AU and AT Microscopii AB
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AU and AT Microscopii AB are all dim red dwarf stars,
like Gliese 623 A (M2.5V) and B (M5.8Ve) at lower right.
(See a Digitized Sky Survey field image around AU and
AT Microscopii AB at NASA's NStars Database.)
AU Microscopii is now thought to be gravitionally bound to the relatively distant dim binary system of AT Microscopii, located around 1.2 light-years (ly) away. The triple system is located around 32.4 ly from our Sun, Sol, in the part (AU Mic - 20:45:9.5-31:20:27.2 and AT Mic AB 20:41:51.2-32:26:6.8 ICRS 2000.0) of Constellation Indus, the Indian -- . However, all three stars are is too faint to be seen with the naked eye. All three stars are around the same age as Beta Pictoris and part of 20 stars identified as being part of the Beta Pictoris moving group. In February 26, 2004, astronomers announced evidence for a planet around AU Mic based on the discovery of a hole in the star's circumstellar dust disk (physicsweb article).
This cool and dim, main sequence red dwarf (M0-1 Ve) has only around 0.5 Sol's mass (Paul Kalas), a much smaller of its diameter (Claud H. Lacy, 1977, page 481), and about 10 percent of its brightness (Paul Kalas). However, AU Microscopii is a very young flare star, only around 12 million years old (eight to 20 million years old). Some alternative names and useful star catalogue numbers are: AU Mic, Gl 803, Hip 102409, HD 197481, CD-31 17815, CP(D)-31 6335, SAO 212402, LTT 8214, and V 824.
Using the University of Hawaii's 2.2-meter telescope, a team of astronomers (including Paul Kalas, Michael Liu, and others) found that AU Mic had an infra-red excess in its spectrum suggesting hat the star is surrounded by a dusty disk like sister star Beta Pictoris, which was likely to have been born from the same nebula but with three to four times more dust in its disk. Then, to obtain an image of the disk, they blocked out the glare of the star using a device known as a coronagraph and found that the disk extended from 50 to about 210 AUs (21") from the star. In a separate experiment that is to be reported in the Astrophysical Journal, Kalas' group calculated that the disk has a hole in it that extends out to 17 AU from the star that may indicate the presence of a planet. To try and confirm that this is indeed the case, they will now collect sharper images of the star using the Hubble and Spitzer space telescopes.
Hunt for Substellar Companions
The distance from AU Microscopii where an Earth-type planet would be comfortable with liquid water is less than 0.04 AU result in a "day" that last less than 10 hours. At that distance, the rotation of the planet would probably be tidally locked with the star so that one side would have perpetual daylight while the other would be in eternal darkness. Moreover, AU Microscopii's light is so red that Earth-type plants may not be able to photosynthesize very well.
AT Microscopii A
This cool and dim, main sequence red dwarf (M4.5 Vpe) probably has less than half of Sol's mass (RECONS), 11 percent of its diameter (Claud H. Lacy, 1977, page 481), and about 12/1,000,000th of its brightness. However, AT Microscopii is a flare star, probably around 12 million years old like AT Mic. In 1962, it was separated from its companion star by only around 40 AUs -- SepAB= 3.9". Some alternative names and useful star catalogue numbers are: AT Mic A, Gl 799 A, Hip 102141, HD 196982, CD-31 16135 A, CP(D)-31 6181, SAO 212355, LTT 8181, LDS 720, and U or UGP 502.
AT Microscopii B
This cool and dim, main sequence red dwarf (M4.5 Ve) probably has less than half of Sol's mass (RECONS), 11 percent of its diameter (Claud H. Lacy, 1977, page 481), and about 12/1,000,000th of its brightness. However, it is probably around 12 million years old like AT Mic. Some alternative names and useful star catalogue numbers are: AT Mic B, Gl 799 B, CD-31 16135 B, and CP(D)-31 6181 B.
The following star systems are located within 10 ly of AU Microscopii.
|Star System||Spectra &|
|AT Microscopii AB||M4.5 Vpe |
|CD-27 14659 AB||K0-3 V |
|AC+20 76187||DA /VII||6.3|
|L 499-56||M3.5 V||9.2|
Up-to-date technical summaries on this star can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARICNS, NASA's NStar Database, and the Research Consortium on Nearby Stars (RECONS) list of the 100 Nearest Star Systems. Additional information may be available at Roger Wilcox's Internet Stellar Database.
For more information about stars including spectral and luminosity class codes, go to ChView's webpage on The Stars of the Milky Way.
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