Looking Up: Take in the galactic scenery tonight

Peter Becker

The next clear, spring evening, treat yourself to a journey beyond belief. Step outside and look up at the southern sky. Far behind the glittering field of stars and the planet Saturn capturing your attention is one of the largest structures ever found, an immense collection of galaxies moving together through the universe, bound by mutual gravitational attraction.

This is the Virgo Supercluster, one of millions of superclusters in the observable universe. As wide as 110 million light years, the Virgo Supercluster contains about 200 “galaxy groups,” about 2,500 large galaxies and about 50,000 dwarf galaxies. The estimated number of stars approaches 200 trillion in this region.

It’s not only the closest supercluster, it is OUR supercluster. The Milky Way Galaxy -- and several other nearby galaxies forming what we call the “Local Group” -- is on the outskirts.

All the thousands of stars you see at night (and the one you see by day) with your unaided eyes are just a small portion of our own immense galaxy. The good Earth is an infinitesimal speck of dust orbiting just one of about 200 billion stars making up our vast spiral home.

We cannot, on human terms, begin to appreciate the colossal size of even our Milky Way, at 100,000 light years in width. That’s how long it takes starlight from a star on one edge to reach an observer on the opposite side. Remember that each light year is 5.8 trillion miles. Remember that even 1 trillion, in terms of sheer size, is a number only a federal politician can appreciate. Earth is not quite 8,000 miles wide. Just to stretch 5 million miles, it would take 625 Earths lined up. Times that distance by a million and you get 5 trillion miles. That’s just one light year, and you are only a quarter of the way to the next star.

Yet the vast Milky Way’s nearest large neighbor, the Andromeda Galaxy, is 2.5 million light years from here, and that is considered close. That is roughly the distance of 25 Milky Ways end to end.

Our galactic neighborhood, the Local Group, is a nice piece of real estate. We have about 30 neighbors, and unlike many of us on Earth, we are getting to know who is next door. Astronomers have been sorting it out for hundreds of years, ever since early observations of what appeared to be wispy clouds among the nearby stars seen in the telescope gave way to realization of their true nature.

Do all our neighbors get along? We suppose so, except for the nasty detail that the Andromeda Galaxy is on a collision course with the Milk Way. Perhaps Canis Major, the Big Dog constellation, has been barking too much.

Actually, galaxies have a habit of smashing into each other and merging, sharing stars and spreading them out. Collision of galactic nebulosity, astronomers believe, lead to formation of new stars shining forth from the compressed gases.

Some of our Local Group neighbors are easy to see with binoculars. The Andromeda Galaxy (M31) is readily visible to unaided yes, appearing as a 4th magnitude fuzzy patch. Nearby in the sky is another neighbor, 7th magnitude galaxy M33. This is just below the normal threshold of visibility by unaided eyes. Both galaxies are found in the evening autumn sky.

The Milky Way and M31 have close to the same mass, and both have sundry satellite galaxies orbiting them. Astronomers have identified 13 satellites of the Milky Way; the two most easily seen, the Small and Large Magellanic Clouds, are only visible well south of the equator.

The outer reaches of the great Virgo Supercluster contain many galaxies you can see if you have access to a backyard telescope. You can find some with even a small telescope that has a 3-inch lens or main mirror, though larger telescopes show more. Sweeping through the constellation Virgo (for which the supercluster gets its name) and Leo and other areas, it is actually hard NOT to find a galaxy. They appear in the telescope as small, dim, fuzzy patches, some round, others oval or even needle-shaped. Many star atlases are available detailing positions of the galaxies among the faint foreground stars.

Without even leaving your yard, you can shift your telescope just a few inches as you scan with your eyepiece and travel from one of these galaxies to the next. You are covering millions of light years with this change of angle by merely pushing the telescope tube with your hand.

Last-quarter moon is on May 17, leading to new moon on May 24. That means dark, moon-less evening skies all week.

Send your comments, questions and reports to pbecker@wayneindependent.com. One reader from Delaware sent a nice report this past week of a bright meteor she saw while she was driving.

Keep looking up!