More “Voorwerps”?
- By Maggie Masetti
- April 16, 2015
- Comments Off on More “Voorwerps”?
Back in 2010, Koji wrote a guest blog for us on Hanny’s Voorwerp. What is this? Back in 2007, a Dutch woman named Hanny van Arkel discovered an odd and until then unclassified ghostly gaseous structure near the galaxy IC 2497 while using the citizen science site, Galaxy Zoo. The object was named Hanny’s Voorwerp, or Hanny’s Object in Dutch.
Ground-based optical image of IC 2497 (top), Hanny’s Voorwerp (bottom), and a nearby
companion galaxy (left). This image is a composite of blue, visual, and near infrared light
images taken with the WIYN telescope. Credit: WIYN/William Keel/Anna Manning
It’s now thought that the Voorwerp was spotted because the galaxy near it once had a bright quasar at its center – that is, a bright, energetic object that is powered by a black hole. The quasar may have illuminated the Voorwerp by hitting it with a beam of light, almost like a searchlight would. Astronomers did follow-up observations with the Hubble Space Telescope, revealing the quasar-lit Voorwerp to be just one part of a huge streamer of gas 300,000 light years long, which stretches around IC 2497!
Hubble’s view of Hanny’s Voorwerp and IC 2497. Credit: NASA, ESA, W. Keel (University of Alabama), and the Galaxy Zoo Team
The Hubble images also showed clusters of stars in an area only a few thousand light-years wide at the tip of the Voorwerp (where it appears yellowish-organge). Starbirth in this object may have been triggered by the gas flowing from the galaxy compressing the gas in this region of the Voorwerp. For scale, the Voorwerp is about the size of our Milky Way galaxy. The bright green color of the Voorwerp comes from glowing oxygen.
So why does this streamer of gas (and the Voorwerp) exist? It’s currently thought that the streamer is a remnant of a long-ago galaxy collision!
Bill Keel of the University of Alabama, Tuscaloosa decided to see if there were other examples of the Voorwerp phenomena to be found elsewhere in the Universe. Using 200 volunteers who looked at Hubble archival data of 15,000 galaxies that also hosted quasars, eight other such structures that had been similarly illuminated were found. Here they are below. (Visit Hubblesite.org to see individual photos of these objects. There is also a a full feature on them available.)
Credit: NASA, ESA, and W. Keel (University of Alabama, Tuscaloosa)
These Hubble images also appear to support that hypothesis that these structures are the result of the collision of galaxies. To learn more about these newly discovered objects, visit the feature on Hubblesite.org and watch the video of the Hubble Hangout discussing them.
Since galaxy collisions and interactions are something that Hubble’s successor, the James Webb Space Telescope, will specifically be used to study, it’s always possible we’ll see further study of this interesting phenomena!
