08/07/2018 – Ephemeris – The source of the Perseids

Ephemeris for Tuesday, August 7th. The Sun rises at 6:35. It’ll be up for 14 hours and 24 minutes, setting at 9:00. The Moon, 3 days past last quarter, will rise at 3:18 tomorrow morning.

The Perseid meteor shower will reach its peak Sunday night and Monday morning, less than a week from now. The meteor shower is caused by tiny particles shed by the comet 109P/Swift-Tuttle on past trips through the inner solar system. The 109P means it was recognized as the 109th comet to have seen to return to the vicinity of the Sun to be rediscovered in 1992. Lewis Swift and Horace Tuttle first discovered the comet independently in 1862. The orbit of the comet fit the orbits of the meteoroids that produce the Perseid meteor shower each year. The comet will return in 2126 after retreating to 51 times the Earth’s distance from the Sun, deep in the Kuiper belt, leaving behind a trail of meteoroids.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The passage of 109P/Comet Swift-Tuttle through the inner solar system November 1, 1992 to January 30, 1993. The meteoroids shed by the comet on its numerous trips close to the Sun lie close to that orbit. Note that its orbit intersects with the Earth’s orbit. That’s where the Earth will be around August 12-13 every year. Click on the image to enlarge. Created using my LookingUp program.

08/09/2016 – Ephemeris – A look at the Perseids progenitor

Ephemeris for Tuesday, August 9th.  The Sun rises at 6:38.  It’ll be up for 14 hours and 18 minutes, setting at 8:56.  The Moon, 1 day before first quarter, will set at 12:23 tomorrow morning.

Comet Swift-Tuttle is the comet responsible for the Perseid Meteor Shower which is now ramping up and will reach its peak Thursday night and Friday morning.  The comet was independently discovered by Swift and Tuttle in the summer of 1862.  Based on three months of observations it was predicted to return after 120 years in 1982. After it failed to appear more work was done to refine the orbit, and to check for past appearances of the comet.  Sure enough comets appearing to fit the orbit were found in 188 CE and 69 BCE, so a new prediction for the comet to reappear was made for 1992 by the late Dr. Brian Marsden of the Smithsonian Astrophysical Observatory.  His revised prediction was only off by 17 days.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Orbit of Comet 109P/Swift-Tuttle. Blue line is the comet’s orbit, coming from above (North). Credit NASA / JPL / Applet by Osamu Ajiki (AstroArts), and further modified by Ron Baalke (JPL).

 

Orbit of Comet 109P/Swift-Tuttle. Blue line is the comet’s orbit, coming from above. That’s why the radiant is so far north.  See yesterday’s post for the radiant point. Credit NASA / JPL / Applet by Osamu Ajiki (AstroArts), and further modified by Ron Baalke (JPL).

These were generated a couple of years ago.  However the comet won’t be back until 2122 give or take.

08/10/2015 -Ephemeris – The Tears of St. Lawrence

Ephemeris for Monday, August 10th.  The Sun rises at 6:39.  It’ll be up for 14 hours and 17 minutes, setting at 8:56.   The Moon, half way from last quarter to new, will rise at 3:55 tomorrow morning.

Today is the Catholic Church’s feast of Saint Lawrence a deacon, who was martyred around 258.  I make reference to this because of the Perseid meteor shower which will reach peak early Thursday morning.  It is also known as the Tears of St Lawrence or St Lawrence’s Fiery Tears because the meteor shower comes near the date of the feast.  We know these meteors as the Perseids because the appear to come from just off the constellation of Perseus the hero in our northern sky.  Small bits of rocky material are the meteoroids that have been shed from Comet Swift-Tuttle on its previous passes near the sun strike the Earth’s atmosphere.  Since the comet’s orbit nearly crosses the Earth’s orbit we pass through this ring of debris every year.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Perseid meteor shower radiant a about 2 a,m, during the period of the shower. Created using my LookingUp program.

My best Perseid photo. From the 70’s.

 

08/03/2015 – Ephemeris – The Perseids are coming!

Ephemeris for Monday, August 3rd.  The Sun rises at 6:30.  It’ll be up for 14 hours and 35 minutes, setting at 9:06.   The Moon, half way from full to last quarter, will rise at 10:58 this evening.

After the Moon sets in the evening and morning hours for the next week and a half the numbers of meteors visible will increase each night.  These are members of the Perseid meteor shower of August.  The peak this year is expected to be during the 2 o’clock hour on the morning of the 13th.  These meteors are the result of debris left in the orbit of Comet Swift-Tuttle shed by innumerable visits to the inner solar system.  Every year at this time the Earth passes through this trail of debris which intersects its orbit giving rise to the meteor shower.  We call them the Perseids, because the appear to come from the direction of the constellation Perseus the hero, which is first seen in the early evening low in the northeast.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Perseid radiant at 10:30 p.m.

Orbit of Comet 109P/Swift-Tuttle. Blue line is the comet’s orbit, coming from above (North). Credit NASA / JPL / Applet by Osamu Ajiki (AstroArts), and further modified by Ron Baalke (JPL)

The distances in the lower left corner are the comet’s current distances from the Earth and Sun.  AU is astronomical units the mean distance between the Earth and Sun.  The comet’s last pass through the inner solar system was in 1992.  Swift-Tuttle is now out just past the current position of the dwarf planet Pluto.  Link to the animation from which the above image was taken and other information on Comet Swift-Tuttle go to http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=109P;cad=1

08/12/2014 – Ephemeris – Comet Swift-Tuttle progenitor of the Perseid meteors

Ephemeris for Tuesday, August 12th.  The sun rises at 6:41.  It’ll be up for 14 hours and 11 minutes, setting at 8:52.   The moon, 2 days past full, will rise at 9:50 this evening.

The Perseid meteor shower will reach its peak later this evening.  The moon will still interfere with all but the brightest meteors.  The meteors are caused by bits of sand grain to pea sized rubble given off by Comet Swift-Tuttle on past runs through the inner solar system.  As comets go Comet Swift-Tuttle is large, with a nucleus of some 16 miles  (26 km) in diameter.  Comet Halley’s nucleus is half that and Churyumov–Gerasimenko’s nucleus that ESA’s Rosetta spacecraft is now orbiting is half Halley’s.  Despite the wear and tear that a comet’s nucleus must endure when coming close to the Sun, the distribution of debris to give us a pretty even annual meteor shower means the comet has been near its present orbit for a very long time.
Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Orbit of Comet 109P/Swift-Tuttle. Blue line is the comet’s orbit, coming from above. Credit NASA / JPL / Applet by Osamu Ajiki (AstroArts), and further modified by Ron Baalke (JPL)

Link to the animation from which the above image was taken and other information on Comet Swift-Tuttle go to http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=109P;cad=1

08/07/2012 – Ephemeris – the comet responsible for the Perseid meteor shower

Ephemeris for Tuesday, August 7th.  The sun rises at 6:36.  It’ll be up for 14 hours and 22 minutes, setting at 8:59.   The moon, 2 days before last quarter, will rise at 11:20 this evening.

The Perseid meteor shower is so named because the meteors seem to come from the direction of the constellation of Perseus which starts in the evening low in the northeast and rotates up throughout the night higher and higher.  The comet responsible is Comet Swift-Tuttle, discovered in 1862 by Lewis Swift and Horace Tuttle.  The comet has a 130 year orbit and returned in 1992.  It’s orbit intersects ours at a 113 degree angle, which is why the radiant point is so far north.  The Perseids have been recorded for 2,000 years so the comet has been around much longer than that.  It’s nucleus is 17 miles in diameter, about twice that of Halley’s Comet.  While Comet Swift-Tuttle won’t be back this century, we can see bits of it tonight.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.