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New “Puffy Planet” Found

By David Reneke

A “puffy planet” has been discovered, as well as fresh evidence that asteroids have delivered water to exoplanets.

The Australian discovery of a strange exoplanet orbiting a small cool star 500 light years away is challenging ideas about how planets form. “We have found a small star, with a giant planet the size of Jupiter, orbiting very closely,” said George Zhou of The Australian National University. “It must have formed further out and migrated in, but our theories can’t explain how this happened.”

In the past two decades more than 1800 extrasolar planets have been discovered outside our solar system orbiting around other stars. The host star of the latest exoplanet, HATS-6, is classed as an M-dwarf, which is one of the most numerous types of stars in the galaxy. But because they’re cool they are also dim, making M-dwarf stars difficult to study.

HATS-6 emits only 5% of the light of our sun. The giveaway that the faint star had a planet circling it was a dip in its brightness caused as the planet passed in front of the star, observed by small robotic telescopes including telescopes at the ANU’s Siding Spring Observatory.

One of the world’s largest telescopes, the Magellan Telescope in Chile, and an amateur astronomer, TG Tan, helped the team confirm that the signal was a planet and not a blip in the system. “TG Tan ... was able to catch the transit of the planet from Perth after it had set over our horizon,” Zhou said. Subsequent observations from the Chilean telescope, and spectra taken from Siding Spring, confirmed that the planet had an orbit of just one-tenth that of Mercury, and orbits its star every 3.3 days.

The newly found planet has a similar mass to Saturn, but its radius is similar to Jupiter. Simply put, it’s a puffed-up planet! “Because its host star is so cool it’s not heating the planet up so much, so it’s very different from the planets astronomers have observed so far,” Zhou said.

The research has been published in the Astronomical Journal.

New Evidence Asteroids Seeded Earth’s Oceans

New research strongly suggests that water delivery via asteroids or comets is probably taking place in many other planetary systems, just as it happened on Earth. The research finds evidence for numerous planetary bodies, including asteroids and comets, containing large amounts of water.

These dramatic but not totally surprising research findings add further support to the possibility that water can be delivered to Earth-like planets via such bodies to create a suitable environment for the formation of life. Commenting on the findings, lead researcher Dr Roberto Raddi of the University of Warwick said: “Our research has found that, rather than being unique, water-rich asteroids similar to those found in our Solar System appear to be frequent. Accordingly, many planets may have contained a volume of water comparable to that found on the Earth.”

It’s believed that the Earth was initially dry, but this research strongly supports the view that the oceans we have today were created as a result of impacts by water-rich comets or asteroids. The claims are backed up by new findings by the William Herschel Telescope in the Canary Islands of a large quantity of hydrogen and oxygen in the atmosphere of the white dwarf star SDSS J1242+5226.

The quantities found provide the evidence that a water-rich exo-asteroid delivered the water it contained onto the star. The asteroid’s size, researchers believe, was comparable to the 900 km-wide dwarf planet, and former asteroid, Ceres. “The amount of water found is equivalent to 30–35% of the oceans on Earth”, Raddi explained.

The impact of water-rich asteroids or comets onto a planet or white dwarf results in the mixing of hydrogen and oxygen into the atmosphere, both detected in large amounts in SDSS J1242+5226. Hydrogen being the lightest element will always remain floating near the surface of the white dwarf where it can easily be detected.

There are many white dwarfs that hold large amounts of hydrogen in their atmospheres. This new study, published in the Monthly Notices of the Royal Astronomical Society, provides good evidence for an abundance of water-rich asteroids or comets around other stars than the Sun.

David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at