Galaxy Hunting Season Opens for Skywatchers

Late spring and early summer is the prime time for hunting galaxies. Generally clear skies and pleasant evening temperatures make this a favorite activity for amateur astronomers around the time of new moon, such as this week.

When you look at images like the deep field view from the Hubble Space Telescope, which shows a wealth of galaxies in a single slice of the universe, you might assume that galaxies are pretty evenly spread around the sky.

Basically that?s true, but we can?t always see them because other things get in the way. The main "other thing" is the Milky Way galaxy, which wraps around the sky and effectively blocks our view of distant galaxies in that band.

What happens in late spring in the northern hemisphere is that the Milky Way lies close to the horizon, so that our view overhead is at right angles to the plane of the Milky Way.

As a result, we can see beyond the Milky Way with minimum interference. By a happy coincidence, the greatest collection of galaxies in our neighborhood also lies in that direction, the so-called Virgo group. [Amazing galaxy photos.]

This sky map shows the prime target zone for skywatchers to hunt for Virgo group galaxies in the night sky.

Whatever catalog of deep sky objects you choose to use, a large proportion of the galaxies in it will lie in the constellation Virgo, with similar large numbers in the adjoining constellations Coma Berenices, Ursa Major, Leo, and Canes Venatici.

Galaxy-hunter extraordinaire

The most popular catalog of deep sky objects among amateur astronomers is that compiled in the late 18th century by French comet hunter Charles Messier, after whom Messier objects are named.

Charles Messier?s catalog contains 110 of the finest deep sky objects, and includes 40 galaxies. Of these 11 are in Virgo, 7 in Coma Berenices, 6 in Ursa Major, 5 in Leo, and 3 in Canes Venatici: 32 out of 40 in only 5 constellations, including two constellations (Coma Berenices and Canes Venatici) which most people have never heard of.

The greatest concentration of galaxies lies on the border between northern Virgo and Coma Berenices. Many beginners at deep sky observing are reduced to terror at the thought of exploring this region because of its many galaxies and very few stars. Yet, if you go about it systematically, it?s not very hard to explore.

The secret to mastering the Coma-Virgo cloud of galaxies is to concentrate on the galaxies, not the stars. Don?t try star-hopping: try galaxy-hopping instead.

The jumping off point for any exploration of this region is the interesting star Rho Virginis.

This star is about a quarter of the way from Vindemiatrix (Epsilon Virginis) to Denebola (Beta Leonis) and reminds some observers of one of the hubs in a child?s Tinkertoy construction set: a bright star with three fainter stars marking the "spokes." The brightest of these three "spokes," on the north side of Rho, points directly at a trio of bright galaxies slightly more than a degree away and falling in a straight line: Messier 60, Messier 59, and Messier 58, from left to right.

How to spot galaxies

Although these galaxies are "bright" in the eyes of experienced amateur astronomers, most beginners will probably have a lot of difficulty seeing them.

There are several things you can do to increase their visibility. The first, and most important, is to observe from a dark location free of light pollution.

It is increasingly hard to find such spots in our modern over lit world. One of the many good reasons for joining an astronomy club is that its members have probably identified the best observing spots in the local area, and meet regularly there to observe.

An important technique for observing faint objects is what is called "averted vision." The most sensitive part of the human eye is not right in the center, but slightly off to one side.

As a result, if you look slightly to one side of your target area, you are more likely to see it than if you look straight at it.

Skywatching eye tricks

Finally, our eyes are better at detecting moving targets than stationary ones, so it often helps to move or tap the telescope to bring out really faint objects like galaxies.

Once you have spotted these three galaxies north of Rho Virginis, continue the line of galaxies the same distance to the right, and you can?t miss Messier 87, the largest known galaxy and one of the brightest in the sky. Extend this line by the same distance again, and you will encounter the attractive pair of Messier 84 and Messier 86.

Where else can you find six bright galaxies forming a straight line?

Move back to Messier 87 and slightly beyond, so that you pick up Messier 58 as well. Using these two galaxies as the two bottom corners of an equilateral triangle, look for a third galaxy, Messier 90, as the third corner of the triangle to the north. Right in the middle of this triangle of three bright galaxies is a fourth smaller galaxy, Messier 89.

Draw an imaginary line from Messier 58 to Messier 90 and continue it the same distance beyond. There you should find Messier 91, probably the faintest and most difficult of all the Messier objects. Just to its right is a much brighter galaxy, Messier 88.

As you might guess from the numbers Messier gave these galaxies, he observed seven of them (Messier 84 to 91) for the first time during a single night, March 18, 1781.

The other three (Messier 58 to 60) were observed two years earlier, on April 15, 1779. It?s a sobering thought to look at those dates and realize that, while revolutions were bursting all around him, Messier was calmly observing the night sky and cataloging the beautiful objects which he found there.

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This article was provided to SPACE.com by Starry Night Education, the leader in space science curriculum solutions.