Looking Up column: Catching a moving point of light
You may have heard the news from NASA this past week (on Oct. 20) when we touched the face of an asteroid.
NASA’s OSIRIS-REx spacecraft, after a year and a half journey, completed its amazing task of touching down on the rocky pile of rubble named Bennu, to collect samples and bring them home.
Once the spacecraft returns in 2023, landing by parachute in a Utah desert, scientists eagerly await study of the fragments and dust. An exponential increase in knowledge about asteroids and the solar system’s creation is anticipated, and likely more mysteries to solve.
All this action last week took place 200 million miles from home, at an asteroid 861 feet wide, a little more than the Empire State Building is high.
There was a time, not many years ago, all asteroids were but specks of light in the night sky, as far as we could discern. The first asteroid to be discovered was Ceres, in 1801 by Giuseppe Piazzi, an Italian astronomer. He was searching to see if there was any unknown planet within the large gap between the orbits of Mars and Jupiter.
Ceres turned out to be the largest asteroid known. In fact, Ceres has been reclassified as a dwarf planet. Ceres is 291 miles wide and spherical, orbiting between Jupiter and Mars once around every 4.6 years. NASA’s Dawn spacecraft went into Ceres orbit in 2015.
There are more than 600,000 known asteroids in the solar system. All get a number in order of their discovery and many have been named. 1 Ceres was the first; within three years, 2 Pallas, 3 Juno and 4 Vesta were found. The fifth, Astraea, was not discovered until 1845. One hundred asteroids were known by 1868, and 1,000 by 1921.
Bennu is number 101,955.
Some of them pose a threat to the Earth, but the vast majority keep their social distance.
Numerous asteroids are large enough to be seen with a small telescope, and some with binoculars. One, asteroid Vesta, can become just bright enough to be seen by naked eyes like a dim star; a very clear, dark night is required.
At least two of the brighter asteroids are visible with binoculars in the evening sky this fall, 1 Ceres and 8 Flora.
Asteroids look like faint stars in binoculars and telescopes. In fact, they are indistinguishable at first glance from the multitude of dim stars you will see spread across the sky. What is exciting is identifying what should be the asteroid and then looking again the next night to find that it has moved!
Popular astronomy magazines are a source to find detailed star charts when a brighter asteroid is in view; they show the track in front of the starry background night by night. With some experience with star charts, you can enjoy hunting the asteroids down.
Occasionally an asteroid comes fairly close to Earth, perhaps just beyond the moon’s distance or even closer. Amateur astronomers delight in spotting these thankfully rare interlopers, and seeing how quickly they move. One time I tracked one down, and with high magnification, I could actually see the point of light slowly moving in real-time, past the background stars.
Scanning the heavens with your backyard telescope, you will spot many points of light moving swiftly through the eyepiece. These are not asteroids; they are manmade, earth satellites.
Amateur astronomers are also alerted from time to time about an asteroid much too faint to be seen in a small telescope, that is about to occult (eclipse) a background star. As the asteroid passes in front, the star blinks off! By making many careful measurements of the time this takes, as seen from various places across the country, astronomers can construct an outline of the often-irregular shape of the asteroid. Some have even been found to have moons - smaller asteroids accompanying them, which cause a secondary, unexpected blink of the background star.
Other asteroids are “binary” - two that are stuck together.
Radar has also been used to determine the shapes of asteroids.
As has been well-publicized and dramatized, much research is being done about near-earth asteroids that could potentially smack into the Earth someday. If one thinks it cannot happen, just look at the moon and its many craters, caused at a time of fierce bombardment eons ago. Earth has a few visible craters as well, although most have eroded away by weather and geologic upheavals.
But fear not; we have enough of our share of daily concerns in this world, thankfully balanced by an abundance of good things and a reservoir of hope to keep us going. Among the little joys we can have is just looking up at the canopy of stars any clear night, and even picking out a distant asteroid.
On the next clear evening, enjoy bright red Mars in the east, and Jupiter and Saturn in the south-southwest (Jupiter is brighter). The lovely moon is waxing to full phase on Oct. 31.
Keep looking up at the sky!
Peter Becker is managing editor at The News Eagle in Hawley, Pennsylvania. Notes are welcome at firstname.lastname@example.org. Please mention in what newspaper or website you read this column.