How old is the system

How old is the Solar System? That is a question that cuts to the heart of it all. By studying several things, mostly meteorites, and using radioactive dating techniques, specifically looking at daughter isotopes, scientists have determined that the Solar System is 4.

Well, give or take a few million years. That age can be extended to most of the objects and material in the Solar System. The basics of it are that all material radioactively decays into a stable isotope. Some elements decay within nanoseconds while others have projected half-lives of over billion years. A good guess, but a tricky one because Earth's surface is so dynamic.

The processes of plate tectonics have altered and recycled the Earth so much over it's history that the oldest known whole rock on the surface gets us to 4. That is really far back, but these rocks in Canada don't get us all the way back to where it all began.

The dates for these Canadian rocks are somewhat controversial, but there are a number other rocks that are around 4 billion years old. Rocks on the Moon, likely formed not long after the Earth during a massive collision with another early solar system object, date back to around 4.

So what about individual minerals? A whole package of rocks might not survive all the trials and tribulations of plate tectonics, but minerals that get recycled into younger rocks especially sedimentary rocks might preserve something even older than the Canadian rocks. But can we push it even further back? We might not have the record on the Earth, but certain meteorites are likely remnants of the first solid stuff to form from the solar nebula.

The Allende meteorite that fell in Mexico in has been dated to 4. It is a type of meteorite called a carbonaceous chondrite , just the sort of primeval material we think formed during the start of our solar system.

So, Allende gives us a good age for the Earth Getting at the timing of how long we went from debris in the nebula to a proper planet is still being actively researched, but studies looking at extinct isotopes elements whose decay rate means they don't exist in our solar system anymore suggest that it might have only taken a few tens of millions of years -- pretty short compared to the age of the solar system.

What about stuff that might be even older than that? This Murchinson meteorite takes us back even before the solar system may have formed! Looking at how isotopes of certain elements like neon formed on this dust, this new work by Philipp Heck and others determine that the dust in the Murchinson meteorite might be up to 3. That makes them potentially 7 billion years old!

This dust is the remnants of other stars that pre-date our Sun, but they are some of the first evidence of the material that was around our neck of the galaxy long before the Sun started to shine. How far back can we conceivably get? This is a question without an answer at this time. Astronomers, looking at stars in other galaxies to peer back into the history of the universe, suggest that our galaxy is around This isn't the same kind of date as Earth scientists have collected -- there is no solid material that we're examining and measuring.

However, it does leave the window open for the discovery of stuff even older than the 7 billion-year-old dust of the Murchinson meteorite. Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.

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Cosmologists use this measurement to extrapolate back to the Big Bang. This extrapolation depends on the history of the expansion rate which in turn depends on the current density of the universe and on the composition of the universe. If the universe is flat and composed mostly of matter, then the age of the universe is.

If the universe contains a form of matter similar to the cosmological constant , then the inferred age can be even larger. Many astronomers are working hard to measure the Hubble constant using a variety of different techniques. If we compare the two age determinations, there is a potential crisis. If the universe is flat, and dominated by ordinary or dark matter, the age of the universe as inferred from the Hubble constant would be about 9 billion years.

The age of the universe would be shorter than the age of oldest stars. This contradiction implies that either 1 our measurement of the Hubble constant is incorrect, 2 the Big Bang theory is incorrect or 3 that we need a form of matter like a cosmological constant that implies an older age for a given observed expansion rate.

Some astronomers believe that this crisis will pass as soon as measurements improve. If the astronomers who have measured the smaller values of the Hubble constant are correct, and if the smaller estimates of globular cluster ages are also correct, then all is well for the Big Bang theory, even without a cosmological constant. Measurements by the WMAP satellite can help determine the age of the universe. The detailed structure of the cosmic microwave background fluctuations depends on the current density of the universe, the composition of the universe and its expansion rate.

As of , WMAP determined these parameters with an accuracy of better than than 1. In turn, knowing the composition with this precision, we can estimate the age of the universe to about 0. How does WMAP data enable us to determine the age of the universe is The key to this is that by knowing the composition of matter and energy density in the universe, we can use Einstein's General Relativity to compute how fast the universe has been expanding in the past.

With that information, we can turn the clock back and determine when the universe had "zero" size, according to Einstein. The time between then and now is the age of the universe.