Tag Archives: space

Kepler: The Mission

The Kepler Mission is to find new planets that are close to Earth in size and composition. The scientific equipment is designed to detect planets as they pass in front of their stars, which causes a tiny dip in the stars’ light.

Think of standing way out beyond the edge of our solar system and just staring at the tiny face of the Sun for a decade or more. You would see regular patterns of tiny dots moving across the face of the Sun. Those dots would be Earth, Mars, and the other planets of our solar system. Every time one of those dots moved across the sun, there would be a change in the light output from the Sun.

Now, think of the Sun as just another star in the Milky Way galaxy. Kepler is simultaneously watching over 100,000 stars, every 30 minutes, waiting for the tiny little winks of light that happen when a planet crosses in front of its sun and changes the light. The change can last an hour or a half-day, depending on the planet’s orbit and the star.

100,000 stars! Think about that for a minute. Kepler is watching 100,000 stars, searching for those stars that have planets circling them. Even more precisely, Kepler is looking for habitable planets with approximately 1-year orbits (more on that below). What are the odds of finding those planets? Pretty good, actually! The Kepler team hopes to find

  • About 50 planets the same size as Earth.
  • About 185 planets that are 1.0 to 1.3 times larger than Earth.
  • About 12% of star/planet systems will contain 2 or more planets.

So why is Kepler focusing on planets with approximately 1-year orbits? It’s practicality, actually. Kepler is staring at the same section of space for 3 or 4 years (the longer the spacecraft can last, the better for observation purposes). It is looking for repeatable “winks” of light (same dimness and position every time) and it has to see those “winks” at least 2 or 3 times to determine there is a pattern – an orbit. Any wink that is seen less than 3 times is discounted. It may be a planet with a really long orbit but Kepler won’t be around long enough to ascertain if it is or not. Any wink that is seen more than 2 or 3 times (a shorter orbit than Earth’s) probably indicates a planet too close to its star to support our kind of life. So those get discounted too. What’s left are planets that are most similar to ours in size and in distance from their stars (their Suns). And Kepler is hoping to find over 200 planets in that category. 200 planets in a tiny section of a single galaxy.

And here’s what’s really amazing. Kepler is only looking at those stars from one angle. There may be planets that don’t show up in that angle of view. So the “200+ planets” figure is even more amazing because it’s a tiny bit of space viewed from a single viewpoint. Imagine what else is out there, beyond what we can see or measure now? It’s truly mind-boggling.


Kepler: The Man

In today’s example of synchronicity, I’ve been working my way (very slowly) through The Grand Design, by Stephen Hawking and Leonard Mlodinow and today I learned why the Kepler mission is named after Johannes Kepler. I guess if I was a deep reader of astronomy, I would already know about Kepler. But I’m not, so I didn’t. Until now. It’s time to rectify this gap in my (limited) knowledge of the history of astronomy. Today, the subject of my study (prior to the Feb 11th Tweetup) is Johannes Kepler. So who was this Kepler guy and why did NASA choose his name as the Mission name?

Johannes Kepler (1571AD – 1630AD) was a German mathematican, astronomer, and astrologer, back when the latter two were  much more closely related than they are now. He was a key figure in the 17th-century scientific revolution that repudiated much of what people had believed since the time of Ancient Greece and provided the foundation for much of modern science. Kepler contributed two very notable ideas to this revolution of knowledge (1) the Kepler laws of planetary motion and (2) the Keplerian refracting telescope, which led to the modern refractive telescopes in use today.

There are three of Kepler laws of planetary motion. The first two were published in 1609 after he had analyzed astronomical observations of his mentor, Tycho Brahe (a Danish noble who was a noted astronomer as well). I understand Kepler’s first two laws:

1. The orbit of every planet is an ellipse with the Sun at one of the two foci.

2. A line joining a planet and the Sun sweeps out equal areas during equal intervals of time.

It took him a while to formulate the third law, and he didn’t publish it until 1619. This one I don’t really understand, being the non-math-brained person that I am:

3. The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

(For you science lovers that want to learn more, Wikipedia has a basic explanation of Kepler’s three laws.)

Isaac Newton later used Kepler’s laws in his own theory of gravity, about a century later. Kepler’s work was that important.

The design of the Keplerian Telescope, published as Dioptrice, was an improvement on Galileo’s original design, published in 1609. Instead of using a concave lens (as Galileo had done), Kepler’s design proposed using a convex lens. This widened the field of view significantly although it did invert the image. Why was this telescope design such a breakthrough? Kepler originally felt that this design improved on Galileo’s design because it collected more light, which increased the magnification, allowing the viewer to see more detail in the small area of sky where he was pointing the telescope. It also allowed a way to insert a measuring device into the area being viewed, the first time anyone could then measure the distance between two objects over time.

The big downside of both Galileo’s and Kepler’s designs were that they required really long telescopes to overcome the abberations of the simple objective lens, along the lines of 130 to 150 feet for a lens was six inches across. Kepler never actually built a telescope using his design; he considered his design as purely theoretical. People did later build a Keplerian telescope, but it was hard to use, given the very long tube length required (the drawing above shows a 45-meter version built in 1673). Given the materials of the day used to construct the tube, it was almost impossible to keep it from bending and therefore affecting the images. (In 1668, Robert Hooke demonstrated the use of mirrors inside the tube to reflect the images and shorten the tube, a major breakthrough. A telescope formerly 60 feet long could now be shortened to 12 feet long, and that was much easier to support and stabilize.)

As part of his study of optics, Kepler wrote Astronomiae Pars Optica (The Optical Part of Astronomy) in 1604, which is generally regarded as the first description of how humans see images as inverted and reversed by the lens of our eye onto the retina.

Kepler was into a lot of things. He also explained that tides are caused by the Moon, discovered that Sun rotates about its axis, investigated the formation of pictures with a pin hole camera, and designed eyeglasses for near- and far-sightedness. (I especially appreciate that last bit, being someone who has needed vision correction since third grade!)

In one more example of synchronicity, an European unmanned resupply spacecraft is scheduled to deliver cargo to the International Space Station in February 2011. The name of that vehicle? The Johannes Kepler ATV-002 (Automated Transfer Vehicle).

It’s an amazing thing to dive into the life and work of someone I never heard about, not being the scientific type in school or in life. I’m playing catchup now, and the two hours I’ve just spent reading an introduction to Kepler’s life and work makes me realize how much I have to learn. It’s a journey, though, and today is just the second step on what I think will be a deepening of my fascination with the starry, starry night sky and the worlds we have yet to find and explore.

Kepler: First Contact

I’m so excited — I’m going to the NASA Tweetup at Ames Research Center on February 11! I am one of only 100 tweeters invited (it was a lottery drawing from all applicants) so I want to study up on what they’re doing at Ames and be able to really absorb everything I can while I’m there.

The two projects we’ll be focusing on are the Kepler and SOFIA missions. I am studying Kepler first because its mission statement really grabbed me: Kepler: A Search for Habitable Planets. Wow, like something out of sci-fi movie, only it’s reality right NOW! The picture here is of a Kepler-10b, a rocky planet about 1.4 times the size of Earth, announced on January 10, 2011. It took eight months of Kepler data to make the calculations that discovered Kepler-10b. I’m reading up on how the Kepler telescope works tomorrow.

Kepler is only looking at a very small part of the Milky Way. How small? Well, check out this graphic from NASA that shows the Kepler’s area of concentration. Go on, click on the graphic and it will display larger and then you can really try to grasp how huge our galaxy is (and we’re only one galaxy, there are so many more out there, it’s mind-blowing, seriously!).

Next time you look up in the night sky and see the constellations of Cygnus and Lyra constellations in our Galaxy, think of Kepler, looking there for more planets, more chances to find new places, and perhaps, new races.

Interested in reading more about Kepler’s mission? Here you go: Kepler Mission on the NASA web site.