Milky Way Mysteries Mapped

 

The Hubble Space Telescope snapped this finely detailed image of the beautiful spiral galaxy NGC 6384, an island of stars thought to resemble our own Milky Way galaxy. Credit: ESA/NASA

Ever look up and wonder how many stars are out there in the night sky, and where did all these stars come from?

Now astronomers have actually counted every single twinkling star visible from the night skies of Earth—and the number is astounding. Using the giant 8.2-foot (2.5-meter) glass eye of the Isaac Newton Telescope in the Canary Islands, astronomers assembled their chart, which includes an astounding 219 million individual stars.

Assembled over ten years of observations, the titanic new catalog plots the faintest stars down to the 20th magnitude, which is one million times fainter than can be seen with the unaided human eye.

This new stellar map plots 219 million stars as seen in the skies from Earth - all of which belong to the Milky Way galaxy. Credit: Hywel Farnhill, University of Hertfordshire.
This new stellar map plots 219 million stars in the Milky Way galaxy, as seen from Earth. Credit: Hywel Farnhill, University of Hertfordshire

The image above is actually a small section of this new galactic survey. The researchers, led by Geert Barentsen of the University of Hertfordshire in the United Kingdom, are hoping it will help us better understand the complex structure of our home galaxy.

Also worth noting is that this catalog represents only a limited view from Earth. Since our planet is embedded within one of the outer arms of the Milky Way, there are tens of thousands of light-years of gas and dust that prevent us from seeing the tens of billions more stars on the other side of the galaxy.

Galactic Collisions

Meanwhile, another new discovery announced this week suggests that the Milky Way, and all the other spiral-type galaxies in the universe, may have their origins in ancient collisions between smaller galaxies.

This 20016 Hubble Space Telescope image of the Antennae galaxies 64 million light years fro Earth is the sharpest yet of this merging pair of galaxies.  Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration
This 2006 Hubble Space Telescope image of the Antennae galaxies, 64 million light-years from Earth, is the sharpest yet of this merging pair of galaxies. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration

Until now, a leading theory around since the early 1970s had suggested that merging galaxies formed into elliptical shapes as they violently cannibalized themselves.

But now new supercomputer simulations, combined with observations of 37 galaxies caught in the act of merging, clearly show gas clouds gathering into distinct disk shapes—an early sign of disk galaxy formation.

“For the first time there is observational evidence for merging galaxies that could result in disc galaxies,” said co-author Junko Ueda, an astronomer with the Japan Society for the Promotion of Science, in a press statement. “This is a large and unexpected step towards understanding the mystery of the birth of disc galaxies.”

Go outside of the city limits any clear summer night, and you can glimpse our home galaxy stretched out above your head. Appearing as a glowing band of light, the Milky Way galaxy reaches across some 100,000 light-years of the sky and takes on the shape of a giant pinwheel with spiral arms flowing outward.

Current estimates are that the Milky Way may be home to as many as 300 billion suns.

And now this study suggests that most galaxy collisions in the nearby universe, ones within 40 to 600 million light-years from Earth, result in so-called disk galaxies that includes spirals like our own Milky Way.

See for Yourself

September is a great month to get acquainted with our own home city of stars, the Milky Way. The night sky is perfectly oriented in the Northern Hemisphere for evening views of the galaxy, especially its downtown core.

To get the best views, pass beyond city limits away from the lights, and head straight into the countryside.

Looking toward the low southwestern sky, the constellation Sagittarius points to the galactic hub, which lies some 28,000 light-years away from Earth.

The brightest star in the low southwestern evening sky is red-colored Antares, and due east of it you will find an easy-to-spot grouping of stars in the shape of a teapot—this marks the heart of Sagittarius. For even the seasoned stargazer, tracing out the figure of a centaur takes some imagination, while the familiar form of the teapot is rather easy to see.

This sky chart shows the Milky Way rising from Sagittarius constellation's Teapot as seen in the low southwestern evening sky this week. Credit: SkySafari
This sky chart shows the Milky Way rising from the “teapot” in the constellation Sagittarius, as seen in the low southwestern evening sky this week. Credit: SkySafari

The Milky Way appears like steam rising from its spout. And when using binoculars, this whole area is rich with stellar gems to discover.

Some of the main attractions in Sagittarius are the numerous colorful gas clouds, or giant star factories, scattered within one of the spiral arms of the Milky Way. These nebulae are home to hundreds of newborn stars, still wrapped inside their hot gaseous blankets.

Enjoy your tour of our home galaxy!

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Changing Planet

Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.