Hubble Telescope Observations Leave Astronomers Puzzled with Mysterious Shadows in Space

NASA’s Hubble Space Telescope may have detected the formation of two new planets in the TW Hydrae system, according to recent observations stored in the telescope’s MAST archive.

Astronomers had previously identified a shadow moving across the system’s gas-and-dust disk in 2017, which was caused by an inner disk tilted relative to the larger outer disk. This time, a second shadow has emerged, possibly from yet another disk nestled inside the system. Both shadows are thought to be evidence of a pair of planets under construction.

Hubble Telescope Observes New Planets in the Making Through Shadow Puppets

TW Hydrae is a young star less than 10 million years old, located about 200 light-years away from Earth. The system’s nearly face-on orientation makes it an ideal target for observing the formation of planets.

Peter Plavchan, a physics and astronomy professor at George Mason University, worked with the team that made the latest observations. He studied the possible role of a forming planet in creating the disk structures and shadows seen in the TW Hydrae system.

The second shadow was discovered in June 2021 as part of a multi-year program aimed at tracking the shadows in circumstellar disks.

John Debes of the European Space Agency at the Space Telescope Science Institute in Baltimore, Maryland, compared the latest TW Hydrae observations to those made several years ago.

While the shadows are not caused directly by planets, they provide important clues about planet formation and may help astronomers better understand how our own solar system evolved over 4.6 billion years ago.

They “found out that the shadow had done something completely different,” points out lead author John Debes.

“When I first looked at the data, I thought something had gone wrong with the observation because it wasn’t what I was expecting. I was flummoxed at first, and all my collaborators were like: what is going on? We really had to scratch our heads and it took us a while to actually figure out an explanation.”

The findings of the study were published in The Astrophysical Journal.

“We haven’t found any direct evidence for a planet at this time,” adds Dr. Peter Plavchan, “but can rule out planets more massive than Jupiter from precisely monitoring the position of the star as a function of time.”

According to the team, there are two misaligned disks casting shadows, which is the best solution they have identified. These disks were so close to each other during earlier observations that they were missed. However, over time, they have separated and split into two shadows.

Debes says they have “never really seen this before on a protoplanetary disk. It makes the system much more complex than we originally thought.”

The team believes that the misaligned disks are likely caused by the gravitational pull of two planets in slightly different orbital planes, which is the simplest explanation. Hubble is working to piece together a holistic view of the system’s architecture. The disks may be acting as proxies for planets that are orbiting each other closely, like two vinyl phonograph records spinning at slightly different speeds. Although their labels may match up at times, one of them eventually gets ahead of the other.

“It does suggest that the two planets have to be fairly close to each other. If one was moving much faster than the other, this would have been noticed in earlier observations. It’s like two race cars that are close to each other, but one slowly overtakes and laps the other,” explains Debes.

The possible worlds are in an area that is about as far from our Sun as Jupiter is. Additionally, the shadows circle the star once every 15 years, which is the predicted orbital period given their proximity to the star.

Additionally, the angle between these two inner disks and the plane of the outer disk is between five and seven degrees. This is about the same as the spread of tilts of orbits in our solar system.

“This is right in line with typical solar system style architecture,” according to Debes.

The findings suggest that a larger outer disk, which casts shadows, could extend beyond the Kuiper Belt by several times its radius. Interestingly, this disk contains a gap at twice the average distance from the Sun to Pluto. This could be evidence of a third planet, as inner planets would be difficult to detect due to the glare from the star and dust in the system.

While the European Space Agency’s Gaia observatory may be able to detect any wobble in the star caused by Jupiter-mass planets, it could take years to confirm due to their long orbital periods.

The data was collected using the Space Telescope Imaging Spectrograph on the Hubble telescope, and the upcoming James Webb Space Telescope’s infrared technology could provide further detail.

Image Credit: Getty