Archive

Archive for the ‘Asterism’ Category

08/19/2022 – Ephemeris – Finding the small constellations near the Summer Triangle

August 19, 2022 Comments off

This is Ephemeris for Friday, August 19th. Today the Sun will be up for 13 hours and 52 minutes, setting at 8:41, and it will rise tomorrow at 6:51. The Moon, at last quarter today, will rise at 12:32 tomorrow morning.

I’ve already talked about the three constellations whose bright stars mark the Summer Triangle: Vega in Lyra the harp, Deneb in Cygnus the swan, and Altair in Aquila the eagle. There are two small constellations near the south end of the triangle near Altair. These are Delphinus the dolphin and Sagitta the arrow. Delphinus is easily spotted, as it’s five or six stars appear as a tiny dolphin leaping out of the water. Sagitta appears as a very short arrow. An interesting sight can be spotted in binoculars near the tail end of Sagitta. It’s 7 stars in a nearly straight line, with a hook of four stars below the center of the line. It’s called The Coathanger. It’s even better if seen in a finder telescope, which inverts the image.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Finding the small constellations of Delphinus the dolphin and Sagitta the arrow among the stars and constellations of the Summer Triangle. Created using Stellarium and GIMP.

Coathanger finder

How to locate the binocular asterism of the Coathanger. It is also known as Collinder 399, Brocchi’s Cluster and Al Sufi’s Cluster. It’s not a real star cluster, but a random arrangement of stars at various distances, that from the solar system make a distinctive pattern.

07/15/2022 – Ephemeris – How to find the constellation of Cygnus the swan

July 15, 2022 Comments off

This is Ephemeris for Friday, July 15th. Today the Sun will be up for 15 hours and 14 minutes, setting at 9:25, and it will rise tomorrow at 6:12. The Moon, 2 days past full, will rise at 11:23 this evening.

Located fairly high in the east at 11 p.m. is the constellation of Cygnus the swan, flying south through the Milky Way. It is also called the Northern Cross. At the left, the tail of the swan or the head of the cross is the bright star Deneb, one of the stars of the Summer Triangle. The next star right is Sadr the intersection of the body and the wings of the swan seen in flight, or the intersection of the two pieces of the cross. There are two or three stars farther to the right that delineate the swan’s long neck or upright of the cross, that ends with the star Alberio in the beak of the swan or foot of the cross. The crosspiece of the cross extends to the stars on either side of the intersection star Sadr, while the swan’s wings extend to a couple more stars each.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Cygnus finder animation

Animated Cygnus finder chart. Included also are, beside Deneb, the other stars of the Summer Triangle: Vega and Altair and their constellations Lyra the harp and Aquila. See if you can find them. Created using Stellarium.

07/14/2022 – Ephemeris – The dimmest Summer Triangle star is actually the brightest

July 14, 2022 Comments off

This is Ephemeris for Thursday, July 14th. Today the Sun will be up for 15 hours and 15 minutes, setting at 9:26, and it will rise tomorrow at 6:11. The Moon, 1 day past full, will rise at 10:49 this evening.

This evening, when it gets dark enough, the bright star Deneb in Cygnus the swan will be high in the east-northeast. I’ll cover Cygnus tomorrow when the sky is darker. Deneb is the dimmest star of the summer triangle. Of the other stars of the triangle, Vega is higher in the east, while Altair is lower in the southeast. Deneb’s apparent magnitude, or brightness as seen from Earth, makes it the dimmest of the three bright stars. That’s because of its vast distance of maybe 1,550 light years, 57 times the distance of Vega. If brought as close as Vega, Deneb would be as bright, at least, as the first quarter moon. It is possibly as bright as 196 thousand Suns; and it’s a huge star, possibly as large in diameter as the orbit of the Earth. For all this, it is only 23 or so times the mass of the Sun.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

The Summer Triangle July 5, 2012 at 11 p.m. Created using Stellaruim and The Gimp.

The Summer Triangle. Created using Stellarium and The Gimp.

If you put Deneb in the search box, you will find that the content of the posts, over the years, about the star are nearly identical. However, the distance estimates vary widely. It is too far away for trigonometric parallax measurements by earth based telescopes. Though in the range of ESA’s Hipparcos and Gaia satellites, it is too bright. So other less accurate measurements are used. I don’t think it involves coin flipping. The assumed distance also affects estimates of luminosity, and mass.

06/27/2022 – Ephemeris – Finding the Summer Triangle

June 27, 2022 Comments off

This is Ephemeris for Monday, June 27th. 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, 1 day before new, will rise at 5:13 tomorrow morning.

We’re nearly a week into summer, and the asterism or informal constellation called the Summer Triangle can be 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, in Cygnus the swan, 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 may be a whopping 2,600 light years away. One light year is 6 trillion miles (9 trillion kilometers).

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Summer Triangle finder animation

The Summer Triangle finder animation showing first the unlabeled sky, Then the Summer Triangle with the stars labeled, then the constellations of those stars. Created using Stellarium and GIMP.

03/21/2022 – Ephemeris – Finding the celestial lion

March 21, 2022 Comments off

This is Ephemeris for Monday, March 21st. Today the Sun will be up for 12 hours and 12 minutes, setting at 7:56, and it will rise tomorrow at 7:42. The Moon, 3 days past full, will rise at 12:15 tomorrow morning.

At 10 p.m. the spring constellation of Leo the lion will be fairly high in the southeast. It can be found by locating the Big Dipper high in the northeast and imagining that a hole were drilled in the bowl to let the water leak out. It would drip on the back of this giant cat. The Lion is standing or lying facing westward. His head and mane are seen in the stars as a backwards question mark. This group of stars is also called the Sickle. The bright star Regulus is at the bottom, the dot at the bottom of the question mark. A triangle of stars, to the left of Regulus, is the lion’s haunches. Leo contains some nice galaxies visible in moderate sized telescopes. The stars in Leo’s part of the sky are fewer than those in the winter sky.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Leaky Dipper drips on Leo

Leaky Big Dipper drips on Leo. The positions in the sky are for 10 pm local time, or about 2 hours after sunset. The little distorted cross at the top of the image marks the zenith. Look high in the east and southeast to see these stars. Created using my LookingUp program, GIMP and LibreOffice.

02/22/2022 – Ephemeris – The Winter Triangle

February 22, 2022 Comments off

This is Ephemeris for Tuesday, February 22nd. Today the Sun will be up for 10 hours and 49 minutes, setting at 6:21, and it will rise tomorrow at 7:30. The Moon, 1 day before last quarter, will rise at 1:26 tomorrow morning.

I’ve talked about the Winter Circle of bright stars already this winter, but some other astronomers talk about the Winter Triangle. The stars involved are Betelgeuse in the hunter Orion, Sirius in Canis Major, Orion’s large hunting dog, and Procyon in Canis Minor, his other small hunting dog. These three stars enclose a rather blank piece of sky with the faint Milky Way running through it and the almost invisible constellation of Monoceros the unicorn. The Summer Triangle has three bright stars with no other close competition. The Winter Triangle has four other bright stars near it. Any three of these would make a nice triangle. One of these constellations, Canis Minor, is tiny with Procyon and one other star. It makes me think of a dachshund, or maybe, if I’m hungry, a hot dog.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT -5 hours). They may be different for your location.

Addendum

Winter Triangle

The Winter Triangle. It encloses a pretty blank space where Monoceros the unicorn lies. Created using Stellarium with my annotations for the Winter Triangle.

08/05/2021 – Ephemeris – Looking toward the center of the Milky Way in Sagittarius

August 5, 2021 Comments off

This is Ephemeris for Thursday, August 5th. Today the Sun will be up for 14 hours and 29 minutes, setting at 9:02, and it will rise tomorrow at 6:35. The Moon, 3 days before new, will rise at 4:09 tomorrow morning.

Let’s look around the Teapot shape of stars that is the constellation of Sagittarius. A pair of binoculars or a telescope with a very low magnifying power is all that’s needed. The purpose here is not so much to make things bigger, but make them brighter. Right off the tip of the teapot’s spout is a large and bright patch of light. This is the farthest we can see, in visible light that is, toward the center of our galaxy, part of the central bulge. Astronomer Walter Baade discovered that fact in the mid 1940s. The center of the galaxy is 4 moon-widths or 2 degrees to the right of it, but obscured by a cloud of interstellar dust. It is called the Large Sagittarius Star Cloud or Baade’s Window. The glow there comes from 25 thousand light years away.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

Baade's Window AKA Large Sagittarius Star Cloud

Baade’s Window, aka Large Sagittarius Star Cloud. A finder animation created from my photograph taken August 23, 2016, at 11:23 pm. Click on the image to enlarge it.

08/03/2021 – Ephemeris – Centaur or Teapot?

August 3, 2021 Comments off

This is Ephemeris for Tuesday, August 3rd. Today the Sun will be up for 14 hours and 33 minutes, setting at 9:05, and it will rise tomorrow at 6:32. The Moon, 3 days past last quarter, will rise at 2:31 tomorrow morning.

In the south and low in the sky at 10:30 p.m. is one of my favorite asterisms the Teapot of the constellation Sagittarius. Sagittarius classically represents a centaur with a bow and arrow aimed at the heart of the constellation Scorpius to its west. I can find the bow and arrow here, but the half man, half horse figure of the centaur eludes me. However, the stout little teapot of the children’s song is quite obvious, with its base, lid on top, handle to the left and the spout to the right. To make things more realistic, the bright Milky Way seems to rise like steam from its spout. As the night goes on, the Teapot slides westward and appears to tilt, pouring its tea on the southwestern horizon. Its appearance in the south is an invitation to explore the milky band with binoculars.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

Sagittarius and the Teapot animation

Sagittarius and the Teapot finder animation for tonight, August 3rd. Created using Stellarium.

06/29/2021 – Ephemeris – The Summer Triangle

June 29, 2021 Comments off

This is Ephemeris for Tuesday, June 29th. Today the Sun will be up for 15 hours and 32 minutes, setting at 9:32, and it will rise tomorrow at 6:00. The Moon, 2 days before last quarter, will rise at 1:14 tomorrow morning.

Dominating the eastern sky at 11 pm are three bright stars. These are all first magnitude stars, members of the group of 21 brightest stars in the night sky. Highest, in the east, is Vega, the brightest of the three. It and a small, slim parallelogram of stars below it belong to the constellation of Lyra the harp. Below it to the northeast is Deneb, dimmest of the three at the head of the horizontally appearing Northern Cross, an informal constellation or asterism. Properly, Deneb is in the tail of Cygnus the swan flying south through the Milky Way. The third star of the three is Altair, lower still, but in the east-southeast at the head of Aquila the Eagle. These three stars are in a large asterism called the Summer Triangle, which will be with us through summer and fall.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT-4). They may be different for your location.

Addendum

Summer Triangle finder animation

The Summer Triangle finder animation showing first the unlabeled sky, Then the Summer Triangle with the stars labeled, then the constellations of those stars. Click on the image to enlarge it. Created using Stellarium and GIMP.

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.