Something massive and mysterious is lurking in our home galaxy’s bulge. Or is it one of the estimated 100-billion objects known as brown dwarfs roaming the Milky Way? In 2017, astronomers used the light-warping effects of gravity to spot a massive object OGLE-2016-BLG-1190Lb using NASA’s infrared Spitzer Space Telescope, 13 times the mass of Jupiter and orbits a star about 22,000 light years away. This discovery of an absolutely massive planet residing in our galaxy’s “bulge” (image above) has scientists struggling to explain if it’s a huge unknown planet or a failed star.
The object’s unusual mass suggests it may be a brown dwarf, sometimes called a “failed stars,” an objects so massive that it generates heat, though only in the range of about 300 to 400 degrees Fahrenheit, but not massive enough to sustain the nuclear fusion that powers main sequence stars.
“Every brown dwarf that has ever existed is still around today.” writes astrophysicist and The Daily Galaxy editor, Jackie Faherty. “The ones that are as old as the oldest stars, will have very little in The line between true planets and brown dwarfs is somewhere between 13 and 14 Jupiter masses, and with a mass of approximately 13.4 Jupiter masses. OGLE-2016-BLG-1190Lb their atmospheres since there were very few elements around when the first stars (and brown dwarfs) formed.”
Astronomers have noticed there’s a distinct lack of brown dwarfs within 5 AU (astronomical unit – the distance between the Earth and the Sun) of other stars. OGLE-2016-BLG-1190Lb has an orbit approximately 5 AU from its companion star that takes about three years to complete. If it is a planet, it’s grown to mammoth proportions.
“Since the existence of the brown dwarf desert is the signature of different formation mechanisms for stars and planets, the extremely close proximity of OGLE-2016-BLG-1190Lb to this desert raises the question of whether it is truly a ‘planet’ (by formation mechanism) and therefore reacts back upon its role tracing the galactic distribution of planets,” the researchers observed.
GLE-2016-BLG-1190Lb, is the first Spitzer detection using the microlensing technique of an exoworld residing in the galactic bulge. The finding was published in the Astronomical Journal in January 2018.
OGLE-2016-BLG-1190 was discovered in June 2016 as a microlensing event by the Optical Gravitational Lensing Experiment (OGLE) collaboration. OGLE is a Polish astronomical project based at the University of Warsaw, searching for dark matter and extrasolar planets. It utilizes the 1.3 meter Warsaw telescope mounted at the Las Campanas observatory in Chile.
Spitzer observed this microlensing event a few days after its discovery. An international team of researchers led by Yoon-Hyun Ryu of the Korea Astronomy and Space Science Institute in Daejon, South Korea, reports that these Spitzer observations detected a new, massive planet orbiting a dwarf star.
“We report the discovery of OGLE-2016-BLG-1190Lb, which is likely to be the first Spitzer microlensing planet in the galactic bulge/bar, an assignation that can be confirmed by two epochs of high-resolution imaging of the combined source-lens baseline object,” the astronomers wrote in the paper.
Image credit top of page: NASA/ Q.D. Wang. An “unprecedented” view of the galactic center using data from two such telescopes — NASA’s Chandra X-ray Observatory and the MeerKAT radio telescope in South Africa.