An international team of astronomers using the W. M. Keck Observatory and other telescopes, has discovered that Tau Ceti, one of the closest and most Sun-like stars, may host five planets – with one in the elusive ‘Goldilocks Zone’.
Artists impression of the Tau Ceti System. Credit: J. Pinfield for the RoPACS networkAt a distance of twelve light years and visible with the naked eye in the December evening sky, Tau Ceti is the closest single star that has the same spectral classification as our Sun. Its five planets are estimated to have masses between two and six times the mass of the Earth – making it the lowest-mass planetary system yet detected. One of the planets lies in the star’s habitable zone – the so-called Goldilocks Zone with it’s ‘just right’ temperatures for supporting liquid water – and has a mass around five times that of Earth, making it the smallest planet found to be orbiting in the habitable zone of any Sun-like star.
The international team of astronomers, from the UK, Chile, the USA, and Australia, combined more than 6,000 observations from three different instruments, including HIRES on the Keck I telescope. Using new techniques, the team has found a method to detect signals half the size previously thought possible. This greatly improves the sensitivity of searches for small planets and suggests that Tau Ceti is not a lone star but has a planetary system.
Lowell astronomer Evgenya Shkolnik and her collaborators have published a set of directions for searching out exoplanets, using W. M. Keck Observatory spectroscopy.
Their paper, recently published in The Astrophysical Journal, examined new and existing data from stars and brown dwarfs that are less than 300 million years old, as determined from strong X-ray emission readings. In all, the authors identified 144 young targets for exoplanet searches, with 20 very strong candidates, according to Dr. Shkolnik. This candidate list is being searched for planets with Gemini’s NICI Planet-Finding Campaign and the Planets Around Low-Mass Stars survey, led by astronomer Michael Liu and graduate student Brendan Bowler, respectively, both at the Institute for Astronomy, University of Hawai‘i.
A joint effort of citizen scientists and professional astronomers at W.M. Keck Observatory in Hawaii has led to the first reported case of a Tatooine-like planet orbiting twin suns that in turn is orbited by a second distant pair of stars.
Aided by volunteers using the Planethunters.org website, a Yale-led international team of astronomers using Keck’s 10-meter telescope identified and confirmed discovery of the phenomenon, called a circumbinary planet in a four-star system.
Only six planets are known to orbit two stars, according to researchers, and none of these are orbited by distant stellar companions.
“Circumbinary planets are the extremes of planet formation,” said Meg Schwamb of Yale, lead author of a paper about the system presented Oct. 15 at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Reno, Nevada. “The discovery of these systems is forcing us to go back to the drawing board to understand how such planets can assemble and evolve in these dynamically challenging environments.”
An artist’s illustration of PH1, a planet discovered by volunteers from the Planet Hunters citizen science project. PH1, shown in the foreground, is a circumbinary planet and orbits two suns. Credit: Haven Giguere/Yale
Dubbed PH1, the planet was first identified by citizen scientists participating in Planet Hunters, a Yale-led program that enlists the public to review astronomical data from NASA’s Kepler spacecraft for signs of planets. It is the project’s first confirmed planet.
The volunteers, Kian Jek of San Francisco and Robert Gagliano of Cottonwood, Arizona, spotted faint dips in light caused by the planet as it passed in front of its parent stars, a common method of finding extrasolar planets. Schwamb, a Yale postdoctoral researcher, led the team of professional astronomers that confirmed the discovery and characterized the planet, following observations from the Keck telescopes on Mauna Kea, Hawaii. PH1 is a gas giant with a radius about 6.2 times that of Earth, making it a bit bigger than Neptune.
“Planet Hunters is a symbiotic project, pairing the discovery power of the people with follow-up by a team of astronomers,” said Debra Fischer, a professor of astronomy at Yale and planet expert who helped launch Planet Hunters in 2010. “This unique system might have been entirely missed if not for the sharp eyes of the public.”
PH1 orbits outside the 20-day orbit of a pair of eclipsing stars that are 1.5 and 0.41 times the mass of the Sun. It revolves around its host stars roughly every 138 days. Beyond the planet’s orbit at about 1000 AU (roughly 1000 times the distance between Earth and the Sun) is a second pair of stars orbiting the planetary system.
An international team of scientists has discovered a potentially habitable super-Earth orbiting a nearby star. With an orbital period of about 28 days and a minimum mass 4.5 times that of the Earth, the planet orbits within the star’s “habitable zone,” where temperatures are neither too hot nor too cold for liquid water to exist on the planet’s surface. The researchers found evidence of at least one and possibly two or three additional planets orbiting the star, which is about 22 light years from Earth.
The researchers used public data from the European Southern Observatory and analyzed it with a novel data-analysis method. They also incorporated new measurements from the W. M. Keck Observatory’s High Resolution Echelle Spectrograph (HiRES) and the new Carnegie Planet Finder Spectrograph at the Magellan II Telescope. Their planet-finding technique involved measuring the small wobbles in a star’s motion caused by the gravitational tug of a planet.
The team includes UC Santa Cruz astronomers Steven Vogt and Eugenio Rivera and was led by Guillem Anglada-Escudé and Paul Butler of the Carnegie Institution for Science. Their work will be published by Astrophysical Journal Letters, and the manuscript will be posted online at arxiv.org/archive/astro-ph.
The host star is a member of a triple-star system and has a different makeup than our sun, with a much lower abundance of elements heavier than helium, such as iron, carbon, and silicon. This discovery indicates that potentially habitable planets can occur in a greater variety of environments than previously believed.
For years the search for exoplanets has largely been like Gulliver’s visit to Brobdingnag: colossal systems of giant gas planets orbiting mammoth stars. But astronomers have finally landed on the shores of Lilliput. They have found a tiny star with three puny planets, each smaller than Earth, zooming around it.
The three small exoplanets orbit a star called KOI-961. Their radii are calculated to be 78, 73 and 57 percent that of Earth. The sizes of the planets were worked out by Kepler Telescope observations that measured the dimming of the star KOI-961 as each planet passes in front of it. This plus crucial information about the star from Keck and Palomar telescopes enabled researchers to determine the sizes of the planets.
Although the masses of the three planets are unknown, they are suspected of being rocky, like Earth, Venus, Mars and Mercury. But they orbit too close to their star to be in the habitable zone where liquid water could exist. The three planets take less than two days to orbit around KOI-961, which is a red dwarf with a diameter one-sixth that of our sun, making it just 70 percent bigger than Jupiter.
“This is the tiniest solar system found so far,” said John Johnson, the principal investigator of the research from NASA’s Exoplanet Science Institute at the California Institute of Technology in Pasadena. “It’s actually more similar to Jupiter and its moons in scale than any other planetary system. The discovery is further proof of the diversity of planetary systems in our galaxy.”
We do like it when Keck Observatory is featured in the local papers. We are proud of the ‘scopes and take notice when we get some good press. The Star-Advertiser is the major daily paper for Honolulu and much of the state. I have even had some of my photographs published in the paper. Another article about Keck appeared today, but this time they simply display their ignorance of basic science.
The headline quickly had my attention. Exoplanet discoveries are coming fast with the Kepler Spacecraft / Keck Observatory team confirming alien worlds at a breakneck pace. It was the “outside the Milky Way” part that had my attention. I had no idea our current technology was capable of that! KOI-961 is a red-dwarf, a small, fairly dim class of star. It is difficult to even detect these stars at great distances, much less get the data needed to confirm orbiting planets. Something wrong here.
I double checked other sources… KOI-961 is actually fairly close to us in galactic terms, a mere 130 light years away. Given that the Milky Way Galaxy is well over 100,000 light years across, it puts KOI-961 well inside our galaxy. The article is actually reasonable, it appears to have simply taken the information from a press release, hard to screw up a cut and paste job. The headline however is where they stumbled hard.
Someone at the Star-Advertiser needs to take a basic astronomy course. Or maybe, simply check Wikipedia!
Update… They have fixed it. I forwarded the link to Larry O’Hanlon, the Keck PIO, whom I work with regularly. He called the S-A and apparently pointed out the issue. I would have loved to listen in on that conversation. The headline and text are edited now on the S-A website, but I kept a screenshot…
For nearly a decade, Cal-Berkeley astronomer Geoff Marcy and his colleagues have been using the W. M. Keck telescopes to discover giant planets orbiting distant stars. Now, with the successful launch of NASA’s Kepler mission, they will be using Keck I’s ten-meter astronomical eye to discover distant Earths. Kepler will pick out Earth-like candidates. Keck will then zero in on them and determine, with certainty, if they are at all similar to our home planet.
“Keck and NASA have a long-standing partnership to push astronomy research to its fullest potential. This Keck-Kepler collaboration gives that partnership a compelling new scientific focus,” said Taft Armandroff, the Director of Keck Observatory headquartered in Kamuela, HI.
Artist’s rendition of the Kepler Spacecraft in orbit around the Sun peering at a distant solar system, press release image from the NASA Kepler websiteKepler was launched from NASA’s Kennedy Space Center last Friday. Aboard the spacecraft is an 84-megapixel camera that will focus on a single region of the sky and snap repeated images of 100,000 stars looking for those that dim periodically. By studying the stars’ episodic decreases in starlight, astronomers will be able to determine the diameter of the object that passes in front of the star, blocks its light and causes the dimming.
“Kepler does not tell astronomers with certainty if the object taking a bite out of the starlight is a planet or another star. That is where Keck plays a crucial role to the Kepler mission,” said Marcy, a frequent Keck user and Kepler mission co-investigator. He, along with a large international planet-hunting team, has discovered nearly half of the 300-plus known planets outside the Solar System.
