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Circular Orbits Identified For Small Exoplanets

June 2, 2015 1 comment

Artist's conception.  Image courtesy of NASA

Artist’s conception. Image courtesy of NASA

Viewed from above, our solar system’s planetary orbits around the sun resemble rings around a bulls-eye. Each planet, including Earth, keeps to a roughly circular path, always maintaining the same distance from the sun.

For decades, astronomers have wondered whether the solar system’s circular orbits might be a rarity in our universe. Now a new analysis suggests that such orbital regularity is instead the norm, at least for systems with planets as small as Earth.

In a paper published in the Astrophysical Journal, researchers from MIT and Aarhus University in Denmark report that 74 exoplanets, located hundreds of light-years away, orbit their respective stars in circular patterns, much like the planets of our solar system.

These 74 exoplanets, which orbit 28 stars, are about the size of Earth, and their circular trajectories stand in stark contrast to those of more massive exoplanets, some of which come extremely close to their stars before hurtling far out in highly eccentric, elongated orbits.

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Weather On Alien Worlds Uncovered: Cloudy Mornings & Hot Afternoons

May 12, 2015 1 comment

TORONTO, May 12, 2015 — We may complain a lot about the weather on earth but perhaps we are much better off here than on some alien worlds, where the daily forecast is cloudy, overcast skies in the morning and scorching heat in the afternoon.

A team of international astronomers including York University scientist Professor Ray Jayawardhana have uncovered evidence of daily weather cycles on six extra-solar planets using sensitive observations from the Kepler space telescope.

“Despite the discovery of thousands of extra-solar planets, what these far-off worlds look like is still shrouded in mystery,” says lead author Lisa Esteves, graduate student at the University of Toronto.

In their paper entitled “Changing Phases of Alien Worlds: Probing Atmospheres of Kepler Planets with High-Precision Photometry” published today in the Astrophysical Journal, the team analyzed all 14 Kepler planets known to exhibit phase variations, and found indications of cloudy mornings on four and hot, clear afternoons on two others.

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New Exoplanet Too Big For Its Stars


An artist's impression of HATS-6. Credit ANU

An artist’s impression of HATS-6. Credit ANU

The Australian discovery of a strange exoplanet orbiting a small cool star 500 light years away is challenging ideas about how planets form.

“We have found a small star, with a giant planet the size of Jupiter, orbiting very closely,” said researcher George Zhou from the Research School of Astrophysics and Astronomy.

“It must have formed further out and migrated in, but our theories can’t explain how this happened.”

In the past two decades more than 1,800 extrasolar planets (or exoplanets) have been discovered outside our solar system orbiting around other stars.

The host star of the latest exoplanet, HATS-6, is classed as an M-dwarf, which is one of the most numerous types of stars in galaxy. Although they are common, M-dwarf stars are not well understood. Because they are cool they are also dim, making them difficult to study.

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Astronomers Discover Three Super-Earths Orbiting Nearby Star


Artist’s impression. Art by Karen Teramura & BJ Fulton, UH IfA.

Artist’s impression. Art by Karen Teramura & BJ Fulton, UH IfA.

Astronomers have discovered a planetary system orbiting a star only 54 light-years away with the Automated Planet Finder (APF) at Lick Observatory and ground-based telescopes in Hawaii and Arizona.

The team discovered the planets by detecting a wobble of the star HD 7924, a result of the gravitational pull of the planets orbiting around it. All three planets orbit the star at a distance closer than Mercury orbits the sun, completing their orbits in just 5, 15, and 24 days.

The APF facility at Lick Observatory offers a way for astronomers to speed up the exoplanet search. The fully-robotic telescope searches for planets every clear night of the year, so planets and their orbits can be discovered and traced quickly.

“The APF is great for two reasons. One, it has the superb Levy spectrometer. Two, it is a modern computer controlled telescope so we can automate it. This combination means that we can observe stars night and night out to look for the wobble,” said Bradford Holden, an Associate Research Astronomer for UC Observatories (UCO) who helped to make the telescope robotic.

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Hubble Gets Best View of A Circumstellar Debris Disk Distorted By A Planet

February 19, 2015 Leave a comment

Credit: NASA, ESA, and D. Apai and G. Schneider (University of Arizona)

Credit: NASA, ESA, and D. Apai and G. Schneider (University of Arizona)

Astronomers have used NASA’s Hubble Space Telescope to take the most detailed picture to date of a large, edge-on, gas-and-dust disk encircling the 20-million-year-old star Beta Pictoris.

Beta Pictoris remains the only directly imaged debris disk that has a giant planet (discovered in 2009). Because the orbital period is comparatively short (estimated to be between 18 and 22 years), astronomers can see large motion in just a few years. This allows scientists to study how the Beta Pictoris disk is distorted by the presence of a massive planet embedded within the disk.

The new visible-light Hubble image traces the disk in closer to the star to within about 650 million miles of the star (which is inside the radius of Saturn’s orbit about the Sun).

“Some computer simulations predicted a complicated structure for the inner disk due to the gravitational pull by the short-period giant planet. The new images reveal the inner disk and confirm the predicted structures. This finding validates models, which will help us to deduce the presence of other exoplanets in other disks,” said Daniel Apai of the University of Arizona. The gas-giant planet in the Beta Pictoris system was directly imaged in infrared light by the European Southern Observatory’s Very Large Telescope six years ago.

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The Gemini Planet Imager Produces Stunning Observations In Its First Year

January 8, 2015 Leave a comment

Image credit: Christian Marois (NRC Canada), Patrick Ingraham (Stanford University) and the GPI Team

Image credit: Christian Marois (NRC Canada), Patrick Ingraham (Stanford University) and the GPI Team

Stunning exoplanet images and spectra from the first year of science operations with the Gemini Planet Imager (GPI) were featured today in a press conference at the 225th meeting of the American Astronomical Society (AAS) in Seattle, Washington. The Gemini Planet Imager GPI is an advanced instrument designed to observe the environments close to bright stars to detect and study Jupiter-like exoplanets (planets around other stars) and see protostellar material (disk, rings) that might be lurking next to the star.

Marshall Perrin (Space Telescope Science Institute), one of the instrument’s team leaders, presented a pair of recent and promising results at the press conference. He revealed some of the most detailed images and spectra ever of the multiple planet system HR 8799. His presentation also included never-seen details in the dusty ring of the young star HR 4796A. “GPI’s advanced imaging capabilities have delivered exquisite images and data,” said Perrin. “These improved views are helping us piece together what’s going on around these stars, yet also posing many new questions.”

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UH Astronomer, Keck Observatory Confirm First Kepler K2 Exoplanet Discovery

December 19, 2014 Leave a comment

Artist’s conception. Artwork courtesy CfA

Artist’s conception. Artwork courtesy CfA

Despite a malfunction that ended its primary mission in May 2013, NASA’s Kepler spacecraft has discovered a new super-Earth using data collected during its “second life,” known as the K2 mission.

University of Hawaii astronomer Christoph Baranec supplied confirming data with his Robo-AO instrument mounted on the Palomar 1.5-meter telescope, and former UH graduate student Brendan Bowler, now a Joint Center for Planetary Astronomy postdoctoral fellow at Caltech, provided additional confirming observations using the Keck II adaptive optics system on Maunakea.

The Kepler spacecraft detects planets by looking for planets that transit, or cross in front of, their star as seen from the vantage of Earth. During the transit, the star’s light dims slightly. The smaller the planet, the weaker the dimming, so brightness measurements must be exquisitely precise. To enable that precision, the spacecraft must maintain a steady pointing.

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