An Unknown Planet?

The binary stars Alpha Centauri A and Alpha Centauri B, and in the background the faint red dwarf Alpha Centauri C, also known as Proxima Centauri.

Astronomers have glimpsed what seems to be an unknown planet. In Nature Communications, the research team describes how infrared observations for 100 hours in May and June 2019 revealed a bright dot they have been unable to explain. If confirmed as a planet, the sighting would be the first to directly image an exoplanet around a nearby star.

Scientists spotted the bright dot near Alpha Centauri A, the closest star system to the Earth. It appears to be one of a pair of stars that swing around each other so tightly they appear to be a single star in the southern constellation of Centaurus. The binary star system is 4.37 light years away, a relatively short distance given the expanse of the cosmos. 

The researchers are referring to it as a “planet candidate” until further observations can verify the sighting.

The astronomers used the Very Large Telescope, or VLT, operated by the European Southern Observatory located in Chile’s Atacama Desert. A new coronagraph on the instrument blocks light from Alpha Centauri, making it easier to spot orbiting worlds.

Pete Klupar, the chief engineer of the Breakthrough Initiatives, said,“We’re trying to see a flashlight right next to a lighthouse.”

Read more here.

New Earth-Like Planets Studied

An international research team led by the University of Göttingen has discovered two new Earth-like planets near one of our closest neighboring stars. "Teegarden's star" is only about 12.5 light years away from Earth and is one of the smallest known stars. It is only about 2,700 °C warm and about ten times lighter than the Sun. Although it is so close to us, the star wasn't discovered until 2003. The scientists observed the star for about three years. The results were published in the journal Astronomy and Astrophysics.

Their data clearly show the existence of two planets. "The two planets resemble the inner planets of our solar system," explains lead author Mathias Zechmeister of the Institute for Astrophysics at the University of Göttingen. "They are only slightly heavier than Earth and are located in the so-called habitable zone, where water can be present in liquid form."

Read the Science Daily report here.

CARMENES Telescope Used

Despite its proximity, this nearby Teegarden's star was only discovered back in 2003. About ten times lighter than our own Sun and one of the smallest stars we know of, the old red dwarf, which is roughly 8 billion years old, has proved a challenge to research.

According to the team, other planetary systems around similar stars have always been detected using the transit method, when an orbiting planet passes in front of a star, blocking Earth's view and causing the bright celestial object to darken for a brief moment.

The alignment and dimness of Teegarden wouldn't lend itself to this method however, so astronomers instead used the CARMENES next-generation telescope designed specifically for such situations. Located at Spain's Calar Alto Observatory, the instrument allowed the researchers to look for any changes in the mini-star's radial velocity.

Read the Science Alert report here.

Related reading:  (Astronomy and Astrophsics Manuscript) The CARMENES search for exoplanets around M dwarfs: Two temperate Earth-mass planet candidates around Teegarden’s Star?; Finding Exoplanets; The Trappist-1 System

Finding Exoplanets

An artist's rendering of Kepler-34b, an exoplanet believed to orbit two stars. 

Credit: David A. Aguilar, Harvard-Smithsonian Centre for Astrophysics

It has been 85 years since the discovery of the planet Pluto, and astronomers want to find a new planet by looking for a pulsar. A pulsar is a highly magnetized, rotating neutron star or white dwarf, that emits a beam of electromagnetic radiation.

By carefully observing the light from a distant star, astronomers can detect the changes in the wavelengths of light called redshifting and blueshifting. They detect an exoplanet by observing over years the orbital wobble the occurs due to gravitation pull between the planet and the star.

An instrument called HARPS-North helps NASA's planet-scouting Kepler spacecraft confirm new planets.This spectrograph detects the tiny radial velocity signal induced by planets if they orbit close to their star.

"HARPS" stands for "High-Accuracy Radial velocity Planet Searcher." A spectrograph splits the light from a star into its wavelengths or colors, similar to the way a prism splits wavelengths and produces a colorful array. Chemical elements absorb light of specific colors, leaving dark lines in the star's spectrum. Those lines wobble slightly due to the gravitational tug of an orbiting planet on its parent star.

There are 5 ways to find an exoplanet. They are described in this NASA presentation.


Related reading: The TRAPPIST-1 System