Regardless of whether Punxsutawney Phil sees his shadow on Groundhog Day this Wednesday, there will still be six more weeks of winter for us in the northern hemisphere.
Late January and early February mark the coldest days of the winter. In summer, we usually get the hottest days in early August for the same reason. That is because it takes some time for the earth and the water to continue cooling off after the shortest day of the year. It also takes the earth and the water about six weeks to heat up to their maximum temperatures after the summer solstice in June.
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The ocean temperature off Portland averages 39 degrees when winter starts and averages only 33 degrees in February. It averages 57 degrees when summer starts and reaches its highest average of 62 degrees in August.
There are several interesting celestial highlights in February if you are willing to brave the cold to enjoy the crystalline clarity of the midwinter sky. There are only three planets visible, but all three have unusual activities going on, as if they are competing for our attention.
The South Equatorial belt on Jupiter, along which the Great Red Spot travels, is continuing to return after a brief disappearance last year.
Saturn has sprung a massive new storm, which could be one of the rare Great White Spot outbreaks that occur periodically on this giant gas planet. At 36,000 miles long by the end of last year, this spot was already bigger than the circumference of the earth. The white spots usually occur about every 29 years, which corresponds to Saturn’s orbital period around the sun. However, there are some exceptions, and this is one of them since the next white spot was not expected until 2018.
The storm appears white because it is made of ammonia ice crystals. They start by shooting warm gas up from Saturn’s lower atmosphere and through a thick upper mantle of smog-stained ammonia ice. As the gas expands in the upper atmosphere, fresh crystals of ammonia condense on the cooling vapor, forming the white region visible from Earth.
Not to be outdone by the two largest planets in our solar system, Venus, sometimes called our sister planet because it is the same size as the earth, 8,000 miles in diameter, has two other interesting solar system bodies following it very closely through the sky in February. Brilliant Venus will be passing through the constellation of Sagittarius very close to nearly a dozen bright Messier objects visible in binoculars, including the beautiful Lagoon and Trifid nebulae.
Unlike Jupiter and Saturn, there will be no major, visible changes taking place on the surface of Venus, which is always cloud-covered and uniformly hot at nearly 900 degrees F because of trapped carbon dioxide, but two objects will appear to be following it.
Our second largest asteroid, named Vesta, which is 325 miles in diameter, will be less than half a degree above Venus on Feb. 9. You will need good binoculars or a telescope to see Vesta, since it is 12 magnitudes, or over half a million times fainter than Venus.
The other famous object that will be only 2.3 degrees north of Venus that same morning is the dwarf planet Pluto. At 13.8 magnitude, Pluto is another 250 times fainter than Vesta, which makes it 150 million times fainter than Venus. Usually Pluto is further out of the ecliptic plane than the full-fledged planets, but it is now approaching the plane and will cross it in 2018. That means Pluto will have many closer encounters than usual with brighter planets over the next decade.
Vesta is very different from the largest asteroid, Ceres, which is 600 miles across, or about twice the size of Vesta. Ceres is icy and very primitive in its evolution. It may have seasonal polar caps of water frost and a thin, permanent atmosphere. Vesta is more evolved and dry, with a surface of silicate rock, showing that it has a similar geologic history to terrestrial planets.
Vesta has suffered thousands of major impacts throughout its 4.6 billion-year history. One of them left a crater nearly the size of the asteroid itself, thereby exposing material from deep inside Vesta’s mantle, which would help us better understand Earth’s mantle. Vesta was hit so many times that about 6 percent of all the meteorites that hit the earth, based on similar spectral properties, are actually pieces of Vesta. This asteroid may also have very strongly magnetized rocks.
We should solve those mysteries and learn much more about the story of these contrasting asteroids very soon, when the Dawn spacecraft arrives at Vesta this July. It will spend one year orbiting and learning about Vesta and then head on to Ceres, where it will arrive in four years, February of 2015. Dawn was launched on Sept. 27, 2007 and uses an effective new ion propulsion drive to enable it to spiral to lower orbits around Vesta and Ceres and save on fuel.
The Dawn spacecraft has the lofty goals of 1) capturing the earliest moments in the formation of our solar system, enabling us to understand the original conditions leading to their formation; 2) determining the nature of the basic building blocks from which terrestrial planets formed; 3) contrasting the evolution of two small planets on very different paths so we can better understand what controls their evolution and exactly why they turned out so different.
The role of water in the evolution of planets and how the growth of these two baby planets was interrupted by the formation of Jupiter will also be studied.
FEBRUARY HIGHLIGHTS
Feb. 1: A very thin waning crescent moon will be just above Mercury and about 20 degrees below and to the left of Venus this morning 15 minutes before sunrise. You will need binoculars to see Mercury and the thin crescent moon.
Feb. 2: New moon is at 9:31 p.m. EST.
Feb. 4: Clyde Tombaugh was born on this day in 1906. He would discover Pluto when he was just 24 years old, on Feb. 18, 1930.
Feb. 6: Jupiter is about 6 degrees to the left of the thin waxing crescent moon this evening.
Feb. 11: First quarter moon is at 2:18 a.m. On this day in 1970, Japan became only the fourth country to make and launch its own satellite. The former Soviet Union was first, with Sputnik in October 1957; the U.S. was second, with Explorer in January 1958; and France was third in November 1965. Unlike Sputnik, our Explorer satellite actually did some very useful scientific work, discovering the Van Allen radiation belts, which protect us from the powerful and deadly solar wind.
Feb. 15: Galileo was born on this day in 1564. He revolutionized our concepts of astronomy by proving that the sun was the center of the solar system and by seeing and discovering many other unexpected things through his improving telescopes. These included the rings of Saturn, sunspots on the sun, the phases of Venus and Mercury and four moons of Jupiter.
Feb. 18: Full moon is at 3:36 a.m. This is also called the Snow, Hunger or Wolf Moon.
Feb. 21: Saturn will be just above the waning gibbous moon this morning 40 minutes before sunrise. Along with Spica to the left, they will form an almost equilateral triangle.
Feb. 24: Last quarter moon is at 6:26 p.m.
Feb. 28: The waning crescent moon will be just above Venus one hour before sunrise.
Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.
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