Astronomers have discovered stars that were hiding in plain sight within our Milky Way galaxy. An international team of scientists observed nearly one billion stars over 10 years using infrared light, which allowed them to see through dust and gas and find stars that were previously invisible.

Some of the stars they discovered were newly formed “protostars” that experience giant outbursts for months or even decades as they form new planetary systems.

Most of these young stars emit their light in infrared wavelengths because dust blocks visible light. Seeing them in infrared for the first time helped astronomers understand more about how stars and planets are born.

The researchers also spotted an unexpected new type of aging giant star they nicknamed “Old smoker.” Located in the center of our galaxy, these mysterious stars can stay quiet for decades before suddenly erupting with clouds of smoke.

To learn more about these unusual objects, the scientists used the Very Large Telescope in Chile to take detailed spectra – which show what wavelengths of light the stars emit.

The study was led by Professor Philip Lucas from the University of Hertfordshire in the UK. His team monitored hundreds of millions of stars and selected 222 that showed the largest changes in brightness over 10 years. Two-thirds of the stars could be easily classified, but the rest required closer study with the powerful telescope spectra.

One of the main goals was to find protostars during their rare giant outbursts. The researchers discovered 32 erupting protostars that increased in brightness by at least 40 times, and in some cases over 300 times.

Being able to observe so many outbursts over time will help astronomers understand how young stars grow.

However, the most unexpected finding was 21 aging red giant stars near the center of the Milky Way that showed ambiguous brightness changes. Analysis revealed they belong to a brand new type of giant star.

Known as “Old smokers”, these elders can stay dormant for decades before suddenly ejecting thick clouds of smoke – a behavior previously unknown to science.

The locations of the Old smokers provide an important clue, as they are concentrated in the densest part of our galaxy where stars contain more “heavy elements” like iron.

The astronomers hope to learn more about how these mysterious giants redistribute star and planet-forming materials throughout the galaxy. Their discovery may change our understanding of how elements spread through space over cosmic time.


Royal Astronomical Society | P W Lucas, L C Smith, Z Guo,et al., The most variable VVV sources: eruptive protostars, dipping giants in the nuclear disc and others, Monthly Notices of the Royal Astronomical Society, Volume 528, Issue 2, February 2024, Pages 1789–1822, | Zhen Guo, P W Lucas, et al., Spectroscopic confirmation of high-amplitude eruptive YSOs and dipping giants from the VVV survey, Monthly Notices of the Royal Astronomical Society, Volume 528, Issue 2, February 2024, Pages 1769–1788, | Carlos Contreras Peña, Philip W Lucas, et al., On the incidence of episodic accretion in Class I YSOs from VVV, Monthly Notices of the Royal Astronomical Society, Volume 528, Issue 2, February 2024, Pages 1823–1840,

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