Could Moons Contain Life?

According to new research, exomoons (natural satellites of planets outside our Solar System) could offer another clue about the pool of alien worlds that may be home to life.

Only a small proportion of exoplanets are likely to be able to sustain life, existing in the habitable zone of their stars. But some planets, especially large gas giants, may harbor moons which contain liquid water.

These moons can be internally heated by the gravitational pull of the planet they orbit, which can lead to them having liquid water well outside the normal habitable zones of systems that scientists are trying to find Earth-like planets in.

Researchers looked at the possibility of exomoons orbiting J1407b, a large gas giant believed to have an enormous ring system. J1407b circles a 16-million-year-old Sun-like star approximately 434 light-years away from Earth. The planet’s mass is thought to be in the range of about 10 to 40 Jupiter masses.

The rings of J1407b are shown eclipsing the young Sun-like star J1407. Image credit: Ron Miller.


Scientists ran computer simulations to model the rings around J1407b, which are 200 times larger than those around Saturn. Gravitational forces between particles were calculated and used to update the positions, velocities, and accelerations in the computer models of J1407b and its ring system. They then added a moon that orbited at various ratios outside of the rings to test whether this caused gaps to form where they expected.

The findings revealed that while the orbiting moon did have an effect on the scattering of particles along the ring edge, the expected gaps in the ring structure were unlikely to be caused by the gravitational forces of a currently unseen moon orbiting outside J1407b’s rings.

The paper was published in the Monthly Notices of the Royal Astronomical Society.

New Neighbors

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Astronomers using NASA’s Transiting Exoplanets Survey Satellite (TESS) have discovered a compact three-planet system around the star HR 858. The newly-discovered planets orbit HR 858, a slightly-evolved F-type star, which is also a member of a visual binary system. The star lies in the constellation of Fornax, approximately 104.4 light-years from Earth. It has a radius 30% larger than the Sun, and a temperature of about 10,700 degrees Fahrenheit (5,928 degrees Celsius).

Named HR 858b, c and d, the new planets are all about twice the size of Earth and have periods of 3.6, 6 and 11.2 days, respectively. This compact and near-resonant architecture harkens back to the systems of tightly packed inner planets discovered by Kepler, but HR 858 is hundreds to thousands of times brighter than the hosts of those Kepler systems.

According to the team, HR 858 is one of the brightest stars known to host transiting exoplanets, trailing only HD 219134, pi Mensae, and 55 Cancri.

Pre-launch estimates of the TESS planet yield predicted a handful of planet discoveries around naked-eye stars, and so far only HR 858 and pi Mensae have fit this description. HR 858 will likely retain its privileged position as one of the brightest transit hosts in the sky and most favorable systems for detailed study.

paper detailing the discovery will be published in a journal of the American Astronomical Society (AAS).

A Totally Metal Weather Forecast

Scientists have determined that the weather forecast on PSO J318.5-22, a mysterious object that does not orbit any star but floats freely, is pretty extreme.

Based on data from the European Southern Observatory’s Very Large Telescope in Chile, researchers from the University of Edinburgh in Scotland have determined that the orphan world’s climate consists of thick clouds of hot dust and droplets of molten iron rain. Their study was published Oct. 30 in The Astrophysical Journal

PSO J318.5-22, which is similar to a brown dwarf star and sits some 75 light-years from Earth, was discovered in 2013. The strange world is around the same size as Jupiter, but has roughly eight times the mass. The object is not massive enough to initiate nuclear fusion in its core like a star would so it glows feebly.

To observe the object, the researchers took hundreds of infrared images of PSO J318.55 over a period time.

The researchers analyzed different cloud patches, allowing them to determine weather patterns. They noted that this type of analysis would not have been possible had PSO J318.5-22 orbited a parent star, as most planets and similar objects do.

Scientists still aren’t sure why PSO J318.5-22 is isolated and free-floating in space, but there are two theories: PSO J318.5-22 may have formed as a planet around a star and got ejected from that system, or it formed in isolation, condensing out of a star-forming cloud, similar to how brown dwarfs form.