Jupiter at its biggest and brightest! Here's how to see it
Monday, May 7, 2018, 8:00 AM - A blue moon, two meteor showers and Jupiter at its biggest and brightest. Here's what to watch for in the night sky in Spring of 2018!
With the weather warming up as we head into spring, there are a few interesting things to check out in the night sky.
March 30-31 - 2018's second Blue Moon
April 21-23 - the peak of the Lyrid Meteor Shower
May 4-5 - the peak of the eta Aquariid Meteor Shower
• May 8-9 - Jupiter at Opposition
(Visit our Complete Guide to Spring 2018 for an in depth look at the Spring Forecast, tips to plan for it and much more.)
May 8-9 - Jupiter at Opposition
On the night of May 8-9, the planet Jupiter will be at its biggest and brightest in our night sky, as it reaches Opposition - the point in its orbit when it is on the exact opposite side of Earth from the Sun.
Jupiter at around 1 a.m. local time, on the night of May 8-9, 2018. Credit: Stellarium/Scott Sutherland
The closest point between Earth and Jupiter is actually a few days after Opposition, just due to a quirk of our orbits, so there are a few days here when we'll have a big, bright Jupiter.
Viewing the planet is still best done with a telescope, or at least a good pair of binoculars. Otherwise, it simply appears as an exceptionally bright star to the naked eye. Look through a telescope, though, and you will be able to see the four Galilean moons of Jupiter - Io, Europa, Ganymede and Callisto.
Throughout the spring, watch the night sky for when various planets team up, and even line up with the Moon at times.
Of particular note are Mars and Saturn, which stick together in the sky throughout much of the season, crossing paths in early April (plus lining up with the Moon on April 7), and then pulling farther apart towards the end of the month.
(LOOKING FOR THE LATEST SPACE AND SCIENCE NEWS: Go Out of this World with science writer Scott Sutherland)
What we've already seen
March 30-31 - 'Blue Moon'
On the night of March 30 to 31, we'll see the second of 2018's two Blue Moons.
The two Full Moons of March 2018. Credit: NASA Goddard Scientific Visualization Studio/Scott Sutherland
The first Blue Moon of 2018 was the Super Blood Blood Moon, on the morning of January 31, and we're having a second one now, due to the timing, because February - with only 28 days - had no Full Moon this year.
The original definition of a Blue Moon is "the third Full Moon in a season with four Full Moons." Typically, seasons have three Full Moons, but once in awhile, when the Full Moons fall around the 18th to 22nd of the months in the season, you can have four.
Using 'Blue Moon' to describe the second Full Moon in a calendar month is actually based on a misinterpretation of the original meaning, which appeared in the March 1946 issue of Sky and Telescope magazine. The author of that article, amateur astronomer James Hugh Pruett, basically said that since some calendar years have 13 Full Moons, that must mean that there is a month with two Full Moons, and that second Full Moon must be the Blue Moon.
Unfortunately, Pruett did not account for the fact that the timing of those Full Moons is more important. So, the next "true" Blue Moon will be on May 18, 2019, since that will be the third of four Full Moons of spring that year (March 21, April 19, May 18 and June 17). However, 2019 still has only 12 Full Moons, compared to the 13 Full Moons of 2018.
Still, with the error made, Pruett's definition - the second Full Moon of a calendar month - has become the more popular definition. It's similar to the term "supermoon", which has caught on to describe a Full Moon or New Moon that happens close to lunar perigee (the Moon's closest point to Earth in its orbit), despite it being a fairly arbitrary astrological term.
April 21-23 - The Lyrid Meteor Shower
The "radiant" of the Lyrid meteor shower, roughly at midnight, on April 22-23. Credit: Stellarium/Scott Sutherland
Lyrid meteors originate from a stream of dusty, icy debris left behind by Comet C/1861 G1 Thatcher, and the streaks across the sky occur when Earth passes through that stream, and the atmosphere 'sweeps up' some of that dust and ice. While the stream is rather sparse, delivering only around 20 meteors per hour, at best, embedded within this stream are some larger bits, which are capable of producing fireballs!
The light from the young Crescent Moon will provide some competition for the dimmest meteors of this shower, so the best time to watch will likely be in the pre-dawn hours, after the Moon has set.
According to the International Meteor Organization's meteor shower calendar, it presents good activity on the nights before and after the April 22nd peak.
May 4-5 - The eta Aquariid Meteor Shower
Comet Halley is one of the most well-known comets in the world, for the spectacular showing it gives as it passes by our world every 75 years. It is also notable because it is the only comet we know of that produces two of the major meteor showers we see each year.
The eta Aquariids, which peak on the night of May 4-5, is the first of these two meteor showers.
The "radiant" of the eta Aquariid meteor shower, in the hours before dawn, on May 5. Credit: Stellarium/Scott Sutherland
The eta Aquariids typically produce around 50 meteors per hour, under ideal conditions*, and while they do not tend to produce fireballs, the bits of debris are moving so quickly when they hit our atmosphere that they can produce a phenomena called 'persistent trains'.
Persistent trains are colourful, faintly glowing streaks that can persist in the sky from a few seconds to several minutes after the meteor has winked out. Some have even been observed for hours afterward.
What causes this phenomenon is the exceptional speed of the meteoroids in Comet Halley's stream of debris.
When a typical meteoroid passes through the Earth's upper atmosphere, it's travelling at around 100,000 km/h, and it compresses the air molecules directly in its path to the point where they superheat and glow. This glow persists for as long as the meteoroid exists (the heat vapourizes ice particles and smaller bits of dust), and as long as it's travelling fast enough to continue compressing the air (since the compressed air pushes back against the meteoroid, slowing it down).
The particles in the eta Aquarid stream hit Earth's atmosphere travelling at more like 240,000 km/h. This produces the bright meteor flash, and sometimes there's an added bonus. After the meteor has winked out, a glowing trail can be left in the air.
Since these have only rarely been recorded, there's still some uncertainty about exactly how this is caused, however there are two basic ideas behind this effect. The first says that the meteoroids are travelling fast enough to actually strip electrons from the air molecules, leaving them in an ionized state. As the air molecules reclaim those liberated electrons, the energy they release in the process is emitted as light. Since this process can take much longer than the original meteor flash, the "train" persists in the air afterward. The second idea says that metals vapourized off the fast-moving meteoroids can chemically react with ozone and oxygen, to produce the glow via chemiluminescence. One of these explanations may account for these "trains" or both may cover different occurrences, at different times, and even between individual meteors. It will take more sightings of these to fully explain them.
The best time to see the eta Aquariids is in the hours before dawn on May 5, since the radiant only rises above the eastern horizon at that time. The Moon will be up in the sky, which will wash out some of the dimmest meteors, but look off to the south to see the Moon almost perfectly line-up with Mars and Saturn.