Alan MacRobert, Senior Editor
617-864-7360 x22151, macrobert@SkyandTelescope.com
(Nights, weekend: 781-275-9261)
J. Kelly Beatty, Senior Editor
617-864-7360 x22168, kbeatty@SkyandTelescope.com
|Note to Editors/Producers: This release is accompanied by high-quality graphics; see the end of this release. For more information, please direct your readers/viewers to our online story about the eclipse (not to this press release). Also, please direct your audience to our live, expertly narrated live lunar-eclipse webcast.
Everything is lining up beautifully for the last total lunar eclipse until 2018. Plan now for Sunday night.
If the sky is clear after sunset this Sunday (September 27, 2015), plan to head outside to see the last total eclipse of the Moon that we'll get for more than two years.
This eclipse promises to be a grand one. First, it happens during convenient evening hours for North Americans, with the Moon nicely placed for viewing in the eastern sky. And it happens when the Moon is very near the "supermoon" point of its orbit, where it's closest to Earth (called perigee). The year’s closest lunar perigee occurs just 59 minutes before mid-eclipse. The Moon will appear 13% larger in diameter than it did when eclipsed last April 4th. That may not be enough for anyone but dedicated Moon watchers to notice, but for a spectacle like this, every bit helps.
Easterners can watch every stage of the eclipse in late twilight and darkness, with the Moon (in the constellation Pisces) mostly high in the east. If you're in the Far West, the first partial stage of the eclipse is already in progress when the Moon rises (due east) right around the time of sunset.
The eclipse is also visible from South America later in the night local time, and from Europe and much of Africa in the early-morning hours of Monday the 28th local time.
See the table and diagram below for times of key events during the eclipse. The stages of the eclipse occur simultaneously for everyone who can see the Moon, but the clock times depend on your time zone:
|Key Times for Total Lunar Eclipse, Sept. 27–28, 2015|
|Eclipse event||UT (GMT)
|Penumbra first visible?||00:40||8:40 p.m.||7:40 p.m.||—||—|
|Partial eclipse begins||01:07||9:07 p.m.||8:07 p.m.||7:07 p.m.||—|
|Total eclipse begins||02:11||10:11 p.m.||9:11 p.m.||8:11 p.m.||7:11 p.m.|
|Mid-eclipse||02:47||10:47 p.m.||9:47 p.m.||8:47 p.m.||7:47 p.m.|
|Total eclipse ends||03:23||11:23 p.m.||10:23 p.m.||9:23 p.m.||8:23 p.m.|
|Partial eclipse ends||04:27||12:27 a.m.||11:27 p.m.||10:27 p.m.||9:27 p.m.|
|Penumbra last visible?||04:55||12:55 a.m.||11:55 p.m.||10:55 p.m.||9:55 p.m.|
With its wide visibility, convenient evening schedule, and record size, this eclipse is going to get a lot of publicity.
And if your sky is cloudy (or you're on the wrong side of the world), you can watch the slow progression of this dramatic celestial event via Sky & Telescope's live webcast.
A lunar eclipse happens when the Sun, Earth, and Moon form a near-perfect lineup in space. The Moon gradually glides into Earth's shadow, until the Moon's entire face turns from white to an eerie dim orange or red. The total phase of the eclipse will last 1 hour and 12 minutes, with its midpoint at 10:47 p.m. EDT. Then events undo themselves in reverse order, until the Moon returns to full brilliance. The whole process takes more than 3 hours.
You only need your eyes to see the drama unfold, but if you have binoculars or a backyard telescope, they'll give a much-enhanced view.
What to Look For
The events that happen to a shadowed Moon are more complex and interesting than many people realize. A total lunar eclipse has five stages, with different things to watch for at each.
The first penumbral stage begins when the Moon’s leading edge enters the pale outer fringe of Earth’s shadow: the penumbra. But the shading is so weak that you won’t see anything of the penumbra until the Moon is about halfway across it. Watch for a slight darkening to become apparent on the Moon’s celestial east side: its lower left side as seen from North America.
The penumbra is the region where an astronaut standing on the Moon would see Earth covering only part of the Sun’s face. The penumbral shading becomes stronger as the Moon moves deeper in.
The second stage is partial eclipse. This begins much more dramatically when the Moon’s leading edge enters the umbra: Earth’s inner shadow where the Sun is completely hidden. With a telescope, you can watch the edge of the umbra slowly engulfing one lunar feature after another, as the entire sky begins to grow darker.
The partial phase will last just over an hour. As its end approaches, only a final bright sliver remains outside the umbra. By this time the rest should already be showing a dim, foreboding reddish glow.
The third stage is total eclipse, beginning when the last rim of Moon slips into the umbra. But the Moon won’t black out: it’s sure to glow some shade of intense orange or red.
"That red light you see is sunlight that has skimmed and bent through Earth's atmosphere and continued on through space to the Moon," says Alan MacRobert of Sky & Telescope magazine. "In other words, it's from all the sunrises and sunsets that ring the world at the moment.
"Picture it from the point of view of an astronaut standing on the Moon," says MacRobert. "They would see the dark Earth in the sky thinly ringed with brilliant orange from the Sun hidden behind it. The ring is bright enough to illuminate the ground at the astronaut's feet an eerie red."
The red umbral glow can be quite different from one eclipse to the next. Two main factors affect its brightness and color. The first is simply how deeply the Moon goes into the umbra as it passes through; the center of the umbra is much darker than its edges.
The other factor is the state of Earth’s atmosphere along the sunrise-sunset line. If the air is very clear, the eclipse is bright. But if a major volcanic eruption has recently polluted the stratosphere with thin global haze, a lunar eclipse will be dark red, ashen brown, or occasionally almost black.
In addition, blue light is refracted through Earth’s clear, ozone-rich upper atmosphere above the thicker layers that produce the red sunrise-sunset colors. This ozone-blue light tints the Moon also, especially near the umbra’s edge. The result can be a subtle mix of changing blue, gray, and even green.
And then, as the Moon continues eastward along its orbit, events replay in reverse order. The Moon’s edge re-emerges into sunlight, ending totality and beginning stage four: a partial eclipse again.
When all of the Moon escapes the umbra, only the last, penumbral shading is left for stage five. By about 30 or 40 minutes later, nothing unusual remains.
We’ll have more than two years’ wait until the next total eclipse of the Moon, on January 31, 2018. And that one will be visible only from the Eastern Hemisphere and the western side of North America.
For more skywatching information and other astronomy news, visit SkyandTelescope.com or pick up Sky & Telescope, the essential magazine of astronomy since 1941.
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