Twinkle, twinkle, little dot

Are you a planet or are you not?

The faint celestial object TMR-1C has had a checkered past — and now it has a checkered present.

IS IT OR ISN’T IT? Possibly the first photograph ever taken of a planet outside the solar system, this 1998 image shows a faint object 450 light-years from Earth (lower left, connected to a pair of stars by a luminous filament). NASA

In 1998, NASA proclaimed that a picture taken of the body a year earlier with the Hubble Space Telescope — a fuzzy white dot — might go down in history as the first planet beyond the solar system to be photographed (SN: 6/6/98, p. 357). The discovery team, led by Susan Terebey, now at California State University, Los Angeles, suggested that the object’s location — at the end of a long, luminous filament emanating from two newborn stars — indicated that TMR-1C was a planet cast off by those incipient suns.

Many researchers were skeptical, noting that the apparent association between the object and the youthful stars might be a chance alignment on the sky. Only a year later Terebey herself declared that the body was too hot to be a planet and could be just an old background star (SN: 6/26/99, p. 404).

Now two independent studies, both set to appear in an upcoming Astronomy & Astrophysics, indicate that Terebey may have written off TMR-1C prematurely. Both reports provide evidence that the object is closely linked to the pair of youthful stars, which are likely members of the Taurus star-forming region some 450 light-years from Earth. While one of the studies suggests TMR-1C is just another low-mass star associated with the pair, the other suggests it could indeed be a planet.

“We may have to credit Terebey et al with finding a planet after all, but it is perhaps too soon to jump to that conclusion, just as it was too soon to discard the object as a planet 10 years ago,” says Eduardo Martin of the Centro de Astrobiologia in Madrid, a coauthor of one of the new studies. He and Basmah Riaz of the Instituto Astrofisica de Canarias in Tenerife, Spain, posted their findings online August 9.

Martin and Riaz compared observations they made with the Canada-France-Hawaii Telescope atop Hawaii’s Mauna Kea in late 2002 and early 2009 with those recorded by Terebey and her colleagues earlier using the Hubble Space Telescope. The pair found that the object became much bluer between 1998 and 2002 and more than doubled its brightness between 1998 and 2009.

That rapid and large variability suggests that TMR-1C is not an old background star, but a young, nearby object, the researchers say. The astronomers attribute the brightness and color changes to shifts in the concentration of dust surrounding the body. The presence of warm dust, if unaccounted for, could also have fooled Terebey and her colleagues into thinking that TMR-1C is too hot to be a planet, Martin adds.

“This object should be reconsidered as a planet candidate” with a mass a few times that of Jupiter, as Terebey’s team initially proposed, he says.

Another team, which includes Monika Petr-Gotzens of the European Southern Observatory in Garching, Germany, took both infrared images and spectra of TMR-1C with the Very Large Telescope in Chile. The team, which posted its findings online July 30, also finds that the object cannot be a background star. But the researchers say the estimated temperature of the body, greater than 3,000 kelvins, indicates it’s not a planet but a nearby, low-mass star surrounded by a dusty disk. Martin contends, however, that the team doesn’t provide a definitive enough dataset to establish that the object has such a high temperature.

Petr-Gotzens and her colleagues also discovered another faint object, dubbed TMR-1D, which lies at the end of another bright filament emanating from the same pair of young stars. The researchers classify the object as yet another low-mass star, but Martin says it’s possible the new-found object could be a second planet ejected by the pair of newborns.

Comments Mark Marley of NASA’s Ames Research Center in Moffett Field, Calif.: “I’m not convinced by either study. This is a very faint and difficult-to-observe object.”

Terebey says “the new data for TMR-1C are intriguing to consider but not yet conclusive.” Petr-Gotzens and her colleagues show that the object is not a background body, while the variability and increasing brightness at bluer colors demonstrated by Riaz and Martin indicate that the object is both young and of a type that fits the planet models better than previous observations do, she notes.

If TMR-1C turns out to be a planet, says Adam Burrows of Princeton University, “this would punctuate one of the strangest episodes in the history of the emerging field of exoplanet research. If false, it would be one more warning that numerous pitfalls await the intrepid astronomer in search of planetary gold beyond the solar system.”

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