Astronomers see exozodiacal light from vanished comets, pulverized asteroids
The Milky Way (at left) and zodiacal light cone (right) tower over the ESO’s Very Large Telescope (VLT) at Paranal Observatory in Chile. The zodiacal light originates in the scattering of sunlight by dust left by vaporizing comets and asteroid collisions spread through the plane of the solar system and coinciding with the band of the zodiac constellations. Credit: Yuri Beletsky (LCO) ESO
Earth’s not the only planet where you can see the glowing cone of zodiacal light in the east before dawn this month. Using the four 70.9-inch (1.8-m) Auxiliary Telescopes at the European Southern Observatory (ESO) in Chile, a team of astronomers observed 92 nearby stars to probe both hot and reflective dust close to their habitable zones where Earth-like planets might be found. The search netted nine stars with an alien version of zodiacal light aptly named “exozodiacal”.
Vaporizing comets and asteroid collisions create the material which collects in the plane of the solar or star system. Sunlight reflecting off the tiny particles creates a finger or skinny pyramid of light reaching up from the eastern horizon before dawn in fall and the western horizon after dusk in spring.
Artist’s view from an imagined planet around a nearby star shows the brilliant glow of exozodiacal light extending up into the sky and swamping the Milky Way. This light is starlight reflected from hot dust created as the result of collisions between asteroids, and the evaporation of comets. The presence of such thick dust clouds in the inner regions around some stars may pose an obstacle to the direct imaging of Earth-like planets in the future.
Glowing dust around the stars in the study turned out to be a much more extreme version of the zodiacal light we see on Earth, brighter by 1000 times. Heck, that’s as bright as the Luxor Hotel beacon in Vegas. With light enough to cast shadows, there would be no need to travel to dark skies to see this (on Earth) elusive phenomenon.
Two of the four Auxiliary Telescopes used to photograph the exozodiacal light around nearby stars. The light feeds from all four telescopes were combined to create a extremely high-resolution image that could distinguish the dusty disks from the glow of their host stars. Observations were made in infrared light to better show the glowing dust. Credit: ESO / Yuri Beletsky
That’s part of the problem though. Astronomers caution that exozodiacal light could easily swamp the light of any planets orbiting near the star, making them impossible to detect with photography. One of the goals of exoplanet studies is to detect and image exo-Earths around other stars. This study reveals a potential obstacle to that:
A planet twice Earth’s mass forms a ringed dust structure in this simulation of exozodiacal dust. Enhanced dust density leads and trails the planet and causes periodic brightenings. Credit: NASA/Christopher Stark, GSFC
“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 Olivier Absil, co-author of the paper, from the University of Liege. “The presence of such dust in so many systems could therefore become an obstacle for future observations, which aim to make direct images of Earth-like exoplanets.”
You win some, you lose some. On the bright side, detecting and observing the properties of exozodiacal light will help astronomers understand the structure and evolution of solar systems around other stars. It’s important to note that the dust we’re talking about is not in the process of forming planets but created by collisions of small objects – asteroids and comets – after planets are in place. Same as in our current-day solar system.
Debris disks seen with SCUBA (Submilliter Common-User Bolometry Array), including (l-to-r) Tau Ceti, Epsilon Eridani, Vega, Fomalhaut and Eta Corvi. The disks are shown to the same physical scale i.e. as if all at one distance. Sketches at the bottom demonstrate the disk orientations, and the star symbols are at the stellar positions. Credit: SCUBA-2 Survey
Whenever a study breaks fresh ground, we often have to reconsider earlier hypotheses or theories based on new evidence. By analyzing the properties of the stars surrounded by a disc of exozodiacal dust, the team found that older stars had more dust. This result was surprising because dust production caused by collisions of asteroids (and evaporation of comets) should diminish over time, as their number is reduced.
Our solar system’s zodiacal light has been putting on a great show this month, though the Moon will soon put a temporary stop to that. Our next viewing opportunity runs from November 20 through December 3. Face east-southeast 2 hours to 90 minutes before sunrise from a dark site. While bundled in your winter coat, take a minute to contemplate the endo and exo of it all.
This entry was posted in Uncategorized and tagged asteroids, comets, dust, exozodiacal light, VLT, zodiacal by astrobob. Bookmark the permalink.
- See more at: http://astrobob.areavoices.com/2014/11/03/astronomers-see-exozodiacal-light-from-vanished-comets-pulverized-asteroids/#sthash.0OxVxgbA.dpuf
No hay comentarios :
Publicar un comentario