This week, look for the Eta Aquariids to reach their peak, slightly hidden behind the bright, Full Milk Moon. As next week begins, there will be a meeting of the Moon and planets, while Saturn begins its apparent retrograde motion.
Wednesday, May 6 – Eta Aquariid meteor shower peak
The annual Eta Aquariids meteor shower is produced by particles of material left behind by passages of Halley’s Comet. The shower, which runs from April 19 to May 26, will peak in intensity before dawn on Wednesday, May 6.
The paths of Aquariids meteors will extend away from a radiant point in Aquarius, which will lie near the southeastern horizon. The southerly radiant makes this shower better for observers at low latitudes. During the peak, watch for up to a few dozen meteors per hour, including some fireballs. A bright, nearly Full Moon in the sky on the peak morning will reduce the number of meteors seen.
Thursday, May 7 at 10:45 GMT – Full Milk Moon
The May Full Moon — known as the Full Milk Moon, Full Flower Moon or Full Corn Planting Moon — always shines in or near the stars of Libra.
Full moons are always positioned opposite to the Sun, rising in the east as the sun sets or setting in the west at sunrise. Since the sunlight striking the Full Moon is arriving straight-on to its Earth-facing hemisphere, no shadows are produced — and all of the brightness differences we see are generated by variations in albedo, differences in reflectivity of the lunar surface’s rocks. When the moon is full all of the Apollo landing sites are fully illuminated, but no earth-based telescope can see the equipment left by human explorers fifty years ago.
Monday, May 11 pre-dawn – Bright Moon and planets
In the southeastern sky during the hours before sunrise on six consecutive mornings this week, the bright, waning Moon’s orbital motion from west to east (or right to left as viewed from the Northern Hemisphere) will carry it closely past three bright planets — Jupiter, Saturn and Mars.
Although not visible with unaided eyes, it will pass Neptune, too. On Monday morning, May 11 look for the Moon positioned 1.4 outstretched fist diameters to the right (or 14 degrees to the celestial west) of bright, white Jupiter. Yellowish Saturn and reddish Mars will be arrayed to the left of Jupiter. The scene will make a fine wide-field photograph when composed with some interesting landscape scenery.
Monday, May 11 pre-dawn – Saturn stands still
On Monday, May 11, Saturn will temporarily cease its regular eastward motion in front of the distant stars of Capricornus and begin a retrograde loop (red curve with dates/times) that will last until the end of September.
The apparent reversal in Saturn’s motion is an effect of parallax produced when Earth, on a faster orbit, passes the Ringed Planet on the “inside track.” The pause in Saturn’s eastward apparent motion will allow Jupiter to approach to within 4.75 degrees of Saturn, well within the field of view of binoculars (red circle). The two gas giants will slowly separate after this week.
Chris Vaughan is a science writer, geophysicist, astronomer, planetary scientist and an “outreach RASCal.” He writes Astronomy Skylights, and you can follow him on Twitter at @astrogeoguy. He can also bring his Digital Starlab portable inflatable planetarium to your school or other daytime or evening event. Contact him through AstroGeo.ca to tour the universe together.