#microlensing

Sparkling Star May Indicate Galactic Composition - June 24th, 1998.

First ‘Earth Without A Sun’ Discovered: Thousands More To Be Revealed Soon

“Today, more than 4,000 exoplanets are known, revealed from their effects on the stars they orbit. But plenty of planets should have no parent stars at all. Perhaps surprisingly, these rogue planets should be extraordinarily common. Many young planets get ejected as solar systems form, creating “orphaned” planets. Others formed as members of insufficiently massive, failed solar systems. Altogether, rogue planets should outnumber the stars in our Milky Way.”

According to our best theories of how stars and planetary systems form, there should be an enormous number of planets without stars wandering through the galaxy, far outnumbering the stars themselves. But because they don’t emit their own light, these “rogue planets” should be completely invisible. Invisible doesn’t mean undetectable, however, as there is no hiding from gravity. 

A different perspective on our Galaxy

Planet Earth is a rocky world orbiting a small fairly commonplace G type yellow star, along with other planets. Over the last few decades, we’ve discovered other stars also have planetary systems, and while we are beginning to discover our planetary system is fairly unique in its makeup, 

Between the Stars, the void of interstellar space, once assumed to be light years of nothing, now almost certainly with the recent visit of interstellar asteroid ‘Oumuamua’ we know interstellar space is populated by a lot of debris moving around, so much so, it’s a serious concern for any future interstellar probes. 

But what about Rogue planets ? Free floating worlds with no star, probably ejected for their birth system ? In the 1960s, the theory that brown dwarfs could exist was proposed, but it was 30 years before we found any such failed star, today we are finding them everywhere we look. 

Part of the problem was, trying to find a brown dwarf that emits such low levels of energy due to the lack of fusion occurring in its core, meant we had to wait for detection technology to catch up and provide the evidence.

Rogue planets are even harder to spot, exo planets circling other stars are almost always given away by their impact on the host star, so with no host star, how can we spot them ? 

Gravity ! Planets have mass, and therefore a gravitational effect. When an object with large enough mass passes between a background star, it creates a lensing of the light from behind it. In that way, it is possible to potentially spot a planet as it passes between us and a star. 

The Roman telescope, slated to launch in the coming years, will be particularly looking for these micro-lensing events, there’s been many assumptive ones detected already, but earth based telescopes won’t have anywhere near the power of the space based telescopes, and will hopefully change the assumption to hard evidence. 

It’s suspected the milky way is full of rogue planets, and that may change the way we think about our near neighbourhood.

A newfound alien world is quite Earth-like in some ways, but you wouldn't want to live there.

The exoplanet, known as OGLE-2016-BLG-1195Lb, is about as massive as Earth and orbits its star at about the same distance Earth circles the sun. But OGLE-2016-BLG-1195Lb's parent star is tiny and dim, meaning the alien planet is likely far too cold to host life, its discoverers said.

OGLE-2016-BLG-1195Lb is not in Earth's neck of the cosmic woods; the alien world lies nearly 13,000 light-years away. The astronomers spotted it using a technique called gravitational microlensing, which involves watching what happens when a massive body passes in front of a star. The closer object's gravity bends and magnifies the background star's light, acting like a lens.

[...]

"This 'iceball' planet is the lowest-mass planet ever found through microlensing," Yossi Shvartzvald, a NASA postdoctoral fellow based at the agency's Jet Propulsion Laboratory (JPL) in Pasadena, California, said in a statement. Shvartzvald is lead author of the study announcing the new planet's existence, which was published online Wednesday (April 26) in the Astrophysical Journal Letters. (You can read the paper for free at the journal's website.)

The team was also able to determine that OGLE-2016-BLG-1195Lb's host star is tiny, containing just 7.8 percent the mass of Earth's sun.

That's so small that the parent may not be a proper star at all, researchers said: Its mass is right on the boundary between the "failed stars" known as brown dwarfs and ultracool dwarf stars such as TRAPPIST-1, which hosts seven recently discovered Earth-size planets.

A chance event reveals a frigid oddball planet

The Earth-sized world is the smallest planet ever seen through microlensing.

Things are cold on OGLE-2016-BLG-1195Lb, but to astronomers, its discovery is red hot. That’s because it is the smallest planet ever detected through gravitational microlensing, a quirk of physics that briefly makes distant objects appear brighter when a massive object passes between it and Earth.

NASA made the announcement of its discovery today. (A preprint of the paper is available here.) Using data from the Spitzer Space Telescope, the team led by Ian Bond of Massey University found the Earth-size world at a distance from its parent star similar to that of Earth. Don’t pack up your bags quite yet though: the planet orbits a tiny M-dwarf star, and would be far too frigid to harbor life as we know it. Temperatures are believed to be around -400 degrees F (-240 degrees C). That makes the planet about as cold as Pluto.

Read more ~ Astronomy Magazine