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08/17/2021 – Ephemeris – Jupiter is big and bright in the evening
This is Bob Moler with Ephemeris for Tuesday, August 17th. Today the Sun will be up for 13 hours and 56 minutes, setting at 8:44, and it will rise tomorrow at 6:49. The Moon, 2 days past first quarter, will set at 2:02 tomorrow morning.
The brilliant planet we see rising in the east-southeast in the evening is not Venus, which is low in the west, ensnared in evening twilight. It’s Jupiter, the second-brightest planet and the largest by far. Jupiter would be the brightest planet except that the strength of sunlight falling on it is only 1/25th of what we get on the Earth and less than 1/50th of what Venus gets. Plus, it’s a lot farther away. Even in binoculars, Jupiter appears as not quite star-like. Most of the time, Jupiter is the largest appearing planet in telescopes. It is only beaten by Venus for a couple of months when it is nearest to us. When I was a kid, just learning about the planets, Jupiter had 12 moons. Astronomers by now have discovered 68 more.
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
Jupiter finder animation for tonight, August 17, 2021, at 9:15 pm. Venus i is in the west, which is brighter but suffering in bright twilight. Saturn may not be as easily visible as it is shown here until later. Credit: Stellarium and GIMP.
08/16/2021 – Ephemeris – The first Artemis mission (maybe) – CAPSTONE
This is Ephemeris for Monday, August 16th. Today the Sun will be up for 13 hours and 59 minutes, setting at 8:46, and it will rise tomorrow at 6:47. The Moon, 1 day past first quarter, will set at 1:13 tomorrow morning.
Tonight’s Moon is a great one to view with a small telescope. Speaking of the Moon, a company called Rocket Lab will be launching the first Artemis program mission, later this year, in preparation to land crews back on the Moon. They are launching a small CubeSat to orbit the Moon in a Near Rectilinear Halo Orbit which always faces the Earth and never goes behind the Moon. To test whether all the mathematical calculations for the orbit actually work in real life. The satellite is called CAPSTONE (another tortured NASA acronym*). It will be launched from New Zealand, Rocket Lab’s main launch site first into a polar orbit before heading to the lunar orbit, taking several months to get there.
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.
* Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment. Told ya. Cislunar space is a spherical volume of space centered on the Earth, whose radius is the Moon’s distance. Beyond that is interplanetary space.
Addendum
Rocket Lab had been planning to launch the CAPSTONE satellite from Wallops Island, Virginia, but approval was taking too long, so they moved the launch to their New Zealand launch site instead.
NASA CAPSTONE* pathfinder for gateway orbit is to be launched late this year by Rocket Lab to prove out the near rectilinear orbit for the Lunar Gateway.
08/13/2021 – Ephemeris – Rescheduled virtual star party tonight
This is Bob Moler with Ephemeris for Friday, August 13th. Today the Sun will be up for 14 hours and 8 minutes, setting at 8:51, and it will rise tomorrow at 6:44. The Moon, 2 days before first quarter, will set at 11:36 this evening.
The Grand Traverse Astronomical Society will try again to hold a virtual star party starting at 9:30 pm tonight via the Zoom app on the Internet. We were clouded out last Friday night. Jerry Dobek, professor of astronomy at Northwestern Michigan College, will host the event with the 16-inch telescope at the College’s Observatory and an imager, but only if it’s clear in Traverse City. It should feature a look at Venus and the crescent Moon to start. Saturn and Jupiter will be up by then, but they’re quite low in the sky. We might take another look at them later on when their images are steadier. The wonders of the Milky Way are all available. Instructions and a link can be found on the society’s website, www.gtastro.org.
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
The southern Milky Way from Aquila to Sagittarius taken from my backyard with light pollution from businesses on US 31 in Chums Corners and Grawn south of me. I live about 7 miles west of the NMC Observatory. These bright lights are to its southwest and farther away. Click on the image to enlarge it.
08/12/2021 – Ephemeris – It’s not too late to see the Perseids
This is Ephemeris for Thursday, August 12th. Today the Sun will be up for 14 hours and 10 minutes, setting at 8:52, and it will rise tomorrow at 6:43. The Moon, 3 days before first quarter, will set at 11:13 this evening.
It’s not too late to see the Perseid meteors. The projected peak of the shower is expected to be between 3 and 6 this afternoon. So the meteor shower should still be quite active. It has been my experience that the numbers of meteors decline more rapidly than they increase before the peak. NASA can determine their orbits using all sky cameras placed at different locations to get their paths by triangulation. The cameras have shutters the interrupt the meteor track at a specific interval, which allow them to determine the meteor’s speed and are able to calculate the particle’s orbit of the Sun. An animation of these orbital tracks can be found on the International Meteor Organization website imo.net.
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
I’ve been talking about the Perseid meteor shower all week, so far. Click on the calendar dates to the upper right to review those posts.
A Perseid outburst from 2009. Credit NASA/JPL via Phil Plait’s Bad Astronomy.
Perseid fireballs in one of NASA’s all sky cameras during the morning hours of August 13, 2017. This is a long time exposure. The bright swath in the image is the Moon that morning. Since it is a time exposure, the radiant is also moving with the earth’s rotation, so the meteors only seem to come from the northeastern sky. North is at the top, and East is to the left. Credit NASA.
08/11/2021 – Ephemeris – Let’s search for the naked-eye planets for this week, and meteors tonight
This is Bob Moler with Ephemeris for Wednesday, August 11th. Today the Sun will be up for 14 hours and 13 minutes, setting at 8:54, and it will rise tomorrow at 6:42. The Moon will be 3 days past new tonight.
Let’s search for the naked-eye planets for this week. Venus and the Moon will be close together tonight, with Venus below and right of the waxing crescent Moon by 9:30 tonight. Venus will set at 10:18 pm. With the Moon following at 10:50. By 10 pm, Jupiter and Saturn will be seen low in the southeastern sky. The brighter Jupiter will be easy to spot at that hour. Saturn will be dimmer, but a bit higher and to its right. Tonight and especially in the morning hours tomorrow, the Perseid meteors will be at their peak. These bits of Comet Swift-Tuttle, liberated by the comet’s prior passes in through the warmth of the inner solar system, will flash into incandescence as they enter the Earth’s atmosphere at interplanetary speeds.
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
Venus and the 3-day-old Moon ion evening twilight at 9:45 tonight, August 11, 2021. Created using Stellarium.
The Moon as it might appear in binoculars tonight, August 11, 2021, with earth shine on its night side, illuminated by the bright Earth in its sky.
Created using Stellarium.
Jupiter and Saturn in the southeastern sky at 10:30 in the evening tonight, August 11, 2021. Created using Stellarium.
Telescopic view of the bright planets (north up) as they would be seen in a small telescope, with the same magnification, this evening, at 10 pm August 11, 2021. Apparent diameters: Venus, 13.40″; Saturn 18.57″, its rings 43.26″; Jupiter, 49.00″. Jupiter’s moon have a cluster of events in the evening. See below. The ” symbol means seconds of arc (1/3600th of a degree.) Click on the image to enlarge it. Created using Cartes du Ciel (Sky Charts).
Jupiter's Satellite events
Moon Event EDT (pm-11th, am-12th) UT (12th)
Europa Shadow enters 10:00 pm 02:00
Europa Transit starts 10:25 pm 02:25
Io Eclipse starts 10:41 pm 02:41
Europa Shadow exits 12:51 am 04:51
Ganymede Occultation ends 1:06 am 05:06
Io Occultation ends 1:11 am 05:11
Europa Transit ends 1:12 am 05:12
The above times were determined using Stellarium, and may be off by several minutes.
Shadow events are when a satellite’s shadow is cast onto the face of the planet
Transit events are when the satellite passes in front of the planet
Eclipse events are when a satellite passes through the planet’s shadow
Occultation events are when the satellite passes behind the planet
Planets and the Moon at sunset and sunrise of a single night, starting with sunset on the right on August 11, 2021. The night ends on the left with sunrise on the 12th. Click on the image to enlarge. Created using my LookingUp program.
Perseid Radiant finder automation for midnight, August 11th. Created using Stellarium and GIMP.
More on the Perseids on Monday and Tuesday’s posts.
08/10/2021 – Ephemeris – Tomorrow night, all night, will see the peak of the Perseid Meteor Shower.
This is Bob Moler with Ephemeris for Tuesday, August 10th. Today the Sun will be up for 14 hours and 16 minutes, setting at 8:55, and it will rise tomorrow at 6:40. The Moon, 2 days past new, will set at 10:27 this evening.
Back before astronomers recognized the major meteor shower that occurs at this time of year, the streaks of light in the sky of “falling” or “shooting” stars were called, by Christians, the Tears of Saint Lawrence, who was martyred on this day in the year 258. The bits of comet debris ranging in size from the size of sand grains to that of a pea hit our atmosphere at 38 miles (59 kilometers) per second and quickly vaporize due to friction, causing the streak of light we call meteors. They are called the Perseids since they appear to come from the constellation of Perseus, located in the northeastern sky. They will be best seen tomorrow night and into Thursday morning, with rates of up to one a minute, on average, in the early morning hours.
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
Perseid Radiant finder automation for midnight, August 11th. Created using Stellarium and GIMP.
My best Perseid photo. From the 70s. The stars are trailed because this is a time exposure of perhaps 15 minutes and the camera is on a fixed tripod which rotates with the Earth.
08/09/2021 – Ephemeris – The Perseid Meteors are coming!
This is Ephemeris for Monday, August 9th. Today the Sun will be up for 14 hours and 18 minutes, setting at 8:57, and it will rise tomorrow at 6:39. The Moon, 1 day past new, will set at 10:03 this evening.
If you’ve been out and about under the dark night skies in the last week or so, you may have spotted a few, what are sometimes called, falling or shooting stars. If these could be traced back to the northeastern sky, those were advance members of the Perseid Meteor Shower. The peak of the shower will be on the afternoon of Thursday the 12th, so actually the best time to see them will be in the early hours of that morning. With few exceptions, the best time to view meteors in general or a meteor shower is in the wee morning hours. The Perseids however favor us, because the point from which they seem to come, called the radiant, is so far north that it never sets for us, so they can be seen all night. In the evening, there are just fewer of them.
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
Perseid fireballs in one of NASA’s all sky cameras during the morning hours of August 13, 2017. This is a long time exposure. The bright swath in the image is the Moon that morning. Since it is a time exposure, the radiant is also moving with the earth’s rotation, so the meteors only seem to come from the northeastern sky. North is at the top, and East is to the left. Credit NASA.
08/06/2021 – Ephemeris – Virtual Star Party tonight if it’s clear in Traverse City
This is Ephemeris for Friday, August 6th. Today the Sun will be up for 14 hours and 26 minutes, setting at 9:01, and it will rise tomorrow at 6:36. The Moon, 2 days before new, will rise at 5:11 tomorrow morning.
The Grand Traverse Astronomical Society will hold a virtual star party starting at 10 pm tonight via the Zoom app on the Internet. Jerry Dobek, professor of astronomy at Northwestern Michigan College, will host the event with the 16-inch telescope and an imager, but only if it’s clear in Traverse City. It should feature a look at Venus to start. Saturn and Jupiter will be up by then, but they’re quite low in the sky. We might take another look at them later on when their images are steadier. The wonders of the Milky Way are all available, clouds willing: nebulae where stars are forming, nebulae caused by dying stars, and all kinds of star clusters. Instructions to join the meeting and a link can be found on the society’s website, www.gtastro.org.
Addendum
The Milky Way from Aquila to Sagittarius taken from my backyard with light pollution south of me. The summer southern Milky Way is the reason I love the dark nights of August and September. It’s the best time of year for a star party. I’m 7 miles west of Northwestern Michigan College’s Joseph H. Rogers Observatory, from which the images for tonight’s star party will be captured.
08/05/2021 – Ephemeris – Looking toward the center of the Milky Way in Sagittarius
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. A finder animation created from my photograph taken August 23, 2016, at 11:23 pm. Click on the image to enlarge it.
08/04/2021 – Ephemeris – Let’s search for the naked-eye planets for this week
This is Bob Moler with Ephemeris for Wednesday, August 4th. Today the Sun will be up for 14 hours and 31 minutes, setting at 9:04, and it will rise tomorrow at 6:33. The Moon, halfway from last quarter to new, will rise at 3:16 tomorrow morning.
Let’s search for the naked-eye planets for this week. Venus can be spotted low in the western twilight by 9:45 pm. It will set at 10:29 pm. Venus will be spending the rest of summer low in the western sky, and not be as conspicuous as it usually is as the Evening Star. Mars is to faint and close to the Sun to be seen from northern latitudes. Saturn, now officially an evening planet, rises before sunset. It will be seen low in the southeast in the evening. Brighter Jupiter will rise at 9:38 pm in the east-southeast and will be seen thereafter trailing Saturn to it’s left or east. Jupiter will join Saturn as an evening planet on the 19th when it too reaches opposition from the Sun.
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
Venus in evening twilight at 9:45 pm, or about 40 minutes after sunset tonight, August 4, 2021. Created using Stellarium.
Jupiter and Saturn in the Southeastern sky at 10;30 pm tonight, August 4, 2021. Created using Stellarium.
The waning crescent Moon as it might be seen in binoculars tomorrow morning at 6 am, about an half an hour before sunrise. Created using Stellarium.
Telescopic view of the bright planets (north up) as they would be seen in a small telescope, with the same magnification, this evening, August 4, 2021. Apparent diameters: Venus, 12.93″; Saturn 18.60″, its rings 43.32″; Jupiter, 48.71″. The ” symbol means seconds of arc (1/3600th of a degree.) Click on the image to enlarge it. Created using Cartes du Ciel (Sky Charts).
Note on Jupiter and its moons. The Great Red Spot will be visible on the face of Jupiter. Europa will end its transit of the planet around 11:00 pm (03:00 UT on the 5th) Io will be occulted by Jupiter (behind the planet) in the early evening until about 11:27 pm (03:27 UT on the 5th) and will appear to the east of the planet.
Planets and the Moon at sunset and sunrise of a single night, starting with sunset on the right on August 4, 2021. The night ends on the left with sunrise on the 5th. Click on the image to enlarge. Created using my LookingUp program.
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