Vega Stands Alone: No Planets Found in Recent Observations

How many times does it happen to stop staring at one specific star when stargazing, wondering if other planets surround it? One of those stars, probably, was Vega, and there is bad news: it seems nothing orbits it, apart from some debris.

Vega position in the night sky — *Vega’s position in the night sky. Credits: Stellarium*

All eyes are on Vega

Vega is one of the brightest stars in the northern hemisphere, so it’s not surprising that it was among the first stars to be supposed to have planets around it. Immanuel Kant presented this idea in 1775, but the first useful observations were made no earlier than 1984 when NASA’s InfraRed Astronomy Satellite (IRAS) detected a shell of dust around the star.

*An artistic concept that illustrates an asteroid belt around Vega. Credits: NASA/JPL-Caltech*

Since then, Vega was the objective of many other observations among which we find the ALMA in Chile and the Herschel Space Telescope of ESA, but none of them was able to obtain much detailed images. Things, however, changed when both the Hubble and the Webb Telescope started collaborating, providing a resolution never seen before.

What’s going on around Vega

All these observations revealed the presence of a disk of debris around Vega with a diameter of 100 billion miles. According to Andras Gáspár of the University of Arizona, this disk is different from other circumstellar disks studied before. It appears to be very smooth, with no clue revealing the presence of one or more large planets cleaning it up. By observing the pictures taken by the Hubble and the JWST we can see that, apart from a layer at 60 AU (twice the distance of Neptune from the Sun) from the star, this disk has no gap all the way in until the glare of the star covers our vision.

[left] A Hubble Space Telescope false-color view of a 100-billion-mile-wide disk of dust around the summer star Vega. Hubble detects reflected light from dust that is the size of smoke particles largely in a halo on the periphery of the disk. The disk is very smooth, with no evidence of embedded large planets. The black spot at the center blocks out the bright glow of the hot young star. [right] The James Webb Space Telescope resolves the glow of warm dust in a disk halo, at 23 billion miles out. The outer disk (analogous to the solar system’s Kuiper Belt) extends from 7 billion miles to 15 billion miles. The inner disk extends from the inner edge of the outer disk down to close proximity to the star. There is a notable dip in surface brightness of the inner disk from approximately 3.7 to 7.2 billion miles. The black spot at the center is due to lack of data from saturation. NASA, ESA, CSA, STScI, S. Wolff (University of Arizona), K. Su (University of Arizona), A. Gáspár (University of Arizona) — The disk of dust around Vega as seen from the Hubble (left) and the James Webb (right). Credits: NASA, ESA, CSA, STScI, S. Wolff (University of Arizona), K. Su (University of Arizona), A. Gáspár (University of Arizona)

We must remember that stars are born inside clouds of cold dust and gases. The remaining material aggregates into a disk around the newly born stars, and from this, planets usually start to form. However, some dust remains, and minor bodies contribute to feeding it from collision and material ejection. This dust is shoved around by planets, giving us the possibility to detect indirectly the presence of exoplanets.

The instruments

The JWST represents the edge of space telescope technology and, since its launch, it has already revolutionized our knowledge of the Universe. It is working to solve mysteries all over the Universe, from our neighbors in the Solar System to the edge of the observable Universe. During this study, the JWST captured images of the circumstellar disk around Vega using the Mid-InfraRed Instrument (MIRI).

*Graphic illustration of the James Webb Space Telescope. Credits: NASA*

The Hubble Space Telescope is probably the most iconic telescope orbiting our planet. During its three decades of activities, it amazed us with its high-resolution images of the wonders of the cosmos. Its contribution to the Vega observation consisted in acquiring images of the disk with the Space Telescope Imaging Spectrograph (STIS).

*Hubble in Low Earth Orbit. Credits: NASA*

The study results

From Vega’s observations, it seems that there are no planets like the gas giants that, in our Solar System, prevent dust from spreading. The question astronomers are now asking is: why Vega couldn’t form planets? What’s the difference with other stars like the Sun?