Star Dates | by Brian Koberlein



10 April 2014

The Eskimo nebula.
NASA, ESA, Andrew Fruchter (STScI), and the ERO crew (STScI + ST-ECF)
The Eskimo nebula.

Figuring out the age of a star poses a little bit of a problem for astronomers. In spite of everything, stars exist over a timescale of billions of years, and they’re mild years away. We are able to’t use radiometric courting like we do for rocks and different objects on Earth. So simply how will we decide the age of a star? It seems that there are a number of methods, and it’s getting simpler to do.

One of many methods is to check a star’s mass with its brightness (absolute magnitude). We are able to decide the mass of a star whether it is a part of a binary system, and if we now have a great measure of its distance (say, by way of its parallax) then we are able to observe its obvious magnitude and use its distance to find out its absolute magnitude. The way in which we decide its age is by recognizing that essential sequence stars develop hotter and brighter over time. Stars produce mild and warmth by way of nuclear fusion of their core. As extra hydrogen fuses into helium, the fusion charges progressively improve, producing extra warmth and light-weight. So for stars of a selected mass, brighter stars are older than dimmer stars. By observing stars which can be newly fashioned and stars on the finish of their life we now have an concept of the speed at which stars brighten over time, so we are able to get a measure of a star’s age.

One other method is to measure a star’s fee of rotation. For stars round a photo voltaic mass or much less, the speed of rotation of a star progressively decreases. So the rotation fee of a star relies upon upon its mass and age. By measuring the rotation of a star and evaluating it to the rotation of the Solar (for which we all know its age very nicely), we are able to decide its age.

There are just a few downsides with these age measurements. For one, they solely work with essential sequence stars, so very younger and really previous stars must be studied with completely different measures. For an additional, they rely upon measurements which have historically been difficult to do nicely. However a brand new technique offered within the Astrophysical Journal might present a neater and simpler solution to decide stellar ages.

The tactic makes use of what is named helioseismology, which is the examine of sonic oscillations inside a star. Helioseismology has lengthy been used to review the inside construction of the Solar, however extra just lately it can be used with stars. For the reason that frequency of sound oscillations relies upon upon the mass and density of a star, helioseismology can be utilized to find out the mass and radius of a star fairly successfully. Realizing that, one can use observations of a star’s spectrum to find out its temperature. The mass, radius and temperature of a star can then be used to find out its age.

What makes this new technique doubtlessly highly effective is that it relies upon upon the kind of observational information gathered by sky surveys. This preliminary examine checked out a few thousand stars. A bigger venture often known as the Stroemgren survey for Asteroseismology and Galactic Archaeology (SAGA) is analyzing information gathered by the Kepler telescope. Future observations by telescopes corresponding to GAIA might present a big survey of stellar ages inside our galaxy.

The rationale why that is vital is that understanding the age of a lot of stars permits us to review the historical past of our galaxy. By analyzing stellar ages, we are able to decide when star manufacturing was frequent, and when it was uncommon. We would even have the ability to decide previous collisions with our galaxy, which are inclined to drive star manufacturing. This new technique continues to be younger, so it should take time to find out if it lives as much as its potential. But when it does we could quickly achieve deeper understanding of the historical past of our galaxy.

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