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Meet Icarus, the Most Distant Star Ever Seen

By David Reneke

Astronomers have spotted the most distant star ever seen as well as stunning auroras on Saturn.

More than halfway across the universe, an enormous blue star nicknamed Icarus is the most distant individual star ever seen. Normally it would be much too faint to view, even with the world’s largest telescopes, but through a quirk of nature that tremendously amplifies the star’s feeble glow, astronomers using NASA’s Hubble Space Telescope were able to pinpoint this faraway star and set a new distance record.

The star, harboured in a spiral galaxy, is so far away that its light has taken 9 billion years to reach Earth. It left there when the universe was about 30% of its current age. The discovery of Icarus through nature’s naturally occurring magnification boost has initiated a new way for astronomers to study individual stars in distant galaxies.

“This is the first time we’re seeing a magnified, individual star,” explained study leader Patrick Kelly, now of the University of Minnesota, Twin Cities. The cosmic quirk that makes this star visible is a phenomenon called gravitational lensing whereby gravity from a massive cluster of galaxies closer to Earth acts as a natural lens in space, bending and amplifying light.

Sometimes light from a single background object appears as multiple images. The light can be highly magnified, making extremely faint and distant objects bright enough to see.

In the case of Icarus, the magnified image is created by a galaxy cluster about 5 billion light years from Earth that sits between the Earth and the galaxy that contains the distant star. By combining the strength of this gravitational lens with Hubble’s exquisite resolution and sensitivity, astronomers can see and study Icarus.

When NASA’s James Webb Space Telescope is launched, astronomers expect to find many more stars like Icarus. Webb’s extraordinary sensitivity will allow the measurement of even more details, including whether these distant stars are rotating. Such magnified stars may even become fairly common.

Hubble’s Stunning Images of Saturn’s Brilliant Aurora

The Hubble Space Telescope has captured a series of stunning photos of Saturn showing the planet’s spectacular and breathtaking auroras over a period of 7 months.

On Earth, auroras are generated by solar winds that interact with charged particles in our magnetosphere. These charged particles, mainly protons and electrons, then rain into the ionosphere and travel along the planet’s magnetic field lines to the poles, creating lights in the night sky as other particles such as oxygen and nitrogen interact with each other.

The space-based telescope used its Space Telescope Imaging Spectrograph to study auroras in Saturn’s northern hemisphere before and after the recent summer solstice. As a tantalising prelude, previous Hubble observations of Saturn’s auroras revealed the presence of radio wave activity, which is also associated with Earth’s auroras.

“The variability of the auroras is influenced by both the solar wind and the rapid rotation of Saturn, which lasts only about 11 hours,” the Hubble team stated.

They also noticed an unexpected variable. The northern aurora displays two distinct peaks in brightness, one at dawn and another just before midnight. The latter peak, unreported before, seems to be specific to the interaction of the solar wind with the magnetosphere at Saturn’s solstice.

Other planets have auroras, too, such as Jupiter, Saturn, Uranus and Neptune. Some exoplanets also show some evidence of auroral activity. However, auroras are unique to each planet. For instance, Jupiter’s permanent aurora is not caused by solar wind but some mysterious mechanism yet to be discovered. While Saturn’s main auroral ring seems to be generated by solar wind, there are patches of it that are not, which is still a mystery.

David Reneke is an astronomy lecturer, writer and broadcaster (