Space
Sat Mar 21, 2020 2:3
Odd Orbits of 'Tatooine' Planetary Disks
TEHRAN (FNA)- Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found striking orbital geometries in protoplanetary disks around binary stars. While disks orbiting the most compact binary star systems share very nearly the same plane, disks encircling wide binaries have orbital planes that are severely tilted. These systems can teach us about planet formation in complex environments.

In the last two decades, thousands of planets have been found orbiting stars other than our Sun. Some of these planets orbit two stars, just like Luke Skywalker's home Tatooine. Planets are born in protoplanetary disks -- we now have wonderful observations of these thanks to ALMA -- but most of the disks studied so far orbit single stars. 'Tatooine' exoplanets form in disks around binary stars, so-called circumbinary disks.

Studying the birthplaces of 'Tatooine' planets provides a unique opportunity to learn about how planets form in different environments. Astronomers already know that the orbits of binary stars can warp and tilt the disk around them, resulting in a circumbinary disk misaligned relative to the orbital plane of its host stars. For example, in a 2019 study led by Grant Kennedy of the University of Warwick, UK, ALMA found a striking circumbinary disk in a polar configuration.

"With our study, we wanted to learn more about the typical geometries of circumbinary disks," said astronomer Ian Czekala of the University of California at Berkeley. Czekala and his team used ALMA data to determine the degree of alignment of nineteen protoplanetary disks around binary stars. "The high resolution ALMA data was critical for studying some of the smallest and faintest circumbinary disks yet," said Czekala.

The astronomers compared the ALMA data of the circumbinary disks with the dozen 'Tatooine' planets that have been found with the Kepler space telescope. To their surprise, the team found that the degree to which binary stars and their circumbinary disks are misaligned is strongly dependent on the orbital period of the host stars. The shorter the orbital period of the binary star, the more likely it is to host a disk in line with its orbit. However, binaries with periods longer than a month typically host misaligned disks.

"We see a clear overlap between the small disks, orbiting compact binaries, and the circumbinary planets found with the Kepler mission," Czekala said. Because the primary Kepler mission lasted 4 years, astronomers were only able to discover planets around binary stars that orbit each other in fewer than 40 days. And all of these planets were aligned with their host star orbits. A lingering mystery was whether there might be many misaligned planets that Kepler would have a hard time finding. "With our study, we now know that there likely isn't a large population of misaligned planets that Kepler missed, since circumbinary disks around tight binary stars are also typically aligned with their stellar hosts," added Czekala.

Still, based on this finding, the astronomers conclude that misaligned planets around wide binary stars should be out there and that it would be an exciting population to search for with other exoplanet-finding methods like direct imaging and microlensing. (NASA's Kepler mission used the transit method, which is one of the ways to find a planet.)

Czekala now wants to find out why there is such a strong correlation between disk (mis)alignment and the binary star orbital period. "We want to use existing and coming facilities like ALMA and the next generation Very Large Array to study disk structures at exquisite levels of precision," he said, "and try to understand how warped or tilted disks affect the planet formation environment and how this might influence the population of planets that form within these disks."

"This research is a great example of how new discoveries build on previous observations," said Joe Pesce, National Science Foundation Program Officer for NRAO and ALMA. "Discerning trends in the circumbinary disk population was only made possible by building on the foundation of archival observational programs undertaken by the ALMA community in previous cycles."

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

 

 

 

Bottom top
Tehran, Baku Discuss Expansion of Economic Ties

TEHRAN (FNA)- High-ranking Iranian and Azeri officials conferred on avenues to bolster relations and cooperation between the two countries, specially in trade and economy.
Saad Hariri Becomes New Prime Minister of Lebanon

TEHRAN (FNA)- Saad Hariri, who had previously twice assumed the position of the head of Lebanon's council of ministers, was re-elected on Thursday as the country’s new Prime Minister in the wake of Mustapha Adib's resignation in late September, the office of President Michel Aoun said.
LA Police Chief Predicts Highest Number of Homicides Since 2009

TEHRAN (FNA)- Los Angeles's police chief stated Tuesday that the city has recorded 266 homicides so far this year, and predicted that the count will pass 300 before the end of the year.
Report: White House Mulls Slashing Federal Funds to Cities Labeled 'Anarchist Jurisdictions'

TEHRAN (FNA)- Donald Trump administration officials have reportedly considered cutting millions of dollars for COVID-19 and other health programs in cities led by Democratic lawmakers that the Department of Justice has said "permit anarchy".
Mayor Accuses PM of ‘Blatant Lie’ over Transport for London

TEHRAN (FNA)- London’s mayor Sadiq Khan accused Boris Johnson of telling a “blatant lie” to the House of Commons after the prime minister accused him of bankrupting Transport for London.
UK Government Borrowing Soars to Record High During COVID Pandemic

TEHRAN (FNA)- UK government borrowing soared to a record high in the first six months of the financial year as the extra spending needed to tackle the COVID-19 pandemic pushed the public deficit further into the red.
Iran Stresses Air Defense Force's Capability to Confront Electro-Optic-Guided Targets

TEHRAN (FNA)- Lieutenant Commander of Khatam al-Anbia Air Defense Base Brigadier General Qader Rahimzadeh announced on Thursday the Iranian Air Defense Force's capability to trace and destroy electro-optic-guided targets.
Report: US Ice Officers 'Used Torture to Make Africans Sign Own Deportation Orders'

TEHRAN (FNA)- US immigration officers allegedly tortured Cameroonian asylum seekers to force them to sign their own deportation orders, in what lawyers and activists describe as a brutal scramble to fly African migrants out of the country in the run-up to the elections.
Iran Reports over 5,000 New Coronavirus Patients

TEHRAN (FNA)- The Iranian health ministry announced on Thursday 5,471 new cases of coronavirus infection have been reported across the country during the past 24 hours, adding that a total number of 550,757 patients have been identified since the first case was identified last February.
Poll: Biden's National Lead Narrows to 4 Points

TEHRAN (FNA)- Democratic nominee Joe Biden's lead over President Donald Trump narrowed to 4 percentage points in a new Hill-HarrisX national poll.
White House Leans on Pentagon to Fulfill Trump’s Afghanistan Pledge

TEHRAN (FNA)- The White House is turning up the pressure on the Pentagon to carry out President Donald Trump’s directive of a further withdrawal of US troops from Afghanistan, as the commander in chief looks to deliver on a campaign pledge ahead of next month’s election.
Two Women Stabbed at Eiffel Tower in Apparent Racist Attack

TEHRAN (FNA)- French police launched an investigation after two women were stabbed near the Eiffel Tower in an apparent racist incident.
Kremlin Rejects All US Election Meddling Accusations Against Russia

TEHRAN (FNA)- All accusations against Russia of trying to meddle in the electoral processes in the United States are totally unfounded, Kremlin Spokesman Dmitry Peskov told reporters on Thursday.
Iran's Indigenized Phased-Array Radars Trace Hypothetical Enemy Flying Targets in Wargames

TEHRAN (FNA)- The Iranian Army and the Islamic Revolution Guards Corps (IRGC)'s home-made phased-array radar systems detected and traced aggressive hostile flying objects during their joint aerial drills on Thursday.
Greece, Egypt, Cyprus Jointly Condemn Turkey’s ‘Aggression’ in Eastern Mediterranean

TEHRAN (FNA)- Turkey’s natural gas exploration and military activities in the disputed waters of the Eastern Mediterranean have been roundly condemned by its neighbors, who also criticized the recent reopening of a beach area in North Cyprus.