Within the 1997 movie “Contact,” adapted from Carl Sagan’s 1985 novel, the lead character scientist Ellie Arroway (played by actor Jodi Foster) takes a space-alien-built wormhole ride to the star Vega. She emerges inside a snowstorm of debris encircling the star — but no obvious planets are visible.
It looks just like the filmmakers got it right.
A team of astronomers on the University of Arizona, Tucson used NASA’s Hubble and James Webb space telescopes for an unprecedented in-depth take a look at the nearly 100-billion-mile-diameter debris disk encircling Vega. “Between the Hubble and Webb telescopes, you get this very clear view of Vega. It is a mysterious system since it’s unlike other circumstellar disks we have checked out,” said Andras Gáspár of the University of Arizona, a member of the research team. “The Vega disk is smooth, ridiculously smooth.”
The massive surprise to the research team is that there is no such thing as a obvious evidence for a number of large planets plowing through the face-on disk like snow tractors. “It’s making us rethink the range and variety amongst exoplanet systems,” said Kate Su of the University of Arizona, lead writer of the paper presenting the Webb findings.
Webb sees the infrared glow from a disk of particles the dimensions of sand swirling across the sizzling blue-white star that’s 40 times brighter than our Sun. Hubble captures an outer halo of this disk, with particles no greater than the consistency of smoke which can be reflecting starlight.
The distribution of dust within the Vega debris disk is layered since the pressure of starlight pushes out the smaller grains faster than larger grains. “Several types of physics will locate different-sized particles at different locations,” said Schuyler Wolff of the University of Arizona team, lead writer of the paper presenting the Hubble findings. “The indisputable fact that we’re seeing dust particle sizes sorted out will help us understand the underlying dynamics in circumstellar disks.”
The Vega disk does have a subtle gap, around 60 AU (astronomical units) from the star (twice the space of Neptune from the Sun), but otherwise may be very smooth all the way in which in until it’s lost within the glare of the star. This shows that there are not any planets down no less than to Neptune-mass circulating in large orbits, as in our solar system, say the researchers.
“We’re seeing intimately how much variety there’s amongst circumstellar disks, and the way that variety is tied into the underlying planetary systems. We’re finding loads out in regards to the planetary systems — even when we will not see what may be hidden planets,” added Su. “There’s still a whole lot of unknowns within the planet-formation process, and I feel these recent observations of Vega are going to assist constrain models of planet formation.”
Disk Diversity
Newly forming stars accrete material from a disk of dust and gas that’s the flattened remnant of the cloud from which they’re forming. Within the mid-Nineties Hubble found disks around many newly forming stars. The disks are likely sites of planet formation, migration, and sometimes destruction. Fully matured stars like Vega have dusty disks enriched by ongoing “bumper automobile” collisions amongst orbiting asteroids and debris from evaporating comets. These are primordial bodies that may survive up to the current 450-million-year age of Vega (our Sun is roughly ten times older than Vega). Dust inside our solar system (seen because the Zodiacal light) can be replenished by minor bodies ejecting dust at a rate of about 10 tons per second. This dust is shoved around by planets. This provides a method for detecting planets around other stars without seeing them directly — just by witnessing the results they’ve on the dust.
“Vega continues to be unusual,” said Wolff. “The architecture of the Vega system is markedly different from our own solar system where giant planets like Jupiter and Saturn are keeping the dust from spreading the way in which it does with Vega.”
For comparison, there’s a close-by star, Fomalhaut, which is in regards to the same distance, age and temperature as Vega. But Fomalhaut’s circumstellar architecture is greatly different from Vega’s. Fomalhaut has three nested debris belts.
Planets are suggested as shepherding bodies around Fomalhaut that gravitationally constrict the dust into rings, though no planets have been positively identified yet. “Given the physical similarity between the celebs of Vega and Fomalhaut, why does Fomalhaut appear to have been in a position to form planets and Vega didn’t?” said team member George Rieke of the University of Arizona, a member of the research team. “What is the difference? Did the circumstellar environment, or the star itself, create that difference? What’s puzzling is that the identical physics is at work in each,” added Wolff.
First Clue to Possible Planetary Construction Yards
Positioned in the summertime constellation Lyra, Vega is one among the brightest stars within the northern sky. Vega is known since it offered the primary evidence for material orbiting a star — presumably the stuff for making planets — as potential abodes of life. This was first hypothesized by Immanuel Kant in 1775. Nevertheless it took over 200 years before the primary observational evidence was collected in 1984. A puzzling excess of infrared light from warm dust was detected by NASA’s IRAS (Infrared Astronomy Satellite). It was interpreted as a shell or disk of dust extending twice the orbital radius of Pluto from the star.
In 2005, NASA’s infrared Spitzer Space Telescope mapped out a hoop of dust around Vega. This was further confirmed by observations using submillimeter telescopes including Caltech’s Submillimeter Observatory on Mauna Kea, Hawaii, and likewise the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and ESA’s (European Space Agency’s) Herschel Space Telescope, but none of those telescopes could see much detail. “The Hubble and Webb observations together provide so rather more detail that they’re telling us something completely recent in regards to the Vega system that no one knew before,” said Rieke.
Two papers (Wolff et al. and Su et. al.) from the Arizona team will probably be published in The Astrophysical Journal.
