Neptune at Opposition

Today the planet Neptune will pass through opposition, directly opposite the Sun in our sky. The planet will be well placed for observation all night long, rising at sunset, transiting at midnight, and setting at sunrise. If you are looking to observe Neptune, it is currently shining at magnitude 7.8 in eastern Aquarius.

Neptune from Voyager 2
Neptune from Voyager 2, Credit: NASA /JPL

As the outer planets Uranus and Neptune move so slowly across the sky, the timing of oppositions is driven by the Earth’s orbit and occur each year at nearly the same time. Neptune’s orbital period is 164.8 years, taking over a century and a half to circle the celestial globe once. As Neptune was discovered in 1846, it has completed a little over one orbit since discovery.

Neptune at Opposition

Today the planet Neptune will pass through opposition, directly opposite the Sun in our sky. The planet will be well placed for observation all night long, rising at sunset, transiting at midnight, and setting at sunrise. If you are looking to observe Neptune, it is currently shining at magnitude 7.8 in the center of the constellation Aquarius.

Neptune from Voyager 2
Neptune from Voyager 2, Credit: NASA /JPL

As the outer planets Uranus and Neptune move so slowly across the sky, the timing of oppositions is driven by the Earth’s orbit and occur each year at nearly the same time. Neptune’s orbital period is 164.8 years, taking over a century and a half to circle the celestial globe once. As Neptune was discovered in 1846, it has completed a little over one orbit since discovery.

Saturn at Opposition

Today the planet Saturn will pass through opposition, directly opposite the Sun in our sky.

Saturn
Saturn on April 15th, 2016

Saturn orbits the Sun once every 29.45 years. As the ringed planet continues on its way the Earth swings around much faster on our inside track. As a result we lap Saturn once every 378.1 days, passing between the planet and the Sun. During opposition Saturn will be well placed for observation all night long, rising at sunset, transiting at midnight, and setting at sunrise.

During opposition the planet and rings will be slightly brighter than normal, an effect known as the opposition effect. The effect is most notable in the rings where the apparent brightness can increase by 30%. The effect is a combination of two factors, shadow hiding and the retro-reflective properties of the ring particles.

Jupiter at Opposition

Jupiter will pass through opposition at 05:11HST today.

Jupiter 14Apr2016
Jupiter on April 15, 2016

Jupiter orbits the Sun once every 11.86 years. As the giant planet continues on its way the Earth swings around much faster on our inside track. As a result we lap Jupiter once every 399 days, passing between the planet and the Sun. During opposition Jupiter will rise at sunset, transit at midnight, and set at dawn. This makes the planet available for observation for the entire night.

Look for a bright object rising in the eastern sky after sunset. It is difficult to mistake for anything else, shining at it’s brightest during opposition, a brilliant -2.7 magnitude. For the remainder of the spring and much of the summer, the planet will be quite prominent in the evening sky.

Uranus at Opposition

Today the planet Uranus will pass through opposition, directly opposite the Sun in our sky. The planet will be well placed for observation all night long, rising at sunset, transiting at midnight, and setting at sunrise. If you are looking to observe Uranus, it is currently shining at magnitude 5.7 in the center of the constellation Pisces.

Uranus
The planet Uranus as it appears in a mid-sized telescope
As the outer planets Uranus and Neptune move so slowly across the sky, the timing of oppositions is driven by the Earth’s orbit and occur each year at nearly the same time. The orbital period of Uranus is 84.1 years, taking the better part of a century to circle the celestial globe once.

Neptune at Opposition

Today the planet Neptune will pass through opposition, directly opposite the Sun in our sky. The planet will be well placed for observation all night long, rising at sunset, transiting at midnight, and setting at sunrise. If you are looking to observe Neptune, it is currently shining at magnitude 7.8 in the center of the constellation Aquarius.

As the outer planets Uranus and Neptune move so slowly across the sky, the timing of oppositions is driven by the Earth’s orbit and occur each year at nearly the same time. Neptune’s orbital period is 164.8 years, taking over a century and a half to circle the celestial globe once. As Neptune was discovered in 1846, it has completed a little over one orbit since discovery.

Saturn at Opposition

Today the planet Saturn will pass through opposition, directly opposite the Sun in our sky.

Saturn 22Apr2010
Saturn with Titan above
Saturn orbits the Sun once every 29.45 years. As the ringed planet continues on its way the Earth swings around much faster on our inside track. As a result we lap Saturn once every 378.1 days, passing between the planet and the Sun. During opposition Saturn will be well placed for observation all night long, rising at sunset, transiting at midnight, and setting at sunrise.

During opposition the planet and rings will be slightly brighter than normal, an effect known as the opposition effect. The effect is most notable in the rings where the apparent brightness can increase by 30%. The effect is a combination of two factors, shadow hiding and the retro-reflective properties of the ring particles.

The Opposition Effect

It was pretty obvious, an odd bright spot in the trees below that followed the helicopter. Having educated myself on quite a few optical phenomena I knew exactly what it was I was seeing, and made a point of taking a few photographs.

Opposition Effect
A bright spot in the Puna rainforest caused by the opposition effect
The mechanism for this bright spot is remarkably simple… No shadows.

Called the opposition surge, Seeliger effect or shadow hiding this simple optical phenomena occurs when looking at rough or irregular surfaces that are directly away from the light source, usually the Sun. On an irregular surface some parts will shadow other parts, resulting in an apparent darkening of the overall surface. When looking at that part of the surface directly away from the light source no shadows are seen, making that region appear brighter.

Continue reading “The Opposition Effect”

Saturn at Opposition

Today the planet Saturn will pass through opposition, directly opposite the Sun in our sky.

Saturn 22Apr2010
Saturn with Titan above
Saturn orbits the Sun once every 29.45 years. As the ringed planet continues on its way the Earth swings around much faster on our inside track. As a result we lap Saturn once every 378.1 days, passing between the planet and the Sun. During opposition Saturn will be well placed for observation all night long, rising at sunset, transiting at midnight, and setting at sunrise.

During opposition the planet and rings will be slightly brighter than normal, an effect known as the opposition effect. The effect is most notable in the rings where the apparent brightness can increase by 30%. The effect is a combination of two factors, shadow hiding and the retro-reflective properties of the ring particles.

Vesta at Opposition

Today the minor planet 4 Vesta will pass through opposition.

4 Vesta is one of the largest objects orbiting between Mars and Jupiter, a region often referred to as the Asteroid Belt. This is the second largest asteroid, at 530km (329miles) in diameter. It is also usually the brightest asteroid that can seen by earthbound observers. When Vesta is at opposition it is bright enough to be just visible to the unaided eye, usually around 6th magnitude.

This year Vesta will reach magnitude 5.7 at opposition. This magnitude requires a dark site to view without the aid of a telescope. Precise knowledge of the location is also helpful. Given these two items it becomes possible to see an asteroid with the unaided eye.

The minor planet is currently located in Virgo about 2.5° northwest of τVir. Interestingly enough the dwarf planet 1 Ceres will be located about 2° east and a touch south of Vesta. Despite being much larger than Vesta it will be over a full magnitude dimmer at about 6.9 magnitude.

Vesta was visited by the Dawn spacecraft during 2011 and 2012. Dawn is now on course for Ceres with a planned rendevouz in February 2015.

Vesta 28May2007
Vesta (marked), Jupiter and Summer Milky Way, 40s, 17mm@f/4, fixed tripod on 28May2007