October will be a great month to enjoy New England’s famous fall foliage. The changing leaves will slowly transform our verdant summer landscape into one of myriad and dramatic colors. The chemistry of the chlorophyll is very complex and interesting, and really makes you appreciate our precious trees and the vital function they play on Earth.
Day length and temperature both play roles in this seasonal change. One is caused by the tilt of the Earth, which causes the seasons as our two hemispheres slowly take turns facing the sun more directly. Weather and temperature changes are caused by differential heating of our life-sustaining atmosphere by the sun. So this annual and colorful ritual really reminds us of our Earth’s continual and transforming connections with our sun, which is in turn interacting with all of the stars in our galaxy.
There will be several interesting new highlights in October as the nights slowly get longer and colder while we head toward winter. There will be two meteor showers, two comets to find in the morning sky, the planet Uranus at its best for the year, and some nice conjunctions.
The Southern Taurid meteors will peak before dawn on the 10th. You can expect only about five meteors per hour, which is just above the background rate of three or four stray meteors every hour that are not associated with any shower. However, the Southern Taurids move slower than typical meteors, which make them better subjects for viewing and photography.
The more famous shower this month is the Orionid meteor shower, caused by Halley’s Comet. The Eta Aquarid shower on May 4 is also caused by this famous comet. The Orionids will be partly washed out by the moon, since their peak on the 21st is only three days after the full moon. If it is clear that night, it will still be worth it to see and appreciate these tiny, sand grain-sized pieces of Halley’s Comet streaking into our upper atmosphere at 40 miles per second.
The much heralded Comet ISON will be visible around 4 a.m. It is very close to Mars now in Leo, not just in line of sight but in actual proximity. ISON will not become as bright as originally thought, but it will probably still become a naked-eye comet by November or December at the latest. It is similar to Comet Kohoutek in that regard. Being a first-time comet, it gives off a lot of volatiles when it enters the solar system, making it difficult to predict later what that rate of brightening will be.
The other pre-dawn comet in October is Comet Encke. Discovered by German astronomer Johann Encke in 1818, this is one of the shortest period comets we have at only 3.3 years. However, based on the geometry of the sun, Earth and comet, it shows up much better every three orbits. This will be its best appearance in a decade. You can see it in Gemini, Cancer and Leo, not far away from Comet ISON and Mars. It should brighten from about 11th to seventh magnitude, similar to ISON.
The planet Uranus, discovered by William Herschel on March 13, 1781, will be at its best for the year in October as it reaches opposition on the third in the constellation of Pisces. Our seventh planet will be so bright that you will be able to see it without binoculars or a telescope. It will reach 5.7 magnitude. The human eye can see stars and objects as faint as sixth magnitude from a dark sky. Uranus will rise at sunset and not set until sunrise. This is called opposition and is always the best time to view a superior planet because it will also be closest to Earth, and largest and brightest in our skies at that time.
The good conjunctions in October will include Venus and Antares, Mars and Regulus, the moon and Saturn, and the moon with an asteroid named Juno. This is our fifth-largest asteroid at about 100 miles across and was considered a planet for a while. Spectral analysis of Juno show that it could be the source of chondrites, which are common stoney-iron meteorites that are rich in iron-bearing silicates.
Brilliant Venus will dazzle us all month. Look low in the southwestern sky one hour after sunset. Our sister planet will form a nice conjunction with Antares — the brightest star in Scorpius and one of the largest in the whole galaxy at 700 times the size of our sun — on the 16th.
Saturn has passed Venus and will set into our western horizon by the third week of this month. Look for our first planet, Mercury, close to Saturn low in the evening sky until it also sets.
Jupiter rises shortly after midnight early in October, and it will rise before 10 p.m. by the end of the month. You can easily find it in Gemini, shining at magnitude minus 2.3, which is 25 times brighter than the brightest stars in Gemini. On Oct. 12 at 1 a.m., there will be a very rare triple shadow transit. The shadows of three of its four large Galilean moons will cross over the face of Jupiter, lasting for 65 minutes. These are Io, Europa and Callisto. You will need a small telescope to witness this rare event.
Mars rises around 3 a.m. in Leo. The red planet will form a nice conjunction with Regulus on the 14th at 5 a.m. If you can look through a telescope, look for Comet ISON just one degree directly above Mars. After that, their paths get even closer, but ISON is moving a little faster.
The third annual New England Fall Astronomy Festival was recently held at the University of New Hampshire in Durham. This is turning into an excellent astronomy convention with great activities for kids and adults. They had everything from solar system walks to learn about the relationships of the planets to building and launching model rockets. There were several excellent talks and workshops on many subjects, from Comet ISON to new discoveries on the Van Allen radiation belts that shield us from dangerous cosmic rays to astrophotography.
The highlight was the featured speaker, Dava Soebel, who has written four books related to astronomy and is working on her fifth. She teaches science writing at Smith College and was inspired by Carl Sagan.
UNH has a 14-inch telescope at its observatory, which is open to the public the first and third Saturday each month. Looking at the sun with its many dramatic prominences slowly and majestically moving in real time was a good reminder of its great power and how it provides for all life on Earth.
• Oct. 3. Uranus reaches opposition tonight in Pisces.
• Oct. 4. New moon is at 8:35 p.m. On this day in 1957, Sputnik 1 was launched, beginning the space age.
• Oct. 5. On this day in 1923, Edwin Hubble found Cepheid Variables in the Andromeda Galaxy. We now use this class of star as a standard candle to determine distances to nearby galaxies.
• Oct. 6. The slender waxing crescent moon will pass near Saturn and Mercury this evening.
• Oct. 7. Neils Bohr, the father of quantum mechanics, was born in 1885.
• Oct. 9. Kepler’s supernova was observed in 1604. That was four years before the telescope was invented. It was bright enough to see for a full year. Now we know that this was a classic Type 1A supernova located about 20,000 light years away in the constellation of Ophiuchus. It is about 20 light years wide and still expanding at 4 million miles per hour.
• Oct. 11. First quarter moon is at 7:02 p.m.
• Oct. 18. Full moon occurs at 7:38 p.m. This is the Hunter’s Moon. There will also be a penumbral lunar eclipse, since we are in an eclipse season again, with a partial solar eclipse visible on Nov. 3.
• Oct. 26. Last quarter moon is at 7:40 p.m.
Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.