Illuminating a Giant: Revolutionizing Planet Searches With Direct Imaging and Astrometry

Category Space

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In a new study recently published in Science, researchers combined different search techniques to discover the giant planet, HIP99770b. This planet is too hot for life, but it provides a scaled-up version of the Kuiper Belt in our solar system. The detection technique discovered this new planet by using both direct imaging and astrometry methods.

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Finding life on other planets might well be the holy grail of astronomy, but the hunt for suitable host planets that can sustain life is a resource-intensive task. Imaging Planets Is No Small Feat To satisfy our curiosity about our place in the universe, astronomers have developed many techniques to search for planets orbiting other stars. Perhaps the simplest of these is called direct imaging. But it’s not easy .

HIP99770b orbits HIP99770 and is 1,000℃, making it unable to sustain life.

Direct imaging involves attaching a powerful camera to a large telescope and trying to detect light emitted, or reflected, from a planet. Stars are bright, and planets are dim, so it’s akin to searching for fireflies dancing around a spotlight. It’s no surprise only about 20 planets have been found with this technique to date. Yet direct imaging is of great value. It helps shed light on a planet’s atmospheric properties, such as its temperature and composition, in a way other detection techniques can’t .

The new detection technique analyzed 25 years' worth of positional data with both direct imaging and astrometry.

--- HIP99770b: A New Gas Giant --- Our direct imaging of a new planet, named HIP99770b, reveals a hot, giant and moderately cloudy planet. It orbits its star at a distance that falls somewhere between the orbital distances of Saturn and Uranus around our sun. With about 15 times the mass of Jupiter, HIP99770b is a real giant. However, it’s also more than 1,000℃, so it’s not a good prospect for a habitable world .

HIP99770 is a massive star almost twice the mass of our sun.

What the HIP99770 system does offer is an analogy to our own solar system. It has a cold "debris disk" of ice and rock far out from the star, akin to a scaled-up version of the Kuiper Belt in our solar system. The main difference is that the HIP99770 system is dominated by one high-mass planet, rather than several smaller ones. --- Searching With the Light On --- We reached our findings by first detecting hints of a planet via indirect detection methods .

Gaia’s predecessor, Hipparcos measured the positions of nearly one billion stars since 2014.

We noticed the star was wobbling in space, which hinted at the presence of a planet in the vicinity with a large gravitational pull. This motivated our direct imaging efforts; we were no longer searching in the dark. The extra data came from the European Space Agency’s Gaia spacecraft, which has been measuring the positions of nearly one billion stars since 2014. Gaia is sensitive enough to detect tiny variations of a star’s motion through space, such as those caused by planets .

Direct imaging takes a powerful camera and attaches it to a large telescope to detect light emitted or reflected from a planet.

We also supplemented these data with measurements from Gaia’s predecessor, Hipparcos. In total, we had 25 years’ worth of "astrometric" (positional) data to work with. Previously, researchers have used indirect methods to guide imaging that has discovered companion stars, but not planets. It’s not their fault: massive stars such as HIP99770—which is almost twice the mass of our sun—are reluctant to give up their secrets .

HIP99770 system is dominated by one high-mass planet, rather than several smaller ones.

Otherwise-successful search techniques can rarely reach the levels of precision required to detect planets around such massive stars. Our detection, which used both direct imaging and astrometry, demonstrates a more efficient search strategy.

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