Newly Discovered 'Ice Planet' --"Helps NASA Understand Distribution of Planets in Milky
Way's Disk vs Center"
Scientists have discovered a new planet with the mass of Earth, orbiting its star at the
same distance that we orbit our sun.
The planet is likely far too cold to be habitable for life as we know it, however, because its
star is so faint.
But the discovery adds to scientists' understanding of the types of planetary systems that exist
beyond our own.
"Although we only have a handful of planetary systems with well-determined distances that
are this far outside our solar system, the lack of Spitzer detections in the bulge suggests
that planets may be less common toward the center of our galaxy than in the disk," said
Geoff Bryden, astronomer at JPL and co-author of the study.
"This 'iceball' planet is the lowest-mass planet ever found through microlensing," said
Yossi Shvartzvald, a NASA postdoctoral fellow based at NASA's Jet Propulsion Laboratory,
Pasadena, California, and lead author of a study published in the Astrophysical Journal
Letters.
Microlensing is a technique that facilitates the discovery of distant objects by using
background stars as flashlights.
When a star crosses precisely in front of a bright star in the background, the gravity
of the foreground star focuses the light of the background star, making it appear brighter.
A planet orbiting the foreground object may cause an additional blip in the star's brightness.
In this case, the blip only lasted a few hours.
This technique has found the most distant known exoplanets from Earth, and can detect
low-mass planets that are substantially farther from their stars than Earth is from our sun.
The newly discovered planet, called OGLE-2016-BLG-1195Lb, aids scientists in their quest to figure out
the distribution of planets in our galaxy.
An open question is whether there is a difference in the frequency of planets in the Milky Way's
central bulge compared to its disk, the pancake-like region surrounding the bulge.
OGLE-2016-BLG-1195Lb is located in the disk, as are two planets previously detected through
microlensing by NASA's Spitzer Space Telescope.
For the new study, researchers were alerted to the initial microlensing event by the ground-based
Optical Gravitational Lensing Experiment (OGLE) survey, managed by the University of Warsaw
in Poland.
Study authors used the Korea Microlensing Telescope Network (KMTNet), operated by the
Korea Astronomy and Space Science Institute, and Spitzer, to track the event from Earth
and space.
KMTNet consists of three wide-field telescopes: one in Chile, one in Australia, and one in
South Africa.
When scientists from the Spitzer team received the OGLE alert, they realized the potential
for a planetary discovery.
The microlensing event alert was only a couple of hours before Spitzer's targets for the
week were to be finalized, but it made the cut.
With both KMTNet and Spitzer observing the event, scientists had two vantage points from
which to study the objects involved, as though two eyes separated by a great distance were
viewing it.
Having data from these two perspectives allowed them to detect the planet with KMTNet and
calculate the mass of the star and the planet using Spitzer data.
"We are able to know details about this planet because of the synergy between KMTNet and
Spitzer," said Andrew Gould, professor emeritus of astronomy at Ohio State University, Columbus,
and study co-author.
Although OGLE-2016-BLG-1195Lb is about the same mass as Earth, and the same distance
from its host star as our planet is from our sun, the similarities may end there.
OGLE-2016-BLG-1195Lb is nearly 13,000 light-years away and orbits a star so small, scientists
aren't sure if it's a star at all.
It could be a brown dwarf, a star-like object whose core is not hot enough to generate energy
through nuclear fusion.
This particular star is only 7.8 percent the mass of our sun, right on the border between
being a star and not.
Alternatively, it could be an ultra-cool dwarf star much like TRAPPIST-1, which Spitzer and
ground-based telescopes recently revealed to host seven Earth-size planets.
Those seven planets all huddle closely around TRAPPIST-1, even closer than Mercury orbits
our sun, and they all have potential for liquid water.
But OGLE-2016-BLG-1195Lb, at the sun-Earth distance from a very faint star, would be
extremely cold�likely even colder than Pluto is in our own solar system, such that any
surface water would be frozen.
A planet would need to orbit much closer to the tiny, faint star to receive enough light
to maintain liquid water on its surface.
Ground-based telescopes available today are not able to find smaller planets than this
one using the microlensing method.
A highly sensitive space telescope would be needed to spot smaller bodies in microlensing
events.
NASA's upcoming Wide Field Infrared Survey Telescope (WFIRST), planned for launch in
the mid-2020s, will have this capability.
"One of the problems with estimating how many planets like this are out there is that we
have reached the lower limit of planet masses that we can currently detect with microlensing,"
Shvartzvald said.
"WFIRST will be able to change that."
The Daily Galaxy via Jet Propulsion Laboratory
Không có nhận xét nào:
Đăng nhận xét