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Although most potentially habitable worlds orbit red dwarf stars, we know larger and brighter stars can harbor life. One yellow dwarf star, for example is known to have a planet teaming with life, perhaps even intelligent life. But how large and bright can a star be and still have an inhabited world? That is the question addressed in a recent article in the Astrophysical Journal.

Stable main-sequence stars such as the Sun are categorized by color or spectral type, with each type assigned a letter designation. For historical reasons the categories aren’t alphabetical. Red dwarf stars, the coolest stars with the smallest mass, are M type. Then with each brighter, bluer, and more massive category is K, G, F, A, B, and finally O. The Sun falls into the G category as a yellow star. Each spectral type is then broken into smaller sections, numbered 0 – 9. The Sun is G2 star because it is at the warmer end of G-type stars.

As you go up the scale, the potentially habitable zone shifts farther from the star but also gets larger. That makes it more likely for a planet to be in the zone. But larger stars also have shorter lives, which might not give life enough time to evolve on a world. Then there are other factors that can be harmful for life. The largest stars emit a tremendous amount of ionizing radiation, which could strip planets of their atmospheres, or sterilize the surface of a planet. Because of this, the largest stars of the B and O types aren’t likely to harbor life.

How habitable zones differ by spectral type. Credit: NASA, ESA and Z. Levy (STScI)

But what about F-type stars? They are a bit brighter than the Sun and more white than yellow in color. They are also stable for around 4 billion years, which is long enough for life to evolve and thrive. And they also emit more ultraviolet radiation, which may have helped life arise on Earth. What are the odds of a habitable F-type planet?

To answer this question, the team went through the database of known exoplanets. About 80 F-type main-sequence stars are known to have at least one planet. Of those, 18 systems have exoplanets that spend at least part of their orbit in the habitable zone of the star. And in one case, the exoplanet 38 Virginis b, the planet is always in the habitable zone. Statistically around 5% – 20% of F-type stars have potential for life.

What’s interesting about 38 Virginis b is that it is a gas giant about 4 times more massive than Jupiter, so it isn’t likely to be habitable. But it could have Earth-sized moons, similar to the Galilean moons of Jupiter. A world orbiting a Jovian planet could be a perfect home for life.

F-type stars only comprise 3% of main-sequence stars in the Milky Way, and it’s possible that their excess UV light could rule out habitable worlds. But alien astronomers might make similar arguments about G-type stars like the Sun. As this study shows, we shouldn’t rule out the Sun’s brighter cousins in the search for living worlds.

Reference: Patel, Shaan D., Manfred Cuntz, and Nevin N. Weinberg. “Statistics and Habitability of F-type Star–Planet Systems.” The Astrophysical Journal Supplement Series 274.1 (2024): 20.

The post Could Stars Hotter Than the Sun Still Support Life? appeared first on Universe Today.

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Hubble Lights the Way with New Multiwavelength Galaxy View This image from the NASA/ESA Hubble Space Telescope features the galaxy NGC 1559. ESA/Hubble & NASA, F. Belfiore, W. Yuan, J. Lee and the PHANGS-HST Team, A. Riess, K. Takáts, D. de Martin & M. Zamani (ESA/Hubble)

The magnificent galaxy featured in this NASA/ESA Hubble Space Telescope image is NGC 1559. It is a barred spiral galaxy located in the constellation Reticulum, approximately 35 million light-years from Earth. The brilliant light captured in the current image offers a wealth of information.

This picture is composed of a whopping ten different Hubble images, each filtered to collect light from a specific wavelength or range of wavelengths. It spans Hubble’s sensitivity to light, from ultraviolet through visible light and into the near-infrared spectrum. Capturing such a wide range of wavelengths allows astronomers to study information about many different astrophysical processes in the galaxy: one notable example is the red 656-nanometer filter used here. Ionized hydrogen atoms emit light at this particular wavelength, called H-alpha emission. New stars forming in a molecular cloud, made mostly of hydrogen gas, emit copious amounts of ultraviolet light that the cloud absorbs, ionizing the hydrogen gas causing it to glow with H-alpha light. Using Hubble’s filters to detect only H-alpha light provides a reliable way to detect areas of star formation (called H II regions). These regions are visible in this image as bright red and pink patches filling NGC 1559’s spiral arms.

These ten images come from six different Hubble observing programs, spanning from 2009 all the way up to 2024. Teams of astronomers from around the world proposed these programs with a variety of scientific goals, ranging from studying ionized gas and star formation, to following up on a supernova, to tracking variable stars as a contribution to calculating the Hubble constant. The data from all of these observations lives in the Hubble archive, available for anyone to use. This archive is regularly used to generate new science, but also to create spectacular images like this one! This new image of NGC 1559 is a reminder of the incredible opportunities that Hubble provided and continues to provide.

Along with Hubble’s observations, astronomers are using the NASA/ESA/CSA James Webb Space Telescope to continue researching this galaxy. This Webb image from February showcases the galaxy in near- and mid-infrared light.

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Media Contact:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov

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Last Updated

Sep 20, 2024

Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center

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