October 23, 2017

AstroEvent: The Return of Saturn 2011.

Saturn as imaged March 19th, 2004 by the author.

 Two of unique planetary events are on our astro-radar this week. The first is an extremely close conjunction between brilliant Venus and faint Neptune on the morning of March 27th. At a mere 9’ minutes separation at 0100 UT, this will be one of the closest planetary conjunctions of the year. Ever wondered what Venus would look like with a moon, or perhaps what might have spurred those old Neith sightings in the 19th century? Now is your chance to catch nearby Neptune if seeing permits. Viewers in central Asia longitudes will have the best shot; Venus is a fast mover and the two will be about 30’ apart by the time that US East Coast viewers get a look later the same morning. Venus is now displaying a gibbous phase & will provide an easy, if dazzling guide post to locate faint Neptune at magnitude +8.0.

Fast forward to the evening of April 3rd, when the planet Saturn reaches opposition. A star party staple, this heralds the planets’ return to favorable evening viewing, as the rings are currently tipped open by about 9° degrees from our line of sight and the planet shines at +0.4 magnitude in the constellation Virgo. This also marks a personal watershed, as I remember first starting to observe the ringed world as a teenager with my new 60mm refractor as it sat in the same constellation, 29 years ago… we’ve been exploring the universe for precisely one Saturnian year!

The Astronomy term for this week is the Seeliger Effect. This is the apparent brightening of a planet in days leading up to opposition, and was first noted by Hugo von Seeliger in the late 1800’s. Sometimes also referred to as the opposition effect, this phenomenon is especially notable in the case of Saturn, and Seeliger himself attributed it to the loss of shadow casting by the individual particles in the ring system as seen from our vantage point. Current thoughts on the Seeliger Effect stem from the concept of the coherent backscattering of light, again seen face on from our vantage point during opposition. You see this same phenomenon in action after a glittering fresh snowfall, and reflective street signs also utilize the same effect. An interesting project would be to photograph Saturn on successive nights leading up to and after opposition, and perhaps catch the Seeliger Effect in action. Good luck, and we always love to see those images!

Trackbacks

  1. [...] interesting phenomenon to watch out for near opposition is known as the Seeliger effect. Also sometimes referred to as the “opposition surge,” this sudden brightening of the disk and [...]

  2. [...] of the planet in early June, known as an ‘opposition surge’ due to what is known as the Seeliger effect. This is a coherent back-scattering of light, focusing it similar to highway retro-reflectors [...]

  3. [...] of the planet in early June, known as an ‘opposition surge’ due to what is known as the Seeliger effect. This is a coherent back-scattering of light, focusing it similar to highway retro-reflectors [...]

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