- 3968 -
EXOPLANETS - discovering planets around stars? Scientists have discovered more than 4,000
alien planets since spotting the first ones orbiting a star beyond our sun back
in 1992.
-
------------ 3968 - EXOPLANETS - discovering planets around stars?
- The
exoplanet HIP 99770 b , is seen circling its host star in these images by
Japan's Subaru Telescope. Data from Europe’s star-mapping Gaia spacecraft
revealed the likely presence of a big exoplanet in this system. Astronomers have directly detected and imaged
a gas giant orbiting another star by combining different techniques for hunting
exoplanets.
-
- Star-mapping
data combined from the European Space Agency’s (ESA) “Gaia” and older
“Hipparcos” missions to identify stars that, based on their apparent movements
or wobbles, are likely to be orbited by giant planets.
-
-
Observations using the telescope’s coronagraphic adaptive optics and
spectrograph instruments in July and September 2020 and May and October 2021
led to the discovery of the exoplanet HIP 99770B.
-
- HIP 99770B
is a gas giant planet about 15 times the mass of Jupiter orbiting the star HIP
99770, which is around twice as massive as our sun. Direct imaging provides information such as
the composition of atmospheres around planets and their temperatures.
-
- This
demonstrates that an indirect method sensitive to a planet’s gravitational pull
can tell you where to look and exactly when to look for direct imaging.
- “The
Transit Method”. This technique watches
for the tiny, telltale dips in a star's brightness caused when a planet crosses
(or transits) the star's face, blocking some of its light. NASA's Kepler
spacecraft has employed this method to great effect, spotting more than 2,700
potential planets since its March 2009 launch.
-
- Astronomers
also look for variations in the timing of a particular planet's transit,
because these can reveal the presence of additional worlds orbiting the same
star.
-
- “The radial
velocity method” picks up on the tiny wobbles an orbiting planet induces in its
parent's star's motion toward or away from Earth. This technique is also known
as the Doppler method because it measures shifts in the star's light caused by
these gravitational tugs.
-
- Several
teams of astronomers have discovered many exoplanets using this method and such
Earth-based instruments as the HARPS spectrograph, on a telescope at the
European Southern Observatory's La Silla Observatory in Chile, and the HIRES
spectrograph, on Hawaii's Keck telescope.
-
-
“Gravitational Microlensing” , astronomers watch what happens when a
massive object passes in front of a star from our perspective on Earth. The
nearby object's gravitational field bends and magnifies the light from the
distant star, acting like a lens.
-
- This
produces a light curve, a brightening
and fading of the faraway star's light over time, whose characteristics tell
astronomers a lot about the foreground object, which is often a star. If this
star has any planets, these can generate secondary light curves, alerting
researchers to their presence.
-
-
Gravitational microlensing is less biased toward planets that orbit
relatively far from their stars than the transit or radial velocity methods. Researchers
have even used it to find so-called "rogue planets," which cruise
through the depths of space without a parent star.
-
- Direct
Imaging. Powerful telescopes get actual
images of distant worlds, using instruments called coronagraphs to block out
the overwhelming glare of their parent stars.
NASA's Hubble Space Telescope has spotted planets by direct imaging, as
have Hawaii's Keck Observatory, the European Southern Observatory's Very Large
Array in Chile and several other telescopes.
-
- Pulsar
Timing, is specific to planets around
pulsars, tiny, superdense remnants of exploded stars that emit radio waves at
regular intervals as they rotate.
Anomalies in the timing of these radio pulses can reveal the presence of
orbiting planets. The first worlds ever discovered beyond our solar system were
found using this method back in 1992.
-
- Harnessing
Special Relativity, in this new technique, astronomers watch for a star to
brighten as it's tugged by an orbiting planet, causing photons to "pile up"
in energy and light to be focused in the direction of the star's motion due to
relativistic effects.
-
- The planet
Kepler-76b (also known as "Einstein's planet") was discovered via
this method, then confirmed by radial velocity measurements. Astrometry relies
on the ultraprecise tracking of a star's movements on the sky to spot the
gravitational tugs of orbiting planets. (It's similar in principle to the
radial velocity method but doesn't measure the Doppler shifts in a star's
light.)
-
- Scientists
have searched for alien planets using astrometry for decades, with very limited
(and debatable) success. But the European Space Agency's Gaia mission, set to
launch in October 2013, could spot tens of thousands of exoplanets using the
technique.
-
April 21, 2023 EXOPLANETS
- discoverring planets around
stars? 3968
----------------------------------------------------------------------------------------
----- Comments
appreciated and Pass it on to whomever is interested. ---
--- Some
reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email
feedback, corrections, request for copies or Index of all reviews
--- to: ------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- --- Friday, April 21, 2023
---------------------------
-
No comments:
Post a Comment