The Northern Cross: Find the backbone of the Milky Way

The constellation Cygnus represents a graceful swan. But many also see it as a cross, and so these stars have become known as an asterism called the Northern Cross. The entire pattern fits inside a larger asterism created by the 3 bright stars Vega, Deneb and Altair: the famous Summer Triangle. Chart via EarthSky.

How to find the Northern Cross

The Northern Cross is a clipped version of the constellation Cygnus the Swan. It’s an asterism, or pattern of stars that’s not a recognized constellation. It lies embedded within another much larger asterism: the Summer Triangle. You’ve got to have a dark sky and a good imagination to see a swan in the stars of Cygnus. But the Northern Cross is easy to see, even if your sky is less than pristine.

Here’s step one for finding the Northern Cross. Look for the asterism’s most brilliant star, Deneb. Deneb marks the top of the Northern Cross. It’s also well known as one of the three bright stars of the Summer Triangle, along with Vega and Altair.

Now, look for a bright star roughly halfway between Altair and Vega and slightly offset toward Deneb. That’ll be Albireo. Although only a modestly bright star, Albireo is easy to see on a clear, dark night. There are no similarly bright stars near Albireo, so it’s fairly easy to find.

Once you locate Deneb and Albireo, you’re halfway to piecing together the Northern Cross. All you need now is the crossbar, which most people see as three moderately bright stars. As you can see in the illustration above, these three stars extend about halfway out into the wings of Cygnus the Swan.

Backbone of the Milky Way

When you look at the Northern Cross, you’re looking directly into the flat disk of our galaxy, the Milky Way. In fact, the galactic plane (equator) runs right through the Northern Cross, encircling the sky above and below the horizon. So the Northern Cross serves as a great signpost for a view of our home galaxy. In a dark sky on a northern summer evening, the Milky Way appears as a luminescent river of haze passing directly along the length of the Northern Cross. You can see this hazy band stretching all the way across the sky on late July and August evenings.

You probably know that this haze is actually countless stars. So, these stars will emerge beautifully through binoculars, as will the star fields, star clusters and nebulae that abound within the disk of the Milky Way!

View at EarthSky Community Photos. | Andy Dungan near Cotopaxi, Colorado, captured this image of the Sadr Star Region in Cygnus the Swan on May 25, 2023. The bright central star is Sadr, the star at the intersection of the Northern Cross. Andy wrote: “Cygnus is full of fun stuff to shoot. I had no idea how large the area surrounding the central star of Cygnus (Sadr or Gamma Cygni) was. The large area around Sadr is identified as the Sadr Region or the Butterfly Nebula, IC 1318.” Thank you, Andy!

Northern Cross as a marker of seasons

As seen from mid-northern latitudes, the Northern Cross is out for at least part of the night all year around. Plus, it’s out all night in summer. On Northern Hemisphere summer nights, the Northern Cross shines in the east at nightfall, sweeps high overhead after midnight, and swings to the west by daybreak. When you see the Northern Cross in the east on summer evenings, it’s sideways to the horizon.

By the time northern autumn arrives, the Northern Cross is still out from nightfall until midnight, but it appears high overhead in the evening and sets in the northwest after midnight.

And when winter comes, the Northern Cross is standing upright over your northwest horizon before midnight.

The constellation Cygnus appears in the lighter area. Its primary stars make the distinct pattern of the Northern Cross. On the right of this chart you see the constellation Lyra the Harp with its brightest star, Vega. To use this chart on July or August evenings – when Cygnus is in the east – give the chart a single rotation to the left. Image via IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)/ Wikimedia Commons.

Bottom line: The Northern Cross is an asterism – or recognizable pattern of stars – within the constellation Cygnus the Swan. Here’s how to find it in your sky.

The post The Northern Cross: Find the backbone of the Milky Way first appeared on EarthSky.

from EarthSky https://ift.tt/yR27TMZ

The constellation Cygnus represents a graceful swan. But many also see it as a cross, and so these stars have become known as an asterism called the Northern Cross. The entire pattern fits inside a larger asterism created by the 3 bright stars Vega, Deneb and Altair: the famous Summer Triangle. Chart via EarthSky.

How to find the Northern Cross

The Northern Cross is a clipped version of the constellation Cygnus the Swan. It’s an asterism, or pattern of stars that’s not a recognized constellation. It lies embedded within another much larger asterism: the Summer Triangle. You’ve got to have a dark sky and a good imagination to see a swan in the stars of Cygnus. But the Northern Cross is easy to see, even if your sky is less than pristine.

Here’s step one for finding the Northern Cross. Look for the asterism’s most brilliant star, Deneb. Deneb marks the top of the Northern Cross. It’s also well known as one of the three bright stars of the Summer Triangle, along with Vega and Altair.

Now, look for a bright star roughly halfway between Altair and Vega and slightly offset toward Deneb. That’ll be Albireo. Although only a modestly bright star, Albireo is easy to see on a clear, dark night. There are no similarly bright stars near Albireo, so it’s fairly easy to find.

Once you locate Deneb and Albireo, you’re halfway to piecing together the Northern Cross. All you need now is the crossbar, which most people see as three moderately bright stars. As you can see in the illustration above, these three stars extend about halfway out into the wings of Cygnus the Swan.

Backbone of the Milky Way

When you look at the Northern Cross, you’re looking directly into the flat disk of our galaxy, the Milky Way. In fact, the galactic plane (equator) runs right through the Northern Cross, encircling the sky above and below the horizon. So the Northern Cross serves as a great signpost for a view of our home galaxy. In a dark sky on a northern summer evening, the Milky Way appears as a luminescent river of haze passing directly along the length of the Northern Cross. You can see this hazy band stretching all the way across the sky on late July and August evenings.

You probably know that this haze is actually countless stars. So, these stars will emerge beautifully through binoculars, as will the star fields, star clusters and nebulae that abound within the disk of the Milky Way!

View at EarthSky Community Photos. | Andy Dungan near Cotopaxi, Colorado, captured this image of the Sadr Star Region in Cygnus the Swan on May 25, 2023. The bright central star is Sadr, the star at the intersection of the Northern Cross. Andy wrote: “Cygnus is full of fun stuff to shoot. I had no idea how large the area surrounding the central star of Cygnus (Sadr or Gamma Cygni) was. The large area around Sadr is identified as the Sadr Region or the Butterfly Nebula, IC 1318.” Thank you, Andy!

Northern Cross as a marker of seasons

As seen from mid-northern latitudes, the Northern Cross is out for at least part of the night all year around. Plus, it’s out all night in summer. On Northern Hemisphere summer nights, the Northern Cross shines in the east at nightfall, sweeps high overhead after midnight, and swings to the west by daybreak. When you see the Northern Cross in the east on summer evenings, it’s sideways to the horizon.

By the time northern autumn arrives, the Northern Cross is still out from nightfall until midnight, but it appears high overhead in the evening and sets in the northwest after midnight.

And when winter comes, the Northern Cross is standing upright over your northwest horizon before midnight.

The constellation Cygnus appears in the lighter area. Its primary stars make the distinct pattern of the Northern Cross. On the right of this chart you see the constellation Lyra the Harp with its brightest star, Vega. To use this chart on July or August evenings – when Cygnus is in the east – give the chart a single rotation to the left. Image via IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)/ Wikimedia Commons.

Bottom line: The Northern Cross is an asterism – or recognizable pattern of stars – within the constellation Cygnus the Swan. Here’s how to find it in your sky.

The post The Northern Cross: Find the backbone of the Milky Way first appeared on EarthSky.

from EarthSky https://ift.tt/yR27TMZ