Coming Soon, A New Star in Cygnus?

January 25, 2017

Well, maybe,  if Dr. Larry Molnar’s forecast is correct. The Professor of Physics and Astronomy at Calvin College in Grand Rapids feels that we may within the next few years  experience a flaring of two stars now waltzing around each other in extremely close proximity. They could be in the process of cataclysmically merging into a  single star.

 

Dr. Molnar considers himself fortunate. He came to the private West Michigan school at just the right time. In 1998, Calvin’s leadership wanted to enhance their commitment to astronomy as an important part of the science curriculum. The modest observatory, built atop the science building in the 1970’s, needed an upgrade. Molnar and his colleagues sought to make that happen not only to bring the wonder of the oldest of the sciences to the general student population, but to provide research opportunities while training future astronomers. There is solid evidence of how well they have succeeded. Calvin students are today using the  updated telescope on the Grand Rapids campus and an identical robotic telescope under the clear steady air of New Mexico to monitor nearby asteroids and stars that vary in light output. Molnar, with students and colleagues, has recently made observations that have led to a bold prediction. We in West Michigan and throughout the world may soon witness the appearance of a new star in the sky: what is termed a “luminous red nova.”

 

Molnar points out that the search for the merging stars and other significant research Calvin faculty and students have conducted in recent years has been fortuitous. “We have had some lucky breaks.” One came about due to a longstanding alliance with Rehoboth Christian School east of Gallup, New Mexico. Its campus, perched at a dark high altitude with far more clear nights per year than we experience in West Michigan, was the perfect spot to establish the robotic telescope.

 

With 21st century technology, students and staff do not have to go to New Mexico to observe. They can point the telescope and capture images robotically via the internet from computers on the Calvin campus. Often, when it is cloudy in West Michigan, it is wonderfully clear in New Mexico, so time-sensitive observations have less chance of being lost behind clouds.

 

The  two telescopes, with 16-inch mirrors for gathering starlight, are small by research standards, but are far less costly to build and operate than the giants found at mountaintop observatories. They are more accessible to ambitious students wanting to follow a particular line of research, the key to gaining new knowledge about the universe.

 

An excellent illustration involves the ongoing  effort to monitor what appears  to be  a single faint star in the constellation Cygnus, the swan. Barely bright enough to show up through Calvin’s modest telescopes, it earlier attracted astronomers’ attention because its light output is not constant. It rises and falls slightly over time. GRAAA member Daniel Van Noord, when a Calvin student a number of years ago, undertook a concentrated study of the star to find out why. Was it a single pulsing star, or perhaps two stars very close together sending out unsteady light as they rapidly orbited about a common center of gravity? He discovered they were in fact two stars, and what’s more, their dance was speeding up, a sign they were getting closer and closer to one another. 

Molnar found this discovery exciting. He has a research interest in what astronomers call “contact binary stars,” those orbiting so closely that their surfaces touch. This system seemed special – stars so close to one another that they were merging into a single object. Molnar was aware that when two stars merge, a dramatic temporary brightening can occur, similar to the well known outburst – called a nova – that occurs when two closely spaced stars produce spurts of energy as matter flows between them. The stars producing ordinary novas maintain their individual identity between outbursts, which may be periodic. To distinguish, a star system like the one in Cygnus – expected to brighten only once during the merging process – is called a  “luminous red nova.”

 

Molnar recalled a similar star that turned up a number of years ago and then flared into a nova thousands of times its previous brightness in 2008. It was too far away to attain naked eye visibility,  but it provided a recent case for comparison. “Somewhere there is the next star that is going to do this,” Molnar mused at the time. That is why Molnar and his students are monitoring the latest candidate intently. “We seem to have gotten very lucky. We have found the rate of period change to be accelerating, following the pattern preceding the 2008 outburst.” Molnar and his collaborators think that an outburst may be only two to four years away, and that this nova could become bright enough to be clearly seen with the naked eye. The constellation Cygnus, where it is located, climbs high overhead in our summertime sky, and it is above the horizon at least part of the night from March through December. If this event does occur, we in  Michigan will have a ringside seat to see it. The star in question, still  well below naked eye visibility, lies off the right  tip of the well-known “Northern Cross” asterism. Molnar summarized his work last year at a meeting of the prestigious American Astronomical Society. He notes that his report was well-received, and that the object has passed every theoretical and observational test so far. He is working on a paper about his theory and predictions for submission to the Astrophysical Journal, and adds whimsically: “Very soon, I’m going to be completely wrong or completely right.”

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