Exoplanet Studies
Kepler Telescope Bids ‘Goodnight’ with Final Commands
On the evening of Thursday, Nov. 15, NASA’s Kepler space telescope received its final set of commands to disconnect communications with Earth. The “goodnight” commands finalize the spacecraft’s transition into retirement, which began on Oct. 30 with NASA’s announcement that Kepler had run out of fuel and could no longer conduct science.
Coincidentally, Kepler’s “goodnight” falls on the same date as the 388-year anniversary of the death of its namesake, German astronomer Johannes Kepler, who discovered the laws of planetary motion and passed away on Nov. 15, 1630.
NASA’s Webb Observatory Requires More Time for Testing and Evaluation; New Launch Window Under Review
NASA Release by Jen Rae Wang / Steve Cole
Headquarters, Washington’
NASA’s James Webb Space Telescope currently is undergoing final integration and test phases that will require more time to ensure a successful mission. After an independent assessment of remaining tasks for the highly complex space observatory, Webb’s previously revised 2019 launch window now is targeted for approximately May 2020.
“Webb is the highest priority project for the agency’s Science Mission Directorate, and the largest international space science project in U.S. history. All the observatory’s flight hardware is now complete, however, the issues brought to light with the spacecraft element are prompting us to take the necessary steps to refocus our efforts on the completion of this ambitious and complex observatory,” said acting NASA Administrator Robert Lightfoot.
Newly Discovered Exoplanet May be Best Candidate in Search for Signs of Life
Jason Dittmann
Harvard-Smithsonian Center for Astrophysics
Transiting rocky super-Earth found in habitable zone of quiet red dwarf star
An exoplanet orbiting a red dwarf star 40 light-years from Earth may be the new holder of the title “best place to look for signs of life beyond the Solar System”. Using ESO’s HARPS instrument at La Silla, and other telescopes around the world, an international team of astronomers discovered a “super-Earth” orbiting in the habitable zone around the faint star LHS 1140. This world is a little larger and much more massive than the Earth and has likely retained most of its atmosphere. This, along with the fact that it passes in front of its parent stars as it orbits, makes it one of the most exciting future targets for atmospheric studies. The results will appear in the 20 April 2017 issue of the journal Nature.
NASA News Briefing: Discoveries About Oceans Beyond Earth
NASA/JPL NEWS RELEASE | APRIL 10, 2017
NASA will discuss new results about ocean worlds in our solar system from the agency’s Cassini spacecraft and the Hubble Space Telescope during a news briefing 11 a.m. PDT (2 p.m. EDT) on Thursday, April 13. The event, to be held at NASA Headquarters in Washington, will include remote participation from experts across the country.
The briefing will be broadcast live on NASA Television and the agency’s website.
These new discoveries will help inform future ocean world exploration — including NASA’s upcoming Europa Clipper mission planned for launch in the 2020s — and the broader search for life beyond Earth.
Ultracool Dwarf and the Seven Planets
Dr. Paola Rebusco
MIT – Experimental Study Group
ESON USA
eson-usa@eso.org
Astronomers using the TRAPPIST–South telescope at ESO’s La Silla Observatory, the Very Large Telescope (VLT) at Paranal and the NASA Spitzer Space Telescope, as well as other telescopes around the world [1], have now confirmed the existence of at least seven small planets orbiting the cool red dwarf star TRAPPIST-1 [2]. All the planets, labelled TRAPPIST-1b, c, d, e, f, g and h in order of increasing distance from their parent star, have sizes similar to Earth [3].
New Planet Imager Delivers First Science
Written by Whitney Clavin
Jet Propulsion Laboratory, Pasadena, California
January 30, 2017
A new device on the W.M. Keck Observatory in Hawaii has delivered its first images, showing a ring of planet-forming dust around a star, and separately, a cool, star-like body, called a brown dwarf, lying near its companion star.
The device, called a vortex coronagraph, was recently installed inside NIRC2 (Near Infrared Camera 2), the workhorse infrared imaging camera at Keck. It has the potential to image planetary systems and brown dwarfs closer to their host stars than any other instrument in the world.
NASA, Citizen Scientists Discover Potential New Hunting Ground for Exoplanets
Via a NASA-led citizen science project, eight people with no formal training in astrophysics helped discover what could be a fruitful new place to search for planets outside our solar system – a large disk of gas and dust encircling a star known as a circumstellar disk.
A paper, published in The Astrophysical Journal Letters and coauthored by eight citizen scientists involved in the discovery, describes a newly identified red dwarf star, AWI0005x3s, and its warm circumstellar disk, the kind associated with young planetary systems. Most of the exoplanets, which are planets outside our solar system, that have been imaged to date dwell in disks similar to the one around AWI0005x3s.
The disk and its star are located in what is dubbed the Carina association – a large, loose grouping of similar stars in the Carina Nebula approximately 212 light years from our sun. Its relative proximity to Earth will make it easier to conduct follow-on studies.
Light Echoes Gives Clues To Protoplanetary Disk
Imagine you want to measure the size of a room, but it’s completely dark. If you shout, you can tell if the space you’re in is relatively big or small, depending on how long it takes to hear the echo after it bounces off the wall.
Astronomers use this principle to study objects so distant they can’t be seen as more than points. In particular, researchers are interested in calculating how far young stars are from the inner edge of their surrounding protoplanetary disks. These disks of gas and dust are sites where planets form over the course of millions of years.
ESO Discovers Earth-Size Planet in Habitable Zone of Nearest Star
A newly discovered, roughly Earth-sized planet orbiting our nearest neighboring star might be habitable, according to a team of astronomers using the European Southern Observatory’s 3.6-meter telescope at La Silla, Chile, along with other telescopes around the world.
The exoplanet is at a distance from its star that allows temperatures mild enough for liquid water to pool on its surface.
“NASA congratulates ESO on the discovery of this intriguing planet that has captured the hopes and the imagination of the world,” says Paul Hertz, Astrophysics Division Director at NASA Headquarters, Washington. “We look forward to learning more about the planet, whether it holds ingredients that could make it suitable for life.”
The new planet circles Proxima Centauri, the smallest member of a triple star system known to science fiction fans everywhere as Alpha Centauri. Just over 4 light-years away, Proxima is the closest star to Earth, besides our own sun.
“This is really a game-changer in our field,” said Olivier Guyon, a planet-hunting affiliate at NASA’s Jet Propulsion Laboratory, Pasadena, California, and associate professor at the University of Arizona, Tucson. “The closest star to us has a possible rocky planet in the habitable zone. That’s a huge deal. It also boosts the already existing, mounting body of evidence that such planets are near, and that several of them are probably sitting quite close to us. This is extremely exciting.”
The science team that made the discovery, led by Guillem Anglada-Escudé of Queen Mary University of London, will publish its findings Aug. 25 in the Journal Nature in a 33-page paper titled “A terrestrial planet candidate in a temperate orbit around Proxima Centauri. The team traced subtle wobbles in the star revealing, the presence of a star-tugging planet.
They determined that the new planet, dubbed Proxima b, is at least 1.3 times the mass of Earth. It orbits its star far more closely than Mercury orbits our sun, taking only 11 days to complete a single orbit — a “year” on Proxima b.
Long list of unknowns
The stunning announcement comes with plenty of caveats. While the new planet lies within its star’s “habitable zone” — a distance at which temperatures are right for liquid water — scientists do not yet know if the planet has an atmosphere.
It also orbits a red-dwarf star, far smaller and cooler than our sun. The planet likely presents only one face to its star, as the moon does to Earth, instead of rotating through our familiar days and nights. And Proxima b could be subject to potentially life-extinguishing stellar flares.
“That’s the worry in terms of habitability,” said Scott Gaudi, an astronomy professor at Ohio State University, Columbus, and JPL affiliate credited with numerous exoplanet discoveries. “This thing is being bombarded by a fair amount of high-energy radiation. It’s not obvious if it’s going to have a magnetic field strong enough to prevent its whole atmosphere from getting blown away. But those are really hard calculations, and I certainly wouldn’t put my money either way on that.”
Despite the unknowns, the discovery was hailed by NASA exoplanet hunters as a major milestone on the road to finding other possible life-bearing worlds within our stellar neighborhood.
“It definitely gives us something to be excited about,” said Sara Seager, a planetary science and physics professor at the Massachusetts Institute of Technology, Cambridge, and an exoplanet-hunting pioneer. “I think it will definitely motivate people to get moving.”
‘Not completely unexpected’
Statistical surveys of exoplanets — planets orbiting other stars — by NASA’s Kepler space telescope have revealed a large proportion of small planets around small stars, she said.
The Kepler data suggest we should expect at least one potentially habitable, Earth-size planet orbiting M-type stars, like Proxima, within 10 light-years of our solar system.
So the latest discovery was “not completely unexpected. We’re more lucky than surprised,” Seager said. But it “helps buoy our confidence that planets are everywhere.”
It’s especially encouraging for upcoming space telescopes, which can contribute to the study of the new planet. The James Webb Space Telescope, launching in 2018, may be able to follow-up on this planet with spectroscopy to determine the contents of its atmosphere. NASA’s Transiting Exoplanet Survey Satellite (TESS) will find similar planets in the habitable zone in the stellar backyard of our solar system in 2018.
One of TESS’s goals is to find planets orbiting nearby M-dwarf stars like Proxima Centauri.
“It’s great news just to know that M-dwarf planets could be as common as we think they are,” Seager said.
Another possible inspiration Proxima b could reignite: the admittedly far-off goal of sending a probe to another solar system.
Bill Borucki, an exoplanet pioneer, said the new discovery might inspire more interstellar research, especially if Proxima b proves to have an atmosphere.
Coming generations of space and ground-based telescopes, including large ground telescopes now under construction, could yield more information about the planet, perhaps inspiring ideas on how to pay it a visit.
“It may be that the first time we get really good information is from the newer telescopes that may be coming online in a decade or two,” said Borucki, now retired, a former principal investigator for Kepler, which has discovered the bulk of the more than 3,300 exoplanets found so far.
“Maybe people will talk about sending a probe to that star system,” Borucki said. “I think it does provide some inspiration for an interstellar mission, because now we know there is a planet in the habitable zone, probably around the mass of Earth, around the closest star. I think it does inspire a future effort to go there and check it out.”
To read the ESO press release, visit: http://www.eso.org/public/news/eso1629/?lang
To learn more about NASA’s Exoplanet Program, visit: http://exoplanets.nasa.gov
Cloudy Days on Exoplanets May Hide Atmospheric Water
Water is a hot topic in the study of exoplanets, including “hot Jupiters,” whose masses are similar to that of Jupiter, but which are much closer to their parent star than Jupiter is to the sun. They can reach a scorching 2,000 degrees Fahrenheit (1,100 degrees Celsius), meaning any water they host would take the form of water vapor.
Astronomers have found many hot Jupiters with water in their atmospheres, but others appear to have none. Scientists at NASA’s Jet Propulsion Laboratory, Pasadena, California, wanted to find out what the atmospheres of these giant worlds have in common.
Researchers focused on a collection of hot Jupiters studied by NASA’s Hubble Space Telescope. They found that the atmospheres of about half of the planets were blocked by clouds or haze.
“The motivation of our study was to see what these planets would be like if they were grouped together, and to see whether they share any atmospheric properties,” said Aishwarya Iyer, a JPL intern and master’s degree candidate at California State University, Northridge, who led the study.
The new study, published in the June 1 issue of the Astrophysical Journal, suggests that clouds or haze layers could be preventing a substantial amount of atmospheric water from being detected by space telescopes. The clouds themselves are likely not made of water, as the planets in this sample are too hot for water-based clouds.
“Clouds or haze seem to be on almost every planet we studied,” Iyer said. “You have to be careful to take clouds or haze into account, or else you could underestimate the amount of water in an exoplanet’s atmosphere by a factor of two.”
In the study, scientists looked at a set of 19 hot Jupiters previously observed by Hubble. The telescope’s Wide Field Camera 3 had detected water vapor in the atmospheres of 10 of these planets, and no water on the other nine. But that information was spread across more than a dozen studies. The methods of analyzing and interpretation varied because the studies were conducted separately. There had not been one overarching analysis of all these planets.
To compare the planets and look for patterns, the JPL team had to standardize the data: Researchers combined the datasets for all 19 hot Jupiters to create an average overall light spectrum for the group of planets. They then compared these data to models of clear, cloud-free atmospheres and those with various cloud thicknesses.
The scientists determined that, for almost every planet they studied, haze or clouds were blocking half of the atmosphere, on average.
“In some of these planets, you can see water peeking its head up above the clouds or haze, and there could still be more water below,” Iyer said.
Scientists do not yet know the nature of these clouds or hazes, including what they are they made of.
“Clouds or haze being on almost all these planets is pretty surprising,” said Robert Zellem, a postdoctoral fellow at JPL and co-author of the study.
The implications of this result agree with findings published in the Dec. 14, 2015, issue of the journal Nature. The Nature study used data from NASA’s Hubble and Spitzer Space Telescopes to suggest that clouds or haze could be hiding undetected water in hot Jupiters. This new study uses exoplanet data from a single instrument on Hubble to uniformly characterize a larger group of hot Jupiters, and is the first to quantify how much of the atmosphere would be shielded as a result of clouds or haze.
The new research could have implications for follow-up studies with future space observatories, such as NASA’s James Webb Space Telescope. Exoplanets with thick cloud covers blocking the detection of water and other substances may be less desirable targets for more extensive study.
These results are also important for figuring out how planets form, scientists say.
“Did these planets form in their current positions or migrate toward their host stars from farther out? Understanding the abundances of molecules such as water helps us answer those questions,” Zellem said.
“This paper is an exciting step forward for the study of exoplanets and comparing their properties,” said Mark Swain, study co-author and group supervisor for the exoplanet discovery and science group at JPL.
Michael Line of the University of California, Santa Cruz, also contributed to the study. Other co-authors from JPL included Gael Roudier, Graca Rocha and John Livingston.
For more information about the Hubble Space Telescope, visit: www.nasa.gov/hubble.
