jrasc june 1998 final - The Royal Astronomical Society of Canada

rasc.ca

jrasc june 1998 final - The Royal Astronomical Society of Canada

From the Editorby David TurnerDespite the Earth’s 510 million km 2 surface area, it is arelatively small target for potential impacting objectsin the solar system. Most residents of the CanadianShield are aware, however, that the chances of collision withlarge pieces of orbiting space debris — comets and asteroidsin particular — are far from negligible. The Observer’s Handbookcatalogues about twenty recognized, sizeable, impact sites onthe Shield alone, and there are a small number of other sitesin the rest of Canada. The inventory continues to grow (seeJRASC, 89, 111, 1995). The Sudbury region bears the scars oftwo different impacts, one of which, Lake Wanapitei, is a scenic,deep, 7.5-km diameter, water-filled lake that lies off the northeastedge of the much older and much larger Sudbury basin. Anobject perhaps half a kilometre in diameter produced the former,while an object possibly twenty times larger produced the latter.Such large-sized impactors are much less common than thesmaller meteoroids that collide with the Earth daily and giverise to meteors — of the shower and sporadic variety — andthe occasional fireball. Yet they do exist in sufficiently largenumbers that collisions with Earth in future may occur. Themain focus of those who study Near-Earth Objects (NEOs) isthe discovery and tracking of such objects.It appears that Hollywood has recently discovered thepublic’s growing awareness of the possibility of a future collisionwith a large NEO, since two of the new movies released totheatres for the summer season have plots based on the threatof collisions of a comet or asteroid with Earth. In an interestingturn of events, somewhat unexpected publicity for the movieswas generated in March by an announcement from BrianMarsden of the International Astronomical Union’s CentralBureau for Astronomical Telegrams that the recently-discovered,two-kilometre diameter asteroid 1997 XF 11 could pose such athreat in 2028. The news was released in the standard form ofan announcement in the IAU telegram service to the internationalastronomical community, and also as a press release to thenews media. Both proved to be very effective. A search by EleanorHelin through her collection of asteroid survey films turnedup images of 1997 XF 11 taken in 1990. The new positions increasedthe baseline for the orbital calculation, and the newly derivedorbit for the object ruled out the possibility of its collision withEarth in 2028. The news media also gave considerable publicityto the story, which as it turns out was not entirely a good thing.The apocalypse/no apocalypse nature of the news headlinesrelated to the story placed Brian Marsden at the focus of criticismfrom concerned individuals within the astronomical community.In similar manner, our light-hearted, anonymous, advicecolumnist Gazer became the focus of disgruntled Questar usersfollowing his advice to “Anxious in Athabasca” in the Februaryissue. Canada has a long tradition of humour related to makinglight of our foibles, and Nova Scotia is no exception — “Halifax,the Disaster Capital of the World (The Titanic Gravesites, TheHalifax Explosion of 1917, City Council)” proclaimed a recenteditorial cartoon. However, it appears from the heavy responseto Gazer’s column that the collection of Questar users is lesstolerant of comments about their telescopes, however lightheartedin intent those comments may have been. In order toprovide “equal time” for the other side of the story, this issuecontains an article by Clive Gibbons that offers a balancedappraisal of his experiences using a Questar telescope.June/juin 1998 JRASC107

More magazines by this user
Similar magazines