The newly identified star located within the yellow box of this image is half of a binary. Credit- ESO/BELETSKY/DSS1+DSS2+2MASS
We have found a star aging 13.5 billion years in binary system 2MASS J18082002–5104378 in the constellation Ara, about 1950 light years from Earth.
On the November 5th, 2018 Kevin C. Schlaufman, Ian B. Thompson, and Andrew R. Casey published a research to report the discovery of a low mass star on a circular orbit in a binary system with another small star.
They found a star with circular orbit with orbital period P = 34.757 ± 0.010 days in the ultra-metal-poor (UMP) single-lined spectroscopic binary system 2MASS J18082002–5104378, and is the oldest known star.
What it is?
Example of a binary star system (artist concept)
It is a star in an Ultra metal-poor (UMP) binary star system and single-lined spectroscopic binary. Single Spectroscopic binary means that in this star system two stars orbit around their common barycenter.
These star system to distant observers appear as a single point of light.
Which also happened in this case, the earlier astronomers who found the primary brighter star (2MASS J18082002–5104378A), identified unusual behavior and thought that a black hole or a neutron star may be the reason.
But Schlaufman’s team found fainter and smaller secondary star (2MASS J18082002–5104378B).
Primary star 2MASS J18082002–5104378A is a subgiant. With temperatures less than the Sun but larger and more luminous.
While Secondary star 2MASS J18082002–5104378B is a red dwarf. Its mass is around 0.14 times the mass of the Sun.
Where is this?
It is located in the Constellation Ara at a distance of around 1950 light year.
What makes it different?
Unlike other metal-poor stars, it is part of the “thin disk “of the Milky Way. It is the same part where the sun is located.
The star is billions of year older than the estimated age of the Milky Way’s thin disk.
It has the same heavy metal content as that of planet Mercury.
While our Sun has heavy element content equal to 14 Jupiter’s.
It has extremely low metallicity.
Astronomers call all elements which are heavier than Helium as ‘metals’.
Stars and nebulae with the relatively high abundance of carbon, nitrogen, oxygen, and neon are called “metal-rich”.
The metallic concentration of a star represents when it was formed.
In the young universe, there was an absence of heavy elements. Hydrogen and helium were in abundance. So older stars do not have heavier elements.
Our Sun is Population 1 star, being metal-rich. So what is the Stellar Population?
Let’s find out.
Populations of Stars-
Population I star Rigel with reflection nebula IC2118 (Source- Wikimedia)
1.Population 1 star-
·Have the highest metallicity out of three populations.
·Found in spiral arms of the Milky Way.
·Sun is population 1 stars.
·Have regular elliptical orbits of the galactic center.
·Higher metallic stars have a high probability of having gas giants as there planet.
2.Population 2 stars–
·Have relatively low metal content.
·These are formed during an earlier time of the universe.
·Found in the galactic halo. Also in the globular clusters.
·They may be the source of all other elements in the periodic table.
·They have a higher concentration of alpha elements like (O, Si, Ne, etc.).
Possible Glow of Population III stars imaged by NASA’s Spitzer Telescope
3.Population 3 stars
·With no metals
·Haven’t yet observed directly
·Inferred from physical cosmology
·Likely triggered a period of reionization.
·Such stars are likely to exist in the very early universe.
What its existence indicates?
Its discovery made to think that our galactic neighborhood can be 3 billion years older than previously thought.
Earlier it was believed that only massive stars could have formed in the early stages of Universe.
Therefore they couldn’t be observed because they burn their fuel and died quickly.
But the discovery of this old star indicates that these ancient stars could form from very small amounts of material.
So how it survived this long?
As we see it is pretty small (in stellar terms) and in Universe being small isn’t always bad.
Massive stars evolve quicker than light stars. Even though they have a larger amount of hydrogen for nuclear reactions, their rate of consuming fuel is very much greater. In order to remain stable via hydrostatic equilibrium, star’s luminosity increases with mass.
Sun compared to a red dwarf star
Red dwarf stars with fractions of the mass of the sun are thought to live trillions of years.
Kevin C. Schlaufman said that
“If our inference is correct, then low-mass stars that have a composition exclusively the outcome of the Big Bang can exist,”
How Early Stars Created Elements which make you?
Our world is made of elements formed deep within the core of stars of the early universe. As discussed in the previous post, in the early universe only hydrogen and helium was present.
A Star going Supernova (Credit -GIPHY)
As the early stars born with hydrogen and helium as their building block.
When star’s core runs out of fuel it contracts and heats up. When it reaches a temperature of about 100 million Kelvin, the helium fusion starts. Three helium atoms fuse together to create carbon, releasing energy in the process.
These heavy elements further fuse to give other heavier elements. Also, free neutrons are produced in these process which can combine to give further heavy elements.
These stars when go supernovae scatter this metal-enriched material all over the cosmos.
As Carl Sagan once said;
“The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.”
Where do you think this discovery could lead us? Write in the comments.