Speaking of Hubble...

Archive: October 2010

Phantom Planet

October 20, 2010 by Ray Villard
TMR-1C appears to lie at the end of a strange filament of light.

TMR-1C appears to lie at the end of a strange filament of light.

Hundreds of planets have been found beyond our solar system. Of these “extrasolar planets,” or “exoplanets” for short, one has remained perplexing and infamous 12 years after its purported discovery.

The object’s formal designation is TMR-1c. It lies about 450 light-years away in the Taurus molecular cloud.  Back in 1998, astronomer Susan Tereby announced that this could be the first exoplanet directly photographed. At the time, Tereby cautiously called it a “candidate planet.”

Hubble’s  infrared image was compellingly believable.  A very red — and therefore cool — pinpoint object was at the end of a ghostly finger of illuminated dust stretching 135 billion miles from a young binary star system. The telltale finger was interpreted as being formed after the planet was gravitationally ejected from the binary system.

But it was not clear if the object was actually co-moving along with the double star, or whether it was actually even in the Taurus star-forming region. The object might look red only because its light is scattered by dust — as we seen in sunsets.

A year after the front-page news announcement of the first snapshot of an exoplanet, Tereby reported that follow-up spectroscopy showed the object was a likely a background star.

But now we have even more data spanning a decade since the Hubble observation. A team of astronomers using the Canada-France-Hawaii telescope looked at the object in 2009. They found it had gotten brighter and bluer — a trick a star could never perform on such a short timescale unless it exploded.

They propose it is a young protoplanet surrounded by a thick, spinning disk of dust. This might explain the variability of the planet’s light. The dust only periodically reddens the starlight when the disk is tilted at the right orientation to us.  The researchers say they support Tereby’s initial analysis, that the object could have been “kicked off the island” by gravitational pinball in the young binary system.

Another team using the European Southern Observatory’s Very Large Telescope in Chile maintains that the object is 5,000 degrees Fahrenheit — way too hot for a planet. But they too think the very red color is produced by a dusty disk scattering light.

There is still a lot more to be learned about TMR-1c, whatever it is.