This week, it’s been a feast of exoplanet science at Goddard, which hosted the Signposts of Planets meeting Oct. 18-20. The three-day conference gathered an international crowd of observers, computer modelers, and instrument builders to explore the relationship between exoplanets and the circumstellar disks in which they form.
Circumstellar simply means “disks of gas and dust around a star or stars.” Astronomers have discovered some 687 planets around other stars, but ironically they rarely are able to “see” one directly. What the Hubble telescope and other instruments see are dusty disks.
Circumstellar disks are the “signposts of planets” referenced by the name of the conference. Want to find planets? Look for dusty disks.
Here is Goddard astrophysicist and Signpost meeting organizer Marc Kuchner explaining the lowdown on circumstellar disks, back when we only knew of about 400 extrasolar worlds:
The conference produced some show-stoppers in terms of new discoveries announced. Four were the subject of press releases:
At the meeting, Goddard astronomer Carol Grady announced the discovery of a type of exoplanet telltale predicted but never actually imaged before. In some circumstellar disks, the tug of a planet’s gravity can create subtle spiral features in the gas and dust. That is good news, because it means that disks with spirals could lead astronomers to planets.
“What we’re finding is that once these systems reach ages of a few million years, their disks begin to show a wealth of structure — rings, divots, gaps and now spiral features,” said John Wisniewski, a collaborator at the University of Washington in Seattle. “Many of these structures could be caused by planets within the disks.”
The newly imaged disk surrounds SAO 206462, a star located about 456 light-years away in the constellation Lupus.
Also at the conference, astronomer Adam Kraus explained how he used the mammoth Keck telescopes on Mauna Kea in Hawaii to image an infant planet. “LkCa 15 b is the youngest planet ever found, about 5 times younger than the previous record holder,” said Kraus, who is based at the University of Hawaii’s Institute for Astronomy.
Kraus did the work using a technique called interferometry, which allows a telescope to achieve the detail-resolving power equivalent to that of a much larger telescope.
In another report at the Signpost meeting, astronomer Kevin Luhman of Penn State University described his observations of a star with a cool planet-like companion. The object, a gaseous not-quite-a-star called a brown dwarf, has an outer temperature described as comparable to “a hot summer day in Arizona.”
“Its mass is about the same as many of the known extra-solar planets — about six to nine times the mass of Jupiter — but in other ways it is more like a star. Essentially, what we have found is a very small star with an atmospheric temperature about cool as the Earth’s.”
OK, not quite a planet — but not quite a star either. Brown dwarfs lie in between. But they lie along a spectrum of objects that exoplanet researchers study.
Ever since brown dwarfs first were discovered in 1995, astronomers have been trying to find new record holders for the coldest brown dwarfs because these objects are valuable as laboratories for studying the atmospheres of planets with Earth-like temperatures outside our solar system.
And last but not least, comet storms!
NASA’s Spitzer Space Telescope has detected signs of icy bodies raining down in an alien solar system. The downpour resembles our own solar system several billion years ago during a period known as the “Late Heavy Bombardment,” which may have brought water and other life-forming ingredients to Earth.
Carey Lisse, senior research scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland., announced the finding at the Signposts conference. The research will be published in the Astrophysical Journal.
OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.