Skywatch: A great comet and a magnificent Milky Way

Over the last week, we’ve been entertained by a pre-Halloween visitor from the depths of our solar system. It’s Comet Tsuchinshan-Atlas, a ghostly dirty snowball of rock, gas, and dust partially melting before our very eyes. The solid 2 to 5 core is surrounded by a coma cloud of gas and dust more than 120,000 miles in diameter and a tail more than 16 million miles long being pushed away by solar wind.

It’s been easily visible to the naked eye in the western sky after evening twilight, even in skies plagued by light pollution. Sadly, though, it’s starting to fade as it heads away from our part of the solar system. Try taking a picture of the comet with your smartphone. After dark most cameras in smartphones automatically go to a one to three-second exposure allowing you to see more detail. Attached are two photos I took of Tsuchinshan-Atlas with my smartphone, as well as a shot from one of my astronomical cameras.

You and I are also a tiny, tiny part of something that’s beyond enormous! Our Earth, solar system and sun and up to 400 billion other stars, along with Lord knows how many other planets, are going around those other stars, orbiting around our home Milky Way Galaxy. To give you an idea of the vastness, one light year, which is the distance that a light beam would travel in a year, is just short of 6 trillion miles. That’s a distance so huge, it’s like going around the Earth’s equator 236 million times.

Our Milky Way is believed to be a spiral disk of stars with a big bulge in the middle. It spans well over 100,000 light years in diameter, but the thickness of most of the disk is skinny by comparison, around 1,000 light years. The central bulge of our home galaxy is about 12,000 light years in diameter.

Every time you look up on a clear night, even if you’re gazing in an area mired with light pollution, every one of the stars you see is a neighbor star in our home galaxy. Most of the stars you see at a glance are very close Milky Way neighbors. To get a better idea of the vastness of the Milky Way, get out into the countryside where the sky is pitch dark. Take binoculars or a small telescope with you to really make the night memorable.

As twilight fades, you can immediately tell how special the night sky can be when you’re away from city lighting. Lie back on a blanket or lawn chair so you can really take it all in. It’s especially thrilling this time of year because you can see that big river of stars that cuts the sky nearly in half. More formally known as the Milky Way band, that river stretches from the northeast horizon through the overhead zenith to the south-southwest horizon. You are looking edgewise into the plane of our Milky Way Galaxy, 1000 light-years thick. There are so many stars in our line of sight that it’s impossible to see most of them individually. Instead, they merge into one continuous glow.

The center bulge of the Milky Way is toward the southwestern horizon. It’s a little brighter than the rest of the band and would be much brighter if there weren’t enormous clouds of gas and dust in the way. Some astronomers think that if it weren’t for all of the astronomical crud in the way, that part of the sky would be as bright as the full moon all of the time.

Don’t forget to pack your binoculars when you embark on your galaxy-gazing adventure. They will open up a whole new world of celestial wonders for you to explore. There’s so much to discover from bright nebulae clouds where stars are born to dark rifts of hydrogen gas and clusters of young stars. And who knows, you might even catch a glimpse of a human-made satellite gliding across the heavens. So, lie back, roll your eyes across the sky, especially around the Milky Way band, and prepare for an unforgettable experience.

If you happen to be out galaxy-gazing this Monday, Oct. 21, you’ll notice a significant change in the sky after 9 p.m. That’s when the waning gibbous moon rises above the northeast horizon. Its light will whitewash the sky and pretty much shut down your galaxy-gazing, but the good news is that you’ll be treated to a great celestial conjunction between the moon and the bright planet Jupiter rising right behind it. I know you’ll like what you see!

Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and adventurepublications.net. Mike is available for private star parties. You can contact him at mikewlynch@comcast.net.