Exciting Kepler News – Part 1: Mini-Planetary System


There were two exciting Kepler (the NASA mission tasked with discovering planets outside of our solar system) news releases today. I’ll cover them in two separate posts. This is Part 1; stay tuned for Part 2.

KOI-961 Artist Concept

(Click to englarge / Image credit: NASA/JPL-Caltech)

Announced today was the discovery of the three smallest exoplanets (planets orbiting a star other than the Sun) ever discovered. These planets are orbiting a red dwarf star, currently1 named KOI-961 (KOI = Kepler Object of Interest). These planets are all smaller than our home planet, having a radius of .78, .73, and .57 that of Earth’s. (The smallest is about the size of Mars.) Though the planets are thought to be rocky, they orbit KOI-961 very closely, making them too hot to have any likelihood of being habitable.

The planets, currently 2 named KOI-961.01, KOI-961.02, and KOI-961.03, circle their host star at a fair clip, completing an orbit in less than two Earth-days. The star, KOI-961, has much less mass than our Sun. Its diameter is 1/6 the size of the Sun (which is only about 70% larger than Jupiter).

The discovery announced today came from a team of scientists, led by astronomers from the California Institute of Technology (Caltech). They made their discovery by analyzing publicly-released data from the Kepler mission. Studying KOI-961, they were able to greatly refine the preliminary estimated size of the red dwarf, and subsequently verify the presence of the three small exoplanets.

KOI-961 exoplanet comparisons

(Click to enlarge / Image Credit: NASA/JPL-Caltech)

If you’re interested in further details about how Caltech made the discovery, I highly recommend you read their press release.

So let’s take a step back and ponder about what this latest discovery means. Coupled with the many frequent previous Kepler discoveries, we’re starting to create a big picture in which planets are ubiquitous throughout the Universe. Red dwarfs are the most common type of star in at least our own galaxy, and if one red dwarf has a planetary system, it’s likely more do… maybe even most do. We’re discovering planets around different types of stars; those similar to the Sun and those considerably different. Planets of different sizes and compositions as well. Not just large gas giants with little hope for containing life, but smaller, rocky worlds. Other Earth-sized worlds. Other Earth-like orbits. Other… Earths.

The speed at which we’re making these otherworldly discoveries is astounding and encouraging. It wasn’t long ago, I sat wondering if there were other planets out there, beyond our solar system, and if they might be discovered in my life. Today, I’m overwhelmed trying to keep up with all of the new exoplanet discoveries!

This is an exciting era to live in.

  1. I say currently, because once Kepler exoplanets are confirmed, the star generally gets the designation Kepler followed by a number, and the exoplanets are named after the star, followed by a letter designation. For example, Kepler-22b orbits the star Kepler-22. The designation “b” indicates it was the second expolanet discovered in that system.
  2. See the first footnote!

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