The Eta Aquarid meteor shower peaks near the early morning hours of May 4 or 6. This is an excellent shower for those in the southern hemisphere but weak for us in Minnesota. In dark skies around 4 or 5 am, expect to see perhaps 10 meteors per hour. These meteors, best seen away from city lights with the naked eye, result when Earth plows into small bits left over from Comet Halley.
For those inclined to view the sky in the evening around 10:30 pm, try some star hopping. For example, look almost overhead for the Big Dipper. Follow the curved handle of the Dipper away from the scoop as you arc to Arcturus, a bright reddish star high in the SSE in the constellation Boötes. Then continue along that line to spike on to Spica (aka speed to Spica or straight on to Spica). Spica far outshines all the other stars in Virgo.
And if you have been following the recent black hole news, you can see the galaxy that hosts the shadow of a massive black hole at its center, M87. The galaxy lies about 26 degrees west of Arcturus and you will need a telescope to see it. Come to a star party event or a presentation in the Whitney and Elizabeth MacMillan Planetarium to learn more!
Earth’s only natural satellite is simply called “the Moon” because people didn’t know other moons existed until Galileo Galilei discovered four moons orbiting Jupiter in 1610. The Earth and Moon are tidally-locked. Their rotations are so in sync we only see one side of the Moon all the time. (Humans didn’t see the lunar far side until a Soviet spaecraft flew past in 1959.)
Have you ever wondered what causes the phases of the Moon? The diagram below shows the Moon’s phases as we see them in the Northern Hemisphere, and at each position of its orbit. Lunar phases are created by changing angles, or relative positions, of Earth, Moon and Sun, as the Moon orbits the Earth.
As the Moon waxes and wanes, sunlight illuminates different features on its surface. Up until the full Moon, crater rims cast mile long shadows that produce a stark contrast against the lunar surface. The first and last quarter Moon are the best for seeing details, especially along the terminator (the line between the lit and unlit side). If you look long enough in the dark area near the terminator you can even find bright points of light—lunar mountain ranges catching the first light of the Sun as the Moon orbits around the Earth.
A full Moon is stunning to see in the sky, but its brilliant light washes out many surface details from view. However, a full Moon can be a great time to study the largest structures on the Moon, like craters and maria.
May 4 – New Moon
May 11 – First Quarter Moon
May 18 – Full Moon
May 26 – Last Quarter Moon
Deep sky objects
Cat’s Eye Nebula
Observing method: Telescope
This beautiful planetary nebula is well placed to find with a telescope this summer. Look in the crook of the neck of Draco, the Dragon, to spot a tiny blue jewel. The remnants of this dead star glow from the energy left from a white dwarf at the center of an expanding, cooling cloud of gas left over from the original star’s outer atmosphere. Although most of this object is made of hydrogen and helium, there are other elements as well. The blue color comes from doubly ionized oxygen, or OIII (‘oh-three’). Even more detailed observations from telescopes like the Hubble Space Telescope have revealed multiple layers in this stellar remnant: ring-like structures whose exact formation is still unclear.
Observing method: Naked eye, binoculars, telescope
Constellation: Ursa Major
Mizar and Alcor are located in the crook of the Big Dipper’s handle. Mizar is the second star from the end, and Alcor its fainter companion. Persian astronomer Al-Sufi noted this binary star system as “the one with which people test their vision.” A binary star system is one where two stars revolve around each other or both revolve around a common center—these two orbit each other every 750,000 years.
Today, especially when under light polluted skies, binoculars help resolve the binary star. In fact, astronomers confirmed in 2009 that Mizar is four stars and Alcor is two stars (gravitationally bound to Mizar’s quadruple system).
Mizar and Alcor not only test human eyesight, but the limits of our technological vision. Note: Viewing Mizar/Alcor is not an adequate replacement for a visit to the optometrist!