Short-period comets need roughly 200 years or less to complete one orbit, long-period comets take more than 200 years, and single-apparition comets are not bound to the sun, on orbits that take them out of the solar system, according to NASA.
Yes, you can invest in both an IRA and a 401k (or a Roth 401k and a Roth IRA) at the same time, or any combination of those accounts. And in some cases, based on the fees in your 401k, an IRA might actually be a better place to invest your money.
If your 401k plan doesn't provide the fund diversity that you want, investigate other options. Individuals are allowed to make IRA and 401k contributions in the same year, but they must follow specific IRS guidelines. There are many IRAs to choose from, including deductible IRAs, non-deductible IRAs and Roth IRAs.s of 2010, the IRA maximum you may contribute to any IRA is $5,000, or $6,000 if you're 50 or older. IRAs are at least partially-deductible if you earn less than $109,000 adjusted gross income if you're married and filing jointly, and less than $66,000 if you're single.