NGC 1270 is just one member of the Perseus Cluster, a group of thousands of galaxies that lies around 240 million light-years from Earth in the constellation Perseus. This image, taken with the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North telescope, one half of the International Gemini Observatory, captures a dazzling collection of galaxies in the central region of this enormous cluster. Image Credit: International Gemini Observatory/NOIRLab/NSF/AURA/
Image Processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab)
Acknowledgements: PI: Jisu Kang (Seoul National University)
The elliptical galaxy NGC 1270 lies about 240 million light-years away. But it’s not alone. It’s part of the Perseus Cluster (Abell 426), the brightest X-ray object in the sky and one of the most massive objects in the Universe.
NGC 1270 plays a starring role in a new image from the Gemini North telescope. However, the image doesn’t show the dark matter that has a firm grip on the galaxy and the rest of the galaxies in the Perseus Cluster.
This illustration depicts two quasars in the process of merging. There are many unanswered questions around galaxy mergers and the quasars that can result. Image Credit: NOIRLab/NSF/AURA/M. Garlick)
Studying the history of science shows how often serendipity plays a role in some of the most important discoveries. Sometimes, the stories are apocryphal, like Newton getting hit on the head with an apple. But sometimes, there’s an element of truth to them. That was the case for a new discovery of the oldest pair of merging quasars ever discovered – and it all started with a pair of red blots on a picture.
Artist's conception of how WISE 0855 might appear if viewed close-up in infrared light. Artwork by Joy Pollard, Gemini Observatory/AURA.
Brown dwarfs – those not-quite-a-planet and not-quite-a-star objects – are intriguing oddities that are too low in mass to burn hydrogen, but are more massive than planets. They only emit a faint amount of light, so they are hard to detect, making scientists unsure of how many of them might be out there in our galaxy.
But astronomers have been keeping an eye one particular brown dwarf known called WISE 0855. Just 7.2 light-years from Earth, it is the coldest known object outside of our Solar System and is just barely visible at infrared wavelengths. But with some crafty spectroscopic observing techniques, astronomers have now determined this object has some exciting characteristics: its atmosphere is full of clouds of water vapor. This is the first time water clouds have been detected outside of our Solar System.
“It’s five times fainter than any other object detected with ground-based spectroscopy at this wavelength,” said Andrew Skemer, assistant professor of astronomy and astrophysics at UC Santa Cruz and the first author on a paper on WISE 0855 published in Astrophysical Journal Letters (paper is available on arXiv here). “Now that we have a spectrum, we can really start thinking about what’s going on in this object. Our spectrum shows that WISE 0855 is dominated by water vapor and clouds, with an overall appearance that is strikingly similar to Jupiter.”
This brown dwarf’s full name is WISE J085510.83-071442.5, but we’re among friends, so it’s W0855 for short. It has about five times the mass of Jupiter and is the coldest brown dwarf ever detected, with an average temperature of about 250 degrees Kelvin, or minus 10 degrees F, minus 20 C. That makes it nearly as cold as Jupiter, which is 130 degrees Kelvin.
“WISE 0855 is our first opportunity to study an extrasolar planetary-mass object that is nearly as cold as our own gas giants,” Skemer said.
Skemer and his team used the Gemini-North telescope in Hawaii and the Gemini Near Infrared Spectrograph to observe WISE 0855 over 13 nights for a total of about 14 hours. Skemer was part of a team that studied this object in 2014 found tentative indications of water clouds based on very limited photometric data. Skemer said obtaining a spectrum (which separates the light from an object into its component wavelengths) was the only way to detect this object’s molecular composition.
A video about the 2014 discovery and study of WISE 0855:
WISE 0855 is too faint for conventional spectroscopy at optical or near-infrared wavelengths, but the team took up a challenge and looked at the thermal emissions from the object at wavelengths in a narrow window around 5 microns.
“I think everyone on the research team really believed that we were dreaming to think we could obtain a spectrum of this brown dwarf because its thermal glow is so feeble,” said Skemer. WISE 0855, is so cool and faint that many astronomers thought it would be years before a spectrum could be obtained. “I thought we’d have to wait until the James Webb Space Telescope was operating to do this,” Skemer said.
This spectroscopic view provided a glimpse into the environment of WISE 0855’s atmosphere. With the data in hand, the researchers then developed atmospheric models of the equilibrium chemistry for a brown dwarf at 250 degrees Kelvin and calculated the resulting spectra under different assumptions, including cloudy and cloud-free models. The models predicted a spectrum dominated by features resulting from water vapor, and the cloudy model yielded the best fit to the features in the spectrum of WISE 0855.
While the spectra of this object are strikingly similar to Jupiter, WISE 0855 appears to have a less turbulent atmosphere.
“The spectrum allows us to investigate dynamical and chemical properties that have long been studied in Jupiter’s atmosphere, but this time on an extrasolar world,” Skemer said.
The scientists say WISE 0855 looks more similar to Jupiter than any exoplanet yet discovered, which is especially intriguing since the Juno mission has just begun its exploration at the giant world. Jupiter, along with the other gas planets in our Solar System, all have clouds and storms, although Jupiter’s clouds are mainly made of ammonia with lower level clouds perhaps containing water. One of Juno’s goals is to determine the global water abundance at Jupiter.
A “speckle image” reconstruction of Pluto and its largest moon, Charon (Gemini Observatory/NSF/NASA/AURA)
Real planet, dwarf planet, KBO, who cares? What matters here is that astronomers have created the sharpest image of Pluto ever made with ground-based observations — and developed a new way to verify potential Earth-like exoplanets at the same time.
Here’s how they did it:
After taking a series of quick “snapshots” of Pluto and Charon using a recently-developed camera called the Differential Speckle Survey Instrument (DSSI), which was mounted on the Gemini Observatory’s 8-meter telescope in Hawaii, researchers combined them into a single image while canceling out the noise caused by turbulence and optical aberrations. This “speckle imaging” technique resulted in an incredibly clear, crisp image of the distant pair of worlds — especially considering that 1. it was made with images taken from the ground, 2. Pluto is small, and 3. Pluto is very, very far away.
Less than 3/4 the diameter of our Moon, Pluto (and Charon, which is about half that size) are currently circling each other about 3 billion miles from Earth — 32.245 AU to be exact. That’s a long way off, and there’s still much more that we don’t know than we do about the dwarf planet’s system. New Horizons will fill in a lot of the blanks when it passes close by Pluto in July 2015, and images like this can be a big help to mission scientists who want to make sure the spacecraft is on a safe path.
“The Pluto-Charon result is of timely interest to those of us wanting to understand the orbital dynamics of this pair for the 2015 encounter by NASA’s New Horizons spacecraft,” said Steve Howell of the NASA Ames Research Center, who led the Gemini imaging study.
In addition, the high resolution achievable through the team’s speckle imaging technique may also be used to confirm the presence of exoplanet candidates discovered by Kepler. With an estimated 3- to 4-magnitude increase in imaging sensitivity, astronomers may be able to use it to pick out the optical light reflected by a distant Earth-like world around another star.
Speckle imaging has been used previously to identify binary star systems, and with the comparative ability to “separate a pair of automobile headlights in Providence, RI, from San Francisco, CA” there’s a good chance that it can help separate an exoplanet from the glare of its star as well.
Main image: the first speckle reconstructed image for Pluto and Charon from which astronomers obtained not only the separation and position angle for Charon, but also the diameters of the two bodies. North is up, east is to the left, and the image section shown is 1.39 arcseconds across. Resolution of the image is about 20 milliarcseconds rms. Credit: Gemini Observatory/NSF/NASA/AURA. Inset: the Gemini North telescope on the summit of Mauna Kea. (Gemini Observatory)
Gemini South laser guide star system propagating as the Milky Way rises.
[/caption]When it comes to astrophotography, most of us would think that space-based telescopes like the Hubble are the epitome of imagining. However, there’s something new to be said about being “grounded”. On December 16, 2011, the Gemini South telescope in Chile revealed its first wide-field, ultra-sharp image… the product of a decade of hard work. By employing a new generation of adaptive optics (AO), the scope produced an incredible look into the densely concentrated globular cluster, NGC 288, and captured stars at close to the theoretical resolution limit of Gemini’s massive 8-meter mirror.
The Gemini Multi-conjugate adaptive optics System (GeMS for short), produced an incredible vision… one of incredible resolution. This new system will allow astronomers to study galactic centers and their black holes – as well as the life patterns of singular stars – with incredible clarity. It’s the largest amount of area ever captured in a single observation – one that’s ten times larger than any adaptive optics systems has ever been able to capture before. It has cause quite a stir in the astronomical community. When Space Telescope Science Institute director Matt Mountain saw the first light image, he praised the GeMS instrument team: “Incredible! You have truly revolutionized ground-based astronomy!”
As the director of the Gemini Observatory, Dr. Mountain was around when the project first began 10 years ago. He was responsible for assembling the team, including Francois Rigaut as the lead scientist to develop the GeMS instrument. And, Rigaut was there for first light… “We couldn’t believe our eyes!” Rigaut recalls. “The image of NGC 288 revealed thousands of pinpoint stars. Its resolution is Hubble-quality – and from the ground this is phenomenal.” Of course, one of the most amazing aspects of the image was how widely spaced the stars appeared, to which Rigaut comments: “This is somewhat uncharted territory: no one has ever made images so large with such a high angular resolution.”
Gemini South’s “first light” image from GeMS/GSAOI shows extreme detail in the central part of the globular star cluster NGC 288. The image, taken at 1.65 microns (H band) on December 16, 2011, has a field-of-view 87 x 87 arcseconds. The average full-width at half-maximum is slightly below 0.080 arcsecond, with a variation of 0.002 arcsecond across the entire field of the image. Exposure time was 13 minutes. Insets on the right show a detail of the image (top), a comparison of the same region with classical AO (middle; this assumes using the star at the upper right corner as the guide star), and seeing-limited observations (bottom). The pixel size in the latter was chosen to optimize the signal-to-noise ratio while not degrading the intrinsic angular resolution of the image. North is up, East is right.
Even though this is an incredible insight, some members of the scientific team which use the Gemini telescope are a bit more reserved in their comments. According to University of Toronto astronomer Roberto Abraham, one of a community of hundreds of astronomers worldwide who uses the 8-meter Gemini telescopes for cutting-edge research: “This is fan-freaking-tastic!!!!!!!” Exuberant? Of course! Even the environmental conditions remained as perfect as they could be for the first run of the GeMS equipment. “We were lucky to have clear weather and stable atmospheric conditions that night,” said Gemini AO scientist Benoit Neichel. “Even despite interruptions of the laser propagation due to satellites and planes passing by, we obtained our first image with the system. It was surprisingly crisp and large, with an exquisitely uniform image quality.”
How is it accomplished? GeMS employs five laser guide stars, three deformable mirrors and a full arsenal of computers to provide a near diffraction limited image to the Gemini South Adaptive Optics Imager (GSAOI, built by the Australian National University) and the infrared-sensitive imager attached to it. This means the smallest detail that can be resolved measures about 0.04 to 0.06 arcsecond over a field of 85 arcseconds squared. Compared to 0.5 arcsecond “seeing limited” at a good viewing location, that’s phenomenal! Once resolution was solved, the next problem was extending the field of view through a technique called Multi-Conjugate Adaptive Optics (MCAO) – an endeavor which borrowed technology from other scientific fields, such as medical imaging.
“MCAO is game-changing,” Abraham said. “It’s going to propel Gemini to the next echelon of discovery space as well as lay a foundation for the next generation of extremely large telescopes. Gemini is going to be delivering amazing science while paving the way for the future.”
