For the first time ever, astronomers have directly imaged multiple planets orbiting a sunlike star.
The European Southern Observatory's Very Large Telescope (VLT) in Chile photographed two giant planets circling TYC 8998-760-1, a very young analogue of our own sun that lies about 300 light-years from Earth, a new study reports.
"This discovery is a snapshot of an environment that is very similar to our solar system, but at a much earlier stage of its evolution," study lead author Alexander Bohn, a doctoral student at Leiden University in the Netherlands, said in a statement.
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Before this historic cosmic portrait, only two multiplanet systems had ever been directly imaged, and neither of them features a sunlike star, study team members said. And snapping a photo of even a single exoplanet remains a rare achievement.
"Even though astronomers have indirectly detected thousands of planets in our galaxy, only a tiny fraction of these exoplanets have been directly imaged," study co-author Matthew Kenworthy, an associate professor at Leiden University, said in the same statement.
Bohn, Kenworthy and their colleagues studied the 17-million-year-old star TYC 8998-760-1 with the VLT's Spectro-Polarimetric High-contrast Exoplanet Research instrument, or SPHERE for short. SPHERE uses a device called a coronagraph to block a star's blinding light, allowing astronomers to see and study orbiting planets that would otherwise be lost in the glare.
The newly reported SPHERE imagery revealed two planets in the system, TYC 8998-760-1b and TYC 8998-760-1c. Astronomers already knew about TYC 8998-760-1b — a team led by Bohn announced its discovery late last year — but TYC 8998-760-1c is a newfound world.
The two planets are huge and farflung. TYC 8998-760-1b is about 14 times more massive than Jupiter and orbits at an average distance of 160 astronomical units (AU), and TYC 8998-760-1c is six times heftier than Jupiter and lies about 320 AU from the host star. (One AU is the average Earth-sun distance — about 93 million miles, or 150 million kilometers. For comparison: Jupiter and Saturn orbit our sun at just 5 AU and 10 AU, respectively.)
It's unclear whether the two worlds in TYC 8998-760-1 formed at their present locations or were pushed out there somehow. Further observations, including those made by huge future observatories such as the European Extremely Large Telescope (ELT), could help to solve that mystery, study team members said.
Other questions remain about the TYC 8998-760-1 system as well. For example, do the two gas giants have company? Might several rocky planets circle relatively close to the star, as they do in our solar system?
"The possibility that future instruments, such as those available on the ELT, will be able to detect even lower-mass planets around this star marks an important milestone in understanding multiplanet systems, with potential implications for the history of our own solar system," Bohn said.
The new study was published online today (July 22) in The Astrophysical Journal Letters.
Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
This is an important comment. Exoplanets that are large and orbiting far from their host stars, are very difficult and challenging to fit into the protoplanetary and accretion disk model(s ) in use. I ran a MS SQL query and found 70 such exoplanets documented now, most are direct imaging detection. Their semi-major axies > 50 AU. See http://exoplanet.eu/
My observation, at the present, it does not seem that TRAPPIST-1 seven exoplanets can be confirmed as having an earth like atmosphere and some may not have any atmosphere, note *(if present)* in the report.
Given the sizes and distances in comparison to our system I would not expect to be able to view the inner planets (if any). The CG simulation shows just how far outside the orbit of Pluto these planets would exist in our system
Our habitable zone only extends out approx. 1.4AU. Pluto is approx. 39.5AU. These planets are 4x and 8x more distant from it's star than Pluto is from our Sun.
6 of 7 are as close or closer than Earth is to our Sun when comparing the TRAPPIST-1 exoplanet system to our solar system planet configuration.
If, however, the outer planets were captured, then inner planets are certainly possible, but serious stellar interactions will also limit planets that are beyond, say, Jupiter or Saturn due to disruption by the passing star(s).
This and other things puts the upper limit on the number our Sun had for neighbors to about 3000 stars. The IMF (Initial Mass Function) demonstrates that, likely, a few of these would have been massive stars, which form early and brightly, perhaps illuminating our disk if one or more were relatively close.
We have other reports of multiple giant planets, these are not imaged (primary transit and radial velocity detections). WASP-148 (example, http://exoplanet.eu/catalog/wasp-148_b/) and Kepler-88 system, (http://exoplanet.eu/catalog/kepler-88_b/ as an example). These are more like hot jupiters or warm Neptunes, orbiting very close to their host stars with host star masses near one solar mass too. Kepler-88 host star is considered to be about 2.45E+9 years old . Kepler-88 and WASP-148 multiple giant exoplanet systems all orbit their host stars much closer than 1 AU compared to the TYC 8998-760-1 system imaged.
Consider a collapsing gas cloud and protoplanetary accretion disk model(s). We have our solar system configuration with a one solar mass star and a very habitable Earth. Now we see multiple giant exoplanets imaged around a star about one solar mass much farther away, and other multiple giant planets detected, orbiting around their host stars much closer than Mercury's orbit in our solar system. Those collapsing gas clouds work wonders in planet formation, considering the exoplanet varieties reported now :)
Here is another exoplanet site I use, https://exoplanetarchive.ipac.caltech.edu/index.html, 4183 confirmed. This site reports 706 host stars with multiple exoplanets. The host stars with 6-8 exoplanets orbiting them are: pl_hostname, HD 10180, HD 219134, HD 34445, Kepler-11, Kepler-20, Kepler-80, KOI-351, TRAPPIST-1.
Both sites I use and load into my home MS ACCESS database for MS SQL queries and reports. There is plenty of exoplanets now for deep dives and much fun studying---Rod