Planet formation is a notoriously difficult thing to observe. Nascent planets are ensconced inside dusty wombs that resist our best observation efforts. But recently, astronomers have made progress in imaging these planetary newborns.
A new study presents the first-ever direct images of twin baby planets forming around their star.
Meredith is a Postdoctoral Researcher in the Department of Astronomy at the University of Washington. She writes software to prepare for the coming onslaught of data from the Large Synoptic Survey Telescope and studies weird binary stars. She is also the lead organizer of the ComSciCon-Pacific Northwest workshop for STEM graduate students in Seattle this March. Meredith holds degrees in physics and astronomy from Harvey Mudd College, San Diego State University, and New Mexico State University. When she’s not science-ing or telling people all about it, she plays viola, volunteers at summer camp, and advocates for more equity and less light pollution.
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Ever since it was approved for construction, the Thirty Meter Telescope has been the subject of controversy. A proposed astronomical observatory that is planned to be built on Mauna Kea – Hawaii’s famous dormant volcano and the home of the Mauna Kea Observatories – the construction of this facility has been delayed multiple times due to resistance from the local community.
Stressing the impact the facility will have on local wild life, the associated noise and traffic, and the fact that the proposed site is on land sacred to Hawaii’s indigenous people, there are many locals who have protested the facility’s construction. But after multiple delays, and the cancellation of the facility’s building permits, it appears that public support may be firmly behind the creation of the TMT.
Planning for the Thirty Meter Telescope began in 2000, when astronomers began considering the construction of telescopes that measured more than 20 meters in diameter. In time, the University of California and Caltech began conducting a series of studies, which would eventually culminate in the plans for the TMT. Site proposals also began to be considered by the TMT board, which led to the selection of Mauna Kea in 2009.
However, after opposition and protests halted construction on three occasions – on Oct. 14th, 2014, then again on April 2th and June 24th of 2015 – the State Supreme Court of Hawaii invalidated the TMT’s building permits. Since that time, multiple polls have been conducted to gauge public support for the project. Whereas a previous one, which was conducting in Oct. 2015, indicated that 59% of Big Island residents supported it (and 39% opposed it) the most recent poll yielded different results.
This poll, which was conducted in July of 2016 by Honolulu-based Ward Research, Inc. shows that 60% of Big Island residents now support moving ahead with construction, while 31% remain opposed. While not a huge change, it does indicate that support for the project now outweighs opposition by a 2 to 1 margin since the last time residents were asked, roughly nine months ago.
The first poll surveyed 613 Hawaii Big Island residents, aged 18 years and older and from a variety of backgrounds. The most recent poll surveyed 404 Hawaii residents at least 18 years old via both cellphone and landline (with a margin of error of plus or minus 4.9 percent).
The recent poll also indicated that the majority of respondents, ranging from 66% to 76%, believe that TMT will provide economic and educational opportunities, and that not moving forward would be bad for the island and its residents. Also of interest was the fact that support for TMT’s construction was split among Indigenous Hawaiians, with 46 percent of those polled in support and 45 percent opposed.
As Ed Stone, the TMT Executive Director, said of the results in a recent press release:
“It was important for us to understand how Hawaii Island residents feel about the project, and the latest poll results demonstrate that opposition to TMT on Hawaii Island is decreasing. That’s significant and we are most grateful that the community’s support of the project remains high. The findings also show that the general public on Hawaii Island understands the benefits TMT will bring in terms of Hawaii’s economy and education, both of which are very important to TMT.”
What is perhaps most relevant is the fact that while this most-recent poll shows virtually no change in the amount of support, it does show that opposition has decreased. The reason for this is not clear, but according to Kealoha Pisciotta of the Mauna Kea Hui – which is litigating against TMT’s construction – the change is attributable to the PR efforts of TMT, which hired Honolulu-based PR firm to promote their agenda.
Pisciotta also stressed that the state Constitution of Hawaii protects the cultural and traditional practices that will be affected by this massive project, which is something residents don’t appear to understand. Faced with the promise of benefits – which includes TMT’s annual $1 million contribution to The Hawaii Island New Knowledge (THINK) Fund, which provides for STEM education.
This is not to say that those polled rejected the concerns of those advocating for protection of Hawaiian heritage and culture. In fact, 89% of respondents – the largest return in the poll – indicated that “there should be a way for science and Hawaiian culture to co-exist”. While this is easier said than done, it does show that compromise is the most popular option, and could present a mutually-satisfactory way of moving forward.
What’s more, this is hardly the first time that Mauna Kea has been at the center of controversy. Ever since construction began on the Astronomy Precinct in 1967, there has been opposition from environmentalists and the Indigenous community. Not only is the Precinct located on land protected by the Historical Preservation Act of 1966 due to its significance to Hawaiian culture, it is also the habitat of an endangered species of bird (the Palila).
Nevertheless, Mauna Kea remains the preferred choice for the location of the TMT, though the board is evaluating alternative sites in case the project cannot move forward. Stone and his colleagues hope to resume construction of the TMT facility by April of 2018, and begin gathering images of the cosmos in the near-ultraviolet to mid-infrared by the 2020s.
The Asteroid Belt is a pretty interesting place. In addition to containing between 2.8 and 3.2 quintillion metric tons of matter, the region is also home to many minor planets. The largest of these, known as Ceres, is not only the largest minor planet in the Inner Solar System, but also the only body in this region to be designated as a “dwarf planet” by the International Astronomical Union (IAU).
Due to its size and shape, when it was first observed, Ceres was thought to be a planet. While this belief has since been revised, Ceres is alone amongst objects in the Asteroid Belt in that it is the only object massive enough to have become spherical in shape. And like most of the dwarf planets in our Solar System, its status remains controversial, and our knowledge of it limited.
Discovery and Naming:
Ceres was discovered by Giuseppe Piazzi on January 1st, 1801, while searching for zodiacal stars. However, the existence of Ceres had been predicted decades before by Johann Elert Bode, a German astronomer who speculated that there had to be a planet between Mars and Jupiter. The basis for this assumption was the now defunct Bode-Titus law, which was first proposed by Johann Daniel Titius in 1766.
This law stated that there existed a regular pattern in the semi-major axes of the orbits of known planets, the only exception of which was the large gap between Mars and Jupiter. In an attempt to resolve this, in 1800, German astronomer Franz Xaver von Zach sent requests to twenty-four experienced astronomers (dubbed the “Celestial Police”) to combine their their efforts to located this missing planet.
One of these astronomers was Giuseppe Piazzi at the Academy of Palermo, who had made the discovery shortly before his invitation to join the group had arrived. At the time of his discovery, he mistook it for a comet, but subsequent observations led him to declare that it could be something more. He officially shared his observations with friends and colleagues by April of 1801, and sent the information to von Zach to be published in September.
Unfortunately, due to its change in its apparent position, Ceres was too close to the Sun’s glare to be visible to astronomers. It would not be until the end of the year that it would be spotted again, thanks in large part to German astronomer Carl Freidrich Gauss and the predictions he made of its orbit. On December 31st, von Zach and his colleague Heinrich W.M. Olbers found Ceres near the position predicted by Gauss, and thus recovered it.
Piazzi originally suggesting naming his discovery Cerere Ferdinandea, after the Roman goddess of agriculture Ceres (Cerere in Italian) and King Ferdinand of Sicily. The name Ferdinand was dropped in other nations, but Ceres was eventually retained. Ceres was also called Hera for a short time in Germany; whereas in Greece, it is still called Demeter after the Greek equivalent of the Roman goddess Ceres.
The classification of Ceres has changed more than once since its discovery, and remains the subject of controversy. For example, Johann Elert Bode – a contemporary of Piazzi – believed Ceres to be the “missing planet” he had proposed to exist between Mars and Jupiter. Ceres was assigned a planetary symbol, and remained listed as a planet in astronomy books and tables (along with 2 Pallas, 3 Juno, and 4 Vesta) until the mid-19th century.
As other objects were discovered in the neighborhood of Ceres, it was realized that Ceres represented the first of a new class of objects. In 1802, with the discovery of 2 Pallas, William Herschel coined the term asteroid (“star-like”) for these bodies. As the first such body to be discovered, Ceres was given the designation 1 Ceres under the modern system of minor-planet designations.
By the 1860s, the existence of a fundamental difference between asteroids such as Ceres and the major planets was widely accepted, though a precise definition of “planet” was never formulated. The 2006 debate surrounding Eris, Pluto, and what constitutes a planet led to Ceres being considered for reclassification as a planet.
The definition that was adopted on August 24th, 2006 carried the requirements that a planet have sufficient mass to assume hydrostatic equilibrium, be in orbit around a star and not be a satellite, and have cleared the neighborhood around its orbit. As it is, Ceres does not dominate its orbit, but shares it with the thousands of other asteroids, and constitutes only about a third of the mass of the Asteroid Belt. Bodies like Ceres that met some of these qualification, but not all, were instead classified as “dwarf planets”.
In addition to the controversy surrounding the use of this term, there is also the question of whether or not Ceres status as a dwarf planet means that it can no longer be considered an asteroid. The 2006 IAU decision never addressed whether Ceres is an asteroid or not. In fact, the IAU has never defined the word ‘asteroid’ at all, having preferred the term ‘minor planet’ until 2006, and the terms ‘small Solar System body’ and ‘dwarf planet’ thereafter.
Size, Mass and Orbit:
Early observations of Ceres were only able to calculate its size to within an order of magnitude. In 1802, English astronomer William Herschel underestimated its diameter as 260 km, whereas in 1811 Johann Hieronymus Schröter overestimated it as 2,613 km. Current estimates place its mean radius at 473 km, and its mass at roughly 9.39 × 1020 kg (the equivalent of 0.00015 Earths or 0.0128 Moons).
With this mass, Ceres comprises approximately a third of the estimated total mass of the asteroid belt (which is in turn approximately 4% of the mass of the Moon). The next largest objects are Vesta, Pallas and Hygiea, which have mean diameters of more than 400 km and masses of 2.6 x 1020 kg, 2.11 x 1020 kg, and 8.6 ×1019 kg respectively. The mass of Ceres is large enough to give it a nearly spherical shape, which makes it unique amongst objects and minor planets in the Asteroid Belt.
Ceres follows a slightly inclined and moderately eccentric orbit, ranging from 2.5577 AU (382.6 million km) from the Sun at perihelion and 2.9773 AU (445.4 million km) at aphelion. It has an orbital period of 1,680 Earth days (4.6 years) and takes 0.3781 Earth days (9 hours and 4 minutes) to complete a sidereal rotation.
Composition and Atmosphere:
Based on its size and density (2.16 g/cm³), Ceres is believed to be differentiated between a rocky core and an icy mantle. Based on evidence provided by the Keck telescope in 2002, the mantle is estimated to be 100 km-thick, and contains up to 200 million cubic km of water – which is more fresh water than exists on Earth. Infrared data on the surface also suggests that Ceres may have an ocean beneath its icy mantle.
If true, it is possible that this ocean could harbor microbial extraterrestrial life, similar to what has been proposed about Mars, Titan, Europa and Enceladus. It has further been hypothesized that ejecta from Ceres could have sent microbes to Earth in the past.
Other possible surface constituents include iron-rich clay minerals (cronstedtite) and carbonate minerals (dolomite and siderite), which are common minerals in carbonaceous chondrite meteorites. The surface of Ceres is relatively warm, with the maximum temperature estimated to reach approximately 235 K (-38 °C, -36 °F) when the Sun is overhead.
Assuming the presence of sufficient antifreeze (such as ammonia), the water ice would become unstable at this temperature. Therefore, it is possible that Ceres may have a tenuous atmosphere caused by outgassing from water ice on the surface. The detection of significant amounts of hydroxide ions near Ceres’ north pole, which is a product of water vapor dissociation by ultraviolet solar radiation, is another indication of this.
However, it was not until early 2014 that several localized mid-latitude sources of water vapor were detected on Ceres. Possible mechanisms for the vapor release include sublimation from exposed surface ice (as with comets), cryovolcanic eruptions resulting from internal heat, and subsurface pressurization. The limited amount of data suggests that the vaporization is more consistent with cometary-style sublimation.
Multiple theories exist as to the origin of Ceres. On the one hand, it is widely believed that Ceres is a surviving protoplanet which formed 4.57 billion year ago in the Asteroid Belt. Unlike other inner Solar System protoplanets, Ceres neither merged with others to form a terrestrial planet and avoided being ejected from the Solar System by Jupiter. However, there is an alternate theory that proposes that Ceres formed in the Kuiper belt and later migrated to the asteroid belt.
The geological evolution of Ceres is dependent on the heat sources that were available during and after its formation, which would have been provided by friction from planetesimal accretion and decay of various radionuclides. These are thought to have been sufficient to allow Ceres to differentiate into a rocky core and icy mantle soon after its formation. This icy surface would have gradually sublimated, leaving behind various hydrated minerals like clay minerals and carbonates.
Today, Ceres appears to be a geologically inactive body, with a surface sculpted only by impacts. The presence of significant amounts of water ice in its composition is what has led scientists to the possible conclusion that Ceres has or had a layer of liquid water in its interior.
Until recently, very few direct observations had been made of Ceres and little was known about its surface features. In 1995, the Hubble Space Telescope captured high-resolutions images that showed a dark spot in the surface that was thought to be a crater – and nicknamed “Piazzi” after its founder.
The near-infrared images taken by the Keck telescope in 2002 showed several bright and dark features moving with Ceres’s rotation. Two of the dark features had circular shapes and were presumed to be craters. One was identified as the “Piazzi” feature, while the other was observed to have a bright central region. In 2003 and 2004, visible-light images were taken by Hubble during a full rotation that showed 11 recognizable surface features, the natures of which are yet undetermined.
With the launch of the Dawn mission, with which NASA intends to conduct a nearly decade-long study of Ceres and Vesta, much more has been learned about this dwarf planet. For instance, after achieving orbit around the asteroid in March of 2015, Dawn revealed a large number of surface craters with low relief, indicating that they mark a relatively soft surface, most likely made of water ice.
Several bright spots have also been observed by Dawn, the brightest of which (“Spot 5”) is located in the middle of an 80 km (50 mi) crater called Occator. These bright features have an albedo of approximately 40% that are caused by a substance on the surface, possibly ice or salts, reflecting sunlight. A haze periodically appears above Spot 5, supporting the hypothesis that some sort of outgassing or sublimating ice formed the bright spots.
The Dawn spacecraft also noted the presence of a towering 6 kilometer-tall mountain (4 miles or 20,000 feet) in early August, 2015. This mountain, which is roughly pyramidal in shape and protrudes above otherwise smooth terrain, appears to be the only mountain of its kind on Ceres.
Like so many celestial bodies in our Solar System, Ceres is a mystery that scientists and astronomers are working to slowly unravel. In time, our exploration of this world will likely teach us much about the history and evolution of our Solar System, and may even lead to the discovery of life beyond Earth.
Astronomers from the Keck Telescope in Hawaii will be trying to observe Asteroid 2005 YU55 as it flies away from Earth. A live webcast from Keck starts about the same time this article is being published, starting no later than 9 pm U.S. PST on Nov. 8, or Midnight EST/ 0500 UT on Wednesday, Nov. 9. Indications are the webcast might start a little late because of fog on Mauna Kea.
Their hope is to get infrared images and perhaps a three-dimensional view of the asteroid with one of the world’s largest optical/infrared telescopes. The observing run is being webcast live on UStream from the Keck II Remote Operations room in Kamuela, Hawaii. They also are hoping to be able to look for moons around the asteroid. About 20% of asteroids have “moons” orbiting them.
At the helm of the 10-meter Keck II telescope and using Keck’s pioneering adaptive optics to view YU55 will be asteroid investigators William Merline and Peter Tamblyn of Southwest Research Institute, in Boulder, Colorado, and Chris Neyman of Keck Observatory.
Popular theory on how Uranus ended up with a highly eccentric axis has always been pretty standard – one giant blow. However, at today’s (October 6) EPSC-DPS Joint Meeting in Nantes, astronomers are thinking things may have occurred slightly differently. Instead of a singular impact, the glowing blue-green gas giant may have been the victim of a series of smaller punches.
At a 98 degree inclination, Uranus and its satellites have always been somewhat of a mystery to planetary scientists. While many of the Solar Systems planets have an inclined axis, none can compare with nearly being on its side. It has always been popular conjecture that Uranus was plastered that way at some point in its evolution by a body a few times larger than Earth. While this seems plausible, only one hole remains in the theory. Why did its moons take on the same inclination instead of staying in their original position?
This long-standing puzzle may have been solved by an international team of scientists led by Alessandro Morbidelli (Observatoire de la Cote d’Azur in Nice, France). Their theory relies on computer modeling – and the thought the impact might have occurred while Uranus was still forming. If the simulations are correct and the strike happened when the planet was still surrounded by a protoplanetary disk, ” the disk would have reformed into a fat doughnut shape around the new, highly-tilted equatorial plane. Collisions within the disk would have flattened the doughnut, which would then go onto form the moons in the positions we see today.”
But that’s not a neat answer. Just like throwing a tilt into pinball, the game changes. In this new scheme, the moons displayed retrograde motion – precisely the opposite of the way things are now. So what’s a player to do? Change the game again by re-arranging the parameters. By adding multiple strikes to Uranus – instead of just one large – the satellites now behave as we observe them.
Of course, when you “tilt” the game is over, and the new research doesn’t jive with current theories of planetary formation. This may mean re-writing the rules again. Morbidelli elaborates: “The standard planet formation theory assumes that Uranus, Neptune and the cores of Jupiter and Saturn formed by accreting only small objects in the protoplanetary disk. They should have suffered no giant collisions. The fact that Uranus was hit at least twice suggests that significant impacts were typical in the formation of giant planets. So, the standard theory has to be revised.”
That deaf, dumb and blind kid… Sure plays a mean pinball!