Slip-slidin’ away. Always liked the title of that Paul Simon song. This week you can watch Jupiter slip slide under Venus in the west in evening twilight. For months now, Jupiter stood above Venus, but the combined movement of Venus away from the sun and Jupiter toward it have conspired them to bring them together. They’re closest tonight at just 3 degrees apart but will part company thereafter. Sweet sorrow.
Facing the northeast two nights ago, I noticed the bright spring star Arcturus making its push into the evening sky around 9-10 p.m. Look for it well below the Handle of the Big Dipper. Together with Mars and the Dipper’s Alkaid, the three form a big triangle across the eastern sky.
Notice that the triangle includes another smaller triangle within its borders – the three stars that form the rump of Leo the Lion. Further up and to the right of Mars, the “Backwards Question Mark” figure defines the lion’s head.
Mars is due south and highest around midnight. As the night rolls on, Arcturus rise higher and higher until it’s due south at dawn. If you’re out that late, take a look to the right of the last quarter moon, and you’ll spot a third red luminary, the bright star Antares in Scorpius.
No matter when you go out you’re likely to see an occasional stray meteor. The later you’re up, the more meteors you’re likely to see. No, we’re not in the midst of a shower – the next one won’t be until late April – but the number of meteors changes overnight because of the Earth’s motion.
After sunset and before midnight, the hemisphere you’re standing on faces opposite Earth’s orbital motion. We’re literally on the trailing side of the planet as Earth orbits the sun. Any meteoroids headed our way have to play catch up, traveling at least 18 miles per second (Earth’s orbital speed) to reach the atmosphere and burn up as meteors.
After midnight, Earth has rotated far enough around so that our hemisphere faces “into the wind”. We’re moving forward along our orbit and straight into anything that might be in our path. No longer do meteoroids play catch up; instead we hit ’em head on.
It’s like watching a rain or snow storm from the rear window while driving down the freeway. Not much to see when all the action’s up at the front window. On any old night, when no meteor showers are active, we see about 2 to 6 random or sporadic meteors per hour before midnight. In the wee hours, that number can rise to better than a dozen.
If you’re really, really lucky, one of those meteors might flare as a fireball, survive atmospheric passage and land right on your roof. That’s just what happened yesterday when a meteorite was found in Margaret Anne Thomasson’s garden in Oslo, Norway after punching a hole in the roof of her house. Half of it was still stuck in the ceiling.
The 1-lb. 4 oz. meteorite was almost certainly a fragment from a widely-witnessed fireball on March 1. Take a look at this Norwegian TV video of Earth’s newest visitor – there are some great closeups of the fresh, matte-black crust and fragmented interior along with lively discussion from astrophysicist Knut Jorgen Roed Odegaard and his wife Anne Mette Sannes. It helps to know Norwegian of course. If you don’t, here’s a short article about the fall in English. For the moment, Margaret plans to just look at the meteorite a while before deciding what to do with it.
The meteorite, which appears to be a chondrite or common type of space rock, shows a broken texture that tells us in a graphic way, that the asteroid from which it originated must have been struck by another asteroid in the distant past. Asteroid hitting asteroid creates shattered rock mixes called breccias (bretch-chas) that are cemented together by heat and pressure. Will the solar system never stop beating up on itself?