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.
Credits
NASA, ESA, and J. Debes (STScI)| About The Object | |
|---|---|
| Object Name | TW Hydrae |
| Object Description | T Tauri Star |
| R.A. Position | 11h 01m 51.91s |
| Dec. Position | -34º 42’ 17.0” |
| Constellation | Hydra |
| Distance | About 180 light-years (54 parsecs). The images are approximately 6 arcseconds, or roughly 400 AU, wide. |
| About The Data | |
| Data Description | Datasets used for these results are from the HST proposal 13753, John Debes (STScI) P.I. and lead author. |
| Instrument | HST>STIS/CCD |
| Exposure Dates | May 2015, March 2016 |
| Filters | 50CCD |
| About The Image | |
| Color Info | The images were acquired by HST’s STIS CCD instrument using the 50CCD (clear imaging) filter. Color was applied using a colormap assigning a different color to each brightness value. |
| About The Object | |
|---|---|
| Object Name | A name or catalog number that astronomers use to identify an astronomical object. |
| Object Description | The type of astronomical object. |
| R.A. Position | Right ascension – analogous to longitude – is one component of an object's position. |
| Dec. Position | Declination – analogous to latitude – is one component of an object's position. |
| Constellation | One of 88 recognized regions of the celestial sphere in which the object appears. |
| Distance | The physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs. |
| Dimensions | The physical size of the object or the apparent angle it subtends on the sky. |
| About The Data | |
| Data Description |
|
| Instrument | The science instrument used to produce the data. |
| Exposure Dates | The date(s) that the telescope made its observations and the total exposure time. |
| Filters | The camera filters that were used in the science observations. |
| About The Image | |
| Image Credit | The primary individuals and institutions responsible for the content. |
| Publication Date | The date and time the release content became public. |
| Color Info | A brief description of the methods used to convert telescope data into the color image being presented. |
| Orientation | The rotation of the image on the sky with respect to the north pole of the celestial sphere. |
