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Posts Tagged ‘Big Dipper’

04/09/2021 – Ephemeris – Follow the arc to Arcturus

April 9, 2021 Comments off

This is Bob Moler with Ephemeris for Friday, April 9th. Today the Sun will be up for 13 hours and 12 minutes, setting at 8:20, and it will rise tomorrow at 7:06. The Moon, 2 days before new, will rise at 6:57 tomorrow morning.

The fourth or fifth brightest night-time star, depending on whose list you see, is now up in the east in the evening. It is Arcturus, a bright star with an orange hue. It can be found otherwise by finding the Big Dipper and tracing out and extending the curve of the handle and “Follow the arc of the handle to Arcturus”, to remember the name of the star and how to find it. Arcturus is about 37 light years from us and is moving quite rapidly across the sky, compared to most stars, though one would not notice it to the naked eye in one’s lifetime. Arcturus is slightly more massive than our Sun, and about 7 billion years old, and is entering its red giant stage of life after using all the hydrogen fuel in its core. Our Sun, being slightly less massive will survive on hydrogen a bit longer.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

How to find Arcturus
How to find Arcturus. In the early spring Arcturus is low in the east in the evening. The Big Dipper is high in the northeast standing on its handle. To find and remember the name of this star simply follow the arc of the handle to Arcturus. Created using Stellarium and GIMP.

I’ll be talking more about Arcturus and the constellation it’s in Boötes the herdsman, a kite shaped constellation that’s currently laying on its side. He’s not herding, but chasing the Great Bear. But that’s another story.

04/08/2021 – Ephemeris – Ursa Major, the Great Bear

April 8, 2021 Comments off

This is Bob Moler with Ephemeris for Thursday, April 8th. Today the Sun will be up for 13 hours and 9 minutes, setting at 8:19, and it will rise tomorrow at 7:08. The Moon, 3 days before new, will rise at 6:37 tomorrow morning. | The constellation of Ursa Major, or great bear was well-known to the ancient Greeks and Native Americans. Today, however, many of us can recognize only part of it as the Big Dipper. The whole bear can be easily seen only in a dark sky. At 10 pm it’s high in the northeast with feet to the south. The stars in front of the bowl are the front part of his body and head. The bowl of the Big Dipper is his rump, and the handle his long tail. The Native Americans, saw those three stars as three hunters following the bear. The Anishinaabe tribes of the Great Lakes region saw it as the Fisher or Ojiig, who brought summer to the Earth. These stars here do make a convincing bear, except for the tail, when seen on a dark night. However, the weasel-like Fisher fits the stars completely.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Ursa Major andOjiig animation
An animation to visualize the Great Bear, Ursa Major and the Fisher, Ojiig, from the stars of and around the Big Dipper. Created using Stellarium.

03/11/2021 – Ephemeris – The Guardian of the Bear is rising

March 11, 2021 Comments off

This is Ephemeris for Thursday, March 11th. Today the Sun will be up for 11 hours and 42 minutes, setting at 6:44, and it will rise tomorrow at 7:00. The Moon, 2 days before new, will rise at 7:09 tomorrow morning.

The brightest star of spring is Arcturus which will be visible by 9 pm low in the east-northeast. Arcturus can most famously be found by following the arc of the handle of the Big Dipper, which resides fairly high in the northeastern sky to it. “Follow the arc of the handle to Arcturus.” It’s the fourth or fifth brightest star in the sky, depending on the list. It was regarded as the “Guardian of the Bear”, meaning the Great Bear, Ursa Major, of which the Big Dipper is its hind end. Apparently it’s guarding its rear. Arcturus will stay in our evening sky until the end of summer and has a fascinating story of its own aside from its ancient mythology, which I’ll talk about when it’s higher in the sky. It’s located at the base of a kite shaped constellation called Boötes, which is now horizontal and too close to the horizon to be appreciated.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Arcturus rising finder animation

Arcturus rising finder animation for 9 pm tonight, March 11, 2021. Created using Stellarium and GIMP.

01/18/2021 – Ephemeris – The Drinking Gourd

January 18, 2021 Comments off

This is Bob Moler with Ephemeris for Martin Luther King Jr. Day, Monday, January 18th. Today the Sun will be up for 9 hours and 18 minutes, setting at 5:32, and it will rise tomorrow at 8:13. The Moon, 2 days before first quarter, will set at 11:34 this evening.

This day is set aside to honor the Reverend Dr. Martin Luther King Jr. who gave his life for the struggle for equality for blacks and other minorities and to end segregation. A struggle that continues to this day. In the decades before the Civil War runaway slaves would travel, often at night, northward from the slave states of the south to the northern free states and Canada over the metaphorical Underground Railroad following the Drinking Gourd, the Big Dipper as their compass. Over the last several millennia the Great Bear, Ursa Major has been that northward pointer. For much of that time the North Pole of the sky had been passing near the handle of the Big Dipper or bear’s tail.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

An animation showing the Big Dipper, also known as the Drinking Gourd pointing to Polaris, the North Star which is just about due north. This is for 9 pm January 18th, about 3 1/2 hours after sunset. Created using Stellarium with additional annotations.

06/26/2020 – Ephemeris – The stars known as the Horse and Rider

June 26, 2020 Comments off

Jun 26. This is Bob Moler with Ephemeris for Friday, June 26th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:32, and it will rise tomorrow at 5:59. The Moon, 2 days before first quarter, will set at 1:28 tomorrow morning.

The most interesting star in the Big Dipper is Mizar and its dim companion Alcor. It is the second star from the end of the handle, where the bend in the handle takes place. Folks with good vision can see the dimmer star right next to Mizar. In ancient times it was used as an eye test for visual acuity for warriors. As such it was known as the “Horse and the Rider”. Mizar is second magnitude, in the second rank of star brightness invented by the Greek astronomer Hipparchus in the 2nd century BC. He ranked stars in 6 classes, from first magnitude for the brightest to 6th for the dimmest visible to the naked eye. Alcor comes in at 4th magnitude. It does suffer a bit by being very close to Mizar which is 6 times brighter.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Mizar finder animation

Mizar finder animation for the Big Dipper’s orientation in late June at 11 pm where I live or an hour and a half after sunset. Created using Stellarium and GIMP.

Mizar and Alcor as they would appear in a telescope

Mizar and Alcor as they might appear in a telescope. Mizar is a binary star in a telescope. The other star in the field is apparently a background star. The brighter star of Mizar is Mizar A, while the dimmer is Mizar B. It turns out that Mizar A and B plus Alcor are all spectroscopic binaries, meaning the companion stars are too close to resolve in telescopes, but whose motion shows up in the spectra of the stars. Mizar and Alcor are around 80 light years away. Created using Stellarium.

06/25/2020 – Ephemeris – The bright star Spica

June 25, 2020 Comments off

This is Ephemeris for Thursday, June 25th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:32, and it will rise tomorrow at 5:58. The Moon, 3 days before first quarter, will set at 12:59 tomorrow morning.

Low in the southwest at 11 p.m. is the bright star Spica which can be found from all the way back overhead to the Big Dipper. Follow the arc of the handle of the Big Dipper to the bright star Arcturus high in the southwest. Then straighten the curve of the arc to a straight spike which points to Spica. Arcturus is much brighter than Spica and has an orange tint to Spica’s bluish hue. In fact Spica is the bluest of the 21 first magnitude stars. That means that it is hot. Actually Spica is really two blue stars orbiting each other in 4 days. Spica is 250 light years away, which is reasonably close. Spica was an important star to the ancient Greeks. One temple was built, and aligned to its setting point.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Spica finder chart

Spica finder chart using my LookingUp program fo 11 p.m. tonight June 25.

06/23/2020 – Ephemeris – Arcturus: a look at the Sun’s future

June 23, 2020 Comments off

This is Ephemeris for Tuesday, June 23rd. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32, and it will rise tomorrow at 5:58. The Moon, 2 days past new, will set at 11:49 this evening.

Arcturus, a red giant star is about two thirds the way up the sky in the southwest at 11 p.m. It’s one of the earliest stars to appear in twilight, being nearly tied in brightness with Vega, a white star nearly as high in the east. A pointer to Arcturus is the handle of the Big Dipper, following the arc of the handle to Arcturus. Though only 37 light years away, it’s not from around here. It’s passing through the galactic disk from north to south. Arcturus is about 7 billion years old, and is about 8% more massive than our Sun. It appears to be starting its red giant phase, after running out of hydrogen to fuse to helium in its core and is beginning to fuse helium. It’s a preview of coming attractions for our Sun when it gets that old.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Arcturus finder diagram

Arcturus is easy to find. It’s the brightest star in the southwest in the evening. This is 11 pm tonight June 23, 2020. Note the Big Dipper and its handle to the upper right. Created using Stellarium.

05/15/2020 – Ephemeris – Virgo and its cluster of galaxies

May 15, 2020 Comments off

This is Ephemeris for Friday, May 15th. Today the Sun will be up for 14 hours and 50 minutes, setting at 9:04, and it will rise tomorrow at 6:12. The Moon, 1 day past last quarter, will rise at 4:01 tomorrow morning.

One of the large constellations we see in the south at 11 p.m. can be found using the Big Dipper overhead, follow the arc of the handle to the bright star Arcturus, the straighten the arc to a spike to reach Spica, a bright blue-white star in the south. Spica is the brightest star in the constellation Virgo the virgin. She represents the goddess of the harvest, Virgo is holding a sheaf of wheat in depictions of her, and Spica is placed at the head of the sheaf. In the space between Spica and Leo the lion to her upper right is, a great cluster of thousands of galaxies just below naked eye visibility. The Virgo Cluster. Inside that cluster is galaxy M87 in whose center lies a black hole with the mass of 6.5 billion suns that was imaged last year. The center of the cluster is at about 54 million light years away.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Finding Spica

Spica finder animation . Click on the image to enlarge. Created using Stellarium and GIMP.

Virgo Cluster

Some of the brighter members of the Virgo Cluster (of galaxies) as red ovals. The galaxies marked with an ‘M’ number are part of Charles Messier’s catalog. It took a telescope of 8 inch diameter for me to spot them. Someone with better vision, like Messier himself can spot them with a smaller telescope. M53 and the object next to it are globular star clusters in the outer reaches of our galaxy. Created using Cartes du Ciel (Sky Charts).

Markarian Chain of galaxies

Markarian Chain of galaxies within the Virgo Cluster by Scott Anttila.

Black hole in M87

The first image of the black hole in M87. Credit Event Horizon Telescope.

 

 

04/24/2020 – Ephemeris – The Big Dipper can be used to point to other stars and constellations

April 24, 2020 Comments off

This is Bob Moler with Ephemeris for Arbor Day, Friday, April 24th. Today the Sun will be up for 13 hours and 57 minutes, setting at 8:39, and it will rise tomorrow at 6:41. The Moon, 2 days past new, will set at 10:21 this evening.

The Big Dipper can be used to point to other stars and constellations. Right now the Big Dipper is nearly overhead. The front bowl stars point to Polaris, the North Star which never seems to move in the sky. The handle can be used to find two stars. First follow the arc of the handle away from the bowl to find the fourth brightest night-time star Arcturus in the base of the kite shaped constellation of Boötes. Straighten the arc to a spike and continue to the south and you will come to the bright blue-white star Spica in Virgo the virgin. You can remember these stars with the phrase “Follow the arc of the handle to Arcturus and then spike to Spica” or if you prefer the alternate pronunciation of the latter star “Speak to Speeka”.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Finding stars and constellations using the Big Dipper

Finding stars and constellations using the Big Dipper. Click on the image to enlarge. Created using my LookingUp program for Windows.

04/13/2020 – Ephemeris – The story of Callisto and Arcas or Ursa Major and Boötes

April 13, 2020 Comments off

This is Ephemeris for Monday, April 13th. Today the Sun will be up for 13 hours and 25 minutes, setting at 8:26, and it will rise tomorrow at 6:59. The Moon, 1 day before last quarter, will rise at 3:09 tomorrow morning.

Appearing mid way up the sky in the east at 10 p.m. is the kite shaped constellation of Boötes the herdsman. The bright star Arcturus is at the bottom-right of the kite, pointed to by the arc of the handle of the Big Dipper, above it. In one Greek myth Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young lady who had the misfortune of being loved by Zeus the chief of the Greek gods. Zeus’ wife Hera, found out about the affair, and since she couldn’t punish Zeus, turned the poor woman into an ugly bear. Arcas, unaware of the events surrounding his mother’s disappearance in his youth was about to kill the bear when Zeus intervened and placed them both in the sky to save her. To this day Boötes continues to chase the Great Bear, Ursa Major, around the pole of the sky each night.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Arcas and Callisto

Bootes and Ursa Major aka Arcas chasing Callisto around the pole of the sky. Created using Stellarium.

Arcas and Callisto woodcut

Arcas about to slay the bear by the 17th century artist Baur. Source: University of Virginia Electronic Text Center