Tonight is the total lunar eclipse! This month’s full moon is going to be directly lined up with the Earth and the sun, so the moon will travel through the umbra of the Earth’s shadow, the region of total shadow.
Though the moon takes about a month to orbit the Earth, it usually misses the Earth’s shadow because the moon’s orbit is tipped by 5 degrees with respect to the Earth-sun line. At a distance of 240,000 miles, that 5-degree angle is plenty big enough to miss the shadow.
Every now and then the full moon happens just as the moon is crossing the Earth-sun plane and we get an eclipse. In 2020, there were no total lunar eclipses visible. Last year, we had one that was visible — a short one (just 18 minutes of totality) in the pre-dawn morning. This year, we’ll be able to see two total lunar eclipses and tonight’s will be a long one (1 hour 25 minutes of totality) visible not too late in the evening.
As the moon rises tonight shortly before 8 p.m., it will already have begun moving into the umbra. The moon moves eastward with respect to the stars, so you’ll see the dark edge of the umbra slowly move rightward as the moon gets higher in the sky. Totality begins at 8:29 p.m. (8:28:40 to be more precise) and will last until 9:54 p.m. (more precisely 9:54:11). The moon will be low in the southeast during totality, ranging from two finger widths at arm's length at the start to two fists at arm's length at the end of totality.
What color will the moon be during totality? Because of Earth’s atmosphere, the orange and red colors of sunlight are able to bend around the Earth and reach the moon even though the moon is in total shadow. The shorter wavelength colors such as the greens, blues and purples get scattered away. The total eclipsed moon will take on an orange, red or even a brown color depending on how much dust there is in our atmosphere globally. A lot of dust from a volcanic eruption that has had time to spread around the globe can make the total eclipsed moon appear a dark brown, almost black, while a global dust-free atmosphere will make the moon have a light orange color.
If you’re on the west side of town, join the Kern Astronomical Society at The Park at River Walk in the main parking lot, east of the lake at Buena Vista and Stockdale Highway! They will have their telescopes set up between 8 and 10 p.m. to look at the moon as well as other celestial objects, such as the M13 globular cluster in Hercules. Of course, you don’t need a telescope to enjoy the lunar eclipse, but it is a pretty darn cool sight in a telescope or pair of binoculars!
Eye on the planets
Early morning risers will see a line of four bright planets in the southeastern sky starting about 4:35 a.m. By then, Venus will have risen to complete the quartet. From lowest to highest (as well as brightest to dimmest), it will be Venus, Jupiter, Mars and Saturn. Jupiter is just beyond the midway point between Venus and Mars, closer to Mars. Over the rest of May, you’ll see Jupiter and Mars draw closer and closer together for their May 29 conjunction.
Impatient for Webb observations
The James Webb Space Telescope now has its mirrors all perfectly aligned. The next stage in the commissioning process is to prepare and test the instruments, which will take about two months. The first science images and spectra will be coming this summer.
The engineering images of a part of a satellite galaxy of the Milky Way (our home galaxy), called the Large Magellanic Cloud, confirmed that the mirrors are all perfectly aligned for the four different instruments of Webb. They also hint at the great power of this space telescope.
However, I’m impatient to get to the science! Why does it take so darn long to get the telescope ready for science operations? It’s because true science is not a Hollywood movie; physical reality is more complex and surprising than virtual reality.
Doing cutting-edge science takes a certain kind of humility and respect for nature. We test and test and then test again. Very often we make a lot of mistakes along the way, not taking something into account that in hindsight seems obvious, and we know that mistakes are going to be made. Since we know that we’re fallible and have limited knowledge, the scientific method and engineering’s design-to-commissioning process we’ve created have built into them a lot of checking, rechecking, peer review, incremental steps, etc.
We don’t put all our eggs in one basket, so to speak, by building something and turning it on for the first time in the field with the hope that it works as the computer model says it should. No, the real universe is not a Hollywood movie where everything works correctly the first time.
So, yeah, I’m impatient but I’ll cope with it as I wait for those first science observations from Webb.