---
title: "Hubble survey finds weak stellar winds in metal-poor massive stars"
description: "University of Utah-led study of 29 stars offers clues to why early galaxies looked so different"
author: "rews desk"
published: 2026-09-30T00:31:30.785Z
modified: 2026-09-30T01:15:02Z
url: https://rews.cc/a/hubble-survey-finds-weak-stellar-winds-in-metal-poor-massive-dffaa7
language: en
tags: ["astronomy", "stars", "hubble", "webb", "universe", "science"]
publisher: "Rews (https://rews.cc)"
---

# Hubble survey finds weak stellar winds in metal-poor massive stars

*University of Utah-led study of 29 stars offers clues to why early galaxies looked so different*

By rews desk · September 30, 2026 · https://rews.cc/a/hubble-survey-finds-weak-stellar-winds-in-metal-poor-massive-dffaa7

## In brief

- Hubble survey TEMPOS studied 29 massive stars in six low-metallicity dwarf galaxies
- Stellar winds drop off far more sharply below about 10% of the sun’s metallicity than expected
- Findings could help explain unusual properties of galaxies seen by the James Webb Space Telescope
- Study led by Grace Telford of the University of Utah, published Sept. 21 in The Astrophysical Journal Supplement Series
- Team is now adding Keck Observatory data and will release spectra via NASA’s Mikulski Archive

A University of Utah-led team has published a Hubble Space Telescope survey of 29 massive stars in six nearby dwarf galaxies, finding that stars with very low metal content produce markedly weaker stellar winds than expected, according to a paper published on Sept. 21 in *The Astrophysical Journal Supplement Series*.

The survey, called the Treasury of Extremely Metal-Poor O Stars, or TEMPOS, used ultraviolet observations from Hubble’s Cosmic Origins Spectrograph to study stars whose chemical composition resembles that of stars in the universe’s earliest galaxies, according to the [study](https://iopscience.iop.org/article/10.3847/1538-4365/ae95f6).

“Webb opened up a whole bunch of new questions about the evolution of these early galaxies -- they’re weird,” said Grace Telford, an assistant professor in the Department of Physics & Astronomy at the University of Utah and the study’s lead author. “That’s the scientific motivation behind the TEMPOS program: to help understand what is going on in these early galaxies.”

The James Webb Space Telescope, which launched in 2021, has returned observations of galaxies from the early universe that do not match predictions built on nearby, metal-rich galaxies like the Milky Way, according to the University of Utah. Massive stars, which are more than 10 times the mass of the sun, are thought to drive much of that difference by heating and shaping the gas around them before ending their short lives as supernovae, Telford said.

“They burn very hot, bright and fast and they end their short lives as supernova explosions that deposit a lot of energy and material into the surrounding gas,” Telford said. “They govern the evolution of their host galaxies by heating and essentially regulating the gas that’s then available to cool and form into new stars.”

Because the universe’s first galaxies had far fewer elements heavier than hydrogen and helium than galaxies do today, astronomers cannot rely on models of Milky Way stars to interpret them, according to Telford. TEMPOS instead targeted 29 stars in six local dwarf galaxies with metallicities below one-fifth that of the sun, combining 12 newly observed stars with previously collected data.

Each star required up to 35 hours of Hubble observing time, according to Telford. “It’s a sample of 29 stars, which doesn’t sound like a lot, but when each one costs up to 35 hours of Hubble time to observe, it gets really expensive,” she said.

## A sharp drop in wind speed

Massive stars continually shed material through stellar winds, and astronomers had expected wind strength to decline steadily as metallicity falls, because metal ions couple a star’s radiation to the surrounding gas. The TEMPOS data confirmed that overall trend but found it accelerates sharply among stars with metallicity below about 10% of the sun’s, according to the study.

“There’s sort of a smooth trend and then suddenly for lowest-metallicity stars, the wind speed really drops off,” Telford said. “I was so excited to find that fun surprise in the data.”

If extremely metal-poor stars lose less mass to weaker winds, they may retain more of their original mass, altering how they evolve, die and influence the galaxies around them, according to the researchers.

## Iron versus oxygen

The team also measured iron absorption features in the stars’ ultraviolet spectra, a difficult task in metal-poor environments where astronomers usually estimate overall metallicity from oxygen levels instead, because oxygen produces brighter, more easily observed signals. The assumption that iron and oxygen abundances track each other is not guaranteed, according to the study.

TEMPOS found that stars in more oxygen-rich galaxies tend to show much stronger iron absorption than stars in oxygen-poor galaxies, with wide variation in iron abundance among the metal-poor sample. “This is the first time we’ve had the statistical power to see that trend across a large sample of stars in six galaxies, all with different chemical compositions,” Telford said. “TEMPOS gives us the foundation for determining how massive-star physics changes as iron abundance changes in the very low-metallicity regime.”

Telford said her earlier attempts to model this behavior relied on just three stars. “With only three, you don’t see these trends,” she said. “We’ve always just been stuck in this low-number statistics regime, so this is our very best attempt to build a big enough sample to do something more useful.”

The TEMPOS collaboration includes researchers from the Space Telescope Science Institute, Rutgers University, the University of Texas at Austin, Christian-Albrechts-Universität zu Kiel, Rensselaer Polytechnic Institute, Princeton University and the University of Notre Dame, according to the university. The observations were funded through NASA Hubble grants GO-16767, GO-16920 and GO-17491, the university said.

The team is now combining the Hubble ultraviolet spectra with visible-light data from the Keck Observatory in Hawaii to model the stars’ chemical abundances and mass-loss rates in greater detail, according to Telford. The survey’s ultraviolet spectra will be made publicly available through the Mikulski Archive for Space Telescopes, the university said.

## See also

- [TEMPOS project page](https://ogtelford.github.io/tempos) — ogtelford.github.io · Official page for the Hubble Treasury program and its team
- [arXiv preprint of the TEMPOS study](https://arxiv.org/abs/2609.20928) — arxiv.org · Free preprint version of the paper