by Kim Malville
This is a glorious month for planets; all eight planets will appear in our skies. Jupiter is in the west at dusk, lying between the constellations of Leo and Virgo. Mars, as red and spectacular as ever, is in Scorpius. To its left left is Saturn, which is whiter and fainter. Below Saturn is the red giant, Antares, completing the triangle with Mars. Later in the month, Mercury and Venus will appear in the western skies just after sunset.
July 4: On this day
Earth is farthest from the sun, reaching a distance of 94,512,904 miles. We are hotter in the northern hemisphere because the earth is tilted toward the sun in our summer, even though we are slightly further from the sun: a very nice little paradox.
July 7: Look for the new crescent moon above the western horizon. Just to its right you will find Regulus, the brightest star in Leo.
July 8: The moon has moved eastward and now lies just below Jupiter.
July 15: The moon forms a nearly vertical line with Saturn and Antares.
July 30: Just as it is getting dark in the evening, look to the west-northwest where you might find Mercury and Venus appearing next to fainter Regulus.
Global warming is slowing the Earth
Last month, summer solstice arrived a little late, and the day was a little long because the earth is slowing its spin. Most of the slowing has been due to the drag of the moon on our oceans. But now, because of the melting of ice sheets and glaciers near the poles, water is accumulating near the equator. That extra mass slows the earth, like an ice skater is slowed by holding her arms out. It’s due to the conservation of angular momentum, when the equator gets loaded with extra weight, the speed of rotation needs to slow. The combination of the moon’s influence and water loading of the equator slows the spinning of the earth by 1.7 milliseconds per century, a small and unanticipated consequence of global warming. Lots of other consequences lie ahead.
Gravity waves shake the Earth again
Gravitational waves have again been detected by LIGO, the Laser Interferometer Gravitational-Wave Observatory. LIGO consists of two sets of detectors, separated by 3000 kilometers, at Hanford, WA and Livingston, LA. Each detector consists of two arms that are 4 km in length, which are perpendicular to each other. The time for a laser beam to go back and forth in one arm is compared to that in the other. If a gravity wave has passed through the earth and changed the structure of space, the transit times of the laser light in each arm will be different. Only if these differences occur nearly simultaneously at Hanford and Livingston, will the change be considered a solid detection of a gravity wave.
You may remember that the first detection occurred on September 14, last year. The second burst of gravitational waves arrived on Christmas Day. This time the black holes were smaller, a mere 8 and 14 times more massive than the sun. (The first merger of black holes involved masses, 29 and 36 times larger than the sun.) Both of these violent encounters took place in galaxies far beyond our own, some 1.3 to 1.4 billion light years away. We know only approximately where in the sky they occurred, but we do know they came from different regions of the universe. This second detection of gravity waves is important. Redundancy is very nice in science.
Alien life probably flourishes around red dwarfs
Once we thought the best places to search for alien life were rocky and watery planets like the earth, circling a star like our sun. Now, a new type of star has become interesting, namely red dwarfs, which are smaller than the sun, but are the silent majority of our galaxy, making up 70% of the stars of the Milky Way. These dwarfs are red because they are cool. In order for a planet to have liquid water it needs to be close to such a star, in such a case it is probably tidally locked to the star, keeping one side always facing the star. (Our moon is tidally locked to the earth). One side would be in perpetual daylight and the other sunk in eternal night, creating enormous temperature variations from one side of the planet to the other. The zone of perpetual dark would be cold enough to freeze the main gases of their atmospheres, leaving the daylight zone nude and dry. Tremendous winds might be blowing across the regions of perpetual twilight. However very recent studies suggest that a thick atmosphere or planetary ocean could circulate heat around such a planet and moderate the temperature difference.
The most significant feature of these red dwarfs is that they practically last forever. When most stars reach old age and begin to run out fuel, they swell up to hundreds of times their normal size, engulfing planets that orbit too close. In about 5 billion years, our sun will start expanding, eventually swelling to about 200 times its current size. It will swallow Mercury and Venus. Skimming the surface of this bloated star, the Earth will be uninhabitable, a sizzling wasteland.
The great advantage for alien life on their planets is that red dwarfs can live for trillions of years, because their nuclear reactions are far slower than those of larger stars. It took 4.5 billion years before humanity appeared on Earth. What if life on planet Earth had been around for hundreds of billions of years already? Just think how smart we would be! This is truly the subject matter for science fiction. In fact, it already has been written.
In Olaf Stapledon’s 1937 wonderful novel, Star Maker, one of the many alien civilizations in the Milky Way he describes is located in the twilight zone of a tidally locked planet of a red dwarf star. This planet is inhabited by intelligent plants that look like carrots with arms, legs, and a head. They sleep part of the time by inserting themselves into soil and absorbing sunlight through photosynthesis. When awake they emerge from their plots of soil as locomoting beings who participate in all the complex activities of a modern industrial civilization. Would you believe it? The future belongs to carrots!