5 Sky Events This Week: Lunar Wall, Mars Up-Close, and a Blue Giant

This composite illustration shows Neptune as seen from its moon Triton. Neptune’s south pole is to the left; clearly visible in the planet’s southern hemisphere is the Great Dark Spot. Credit: NASA

Fantastic fault lines and planetary close encounters this week offer sky-watchers some impressive cosmic views of the heavens.

The lunar wall. The first quarter moon, which comes into view on Monday, April 7, offers the best moment this month to view, in small telescopes, an amazing lunar feature called the lunar wall, or Rupes Recta (sometimes called the Straight Wall).

In reality, the “wall” is a lunar rille, a fault line created where parts of the moon’s crust have pulled apart. The fault line stretches some 75 miles (120 kilometers) in length and more than 1,300 feet (400 meters) deep. It casts a distinct straight, dark line when seen through your eyepiece. (Read more about lunar wonders.)

The Straight Wall, or Rupes Recta, cuts across the face of the moon and is visible in small telescopes this week. Photograph courtesy JAXA/SELENE
The Straight Wall, or Rupes Recta, cuts across the face of the moon and is visible in small telescopes this week. Photograph courtesy JAXA/SELENE

Mars opposition. On Tuesday, April 8, the red planet will appear at its biggest and brightest since December 2007. Known as opposition, when Mars appears opposite in our skies from the sun, the distinctly orange-hued starlike object will rise in the east as night falls. By 1 a.m. local time, the planet will appear near the overhead southern sky in the constellation Virgo, the Maiden.

High-magnification views of Mars through backyard telescopes will show surface features like its ice-covered northern polar cap. Stay tuned for more details.

Earlier on Tuesday, the moon will reach its farthest distance from the Earth for the month, a position known as lunar apogee. At that time, the moon will orbit 251,344 miles (404,500 kilometers) from the center of our planet.

Moon and Regulus. As evening settles in on Thursday, April 10, look high in the southern sky for the waxing gibbous moon, which will hang below the “heart” of constellation Leo.

The blue-white star, Regulus, appears just over 5 degrees from the moon, equal to the width of three middle fingers held at arm’s length.

Venus and Neptune. At dawn on Saturday, April 12, telescope-equipped sky-watchers can try a real observing challenge—tracking down the distant planet Neptune very low in the eastern sky. This morning it will be a bit easier to locate, thanks to its proximity in the sky to a brilliant Venus. The two worlds will appear just 0.7 degrees apart (a bit more than the width of the full moon), easily fitting into a single field of view through a telescope eyepiece.

Follow Andrew Fazekas, the Night Sky Guy, on Twitter, Facebook, and his website.

Changing Planet

Meet the Author
Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.