by Kim Malville
Mercury reaches its greatest height in the sky on the first of the month. Look in the west, some 30 to 45 minutes after sunset. It will set about 90 minutes after sunset. Mars will be visible about 15° above Mercury on this day. But, catch rapidly moving Mercury while you can, because it will rapidly sink in the west, and by April 10 it should be too faint to spot in the western twilight. Jupiter dominates the heavens, reaching its greatest height at midnight on April 7, when it will be in opposition to the sun.
April 1: Look for Mercury in the west. Don’t miss it. Remember that the greatest regret voiced by Copernicus on his death bed was that he had never seen Mercury.
April 6: The waxing gibbous moon will be close to Regulus, the brightest star in Leo.
April 10: The full moon will be close to Jupiter.
April 18: Ruddy Mars will be moving close to the Pleiades.
April 28: Look for a beautifully thin crescent moon in the west just after sunset.
TRAPPIST & its seven new planets
“This space we declare to be infinite . . . In it are an infinity of worlds of the same kind as our own.” -Giordano Bruno (1584)
In the sixteenth century the Italian philosopher Giordano Bruno, an early supporter of the Copernican theory that Earth and other planets orbit the Sun, put forward the view that the fixed stars are similar to the Sun and are accompanied by planets. He was burned at the stake for advocating the plurality of worlds and other heresies on 17 February, 1600.
The first planet beyond the solar system was detected in 1988. Now, as of March 2017, the number of detected exoplanets has reached an astonishing 3586. However, before this news only 10 of them are similar to earth and lie within Goldilocks’ zones, neither too hot nor too cold, where liquid water can exist on their surfaces. Last month three more planets were added to that list.
On February 22 we learned the extraordinary news that seven earth-sized planets surround a star named TRAPPIST 1, some 40 light years from Earth. The star is named after the telescope that first detected some of its planets: Transiting Planets and Planetesimals Small Telescope. The star is a faint dwarf, only slightly larger than Jupiter with a surface temperature half that of the sun. Because TRAPPIST-1 has a mass 84 times larger than Jupiter, its interior can generate enough dim red light to warm the surfaces of three of the planets to allow the presence of liquid water, the holy grail of our search of life elsewhere in the galaxy. These seven planets offer a smorgasbord of opportunities for life, ranging from a very hot planet (b), similar to Io, the hot moon of Jupiter, to a the most distant one (h), similar to Europa, one of the cold moons of Jupiter.
TRAPPIST-1 is an ultra-cool dwarf star in the constellation Aquarius. These planets are probably all tidally locked, meaning the same face of each is always pointed at the star. This creates a perpetual night side and perpetual day side on each planet. The habitable regions may be at the fixed boundary line between day night, a perpetual twilight zone. It also would be a region of strong winds, blowing from the hot to the cool hemispheres.
The diagram showing the detection of planets shows how the light of the star fades as each of its seven known planets passes in front of it and blocks some of its light. Looking at the figure you can tell that planets b, c, and g are the largest and d is the smallest based upon the depth of the fading. Because the innermost planets revolve faster around the star, you can easily judge the relative distances of the planets by the duration of the fading. All seven of the Earth-size planets complete a single orbit, their year, in a matter of days, ranging from 1.5 days for the nearest planet and 20 days for the farthest. The innermost four planets are locked into a fascinating coordinated dance with each other. While the innermost planet (b) circles the star eight times, the next one (c) makes 5 revolutions, (d) circles 3 times, and (e) circles once.
The life time of the TRAPPIST star is uncertain, but estimates have ranged from 3 to 8 billion years. Our sun is a little younger than 5 billion years. Thus, it is possible that life has had a chance to evolve on its planets. While our sun will run out of energy in 5 billion years, the TRAPPIST star can last whopping 12 trillion years, giving any life on its planets enough time to evolve into some pretty smart and handsome dudes.
Detecting life beyond Earth would be one of the most, if not the most, profound discovery in all human history. It would mean we aren’t unique, that the transformation of inanimate material into living material did not only occur on our planet, that we aren’t a happy curiosity, an accident that only occurred on one of hundreds of billions of galaxies in the universe. It would show that the intense urge to live, grow, and thrive, our élan vital, may be cosmic in scope. Given the right mixture of chemicals, sunlight, and environmental stability, the universe may be teeming with life. Discovery of life on other planets might even throw several of the world’s religions and their concepts of God into a chaos from which they would never recover.
Future telescopes, including NASA’s huge new James Webb Space Telescope to be launched in 2018, could help resolve such questions by closely analyzing the atmospheric gases of the TRAPPIST-1 planets. If one of these telescopes were to discover water vapor, oxygen, and methane, it would be a strong indication of life-bearing worlds. TRAPPIST has been radio quiet so far. A search for signals from its planets by SETI radio telescopes has not detected any signals. Forty years ago, they may not have been interested in talking to us.