Finding Planetary Construction Zones

In 1992, Hubble was the first telescope to resolve protoplanetary disks (dubbed “proplyds”) around stars in the Orion Nebula. Hubble’s high resolution and sensitivity, along with the Orion Nebula’s proximity, have allowed the telescope to image proplyds around nearly 200 stars in the nebula. Proplyds are pancake-like disks of mostly gas and some dust surrounding a young star. They are a prerequisite for the formation of planetary systems.

Thirty proplyds in a 6 by 5 grid. Each one is unique. Some look like tadpoles, others like

Here are some of the many protoplanetary disks that were discovered by Hubble in the large, majestic Orion Nebula.

NASA, ESA, and L. Ricci (ESO)

Hubble has also done the largest and most sensitive visible-light imaging survey of debris disks around stars. Two particular stars highlight Hubble’s observations: TW Hydrae, and Beta Pictoris.

Using a mask to block the star’s bright light, Hubble scientists spotted a mysterious gap in a vast protoplanetary disk of gas and dust swirling around the star TW Hydrae. The gap is likely the result of a growing, unseen planet gravitationally sweeping up material and carving out a lane in the disk like a snowplow. The 1.9 billion-mile-wide gap isn’t completely cleared of material yet.

TW Hydrae Hubble observation (left) and illustration (right)

This Hubble image (left) and graphic (right) show a gap in a protoplanetary disk of dust and gas whirling around the nearby red dwarf star TW Hydrae. The gap’s presence is probably due to the effects of a growing, unseen planet that is gravitationally sweeping up material and carving out a lane in the disk. Astronomers used a masking device within the Hubble camera to block out the star’s bright light so that the disk’s structure could be seen.

NASA, ESA, J. Debes (STScI), H. Jang-Condell (University of Wyoming), A. Weinberger (Carnegie Institution of Washington), A. Roberge (Goddard Space Flight Center), G. Schneider (University of Arizona/Steward Observatory) and A. Feild (STScI/AURA)

More recently, astronomers using Hubble noticed a change in brightness with position of TW Hydrae's disk. Because Hubble has 18 years' worth of observations of the star, the astronomers could assemble a time-lapse movie of the shadow's rotation. They think an unseen planet in the disk is gravitationally pulling on material near the star and warping the inner part of the disk. The twisted, misaligned inner disk is casting its shadow across the surface of the outer disk.

four part graphic showing orange rings against black

These images, taken a year apart by NASA's Hubble Space Telescope, reveal a shadow moving counterclockwise around a gas-and-dust disk encircling the young star TW Hydrae. The two images at the top, taken by the Space Telescope Imaging Spectrograph, show an uneven brightness across the disk. Through enhanced image processing (images at bottom), the darkening becomes even more apparent. These enhanced images allowed astronomers to determine the reason for the changes in brightness. The dimmer areas of the disk, at top left, are caused by a shadow spreading across the outer disk. The dotted lines approximate the shadow's coverage. The long arrows show how far the shadow has moved in a year (from 2015-2016), which is roughly 20 degrees. Based on Hubble archival data, astronomers determined that the shadow completes a rotation around the central star every 16 years. They know the feature is a shadow because dust and gas in the disk do not orbit the star nearly that quickly. So, the feature must not be part of the physical disk. The shadow may be caused by the gravitational effect of an unseen planet orbiting close to the star. The planet pulls up material from the main disk, creating a warped inner disk. The twisted disk blocks light from the star and casts a shadow onto the disk's outer region.

NASA, ESA, and J. Debes (STScI)

Hubble researchers also studied changes in the planetary disk surrounding Beta Pictoris. By masking out the star’s light, they could detect changes in the material orbiting the star. The results point to a massive planet embedded within the star’s dust disk. Astronomers spotted the planet using the European Southern Observatory.

Hubble has given astronomers the most detailed picture to date of a large, edge-on, gas-and-dust disk encircling the 20-million-year-old star Beta Pictoris. Ongoing changes seen in the disk allow scientists to study the effect of a massive planet embedded within the orbiting material. Beta Pictoris itself is hidden by the dark spot that masks out the the bright star at the center of each image, allowing astronomers to see the disk.

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

Hubble’s ultraviolet sensitivities captured radiation falling onto a planet forming around the star PDS 70. Previous observations with ground-based telescopes revealed two massive Jupiter-sized, planets carving out a wide gap within the planetary disk of the star. Located some 370 million light-years away, the young 6-million-year-old star is slightly smaller and less massive than the Sun.

Hubble observations pinpoint planet PDS 70b. A coronagraph on Hubble’s camera blocks out the glare of the central star for the planet to be directly observed. The team’s fresh technique for using Hubble to directly image this planet paves a new route for further exoplanet research, especially during a planet’s formative years.

NASA, ESA, McDonald Observatory–University of Texas, Yifan Zhou (UT); Image Processing: Joseph DePasquale (STScI)

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