This artist’s impression shows an ultra-hot exoplanet as it is about to transit in front of its host star. Credit: ESO
Astronomers have discovered an intense binary star system located about 1,400 light years away. It contains a brown dwarf with 80 times the mass of Jupiter which is bound closely with an incredibly hot white dwarf star. Observations have shown the brown dwarf is tidally locked to the white dwarf, allowing the daytime surface temperatures on the brown dwarf to reach 8,000 Kelvin (7,700 Celsius, 14,000 Fahrenheit) — which is much hotter than the surface of the Sun, which is about 5,700 K (5,427 C, 9,800 F). The brown dwarf’s nightside, on the other hand, is about 6,000 degrees K cooler.
Artist’s impression of an aurora and the surrounding radiation belt of the ultracool dwarf LSR J1835+3259. Credit: Chuck Carter/Melodie Kao/Heising-Simons Foundation)
In 1958, the first satellites launched by the United States (Explorer 1and 3) detected a massive radiation belt around planet Earth. This confirmed something that many scientists suspected before the Space Age began: that energetic particles emanating from the Sun (solar wind) were captured and held around the planet by Earth’s magnetosphere. This region was named the Van Allen Belt in honor of University of Iowa professor James Van Allen who led the research effort. As robotic missions explored more of the Solar System, scientists discovered similar radiation belts around Jupiter, Saturn, Uranus, and Neptune.
Given the boom in extrasolar planet research, scientists have eagerly awaited the day when a Van Allen Belt would be discovered around an exoplanet. Thanks to a team of astronomers led by the University of California, Santa Cruz (UCSC) and the National Radio Astronomy Observatory (NRAO), that day may have arrived! Using the global High Sensitivity Array (HSA), the team obtained images of persistent, intense radio emissions from an ultracool dwarf star. These revealed the presence of a cloud of high-energy particles forming a massive radiation belt similar to what scientists have observed around Jupiter.
This artist’s rendering shows the Extremely Large Telescope in operation on Cerro Armazones in northern Chile. The telescope is shown using lasers to create artificial stars high in the atmosphere. Image: ESO/E-ELT
The field of astronomy is about to be revolutionized, thanks to the introduction of Extremely Large Telescopes that rely on primary mirrors measuring 30 meters (or more) in diameter, adaptive optics (AO), coronographs, and advanced spectrometers. This will include the eponymously-named Extremely Large Telescope (ELT), the Giant Magellan Telescope (GMT), and the Thirty Meter Telescope (TMT). These telescopes will enable astronomers to study exoplanets using the Direct Imaging (DI) method, which will yield valuable data on the composition of their atmospheres.
According to a new study by a team of researchers from Ohio State University (OSU), these telescopes will also allow astronomers to study “ultracool objects,” like very low-mass stars (VLMs), brown dwarfs, and exoplanets. In addition to being able to visualize magnetic starspots and determine the chemical compositions of these objects, ELTs will be able to reveal details about atmospheric dynamics and cloud systems. These types of studies could reveal a wealth of information about some of the least-studied objects in our Universe and significantly aid in the search for life beyond our Solar System.
This mosaic is composed of images covering the entire sky, taken by the Wide-field Infrared Survey Explorer (WISE) as part of WISE’s 2012 All-Sky Data Release. By observing the entire sky, WISE can search for faint objects, like distant galaxies, or survey groups of cosmic objects.
Credits: NASA/JPL-Caltech/UCLA
The Universe is over 13 billion years old, so a 12-year slice of that time might seem uneventful. But a timelapse movie from NASA shows how much can change in just over a decade. Stars pulse, asteroids follow their trajectories, and distant black holes flare as they pull gas and dust toward themselves.
Artist's rendering of an Earth-sized rogue planet approaching a star. Credit: Christine Pulliam (CfA)
The search for life on exoplanets takes a fairly conservative approach. It focuses on life that is similar to that of Earth. Sure, it’s quite possible that life comes in many exotic forms, and scientists have speculated about all the strange forms life might take, but the simple fact is that Earth life is the only form we currently understand. So most research focuses on life forms that, like us, are carbon based with a biology that relies on liquid water. But even with that narrow view, life could still be hiding in places we don’t expect.
NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill (wikimedia commons)
So, you want to find dark matter, but you don’t know where to look? A giant planet might be exactly the kind of particle detector you need! Luckily, our solar system just happens to have a couple of them available, and the biggest and closest is Jupiter. Researchers Rebecca Leane (Stanford) and Tim Linden (Stockholm) released a paper this week describing how the gas giant just might hold the key to finding the elusive dark matter.
NASA’s Wide Field Infrared Survey Telescope (WFIRST) is now named the Nancy Grace Roman Space Telescope, after NASA’s first Chief of Astronomy.
Credits: NASA
In 2025, the Nancy Grace Roman space telescope will launch to space. Named in honor of NASA’s first chief astronomer (and the “Mother of Hubble“), the Roman telescope will be the most advanced and powerful observatory ever deployed. With a camera as sensitive as its predecessors, and next-generation surveying capabilities, Roman will have the power of “One-Hundred Hubbles.”
In order to meet its scientific objectives and explore some of the greatest mysteries of the cosmos, Roman will be fitted with a number of infrared filters. But with the decision to add a new near-infrared filter, Roman will exceed its original design and be able to explore 20% of the infrared Universe. This opens the door for exciting new research and discoveries, from the edge of the Solar System to the farthest reaches of space.
This artist's conception illustrates the brown dwarf named 2MASSJ22282889-431026, observed by NASA's Hubble and Spitzer space telescopes. Brown dwarfs are more massive and hotter than planets but lack the mass required to become stars.
Image credit: NASA
In some ways, brown dwarfs are nature’s stellar oddballs. A lot of stars exhibit strange behaviour at different times in their evolution. But brown dwarfs aren’t even certain that they’re stars at all.
But that doesn’t mean astronomers don’t want to study and understand them.
Artist’s impression of the free-floating object known as CFBDSIR J~214947.2-040308.9. Credit: ESO/L. Calçada/P. Delorme/R. Saito/VVV Consortium.
In the hunt for exoplanets, some rather strange discoveries have been made. Beyond our Solar System, astronomers have spotted gas giants and terrestrial planets that appear to be many orders of magnitude larger than what we are used to (aka. “Super-Jupiters” and “Super-Earths”). And in some cases, it has not been entirely clear what our instruments have been detecting.
For instance, in some cases, astronomers have not been sure if an exoplanet candidate was a super-Jupiter or a brown dwarf. Not only do these substellar-mass stars fall into the same temperature range as massive gas giants, they also share many of the same physical properties. Such was the conundrum addressed by an international team of scientists who recently conduced a study of the object known as CFBDSIR 2149-0403.
Located between 117 and 143 light-years from Earth, this mysterious object is what is known as a “free-floating planetary mass object”. It was originally discovered in 2012 by a team of French and Canadian astronomers led by Dr. Phillipe Delorme of the University Grenoble Alpes using the Canada-France Brown Dwarfs Survey – a near infrared sky survey with the Canada-France Hawaii Telescope at Mauna Kea.
The Canada France Hawaii Telescope, near the summit of Mauna Kea, Hawaii. Credit: cfht.hawaii.edu/
The existence of this object was then confirmed using data by the Wide-field Infrared Survey Explorer (WISE), and was believed at the time to be part of a group of stars known as the AB Doradus Moving Group (30 stars that are moving through space). The data collected on this object placed its mass at between 4 and 7 Jupiter masses, its age at 20 to 200 million years, and its surface temperature at about 650-750 K.
This was the first time that such an object had constraints placed upon its mass and age using spectral data. However, questions remained about its true nature – whether it was a low mass, high-metallicity brown dwarf or a isolated planetary mass. For the sake of their study, Delorme and the international team conducted a multi-wavelength, multi-instrument observational characterization of CFBDSIR 2149-0403.
“The X-Shooter data enabled a detailed study of the physical properties of this object. However, all the data presented in the paper is really necessary for the study, especially the follow-up to obtain the parallax of the object, as well as the Spitzer photometry. Together, they enable us to get the bolometric flux of the object, and hence constraints that are almost independent from atmosphere model assumptions.”
An artist’s conception of a T-type brown dwarf star. Credit: Wikimedia Commons/Tyrogthekreeper
From the combined data, they were able to characterize the absolute flux of the CFBDSIR 2149-0403, obtain readings on its spectrum, and even determine the radial velocity of the object. They were therefore able to determine that it not likely a member of a moving population of stars, as was previously expected.
“We now reject our initial hypothesis that CFBDSIR 2149-0403 would be a member of the AB Doradus moving group,” said Delorme. “This removes the most robust age constraint we had. Though determining that certainly improved our knowledge of the object it also made it more difficult to study, by adding age as a free parameter.”
As for what it is, they narrowed that down to one of two possibilities. Basically, it could be a planetary-mass object with a mass of between 2 and 13 Jupiters that is less than 500 million years in age, or a high metallicity brown dwarf that is between 2 and 40 Jupiter masses and two to three billion years in age. Ultimately, they acknowledge that this uncertainty is due to the fact that our theoretical understanding of cool, low-gravity, and metallicity-enhanced bodies is not robust enough yet.
Much of this has to do with the fact that brown dwarfs and super gas giants have common physical parameters that produce very similar effects in the spectra of their atmospheres. But as astronomers gain more of an understanding of planetary formation, which is made possible by the discovery of so many extra-solar planetary systems, we might just find where the line between the smallest of stars and the largest of gas giants is drawn.
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.
