Theories need a continuum of data to illustrate plausible developmental or evolutionary steps. The more data that can be accumulated across a continuum, the more fully the theoretical framework can be filled in or fleshed out. Mar Mezcua of the Harvard-Smithsonian Center for Astrophysics who is leading the mid-sized black hole study, says that astronomy, like paleontology, needs to fill in the gaps in theory but that astronomers “‘dig’ up [their] discoveries in galaxies that are millions of light years away.”
Small, Medium and Large Black Holes
Black hole theory posits three sizes of black holes suggesting three stages of growth. Small black holes are of the class called stellar-mass black holes and are between five and 30 times the mass of the Sun. These are in the stellar (or star) mass range. Large black holes are of the class called supermassive black holes and are between millions to billions times the mass of the Sun. At the center of galaxies, these can be thought of as galactic black holes. What lies in between stellar and galactic black holes?
If black holes grow through time as is theorized, there must be a size class between star-size and galactic-center-size. Theorists call the missing size class intermediate-mass black hole, or IMBH, but astronomical data has been missing to support the IMBH class hypothesis: the missing link to the family tree has been nowhere to be found. Some scientists, though, suspected ultraluminous X-ray source objects might provide a clue to the missing link.
Intermediate-Mass Black Hole Found by Chandra Observatory
Located in an arm of a spiral galaxy about 100 million light years away, Chandra Observatory, in partnership with XMM-Newton and e-VLBI, has spotted what appears to be an intermediate-mass black hole. The intermediate-sized IMBH is called NGC2276-3c because the spiral galaxy it lies in is known as NGC 2276.
What Is the Significance of This Discovery?
Black hole theory says that supermassive black holes grow in size over time from “seed” black holes that lie in the mass range occupied by hypothesized IMBHs. In other words, it is thought that medium-sized black holes provide the seed ground for the growth of large black holes. Now that a black hole fitting the intermediate size range, between hundreds to hundred-thousands times the mass of the Sun, has been identified, it will be possible to gather data to support or refute the theory of black hole growth. Lead scientist and study author Mar Mezcua expects NGC2276-3c will provide answers to how black holes evolve and how they influence their surroundings thereby tying together the existing data for all classes of black holes.
Co-author Andrei Lobanov of the Max Planck Institute for Radio Astronomy in Bonn, Germany, suggests that the similar properties of all three classes of black holes lead to the expectation that there will be a cohesive unity connecting development from one class to the next: “We found that NGC2276-3c has traits similar to both stellar-mass black holes and supermassive black holes. In other words, this object helps tie the whole black hole family together.”
Features of NGC2276-3c
The several remarkable features of IMBH NGC2276-3c will help scientists from the Chandra project and ultraluminous X-ray sources project to answer questions about its formation; about possible collision and merger of two galaxies; and about its influence on star formation. The features of note are:
• its production of powerful jet of radio waves extending 2,000 light years from its center.
• a 1,000 light years swatch along the jet stream from NGC2276-3c that seems to be missing young stars in a galactic area where annual formation of young stars is the equivalent of five to fifteen times the Sun’s mass.
• star formation evidence that NGC2276-3c exerts strong influence in its local environment indicated by the possibility that the radio jet streaming form IMBH NGC2276-3c cleared a cavity in the surrounding stellar gas thereby suppressing star formation.
Luminous Scientific Teamwork with X-Ray, Radio Astronomy and Ultra Luminosity
Mar Mezcua of the Harvard-Smithsonian Center for Astrophysics led the Chandra X-ray Observatory study in co-authorship with Andrei Lobanov of the Max Planck Institute for Radio Astronomy in Bonn, Germany, operating the European Very Long Baseline Interferometry (e-VLBI) Network. In Milan, Italy, Anna Wolter of the National Institute for Astrophysics (INAF) led the study of ultraluminous X-ray sources (ULXs) observed by ESA’s XMM-Newton. Wolter’s work with her colleagues led to the identification of IMBH NGC2276-3c as one of a group of five ULXs that had previously been thought to comprise just one ULX. The Mezcua and Wolter papers are published separately in the Monthly Notices of the Royal Astronomical Society and are also available online.
