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Tiny Satellites Are Telling Us About How Super Bright Stars Are Formed

Canada's BRITE mission is studying the brightest stars in the sky.
May 30, 2016, 10:00am

In a funny astronomical twist, the stars you see while sipping a beer on the back porch are actually really hard for a telescope to observe. These stars—known as "naked-eye stars"—are so bright, they saturate the sensitive detector on an instrument like the Hubble Space Telescope.

In 2013, Canada teamed up with Austria and Poland to beam up a constellation of six space-based telescopes called BRITE. Each one is about the size of a car battery: these satellites, which orbit the Earth, are only 20 centimeters across and have a tiny telescope inside with a 30-millimetre mirror.

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They're modest, but mighty. These telescopes can stare at one single star for up to six months at a time. They also have a wide field of view, allowing scientists to compare several stars at once. Now, the first science results have finally been published, and at least 40 new papers are expected in the coming months. The results will be presented at the Canadian Astronomical Society meeting this week.

The space telescopes are the size of a car battery. Image: UTIAS Space Flight Laboratory

"We can do more if only we had the capacity to do it," said Anthony Moffat, the scientific mission lead for Canada's contribution, in an interview with Motherboard. The Canadian Space Agency spent $4.07 million on BRITE.

"We can't download data faster than a certain rate. It's not an extensive mission, so we can't afford the latest and greatest technologies," added Moffat, who is a professor emeritus at the Université de Montreal. "We have three [satellite] ground stations [in Austria and Poland] and are hoping to get a fourth one up in Vancouver in the next couple of months."

Of the space-based telescopes planned in the mission, two each are from Canada, Austria and Poland. But only five are returning results, because one of the Canadian satellites got stuck on a Russian rocket stage that was supposed to kick it up to its proper orbit. The satellite is working perfectly, but it is in the wrong orbit and can't do proper observations, Moffat said.

The ultimate goal is to figure out how these stars formed. Because you can't exactly open up a star to see what's inside, scientists have to infer what goes on in the core. To do this, they use a technique called asteroseismology—checking out vibrations on the star's surface—and then make estimates about the star's insides. It's a technique we use often on our own sun to better learn how it belches solar flares, for example.

So far, published results (here, here and here) in the journal Astronomy & Astrophysics paint an interesting picture. For example, the team discovered that one rapidly rotating star regularly sheds mass in tune with how it pulses (gets brighter and dimmer again). BRITE also detected two bright spots on another fast-rotating star, and found 19 different pulsation frequencies on a hot star, which sets a new record.

Huge stars bigger than our own sun are known for blowing gigantic winds of gas in their neighbourhoods, which can create massive clouds and perhaps even new areas of star birth. (Sometimes these stars also explode.) Some of the forthcoming papers will look at how these winds are generated in massive stars, Moffat said. Others will look at what happens as winds from two stars collide with each other.

With the remaining five satellites working well, Moffat said a future area for observation will be the Orion field, which is a rich zone of bright stars in the Orion constellation. The constellation hosts some of the brightest stars in the sky, and is easy to spot due to the well-known asterism of three stars that we call "Orion's belt."

The real advantage of BRITE is it will be able to repeat observations. Moffat said he hopes the satellites will last at least a decade, which would be a similar lifespan to Canada's successful tiny space telescope, MOST (Microvariability and Oscillations of Stars).