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with an observer from Red Deer, Bob Gosselin. When theopportunity presents itself, he said he would take the southernlimit, saving us from a longer drive and of course providinganother chord.You may be wondering, “Doesn’t the asteroid rotate as itmoves?” Yes, but most of these events take only a few minutesto cross the face of the Earth, so it typically does not matter. But,an extraordinarily well-observed event spanning continentscould reveal a change in shape, though this has yet to be done.This was a really fun way to do science — we are eagerlyawaiting more asteroid occultations.Alister Ling enjoys all aspects of visual astronomy sincediscovering Jupiter with a 4.5-inch Tasco in the mid-1970s.Slowly but surely, he is adding impartial scientific measurementto the mix; the challenge is to do it unattended so he can keepthe eye at the eyepiece when it’s clear!On Another WavelengthM81/M82 & Arp’s Loopby David Garner, Kitchener-Waterloo Centre (jusloe1@wightman.ca)Figure 1 — M81 and M82 image courtesy of Ron Brecher, Kitchener-Waterloo Centre. Exposure: 51 x 90-sec unguided exposures using amodified Canon Digital Rebel XT, 105-mm f/6 refractor, and HutechLPS filter. Acquired and processed with Images Plus.The M81 Group of galaxies, containing M81 and M82along with several smaller associates, is located 12million light-years away in the constellation UrsaMajor. M81, also known as NGC 3031 and Bode’s Galaxy, isa beautiful type Sb spiral galaxy. It appears to have an activegalactic nucleus that is very luminous across the entireelectromagnetic spectrum. This extraordinary luminosity atthe core of M81 may be caused by hot gas spiralling into asupermassive black hole lurking at its centre. As gas falls intosuch a black hole, it can be heated to millions of degrees andemit extremely intense radiation.M81 is found at right ascension 09h 55m 33.2s,declination +69° 3´ 55“, and has an apparent magnitudeof 7.89, which is beyond the naked-eye limit for most of us.The way to find M81 by starhopping is to look for the BigDipper, start at the bottom-inside star (Phad) of the bucket,go diagonally up and across to the top of the bucket (Dubhe).This line points almost directly at M81, which is about thesame distance again as your diagonal line.In Figure 1, M82, an irregular galaxy (a.k.a. the CigarGalaxy), can be seen somewhat edge-wise near the top, tothe left of M81. Both galaxies can be viewed with binoculars,but you will need at least an 8-inch telescope to see anystructure.M81 and M82 have been tugging on each othergravitationally for the past billion years and now appear tobe orbiting around each other with a period of about 100million years. M82 seems to have suffered recently from aclose encounter with M81, causing it to form several darklanes throughout its structure. As a result of the interaction,density waves of gas have created many star-forming areascharacterized by bright blue stars in both galaxies. Theseare found in M81’s spiral arms and scattered around M82’souter areas. Gravitational interactions have also caused infallinggas to create many hot blue stars in the centres of thegalaxies. Today, M82 is usually described as a starburst-typegalaxy with stars forming at a rate fifty to a hundred timesfaster than a normal galaxy of its size.Since massive stars generally have short lifespans, astar in M82 explodes on average about every ten years. Theseviolent explosions heat the surrounding gas, blasting it outof the galaxy and creating filamentary structures with acharacteristic red (Hα) colour that extend perpendicularlyoutward from the galaxy core. Because all the hot new starsin M82 radiate and heat up any nearby dust clouds, M82 isalso the brightest infrared galaxy in the sky.Recently, researchers (deMello et al. 2008), using datafrom the Galaxy Evolution Explorer (GALEX) satellite and the76 Celebrating the International Year of Astronomy (IYA2009)JRASC April / avril 2009