Calling someone a big baby is an insult, but when it comes to new planets, go ahead — no hard feelings!
Astronomers have captured a spectacular photo of such a planet in the act of forming from a disk of dust and gas around the young dwarf star PDS 70. By using the SPHERE instrument on the European Southern Observatory’s Very Large Telescope (VLT) — a powerful planet-hunting tool — they teased out this otherworldly gas giant named PDS 70b with a mass a few times that of Jupiter.
The SPHERE instrument also enabled the team to measure the brightness of the planet at different wavelengths, which allowed them to determine that it’s a cloudy place. The planet is roughly 1.9 billion miles (3 billion km) from its central star, about the same distance that separates Uranus from our sun. You would think that would make it a cold, icy place, but the new planet’s surface temperature hovers around around 1,800 F (1000°C), making it about twice as hot as Mercury and Venus, the hottest planets in our solar system.
Travel 370 light years as you zoom in on the orange dwarf PDS 70 and its planet
The host star, PDS 70, is located in the southern constellation Centaurus 370 light years from Earth. At magnitude 12, it’s even bright enough to see in a 4-inch telescope. Just the star — not the planet. While the sun is G-type pale yellow star, PDS 70 is K-type orange star about ⅘ as massive as the sun and 1.4 times its diameter.
Given that the star is some 2,000 degrees cooler than our sun, we can surmise that the planet’s high surface temperature may have something to do with its high mass (three Jupiter’s worth) and heavy cloud cover. Massive objects, especially young ones, radiate heat as they continue to contract through gravity. That’s my hunch anyway.
The dark circle in the center of the photo is from a coronagraph, a mask which blocks the blinding light of the central star and allows astronomers to see the fainter disk and planetary companion. Without it we’d see zip!
“These disks around young stars are the birthplaces of planets, but so far only a handful of observations have detected hints of baby planets in them,” explains Miriam Keppler, who lead the team behind the discovery of PDS 70’s still-forming planet. “The problem is that until now, most of these planet candidates could just have been features in the disk.”
Looking at the photo, you can see more going on than just the planet. PDS 70b planetary companion has sculpted a transition disk — a protoplanetary disc with a giant “hole” in the center. These inner gaps have been known about for decades and suspected to be caused by orbiting planets. Now, a perpetrator has finally been exposed!
All the photos of extraterrestrial planets so far only show the planet a bright spot much like stars appear as bright points. That’s because the planets are too far and too small to show as disks in even the largest instruments, and that includes the upcoming James Webb Space Telescope due to launch in 2021. It’s estimated that to image an actual disk, an array of optical telescopes spanning 12.4 miles (20 km) across would be required. To distinguish continents and oceans, we’d need to expand the array to 43 miles (70 km). Read more about the future of exoplanet research here.