The Ison comet is photographed here by the Hubble Space Telescope as it races through space.
''The future of comet Ison does not look bright,'' astronomer Ignacio Ferrin, with the University of Antioquia in Colombia, said in a statement.
Ferrin's calculations show the comet, which is currently moving toward the Sun at 26km per second, has not brightened since mid-January. That may be because the comet is already out of ice particles in its body, which melt as the comet moves closer to the Sun, creating a long, bright tail.
Another theory is that the comet is covered in a layer of silicate dust that snuffs out water vapor and other gases that brighten the comet.
''Comet ISON has been on a standstill for more than 132 days... a rather puzzling feat,'' Ferrin wrote in a paper submitted to the Monthly Notices of the Royal Astronomical Society and posted online at the archival site arXiv.org.
The comet, named Ison for the International Scientific Optical Network that made its discovery, was found in September 2012 by two amateur Russian astronomers.
It is due to pass about 1.2 million km from the Sun on November 28.
The relatively close pass was expected to create a massive tail that some scientists predict will be visible even in daylight.
If it survives, that is. At that distance, the comet would reach temperatures of about 2700 degrees Celsius - hot enough to melt lead. It may also be pulled apart by the Sun's gravity.
Scientists believe the comet hails from the Oort Cloud, a cluster of icy rocks that circle the Sun about 50,000 times farther away than Earth's orbit.
Calculations show Comet Ison is making its first - and possibly last - voyage into the inner solar system.