News about a nearby brown dwarf occupies us this morning, but first, a quick site update. The recent server problems did not, fortunately, result in the loss of any data, but I’ve had to make some temporary software changes to get Centauri Dreams back up. Expect more changes in coming weeks as I replace these fixes, so you may see things in transition for a time, but the server switchover is complete. One remaining problem is a snafu in image uploads that I hope to fix soon.
Now, to brown dwarfs. Seeing them is tricky business. Too small to be stars (although they do fuse deuterium), too massive to be planets, they’re hard to pick out in visible light and are generally detected at infrared wavelengths. Now a faint brown dwarf orbiting the nearby star Wolf 940 has been discovered. The primary is a red dwarf some 40 light years from Earth, orbited by its dim neighbor at a distance of some 440 AU.
This may bring to mind our recent discussion of Lorenzo Iorio’s work, which settled on a figure of 3,736-3,817 AU from the Sun as the nearest distance an undetected brown dwarf could exist near us. Wolf 940 B is obviously in a much tighter relationship than that with its primary. And astronomers studying the object hope that it may prove useful in telling us about the age and composition of brown dwarfs.
Ben Burningham (University of Hertfordshire) notes the dwarf’s cool temperature (by stellar standards) of 300 degrees Celsius, and says that its proximity to the red dwarf may come in handy:
“What’s so exciting in this case, is that we can use what we know about the primary star to find out about the properties of the brown dwarf, and that makes it an extremely useful find. You can think of it as a Rosetta Stone for decrypting what the light from such cool objects is telling us.”
The UKIRT Infrared Deep Sky Survey, based on Mauna Kea, is carrying out the work that resulted in this detection, flagging the brown dwarf as a companion to Wolf 940 after studying their common motion. We’re in an era of large scale surveys, and the question that now arises is whether brown dwarf/red dwarf binaries are unusual or whether we’re going to learn that red dwarfs often have such companions. In any case, Wolf 940 B should be helpful in finding out more about brown dwarfs and the nature of warm planetary atmospheres. The paper will run soon in Monthly Notices of the Royal Astronomical Society.
Speaking of nearby objects, Max Wolf, who discovered Wolf 940 some ninety years ago, seems to have had a penchant for finding them. He’s also the discoverer of Wolf 359, located 7.7 light years away and, like Wolf 940, a red dwarf (one with a relatively high flare rate, at that). Max Wolf was also a prolific asteroid finder, a pioneer in astrophotographic techniques, and the discoverer of several comets. He is not, however, associated with the so-called Wolf-Rayet stars. That would be the French astronomer Charles Wolf.