Speaking of Hubble...

Reflections on Beta Pictoris

April 13, 2011 by Ray Villard
This Hubble Space Telescope view of Beta Pictoris shows a main dust disk and a much fainter secondary dust disk.

This 2003 Hubble view of the area surrounding Beta Pictoris shows a main dust disk and a much fainter secondary disk. (A coronagraph was used to block out the light from the bright star in the center.)

The recent announcement of the discovery of over 1,200 worlds whirling around other stars has accustomed us to the reality of our Milky Way galaxy being chock full of planets. These exoplanets, as they’re called, were discovered by NASA’s Kepler space observatory.

But the granddaddy of the ballooning field of exoplanet research is the blazing star Beta Pictoris, located 63 light-years away in the far southern sky.

Thirty eight years ago — long before exoplanets were ever discovered — the star got astronomers’ attention because it has an odd excess of infrared radiation (IR) for a star of its temperature.

This was identified as the IR glow of a warm dust disk encircling the star. Astronomers know that newborn planets generate dust through collisions. Take a look at our solar system: The Moon was born from a grazing blow to the Earth by a Mars-sized embryonic planet.

Where there’s dust, there could be planets too, astronomers reasoned.

In the early 1980s, a ground-based telescope revealed a pair of spike-like appendages on either side of the star. This was interpreted as an edge-on dust disk.

Beta Pic immediately became the poster child for the possibility of exoplanets (which weren’t first discovered until 1995). All through the 1980s, the somewhat abstruse Beta Pictoris photo appeared in nearly every introductory astronomy textbook and popular space books.

Through the 1990s, the Hubble Space Telescope gleaned spectroscopic evidence for a snowstorm of comets whirling around Beta Pictoris. Soon, crisp Hubble pictures showed there were in fact two disks around the star, perhaps altered by the gravitational tug of an unseen planet. Hubble had accomplished far more than anyone could have ever imagined when the Beta Pictoris disk was first imaged.

In 2009, astronomers at the European Southern Observatory photographed a planet near the star.

Now, new observations show that the planet is indeed orbiting the star according to laws of planetary motion formulated by Johannes Kepler nearly 400 years ago.

Today the much-lauded Beta Pictoris system is like an aging movie star whose celebrity status has been diminished. The Hubble Space Telescope made similar observations in 2004 and 2006 when it photographed a hot, young, Jupiter-sized planet orbiting the star Fomalhaut. The planet was seen moving along its orbit at a rate that Kepler himself would have easily calculated.