Tonight – August 29, 2017 – use the moon to find Saturn, the 6th planet outward from the sun. Saturn now shines in front of the constellation Ophiuchus, sometimes called the forgotten constellation of the zodiac. Find out more about Ophiuchus on our Tonight post for August 13.
Saturn is the most distant world that you can easily see with the unaided eye. Moreover, you can view Saturn’s majestic rings with nothing more than a modest backyard telescope. Even though the four outer planets (planets orbiting the sun outside the asteroid belt) – Jupiter, Saturn, Uranus and Neptune – have a ring system of sorts, Saturn’s rings are the most spectacular by leaps and bounds.
This year, in 2017, the north side of Saturn’s rings are maximally tilted toward Earth. So right now is a great time to dust off that telescope and gaze at Saturn, the crown jewel of the solar system.
The four outer planets – Jupiter, Saturn, Uranus and Neptune – are gas giants, though Uranus and Neptune are sometimes referred to as ice giants. Overall, gas giant and ice giant planets have no solid surfaces. The smaller four inner planets with solid surfaces – Mercury, Venus, Earth and Mars – are called terrestrial or rocky planets.
There are no rings around any terrestrial solar system planet at present. Is there some reason why gas and ice giants have rings whereas terrestrial planets don’t? Cathy Jordon speculates at Cornell University’s Ask an Astronomer site.
However, it’s thought that Mars’ inner moon Phobos may break up into a ring some 50 million years from now. That’s because this moon is below the synchronous orbit radius – the distance at which the moon orbits Mars in the same time period that Mars rotates upon its axis. Because Phobos’ orbit is unstable, this moon is slowly but surely plunging toward its day of reckoning.
Speculation of planetary ring systems aside, let tonight’s moon guide you to Saturn, and if you have a telescope, use it to get an eyeful of Saturn’s marvelous rings.