More livable than Earth? New index sizes up the habitability of alien exoplanets

Image: James Webb Space Telescope

Researchers at the University of Washington’s Virtual Planetary Laboratory have devised a new habitability index for judging how suitable alien planets might be for life, and the top prospects on their list are an Earthlike world called Kepler-442b and a yet-to-be confirmed planet known as KOI 3456.02.

Those worlds both score higher than our own planet on the index: 0.955 for KOI 3456.02 and 0.836 for Kepler-442b, compared with 0.829 for Earth and 0.422 for Mars. The point of the exercise is to help scientists prioritize future targets for close-ups from NASA’s yet-to-be-launched James Webb Space Telescope and other instruments.

Astronomers have detected more than 1,000 confirmed planets and almost 5,000 candidates beyond our solar system, with most of them found by NASA’s Kepler Space Telescope. More than 100 of those have been characterized as potentially habitable, and hundreds more are thought to be waiting in the wings. The Webb telescope is expected to start taking a closer look soon after its scheduled launch in 2018.

“Basically, we’ve devised a way to take all the observational data that are available and develop a prioritization scheme,” UW astronomer Rory Barnes said Monday in a news release, “so that as we move into a time when there are hundreds of targets available, we might be able to say, ‘OK, that’s the one we want to start with.'”

This isn’t the first habitability index to be devised. Traditionally, astronomers focus on how close a particular exoplanet’s mass is to Earth’s, and whether its orbit is in a “Goldilocks zone” where water could exist in liquid form. But in a paper accepted for publication in the Astrophysical Journal, Barnes and his colleagues say their scheme includes other factors such as a planet’s estimated rockiness and the eccentricity of its orbit.

The formula could be tweaked even further in the future. “The power of the habitability index will grow as we learn more about exoplanets from both observations and theory,” said study co-author Victoria Meadows.

Barnes, Meadows and UW research assistant Nicole Evans are the authors of “Comparative Habitability of Transiting Exoplanets.” The study was funded by the NASA Astrobiology Institute.

NASA and New Horizons team pick post-Pluto target … and serve up an awesome video

NASA and the science team behind the New Horizons mission to Pluto and beyond have settled on the popular choice for the spacecraft’s next flyby: It’s 2014 MU69, an icy object a billion miles beyond Pluto that’s thought to be less than 30 miles (45 kilometers) wide.

That’s 10 times bigger than, say, the comet targeted by the European Space Agency’s Rosetta probe – but on the order of 1 percent as wide as Pluto. The New Horizons team suspects that 2014 MU69 represents a primordial object in the Kuiper Belt, the vast ring of icy material that lies beyond the orbit of Neptune.

Studying such a Kuiper Belt object, or KBO, should satisfy the mission’s post-Pluto objective of documenting the diversity of worlds at the solar system’s edge. “It is just the kind of ancient KBO, formed where it orbits now, that the Decadal Survey desired us to fly by,” New Horizons principal investigator Alan Stern said Friday in a NASA news release.

This chart shows the path of NASA’s New Horizons spacecraft toward its next potential target, the Kuiper Belt object 2014 MU69, also known as PT1. Other dwarf planets are indicated on the chart as well. (Credit: Alex Parker / NASA / JHUAPL / SwRI)
This chart shows the path of NASA’s New Horizons spacecraft toward its next potential target, the Kuiper Belt object 2014 MU69, also known as PT1. Other dwarf planets are indicated on the chart as well. (Credit: Alex Parker / NASA / JHUAPL / SwRI)

2014 MU69, also known as Potential Target 1 or PT1, was one of three objects identified after a months-long search that drew upon the observing power of the Hubble Space Telescope. Although an alternate target known as PT3 was somewhat brighter and probably bigger, PT1 was favored because there’s a 100 percent chance of reaching it with the fuel that was left on the New Horizons spacecraft after last month’s big Pluto flyby.

The New Horizons team has planned a series of four maneuvers in October and November to send the piano-sized probe toward 2014 MU69, but NASA won’t be able to give the final go-ahead for the extended mission until the team makes a formal proposal in 2016. If NASA gives the green light, the flyby is due to take place on Jan. 1, 2019.

In the meantime, New Horizons is continuing to send back imagery and other data that have been stored up since it flew past Pluto on July 14. New pictures should be released starting in a week or so.

This month, views from the Pluto flyby were mashed together with animations to produce a glorious time-lapse video. Check out this masterpiece by Southwest Research Institute’s Stuart Robbins on YouTube:

A Place for Alien Life? Kepler Mission Discovers Earth’s Older Cousin, Kepler-452b

Kepler-452b

Scientists say NASA’s Kepler Space Telescope has discovered Earth’s “older, bigger first cousin” –  a planet that’s about 60 percent bigger than our own, circling a sunlike star in an orbit that could sustain liquid water and perhaps life.

“Today, Earth is a little bit less lonely, because there’s a new kid on the block,” Kepler data analysis lead Jon Jenkins, a computer scientist at NASA’s Ames Research Center, said Thursday during a NASA teleconference about the find.

The alien world, known as Kepler-452b, is about 1,400 light-years away in the constellation Cygnus – too far away to reach unless somebody perfects interstellar transporters. But its discovery raises the bar yet again in the search for Earth 2.0, which is a big part of Kepler’s mission.

Jenkins said that Kepler-452b has a better than even chance of being a rocky planet (though there’s some question about that). Its size implies that it’s about five times as massive as Earth. He said the planet might be cloudier than Earth and volcanically active, based on geological modeling. Visiting Earthlings would weigh twice as much as they did on Earth – until they walked around for a few weeks and “lost some serious pounds,” he joked.

An artist's impression  shows the surface of Kepler 452b. In the scenario depicted here, the planet is just entering a runaway greenhouse phase of its climate history. Kepler 452b could be giving us a preview of what Earth will undergo more than a billion years from now as the sun ages and grows brighter. Credit: Danielle Futselaar / SETI Institute/
An artist’s impression shows the surface of Kepler 452b. In the scenario depicted here, the planet is just entering a runaway greenhouse phase of its climate history. Kepler 452b could be giving us a preview of what Earth will undergo more than a billion years from now as the sun ages and grows brighter. Credit: Danielle Futselaar / SETI Institute

The planet is about 5 percent farther from its parent star than Earth is from our sun, with a year that lasts 385 days. Its sun is 10 percent bigger and 20 percent brighter than our sun, with the same classification as a G2 dwarf. But Kepler-452b’s star is older than our 4.6 billion-year-old home star – which suggests the cosmic conditions for life could be long-lasting.

“It’s simply awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star, which is longer than the age of the Earth,” Jenkins said. Models for planetary development suggest that Kepler-452b would experience an increasing warming trend and perhaps a runaway greenhouse effect as it aged, he said.

Kepler-452b’s advantages trump the mission’s earlier planetary discoveries. One involved a rocky planet, just a little bigger than Earth, that was found in its parent star’s habitable zone – that is, the kind of orbit where liquid water could exist. But that star, known as Kepler-186, is a shrunken red dwarf rather than a close analog to the sun.

Kepler research scientist Jeff Coughlin said it’s not clear how hospitable a planet circling a red dwarf might be. A rocky planet in the right orbit around a sunlike star is a surer bet. “We’re here on Earth, we know there’s life here,” he said.

Scientists said Kepler-452b is on the target list for the SETI Institute’s search for radio signals from extraterrestrial civilizations, using the Allen Telescope Array in California – but no alien detection has been reported. “So far, the 452b-ians have been coy,” Seth Shostak, the institute’s senior astronomer and director of the Center for SETI Research, told Universe Today in an email.

Planetary system comparison
This size and scale of the Kepler-452 system compared alongside our own solar system, plus another planetary system with a habitable-zone planet known as Kepler-186f. The Kepler-186 system has a faint red dwarf star.

John Grunsfeld, NASA’s associate administrator for science, characterized the newly announced planet as the “closest twin” to Earth discovered so far. However, he said further analysis of the Kepler data may turn up even closer relatives.

Launched in 2009, Kepler detects alien worlds by looking for the faint dimming of a star as a planet crosses its disk. The SUV-sized telescope has spotted more than 4,600 planet candidates.

So far, about 1,000 of those have been confirmed as planets using other methods, ranging from detecting their parent stars’ Doppler shifts to carefully measuring the time intervals between the passages of planets. For Kepler-452b, scientists used ground-based observations and computer models to estimate the mass and confirm the detection to a level of 99.76 percent, Jenkins said.

The findings were due to be published online Thursday by the Astrophysical Journal, Jenkins said. In addition to Kepler-452b, another 521 planet candidates have been added to the mission’s checklist – including 12 candidates that appear to be one to two times as wide as Earth and orbit in their parent stars’ habitable zones. Nine of the stars are similar to our own sun in size and temperature, NASA said in a news release.

There’s sure to be more to come. In 2013, Kepler was crippled by failures of its fine-pointing navigation system, but it returned to its planet-hunting mission last year, thanks to some clever tweaking that makes use of the solar wind as an extra stabilizer. “It’s kind of the best-worst thing that ever happened to Kepler,” Jenkins said.

What’s Up With Ceres’ Mysterious Bright Spots? Reply Hazy, Ask Again Later

Ceres' spots

The crater that contains those puzzlingly bright spots on Ceres may harbor an equally puzzling haze. Or not. The hints of haze on the dwarf planet, seen in some of the images coming from NASA’s Dawn spacecraft, add another intriguing twist to Ceres’ mysteries.

The hubbub over haze arose this week during the Exploration Science Forum at NASA’s Ames Research Center in California. For months, Dawn’s scientists have been observing – and trying to make sense out of – unusually reflective spots within Ceres’ craters that show up when the asteroid turns into the sunlight. The team has speculated that they could be frozen pools of water ice, or patches of light-colored, salt-rich material.

The brightest spots are known collectively as Spot 5, and sit inside Occator Crater on Ceres. Dawn’s principal investigator, Chris Russell of the University of California at Los Angeles, told the forum that some type of haze could be seen inside the crater at certain times of Ceres’ day, according to reports from Nature and the Planetary Society. Nature quoted Russell as saying the bright spots “could be providing some atmosphere in this particular region of Ceres.”

Last year, scientists with the European Space Agency’s Herschel mission reported detecting signs of water vapor rising from Ceres’ surface, and it would be tempting to suggest that the water vapor is emanating from bright icy spots and creating the haze. That would strengthen Ceres’ status as the only asteroid with a significant atmosphere and a subsurface reservoir of water, and stoke speculation about life on Ceres.

However, Russell told Universe Today that it’s way too early to give in to temptation.

“I was speaking from less than a handful of images, and the interpretation of the images is disputed by some team members,” Russell said in an email. “I would like the debate to go on internally before we make a pronouncement one way or the other. I of course have my personal opinion, but I am not always right.”

Russell said the ice-vs.-salt debate is continuing. “I originally was an advocate of ice, because of how bright the spots seemed to be,” he said. However, the bright material’s albedo, or reflectivity factor, is about 50 percent – which is less than Russell originally thought. “This could be salt and is unlikely to be ice. I think the team opinion is now more in line with salt,” he said.

Either way, Russell doesn’t see any way for the spots to form without internal activity on Ceres. “Thus, the very existence of the spots tells us that there is some active process going on,” he told Universe Today.

Will we ever know if the haze is for real? Or what the spots are made of? As the Magic 8-Ball might say, “Ask again later.” The Dawn spacecraft recently recovered from a mechanical glitch and is gradually descending to a closer mapping orbit, around an altitude of 900 miles (1,500 kilometers). That will provide a much better look at Occator Crater and what lies within.

“Eventually I am expecting the spectral data will unambiguously tell us what has happened to the surface,” Russell said, “but it is a little too soon to be sure.”