Recently Eric and his 14-year old son, Tristan, of Johannesburg, South Africa, asked in an email: “What would happen if there was another galaxy headed on a collision course with our galaxy? Would we know about it before we were vapourised?”

The answer contains both bad and good news. The bad news: another galaxy IS on a collision course with our Milky Way galaxy. The even larger Andromeda galaxy is headed our way and the collision will spell the end of our galaxy as we know it.

So where’s any good news in that? Fortunately, it will happen 5 billion years down the road. So don’t quit your job, drop out of school, or cancel your life insurance.

What’s more, while there will no longer be a Milky Way or Andromeda galaxy, neither will be vaporized. According to astronomers Abraham Loeb and T.J. Cox (“Our Galaxy’s Date with Destruction,” Astronomy, June 2008), the collision will result in the merger of the two galaxies, producing a gigantic galaxy which, combining the names, they dub “Milkomeda.” Such mergers, visible in amateur scopes, are common throughout the cosmos.

Although both galaxies contain billions of stars, the likelihood is that few will actually collide with other stars. Galaxies consist mostly of empty space (ignoring the speculative existence of “dark matter” about which astronomers know so little.)

If our Sun was the size of a Ping-Pong ball, the next nearest star would be 625 miles away—that’s about four or five Ping-Pong balls within an area size of Texas. So we needn’t worry about being vaporized by a stellar crash when the galaxies collide.

Still, we’re not completely off the hook. The Milky Way-Andromeda merger will, by coincidence, occur about the time our Sun dies, and when that happens, Earth almost certainly will be vaporized, but again, that’s far into the future.

Nearer-term threats are far more likely to come from asteroid and comet impacts. That’s why, in my view, our species must allocate more resources to finding and tracking these objects, and devising realistic strategies and means for dealing with them when threatening ones do come our way—and it’s just a matter of time.

• Sky Calendar:

•11/12 Mon. evening/Tue. morning: The Perseid meteor shower, usually one of the best, peaks with the best viewing likely from 2 a.m. until dawn, after the moon sets. Perseus, from which Perseids seem to radiate, is in the east.

•13 Wed. early evening: Venus passes within a moonwidth of Saturn very low in the west 30 minutes after sunset.

•14-16 Thu.-Sat. early evenings: Venus (brightest), Saturn, and Mercury (faintest) are closely grouped near the western horizon 30 minutes after sunset; binoculars will help.

•16 Sat.: The full Moon, called Green Corn Moon and Grain Moon, features a partial eclipse not visible here.

•20 Wed. early evening: Mercury is two moonwidths below much brighter Venus just above the western horizon.

•28 Thu. morning: The crescent Moon is less than three moonwidths above the Beehive cluster low in the east before dawn.

•Naked-eye Planets. (The Sun, Moon and planets rise in the east and set in the west due to Earth’s west-to-east rotation.) Evening: Venus, Saturn and Mercury are very low in the west with Mars well to their upper left; Jupiter is the brilliant object in the southeast. Morning: There are no morning naked-eye planets visible after Jupiter sets around 4 a.m.

Stargazer appears every other week. Paul Derrick is an amateur astronomer who lives in Waco. Contact him at 918 N. 30th, Waco, 76707, (254) 753-6920 or paulderrickwaco @aol.com. See the Stargazer Web site at stargazerpaul.com.