According to Phys.org, Astronomers have made an interesting new discovery — a gas giant orbiting a brown dwarf. The exoplanet has been dubbed OGLE-2017-BLG-1522Lb. The newly discovered gaseous body has about 25% less mass than Jupiter, while its parent pseudo-star is about 46 times more massive than our own Jove.

Exoplanets are already pretty tough to spot. Unlike stars, planets don’t naturally give off any light, which means that scientists have to get a little creative when looking for them. Often they use something called the “Transit Method” wherein they follow a star as it crosses in front of its parents light, and watch how and where the image dims to get a rough estimate of its properties.

But this one was a bit different. Here, researchers used gravitational microlensing. Because gravity isn’t really a force, as Einstein demonstrated, but a curvature of space-time, in the same way a lens can be used to magnify an image, gravity can be used to accomplish the same. This technique requires solid understanding of the masses in the system being studied, but it’s extraordinarily effective and quite useful to spot a planet near a brown dwarf — which emit very little light naturally.

OGLE-2017-BLG-1522 was observed in August of last year as part of the Optical Gravitational Lensing Experiment (OGLE). The team used one of the telescopes at the Las Campanas Observatory in Chile, and, following the data collection, an international team of astronomers analyzed the data and found that the system likely had a brown dwarf and a gas giant.

“We report the discovery of a giant planet in the OGLE-2017-BLG-1522 microlensing event. The planetary perturbations were clearly identified by high-cadence survey experiments despite the relatively short event timescale of tE ~ 7.5 days,” the researchers wrote.

What matters here is that brown dwarfs aren’t generally thought to have the kind of nebulae that cause planet formation. There is a boundary, known as the “snow line,” past which planets tend to form. And while the astrophysics behind that gets a little complicated, these astronomers are fairly confident that their discovery is the first giant planet orbiting a brown dwarf with the right proportions. More observations will need to be made to confirm that the star is, indeed, brown, i.e. it doesn’t have enough mass to sustain hydrogen fusion in its core. If so, this could be a major new addition to our understanding of astrophysics and how planets form.

Let us know what you like about Geek by taking our survey. </s> Light curve of OGLE-2017-BLG-1522. Credit: Jung et al., 2018.

Using microlensing technique, astronomers have found a new giant planet orbiting a brown dwarf located in the bulge of the Milky Way galaxy. The newly discovered exoplanet, designated OGLE-2017-BLG-1522Lb, is most likely 25 percent less massive than Jupiter. The finding is reported March 14 in a paper published on arXiv.org.

Based on the gravitational lens effect, the microlensing method is mainly used to detect planetary and stellar-mass objects regardless of the light they emit. This technique is therefore sensitive to the mass of the objects, especially to low-mass planets orbiting beyond the so-called "snow line" around relatively faint host stars like M dwarfs or brown dwarfs. Such planets are of special interest for astronomers, as just beyond this line, the most active planet formation occurs.

The OGLE-2017-BLG-1522 microlensing event was detected August 7, 2017 by the Optical Gravitational Lensing Experiment (OGLE) using the 1.3m Warsaw telescope at the Las Campanas Observatory in Chile. Afterward, an international team of astronomers, including scientists from the OGLE Collaboration and the Korea Microlensing Telescope Network (KMTNet) Collaboration, has analyzed the event and found a system composed of a brown dwarf orbited by a giant planet.

"We report the discovery of a giant planet in the OGLE-2017-BLG-1522 microlensing event. The planetary perturbations were clearly identified by high-cadence survey experiments despite the relatively short event timescale of t E ~ 7.5 days," the researchers wrote in the paper.

According to the study, OGLE-2017-BLG-1522Lb is a giant planet with a mass of about 0.75 Jupiter masses, orbiting its host at a distance of about 0.59 AU. The researchers noted that they are 75 percent sure that the host is a brown dwarf approximately 46 times more massive than our solar system's biggest planet. Therefore, additional observations should be conducted in order to definitely confirm whether the host is a low-mass star or a an intermediate-mass brown dwarf.

The projected companion-host separation indicates that OGLE-2017-BLG-1522Lb is placed beyond the snow line—the distance at which molecular species freeze, thus where the planet formation starts. Moreover, the authors of the paper calculated that the system is located in the galactic bulge.

In concluding remarks, the astronomers underlined the importance of their discovery, noting that OGLE-2017-BLG-1522Lb could be the first giant planet orbiting around a brown dwarf host having a planetary mass ratio.

"Planet formation scenarios combined with the small companion-host mass ratio q ∼ 0.016 and separation suggest that the companion could be the first discovery of a giant planet that formed in a protoplanetary disk around a brown dwarf host," the scientists concluded.

Explore further Extremely massive exoplanet discovered in the Milky Way's bulge

More information: OGLE-2017-BLG-1522: A giant planet around a brown dwarf located in the Galactic bulge, arXiv:1803.05095 [astro-ph.EP] OGLE-2017-BLG-1522: A giant planet around a brown dwarf located in the Galactic bulge, arXiv:1803.05095 [astro-ph.EP] arxiv.org/abs/1803.05095 Abstract

We report the discovery of a giant planet in the OGLE-2017-BLG-1522 microlensing event. The planetary perturbations were clearly identified by high-cadence survey experiments despite the relatively short event timescale of tE∼7.5 days. The Einstein radius is unusually small, θE=0.065mas, implying that the lens system either has very low mass or lies much closer to the microlensed source than the Sun, or both. A Bayesian analysis yields component masses (Mhost,Mplanet)=(46+79−25,0.75+1.26−0.40) MJ and source-lens distance DLS=0.99+0.91−0.54 kpc, implying that this is a brown-dwarf/Jupiter system that probably lies in the Galactic bulge, a location that is also consistent with the relatively low lens-source relative proper motion μ=3.2±0.5 mas yr−1. The projected companion-host separation is 0.59+0.12−0.11 AU, indicating that the planet is placed beyond the snow line of the host, i.e., asl∼0.12 AU. Planet formation scenarios combined with the small companion-host mass ratio q∼0.016 and separation suggest that the companion could be the first discovery of a giant planet that formed in a protoplanetary disk around a brown dwarf host.

© 2018 Phys.org </s> Scientists have discovered a planet a lot like Jupiter orbiting a dim star, if you can even call it a star—it’s nothing like our sun. The finding once again makes us wonder: what is a planet, anyway?

A team of researchers from two collaborations, KMTNet and the OGLE, or Optical Gravitational Lensing Experiment, announced their new planet-brown dwarf pair, calling it the “OGLE-2017-BLG-1522 microlensing event.” Brown dwarfs are either the lightest, dimmest stars or the heaviest, hottest planets. They have been spotted with companions before, but this would be largest mass difference between a brown dwarf and its companion yet, with the brown dwarf being perhaps over 60 times the size of the orbiting planet.

“OGLE-2017-BLG-1522Lb could be the first giant planet orbiting around a brown-dwarf host having a planetary mass ratio,” the authors write in the paper published on the arXiv preprint server.

That means that the planet could have formed from a ring of dust around the brown dwarf, rather than the two objects forming together as a sort of binary. “That’s the fundamental question,” Jennifer Yee, astrophysicist at the Harvard-Smithsonian Center for Astrophysics, told Gizmodo. “That’s why it’s important. We don’t know how you would form these things,” she said, referring to planets orbiting brown dwarfs.

The OGLE discovered the object on August 7, 2017, using their Warsaw telescope in Chile. Another network of telescopes in Chile, South Africa, and Korea, called the Korea Microlensing Telescope Network Survey, also monitored the event.

Essentially, the researchers saw another star, located behind the brown dwarf and planet, brighten in a characteristic pattern, one most likely due to the pair passing in front of it. The gravity from the closer objects would bend the light of the star behind them. The researchers attributed their results to a planet around three-quarters the mass of Jupiter orbiting a brown dwarf 46 or so times the mass of Jupiter. They calculated that the two are separated by about 0.6 times the distance between the Earth and the Sun.

This new paper hasn’t been published in its peer-reviewed form yet, and has some pretty large uncertainties; for example, the paper includes the line “the probability that the host is a brown dwarf is [approximately] 76%.” We’ll update this post with further comment when we hear back.



But the event brings up yet again the debate about what constitutes a “planet” and what doesn’t—a redefinition of the term planet stripped Pluto of its title, you might remember. It’s especially difficult to figure out the difference on the heavier end of things, though, when something is too big to be called a planet and just massive enough to become a star. How something forms is of crucial importance to understanding whether something is a planet or not, since planets tend to form from disks around stars, while stars form from the centers of the disks themselves.

Given the uncertainty, there’s still lots more research to be done, said Yee, since we can’t see the whole process from start to finish. “By finding a bunch of these thing, we can relate them back to the whole corse of their evolution,” she said. </s> UPDATE: A mistake about an exoplanet's exact position has been corrected

Astronomers have found over 4,000 planets in other star systems, but almost all of these "exoplanets" are massive compared to Earth. In fact, 96% of them are larger than Earth. Mostly, astronomers have found gas giants like Neptune or Jupiter, but very few small planets. So the announcement this week that 18 exoplanets have been discovered that fall into the broad category of Earth-sized planets is big news.

The even bigger news is that one of them is slightly smaller than our planet. Have we just found Earth 2.0?

What do we know about this planet?

The candidate for an "Earth twin" is called EPIC 201497682.03. It resides around a red dwarf star called EPIC 201497682 that’s 831 light years from our solar system between the constellations Leo and Virgo. It’s 69% of the size of the Earth, the closest fit in the 18 exoplanets found by scientists at the Max Planck Institute for Solar System Research (MPS), the Georg August University of Göttingen, and the Sonneberg Observatory, whose results have been published in Astronomy & Astrophysics.

What about its host star?

"EPIC” stands for “Ecliptic Planet Input Catalog”, which was a list of targets that the Kepler Space Telescope's K2 mission was supposed to observe. However, EPIC 201497682 is also known in other star catalogs as UCAC4 453-051784, 2MASS J11154478+0029171, and Gaia DR2 3810098271767907840. "When we look at the star now we see the light that emerged from this system about 300 years before Christopher Columbus reached The Americas," said Dr. Rene Heller from MPS, first author of the paper. "It’s quite compelling that we were able to find a rock just slightly larger than Mars around this remote star."

Why are small exoplanets hard to find?

Small planets are harder to track down than big ones. Exoplanet-hunters find their targets by detecting a drop in brightness as a planet travels (transits) in front of its host star. However, while large planets cause sudden drops in brightness that is easy to detect, small planets cause such a tiny change in brightness that it's hard to separate it from the natural brightness fluctuations of the star. "Standard search algorithms attempt to identify sudden drops in brightness," said Heller. "In reality, however, a stellar disk appears slightly darker at the edge than in the center. When a planet moves in front of a star, it therefore initially blocks less starlight than at the mid-time of the transit. The maximum dimming of the star occurs in the center of the transit just before the star becomes gradually brighter again," he said.

How were these new exoplanets found?

As well as the "sub-Earth" planet EPIC 201497682.03, the scientists found 17 planets slightly larger than Earth, all of them found in data from the Kepler Space Telescope using a new search algorithm called transit least-squares (TLS). "Our new algorithm helps to draw a more realistic picture of the exoplanet population in space," summarises Michael Hippke of Sonneberg Observatory. The new algorithm looks for gradual darkening, not the abrupt brightness drops that algorithms usually look for. This makes the new transit search algorithm significantly more sensitive to very small planets the size of the Earth. "This method constitutes a significant step forward, especially in the search for Earth-like planets,” said Hippke.

What is the Kepler Space Telescope?

The researchers used data from NASA’s Kepler Space Telescope as a test bed for their new algorithm. In its first mission phase from 2009 to 2013, Kepler recorded the light curves of more than 100,000 stars, resulting in the discovery of over 2,300 planets. After a technical defect, the telescope had to be used in an alternative observing mode, called the K2 mission, but it still managed to monitor more than 100,000 more stars by the end of the mission in 2018. The researchers decided to re-analyze all 517 stars from K2 that were already known to host at least one transiting planet.

Could these exoplanets be habitable?

Most of them are probably too hot. Most of the new planets detected in the old data orbit their star closer than other known planets. The surfaces of these new planets therefore likely have temperatures well in excess of 100ºC/212ºF, while some have temperatures of up to 1,000ºC/1,832ºF. Only one, a planet called EPIC 201238110.02, resides in the "habitable zone". "It's 1.87 Earth diameter in size, so it’s rather a super-Earth than an Earth twin," says Heller. The host star EPIC 201238110 is 522 light years from us, also between the constellations Leo and Virgo.

Can the new algorithm be used to find another Earth 2.0?

Given their discovery rate of 3.5% new planets in old data, the researchers think that their method will help them to find more than 100 other Earth-sized worlds in the Kepler data. “This new method is also particularly useful to prepare for the upcoming PLATO mission to be launched in 2026 by the European Space Agency,” says Professor Dr. Laurent Gizon, managing director at the MPS.

What is the PLATO mission?

Planned for launch by 2026, the PLATO (PLAnetary Transits and Oscillations of stars) mission will assemble the first-ever catalog of confirmed planets, including planets in the habitable zone of their host stars. It will study hundreds of rocky, icy and giant planets and accurately measure their radii, masses, and ages. It’s expected to revolutionize astronomers’ understanding of planet formation and the evolution of planetary systems. "Does a second Earth exist in the Universe? is one of the exciting questions in astrophysics today," says Johann-Dietrich Wörner, director general of ESA. "With our PLATO satellite, we are focusing on Earth-like planets orbiting up to the habitable zone around other stars which are similar to our Sun. This will be a major step towards finding another Earth."
ArXiv publishes research that a gas giant may be orbiting a brown dwarf. The exoplanet, designated OGLE-2017-BLG-1522Lb, orbits its host at a distance of 0.59 AU and could be the first known gas giant to have formed inside the protoplanetary disk of a brown dwarf.