When 50% of the solar surface area is obscured, the eclipse magnitude is roughly 60%.Įclipse season: The 35 days when the Sun is close enough to one of the nodes of the Moon's orbit (that is, the two points at which the Moon's orbit around Earth crosses the plane of Earth's orbit around the Sun) for an eclipse to occur.Įcliptic: The plane of Earth's orbit around the Sun or, equivalently, the plane of the Sun's apparent motion around the sky throughout the year. Do not confuse it with eclipse magnitude (see previous item). When the eclipse magnitude is 50% (that is, when 50% of the Sun’s diameter is covered), only about 40% of the solar surface area is obscured.Įclipse obscuration: The fraction of the Sun’s surface area covered by the Moon. It is a ratio of Sun/Moon diameters and should not be confused with eclipse obscuration (see next item). It’s the signal that totality is about to start (second contact) or has ended (third contact).ĭuration: The time between second and third contact during a total or annular solar eclipse.Įclipse magnitude: The fraction of the Sun’s diameter covered by the Moon. Its shape (sometimes elongated, sometimes round) is determined by the Sun’s magnetic field and is linked to the sunspot cycle.ĭiamond ring: A single Baily’s Bead, shining like a brilliant diamond set into a pale ring created by the pearly white corona. It is briefly visible immediately after second contact and just prior to third contact at a total solar eclipse.Ĭorona: The Sun’s upper atmosphere, visible as a pearly glow around the eclipsed Sun during totality. They’re named after the English astronomer Francis Baily, who first described them during the annular eclipse of May 15, 1836.Ĭhromosphere: A thin, red-colored layer of solar atmosphere located just above the photosphere. They appear just prior to second contact and just after third contact at annular and total solar eclipses. An observer standing in the antumbra sees an annular eclipse.īaily’s beads: Caused by shafts of sunlight shining through deep valleys on the lunar limb (edge), they look like a series of brilliant beads popping on and off. Within the antumbra, the Sun appears larger than the Moon, which is visible in silhouette. It can last from a fraction of a second to a maximum of 12 minutes 30 seconds.Īntumbra: The extension of the Moon’s shadow beyond the umbra. Annularity occurs between second and third contact. At mideclipse, the Sun appears as a blindingly bright ring, often called a "Ring of Fire," encircling the Moon.Īnnularity: The maximum phase of an annular eclipse, when the Moon’s entire disk is seen silhouetted against the Sun. You’ll find many of them used throughout this website and will encounter others on other sites and in the media as we get closer and closer to the August 21, 2017, solar eclipse across America.Īnnular eclipse: A solar eclipse where the apparent diameter of the Moon is too small to completely cover the Sun. The following are a number of terms used to describe various aspects of solar eclipses.
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