Astronomers Detect First Light From Alien Planets

Times Staff Writer

Astronomers have for the first time measured the reflected light of planets outside our solar system, a breakthrough that could advance the search for habitable worlds in deep space.

Two teams of researchers announced their findings Tuesday about two Jupiter-sized planets 153 and 489 light-years from Earth.

The planets, designated HD 209458b and TrES-1, are in the constellations Pegasus and Lyra. They are closer to their stars than Mercury is to the sun, making them too hot to support life.

The findings, made using NASA’s Spitzer Space Telescope, are the first direct observations of alien worlds.


“I feel we’ve been blind and have just been given sight,” said Sara Seager of the Carnegie Institution, a member of one of the research teams.

The results will be published today in the online version of the journal Nature and in the June issue of the Astrophysical Review.

“Spitzer has provided us with a powerful new tool for learning about the temperatures, atmospheres and orbits of planets hundreds of light-years from Earth,” said Drake Deming of NASA’s Goddard Space Flight Center in Greenbelt, Md.

The orbiting Spitzer telescope, launched in 2003, detects objects by measuring their infrared light -- in essence, their heat.

“We’ve been hunting for this light for almost 10 years, ever since extrasolar planets were first discovered,” said David Charbonneau of the Harvard-Smithsonian Center for Astrophysics, who led one team.

All 150 or so known extrasolar planets were discovered through indirect means, by measuring the telltale wobble in the rotation of their stars or by spotting a tiny wink in a star’s light that occurs when a planet crosses in front of it. A third method involves measuring the bending of a star’s light waves to reveal the size of a planet.

The two planets involved in the latest findings were also discovered indirectly. The breakthrough involves measuring the loss of heat and light when an orbiting planet disappears behind its star. By this means, the teams were able to calculate that the planets were being baked at temperatures as high as 1,574 degrees Fahrenheit.

Because of this overheating, the planets have been nicknamed “hot Jupiters.”

Based on observations of the light spectrum, scientists also determined the star being orbited by HD 209458b was very much like Earth’s sun. The star of TrES-1 is smaller and cooler. Both planets complete one orbit every three days.

So far, scientists have not found small, Earth-like planets capable of developing life. But some believe it’s just a matter of time before they will be able to detect habitable worlds.



Coming into focus

Scientists have made the first direct observations of planets outside our solar system by measuring their infrared light. An artist’s rendering shows a star and its planet in visible and infrared lights.

* When viewed in visible light, the star’s brilliance overwhelms the light that is reflected by the planet.

* When viewed in infrared light, the star is less blinding and its planet perks up with a fiery glow.

Source: NASA/JPL

Los Angeles Times