Planetary formation is a complicated, multilayered process. Even with the influx of data on exoplanets, there are still only two known planets that are not yet fully formed. Known as PDS 70b and PDS 70c, the two planets, which were originally found by the Very Large Telescope, are some of the best objects we have to flesh out our planetary formation models. And now, one of them has been confirmed to have a moon-forming disk around it.Continue reading “Incredible! Astronomers see a Moon-Forming Disk Around a Newly Forming Planet”
Stunning First Ever Photograph of a Newly Forming Planet
For decades, the most widely-accepted view of how our Solar System formed has been the Nebular Hypothesis. According to this theory, the Sun, the planets, and all other objects in the Solar System formed from nebulous material billions of years ago. This dust experienced a gravitational collapse at the center, forming our Sun, while the rest of the material formed a circumstellar debris ring that coalesced to form the planets.
Thanks to the development of modern telescopes, astronomers have been able to probe other star systems to test this hypothesis. Unfortunately, in most cases, astronomers have only been able to observe debris rings around stars with hints of planets in formation. It was only recently that a team of European astronomers were able to capture an image of a newborn planet, thus demonstrating that debris rings are indeed the birthplace of planets.
The team’s research appeared in two papers that were recently published in Astronomy & Astrophysics, titled “Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70” and “Orbital and atmospheric characterization of the planet within the gap of the PDS 70 transition disk.” The team behind both studies included member from the Max Planck Institute for Astronomy (MPIA) as well as multiple observatories and universities.
For the sake of their studies, the teams selected PDS 70b, a planet that was discovered at a distance of 22 Astronomical Units (AUs) from its host star and which was believed to be a newly-formed body. In the first study – which was led by Miriam Keppler of the Max Planck Institute for Astronomy – the team indicated how they studied the protoplanetary disk around the star PDS 70.
PDS 70 is a low-mass T Tauri star located in the constellation Centaurus, approximately 370 light-years from Earth. This study was performed using archival images in the near-infrared band taken by the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) instrument on the ESO’s Very Large Telescope (VLT) and the Near-Infrared Coronagraphic Imager on the Gemini South Telescope.
Using these instruments, the team made the first robust detection of a young planet (PDS 70b) orbiting within a gap in its star’s protoplanetary disc and located roughly three billion km (1.86 billion mi) from its central star – roughly the same distance between Uranus and the Sun. In the second study, led by Andre Muller (also from the MPIA) the team describes how they used the SPHERE instrument to measure the brightness of the planet at different wavelengths.
From this, they were able to determine that PDS 70b is a gas giant that has about nine Jupiter masses and a surface temperature of about 1000 °C (1832 °F), making it a particularly “Hot Super-Jupiter”. The planet must be younger than its host star, and is probably still growing. The data also indicated that the planet is surrounded by clouds that alter the radiation emitted by the planetary core and its atmosphere.
Thanks to the advanced instruments used, the team was also able to acquire an image of the planet and its system. As you can see from the image (posted at top) and the video below, the planet is visible as a bright point to the right of the blackened center of the image. This dark region is due to a corongraph, which blocks the light from the star so the team could detect the much-fainter companion.
As Miriam Keppler, a postdoctoral student at the MPIA, explained in a recent ESO press statement:
“These discs around young stars are the birthplaces of planets, but so far only a handful of observations have detected hints of baby planets in them. The problem is that until now, most of these planet candidates could just have been features in the disc.”
In addition to spotting the young planet, the research teams also noted that it has sculpted the protoplanetary disc orbiting the star. Essentially, the planet’s orbit has traced a giant hole in the center of the disc after accumulating material from it. This means that PDS 70 b is still located in the vicinity of its birth place, is likely to still be accumulating material and will continue to grow and change.
For decades, astronomers have been aware of these gaps in the protoplanetary disc and speculated that they were produced by a planet. Now, they finally have the evidence to support this theory. As André Müller explained:
“Keppler’s results give us a new window onto the complex and poorly-understood early stages of planetary evolution. We needed to observe a planet in a young star’s disc to really understand the processes behind planet formation.“
These studies will be a boon to astronomers, especially when it comes to theoretical models of planet formation and evolution. By determining the planet’s atmospheric and physical properties, the astronomers have been able to test key aspects of the Nebular Hypothesis. The discovery of this young, dust-shrouded planet would not have been were if not for the capabilities of ESO’s SPHERE instrument.
This instrument studies exoplanets and discs around nearby stars using a technique known as high-contrast imaging, but also relies on advanced strategies and data processing techniques. In addition to blocking the light from a star with a coronagraph, SPHERE is able to filter out the signals of faint planetary companions around bright young stars at multiple wavelengths and epochs.
As Prof. Thomas Henning – the director at MPIA, the German co-investigator of the SPHERE instrument, and a senior author on the two studies – stated in a recent MPIA press release:
“After ten years of developing new powerful astronomical instruments such as SPHERE, this discovery shows us that we are finally able to find and study planets at the time of their formation. That is the fulfillment of a long-cherished dream.”
Future observations of this system will also allow astronomers to test other aspects of planet formation models and to learn about the early history of planetary systems. This data will also go a long way towards determining how our own Solar System formed and evolved during its early history.
Further Reading: ESO, MPIA, Astronomy & Astrophysics, Astronomy & Astrophysics (2)
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Here There Be Planets: Stellar Disk Gap May Reveal Newborn Worlds
HiCIAO near-infrared image of the protoplanetary disk around PDS 70. The circular mask hides the star itself, as well as a smaller internal disk structure. (Credit: NAOJ)
Over the past couple of decades astronomers have figured out several methods for finding planets around other stars in our galaxy. Some have revealed their presence by the slight “wobble” they impart to their host stars as they orbit, while others have been discovered as they pass in front of their stars from our perspective, briefly dimming the light we see.
Now, some astronomers think they may have identified the presence of multiple planets, based on a large gap found in the disk of gas and dust surrounding a Sun-like star 460 light-years from Earth.
Using the High Contrast Instrument for the Subaru Next Generation Adaptive Optics (HiCIAO) mounted on Japan’s 8.2-meter optical-infrared Subaru telescope atop Mauna Kea in Hawaii, an international team of astronomers targeted PDS 70, a young star (10 million years old) about the same mass as the Sun located 460 light-years away in the constellation Centaurus.
The near-infrared observations made by HiCIAO reveal a protoplanetary disk surrounding PDS 70. This disk is composed of gas and dust and extends billions of miles out from the star. Quite literally the stuff that planets are made of, it’s a disk much like this that our solar system likely started out as over 4.6 billion years ago.
“Thanks to the powerful combination of the Subaru Telescope and HiCIAO, we are able to probe the disks around Sun-like stars. PDS 70 shows how our solar system may have looked in its infancy. I want to continue this kind of research to understand the history of planetary formation.”
– Team Leader Jun Hashimoto (NAOJ)
Within PDS 70’s disk are several large gaps positioned at varying distances from the star itself, appearing as dark regions in the near-infrared data. These gaps — especially the largest, located about 70 AU from the star — are thought to be the result of newly-formed planets having cleared the surrounding space of dust and smaller material. It’s also believed that multiple planets may be present since, according to the team, “no single planet, regardless of how heavy or efficient it is in its formation, is sufficient to create such a giant gap.”
In addition to the large disk structure and outer gap, PDS 70 also has a smaller disk located only 1 AU away. (This disk is obscured by the HiCIAO mask in the image above.)
Further observations will be needed to locate any actual exoplanets directly, since the light from the star and scattered light within the disk makes it difficult — if not impossible with current technology — to detect the incredibly faint light reflected by planets.
Still, it’s fascinating to come across what may very well be a solar system in its infancy, giving us a glimpse back in time to our own formation.
“Direct imaging of planets in the process of forming in protoplanetary disks would be ideal so that we can learn when, where, and how planets form,” said team leader Ruobing Dong of Princeton University.
Read more on the NAOJ website for the Subaru Observatory here.
The goal of the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) Project is to study the disks around less massive stars like the Sun.
Inset image: Artist’s rendition of PDS 70 and its two protoplanetary disks (NAOJ)