Archive
07/25/2013 – Ephemeris – Vega, the fifth brightest night-time star
Ephemeris for Thursday, July 25th. The sun rises at 6:21. It’ll be up for 14 hours and 54 minutes, setting at 9:15. The moon, 3 days past full, will rise at 10:43 this evening.
The star Vega, which is nearly overhead or the zenith is a special star for astronomers. It’s part of the small constellation of Lyra the harp, which includes the parallelogram of stars near it. Vega is kind of a standard calibration star. It is the 5th brightest night-time star with a brightness of 0 magnitude, although recent measurements place it at 0.03. Of the spectral types which denote the star’s color and surface temperature, Vega comes out to be pure white, with a surface temperature nearly twice the sun’s. It’s almost exactly 25 light years away, and so is one of the closer stars. It’s a tenth the sun’s age and 40 times the sun’s brightness. It has perhaps a Jupiter sized planet, and a Kuiper belt of Pluto like objects orbiting it.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Magnified view of Lyra showing Vega. Created using Stellarium.
07/22/2013 – Ephemeris – The star Deneb, brighter than it looks
Ephemeris for Monday, July 22nd. Today the sun will be up for 15 hours, setting at 9:18. The moon, at full today, will rise at 9:00 this evening. Tomorrow the sun will rise at 6:19.
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 south. While Deneb’s apparent magnitude, or brightness as seen from earth, makes it the dimmest of the three bright stars, Deneb’s vast distance of possibly 2,600 light years makes it 100 times the distance of Vega. If brought as close as Vega, Deneb would be several time 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 it will explode, go supernova, in perhaps a few million years.
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.
07/18/2013 – Ephemeris – The bright star Altair
Ephemeris for Thursday, July 18th. Today the sun will be up for 15 hours and 7 minutes, setting at 9:22. The moon, 3 days past first quarter, will set at 2:56 tomorrow morning. Tomorrow the sun will rise at 6:15.
Of the three stars of the Summer Triangle Altair in the constellation Aquila the eagle is the farthest one south and the closest. Altair is at a distance of 16.8 light years away. One light year is nearly 6 trillion miles. Altair is 10 times the brightness of the sun. While it’s almost twice the sun’s diameter, it rotates once in only 9 hours, and has a decidedly squashed appearance when seen close up. There are techniques that can actually accomplish this. Our sun’s a slow poke, taking nearly a month to rotate once. In science fiction the Altair system was the scene for the classic film Forbidden Planet, one of the few science fiction classic films of the 1950s.
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.
False-color image of the rapidly rotating star Altair, made with the MIRC imager on the CHARA array on Mt. Wilson.
United Planets Cruiser C57-D lands on Altair IV in the 1956 movie Forbidden Planet.
07/16/2013 – Ephemeris – The red giant star Antares
Ephemeris for Tuesday, July 16th. Today the sun will be up for 15 hours and 11 minutes, setting at 9:23. The moon, 1 day past first quarter, will set at 1:24 tomorrow morning. Tomorrow the sun will rise at 6:13.
Low in the south is the red giant star Antares. It lies at the heart of Scorpius the scorpion. Its name means Rival of Mars, because it has the same hue as the red planet. In Mars case the color comes from iron oxide, rust. In Antares case it has a cool surface temperature, relatively speaking of 5,700 degrees Fahrenheit. As a red giant star Antares is near the end of its life, though for a star Antares is young, possibly 12 million years old. That that age the sun was just getting started. But Antares with around 15 to 17 the sun’s mass has already run out of fusible hydrogen in its core and bloated out to over Mars orbit in size. Antares is 450 light years away and has a companion star in its system that looks greenish in contrast to Antares red. However when Antares A, the red giant’s light is blocked, the companion looks bluish.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The constellation Scorpius and the star Antares. Created using Stellarium.
07/15/2013 – Ephemeris – The moon will appear near Spica tonight
Ephemeris for Monday, July 15th. Today the sun will be up for 15 hours and 12 minutes, setting at 9:24. The moon, at first quarter today, will set at 12:48 tomorrow morning. Tomorrow the sun will rise at 6:12.
The moon this evening is very close to the bright star Spica. It might take a pair of binoculars to spot it in the glare of the moon. Spica will be just above left of the moon tonight. For other spots on the earth the moon will actually pass in front of the star. The event is called an occultation, from the word occult meaning hidden. Simply put the moon will pass in front of or hide the star for up to an hour. The chief beneficiary of this occultation is the state of Hawai’i. Occultations are one of the best ways to measure the position, diameter and shape of distant asteroids and Kuiper belt objects that are too small to measure otherwise. Satellites of these objects have also been discovered this way.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Spica and the Moon at 10 p.m. on July 15, 2013. Created using Stellarium.
Path on the Earth where the occultation of Spica will be visible. Credit Astronomical Almanac Online.
The Astronomical Almanac Online ( http://asa.usno.navy.mil/) “is a joint publication of the U. S. Nautical Almanac Office, United States Naval Observatory (USNO), in the United States and Her Majesty’s Nautical Almanac Office (HMNAO), United Kingdom Hydrographic Office (UKHO), in the United Kingdom.”
07/04/2013 – Ephemeris – Patriotic Stars: Red, White and Blue
Ephemeris for Independence Day in the United States, Thursday, July 4th. Today the sun will be up for 15 hours and 27 minutes, setting at 9:30. The moon, half way from last quarter to new, will rise at 4:05 tomorrow morning. Tomorrow the sun will rise at 6:03.
Today is Independence Day so let’s look for some red, white, and blue stars. Red is easy, the red star Antares is seen in the south at 11 p.m. White is easy too, the official white calibration star Vega high in the east at 11 p.m. The blue star is really blue-white. The brightest of these out at 11 p.m. is Spica, low in the southwest to the right of the brighter Saturn. The color is best seen in binoculars. Star colors are quite subtle, and are an indicator of the temperature of their outer gaseous layers. The temperature of a stars outer layers, in order of their increasing temperatures are red, white and blue. Of these three the coolest on the outside, Antares is really the hottest inside, using helium as fuel.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Red Antares, white Vega and blue Spica. Patriotic Stars this evening. Created using Stellarium.
06/06/2013 – Ephemeris – Star colors
Ephemeris for Thursday, June 6th. Today the sun will be up for 15 hours and 26 minutes, setting at 9:24. The moon, 2 days before new, will rise at 5:22 tomorrow morning. Tomorrow the sun will rise at 5:57.
Star and planets colors are quite subtle. This is partly due to the fact that we are color blind at very low light levels. Only the brightest stars show color at all. Telescopes however aid our color perception because it makes the stars brighter. The planet Saturn, now in the south at night has a distinct yellowish hue, caused by the color of its atmosphere. The star Spica to its right is the bluest of the bright first magnitude stars, and shows as a bright arc light. Arcturus, above both Saturn and Spica has a yellow to orange hue. Antares low in the southeast has a definite reddish hue. In a telescope it also looks like a sparkler due to our turbulent atmosphere. Red stars are the coolest stars (temperature wise) while blue-white stars are the hottest.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Stellarium does a pretty good job of showing the subtle colors of stars, which is also reflected in the color of the star labels. Click on the image to enlarge.
05/20/2013 – Ephemeris – Silicon rings around old stars in the Hyades
Ephemeris for Monday, May 20th. Today the sun will be up for 15 hours and 0 minutes, setting at 9:09. The moon, 2 days past first quarter, will set at 3:45 tomorrow morning. Tomorrow the sun will rise at 6:08. | I found this item at Universe Today, an astronomical news website, universetoday.com. The Hubble Space telescope has found evidence of rings of mainly silicon around two white dwarf stars in the Hyades star cluster. The Hyades is the V-shaped star cluster just below the setting Jupiter these nights. White dwarf stars are old stars in their last stage of life and usually don’t show the absorption of heavy elements in their spectrum. These two stars must have pulverized rings of silicon plus a little carbon orbiting them, suggesting the formation of earth-like planets. Astronomers usually don’t see this in cluster stars, which are generally young and too active to show planet forming material close to them.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
05/14/2013 – Ephemeris – How to find two bright spring stars.
Ephemeris for Tuesday, May 14th. Today the sun will be up for 14 hours and 47 minutes, setting at 9:02. The moon, 4 days before first quarter, will set at 12:48 tomorrow morning. Tomorrow the sun will rise at 6:14.
The Big Dipper, now pretty much overhead points to several stars and constellations. It’s handle points to two bright stars. First we follow the arc of the handle to the bright orange star Arcturus, the 4th brightest night time star. The reason I say night time is that the sun is a star also but by definition is not out at night. The arc to Arcturus is a how to find Arcturus and a clue to its name. Arcturus, high in the east southeast, lies at the base point of the kite shaped constellation of Boötes the herdsman. From Arcturus, straighten out the arc to a spike and one soon arrives at Spica a blue-white star in Virgo the virgin, now low in the southeast. Saturn is to its left this year. Spica is also sometimes pronounced “Speeka”.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
My program that shows the arc to Arcturus and spike to Spica.
A more realistic view of the same part of the sky. Created using Stellarium.
03/04/2013 – Ephemeris – The Winter Circle
Ephemeris for Monday, March 4th. The sun will rise at 7:14. It’ll be up for 11 hours and 20 minutes, setting at 6:34. The moon, at last quarter today, will rise at 2:34 tomorrow morning.
The winter skies are blessed with more first magnitude stars than any other season. Six of these stars lie in a large circle centered on the seventh. This circle is up all evening now that we are in the heart of winter. Starting high overhead is Capella in Auriga the charioteer. Moving clockwise and downward, we come to Aldebaran in the face of Taurus the Bull and brighter nearby Jupiter. Then down to Orion’s knee we find Rigel. Down and left is the brightest star of all Sirius the Dog Star in Canis Major Orion’s large hunting dog, lowest of these stars in the south. Moving up and left there is Procyon in Canis Minor Orion’s other hunting dog, Then above is Pollux in Gemini the twins. All are centered on Betelgeuse in Orion.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Winter Circle and Jupiter for March. Created using Stellarium.
Bob Moler's Ephemeris Blog 