This is Dudley Observatory’s Skywatch Line for Friday, July 27 through Sunday, July 29, written by Sam Salem.
On Friday, the Sun rises at 5:42am and sets at 8:22pm; Moon sets at 5:23am and rises at 8:23pm. Full Moon occurs at 4:20pm on Friday. This is the smallest full Moon of 2018 as the Moon is also at apogee, or farthest point in its orbit around the Earth. Total eclipse of the Moon occurs on Friday but not for the Americas. This will be the longest total lunar eclipse of the 21st century with totality lasting 1 hour 43 minutes. The eclipse will be viewed in Europe, Africa, and much of Asia. The Moon, orbiting Earth, is in opposition to the Sun at full Moon. When Moon is in exact opposition, a lunar eclipse occurs.
Mars reached opposition Thursday night. However, Mars will be closest to Earth, and its absolute biggest and brightest on the night of July 30-31. A planet is in “opposition” when it is opposite to the Sun as seen from Earth. Opposition occurs for superior planets orbiting outside Earth’s orbit. These planets are Mars, Jupiter, Saturn, Uranus, Neptune, and dwarf planets. A planet in opposition is visible almost all night, rising around sunset, culminating around midnight, and setting around sunrise. Opposition occurs at the point in planet’s orbit where it is roughly closest to Earth, making it appear larger and brighter.
The evening sky features four of bright planets along the ecliptic from west to east. Westernmost is the “evening star” Venus at magnitude –4.2. Jupiter, at magnitude –2.1, shines in the south-southwest at dusk and sets a little before 1am. Saturn, at 0.2-magnitude, transits the meridian at roughly 10:45pm, when it’s due south and in prime position for telescopic inspection. Mars outshines Jupiter, gleaming at magnitude –2.8. Mars is visible all night and highest in the south at around 1:00am. Mars will maintain its peak size of 24.3 arcseconds for about a week around its closest approach on the night of July 30-31. The dust that still cover the Martian globe has started to thin, allowing faint, low-contrast views of some dark surface features.
The first large, stable mass of liquid water has been detected on Mars. An Italian team using ground-penetrating radar found a 12-mile wide lake about a mile beneath the planet’s southern ice cap. There has been evidence of recent water activity but never of stable bodies of water. The team discovered the lake while analyzing a radar survey that was done between 2012 and 2015 by the Mars Express orbiter spacecraft.
Friday is the grand opening of the new observatory building at miSci. The new observatory holds a modern 14-inch telescope. The celebration will run from 6:00 pm to 11:00 pm with solar observing, Night sky observing, hands on activities, and Planetarium shows. Check the Dudley Observatory website for more information. http://dudleyobservatory.org/observatory-at-misci/