On the night of Sunday, January 20, 2019, a total lunar eclipse will be visible from all 50 U.S. states. It’s been over three years since lunar totality has been seen across such a wide swath of the country. Of course, more recently, the U.S. witnessed a total eclipse of the solar variety, in August of 2017. People sometimes confuse the difference between solar eclipses and lunar eclipses, so with January 20 right around the corner, let’s discuss what a lunar eclipse is, what makes it special, and how it compares to a solar eclipse.
A lunar eclipse occurs when the Sun, the Earth, and the Moon are aligned and the Earth casts a shadow across the Moon that can be seen by a viewer on Earth. During a total lunar eclipse, the Sun, the Earth, and the Moon line up perfectly and the Earth’s shadow fully covers the Moon, resulting in “totality”; in a partial lunar eclipse, the Sun, the Earth, and the Moon are not perfectly aligned and the Earth’s shadow covers only part of the Moon; and during a penumbral lunar eclipse, only the faint outer edge of the Earth’s shadow falls on the Moon.
As is the case with solar eclipses, you’ll get the most thrill and bang for your astronomical buck when a lunar eclipse is total. Although certainly not as awe-inspiring and even life-changing as a total solar eclipse, a total lunar eclipse is definitely worth making an effort to see at least once.
A partial lunar eclipse is certainly interesting, as the shadow of the Earth is quite distinctive as it slowly moves across the Moon. But it’s probably not as impressive as the Sun being gobbled up by the Moon during a partial solar eclipse.
As for a penumbral lunar eclipse, don’t expect to see much. If you’re lucky, you might notice a very slight dimming of the lunar disc. If the eclipse occurs late at night, it’s probably not worth staying up for unless you’re an obsessive eclipse chaser.
Unlike during a total solar eclipse, when totality is visible from Earth only along a very narrow path, a total lunar eclipse can be seen by almost everyone on the nighttime side of the Earth. Although total lunar eclipses aren’t necessarily more common than total solar eclipses, the extremely wide viewing area means that while most people will never see a total solar eclipse in their life, almost everybody on Earth will have multiple opportunities to see a total lunar eclipse right from their own homes.
What’s more, while totality is visible along the eclipse path for just a few short minutes during a total solar eclipse, a total lunar eclipse can last for up to almost two hours. And while a solar eclipse requires special eclipse safety glasses or viewers, a lunar eclipse can be viewed safely with just the naked eye. All of these reasons make lunar eclipses much more accessible to the casual viewer than solar eclipses.
A total lunar eclipse is sometimes referred to as a “blood moon” due to the reddish tint exhibited by the Moon during totality. Although the Earth blocks all direct sunlight from striking the Moon, a small amount of indirect light reaches the Moon after passing around the edge of the Earth. After Earth’s atmosphere filters and refracts this light, scattering non-red wavelengths, it’s reflected back from the Moon to the Earth with a reddish hue. This occurs for the same reason that the sky turns red during a sunrise or sunset. The reddish tint of the Moon can be more or less noticeable depending on the amount of dust and particles in the atmosphere when an eclipse occurs. A total lunar eclipse occurring shortly after a volcanic eruption, for example, can result in a very bright red blood moon.
As mentioned, it’s not uncommon for people to confuse the difference between a solar eclipse and a lunar eclipse but the two are entirely different astronomical events. A solar eclipse is the obscuration of the Sun by the Moon; a lunar eclipse is the obscuration of the Moon by the Earth. The name of the eclipse type (solar or lunar) refers to the body being obscured. A lunar eclipse can only occur during a full Moon, when the Moon is on the opposite side of the Earth from the Sun; a solar eclipse can only occur during a new Moon, when the Earth is on the opposite side of the Moon from the Sun.
On Sunday, January 20, 2019, the partial phase of the eclipse will start at about 10:33pm ET, with totality beginning at about 11:41pm ET and lasting for a little over an hour. The eclipse timeline is the same wherever it’s viewed, so simply adjust those times for your own local time zone.
Last year, America went eclipse crazy. As the first major widespread eclipse event in the U.S. since then, this upcoming eclipse will surely generate more excitement than usual. If you’ve never seen a total lunar eclipse before (or even if you have), hope for a cloud-free sky on the night of Sunday, January 20, 2019, and treat yourself to totality.
Visit NationalEclipse.com for more about eclipses, including information on the next total solar eclipse coming to America on April 8, 2024.