What Is The ‘Vermin Galaxy’? Hubble Captures Galaxy Transiting Behind Star HD 107146

From the treasure trove of images captured by NASA’s Hubble Space Telescope, the space agency released an image Friday that shows a distant galaxy as it begins it transit behind a star that lies much closer to Earth. The transit is of significance because it allows scientists to study the star HD 107146, which is very similar to the sun.

HD 107146 is about 90 light-years away from Earth, and its physical properties are very similar to the sun. It has a mass of about 1.09 suns, and its size is about 99 percent that of the sun. But compared to the 4.6 billion years the sun has been around, this star is a youngster whose age is between 80 and 200 million years only. It also has a circumstellar disk of orbiting debris that appears as the numerous jagged spikes in the Hubble image. Given the star’s similarities to the sun, this disk — visible to us face-on — could be similar to the asteroids and the Kuiper belt in our solar system.

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The “Vermin Galaxy” — which NASA said was a nickname coined by some astronomers to display their annoyance at its presence — is much farther away in space, compared to HD 107146. The pairing of the star and the galaxy was first observed by Hubble in 2004, and then again in 2011, and the latter image is the one NASA released Friday. A 2009 paper, published in the Astrophysical Journal Letters, suggested the presence of a planet at an orbital distance of 45-75 times the distance between Earth and the sun.

In the image, the galaxy appears as the bright smudge near the lower right corner, while the green circle in the center marks the location of the star. The large and orange concentric circle around the star indicates the circumstellar debris. The light from the star has been blocked in this image; otherwise, its surroundings and the faint galaxy would not be visible.

The transit of the galaxy behind HD 107146 will be complete only by 2020, which is when it will be fully obscured by the star. Transits are valuable to study distant objects, because they cause, even when not complete, a change in the light that is observed by our instruments.

“Light from the galaxy will pass through the star’s debris disks before reaching our telescopes, allowing us to study the properties of the light and how it changes, and thus infer the characteristics of the disk itself,” NASA explained in a statement, which was put together by the European Space Agency (ESA) and accompanied the image.

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The Hubble Space Telescope is a collaboration between NASA and ESA, and has been operational since 1990. Its successor, the far more powerful James Webb Space Telescope, is being developed by NASA, ESA and the Canadian Space Agency, and is scheduled for an October 2018 launch.