¡SkyCaramba! Weekly astronomy blog for the week ending May 17, 2014
You could just hear Abbott and Costello.
“Hey, Abbott. Wasat?”
“I’m askin’ you. Wasat?”
Wasat is a star in Gemini around the waistline of Pollux, the twin that bears the same name as the star representing his head. It is actually a triple star about 60 light years away.
Two of the stars orbit each other so closely, they can’t be seen separately. But their combined light can be seen brightening and dimming in spectrograph observations over a six year period. Their spectra are different enough to tell that there are two of them and not just one star varying in brightness. A third star orbits them every 1,200 years and is visible in a telescope. In a few hundred thousand years, it may be possible to see all three of the Wasat stars from Earth as our sun and the Wasat system are moving toward each other.
Wasat is an Arabic word for middle. Being at Pollux’s waistline, it is the middle of the twin. But it is also close to the ecliptic, the line the sun seems to travel on as Earth goes around it. So, the reference to the middle could also mean the middle of the sky.
When American astronomer Clyde Tombaugh compared photographs taken six days apart in 1930, he found one of the objects near Wasat had moved. It became known as Pluto and for the next seven decades was called the ninth planet in the solar system. Pluto is now near a dim star in Sagittarius and is regarded as one of many dwarf planets or minor planets.
Another planet that is not hard to see and whose status as a planet is not being questioned is near Wasat this month. It is the king of the solar system planets, Jupiter.
You’ll find Gemini somewhat high in the west right as nightfall sets in. Jupiter is moving eastward until it’s closest to Wasat on May 22nd. The two will be separated by 0.5°, enough for the moon to fit snugly between them if it happened to be passing through.
In the last few days of this month, Jupiter will be clearly east of the twin, and Mercury will be approaching the other twin’s feet.
Gemini will get harder to see in June as its stars set around the same time as the sun. Jupiter will spend July on the other side of the sun. When it comes out of the glare in August’s morning skies, it will have a close call with Venus on the 18th.