All posts by Callum Tyndall

Shifting habitable zones identified around ancient stars

Astronomers have modelled the locations of habitable zones surrounding several aging stars for the first time, highlighting a move in the habitable zone as a star ages and providing unprecedented insight into how long planets can occupy said zones.

The habitable zone – also dubbed the ‘Goldilocks Zone’ – is the region around a star in which water on a planet’s surface remains liquid, making it a potential host for life.

The model, developed by Cornell University’s Carl Sagan Institute research associate Ramses M Ramirez and Carl Sagan Institute director and associate professor of astronomy Lisa Kaltenegger, is detailed in a paper released today in The Astrophysical Journal.

In the search for habitable planets, astronomers tend to observe middle-aged stars, such as our own Sun. However, the diversity of Kepler planets (exoplanets found using NASA’s Kepler telescope), suggests that around other stars, initially frozen worlds located further from their star could become habitable as that star ages.

Kepler 62f, one of the exoplanets discovered using the Kepler space telescope. Image courtesy of NASA Ames/JPL-Caltech/T. Pyle. Above: the Kepler-11 planetary system. Image courtesy of NASA/Ames/JPL-Caltech

Kepler 62f, one of the exoplanets discovered using the Kepler space telescope. Image courtesy of NASA Ames/JPL-Caltech/T. Pyle. Above: the Kepler-11 planetary system. Image courtesy of NASA/Ames/JPL-Caltech

“When a star ages and brightens, the habitable zone moves outward and you’re basically giving a second wind to a planetary system,” explained Ramirez. “Currently objects in these outer regions are frozen in our own solar system, and Europa and Enceladus – moons orbiting Jupiter and Saturn – are icy for now.”

Depending on the mass of the star, orbiting objects can stay in a habitable zone for up to 9bn years. Our own planet has been in our sun’s habitable zone for about 4.5bn years and has, as a result, seen a mass of varied life.

Ultimately though, our sun will become a red giant and those planets currently in its habitable zone will become far too hot to support life. Mercury and Venus will be engulfed by the red giant, while Earth and Mars will become rocky and scorched. The habitable zone itself will move outwards, warming outer planets such as Jupiter, Saturn and Neptune.

“Long after our own plain yellow sun expands to become a red giant star and turns Earth into a sizzling hot wasteland, there are still regions in our solar system – and other solar systems as well – where life might thrive, ” said Kaltenegger.

“In the far future, such worlds could become habitable around small red suns for billions of years, maybe even starting life, just like Earth. That makes me very optimistic for the chances for life in the long run.”

Image courtesy of Cornell University

Image courtesy of Cornell University

As the graph above shows, the planets that occupy the expanded habitable zone of a red giant, once thawed, could stay warm for up to half a billion years, and provide the potential for life.

The study of these older stars could contribute to the possibility of finding life in other regions of the galaxy, and our own understanding of Earth’s future.

Indeed, though it may be billions of years from now, it is not inconceivable that the future may see humans looking to planets such as Jupiter or Neptune as a new base for our species.

NASA has finally observed interaction between magnetic fields

When magnetic field lines from one place meet those originating from elsewhere, a process called magnetic reconnection occurs. This process sees the field lines clash and then rearrange in a reaction that throws out hot jets of particles across the boundaries that the field lines normally create.

Recently, NASA’s Magnetospheric Multiscale (MMS) mission was able to observe such a reaction, and while we have previously been able to observe the movement of protons from a field line reaction, the MMS has now, for the first time ever, been able to capture the direct measurements of the electron movement involved in the reaction.

The MMS was launched in March 2015 and passed through a magnetic reconnection event on October 16th, 2015.

Flying in a pyramid formation at the edge of Earth’s magnetic field with as little as 10km distance between four identical spacecraft, the mission provided more precise observations than ever before.

The satellites are able to image electrons within their formation once every 30 milliseconds, as opposed to their predecessor, Cluster II, which took measurements once every three seconds.

James Drake, a professor of physics at the University of Maryland and co-author on the study, explained: “Just looking at the data from MMS is extraordinary. The level of detail allows us to see things that were previously a blur. With a time interval of three seconds, seeing reconnection with Cluster II was impossible.

“But the quality of the MMS data is absolutely inspiring. It’s not clear that there will ever be another mission quite like this one.”

Images courtesy of NASA

Images courtesy of NASA

The measurements taken – and published in the journal Science – showed the electrons shooting away from the event, across boundary lines that would usually deflect them, before curving back around in response to the new magnetic fields they encountered.

This movement seems to fit a computer simulation known as the crescent model, named for the shape of the electrons’ path.

“This is the first time we have flown through the heart of a reconnection event. While the data support the crescent theory, some measurements do differ from what we might expect, throwing up new questions about the dynamics,” said  one of the reconnection event data team, Dr Jonathan Eastwood.

“Understanding the fundamental physics of this process will have a real impact on our understanding of disruptive space weather events.”

MMS

The process of magnetic reconnection is a major part of events such as geomagnetic storms, solar flares, coronal mass ejections and the auroras we can see at the North and South poles.

Beyond simply observing the process, the MMS aims to determine how the magnetic field lines briefly break, enabling the process of reconnection.

Beyond our own magnetic field, the findings from MMS may allow us to estimate systems of varying energies and provide answers to a wide range of questions in the field of astrophysics.

In the future, the MMS will travel to the side of the Earth’s field facing away from the sun to observe more varied reconnections.