Sunday, January 24, 2010
Mars escapes a swarm of stellar bees
John Goss
John Goss is chairman of the Mid-East Region of the Astronomical League and a former president of the Roanoke Valley Astronomical Society.
Recent columns
- When were the stars born?
- Moon, Venus, Jupiter in a predictable dance
- Look far beyond the stars of the Milky Way
- The planets lead nomadic existences
Blog
Even though it is the most storied of distant planets, it certainly isn't the most eye-catching. Even though it is the most explored of other planets, it isn't well understood. Even though it is the most Earth-like of planets, it isn't remotely hospitable to human life. Even though it is currently the most easily visible of the bright planets, it isn't likely to command the attention of most people.
This intriguing, mysterious, harsh, yet visually accessible planet is Mars, the fourth planet from the sun.
Our blue Earth catches and passes red Mars this week. On Wednesday, their separation drops to this encounter's minimum of 62 million miles -- still more than 250 times farther than the moon. This means that this week, Mars reaches its brightest appearance, rivaling that of the dazzling white star Sirius, now shining low in the south-southeast in the early evening.
During past apparitions, Mars exhibited a luminosity as much as three times greater than it does this week. This brightness difference is due to its elliptical orbit which, on occasion, brings it another 30 million miles closer to us.
By the end of February, the interplanetary gap increases by 10 million miles and, accordingly, the brightness of Mars drops by half. As the Earth advances its orbital lead, Mars continues its decline in brightness through the summer.
Like all planets, Mars appears to move against the starry backdrop. During the first half of February, the bright planet passes near the faint star cluster M44, popularly called the "Beehive." Look toward the east before the moon rises for Mars creeping through the dim constellation Cancer, which lies between the bright stars Pollux in Gemini and Regulus in Leo. Two other brighter stars, Procyon and Sirius, shine to its right.
Through binoculars, you will easily spot the glow of the many stellar bees buzzing in the Beehive. You will also see four brighter stars of near-equal brightness -- the "Skep" -- that contain the hive. As the nights pass, stealthy Mars sneaks above the Skep, slipping past the "Swarm," a starry stream of menacing bees.
While this celestial commotion takes place, another, more peaceful event occurs in neighboring Leo. The next rocky body of any appreciable size that lies beyond Mars and in its same general direction can be found the week before and after Valentine's Day.
Leo, marked by Regulus, hovers above the eastern horizon and below Mars about 8 p.m. The constellation's second-brightest luminary, Algieba, shines to the left of Regulus.
Look at Algieba through binoculars. A dimmer star, 40 Leonis, lies just to its lower right. The third-brightest object in the field is not a star, nor a planet, but the third-largest asteroid, Vesta.
Just how large -- or rather, how small -- is this potato-shaped worldlet? Vesta's long dimension is the same length as Virginia's portion of Interstate 81. This, combined with its distance (always more than 130 million miles), causes Vesta to appear starlike except in the largest of today's telescopes.
As the evenings pass, plot on paper the relative positions of Algieba, 40 Leonis and Vesta. You will quickly notice the asteroid heading directly toward the two stars. On the nights of the 15th and 16th, Vesta moves between them, providing positive identification.
Be one of the people who notice Mars visiting our night sky. Be one of the people who look even deeper into our solar system to see what few have seen -- Vesta. Be one of the people who revel in exploring the firmament.
