OGLE-2016-BLG-1190Lb – what the hell is that? It may look like some tricky password (definitely not very strong as there aren’t any special characters in it) but no – that is a cosmic object, literally! Yes, that’s the weird name astronomers have come up with and yes, they could have done better. Nonetheless, while we are screaming – ‘what the hell is that’, so are the astronomers.
OGLE-2016-BLG-1190Lb – Why does it confuse astronomers?
OGLE-2016-BLG-1190Lb is quite interesting. This celestial object is massive, so massive that astronomers are still pondering whether to call it a planet or a star.
Just how big is it? Well, OGLE-2016-BLG-1190Lb is 13.4 times more massive than the biggest planet in our Solar System, that is, Jupiter. A body of such massive size easily qualifies to be a Brown Dwarf (a type of star).
So, where’s the confusion? If it is that big to qualify as a Brown Dwarf, why don’t astronomers simply tag it as a Brown Dwarf?
Easier said that done! A celestial body can be classified as a Brown Dwarf if has a mass of anywhere between 13 MJ and 80 MJ where MJ refers to the mass of the Jupiter. The OGLE-2016-BLG-1190Lb has a mass of 13.4 MJ. This means that the OGLE-2016-BLG-1190Lb can be a Brown Dwarf.
However, there is a teeny-tiny problem. The problem is that OGLE-2016-BLG-1190Lb is orbiting a host star at a distance that falls in what is known as Brown Dwarf Desert.
What really is this Brown Dwarf Desert? It is basically a range of orbits around a host star on which, a Brown Dwarf cannot exist. The range of this Brown Dwarf Desert is 5 Astronomical Units (AU) around a star of mass same to the mass of our Sun.
So, if we say that there is a star called X which has one solar mass (denoted by M☉ where M☉ is the mass of our Sun), its Brown Dwarf Desert will have a radius of 5 AU. So, a Brown Dwarf cannot exist inside this radius or on the boundary of this radius.
Refer to the image below:
As per the image, the GRAY area shows the Brown Dwarf Desert and a Brown Dwarf star cannot sit inside the GRAY area or on the boundary of the GRAY area. It has to be outside the GRAY area.
Note that M☉ = (1.98855 ± 0.00025)×1030 kg.
1 AU = Average Distance Between Earth and Sun = ~150 million kilometers.
The problem is that OGLE-2016-BLG-1190Lb sits right at the edge the Brown Dwarf Desert! So, it cannot be a Brown Dwarf star.
Thus, the summary is:
- OGLE-2016-BLG-1190Lb is big enough to be classified as a Brown Dwarf and not a planet.
- It’s orbits at the edge Brown Dwarf Desert and hence, it should not qualify as a Brown Dwarf.
This precisely is the confusion among the astronomers. They cannot decide whether it is a star or a planet.
Some Info On OGLE-2016-BLG-1190Lb
- It orbits around a G-class host Yellow Dwarf Star. The mass of the host star is 0.89 M☉.
- OGLE-2016-BLG-1190Lb orbits the host star at a distance of 2AU (which is at the edge of the Brown Dwarf Desert in this case because the host star is small than our Sun and its Brown Dwarf Desert is smaller).
- The distance of the system (OGLE-2016-BLG-1190Lb and its host star) is 22,000 light years from our Earth.
- OGLE-2016-BLG-1190Lb takes 3 years to orbit around the host star.
- OGLE-2016-BLG-1190Lb is located right near the central bulge of our Milky Way.
What Does OGLE-2016-BLG-1190Lb Tell Us?
It tells us two things:
- If it is a planet, it has grown up to gigantic proportions and gives us an opportunity to understand how it happened.
- If it is a ‘Failed Star’ (a Brown Dwarf), it will help us understand how cosmic object turn into stars.
In this context:
What really is a Brown Dwarf and why is it called ‘Failed Star’?
A Brown Dwarf is a star which has a mass anywhere between 13 times the mass of Jupiter and 80 times the mass of Jupiter. It is big enough to generate heat within the range of 300°F and 400°F. However, it is not really massive enough to start nuclear fusion reaction it is core. Because it doesn’t have nuclear fusion reaction at its core (like normal stars have), it is called ‘Failed Star’.
About Discovery of OGLE-2016-BLG-1190Lb
Who Discovered OGLE-2016-BLG-1190Lb?
The OGLE-2016-BLG-1190Lb was discovered by an international team of researchers. The team lead was a Korean astronomer by the name Yoon-Hyun Ryu. The team found the celestial object from Korea Astronomy and Space Science Institute, located in Daejon, South Korea.
When and How Was OGLE-2016-BLG-1190Lb Discovered?
After they found it, the published their finding in a paper published in Arxiv.org. The discovery of the host star (OGLE-2016-BLG-1190L)was made in June 2016.
The object was found using a method known as Microlensing. It is a methods where distant objects are discovered by using stars behind them as flashlight. What really happens in Microlensing? Here is what happens:
- We stand on Earth and look far out at a distant star (let us call it STAR 1) which is pretty bright.
- A second star (let us call it STAR 2) comes between STAR 1 and Earth.
- The light from STAR 1 will then be bent and focused by gravitation of STAR 2. This will make STAR 1 appear brighter to us on Earth.
- If STAR 1 and STAR 2 align in a straight line, STAR 1 will appear even brighter.
- If STAR 2 has a planet orbiting it and it also aligns with STAR 1 and STAR 2, STAR 1 will become even brighter. This additional blip of brightness will tell us that there is a planet orbiting STAR 2.
This whole process is shown in the image below:
The method of Microlensing described above was used to identify OGLE-2016-BLG-1190Lb. The Microlensing effect of the host star OGLE-2016-BLG-1190L was observed by Optical Gravitational Lensing Experiment (OGLE) collaboration. OGLE is actually an astronomical project of Poland’s University of Warsaw. OGLE searches for extrasolar planets and dark matter. A 1.3 meter Warsaw Telescope mounted in Chile’s Las Campanas Observatory is used by OGLE. It is this Warsaw Telescope that found the host star.
A few days later, Spitzer Space Telescope of NASA observed the same event. The team of researchers studied the data from Spitzer and the Warsaw Telescope and found that Spitzer picked up a spike in Microlensing, confirming the presence of OGLE-2016-BLG-1190Lb (the planet or perhaps a Brown Dwarf).
OGLE-2016-BLG-1190Lb is the first Microlensing planet (if it is a planet) found by Spitzer in the vicinity of galactic bulge of Milky Way.
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