STARGAZER #485 for August 9, 2008

A Collision of Galactic Proportions


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
vaporized?"

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.

Next Two Weeks. Avg. sunrise: 6:54 a.m.; avg. sunset: 8:11 p.m. (exact for
Waco, TX)
* Wednesday (Aug. 13) evening, low in the west a half hour after sunset,
Venus is a moonwidth to the left of Saturn.
* The evenings of Aug. 14-16, Venus (brightest), Saturn, and Mercury
(faintest) are grouped together.
* The Aug. 16 full Moon, called Green Corn Moon and Grain Moon, features a
partial eclipse not visible here.
* The evening of Aug. 20, Mercury is two moonwidths below Venus.

Meteor Shower. The Perseid meteor shower, usually one of the best, peaks
Monday night and Tuesday morning, 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.

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.

Stargazing Class. Paul's free 4-session Learning the Night Sky course is
Aug. 18-21, 7:30 - 9:30 p.m. Call or email for more information or to register.


=======================================================

Stargazer appears every other week in the Waco Tribune-Herald and other
Texas newspapers. Paul Derrick is an amateur astronomer who lives in Waco.
Write him at 918 N. 30th St., Waco, TX 76707, call or fax at (254) 753-6920, or
e-mail at paulderrickwaco@....

Copyright 2008 by Paul Derrick. Permission is granted for free electronic
distribution as long as these paragraphs are included. Please obtain
permission from the author for publication in any other form. To be added to
(or
removed from) the free e-mail distribution list, send your e-mail address (and
name) to _paulderrickwaco@..._ (mailto:paulderrickwaco@...) .


* * See the Stargazer Web site at http://www.stargazerpaul.com. * *





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**************Looking for a car that's sporty, fun and fits in your budget?
Read reviews on AOL Autos.
(http://autos.aol.com/cars-BMW-128-2008/expert-review?ncid=aolaut00050000000017
)


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