Kepler: the first data, and hundreds of possible new planets

Remember Kepler? It’s the space probe with a mission to locate planets that are similar to our own (which are our best bet to start looking for life, or at least life we’d recognise). It launched in March 2009, and started looking in June of that year.

NASA has been collecting, reviewing, and categorising that data. Today they’ve released the first bit of it.

Here’s a summary from Dynamics of Cats: check that out for links to more detail.

306 new candidate exoplanets, with 5 multiple transiting systems – ie stars with more than one planet transiting them.

The really interesting systems though are the 400 objects that the Kepler team got permission to withhold, and the data on which will be released later.

Statistically 100+ of those ought to be real planets, and probably the most interesting of all the exoplanets they found.

Prospects for extraterrestrial life: there are a lot of rocky planets out there

ScienceDaily has an article that explains why the prospects for the existence of other life in our galaxy just got a bit better.

In brief:

  1. We believe that planets that are mostly “rocky” (as opposed to gas giants like Jupiter and Saturn) and have water are the places where we’re most likely to find other life in the universe. This is because the only planet we yet know to contain life – our own Earth – is like this.
  2. Although we’re discovering more planets all the time most of them are extremely small and far away, so it’s slow going. Spotting stars – because they’re bigger and give off lots of radiation – is much easier.
  3. We’ve now seen that lots of white dwarf stars – which is the final stage of most normal stars (our Sun is one of those stars) – contain significant traces of heavy “rocky” elements and water. This implies that the systems around those stars once had rocky planets and water. That means such systems are quite common. And that boosts the chances that there’s life out there.

From the article:

Dr Farihi comments: “In our own Solar System with at least one watery, habitable planet, the asteroid belt — the leftover building blocks of the terrestrial planets — is several percent water by mass. From our study of white dwarfs, it appears there are basic similarities found among asteroid-like objects around other stars; hence it is likely a fraction of these white dwarfs once harbored watery planets, and possibly life.”

NASA’s Kepler mission to look for other planets capable of sustaining life

Tomorrow evening (US eastern time) is the earliest window in which NASA’s Kepler mission may launch. This is very exciting because Kepler’s main mission is to locate planets that are similar, and in similar positions, to our own. Planets like Earth are the ones where we’d be most likely to find life as we know it.

Nearly all of the planets we’ve spotted that are located outside our own Solar System have so far been gas giants like Jupiter and Saturn. They’re easy to spot, though, because they’re big and hot. Kepler will find smaller, rockier, Earth-like planets.

Photometer Being Lowered onto Kepler Spacecraft

There’s a huge amount of really fascinating science, from the general to the detailed, on the mission page. Here are some excerpts I really like.

How will Kepler look for extrasolar planets? By looking at stars, and watching for signs that something has moved across the front of them:

The Kepler spacecraft…will orbit our own Sun, trailing behind Earth in its orbit, and stay pointed at Cygnus starfield for 3.5 years to watch for drops in brightness that happen when an orbiting planet crosses (transits) in front of the star. Cygnus was chosen because it has a very rich starfield and is in an area of sky where the Sun will not get in the way of the spacecraft’s view for its entire orbit.

How does a transit tell us that there’s a planet there?

Transits by terrestrial planets produce a small change in a star’s brightness of about 1/10,000 (100 parts per million, ppm), lasting for 2 to 16 hours. This change must be absolutely periodic if it is caused by a planet. In addition, all transits produced by the same planet must be of the same change in brightness and last the same amount of time, thus providing a highly repeatable signal and robust detection method.

Once detected, the planet’s orbital size can be calculated from the period (how long it takes the planet to orbit once around the star) and the mass of the star using Kepler’s Third Law of planetary motion. The size of the planet is found from the depth of the transit (how much the brightness of the star drops) and the size of the star. From the orbital size and the temperature of the star, the planet’s characteristic temperature can be calculated. From this the question of whether or not the planet is habitable (not necessarily inhabited) can be answered.

What else will Kepler do?

The scientific objective of the Kepler Mission is to explore the structure and diversity of planetary systems. This is achieved by surveying a large sample of stars to:

  1. Determine the percentage of terrestrial and larger planets there are in or near the habitable zone of a wide variety of stars;
  2. Determine the distribution of sizes and shapes of the orbits of these planets;
  3. Estimate how many planets there are in multiple-star systems;
  4. Determine the variety of orbit sizes and planet reflectivities, sizes, masses and densities of short-period giant planets;
  5. Identify additional members of each discovered planetary system using other techniques; and
  6. Determine the properties of those stars that harbor planetary systems.

This is a really exciting mission to undertake during the International Year of Astronomy.