For the first time ever, astronomers have observed a galaxy in its initial phase of development. The discovery of a massive galaxy, dubbed "Sparky," reveals a dense galactic core that's producing new stars at a ferocious rate.
Artistic impression: NASA, Z. Levay, G. Bacon (STScI)
The galaxy, which is being observed a mere three billion years after the Big Bang, is only a fraction of the size of the Milky Way. But its galactic core already contains twice as many stars as our own galaxy — and all packed into a region only 6,000 light-years across (our galaxy extends for 100,000 light-years). Sparky is producing about 300 stars per year (hence its name), compared to the 10 stars per year produced by the Milky Way.
The observation strengthens the current theory about elliptical galaxy formation; a fully developed elliptical galaxy is a gas-deficient gathering of ancient stars that develops from the inside out, with a compact core marking its beginnings.
"We really hadn't seen a formation process that could create things that are this dense," explained lead author Erica Nelson of Yale University in a NASA statement. "We suspect that this core-formation process is a phenomenon unique to the early universe because the early universe, as a whole, was more compact. Today, the universe is so diffuse that it cannot create such objects anymore."
Sparky has been making stars for more than a billion years, but this frenzied pace will eventually slow to a stop. Over the next 10 billion years, other smaller galaxies may merge with it, causing it to expand and become an incredibly large, sedate elliptical galaxy.
The discovery was made by analyzing the combined observations from NASA's Hubble and Spitzer space telescopes, the W.M. Keck Observatory in Mauna Kea, Hawaii, and the European Space Agency's Herschel space observatory. These observational tools allowed the scientists to see the galaxy behind the massive walls of dust.
Read the entire study at Nature: "A Massive Galaxy in its Core Formation Phase Three Billion Years After the Big Bang".