Purest, Most Massive Brown Dwarf

The article, “Astronomers identify purest, most massive brown dwarf,” explains that brown dwarfs are intermediate between planets and fully-fledged stars. Their mass is too small for full nuclear fusion of hydrogen to helium to take place, but they’re usually significantly larger than planets. An international team of astronomers has identified a record breaking brown dwarf with the “purest” composition and highest mass yet known. It is located 750 light years away in the constellation of Pisces, and is made up of gas that’s around 250 times purer than the Sun. This means it consists of more than 99.99% hydrogen and helium. Measurements suggest it has a mass that’s 90 times that of Jupiter. The discovery points the way to a larger undiscovered population of extremely pure brown dwarfs from our galaxies ancient past.

Our conceptual objective was to be able to explain how astronomers use the Hertzsprung-Russell diagram to study properties of stars. An H-R diagram plots stars according to their surface temperatures (or spectral types) and luminosities. The horizontal axis of the H-R diagram represents temperature which correlates with spectral type. The vertical axis represents luminosity which correlates with absolute magnitude. Stars spend most of their lives fusing hydrogen into helium in their cores, and stars in this stage of life are found on the main sequence. The power point slides in class taught us that most stars are on the main sequence and their size is related to temperature and luminosity. The more massive main sequence stars are more luminous, larger, and hotter. There are also giants and white dwarf stars which are not on the main sequence. Giants are bright and large to the upper right of the main sequence. White dwarfs are hot and small, located to the lower left of the main sequence. This article discusses brown dwarfs which are neither planets nor stars. However, the textbook states that the sequence of spectral types has recently been extended further than type M to include spectral types L and T, representing starlike objects, such as brown dwarfs, which are even cooler than stars of spectral type M (p. 314). According to this information, if brown dwarfs were to be added to the H-R diagram and it were extended to spectral types L and T, they would likely be to the lower right portion below the lowest main sequence stars because of their cool temperature and small size.

I was intrigued by this article because I did not know anything about brown dwarfs and it had lots of good information about them. I found it very interesting that they are much larger than planets but too small to be stars. I also liked this article because even though brown dwarfs are not technically stars I felt that they still relate to this objective because they have many similarities and can be applied to the H-R diagram.


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