Commentary by Greg McCauley
Have you ever looked up in the night sky and wished upon a shooting star? We’re not sure about the power of shooting stars to make dreams come true, but we do find them fascinating.
Although planets and stars are the easiest things to see in the night sky, there are also trillions of bits of rocks floating around our solar system. Some of these space rocks are as tiny as particles of dust, others as large as boulders. What do space rocks have to do with shooting stars? Well, a shooting star has nothing to do with stars and everything to do with these little bits of rock.
A few times each year, Earth passes through a trail of rocky debris a comet has left behind while orbiting the sun. This comet trail is called a meteor stream, and when Earth passes through this meteor stream, hundreds or thousands of meteors are born. This is called a meteor shower, a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. This year on April 21 and 22, the Lyrid Meteor Shower could produce a dazzling display of 15 to 25 meteors per hour. If you trace the paths of all the Lyrid Meteors backward, they seem to radiate from the constellation Lyra, near the brilliant star Vega. This is only a chance alignment, for these meteors burn up in the atmosphere about 60 miles above the Earth’s surface. Meanwhile, Vega lies trillions of times farther away at 25 light-years. Yet it’s from Vega’s constellation Lyra that the Lyrid Meteor Shower takes its name. You don’t need to identify Vega or Lyra in order to watch the Lyrid Meteor Shower. The meteors radiate from there, but will appear unexpectedly, in any and all parts of the night sky.
Comet Thatcher (C/1861 G1) is the source of the Lyrid meteors. Every year, in late April, our planet Earth crosses the orbital path of this comet. It last visited the inner solar system in 1861, and isn’t expected to return until the year 2276.
Bits and pieces of rock shed by this comet litter its orbit and bombard the Earth’s upper atmosphere at 110,000 miles per hour each April and the vaporizing debris blaze through the nighttime sky as the Lyrid meteors.
While the Lyrids are a medium-scale shower in terms of the number of meteors, they’re known for producing quite a few fireballs, which are shooting stars that flash brightly and leave a long-lasting streak across the sky.
So take a break from your hectic schedule and enjoy the celestial fireworks. Look to the northeast sky late in the evening on April 21 and 22 as we fly through the tail of a comet.
Greg McCauley is President and CEO of Grand Universe, an amateur astronomer and former NASA employee during the Apollo missions to the Moon. Greg and his wife Janet live in Westfield.