Hate spring cleaning? Dust looks inescapable, even in space, astronomers report. Nearby stars suffer from dust-diffused starlight, a new study finds, challenging observation of their alien worlds.
Astronomers using the four 5.9-foot (1.8-meter) telescopes of the Very Large Telescope Interferometer in the high deserts of Chile have spied large disks of particles in the inner, potentially habitable, regions of nine nearby stars.
The team saw starlight reflecting off individual dust particles. The dust likely originated in collisions between asteroids and melting comets in the distant past of these star systems.
Here in our solar system we call this dust-triggered glare zodiacal light: diffused sunlight from billions of tiny grains scattered in a disk that stretches from Mercury to Mars.
From our vantage point here on Earth we see zodiacal light for a few weeks out of the year in the evening or during the morning twilight as a ghostly, pyramid-shaped glow rising up from the horizon. Sometimes it's called false dawn.
"If we want to study the evolution of Earthlike planets close to the habitable zone, we need to observe the zodiacal dust in this region around other stars," said lead author Steve Ertel, from the European Southern Observatory and the University of Grenoble in France.
"Detecting and characterizing this kind of dust around other stars is a way to study the architecture and evolution of planetary systems."
In this case, the exozodiacal dust ("exo" is the prefix for astronomical objects outside our solar system) surrounding these nearby stars may create problems for future astronomers trying to hunt down and directly image planets embedded within it.
What may make the hunt even more challenging is that the observed exozodiacal light appears to be much brighter than what is seen in our own solar system—some thousand times shinier.
"The high detection rate found at this bright level suggests that there must be a significant number of systems containing fainter dust, undetectable in our survey but still much brighter than the solar system's zodiacal dust," explains co-author Olivier Absil, from the University of Liège.
"The presence of such dust in so many systems could therefore become an obstacle for future observations, which aim to make direct images of Earthlike exoplanets."
See for Yourself
Keen-eyed sky-watchers will have a chance to glimpse the ethereal zodiacal light over the course of the coming week when Earth, sun, and the plane of the solar system will be just right for the dust to light up in our skies.
The best place to spot zodiacal light is out in the dark countryside, far from city light pollution. About an hour before local sunrise, look for a faint, diffuse cone of light rising up from the eastern horizon.
At its base, the light will stretch about 20 to 30 degrees across the eastern horizon, up to the width of three fists held side-by-side. And the pyramid-shaped line will rise at least halfway up the sky as well.
But be aware that the light is tricky to spot because it's so faint. You may have even already seen it and mistaken it for the glow from distant city lights beyond the horizon or from high-altitude clouds.
Zodiacal light is roughly equal in brightness to the Milky Way, an indication of the darkness required to observe it.
It's amazing to think that this ghostly, cosmic light comes from countless dust particles that formed billions of years ago, when the Earth was still young.