Highlights of the Season: April-June 2020

The best of the springtime meteor showers peaks on April 22 and is favored by the new Moon.

The Lyrid meteor shower is known from Chinese records dating back to 687 BC, when meteors were described as "falling like rain." It occurs when Earth barrels through a stream of sand-sized dust particles along the trail of Comet Thatcher and the particles burn up as they plow through the atmosphere. At its peak, the shower produces an average of 10-15 meteors per hour, generally about the brightness of the North Star. They appear to radiate from the constellation Lyra the Harp, hence the shower's name. Typically, the best time of the night to watch for a meteor shower is between midnight and the start of morning twilight, when Earth's rotation has carried observers around to face the incoming dust stream. Weather-permitting, this year's moonless conditions on the 22nd assures optimal predawn viewing, especially away from city lights.

A 47-year-old annual celebration of skywatching and space science takes place this year on May 2. Founded in 1973 by the Amateur Astronomers of Northern California, National Astronomy Day has grown into a worldwide observance, held on a Saturday nearest the first quarter Moon in either April or May, so if nothing else—weather-permitting—the Moon itself provides skywatchers with something to look at.

As seen through a telescope, at two days past first quarter, the long, sharp shadows of craters and mountains along the terminator (the edge of the Moon's daylit side) show off the Moon's dramatic surface relief. Visible on this night are dark patches that form the Seas of Serenity, Tranquility, Fertility, and Nectar and the isolated Sea of Crises. Near the edge of the terminator are the two prominent rayed craters, Copernius in the northern hemisphere and Tycho in the southern hemisphere.

One of two meteor showers caused by dust particles from Halley's Comet burning up in the atmosphere, the Eta Aquarid meteors are active from April 19-May 28 and peak on the morning of May 5.

But only two days before the full Moon, you can expect the light of the waxing gibbous, which is visible all night, to obscure many meteors from view. This will reduce the number seen from the optimal 20 per hour to five or fewer. In addition, the shower's radiant (the point in the sky from which meteors seem to emanate) is located in Aquarius the Water-Carrier, which is quite low in the southern sky and not very high above the horizon by the time morning twilight begins for observers in the northern hemisphere.

June 20, 2:43 pm PDT: This is Summer solstice for the northern hemisphere and winter solstice for the southern hemisphere, where the seasons are reversed. To avoid confusion, some prefer to say June solstice, which applies regardless of location.

For observers north of the equator, the Sun rises and sets farthest north, reaching its highest point in the sky at midday, putting it above the horizon for the longest time for the year (for San Francisco, that's 14 hours 47 minutes).

At the north pole, the Sun is in the sky for 24 hours, located 23.5 degrees above the horizon and circling around parallel to it, causing 24 hours of daylight. From day to day, the Sun slowly spirals lower toward the horizon and doesn't finally set until shortly after the September equinox.

On the Tropic of Cancer (23.5 degrees north latitude), the Sun's highest point in the sky is directly overhead at local solar noon.

On June 20, the third of this year's six eclipses occurs, an annular solar eclipse which is seen when the Moon moves between Earth and the Sun—but unlike a total solar eclipse, the Moon is a little farther away, so it appears smaller and doesn't completely block the Sun from view, revealing our star's ghostly corona, or outer atmosphere. Instead, it leaves a visible ring of the Sun's disk, or annulus, visible around it. This ring is bright enough to obscure the corona, so it does not become visible. Because of this, annular eclipses aren't quite as spectacular as total eclipses, but they're still awe-inspiring to witness! This event will not be observed from any part of the US, since it happens when the Sun is below the horizon for us, but it will be seen from parts of Africa including the Central African Republic, Congo, and Ethiopia, south of Pakistan and northern India, and China.