Celestial Lights
By Phyllis Burton Pitluga (April 28, 2006)
May's Celestial Lights
A comet is breaking apart overhead May 12, 13 and 14
An unusual sight in binoculars and telescopes will be the breaking up of a comet. This comet has been orbiting through the solar system approximately every five and a half years since its discovery in 1930. The comet was named for its discoverers, two German astronomers named Schwassmann and Wachmann. The comet's name is preceded by the designation of P73.
Comets are irregular spheres of ices and particles and are a few miles across. The heat from the sun vaporizes the ice, which then forms a cloud around the comet, giving it a foggy appearance. The wind of protons streaming outward from the sun blows the comet cloud into an elongated comet tail that always points away from the sun (the tail is not caused by the motion of the comet itself).
When Comet P73/Schwassmann-Wachmann passed through our neighborhood of the solar system in 1995, it had already begun to break apart. On this, perhaps its last, passage, the comet pieces will be six million miles away. In future months of May, we might witness a meteor shower from the grains still in orbit.
To view these comet pieces, look directly overhead about 6am with your binoculars. The three brightest stars (from three different constellations) form "The Summer Triangle." The comet pieces will be just to the east of these stars. They will be dim, fuzzy blurs of light-not impressive until you realize what you are looking at.
The sun is directly overhead May 25-26 at 1:40pm
Because San Miguel de Allende is in the Tropical Zone, the sun passes overhead twice during the year: May 25-26 and again on July 18-19. Earlier in May, the sun is south of overhead. After May 26, the sun is north of overhead. The sun continues to be ever farther north of overhead until the June solstice on June 21. Then, the sun gradually returns to passing overhead on July 18-19. For the following 10 months, the midday sun will be to the south.
To see the phenomenon of the sun directly overhead on May 25-26, go outside at Local Noon. Here in San Miguel, Local Noon is at 1:35pm (because daylight-saving time = 1pm, and we are west in our Central Time Zone by 40 minutes = 1:40pm and the Earth is orbiting a bit slower in May, so we return to noon five minutes earlier than average = 1:35 for Local Noon now). Notice the shadows of trees, upright posts and your own shadow.
Revisiting our Milky Way Galaxy
This color photograph of the Whirlpool Galaxy is like a mirror reflection of our own Milky Way Galaxy. NASA Hubble Space Telescope image.
My last article (April 7 Atención) should have displayed the galaxy image in color and with the label "Whirlpool Galaxy" to make sense what had been written, and is reprinted.
Since we live inside our island galaxy of stars, we can never get a photograph of how it looks. But, by analyzing star distances and distributions, we have a fairly good idea of how our Milky Way Galaxy must look: a flattened pinwheel of stars, similar to the Whirlpool Galaxy, 36 million light years away and overhead in our spring evening sky.
Look at the Hubble Space Telescope image of the Whirlpool Galaxy and imagine it as a mirror reflection of our own Milky Way Galaxy. Our solar system is imbedded in this disc about two-thirds from the center.
In the center of our galaxy the stars are older yellow stars. But out in the spiral arms where we live, the stars are young. The dark lanes are where new stars are brewing; hot new stars are lighting the bright pink hydrogen clouds, and the blue stars have blown away their cocoons of gas and dust with the strong stellar winds that they produce.
Tuesday, May 2: Moon passes above Mars
Thursday, May 4: Moon passes above Saturn and Jupiter is at opposition (it rises as the sun sets)
Friday, May 5: First quarter moon
Wednesday, May 10: Moon passes just above the star Spica, a hot star that is 262 light years away and is a multiple star system
Friday, May 12: Moon passes under Jupiter
Saturday, May 13: Full moon
Sunday, May 14: Moon passes just below Antares, a Red Giant star that is 604 light years away and that irregularly varies in brightness and is a double star
Saturday, May 20: Last quarter moon
Sunday, May 21: Moon passes under Uranus (binoculars or telescope needed)
Wednesday, May 24: Moon passes above Venus
Saturday, May 27: New moon
Tuesday, May 30: Moon passes above Mars and Saturn
Phyllis Burton Pitluga is Astronomer Emerita of the Adler Planetarium and Astronomy Museum, Chicago, and is now a San Miguel resident.