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06/12/2015 – Ephemeris – The first stars to appear at night
Ephemeris for Friday, June 12th. Today the Sun will be up for 15 hours and 31 minutes, setting at 9:28. The Moon, 3 days past last quarter, will rise at 4:03 tomorrow morning. Tomorrow the Sun will rise at 5:56.
Evening twilight lasts a very long time this time of year, so the stars will come out slowly. By about a half hour after sunset the planets Venus and Jupiter should be visible in the west. Probably the first actual star to appear is very high in the east, the orange star Arcturus in the constellation of Boötes, which is the 4th brightest night-time star. Next, lower in the northeast, is the 5th brightest star the white Vega in Lyra the harp. By this time Saturn should appear low in the southeast as a yellowish star. Soon many more stars will become visible with the Big Dipper overhead pointing to Polaris in the north, blue-white Spica in the south, Regulus, left of Jupiter and Capella low in the northwest.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The first stars to appear after sunset. This is created from Stellarium for a half hour after sunset. It’s a bit optimistic, in my view, though my eyes aren’t the best. Try your eyes. Click on image to enlarge.
05/12/2015 – Ephemeris – Arcturus, a look at the Sun’s future
Ephemeris for Tuesday, May 12th. Today the Sun will be up for 14 hours and 42 minutes, setting at 9:00. The Moon, 1 day past last quarter, will rise at 3:43 tomorrow morning. Tomorrow the Sun will rise at 6:17.
Arcturus, a red giant star is about midway up the sky in the southeast at 10 p.m. It’s visible earlier, being the 4th brightest night-time star and the third brightest star-like object out at that time after Venus and Mars. A pointer to it 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.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Finding Arcturus. Orientation for 11 p.m. on May 12, 2015. Created using Stellarium.
Evolution of a sun-like star. Note the sizes of the star at the various stages are compressed, also the time line. In the red giant stage the star is possibly a hundred times larger than at the main sequence stage. The white dwarf stage is a hundred times smaller than the main sequence stage. Click to enlarge. Credit: From a NASA/Chandra poster.
04/06/2015 – Ephemeris – Arcturus the 4th brightest star
Ephemeris for Monday, April 6th. The Sun will rise at 7:14. It’ll be up for 13 hours and 1 minute, setting at 8:16. The Moon, 2 days past full, will rise at 10:37 this evening.
One of the stars that stays up most of the year, except late autumn and most of winter is Arcturus. Now in the evening Arcturus is low in the east. It’s a bright star, officially the 4th brightest star in the night sky, and the 4th brightest star-like object in our night sky after Venus, Jupiter, and Sirius. Arcturus can be found by following the arc of the handle of the Big Dipper to it. Remember, follow the arc to Arcturus. Arcturus belongs to the kite shaped constellation of Boötes, which we’ll visit in greater detail when it’s higher in the sky. Arcturus is an interesting star. It’s 37 light years away, and moving quite rapidly at 75 miles per second (122km/s), mostly across the sky. Some astronomers think that it
Arcturus off the handle of the Big Dipper at 9:30 p.m. April 6, 2015. Created using Stellarium.
may be part of a captured dwarf galaxy.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
03/27/2015 – Ephemeris – The North Star, Polaris
Ephemeris for Friday, March 27th. The Sun will rise at 7:33. It’ll be up for 12 hours and 30 minutes, setting at 8:03. The Moon, at first quarter today, will set at 3:49 tomorrow morning.
Tonight we turn our eyes northward to Polaris, the North Star. It is the closest bright star to the north pole of the sky. It appears nearly stationary as all the other stars appear to revolve around it as the Earth rotates. Some folks, think that Polaris is the brightest star in the sky. It’s not. It is a good solid second magnitude star, about the brightness of a Big Dipper star. The Big Dipper can be used to point to it, by using the two stars at the front of the bowl. Polaris is at the end of the handle of the Little Dipper. The Little Dipper has four dim stars in its rather oddly bent handle and back of its bowl. The two stars at the front of the bowl of the Little Dipper are Kochab and the dimmer Pherkad, which are also called the Guard Stars or the Guardians of the Pole.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
How to find Polaris. The grid is the equatorial grid showing the proximity to the pole. Created using Stellarium.
02/16/2015 – Ephemeris – The Winter Circle
Feb 16. This is Bob Moler with Ephemeris for President’s Day, Monday, February 16th. The sun will rise at 7:42. It’ll be up for 10 hours and 30 minutes, setting at 6:12. The moon, 2 days before new, will rise at 6:25 tomorrow morning.
The winter skies are blessed with more first magnitude stars than any other season. That’s a full one-third of the total are seen is a relatively small area. Six of these stars lie in a large circle centered on the seventh. This circle is up at 9 p.m. Starting high overhead is Capella in Auriga the charioteer. Moving down clockwise is Aldebaran in the face of Taurus the Bull. 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, lowest of these stars in the south-southeast. Moving up and left is Procyon in Canis Minor, Above Procyon is Pollux in Gemini the twins. All these are centered on Betelgeuse the bright red star in Orion’s shoulder.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Winter Circle of 1st magnitude stars
02/13/2015 – Ephemeris – The stars Castor and Pollux
Ephemeris for Friday, February 13th. The sun will rise at 7:46. It’ll be up for 10 hours and 21 minutes, setting at 6:08. The moon, 2 days past last quarter, will rise at 3:51 tomorrow morning.
At 9 p.m. the constellation of Gemini the twins will be seen high in the southeast. The namesake stars of the two lads are the two bright stars at the top of the constellation. Pollux the pugilist, or boxer, is the lower of the two, while Castor, the horseman, is the other star, or rather a six star system. In telescopes two close stars may be seen each is a spectroscopic binary, meaning the lines of two stars can be seen in the spectrum. A faint nearby spectroscopic binary also belongs. Pollux, though a single star, does have at least one planet, one over twice the mass of Jupiter orbiting the star at a distance somewhat greater than Mars is from the sun. Pollux is 34 light years away while Castor is 50 light years away. Not too far away as stars go.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Gemini with the stars Castor and Pollux. Created using Stellarium.
02/12/2015 – Ephemeris – The brilliant blue star in Orion: Rigel
Ephemeris for Thursday, February 12th. The sun will rise at 7:47. It’ll be up for 10 hours and 18 minutes, setting at 6:06. The moon, 1 day past last quarter, will rise at 2:52 tomorrow morning.
Two days ago I talked about the star Betelgeuse the bright red star in the top left of Orion’s upright rectangle. Orion is seen in the south at 9 in the evening. The blue-white star in Orion’s opposite corner is usually brighter. It is Rigel whose longer Arabic name of which Rigel is the first part means Left Leg of the Giant. Rigel is a giant itself, actually a super giant star, which is more a measure of its mass than its size, that of 21 solar masses. Its surface temperature is more than twice as hot as the sun. It is 120 thousand times as bright as the sun and 78 times its diameter. Its distance is around 860 light years. Those with telescopes might be able to spot a close companion star to Rigel, just at the edge of the bright arc light image of Rigel itself.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Orion upright and due south. Created using Stellarium.
Rigel with its companion star as photographed through a telescope. No attribution. Source: http://washedoutastronomy.com/content/urban-orion?page=1
02/10/2015 – Ephemeris – Orion’s bright red star, Betelgeuse
Ephemeris for Tuesday, February 10th. The sun will rise at 7:50. It’ll be up for 10 hours and 13 minutes, setting at 6:03. The moon, 1 day before last quarter, will rise at 12:51 tomorrow morning.
The bright red star in constellation Orion’s shoulder is Betelgeuse, and its now thought to be about 640 light years away give or take a couple of hundred light years*. The name Betelgeuse means “Armpit of the central one” in Arabic. Orion is seen in the south at 9 in the evening. Even at Betelgeuse’ great distance it’s the star whose surface is easiest seen, after the sun of course. That’s because it’s so big. As large around as the size of the orbit of Jupiter. Betelgeuse is losing mass in a huge cloud around it. It is a massive star in the late stages of its life even though it’s only 7 million years old. Some astronomers speculate that it will explode in a massive supernova within the next million years.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Update
* I’m being a bit facetious here. See the addendum, and also by coincidence a post from EarthSky today How far is Betelgeuse?
Addendum
Orion upright and due south. Created using Stellarium.
Our estimates of the size, mass and luminosity of Betelgeuse depend on knowing its distance. The distance is not well-known because Betelgeuse is a single star, it is not a binary for which can be applied Newton’s laws to calculate these values. Therefore these values in the broadcast program, where I have 59 seconds total, appear more certain than they really are. Wait for Thursday’s program when I cover Rigel and see how close the values are between the two. But Rigel appears to be a different star altogether. Somebody’s wrong.
“This artist’s impression shows the supergiant star Betelgeuse as it was revealed thanks to different state-of-the-art techniques on ESO’s Very Large Telescope, which allowed two independent teams of astronomers to obtain the sharpest ever views of the supergiant star Betelgeuse. They show that the star has a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface. These discoveries provide important clues to help explain how these mammoths shed material at such a tremendous rate. The scale in units of the radius of Betelgeuse as well as a comparison with the Solar System is also provided.” Credit: ESO/L. Calçada (ESO is the European Southern Observatory)
01/19/2015 – Ephemeris – Sirius, the brightest star in the night
Ephemeris for Martin Luther King Day, Monday, January 19th. The sun will rise at 8:14. It’ll be up for 9 hours and 19 minutes, setting at 5:33. The moon, 1 day before new, will rise at 7:53 tomorrow morning. | The star Sirius is the brightest night-time star in the heavens. It’s up on frosty winter evenings, and currently low in the southeastern sky in the early evening. It can be found in line and left of the three stars of Orion’s belt. It’s known as the Dog Star because it’s in the heart of the constellation Canis Major the greater dog. Sirius, however means dazzling one or sparkling one due to its brightness and the long time it spends low to the horizon where our turbulent atmosphere breaks up its light as a sparkler of color in telescopes and binoculars. Sirius owes its brightness mostly to its close proximity of 8.6 light years. It is 25 times brighter than the sun. It also has a white dwarf companion star nicknamed the Pup.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Sirius A and B (near the diffraction spike to the lower left), A Hubble Space Telescope photograph. Credit NASA, ESA.
01/06/2015 – Ephemeris – Star to stir up solar system’s comets, but you’re gotta wait a bit.
Ephemeris for Tuesday, January 6th. The sun will rise at 8:19. It’ll be up for 8 hours and 57 minutes, setting at 5:17. The moon, 2 days past full, will rise at 7:12 this evening.
In about a quarter to half a million years from now a star with the name HIP 85605 will pass through the Oort cloud of comets that is the extreme outer part of the solar system. The star’s name comes from the Hipparcos catalog created from data from the European satellite which created improved distances of nearby stars. HIP 85605 star is nearby and very faint. The star should pass through the Oort cloud twice, coming and going. What happens is the star will tend to scatter small bodies in its wake, throwing some comets in toward the sun and others it will eject from the solar system. There were all kinds of scare headlines out of this. Something like this “Will a comet shower end life on the Earth?” No it won’t. This kind of thing happens every few million years.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
NASA diagram of the solar system on a logarithmic scale. Each interval is ten times longer than the one on the left. On this scale the star HIP 85605 will penetrate to the inner part of the Oort cloud. Click to enlarge.
Tip o’the old astronomer’s cap to Universe Today where I found this story.
Bob Moler's Ephemeris Blog 