The field of exoplanet research continues to grow by leaps and bounds. Thanks to missions like the Kepler Space Telescope, over four-thousand planets have been discovered beyond our Solar System, with more being confirmed all the time. Thanks to these discoveries and all that we’ve learned from them, the focus has begun to transition from the process of discovery to characterization.
For instance, a group of astronomers was able to image the surface of a planet orbiting a red dwarf star for the first time. Using data from the NASA Spitzer Space Telescope, the team was able to provide a rare glimpse at the conditions on the planet’s surface. And while those conditions were rather inhospitable – akin to something like Hades, but with less air to breathe – this represents a major breakthrough in the study of exoplanets.
The super-Earth 55 Cancri e (aka. Janssen) is somewhat famous, as exoplanet go. Originally discovered in 2004, this world was one of the few whose discovery predated the Kepler mission. By 2016, it was also the first exoplanet to have its atmosphere successfully characterized. Over the years, several studies have been conducted on this planet that revealed some rather interesting things about its composition and structure.
For example, scientists believed at one time that 55 Cancri e was a “diamond planet“, whereas more recent work based on data from the Spitzer Space Telescope concluded that its surface was covered in lakes of hot lava. However, a new study conducted by scientists from NASA’s Jet Propulsion Laboratory indicates that despite its intense surface heat, 55 Cancri e has an atmosphere that is comparable to Earth’s, only much hotter!
The study, titled “A Case for an Atmosphere on Super-Earth 55 Cancri e“, recently appeared in The Astrophysical Journal. Led by Isabel Angelo (a physics major with UC Berkeley) with the assistance of Renyu Hu – a astronomer and Hubble Fellow with JPL and Caltech – the pair conducted a more detailed analysis of the Spitzer data to determine the likelihood and composition of an atmosphere around 55 Cancri e.
Previous studies of the planet noted that this super-Earth (which is twice as large as our planet), orbits very close to its star. As a result, it has a very short orbital period of about 17 hours and 40 minutes and is tidally locked (with one side constantly facing towards the star). Between June and July of 2013, Spitzer observed 55 Cancri e and obtained temperature data using its special infrared camera.
Initially, the temperature data was seen as being an indication that large deposits of lava existed on the surface. However, after re-analyzing this data and combining it with a new model previously develop by Hu, the team began to doubt this explanation. According to their findings, the planet must have a thick atmosphere, since lava lakes exposed to space would create hots spots of high temperatures.
What’s more, they also noted that the temperature differences between the day and night side were not as significant as previously thought – another indication of an atmosphere. By comparing changes in the planet’s brightness to energy flow models, the team concluded that an atmosphere with volatile materials was the best explanation for the high temperatures. As Renyu Hu explained in a recent NASA press statement:
“If there is lava on this planet, it would need to cover the entire surface. But the lava would be hidden from our view by the thick atmosphere. Scientists have been debating whether this planet has an atmosphere like Earth and Venus, or just a rocky core and no atmosphere, like Mercury. The case for an atmosphere is now stronger than ever.”
Using Hu’s improved model of how heat would flow throughout the planet and radiate back into space, they found that temperatures on the day side would average about 2573 K (2,300 °C; 4,200 °F). Meanwhile, temperatures on the “cold” side would average about 1573 – 1673 K (1,300 – 1,400 °C; 2,400 – to 2,600 °F). If the planet had no atmosphere, the differences in temperature would be far more extreme.
As for the composition of this atmosphere, Angelo and Hu revealed that it is likely similar to Earth’s – containing nitrogen, water and even oxygen. While much hotter, the atmospheric density also appeared to be similar to that of Earth, which suggests the planet is most likely rocky (aka. terrestrial) in composition. On the downside, the temperatures are far too hot for the surface to maintain liquid water, which makes habitability a non-starter.
Ultimately, this study was made possible thanks to Hu’s development of a method that makes the study exoplanet atmospheres and surfaces easier. Angelo, who led the study, worked on it as part of her internship with JPL and adapted Hu’s model to 55 Cancri e. Previously, this model had only been applied to mass gas giants that orbit close to their respective suns (aka. “Hot Jupiters”).
Naturally, there are unresolved questions that this study helps to raise, such as how 55 Cancri e has avoided losing its atmosphere to space. Given how close the planet orbits to its star, and the fact that it’s tidally locked, it would be subject to intense amounts of radiation. Further studies may help to reveal how this is the case, and will help advance our understanding of large, rocky planets.
The application of this model to a Super-Earth is the perfect example of how exoplanet research has been evolving in recent years. Initially, scientists were restricted to studying gas giants that orbit close to their stars (as well as their respective atmospheres) since these are the easiest to spot and characterize. But thanks to improvements in instrumentation and methods, the range of planets we are capable of studying is growing.
Images of the Crab Nebula are always a treat because it has such intriguing and varied structure. Also, just knowing that this stellar explosion was witnessed and recorded by people on Earth more than 900 years ago (with the supernova visible to the naked eye for about two years) gives this nebula added fascination.
A new image just might be the biggest Crab Nebula treat ever, as five different observatories combined forces to create an incredibly detailed view, with stunning details of the nebula’s interior region.
Data from the five telescopes span nearly the entire breadth of the electromagnetic spectrum, from radio waves seen by the Karl G. Jansky Very Large Array (VLA) to the powerful X-ray glow as seen by the orbiting Chandra X-ray Observatory. And, in between that range of wavelengths, the Hubble Space Telescope’s crisp visible-light view, and the infrared perspective of the Spitzer Space Telescope.
The Crab is 6,500 light-years from Earth and spans about 10 light-years in diameter. The supernova that created it was first witnessed in 1054 A. D. At its center is a super-dense neutron star that is as massive as the Sun but with only the size of a small town. This pulsar rotates every 33 milliseconds, shooting out spinning lighthouse-like beams of radio waves and light. The pulsar can be seen as the bright dot at the center of the image.
Scientists say the nebula’s intricate shape is caused by a complex interplay of the pulsar, a fast-moving wind of particles coming from the pulsar, and material originally ejected by the supernova explosion and by the star itself before the explosion.
For this new image, the VLA, Hubble, and Chandra observations all were made at nearly the same time in November of 2012. A team of scientists led by Gloria Dubner of the Institute of Astronomy and Physics (IAFE), the National Council of Scientific Research (CONICET), and the University of Buenos Aires in Argentina then made a thorough analysis of the newly revealed details in a quest to gain new insights into the complex physics of the object. They are reporting their findings in the Astrophysical Journal (see the pre-print here).
About the central region, the team writes, “The new HST NIR [near infrared] image of the central region shows the well-known elliptical torus around the pulsar, composed of a series of concentric narrow features of variable intensity and width… The comparison of the radio and the X-ray emission distributions in the central region suggests the existence of a double-jet system from the pulsar, one detected in X-rays and the other in radio. None of them starts at the pulsar itself but in its environs.”
“Comparing these new images, made at different wavelengths, is providing us with a wealth of new detail about the Crab Nebula. Though the Crab has been studied extensively for years, we still have much to learn about it,” Dubner said.
In an encouraging find for habitability researchers, astronomers have detected molecules on the smallest planet ever — a Neptune-sized planet about 120 light-years from Earth. The team behind the discovery says this means the dream of understanding the atmospheres on planets even closer to size of Earth is getting closer.
“The work we are doing now is important for future studies of super-Earths and even smaller planets, because we want to be able to pick out in advance the planets with clear atmospheres that will let us detect molecules,” stated co-author Heather Knutson, of the California Institute of Technology.
This particular world is not life-friendly as we understand it, however. Called HAT-P-11b, it’s not only a gas giant but also a planet that orbits extremely close to its star — making one circle every five days. And unusually among planets of its size that were previously probed by astronomers, it appears to have clear skies.
The team examined the world using the Hubble Space Telescope’s Wide Field Camera 3, looking at the planet as it passed across the face of its star. The team compared the signature of elements observed when the planet was in front of the star and when it was not, and discovered telltale signs of water vapor in its atmosphere.
While other planets outside our solar system are known to have water vapor, the ones previously examined are much larger. Jupiter-sized planets are much easier to examine not only because they are larger, but their atmospheres puff up more (making them more visible from Earth.)
To confirm the water vapor was not a false signal from sunspots on the parent star (which also can contain it), the team used the Kepler and Spitzer space telescopes to confirm the information. (Kepler’s single field of view around the constellation Cygnus, which it had been peering at for about four years, happily included the zone where HAT-P-11b was orbiting.) The infrared information from Spitzer and the visible-light data from Kepler both showed the sunspots were too hot for water vapor.
Further, the discovery shows there were no clouds in the way of the observations — a first for planets of that size. The team also hopes that super-Earths could have clear skies, allowing astronomers to analyze their atmospheres.
“When astronomers go observing at night with telescopes, they say ‘clear skies’ to mean good luck,” stated lead author Jonathan Fraine, of the University of Maryland, College Park. “In this case, we found clear skies on a distant planet. That’s lucky for us because it means clouds didn’t block our view of water molecules.”
After NASA recommended in May that Spitzer space telescope officials send in a revised budget or face possible termination of operations, in a turnaround, the agency’s science mission directorate has now agreed to extend the mission for another two years.
The news broke on Twitter yesterday when the NASA Spitzer account shared the news. An update posted on its website said the decision is “subject to the availability of Congressional appropriations in FY [fiscal year] 2015”, but added that there will soon be a call out for observing time in that period.
Previously, NASA informed Spitzer officials that due to “constrained budget conditions” that their initial request to extend operations past fiscal 2015 was not approved, in line with recommendations from the NASA senior astrophysics review. While the mission was not terminated at that time, officials were asked to “respond with a request for a budget augmentation to conduct continued operations with reduced operations costs.”
The mission was being reviewed at the same time as other astrophysics missions, such as the Kepler planet-hunting space telescope that was asking for (and received) a new mission that would allow it to do useful science despite two busted reaction wheels, or pointing devices. The review said Spitzer was the most expensive of the missions reviewed, and that the telescope’s abilities were “significantly reduced” after it ran out of coolant in 2009.
In an update on the Spitzer website, officials shared more details but did not say if the budget had been reformulated in response to NASA’s suggestion.
We are very happy to report that Spitzer operations have been extended by the NASA Science Mission Directorate for two more years! The letter of direction states: “The Science Mission Directorate has made the decision to extend Spitzer operations for the next two years. The Spitzer observatory is an important resource for on-going infrared observations for research programs across the Science Mission Directorate, and, subject to the availability of Congressional appropriations in FY 2015, it will be continued. Both the Astrophysics and the Planetary Science Divisions have requested observing time commitments for FY 2015, and both Divisions have committed funding to support their observations.” We are working hard to get a call for observing proposals issued by the end of July. And thank you to all the people at NASA Headquarters and in the community that have worked so hard to support science with Spitzer.
Brazilian astronomers have discovered some 300+ star clusters that were largely overlooked owing to sizable obscuration by dust. The astronomers, from the Universidade Federal do Rio Grande do Sul, used data obtained by NASA’s WISE (Wide-Field Infrared Survey Explorer) space telescope to detect the clusters.
“WISE is a powerful tool to probe … young clusters throughout the Galaxy”, remarked the group. The clusters discovered were previously overlooked because the constituent stars are deeply embedded in their parent molecular cloud, and are encompassed by dust. Stars and star clusters can emerge from such environments.
The group added that, “The present catalog of new clusters will certainly become a major source for future studies of star cluster formation.” Indeed, WISE is well-suited to identify new stars and their host clusters because infrared radiation is less sensitive to dust obscuration. The infrared part of the electromagnetic spectrum is sampled by WISE.
Historically, new star clusters were often identified while inspecting photographic plates imaged at (or near) visible wavelengths (i.e., the same wavelengths sampled by the eye). Young embedded clusters were consequently under-sampled since the amount of obscuration by dust is wavelength dependent. As indicated in the figure above, the infrared observations penetrate the dust by comparison to optical observations.
The latest generation of infrared survey telescopes (e.g., Spitzer and WISE) are thus excellent instruments for detecting clusters embedded in their parent cloud, or hidden from detection because of dust lying along the sight-line. The team notes that, “The Galaxy appears to contain 100000 open clusters, but only some 2000 have established astrophysical parameters.” It is hoped that continued investigations using WISE and Spitzer will help astronomers minimize that gap.
When gas and dust squeeze tightly enough together in space, no light can get through and the place is black as pitch. But this dusty cloud seen about 16,000 light-years away from us will eventually generate new stars, with the darkest parts creating powerful O-type stars — a star-type poorly known to scientists.
“The map of the structure of the cloud and its dense cores we have made in this study reveals a lot of fine details about the massive star and star cluster formation process,” stated Michael Butler, a postdoctoral researcher at the University of Zurich in Switzerland who led the study.
The new study, which included observations from NASA’s Spitzer Space Telescope, examined the shadows these clumps cast and concluded this cloud is about 7,000 times more massive than the sun, and about 50 light-years in diameter. Because Spitzer examines the universe in infrared light, this allows it to peer through dusty areas that are difficult or impossible to see in visual light, allowing Spitzer to examine different astronomical phenomena.
Looking at clouds such as this one are expected to shed more light (so to speak) on how O-type stars are created. This stellar type is at least 16 times as massive as the sun (but can be much more) and is known for its wind and powerful radiation, that clean out the neighborhood of any dust or gas that could have formed other planets or stars.
Once these stars reach the end of their short lives, they explode as supernovas and also create heavier elements that are found in rocky planets and in the case of Earth (as far as we know), living beings. Researchers are still unclear on how the stars are able to pick up mass that is so much more the mass of our sun without breaking apart.
Shining 24,000 light-years from Earth is an expanding leftover of a supernova that is doing a great cleanup job in its neighborhood. As this new composite image from NASA reveals, G352.7-0.1 (G352 for short) is more efficient than expected, picking up debris equivalent to about 45 times the mass of the Sun.
“A recent study suggests that, surprisingly, the X-ray emission in G352 is dominated by the hotter (about 30 million degrees Celsius) debris from the explosion, rather than cooler (about 2 million degrees) emission from surrounding material that has been swept up by the expanding shock wave,” the Chandra X-Ray Observatory’s website stated.
“This is curious because astronomers estimate that G352 exploded about 2,200 years ago, and supernova remnants of this age usually produce X-rays that are dominated by swept-up material. Scientists are still trying to come up with an explanation for this behavior.”
Touring the Milky Way’s a blast with this brand new 360-degree interactive panorama. More than 2 million infrared photos taken by NASA’s Spitzer Space Telescope were jigsawed into a 20-gigapixel click-and-zoom mosaic that takes the viewer from tangled nebulae to stellar jets to blast bubbles around supergiant stars.
The new composite, using infrared images taken over the past decade, was compiled by a team led by UW-Madison astronomer Barbara Whitney and unveiled at a TEDactive conference in Vancouver, Canada Thursday. Unlike visual light, infrared penetrates the ubiquitous dust concentrated in the galactic plane to reveal structures otherwise obscured.
Catching a GLIMPSE of the Milky Way in this short video presentation
“For the first time, we can actually measure the large-scale structure of the galaxy using stars rather than gas,” explained Edward Churchwell, UW-Madison professor of astronomy and team co-leader. “We’ve established beyond the shadow of a doubt that our galaxy has a large bar structure that extends halfway out to the sun’s orbit. We know more about where the Milky Way’s spiral arms are.”
Named GLIMPSE360 (Galactic Legacy Mid-Plane Survey Extraordinaire project), the deep infrared survey captures only about 3% of the sky, but because it focuses on the plane of the Milky Way, where stars are most highly concentrated, it shows more than half of all the galaxy’s 300 billion suns.
Using your imagination to hover high above the galactic plane, you’d see the Milky Way is a flat spiral galaxy sporting a stubby bar of stars crossing its central bulge. The solar system occupies a tiny niche in a minor spiral arm called the Orion Spur two-thirds of the way from the center to the edge. At 100,000 light years across, the Milky Way is vast beyond comprehension and yet it’s only one of an estimated 100 billion galaxies in the observable universe.
While you and I sit back and marvel at all the stellar and nebular eye candy, the Spitzer images are helping astronomers determine where the edge of the galaxy lies and location of the spiral arms. GLIMPSE images have already revealed the Milky Way to be larger than previously thought and shot through with bubbles of expanding gas and dust blown by giant stars.
Spitzer can see faint stars in the “backcountry” of our galaxy — the outer, darker regions that went largely unexplored before.
“There are a whole lot more lower-mass stars seen now with Spitzer on a large scale, allowing for a grand study,” said Whitney. “Spitzer is sensitive enough to pick these up and light up the entire ‘countryside’ with star formation.”
The new 360-degree view will also help NASA’s upcoming James Webb Space Telescope target the most interesting sites of star-formation, where it will make even more detailed infrared observations.
When you play around with the interactive mosaic, you’ll notice a few artifacts here and there among the images. Minor stuff. What took some getting used to was how strikingly different familiar nebulae appeared when viewed in infrared instead of visual light. The panorama is also available on the Aladin viewing platform which offers shortcuts to regions of interest.
Neil deGrasse Tyson, astrophysicist and host of the new Cosmos TV series, gave the third line of our “cosmic address” as the Milky Way after ‘Earth’ and ‘Solar System’. After a few minutes with GLIMPSE360 you’ll better appreciate the depth and breadth of our galactic home.
That might seem like a sensational headline worthy of a supermarket tabloid but, taken in context, it’s exactly what’s happening here!
The bright blue star at the center of this image is a B-type supergiant named Kappa Cassiopeiae, 4,000 light-years away. As stars in our galaxy go it’s pretty big — over 57 million kilometers wide, about 41 times the radius of the Sun. But its size isn’t what makes K Cas stand out — it’s the infrared-bright bow shock it’s creating as it speeds past its stellar neighbors at a breakneck 1,100 kilometers per second.
K Cas is what’s called a runway star. It’s traveling very fast in relation to the stars around it, possibly due to the supernova explosion of a previous nearby stellar neighbor or companion, or perhaps kicked into high gear during a close encounter with a massive object like a black hole.
As it speeds through the galaxy it creates a curved bow shock in front of it, like water rising up in front of the bow of a ship. This is the ionized glow of interstellar material compressed and heated by K Cas’ stellar wind. Although it looks like it surrounds the star pretty closely in the image above, the glowing shockwave is actually about 4 light-years out from K Cas… slightly less than the distance from the Sun to Proxima Centauri.
Although K Cas is visible to the naked eye, its bow shock isn’t. It’s only made apparent in infrared wavelengths, which NASA’s Spitzer Space Telescope is specifically designed to detect. Some other runaway stars have brighter bow shocks — like Zeta Ophiuchi at right — which can be seen in optical wavelengths (as long as they’re not obscured by dust, which Zeta Oph is.)
The bright wisps seen crossing K Cas’ bow shock may be magnetic filaments that run throughout the galaxy, made visible through interaction with the ionized gas. In fact bow shocks are of particular interest to astronomers precisely because they help reveal otherwise invisible features and allow deeper investigation into the chemical composition of stars and the regions of the galaxy they are traveling through. Like a speeding car on a dark country road, runaway stars’ bow shocks are — to scientists — like high-beam headlamps lighting up the space ahead.
Runaway stars are not to be confused with rogue stars, which, although also feel the need for speed, have been flung completely out of their home galaxies.