Kepler’s follow-up observers confirm new discoveries
More than 2,300 exoplanet candidate discoveries have made it the most prolific planet hunter in history. But even NASA’s Kepler mission needs a little help from its friends.
An artist’s illustration of an exoplanet system. Credit: Haven Giguere/YaleEnter the Kepler follow-up observation program, a consortium of astronomers dedicated to getting in-depth with the mission’s findings and verifying them to an extremely high degree of confidence.
A single Kepler observation alone is often not enough to prove that the telescope has found an exoplanet, said Nick Gautier, the mission’s deputy project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., who coordinated and continues to help run Kepler’s robust follow-up program.
Kepler finds exoplanets by watching for worlds that move directly between the telescope and their host stars. As they do this, they block a tiny fraction of the star’s light, an event astronomers call a “transit.”
Astronomers using the Canada-France-Hawaii and W. M. Keck Observatory telescopes on the summit of Mauna Kea, Hawaii have been amazed to find a group of dwarf galaxies moving in unison in the vicinity of the Andromeda Galaxy. The structure of these small galaxies lies in a plane, analogous to the planets of the Solar System. Unexpectedly, they orbit the much larger Andromeda galaxy en masse, presenting a serious challenge to our ideas for the formation and evolution of all galaxies.
The findings are being reported on the cover the upcoming issue of the journal, Nature.
While Persian astronomers were the first to catalogue the Andromeda galaxy, only in the last five years that we have studied in exquisite detail the most distant suburbs of the Andromeda galaxy via the Pan-Andromeda Archaeological Survey (PAndAS), undertaken with the Canada-France-Hawaii Telescope and measured with the Keck Observatory, providing our first panoramic view of our closest large companion in the cosmos.
The study culminates many years of effort by an international team of scientists who have discovered a large number of the satellite galaxies, developed new techniques to measure their distances, and have used the Keck Observatory with colleagues to measure their radial velocities, or Doppler shifts (the speed of the galaxy relative to the Sun). While earlier work had hinted at the existence of this structure, the new study has demonstrated its existence to a high level of statistical confidence (99.998%).
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.
A group of astronomers from the University of Hawaii at Manoa, the U.S. Mainland, Canada, and Europe recently used the twin telescopes of the W. M. Keck Observatory on Mauna Kea, Hawaii, to conduct a census of the brightest, but until now unseen, galaxies in the distant Universe, bringing astronomers one step closer to understanding how galaxies form and evolve.
A 3D projection of almost 300 galaxies in the census in the same part of the sky.These galaxies glow so brightly at infrared wavelengths that they would outshine our own Milky Way by hundreds, maybe thousands, of times. They are forming stars so quickly that between 100 and 500 new stars are born in each galaxy every year, and have been coined “starbursts” by astronomers.
While it’s not clear what gives these galaxies their intense luminosity, it could be the result of a collision between two spiral-type galaxies, similar to the Milky Way and Andromeda Galaxies. Or they could be in a particularly gas-rich region of space, where galaxies form stars quickly due to constant bombardment from gas and dust.
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.
Two ‘super-luminous’ supernovae — stellar explosions 10–100 times brighter than other supernova types — have been detected in the distant Universe, using the W.M. Keck Observatory on the top of Mauna Kea in Hawaii. The discovery, reported online in Nature this week, sets a record for the most distant supernova yet detected, and offers the rare possibility of observing the explosions of the first stars to form after the Big Bang.
Simulation of a galaxy hosting a super-luminous supernova and its chaotic environment in the early Universe. Credit: Adrian Malec and Marie Martig (Swinburne University)“The type of supernovae we’ve found are extremely rare,” said Jeff Cooke, astrophysicist at Swinburne University of Technology, whose team made the discovery. “In fact, only one has been discovered prior to our work. This particular type of supernova results from the death of a very massive star (about 100 – 250 times the mass of our Sun) and explodes in a completely different way compared to other supernovae. Discovering and studying these events provides us with observational examples to better understand them and the chemicals they eject into the Universe when they die.”
Super-luminous supernovae were discovered only a few years ago, and are rare in the nearby Universe. Their origins are not well understood, but a small subset of them is thought to occur when extremely massive stars undergo a nuclear explosion triggered by the conversion of photons into electron–positron pairs. Such events are expected to have occurred more frequently in the early Universe (at high redshift), when massive stars were more common. This, and the extreme brightness of these events, encouraged Cooke and colleagues to search for super-luminous supernovae at redshifts, z, greater than 2, when the Universe was less than one-quarter of its present age.
New research using the world’s largest telescope at the Keck Observatory in Hawaii has revealed two distinct populations of star clusters surrounding galaxies that have radically different chemical compositions.
M22 or NGC6656 in Sagittarius, a classic globular clusterAn international team, led by Swinburne astronomers Christopher Usher and Professor Duncan Forbes, has measured the chemical composition of more than 900 star clusters in a dozen galaxies.
“This is ten times the number of star clusters previously examined, allowing us to confirm the existence of two chemically-distinct star clusters,” Mr Usher said.
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.
A comprehensive study of hundreds of galaxies observed by the Keck telescopes in Hawaii and NASA’s Hubble Space Telescope has revealed an unexpected pattern of change that extends back 8 billion years, or more than half the age of the universe.
“Astronomers thought disk galaxies in the nearby universe had settled into their present form by about 8 billion years ago, with little additional development since,” said Susan Kassin, an astronomer at NASA’s Goddard Space Flight Center in Greenbelt, Md., and the study’s lead researcher. “The trend we’ve observed instead shows the opposite, that galaxies were steadily changing over this time period.”
Today, star-forming galaxies take the form of orderly disk-shaped systems, such as the Andromeda Galaxy or the Milky Way, where rotation dominates over other internal motions. The most distant blue galaxies in the study tend to be very different, exhibiting disorganized motions in multiple directions. There is a steady shift toward greater organization to the present time as the disorganized motions dissipate and rotation speeds increase. These galaxies are gradually settling into well-behaved disks.
This plot shows the fractions of settled disk galaxies in four time spans, each about 3 billion years long. Credit: Credit: NASA’s Goddard Space Flight Center
Blue galaxies—their color indicates stars are forming within them—show less disorganized motions and ever-faster rotation speeds the closer they are observed to the present. This trend holds true for galaxies of all masses, but the most massive systems always show the highest level of organization.
Researchers say the distant blue galaxies they studied are gradually transforming into rotating disk galaxies like our own Milky Way.
“Previous studies removed galaxies that did not look like the well-ordered rotating disks now common in the universe today,” said co-author Benjamin Weiner, an astronomer at the University of Arizona in Tucson. “By neglecting them, these studies examined only those rare galaxies in the distant universe that are well-behaved and concluded that galaxies didn’t change.”
Watching active volcanic eruptions should be done from a safe distance, and a group of California researchers has figured out how to do it from, ironically, Mauna Kea – one of Earth’s tallest volcanoes – using the W. M. Keck Observatory. Employing an ingenious combination of telescopic surveys and archival data, they have gathered nearly 40 distinct snapshots of effusive (slow) volcanic eruptions and high temperature outbursts on Jupiter’s tiny moon, Io, showing details as small as 100 km (60 miles) on the moon’s surface.
While space-based telescopes were once required for viewing surface details on Io – similar in size to our Moon, but more than 1,600 times distant – adaptive optics (AO), pioneered at Keck, allows teams like that led by Franck Marchis, a researcher at the Carl Sagan Center of the SETI Institute, to collect fascinating data on the wild show from Earth. Marchis presented results from ground-based telescopic monitoring of Io’s volcanic activity over the past decade this week, at the 2012 Division of Planetary Sciences Meeting of the American Astronomical Society.
Erupting volcanoes on Io cannot be seen well from beneath the Earth’s atmosphere using classical astronomical techniques. Io is a relatively small satellite with a 3,600 km diameter, more than 630 million kilometers away. In 1979, Voyager 1 visited the Jovian system, revealing Io’s dynamic volcanic activity from the first close-up pictures of its surface, capturing bizarre volcanic terrains, active plumes and hot spots. The Galileo spacecraft remained in orbit in the Jovian system from 1995 to 2003 and observed more than 160 active volcanoes and a broad range of eruption styles. Several outstanding questions remained in the post-Galileo era, and the origin and long-term evolution of Io’s volcanic activity is still not fully understood.
Quiescent activity of Io observed in 2010 and 2011 showing several quasi-permanent eruptions at 3.8 microns [bottom] and the absence of bright, hotter outbursts at 2.1 microns [top]. Credit: Franck Marchis, SETI Institute
In the meantime, astronomers designed instruments to break the “seeing barrier” and improve the image quality of ground-based telescopes. The blurring (“seeing”) introduced by the constant motion of the Earth’s atmosphere can be measured and corrected in real time using adaptive optics (AO), providing an image with a resolution close to the theoretical “diffraction limit” of the telescope. The W. M. Keck Observatory has used adaptive optics since 1999.
“Since our first observation of Io in 2001 using the Keck II 10-meter telescope and its AO system from Mauna Kea in Hawaii, our group became very excited about the technology. We also began using AO at the Very Large Telescope in Chile, and at the Gemini North telescope in Hawaii. The technology has improved over the years, and the image quality and usefulness of these AO systems have made them part of the essential instrument suite for large telescopes,” said Marchis.