Archive
Ephemeris: 02/21/2025 – Orion’s most distinctive feature
This is Bob Moler with Ephemeris for Friday, February 21st. Today the Sun will be up for 10 hours and 46 minutes, setting at 6:20, and it will rise tomorrow at 7:31. The Moon, 1 day past last quarter, will rise at 4:09 tomorrow morning.
Orion’s belt of three stars is one of the most noticeable star groupings in the sky. There are no other groups of three bright stars in a straight line visible anywhere else in the sky. The star’s names from left to right are Alnitak, Alnilam and Mintaka. They are actually a bit farther away than the other bright stars of Orion. Alnilam, the center star, is over three times the distance of red giant Betelgeuse above it and over twice as far as blue white giant star Rigel below it. Alnilam is 375 thousand times brighter than the Sun. These three stars were also known as Frigga’s Spindle by the Norsemen. Frigga, also known as Freya, is the goddess from whom we get the name of the day of the week we call Friday.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 02/20/2025 – Can you find the celestial unicorn?
This is Bob Moler with Ephemeris for Thursday, February 20th. Today the Sun will be up for 10 hours and 43 minutes, setting at 6:18, and it will rise tomorrow at 7:33. The Moon, at last quarter today, will rise at 3:06 tomorrow morning.
Among all the constellations in the sky of animals real and mythical, there is also a unicorn. It’s called Monoceros, and inhabits the southeastern sky at 8 p.m. mostly bounded by Orion on the right, Canis Major, the great dog below and Canis Minor, the little dog to the left and above. Unfortunately for observers without a telescope Monoceros, is devoid of any but the faintest stars. Maybe that’s why no one can find unicorns anymore. It has many faint stars because the Milky Way runs through it. For the astrophotographer it is a feast of star clusters and faint nebulae or clouds of gas and dust, the birthplace of stars, including the red rose of the Rosette Nebula. It also contains a beautiful telescopic triple star system, Beta (β) Monocerotis.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 02/19/2025 – All the naked-eye planets are seen in the evening this week
Ephemeris: 02/19/2025 – Where have the naked-eye planets wandered off to this week?
This is Ephemeris for Wednesday, February 19th. Today the Sun will be up for 10 hours and 40 minutes, setting at 6:17, and it will rise tomorrow at 7:34. The Moon, 1 day before last quarter, will rise at 1:59 tomorrow morning.
Let’s take our weekly look at the whereabouts of the naked-eye planets. At 7 PM this evening four of the five naked eye planets will be out. Starting from the West we have Venus the brightest of all in the west southwest. Far below it, near the horizon, will be the much dimmer Saturn, which we are about to lose, or may already have, to the evening twilight. Jupiter, the second-brightest planet will be high in the south. It has reversed course and is heading back eastward now. Farther below it is the spectacular constellation of Orion the hunter. The fourth planet out is Mars, the third-brightest planet now, with its distinctive reddish hue, west of the stars Castor and Pollux in Gemini, and in the east-southeast.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 02/18/2025 – Finding Orion’s greater hunting dog
This is Ephemeris for Tuesday, February 18th. Today the Sun will be up for 10 hours and 37 minutes, setting at 6:15, and it will rise tomorrow at 7:36. The Moon, 2 days before last quarter, will rise at 12:52 tomorrow morning.
The great winter constellation or star group Orion the Hunter, is located in the south-southeastern sky at 8 p.m. His elongated rectangle of a torso is almost vertical. In the center of the rectangle are three stars in a line that mark his belt. As a hunter, especially one of old, he has two hunting dogs. The larger, Canis Major can be found by following the three belt stars of Orion down and to the left. There lies the brilliant star called Sirius, also known as the Dog Star. It’s in the heart of a stick figure dog low in the southeast, facing Orion, that appears to be begging. There’s a fine star cluster, called M41, at the 5 o’clock position from Sirius, easily visible in binoculars or a small telescope.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 02/17/2025 – Follow the Drinking Gourd
This is Ephemeris for President’s Day, Monday, February 17th. Today the Sun will be up for 10 hours and 35 minutes, setting at 6:14, and it will rise tomorrow at 7:38. The Moon, 3 days before last quarter, will rise at 11:47 this evening.
In the decades before the Civil War, runaway slaves would travel, often at night, northward from the slave states in the south to the northern free states and Canada over the metaphorical Underground Railroad following the Drinking Gourd, the Big Dipper as their compass. For millennia, the North Pole of the sky had been passing near the handle of the Big Dipper or Great Bear’s tail and now up to the star Polaris in the Little Dipper. As an amateur astronomer, who loves the dark, starlit skies, I’ve noticed that everyone is the same color in the dark! This year the Grand Traverse Astronomical Society will, once again, team with the Sleeping Bear Dunes for more Sun and star parties.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 02/14/2025 – A Valentine’s Day Rendezvous
This is Ephemeris for St Valentine’s Day, Friday, February 14th. Today the Sun will be up for 10 hours and 26 minutes, setting at 6:10, and it will rise tomorrow at 7:42. The Moon, 2 days past full, will rise at 8:34 this evening.
Twenty-five years ago to the day, the NEAR-Shoemaker* spacecraft entered into orbit of the near Earth asteroid 433 Eros. It wasn’t originally planned to enter orbit of the asteroid named after the Greek god of love on Valentine’s Day, 2000. It arose after an aborted course correction a year earlier. After solving the problem, a new course was plotted and NEAR-Shoemaker was gently inserted into orbit of this 21 mile long asteroid, shaped like a bent bread stick with a bite taken out of the center of it. The spacecraft spent almost a year orbiting Eros at various altitudes. The spacecraft ended its mission by gently dropping onto the middle of the asteroid, where it stayed alive for ten days before succumbing to the cold.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
* The spacecraft was launched as NEAR for Near Earth Asteroid Rendezvous. It was renamed en route NEAR-Shoemaker after Eugene Shoemaker’s death in 1997. Shoemaker was a geologist who trained Apollo astronauts and proved that the Barringer Meteor Crater was indeed an impact site and not a volcanic caldera, and that most of the Moon’s craters were also caused by impacts. He with his wife Carolyn and David Levy discovered Comet Shoemaker-Levy 9, which crashed into Jupiter in 22 pieces in July 1994, gaining worldwide attention.
Addendum
NASA/JPL/JHUAPL. Caption from: https://eros2019.imcce.fr/eros.html via Google Translate.
Ephemeris: 02/13/2025 – A personal story
This is Bob Moler with Ephemeris for Thursday, February 13th. Today the Sun will be up for 10 hours and 23 minutes, setting at 6:08, and it will rise tomorrow at 7:44. The Moon, 1 day past full, will rise at 7:29 this evening.
Whenever I hear the term DEI used by someone that questions the qualifications of a person, or they speak of being apprehensive when they see someone of color or a woman piloting an airplane or having great responsibilities, I get angry. As a not so amateur astronomer in the past I’ve worked in and lectured at planetariums though I didn’t have the academic qualifications for, or sheepskin to prove it. I’m not sure that a black person could get away with what I did. But one thing I did learn as an amateur astronomer and working on star parties such as the ones we have in the summer at Sleeping Bear Dunes, is that everyone is the same color under the light of the stars.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 02/12/2025 – Taking our weekly look at the whereabouts of the naked-eye planets
This is Ephemeris for Darwin Day, Wednesday, February 12th. Today the Sun will be up for 10 hours and 20 minutes, setting at 6:07, and it will rise tomorrow at 7:45. The Moon, at full today, will rise at 6:21 this evening.
Let’s take our weekly look at the whereabouts of the naked-eye planets. At 7 PM this evening four of the five naked eye planets will be out. Starting from the West we have Venus the brightest of all in the west southwest. Far below it, near the horizon, will be the much dimmer Saturn, which we are about to lose to the evening twilight. Jupiter, the second-brightest planet will be high in the south-southeast. It is reversing course and beginning to head back eastward now. Farther below it is the spectacular constellation of Orion the hunter. The 4th planet out is Mars, the third-brightest planet now, with its distinctive reddish hue, west of the stars Castor and Pollux in Gemini, and just about due east. The full Moon will be rising in the east.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 02/11/2025 – Newly discovered asteroid may have our number
This is Ephemeris for Tuesday, February 11th. Today the Sun will be up for 10 hours and 17 minutes, setting at 6:06, and it will rise tomorrow at 7:47. The Moon, 1 day before full, will set at 8:06 tomorrow morning.
Late last year a tiny asteroid was found because it was close to the Earth and given the designation 2024 YR4. After observing it for a month it was discovered that it had a 1½ % chance of hitting the Earth when it came around again in 2032. Remember the fireball that exploded over Chelyabinsk Russia almost exactly 10 years ago? It exploded high in the air, and caused flying glass injuries to over a thousand people who saw the flash and rushed to the windows to see it when the atmospheric shock wave arrived. This object appears to be about 3 times the size of that object, nearly a football field in diameter, and thus could be 27 times the mass and volume. It’s four year orbit of the Sun will bring it back close to Earth in 2028 for us to get a better look at it and its orbit, and the last chance to alter its orbit.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 02/10/2025 – How old are the features on the Moon?
This is Ephemeris for Monday, February 10th. Today the Sun will be up for 10 hours and 14 minutes, setting at 6:04, and it will rise tomorrow at 7:48. The Moon, 2 days before full, will set at 7:42 tomorrow morning.
In dating Moon rocks scientists get a range of dates from 4.6 to 3.3 billion years. An age of a rock is determined by the decay of a radioactive element one of which is uranium 238 decaying to lead 206. So the ratios of these two elements gives a date when a rock was last solidified. This clock is reset when a rock was last melted either by volcanism or by asteroid impact. It turns out that the rocks of the highlands, the lighter area on the Moon where most of the craters are, date to close to 4.5 billion years, and are probably the original crust of the Moon. The rocks from the lunar maria or seas are younger from about 4.1 billion years down to 3.8 billion years. So they were thought to be caused by asteroid impacts from the Late Heavy Bombardment.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
The Late Heavy Bombardment is not accepted by all planetary scientists. The main evidence is the cratering and maria on the Moon.
Bob Moler's Ephemeris Blog 