And now – photographs of a planet around another star

I have a soft spot in my heart for the “friendly star” Fomalhaut and now I find it even more interesting, for they have actually been able to photograph, for the first time, a planet (almost certainly) orbiting another star. This is a great time of year to get a peak at Fomalhaut, easily visible to the naked eye, though you’ll see it’s planet only with your mind’s eye. More on this in a moment.

Frist, here’s a portion of a relevant press release with images from NASA.

NASA’s Hubble Space Telescope has taken the first visible-light snapshot of a planet circling another star.

Estimated to be no more than three times Jupiter’s mass, the planet, called Fomalhaut b, orbits the bright southern star Fomalhaut, located 25 light-years away in the constellation Piscis Australis (the Southern Fish).

Fomalhaut has been a candidate for planet hunting ever since an excess of dust was discovered around the star in the early 1980s by NASA’s Infrared Astronomy Satellite (IRAS).

In 2004, the coronagraph in the High Resolution Camera on Hubble’s Advanced Camera for Surveys produced the first-ever resolved visible-light image of a large dust belt surrounding Fomalhaut. It clearly showed that this structure is in fact a ring of protoplanetary debris approximately 21.5 billion miles across with a sharp inner edge.

This large debris disk is similar to the Kuiper Belt, which encircles the solar system and contains a range of icy bodies from dust grains to objects the size of dwarf planets, such as Pluto.

Chart provided by NASA showing that the suspected planet is far from its star in this youthful solar system.

Chart provided by NASA showing that the suspected planet is far from its star in this youthful solar system.

Hubble astronomer Paul Kalas, of the University of California at Berkeley, and team members proposed in 2005 that the ring was being gravitationally modified by a planet lying between the star and the ring’s inner edge.

Circumstantial evidence came from Hubble’s confirmation that the ring is offset from the center of the star. The sharp inner edge of the ring is also consistent with the presence of a planet that gravitationally “shepherds” ring particles. Independent researchers have subsequently reached similar conclusions.

Now, Hubble has actually photographed a point source of light lying 1.8 billion miles inside the ring’s inner edge. The results are being reported in the November 13 issue of Science magazine.

“Our Hubble observations were incredibly demanding. Fomalhaut b is 1 billion times fainter than the star. We began this program in 2001, and our persistence finally paid off,” Kalas says.

“Fomalhaut is the gift that keeps on giving. Following the unexpected discovery of its dust ring, we have now found an exoplanet at a location suggested by analysis of the dust ring’s shape. The lesson for exoplanet hunters is ‘follow the dust,'” says team member Mark Clampin of NASA’s Goddard Space Flight Center.

Now – about seeing Fomalhaut yourself. My direction are for folks living in mid-northern latitudes, such as I am – roughly 40 degrees north. For me, Fomalhaut is readily visible as a bright star – the only bright star – that at 7 pm EST is roughly 20 degrees above my horizon when facing due south. This is true for the next week or two, but the time when it is due south will get steadily earlier by roughly 4 minutes a day. For a more generic finder guide, use this photo-chart from NASA.

Photo-chart showing location of Fomalhaut relative to other prominent stars.

Photo-chart showing location of Fomalhaut relative to other prominent stars.

Last year I described Fomalhaut this way to my observing class:

Fomalhaut, we hardly know thee!

No kidding. I think of this as the loneliest of our Friendly Stars because there just isn’t much around it in our sky. I seldom see it from Driftway, and no one seems to agree upon how to pronounce it’s name. (I use: FO-mal-ought.) In the past couple of years Fomalhaut has become one the most interesting stars because it seems to include an evolving planetary system that Hubble has actually imaged.

In the list of the 200 brightest stars, it is a respectable 18th at magnitude 1.16 and a distance of just 22 light years (or 25 depending on who you want to believe 😉 It’s also young – a few million years old – and a bit larger than our Sun.

The term “friendly stars” comes from the turn-of-the-century book “The Friendly Stars” by Martha Evans Martin, Published by Harper & brothers, 1907. I love this book and think it’s basic idea – teach the brightest stars, not the constellations as such – remains the best way to become familiar with the night sky.