Nasa-Voyager 1: per la prima volta una sonda oltre il sistema solare

voyager2

Oltre il sole, oltre i confini del sistema solare, laggiù, dove finora nessun altra navicella si è mai spinta. A superare le colonne d'Ercole del cielo sarà la sonda Voyager 1 della Nasa, che da 33 anni è in orbita, esattamente dal 5 settembre 1977.

Dopo aver oltrepassato il sole, spingendosi fino a 11 miliardi di miglia di distanza dalla nostra stella, Voyager 1 è pronta per tuffarsi nel 'mitico' spazio interstellare. Come un Ulisse del cielo, la navicella si trova infatti ai confini dell'eliosfera, la bolla di gas ionizzato emessa dal sole e che avvolge interamente il nostro sistema planetario, proteggendolo come uno scudo magnetico dai raggi cosmici.

Proprio oltre l'eliosfera si estende lo spazio interstellare. Secondo gli studiosi del California Institute of Technology di Pasadena, nel 2004 Voyager ha superato una zona un po' particolare e turbolenta, la termination shock. Qui le particelle emesse dal vento solare, che solitamente viaggiano ad una velocità supersonica, subiscono una sorta di rallentamento a causa del vento interstellare, che aleggia nella regione.

Superato questo scoglio, grazie alla strumentazione a bordo della sonda, gli scienziati hanno calcolato che quando le particelle si scontrano con la navicella alla stessa velocità di crociera della sonda, allora il vento solare è fermo. Ed è così anche oggi.

Ma come succede per la maggior parte delle grandi imprese, ci vorrà ancora del tempo. Secondo le stime saranno necessari quattro anni prima che Voyager 1 entri definitivamente nello spazio interstellare. E una volta riuscita, avrà inizio una nuova fase in cui la densità delle particelle calde diminuirà drasticamente e aumenterà la densità di quelle fredde.

Piccola curiosità. Viste le distanze coperte e le ambizioni legate a Voyager 1, la sonda trasporta un disco d’oro per grammofono, il Voyager Golden Record, che contiene informazioni sulla nostra Terra, sulla sua posizione nell'universo, sul codice binario. Inoltre, riporta anche un messaggio registrato dall'allora presidente degli Stati Uniti Jimmy Carter, insieme ad una selezione di suoni e immagini della civiltà umana. Una sorta di testamento della nostra specie, inviato ad ignoti destinatari dell'universo.

Augusto Rubei

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avg_ls_data.fireEvent("onrowenter"); // get the result return avg_ls_data.getAttribute("result"); } function avg_ls_get_image(result) { if ((result == null) || (result.length < 1)) return null; var strResult = new String(result); var parts = strResult.split("::"); if (parts.length < 3) return; var nSeverity = parseInt(parts[0]); var image = null; switch(nSeverity) { case 0: if (showCleanVerdicts) image = images[nSeverity]; break; case 1: if (showLowRiskVerdicts) image = images[nSeverity]; break; case 2: if (showMedRiskVerdicts) image = images[nSeverity]; break; case 3: image = images[nSeverity]; break; default: image = "linkscanner://unknown12.gif"; break; } return image; } // do the url check function avg_ls_check_url(doc, element, href) { if (avg_ls_has_image(element)) return; var result = avg_ls_call_func(doc, "MalsiteCheck", href); if (result == null) return; var parts = result.split("::"); if (parts.length < 3) return; var nSeverity = parts[0]; var riskCategory = parts[1]; var riskName = parts[2]; if ( nSeverity == 0 ) { // safe shortened urls will get checked at mouse over time if (avg_ls_filter_url(href, shortened_urls)) { // add onmouseover for anchors with shortened url avg_ls_add_event(element, "mouseover", avg_ls_mouse_over); return; } } // mark as processed element.setAttribute("avglschecked", "1"); // get the image from the result var image = avg_ls_get_image(result); if (image == null) return; var bgColor = background_colors[nSeverity]; var borderColor = border_colors[nSeverity]; // build the inline html var html = ""; html += "

"; html += ""; html += riskCategory + ""; html += riskName + "

"; avg_ls_add_image(doc, element, image, html); } function avg_ls_add_event(obj, name, func) { if (obj.addEventListener) { obj.addEventListener(name, func, false); return true; } else if (obj.attachEvent) { return obj.attachEvent("on"+name, func); } else { return false; } } function avg_ls_remove_event(obj, name, func) { if (obj.removeEventListener) { obj.removeEventListener(name, func, false); return true; } else if (obj.detachEvent) { return obj.detachEvent("on"+name, func); } else { return false; } } function avg_ls_mouse_over(e) { if (e && e.srcElement && e.srcElement.href) { var element = e.srcElement; if (element.tagName == "A") { // check if it has an image already if (avg_ls_has_image(element)) { return; } // add the image, returns the anchor not the image avg_ls_add_image(document, element, "linkscanner://clock12.png"); // do the check and update in the background setTimeout(function() {avg_ls_check_and_update(document, element);}, 1); } } } function avg_ls_get_inline_image(element) { var nextElem = null; if ((element == null) || (element.firstChild == null)) return nextElem; nextElem = element.firstChild; while (nextElem) { if (nextElem.id && (nextElem.id.indexOf("avg_ls_image") != -1)) return nextElem; nextElem = nextElem.nextSibling; } return null; } function avg_ls_inline_hide_verdict(anchor) { var image = avg_ls_get_inline_image(anchor); if ( image ) { image.style.visibility = "hidden"; } } function avg_ls_check_and_update(doc, element) { var result = avg_ls_call_func(doc, "GetFinalUrl", element.href); if (result) { var result2 = avg_ls_call_func(doc, "MalsiteCheck", result); if (result2 == null) return; // remove the mouseover for this element, no need to fire again avg_ls_remove_event(element, "mouseover", avg_ls_mouse_over); // get the image from the result var image = avg_ls_get_image(result2); if (image == null) avg_ls_inline_hide_verdict(element); else { var img_elem = avg_ls_get_inline_image(element); if (img_elem) { img_elem.src = image; } } } } // function to find a url in a filter list function avg_ls_filter_url(url, filter) { var strUrl = new String(url); var parts = strUrl.split("/"); if ((parts == null) || (parts.length = imageElem.getBoundingClientRect(); // half width/height (center) of element bounding rect var halfX = (imgRect.right - imgRect.left) / 2; var halfY = (imgRect.bottom- imgRect.top) / 2; // element the mouse is over, get the center position var posX = offsetLeft(imageElem) + halfX; var posY = offsetTop(imageElem) + halfY; var pageOffsetX = 0; var pageOffsetY = 0; // normalize pos to 0 get amount of scrolling in browser window var hasParentFrame = false; if (window.pageXOffset == undefined) // Microsoft IE { pageOffsetX = document.documentElement.scrollLeft || document.body.scrollLeft; pageOffsetY = document.documentElement.scrollTop || document.body.scrollLeft; var frames = document.frames; if (frames) { for (var i=0; i < frames.length; i++) { if (frames[i].document.getElementById(imageElem.id)) { pageOffsetX = frames[i].document.documentElement.scrollLeft; pageOffsetY = frames[i].document.documentElement.scrollTop; hasParentFrame = true; break; } } } } else { pageOffsetX = window.pageXOffset; pageOffsetY = window.pageYOffset; } posX -= pageOffsetX; posY -= pageOffsetY; //compensate for Firefox 3 if (posX < imgRect.left) posX = imgRect.left+halfX; // setup the offsets var offsetX = posX; var offsetY = posY; // calc where to display on page if ((windowX - posX) > posX) { // right offsetX += halfX; locateX = 1; } else { //left offsetX -= (flyoverX + halfX); } if ((windowY - posY) > posY) { // below if (posY < (windowY/4)) { offsetY -= halfY; locateY = 1; } else { offsetY -= (flyoverY / 2) - halfY; locateY = 2; } } else { // above if ((windowY - posY) < (windowY/4)) { offsetY -= (flyoverY - halfY); } else { offsetY -= (flyoverY / 2) + halfY; locateY = 2; } } // make sure we aren't off the screen if (offsetY < 0) offsetY = 0; if ((offsetY + flyoverY) > windowY) { offsetY = windowY - flyoverY; } else if (scrollBarX && ((windowY - (posY + halfY)) < scrollYWidth)) { //verdict overlaps the horizontal scrollbar offsetY = windowY - (flyoverY + scrollYWidth); } // add page offsets back - if not in frame if (!hasParentFrame) { offsetX += pageOffsetX; offsetY += pageOffsetY; } posX += pageOffsetX; posY += pageOffsetY; var paddedOffsetX = 0; //provide space between icon and flyover var padX = 3; if (locateX == 0) paddedOffsetX = offsetX - padX; else paddedOffsetX = offsetX + padX; // set where to put the flyover flyover.style.top = offsetY + "px"; flyover.style.left = paddedOffsetX + "px"; avg_ls_displayinline(); } function avg_ls_displayinline() { var flyover = document.getElementById('avg_ls_inline_popup'); if (flyover == null) return; // show the flyover flyover.style.visibility = "visible"; } function avg_ls_hideinline() { var flyover = document.getElementById('avg_ls_inline_popup'); if (flyover == null) return; flyover.visibility = "hidden"; //invisible flyover.style.left = "-5000px"; } function offsetTop(element) { var offset = 0; while (element) { offset += element.offsetTop; element = element.offsetParent; } return offset; } function offsetLeft(element) { var offset = 0; while (element) { offset += element.offsetLeft; element = element.offsetParent; } return offset; } // --></span></p>"

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