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07/21/2015 – Ephemeris – Vega, the brightest star of the Summer Triangle
Ephemeris for Tuesday, July 21st. Today the Sun will be up for 15 hours and 3 minutes, setting at 9:20. The Moon, 3 days before first quarter, will set at 12:01 tomorrow morning. Tomorrow the Sun will rise at 6:17.
The bright star high in the east is Vega, one of the stars of the Summer Triangle an informal constellation called an asterism. Vega belongs to the official constellation Lyra the harp, which includes a narrow parallelogram of stars to its south. Vega was regarded by astronomers as a standard calibration star. Though a first magnitude star, its actual magnitude is 0.03 and slightly variable. It is a type A0 (A-zero) pure white star, and is 25 light years away. Astronomers however got a shock in 1983 when calibrating the Infrared Astronomy Satellite (IRAS) on it: Vega showed an excess of Infrared radiation that means the star is orbited by a disk of dust, perhaps the beginnings of a planetary system. Due to the slow wobble of the earth’s axis Vega will be our pole star in 14 thousand years.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Summer Triangle. Created using Stellarium and The Gimp.
Magnified view of Lyra. Created using Stellarium.
Vega in the mid-infrared from the Spitzer Infrared Satellite. Credit: NASA/JPL-Caltech/University of Arizona
07/16/2015 – Ephemeris – The Summer Triangle is the sign of the season
Ephemeris for Thursday, July 16th. Today the Sun will be up for 15 hours and 12 minutes, setting at 9:25. The Moon, 1 day past new, will set at 9:32 this evening, and tomorrow the Sun will rise at 6:13.
We’re almost a month into summer, and the asterism or informal constellation called the Summer Triangle can be seen midway up the sky in the east as it gets dark. Highest of the three bright stars is Vega in the constellation Lyra the harp, whose body is seen in a narrow parallelogram nearby. The second star of the triangle is Deneb lower and left of Vega, It appears dimmer than Vega because it is by far the most distant of the three. The third star of the Summer Triangle is seen farther below and a right of Vega. It is Altair in Aquila the eagle, and the closest. Altair is 16.5 light years away, Vega is 27 light years while Deneb is so far away that it’s distance is in some doubt and may be 2,600 light years away.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Summer Triangle. Created using Stellarium.
07/09/2015 – Ephemeris – The first stars to appear at night
Ephemeris for Thursday, July 9th. Today the Sun will be up for 15 hours and 23 minutes, setting at 9:29. The Moon, 1 day past last quarter, will rise at 2:05 tomorrow morning, and tomorrow the Sun will rise at 6:07.
Let’s check out all the bright stars in the evening sky, as it gets dark tonight. Low in the west are the planets Venus and Jupiter. High in the west is the bright yellow-orange star Arcturus. In the northwest is the Big Dipper, whose curved handle points to Arcturus. Straightening that curve to a spike will point to Spica a blue-white star low in the southwest. The planet Saturn is located in the south. Below and left of it is the red star Antares which usually twinkles merrily. High in the east is the bright white star Vega. To its lower right is Altair, and to its lower left the star Deneb. Vega, Altair and Deneb make the Summer Triangle, whose rising in the east signals the coming of summer.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
I talked about seeing the first stars a month ago. It seems that in holding star parties this time of year we spend a lot of time watching the first stars appear. I wanted to discuss the Summer Triangle, but it wandered off to what you see above. I’ll get there next week, I promise.
The first stars and planets to appear. See if you can located them from the text. Created using Stellarium for about 10 p.m., July 9, 2015.
11/24/2014 – Ephemeris – The Summer Triangle is still with us
Ephemeris for Monday, November 24th. The sun will rise at 7:50. It’ll be up for 9 hours and 16 minutes, setting at 5:07. The moon, 2 days past new, will set at 7:29 this evening.
Well it’s almost Thanksgiving and about time that the Summer Triangle of bright summer stars finally set. Except it won’t go just yet. The stars Vega, Altair and Deneb are still hanging around in the west. The bright summer part of the Milky Way is gone. The constellations the three stars are in are Altair in Aquila the Eagle, now flying vertically up, Deneb in Cygnus the swan flying vertically down, and Vega in Lyre the harp, lying on its side. Altair the southernmost of these three will set first, later Vega will also set. What happens to Deneb depends on your location in the Interlochen Public Radio area. It you are north of Traverse City, Deneb will not actually set over Lake Michigan’s northern horizon.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Summer Triangle at 9 p.m. on November 24, 2014. Created using Stellarium.
Vega near its setting point at 11:07 p.m. p.m. on November 24, 2014. Created using Stellarium.
Deneb near its setting point at 5:05 a.m. p.m. on November 25, 2014. Created using Stellarium.
But will Deneb really set for Traverse City. Geometrically it will. However with a flat northern horizon looking northward over the bays to a clean Lake Michigan horizon, atmospheric refraction will bend the light from Deneb making it appear higher in the sky than it really is, so it won’t actually set. On the other side atmospheric extinction, the dimming of stars close to the horizon due to the filtering effect of looking through so much atmosphere would make Deneb impossible to see without a telescope. It might be an interesting challenge to spot.
08/21/2014 – Ephemeris – What do a dolphin, an arrow and a coffin have in common?
Ephemeris for Thursday, August 21st. The sun rises at 6:52. It’ll be up for 13 hours and 46 minutes, setting at 8:38. The moon, half way from last quarter to new, will rise at 4:12 tomorrow morning.
Located below the eastern edge of the Summer Triangle of three of the brightest stars in the sky, which is high in the southeast in the sky at 10 p.m., is the tiny constellation of Delphinus the dolphin. Delphinus’ 6 stars in a small parallelogram with a tail, really does look like a dolphin leaping out of the water. The parallelogram itself has the name Job’s Coffin. The origin of this asterism or informal constellation is unknown. Of the dolphin itself: the ancient Greeks appreciated this aquatic mammal as we do, and told stories of dolphins rescuing shipwrecked sailors. There’s another tiny and slender constellation to the right of Delphinus called Sagitta the arrow, which is said to represent Cupid’s dart.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Delphinus, Sagitta and the Coat hanger. Diagram created using Stellarium.
The Coat hanger is strictly a binocular asterism. However it was discovered by the great Arabian astronomer Al Sufi inn the 10th century, and is currently designated Collinder 399. It is actually a random pattern of unrelated stars.
Delphinus and Sagitta images along with the stars and constellations of the Summer Triangle. Created using Stellarium.
07/24/2014 – Ephemeris – A look at Altair the third star of the Summer Triangle
Ephemeris for Thursday, July 24th. The sun rises at 6:20. It’ll be up for 14 hours and 56 minutes, setting at 9:17. The moon, 2 days before new, will rise at 5:21 tomorrow morning.
The Summer Triangle Is high in the east to southeast sky in the evening. The southernmost star of the Summer Triangle is Altair, in the southeast. Altair is the closest of the three stars at a distance of 16.7 light years away. One light year is nearly 6 trillion miles, that’s 6 followed by 12 zeros. Altair is nearly 11 times the brightness of the sun. If seen at Altair’s distance, the sun would only be as bright as one of the two stars that flank it in our sky. What is rather different about Altair is its rapid rotation. While it’s almost twice the sun’s diameter, it rotates once in only 9 hours, and would show a decidedly squashed appearance if seen close up. Our sun’s a slow poke, taking nearly a month to rotate just once.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Deneb with the other stars and constellations in the Summer Triangle. Created using Stellarium.
False-color image of the rapidly rotating star Altair, made with the MIRC imager on the CHARA array on Mt. Wilson. Credit: Ming Zhao, University of Michigan
07/18/2014 – Ephemeris – Deneb is the brightest star of the Summer Triangle… Really
Ephemeris for Friday, July 18th. Today the sun will be up for 15 hours and 8 minutes, setting at 9:22. The moon, at last quarter today, will rise at 12:58 tomorrow morning. Tomorrow the sun will rise at 6:15.
At 11 this evening the bright star Deneb in Cygnus the swan will be moderately high in the east northeast. Deneb is the dimmest star of the summer triangle. Of the other stars of the triangle, Vega is nearly overhead, and Altair to the southeast. While Deneb’s apparent magnitude, or brightness as seen from Earth, makes it the dimmest of the three bright stars, Deneb has a vast distance of possibly 1,550 light years. If brought as close as Vega, Deneb would be several times brighter than Venus. For all this it is only 13-20 times the mass of the sun. It will have an extremely short life and will explode, go supernova, in perhaps a few million years. Closer to home, check out the Sun at Kingsley Heritage Days This Saturday and Sunday.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Deneb and the Northern Cross section of Cygnus the swan. Created using Stellarium.
One of my old photographs of Deneb and the North American Nebula digitized from a slide.
The North American Nebula, visible as a faint smudge in binoculars or the naked eye may be ionized and illuminated by Deneb. It’s distance appears to be comparable to that of Deneb.
You may note that previous postings about Deneb over the years have given different distances of Deneb. That just denotes how difficult it is to pin down its distance.
06/23/2014 – Ephemeris – It’s summer, so where is the Summer Triangle?
Ephemeris for Monday, June 23rd. Today the sun will be up for 15 hours and 33 minutes, setting at 9:31. The moon, half way from last quarter to new, will rise at 4:09 tomorrow morning. Tomorrow the sun will rise at 5:58.
Now that it’s summer it’s time to look for the Summer Triangle in the sky. It’s seen rising in the east as it gets dark. Highest of the three bright stars is Vega in the constellation Lyra the harp, whose body is seen in a narrow parallelogram nearby. The second star of the triangle is Deneb lower and left of Vega, It appears dimmer than Vega because it is by far the most distant of the three. The third star of the Summer Triangle is seen farther below and a right of Vega. It is Altair in Aquila the eagle, and the closest. Altair is 16.5 light years away, Vega is 27 light years while Deneb actually one of the brighter stars known, is a whopping 2600 light years away, give or take. It’s distance is not well-known. (24 08:54 Venus 1.3°N of Moon)
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Summer Triangle. Created using Stellarium and The Gimp.
07/29/2013 – Ephemeris – The constellation Aquila the eagle
Ephemeris for Monday, July 29th. The sun rises at 6:25. It’ll be up for 14 hours and 45 minutes, setting at 9:11. The moon, at last quarter today, will rise at 12:46 tomorrow morning.
Aquila the eagle is a constellation that lies in the Milky Way. It’s in the southeastern sky as it gets dark. Its brightest star, Altair is one of the stars of the Summer Triangle, a group of three bright stars seen now in the eastern sky in the evening. Altair, in the head of the eagle, is flanked by two slightly dimmer stars, the shoulders of the eagle. The eagle is flying northeastward through the Milky Way. Its wings are seen in the wing tip stars. A curved group of stars to the lower right of Altair is its tail. Within Aquila the Milky Way shows many dark clouds as part of the Great Rift that splits it here. The other summer bird is Cygnus the swan, above and left of Aquila, flying in the opposite direction, southward.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Aquila with the other constellations in the Summer Triangle. Created using Stellarium.
06/26/2013 – Ephemeris – Latest sunset and the Summer Triangle
Ephemeris for Thursday, June 27th. Today the sun will be up for 15 hours and 32 minutes, setting at 9:31. The moon, 3 days before last quarter, will rise at 12:14 tomorrow morning. Tomorrow the sun will rise at 5:59.
Last night we had the latest sunset of the year. The sun is really beginning to head south. Other than the sunrise and sunset numbers, we’ll begin to notice it for real in a few weeks. At first that realization strikes me a sad note that summer is beginning to end. However the astronomer in me realizes that means more night-time hours, and that the summer Milky Way is coming. Of the three bright stars of the Summer Triangle overhead and in the east, two of its stars are in the milky band. They are Deneb to the north and Altair to the south. Vega, closest to the zenith is not in the band. Actually all the stars we see with the naked eye or small telescopes belong to the Milky Way galaxy.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Summer Triangle at 11 p.m. Created using Stellaruim and The Gimp.
Bob Moler's Ephemeris Blog 