As one of the brightest stars in the night sky, Vega has captivated people for centuries. Now, thanks to the Hubble and James Webb telescopes, astronomers have observed it in greater detail than ever before.
A team of astronomers used both telescopes to study the debris disk surrounding Vega, uncovering an unusually smooth disk spanning nearly 99.5 billion miles.
So Smooth That Astronomers Are Baffled
Image of Vega’s circumstellar disk taken by the JWST.
The combined efforts of Hubble and the James Webb Space Telescope (JWST) were essential in making this discovery. NASA’s Hubble Space Telescope, which specializes in visible and ultraviolet spectrums, captured Vega’s outer disk by detecting light reflected off dust particles as fine as smoke.
Meanwhile, the JWST, a collaboration between NASA, the European Space Agency, and the Canadian Space Agency, observed the disk in mid-infrared, detecting the glow of warm dust in the inner disk. This enabled astronomers to examine sand-grain-sized particles orbiting closer to the star. By merging observations at different wavelengths, scientists gained a comprehensive view of Vega’s disk.
Image of Vega’s circumstellar disk taken by the Hubble Space Telescope.
According to astronomer Andras Gáspár of the University of Arizona, a co-author of the study, the disk surrounding Vega is “ridiculously smooth.” Unlike other circumstellar disks, where planets create ripples and gaps, Vega’s disk shows no signs of disturbance.
Astronomers’ initial conclusion is that the Vega system lacks large planets—at least none larger than Neptune—since such planets would likely interact with the disk. This finding is unusual, as debris disks in similar systems are typically shaped by their planets.
The astronomers’ second conclusion is that Vega’s disk is layered with dust particles of different sizes. The star’s intense light pressure pushes smaller dust grains toward the outer regions of the disk before it moves the larger grains, resulting in a stratified distribution of particle sizes across different areas.
The Stark Contrast Between Vega and Fomalhaut
Image of Fomalhaut’s circumstellar disk taken by the JWST.
Fomalhaut, a nearby star similar to Vega in age, size, and temperature, has a notably different circumstellar disk. Unlike Vega’s smooth disk, Fomalhaut’s disk features three nested debris belts.
Although researchers haven’t directly identified planets in the Fomalhaut system, irregularities in its disk suggest that large planets may be interacting with the dust. This comparison raises an intriguing question for astronomers: Why does Vega lack signs of planetary influence, while Fomalhaut, with similar conditions, appears to have them?
Observations of Vega are prompting scientists to rethink theories about planet formation and the diversity of planetary systems. Vega’s lack of large planets suggests planetary systems may be more varied than previously believed, with different initial conditions leading to unique outcomes in planetary formation processes.
There’s also another possibility. Vega’s undisturbed disk doesn’t entirely rule out the presence of planets. Smaller or distant planets could be hidden from current detection methods. If this is the case, astronomers may need to recalibrate models of planet formation and migration.
Vega’s exceptionally smooth disk defies expectations and underscores Hubble’s importance in space research. Despite its age and potential budget cuts from NASA, Hubble remains essential to complement the JWST’s observations.
Images | NASA, ESA, CSA
View 0 comments