[BRIEF NOTE] On Gliese 570
Mar. 15th, 2010 10:30 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
rfmcdonaldBy now, I expect that many people here have learned that the star Gliese 710 is likely on a collision course for dear old Sol system (thanks to Will Baird for the link).
Gliese 710, lying some 63 light years away from Earth at present, is a relatively dim orange dwarf of spectral type K7. As Sol Station notes, "The star may have about 0.4 to 0.6 (possibly 42 percent) of Sol's mass (García-Sánchez et al, 1999; and Weissman et al, 1997), possibly 67 percent of its diameter (Johnson and Wright, 1983, page 691), and only 4.2 percent of its visual luminosity. It is not a strong radio emitter. However, Gliese 710 is a variable star with the New Variable Star designation NSV 10635. Some other useful star catalogue designations include: Gl 710, Hip 89825, BD-01 3474, HD 168442, HD 168442, U449, and Vys/McC 63." The star, as Wikipedia notes, will be interesting.
A new set of star velocity data indicates that Gliese 710 has an 86 percent chance of ploughing into the Solar System within the next 1.5 million years.
The Solar System is surrounded by thousands of stars, but until recently it wasn't at all clear where they were all heading.
In 1997, however, astronomers published the Hipparcos Catalogue giving detailed position and velocity measurements of some 100,000 stars in our neighbourhood, all gathered by the European Space Agency's Hipparcos spacecraft. It's fair to say that the Hipparcos data has revolutionised our understanding of the 'hood.
In particular, this data allowed astronomers to work out which stars we'd been closer to in the past and which we will meet in the future. It turns out that 156 stars fall into this category and that the Sun has a close encounter with another star (meaning an approach within 1 parsec) every 2 million years or so.
In 2007, however, the Hipparcos data was revised and other measurements of star velocities have since become available. How do these numbers change the figures?
Today, Vadim Bobylev at the Pulkovo Astronomical Observatory in St Petersburg gives us the answer. He's combined the Hipparcos data with several new databases and found an additional nine stars that have either had a close encounter with the Sun or are going to.
But he's also made a spectacular prediction. The original Hipparcos data showed that an orange dwarf star called Gliese 710 is heading our way and will arrive sometime within the next 1.5 million years.
Of course, trajectories are difficult to calculate when the data is poor so nobody has really been sure about what's going to happen.
What the new data has allowed Bobylev to do is calculate the probability of Gliese 710 smashing into the Solar System. What he's found is a shock.
He says there is 86 percent chance that Gliese 710 will plough through the Oort Cloud of frozen stuff that extends some 0.5 parsecs into space.
That may sound like a graze but it is likely to have serious consequences. Such an approach would send an almighty shower of comets into the Solar System which will force us to keep our heads down for a while. And a probability of 86 percent is about as close to certainty as this kind of data can get.
Gliese 710, lying some 63 light years away from Earth at present, is a relatively dim orange dwarf of spectral type K7. As Sol Station notes, "The star may have about 0.4 to 0.6 (possibly 42 percent) of Sol's mass (García-Sánchez et al, 1999; and Weissman et al, 1997), possibly 67 percent of its diameter (Johnson and Wright, 1983, page 691), and only 4.2 percent of its visual luminosity. It is not a strong radio emitter. However, Gliese 710 is a variable star with the New Variable Star designation NSV 10635. Some other useful star catalogue designations include: Gl 710, Hip 89825, BD-01 3474, HD 168442, HD 168442, U449, and Vys/McC 63." The star, as Wikipedia notes, will be interesting.
[I]ts proper motion, distance, and radial velocity[3] indicate that it will approach within 1.1 light years (70,000 AU) from Earth within 1.4 million years, based on the latest Hipparcos data. At closest approach it will be a first-magnitude star about as bright as Antares. The proper motion of this star is very small for its distance, meaning it is traveling nearly directly in our line of sight; compare for example with Arcturus.
In a time interval of ±10 million years from the present, Gliese 710 is the star whose combination of mass and close approach distance will cause the greatest gravitational perturbation of our solar system. Specifically, it has the potential to perturb the Oort cloud enough to send a shower of comets into the inner solar system, possibly causing an impact event. However, recent dynamic models by García-Sánchez, et al. indicate that the net increase in cratering rate due to the passage of Gliese 710 will be no more than 5%. They estimate that the closest approach will happen in 1,360,000 years when the star will approach within 0.337 ± 0.177 pc (1.1 ly) of the Sun.[4]
