May 1 – 7
The moon is new on the 6th, but on the mornings of the 2nd and 3rd, it’s visible in the low east before sunrise. If you leave for work before sunrise, be sure to take a look at the moon and Earthshine on its right side. You’ll need to make this observation by around 4:45 AM. Much later and the light of dawn will wash out Earthshine.
The Eta Aquarid meteor shower peaks on the night of the 6th and morning of the 7th, which is awesome since this is a Friday night and Saturday morning. We can observe up to 30 meteors per hour from this shower; unfortunately, this is the case if you live the southern hemisphere. However, it’s still worth observing this shower as the nights are getting warmer and the moon is new. That means we’ll have warm, dark skies for observing this shower. There’s no need to watch this shower all night, as the radiant for the shower doesn’t rise until after 3:00 AM. So look for meteors appearing from the low east after 3:00 AM.
May 8 – 14
The moon reappears in the low west-northwest on the 8th. So after it gets dark after 10:00 PM, look for the moon and see if you can detect Earthshine illuminating its dark portion. Earthshine will be most visible if you view the moon through binoculars. The brightish orange star to the left of the moon is Betelgeuse, a star in the shoulder of Orion. You can make observations of Earthshine for several more nights.
Mercury made an evening appearance last month, but disappeared before the end of April. This month Mercury passes between Earth and the sun and in Idaho, we get to see a part of that. This is called a transit and it only happens on an average of 13 times per century. The transit begins on the 9th at around 7:00 AM in Idaho and ends shortly after noon.
A transit is not safe to observe directly with your eyes, since it requires looking at the sun. This means that a telescope properly covered with solar viewing filters can observe the transit of Mercury, but other instruments cannot. The rest of us will need to rely having an acquaintance who is an amateur astronomer, finding a local astronomy club giving public viewings, or using the projection method of observing the sun. How can you project an image of the sun? A pair of binoculars, spotting scope, or small telescope pointed at the sun will project an image of the sun out its eyepiece. Do NOT look at this image through the eyepiece. Instead, position the telescope so that the image projecting out of the eyepiece falls upon a sheet of paper. Then focus the binoculars, spotting scope, or telescope so that the image is sharp. Any sunspots visible during the transit will appear to have fuzzy edges while Mercury will be a tiny round dot with well-defined edges. Mercury will transit south of the sun’s equator, from Earth’s perspective. Remember that if you observe the transit with a telescope, the image will be upside down.
Gemini appears like the waist and legs of a soccer player. Look in the low west after dark in May and you’ll see upright Gemini as two columns of stars. At the top of the columns are two bright stars, Pollux (on the left) and Castor (on the right). Castor and Pollux mark the head of the Gemini Twins, but more like the waist of a soccer player. Even better, on the evening of the 9th, the crescent moon appears at the feet of Gemini just like Gemini is about to kick it like a soccer ball.
One of the closest stars to the sun appears to the lower left of the moon on the 10th. The star’s name is Procyon, which means “Before the Dog”. The dog in this case is the Dog Star, Sirius. Procyon gets this name because it rises shortly before the rising of Sirius. Procyon is the eighth brightest star in the sky because it’s only 11.5 light years away and not because its particular bright compared to other stars. Procyon is a young star, only one quarter the age of the sun. Procyon is the brighter of the two stars forming the constellation of Canis Minor, or the Little Dog.
Hey, want to see a really nice star cluster? You can on almost any night, but the 11th is better because the moon will help you find it. The star cluster is named the Beehive Star Cluster and you’ll find it 7 degrees above the moon on the night of the 11th. To see this attractive star cluster, point you binoculars at the moon and then tilt them directly north of the moon. Just after the moon leaves the binoculars’ view, the Beehive will appear at the top of the field of view. You should see a striking similarity between the Beehive and a swarm of bees.
The moon reaches the first quarter phase on the 13th. The star Regulus also appears above the moon that night. Regulus is the brightest star of Leo the Lion. The constellation is standing on end above the moon that night. Regulus is so close to the moon that both can be seen together at the same time through binoculars.
There’s an even brighter star above the moon on the night of the 14th. In his case, the star is Jupiter, the King of the solar system’s planets. Both the moon and Jupiter can be seen together in your binoculars on the 14th. You should notice that Jupiter appears as a more intense source of light than the moon and that it is accompanied by a retinue of satellites. On the 14th, binoculars will let you see up to three of Jupiter’s moons. From left to right, the moons will be Callisto, Europa, Jupiter, and Ganymede. The planet’s innermost moon Io very close to Jupiter and might not be visible through binoculars. If you have a spotting scope or larger, then Io appears near the right edge of Jupiter.
May 15 – 21
The moon passes very close to Spica on the night of the 17th. Spica is the brightest star of Virgo the Maiden, the second largest constellation. Virgo is made up of dim stars, so the constellation doesn’t stand out to the extent its large size should make it. One depiction of Virgo is as a goddess of justice named Justitia. In this guise, she holds the scales of justice in her hands, or the constellation of Libra.
A widely spaced double star located in Libra can be found below the moon on the 19th. The star’s name is Zubenelgenubi and the angular distance between the companion stars is wide enough that some people can see it as two separate stars without optical aid. The rest of us need a pair of binoculars. The star is 5 degrees below the moon, therefore, place the moon at the top of your binocular’s view and Zubenelgenubi will be the bright pair of stars at the bottom.
The moon is full on the 21st. Full moons in May are sometimes called the Flower Moon and you’ll find the Flower moon located between the planets Mars and Saturn. Mars will be the bright orange-tinted star to the right of the moon and Saturn will be the fainter yellow-white star to the lower left of the moon. Below the moon is another orange star, Antares. Antares is the heart of Scorpius the Scorpion.
May 22 – 30
Mars reaches opposition on the 22nd. At opposition, superior planets, or those beyond Earth, are at their closest to Earth for the year. Opposition occurs when the faster orbital motion of Earth results in Earth catching up to and passing the superior planet in question. In the process of reaching opposition, superior planets appear to retrograde, or move slightly backwards across the stars. Retrograde motion is an illusion caused by the changing perspective between Earth and superior planets when compared to the fixed stars. Hundreds of years ago, when the geocentric or Earth-centered solar system was in vogue, astronomers and philosophers believed the superior planets actually moved backwards during a short period of time. This was possible because these planets orbited Earth in a set of nested orbits of various sizes. Copernicus convinced astronomers in the 16th century that the retrograde motion of the planets was easier to explain by moving the sun to the center of the solar system and demoting Earth to a planet orbiting the sun.
The bright yellowish star visible to the right of the moon on the 22nd is Saturn. You’ll need at least a spotting scope capable of magnifying at least 25 times in order to see the planet’s rings and largest satellite, Titan. Titan is a fascinating world. It’s larger than Earth’s moon and surrounded by an atmosphere denser than Earth’s. Unfortunately, it’s intensely cold on Titan. So cold that methane, a gas used to heat our homes, is a liquid. Its nitrogen-rich atmosphere is almost cold enough to liquefy. Because of its dense atmosphere and liquid methane, Titan has weather, but probably not as dynamic as Earth’s. This still allows it to rain on Titan, but with methane rain.
If you’re a late night person, you can use the moon to locate several star clusters and nebulae on the morning of the 24th. These attractive deep sky objects are located between Earth and the center of our galaxy, meaning they appear in the thick of the Milky Way (which is why you need to wait until after midnight to see them). These clusters and nebulae are small, so you need a pair of binoculars to see them. Through binoculars, the nebulae will appear as fuzzy spots while the star clusters will have some stars sprinkled among the fuzz.
The moon is last quarter on the 29th, which is nice, but it has a neighbor that night that will give you a real astronomy challenge. The eighth planet, Neptune is just 4.5 degrees away from the moon on the 29th. This means you can see both together in a pair of binoculars, which typically have a field of view of 5 degrees. You need dark skies in order to see Neptune, so leave town for the countryside. To see Neptune, place the moon on the right edge of your binoculars and find the brightest star directly east of the moon. This star will be near the left edge of your binoculars. A small distance farther east of the bright star is a faint star that’s as bright as Neptune. The distance between the star and the brighter star is the same distance Neptune is away from the bright star. Neptune is the other faint star down and slightly left of the bright star. The bright star, faint star, and Neptune will form a small triangle with a 90 degree apex.
The moon is close to the eastern horizon as you drive to work on the 31st. Can you see Earthshine? Binoculars will definitely help (but don’t use binoculars while you drive!).
This Month’s Sources
Astronomical Phenomena of the Year 2016, The Nautical Almanac Office and Her Majesty’s Nautical Almanac Office
Astronomy Calendar of Celestial Events for Calendar Year 2016, http://www.seasky.org/astronomy/astronomy-calender-2016.html
Climate of Titan, https://en.wikipedia.org/wiki/Climate_of_Titan
Mercury Transits the Sun, http://skyandtelescope.com/observing/ceelstial-objects-to-watch/mercury-transits-thesun/
Night Sky Explorer