# University of Colorado Boulder builds prototype optical clock locked to iron line in sunlight

- Published: 2026-11-14 20:05 UTC
- Section: Science › Instruments & experiments
- Tags: solar optical clock, optical clock sunlight, frequency comb, iron spectral line 1565 nm, Scott Diddams, Rossiter-McLaughlin effect, radial velocity, solar oscillations, exoplanet detection, University of Colorado Boulder
- URL: https://realtech.media/news/rt-74675d3f0e37fd1e7b989868_university_of_colorado/

**Researchers locked a laser to a feature of the solar spectrum instead of an isolated atom. The setup tracked the sun's motion and could help study processes on its surface.**

![University of Colorado Boulder builds prototype optical clock locked to iron line in sunlight](https://www.computerra.ru/wp-content/uploads/2026/11/Snimok-ekrana-2026-11-14-v-11.28.34.jpeg)
*computerra.ru*

Researchers led by Scott Diddams at the University of Colorado Boulder have built an optical clock that uses light from the sun as a key component, newscientist.com reports. This type of solar optical clock had not been built before. [1]

Instead of an isolated atom, the reference is a process in the sun's atmosphere, where sunlight causes jumps in iron atoms. The authors say it could be used to diagnose shifts in the sun's velocity or to probe processes on its surface. [1]

## How the solar clock works

In a typical optical clock, an electron in an atom oscillates between two energy levels, and an ultra-stable laser is locked to the frequency of that oscillation. A frequency comb then turns visible light into microwaves that standard electronics can process. [1]

The new experiment kept the laser and the frequency comb. The laser was locked to the signature that iron atoms leave in the spectrum of sunlight, a line of neutral iron near 1565 nanometres. The team collected sunlight into a special fibre and fed it into the rest of the setup. The laser frequency was compared with a comb referenced to the SI second, so the system does not replace a time standard. [1]

## What the measurements showed

The clock does not rival the best atomic optical clocks in accuracy. The setup determined the position of the solar spectral line to about 30 centimetres per second in radial velocity after several thousand seconds of measurement, and it registered the sun's five-minute oscillations. [1]

During the partial solar eclipse of April 2024, the team observed a shift in the spectrum as the moon passed in front of the sun. This is known as the Rossiter-McLaughlin effect and is linked to the star's rotation. [1]

If the clock were fed light from a distant star, similar shifts could indicate orbiting exoplanets. That would require large telescopes, about 25 to 40 metres in diameter, and long collection times. Piet Schmidt at the National Metrology Institute of Germany notes that, as an astronomical instrument, the design does not yet surpass existing methods, and for very distant stars the faintness of their light would limit it. He sees possible advantages in studying the sun itself: eruptive events, sunspots and the solar wind. [1]

## Sources

1. [newscientist.com](https://www.newscientist.com/article/2598583-researchers-built-the-first-ever-quantum-clock-that-uses-sunlight/)
2. [computerra.ru](https://www.computerra.ru/374979/sozdany-pervye-v-mire-opticheskie-chasy-na-solnechnom-svete)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-74675d3f0e37fd1e7b989868_university_of_colorado/