In the vastness of space, astronomers are likely to find examples of almost all astronomical phenomena if they look closely enough. Many planetary phenomena are becoming increasingly acute as astronomy continues to focus on finding exoplanets. Now a team led by Yifan Zhou from UT Austin has directly imaged a gas giant that is still in formation.
To this end, the team has used the astronomers’ workhorse – Hubble – for the past 30 years. They aimed it at the orange dwarf system PDS 70, which is known to have two planets in the formation phase. The system is located in the constellation Centaurus, about 370 light years from our solar system. One of its planets, PDS 70b, is a gas giant orbiting its star at about the same distance as Uranus from our sun.
Image of the protoplanetary surrounding PDS 70.
Photo credits: ESO, VLT, André B. Müller (ESO)
At about 5 million years old, PDS 70b is still relatively young, but has already grown to the size of about 5 Jupiters. It also appears to be at the end of its growth phase and will only collect about 1/100 of the mass of Jupiter for the next million years if it maintains its current rate of growth.
This growth is driven by a circumplanetary disk that collects material from a larger circumstellar disk and directs it to the planet. These funnels follow magnetic field lines into the planet’s atmosphere and can be viewed in particularly hot spots in ultraviolet wavelengths.
Astronomy Cast Episode about the direct imaging method of exoplanets
Dr. Zhou and his team managed to map the planet directly. This makes him one of only about 15 that have been directly imaged so far, and the youngest of those that Hubble has imaged. They used the space telescope’s ultraviolet sensors to capture an image of both the PDS 70 star and its growing gas giant. The problem was filtering out the star’s light, which was 3,000 times brighter than the planet’s ultraviolet light.
With a new type of post-processing technique, Dr. Zhou block the light from the star, leaving only the light emitted from the planet for analysis. In doing so, he also reduced the maximum orbit of the maximum exoplanet by one star, which Hubble can see by a factor of five.
Processed image of the gas giant PDS 70b with blocked starlight.
Photo credit: NASA, ESA, McDonald Observatory – University of Texas, Yifan Zhou (UT), Joseph DePasquale (STScI)
The team suggests that this observation is only a snapshot of time, so there is no data on changes in the rate at which the PDS 70b continues to grow or how close it is to completion of its growth. However, if you string enough snapshots together over time, it creates a moving image that provides more information than a single one could ever be. With luck, Hubble will continue to collect more data through the PDS 70 system, with Dr. Zhou’s techniques are used to track the progress of his planet’s fascinating creation process.
Hubble Site – Exoplanet PDS 70B engulfs gas and dust as it continues to build up mass
The Astronomical Journal – Hubble Space Telescope UV and H? Measurements of the accretion excess emission from the young giant planet PDS 70 b
Sci-News – Hubble Captures First Ultraviolet Image of an Exoplanet
SyFy – HUBBLE SEES A VERY YOUNG EXOPLANET ENDING A GROWTH TRACK
Artistic idea of the planet PD 70b showing material flowing into the atmosphere along magnetic fields.
Photo credit: McDonald Observatory – UT, Yifan Zhou (UT), NASA, ESA, STScI, Joseph Olmsted (STScI)