Planets, Planets Everywhere

They seem to be coming out of the woodwork! Well, not the woodwork, but just about everywhere we look in our home galaxy, the Milky Way. Planets, exoplanets to be more accurate. Look and you will find.

Seems ever since the first humans checked out the night sky we wondered if there might be others out there, living among the stars. It took a while for astronomers to have the technology to turn suspicion into fact. The first observations indicating an exoplanet came in 1917, but no one seemed to pay attention.

The first confirmed exoplanet discovered, in 1992, turned out to be a group of planets, orbiting a Pulsar, a rapidly spinning neutron “star” that shoots jets of plasma from its poles. When the jets are in just the right orientation as viewed from Earth, they are detected as rhythmic pulses of energy. Orbiting a pulsar is probably not conducive to life. That’s OK, it was a beginning. After this discovery interest in exoplanets went from meh to Wow! The floodgates opened.

Since that first exoplanet discovery, various Earth-bound instruments and space-based craft have been busy hunting down planets beyond our solar system. The big limitation, distance. It’s hard enough to study objects like stars in our own galaxy. Forget about looking in our closest neighbor galaxy, M31, the Andromeda Galaxy. It’s 2.5 million light years from us! Stars and their accompanying planets in our home galaxy are at most 80,000 light years away, and that’s a challenge.

How have we been doing? Not bad. To date over 5,500 exoplanets have been discovered, orbiting within over 4,000 planetary systems. Just bear in mind that finding exoplanets depends on factors such as their size, distance from their star, and orbital orientation. So, 5,500 is a conservative number. Plus, astronomers are still sifting through data collected years ago, by spacecraft long since retired, such as Kepler. Just recently astronomers reported finding in Kepler data 7 planets orbiting a Sun-like star. It’s a process.

So far, the vast majority of exoplanets found are not exactly places where we might find life. They are either super-hot – they orbit very close to their star, they are huge, bigger than Jupiter, or they are super-cold like Pluto. A few rocky, Earth-like planets have been discovered orbiting their star in what is termed the “habitable” zone, where conditions can exist for liquid water to exist – a must for life on Earth.

Again, there is the issue of distance.  Our closest neighbor star, Proxima Centauri, is 4.3 light years from us. We can’t just hop a rocket and check out its planets.

Ooo, and then we have the Drake Equation. In 1961 astrophysicist and a founder of SETI, Frank Drake came up with an equation to estimate the probability of civilizations in our galaxy. Back then we didn’t have a clue as to the number of planets.  We can now estimate two values – fp, the fraction of stars harboring planets, and ne, the mean number of planets that could support life. Of course, this is still a wild estimate, even a guess.

More exoplanets are in the queue, ready to be found.

What’s in the Sky?

November 12/13; late night; east-northeast: The Northern Taurid Meteor Shower peaks.

November 18: 6:30PM: Astronomy Night at Tye Preston Memorial Library in Canyon Lake