Kepler Discovers Planets-like Objects Hotter Than Stars

Possible habitable zones around stars. Credit: Kepler mission

The Kepler mission announced the discovery of 5 new extrasolar planets today at the American Astronomical Society meeting in Washington, DC, each with some very unusual properties. But additionally, the space telescope has spotted some Jupiter-sized objects orbiting stars, and these objects are hotter than the host star. The science team has no idea what these objects could be, but they are part of 100 planetary candidates Kepler has observed that are still being analyzed.

The Kepler mission’s objective is to search for Earth-size planets in the habitable zones of other stars, and the planets announced today are comparable in size to Neptune, Jupiter and the other gas giants of our solar system but are substantially less dense. This first set of five new planets discovered by the Kepler mission was discovered in the first six weeks of the telescope’s operation. “The quick discovery indicates that Kepler is performing well,” said William Borucki, from NASA’s Ames Research Center.

One of these new planets is similar in many ways to Neptune, although its irradiation level is much higher. A second planet is one of the least dense planets ever discovered, and along with the other three, confirms the existence of planets with densities substantially lower than those predicted for gas giant planets. Borucki said Kepler 7b has the density of styrofoam, at .17 grams per cubic centimeter, basically a density of zero.
The smallest planet, Kepler 4b, is 4.31 earth radii, or about Neptune-sized. The other four about the size of Jupiter. All five planets have short orbital periods, and follow-up observations will be made with ground-based telescopes.

Since these planets are close to their host stars, they are very hot, hotter than about 1500 K. 1300 K is the temperature where molten lava flows.

Kepler launched in March 2009 and the mission is expected to last 3½ years. The team now has an additional 8 months of data are now available to analyze. Borucki said in 2010 Kepler will focus on the discovery of smaller planets, with an Earth-sized planet being the “holy grail” of exoplanet discoveries.
Other objects detected by Kepler include unusual variable stars, including binaries, oscillating stars, pulsating variables, and more, including other extrasolar planets, but declined to divulge more, saying his team has to be patient and do the confirmations on all the objects before.

Borucki also said data from Kepler will be released to the public on a regular basis starting in June 2010.

Source: AAS Press conference

No Earth-Sized Planet Hunting for Kepler Until 2011

A glitch in the Kepler spacecraft’s electronics means the space telescope will not have the ability to spot an Earth-sized planet until 2011, according to principal investigator William Borucki. Noisy amplifiers are creating noise that compromises Kepler’s view, and the team will have to generate and upload a software fix for the spacecraft. “We’re not going to be able to find Earth-size planets in the habitable zone — or it’s going to be very difficult — until that work gets done,” said Borucki, who revealed the problem last week to the NASA Advisory Council.

The team knew about the problem before launch, as the noisy amplifiers were noticed during ground testing before the device was launched. “Everybody knew and worried about this,” says instrument scientist Doug Caldwell. But he said the team thought it was riskier to pry apart the telescope’s electronic guts than to deal with the problem after launch.

Kepler launched on March 6, 2009 and is designed to look for the slight dimming of light that occurs when a planet transits, or crosses in front of a star.

The problem was is caused by amplifiers that boost the signals from the charge-coupled devices that form the heart of the 0.95-metre telescope’s 95-million-pixel photometer, which detects the light emitted from the distant stars. Three of the amplifiers are creating noise, and even though the noise affects only a small portion of the data, Borucki says, but the team has to fix the software — it would be “too cumbersome” to remove the bad data manually — so that it accounts for the noise automatically.

The team is hoping to fix the issue by changing the way data from the telescope is processed, and looks to have everything in place by 2011.

Borucki pointed out that the team was probably going to have to wait at least three years to find an extrasolar Earth orbiting in the habitable zone anyway. Astronomers typically wait for at least three transits before they confirm a planet’s existence; for an Earth-sized planet orbiting at a distance similar to that between the Earth and the Sun, three transits would take three years. But Borucki said that the noise will hinder searches for a rarer scenario: Earth-sized planets that orbit more quickly around dimmer, cooler stars — where the habitable zone is closer in. These planets could transit every few months.

The delay for Kepler could mean ground-based observers could now have the upper hand in the race for the holy grail of planet hunting: finding an Earth-like planet.

Kepler and CoRoT (Convection, Rotation and Planetary Transits) both look for transiting planets while the ground-based telescopes use radial velocity, looking for tiny wobbles in the motion of the parent stars caused by the planets’ gravity. The journal Nature quoted astronomer Greg Laughlin from the University of California at Santa Cruz, saying that the delay for Kepler makes it “more likely that the first Earth-mass planet is going to go to the radial-velocity observers”.

Source: Nature

Kepler’s Third Law

Johannes Kepler

“The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit” That’s Kepler’s third law. In other words, if you square the ‘year’ of each planet, and divide it by the cube of its distance to the Sun, you get the same number, for all planets.

(The other two are “the orbit of each planet is an ellipse with the Sun at a focus”, and “a line between a planet and the Sun sweeps out equal areas in equal times”.)

Copernicus, Kepler, and Newton dealt a one-two-three knockout blow to the idea – thousands of years old – that the Sun (and planets) moved around the Earth. Copernicus put the Sun at the center, Kepler modified Copernicus’ circular motions (and provided a simple, quantitative description of the actual motion), and Newton explained how it all worked (gravity).

Kepler worked out his three laws from detailed records of observations of the positions of the planets (known at the time, Mercury, Venus, Mars, Jupiter, and Saturn) – especially Mars – painstakingly compiled by Tycho Brahe.

Kepler’s third law (in fact, all three) works not only for the planets in our solar system, but also for the moons of all planets, dwarf planets and asteroids, satellites going round the Earth, etc. Well, not quite; if the secondary body – a planet, say – has a mass that’s a significant fraction of the primary one (the Sun, say), then the law needs a small tweak.

By showing how Kepler’s laws could be derived from his universal law of gravitation, Newton united heaven and earth, perhaps the greatest revolution in science (OK, Darwin’s revolution may be greater). Before Newton, the heavens were thought to work according to rules quite different from the ones which governed things on Earth.

NASA’s Imagine the Universe! has a neat demonstration of Kepler’s laws, and this PDF file (from the University of Tennessee Knoxville’s Maths Department) gives a simple derivation of Kepler’s laws, from Newton’s universal law of gravitation.

Universe Today articles with more information: Kepler’s Laws, Let’s Study Law: Kepler Would Be So Proud, and Happy Birthday Johannes Kepler.

Gravity, an Astronomy Cast episode, also discusses Kepler’s third law, as does Where is the Center of the Universe?.

Happy Birthday Johannes Kepler!


December 27 is a day to celebrate the life of astronomer Johannes Kepler, who was born on this date in 1571, and is best known for his three laws of planetary motion. But also, coming up in 2009, The International Year of Astronomy (IYA) will celebrate the work of Kepler as well. Not only did Galileo begin his observations with a telescope almost 400 years ago in 1609, but also in that year Kepler published his book New Astronomy or Astronomia Nova. This was the first published work that documented the scientific method.

Kepler’s primary reason for writing Astronomia Nova was to attempt to calculate the orbit of Mars. Previous astronomers used geometric models to explain the positions of the planets, but Kepler sought for and discovered physical causes for planetary motion. Kepler was the first astronomer to prove that the planets orbited the sun in elliptical paths and he did so with rigorous scientific arguments.

An offshoot of Astronomia Nova was the formulation of concepts that eventually became the first two of Kepler’s Laws:

First Law: The orbit of a planet about the Sun is an ellipse with the Sun’s center of mass at one focus.

Second Law: A line joining a planet and the Sun sweeps out equal areas in equal intervals of time.

And Kepler’s third Law: The squares of the periods of the planets are proportional to the cubes of their semi-major axes.

Kepler was also instrumental in the development of early telescopes. He invented the convex eyepiece, which allowed an expanded field of vision, and discovered a means of determining the magnifying power of lenses. He was the first to explain that the tides are caused by the Moon and the first to suggest that the Sun rotates about its axis. He also was the first to use stellar parallax caused by the Earth’s orbit to try to measure the distance to the stars.

While Kepler remains one of the greatest figures in astronomy, his endeavors were not just limited to this field. He was the first person to develop eyeglasses designed for nearsightedness and farsightedness, the first to investigate the formation of pictures with a pin hole camera, and the first to use planetary cycles to calculate the birth year of Christ. He also formed the basis of integral calculus.

Kepler’s many books provided strong support for Galileo’s discoveries, and Galileo wrote to him, “I thank you because you were the first one, and practically the only one, to have complete faith in my assertions.”

Original News Source: The Writer’s Almanac