LOOK UP during these August nights, and you’ll be treated to the sight of many bright stars. All of these belong to our Milky Way, a galaxy containing several hundred billion stars, one of which is our sun. Most of the stars visible with our unaided eyes are relatively close by astronomical standards, but their actual distances are truly beyond human comprehension.
Because the mile is not an adequate unit of measure in astronomy, astronomers employ the unit of distance known as the light year to measure distances in space. One light year is equal to approximately six trillion miles, the distance that light travels in one year moving at 186,000 miles per second.
Almost overhead in the night sky this month is the star named Vega. It is estimated to be about 25 light years away from Earth, meaning the light you see tonight left Vega 25 years ago in 1995. As you face south, look to the left of Vega for a slightly dimmer star named Deneb, one of the farthest stars visible without optical aid at a whopping 2,600 light years away. Yes, that light you see from Deneb is around 2,600 years old!
Moving much closer to Earth in distance, very bright Jupiter is visible in the southern sky well below Vega and Deneb. Unlike the stars, we can almost comprehend the distance to Jupiter in miles, or we can once again use light as the measuring stick. By using light, we find that Jupiter is around 35 light minutes, not years, from Earth. This means the light you see from Jupiter tonight is around 35 minutes old. For comparison, the sun is around 8½ light minutes away while our closest natural satellite, the moon, is only 1.3 light seconds away. Clearly, the road to the stars is a very long one outside of our solar system.
The first few days of the month feature the moon near bright Jupiter and dimmer Saturn in the eastern sky after sunset. The moon will be closest to Jupiter on the 1st and nearest to Saturn on the 2nd. If you miss those dates, the moon also swings by the two planets at the end of the month on the 27th–29th.
Mars will be near the moon during the late evening of the 8th and into the early morning of the 9th.
Venus continues to be a brilliant morning object this month and will be located close to the moon during the morning of the 15th.