A Nearby Star Is Birthing a Massive Icy World
The young sun-like star TW Hydrae is showing signs that a massive exoplanet is forming within its protoplanetary disk.
TW Hydrae is something of a celebrity in protoplanetary circles. The 10 million year old star is thought to resemble our sun when it was young and, as observational techniques have improved, astronomers have been mesmerized by the star's protoplanetary disk, which contains several rings that could be indicative of baby planets being born.
Previous research has shown that there's likely a small exoplanet being born very close to the star, leading to speculation that it could be the birth place of an Earth-like exoplanet.
Now, astronomers using data from the Atacama Large Millimeter/submillimeter Array (ALMA), located high in the Atacama Desert in Chile, have added another layer of evidence that the prominent outer ring may well contain an "ice giant" exoplanet in the earliest stages of birth.
WATCH VIDEO: Exo-Uranus Found!
ALMA, which is an interferometer consisting of 66 radio antennae, can peer into the TW Hydrae system with astounding precision. During its studies of the star's dusty protoplanetary disk astronomers have been able to use it as a kind of protoplanetary "petri dish" owing to its close proximity to Earth (at a distance of only 175 light-years) and its fortuitous alignment. The disk is almost perfectly facing us, allowing astronomers to study planetary birth in action.
By studying two different wavelengths of radio emissions from the warm dust in the TW Hydrae disk, different sizes of dust particles can be studied. According to theoretical models of the protoplanetary disk, the dark rings embedded inside the bright disk should contain smaller dust particles than the rest of the disk if a baby exoplanet is present.
Sure enough, in research carried out by Takashi Tsukagoshi and his team at Ibaraki University, Japan, the most prominent gap, located at around 22 AU (22 times the Earth-sun distance) contains few large particles and is filled with smaller dust particles.
According to their models, should a planet be forming inside this dark ring, frictional processes are causing larger dust particles to be forced out of the ring as the baby exoplanet orbits the star. Smaller dust particles, however, remain unaffected and will preferentially fill the dark ring.
With this information, the researchers have been able to calculate the mass and probable composition of the planet. By their reckoning, this sun-like star is in the process of forming a baby ice giant exoplanet, much like the solar system's Uranus or Neptune.
"Combined with the orbit size and the brightness of TW Hydrae, the planet would be an icy giant planet," said Tsukagoshi.
By studying this very young star system, astronomers don't only have a ringside seat of the complexities of planetary formation, they are looking back in time when our sun was a youngster and how some of the biggest planets in our solar system likely formed. Fascinating.
GALLERY: The Most Mind-Blowing Space Spirals:
Meet R Sculptoris, a dying star that is shedding its outer layers of gas, generating a beautiful spiral of radio emissions. This amazing sight was captured by the Atacama Large Millimeter Array (ALMA) in the Chilean desert in 2012. Although rare, this kind of space spiral isn't unprecedented. In fact, there have been several space spirals seen in recent years that have excited, spooked, but, above all, awed onlookers -- here are a few of the most memorable.
The image on the right shows the actual observation of a very young star called MWC 758, which was spotted by the European Southern Observatory's Very Large Telescope (VLT). Each one of the dusty arms spiraling away from the central star are 10 billion miles long, or more than three times the diameter of Neptune's orbit. But what's driving this spiral? Using computer models (an example can be seen on the left), astronomers have realized that it is likely the gravitational force of a huge exoplanet (approximately 10 times the mass of Jupiter) that is stirring up the star's protoplanetary disk -- but the planet itself is hidden from view.
While technically not a spiral, this outstanding observation by ALMA has revealed the wonderfully well-defined tracks etched out by the presence of baby planets on orbit around TW Hydrae, a million year old star that is only 175 light-years from Earth. Though beautiful, this observation is most profound in that it possesses a proto-planet in a very Earth-like orbit very close to the host star. Yes, we're basically looking at a star system that resembles our solar system 4.5 billion years ago.
In 2010, the Hubble Space Telescope imaged a ghostly pinwheel spiral surrounding a binary star system called LL Pegasi. This bizarre cosmic phenomenon is caused by one of the stars dying, venting huge amounts of gas and dust into space. As the stars orbit one another every 800 years, the material expands into space like water being sprayed from a spinning garden sprinkler.
Probably the most striking example in recent years is that of the mysterious expanding shape that appeared over northern Norway on Dec. 9, 2009. Reflecting the early morning Arctic light, this vast spinning cloud expanded above the horizon, spraying a white spiral and blue tail. Conspiracy theories swarmed as soon as photographs and videos hit the media. Was it a portal to another dimension? Did a black hole just appear in our atmosphere? Was the restarted Large Hadron Collider responsible? As it turned out, the spiral was caused by a Russian missile after a failed test launch. The rocket, designed to carry nuclear warheads, spun out of control spewing fuel into the upper atmosphere, creating this beautiful spiral display.
What a kerfuffle WR 104 caused in 2008. The Wolf-Rayet star first gained attention when astronomers admired its spectacular spiral created by stellar winds colliding with the winds of its binary partner. But then we realized something. The Wolf-Rayet was dying, violently. And its violent death meant the massive star could collapse and generate one of the most powerful explosions in the cosmos: a gamma ray burst (or GRB). WR 104 is only 8,000 light-years from Earth, and the fact that we can see its full spiral means that we are looking down the barrel of this potentially damaging GRB. Naturally, many people were concerned that we could become GRB toast and in the eyes of the media, WR 104 was dubbed the "Death Star." Fortunately in 2009, Discovery News spoke with Wolf-Rayet star expert Grant Hill, of the Keck Observatory in Hawaii, who has other ideas about the deadly potential of WR 104.
UFO reports are often vague and include shaky video footage of a fuzzy light in the sky. However, when the Australian press announced the arrival of a bizarre spiraling light over the Gold Coast in June 2010, many eyewitnesses captured high quality video and photographs of the event. At the time, this "UFO" stayed true to its description; it was certainly an unidentified flying object. But it didn't stay unidentified for long; the sightings coincided with the maiden flight of SpaceX's Falcon 9 rocket. The spiraling effect was caused by a slight engineering fault causing the rocket to spin slowly, venting exhaust in a partial spiral.
We've all heard of supernovae, but what are "recurrent novae"? In the case of the binary star system RS Ophiuchi, a small but dense white dwarf star orbits with a large, puffy red giant that is shedding huge quantities of matter. This matter is blasted into space in the form of a strong stellar wind, forming a spiral. Interestingly, in this star system, the white dwarf captures some of the gas from its companion star, gradually accumulating it. Once the gas reaches a critical mass and temperature, a massive explosion occurs, wiping out the expanding spiral. The process then repeats every 20 years or so.
Let's shrink our spirals from the astrophysical to the geological (or, maybe, "areological"?) and look at these highly mysterious spirals on the surface of Mars. Yes, they're real, and no, they weren't created by intelligent Martians. Geologists know of these kinds of formations on Earth and they are caused by volcanic activity. Hundreds of these features, measuring up to 30 meters wide, have been spotted by NASA's Mars Reconnaissance Orbiter in Mars' Athabasca Valles. And, like their Earthly counterparts, geologists think they were formed by ancient lava flows when the Red Planet was volcanically active. Similar formations have been found in slow lava flows on Hawaii, for example.