Image credit & copyright: NASA/JPL Cassini Spacecraft.
If you’re a fan of the night sky, you’ve been noticing the Saturn, Mars and Antares Trio as it’s been quite a treat for the past few months. If you haven’t seen this yet I would urge you to do so because it’s a fantastic view that’s peaking right now. Beauty aside, they’re also a big trio. Mars hit opposition a couple weeks ago and on May 30 reached its closest point to Earth in 11 years. Well now it’s Saturn’s turn as its hitting opposition this Friday, June 3, 2016. Saturn reaches opposition every year or 378 days or 54 weeks and this opposition will bring Saturn to 9 AU (AU being 1 Earth/Sun distance or about 93 million miles) from Earth.
Opposition, in planetary terms is when a superior (outer) planet, dwarf planet or asteroid reaches a point almost exactly opposite the Sun from Earth’s vantage point so we see its full, bright disk. Another way to say it is Earth is directly between the Sun and that object. Opposition also places the object near its closest point that it can get to the Earth in its orbit (perigee). Technically opposition and actual perigee points usually differ from a few hours to a few weeks but again, its close enough for what we’re doing.
You may be asking why opposition doesn’t also equal perigee or that body’s closest point to Earth. Well, as I said above it pretty much does but you have to remember that orbits are elliptical and two orbits don’t mirror each other so even though a planet may be directly opposite the Sun from us, the elliptical nature of orbits usually means the actual closest points tend to be slightly before or after opposition.
You may also be asking why oppositions have different distances opposition to opposition. The reason is the same as the above paragraph, the orbits of the planets aren’t actually circular they’re slightly elliptical. For example, Mars reaches perigee (closest point to Earth) around the same time it reaches perihelion (closest point to the Sun) every 15 to 17 years. So if Mars reaches opposition at its furthest point from the Sun it will be a more distant opposition than if it were at its closest point to the Sun. Imagine if we happen to be at aphelion (Earth’s farthest point from the Sun) at the same time say, Mars is at its perihelion? What a great sight that would be!
Also, during the immediate hours of opposition look for a phenomenon known as the Seeliger Effect. You may also know this as “Opposition Surge”, “Opposition Effect” or even “Opposition Spike.” This is a sudden brightening of the planet; or in this case Saturn’s rings just before and just after opposition. You may notice that the disk of the planet doesn’t brighten; just the rings. The brightening is from the sunlight being reflected off the ice crystals in the rings as they are illuminated from almost the same direction in which we are viewing them from. This also happens with other celestial bodies including the Moon when full vs. its other phases but for slightly different reasons that include shadows etc.
Below I’ve listed the important data as well as a bunch of my favorite links to use and abuse as they’re invaluable assets for sky watching and as always, if you have questions, please ask! I don’t include Planet, Sun or Moon rise and set times because that’s different depending on where exactly you are but the resources are in the links below.
SATURN OPPOSITION 2016:
DATE: Friday, June 3, 2016.
TIME: 06:25 UTC (02:25 EDT).
WHERE IS IT? (Constellation): Ophiuchus the Serpent Bearer.
WHERE IS IT? (Exact RA/Dec J2000): RA 16h 46m 40s / Dec 20°33’15”.
APPARENT MAGNITUDE: A very bright 0.8.
APPARENT DIMENSIONS (Angular Size): 18.4” arcseconds and including rings it will be 41.7” arcseconds.
ALTITUDE: About 35 degrees for mid-northern latitudes.
DISTANCE FROM EARTH: 9 AU (An AU is 1 Earth/Sun distance or 93 million miles).
OPPOSITION FREQUENCY: Just over a year; 54 weeks or 378 days.
RING ANGLE: +26 degrees so they will be nice and open, facing us.
MOON PHASE: Waning crescent, 28 days old (nearly new).
Naked Eye Planets Saturn Location: http://www.nakedeyeplanets.com/saturn.htm
Dominic Ford’s “In-The-Sky” page for this event: https://in-the-sky.org/news.php?id=20160603_13_100
In-The-Sky’s, Solar System Body Finder Chart: https://in-the-sky.org/findercharts.php?startday=1&startmonth=6&startyear=2016&objtype=0&duration=3&objtxt=Saturn&objs=
U.S. Naval Observatory (USNO) Solar System Body Apparent Dimensions: http://aa.usno.navy.mil/data/docs/diskmap.php
U.S. Naval Observatory (USNO) Solar System Body Rise & Set Times: http://aa.usno.navy.mil/data/docs/mrst.php
The Sky Live page for Saturn: http://theskylive.com/saturn-info
The Sky Live, Saturn Tracker: http://theskylive.com/saturn-tracker
Chris Peat’s “Heavens-Above” Planet Summary: http://heavens-above.com/PlanetSummary.aspx
The Planets Today (current solar system configuration): http://www.theplanetstoday.com/
Time and Date Sunrise and Sunset calculator: http://www.timeanddate.com/sun/
Time and Date Moonrise and Moonset calculator: http://www.timeanddate.com/moon/