itself mer­ci­less­ly ripped apart by this beast weigh­ing mil­lions to bil­lions times more than the hap­less star. It does­n’t hap­pen very often. But when it hap­pens, it’s pret­ty spec­tac­u­lar. And now NASA has pro­duced a com­put­er sim­u­la­tion show­ing this spec­ta­cle, draw­ing on evi­dence gath­ered by NASA’s Galaxy Evo­lu­tion Explor­er and the Pan-STARRS1 tele­scope locat­ed in Hawaii. Here’s how NASA describes what you’re see­ing in the clip above:

Some of the stel­lar debris falls into the black hole and some of it is eject­ed into space at high speeds. The areas in white are regions of high­est den­si­ty, with pro­gres­sive­ly red­der col­ors cor­re­spond­ing to low­er-den­si­ty regions. The blue dot pin­points the black hole’s loca­tion. The elapsed time cor­re­sponds to the amount of time it takes for a Sun-like star to be ripped apart by a black hole a mil­lion times more mas­sive than the Sun.

NASA has more infor­ma­tion on this stel­lar homi­cide here.

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