Universe Today
As of
March 1st, 2018
, 3,741 exo
planets
have been confirmed in 2,794 systems, with 622 systems having more than one planet. Most of the credit for these discoveries goes to the
Kepler space telescope
, which has discovered roughly 3500 planets and 4500 planetary candidates. In the wake of all these discoveries, the focus has shifted from pure discovery to research and characterization.
In this respect, planets detected using the
Transit Method
are especially valuable since they allow for the study of these planets in detail. For example, a team of astronomers
recently discovered
three Super-Earths orbiting a star known GJ 9827, which is located just 100 light years (30 parsecs) from Earth. The proximity of the star, and the fact that it is orbited by multiple Super-Earths, makes this system ideal for detailed exoplanet studies.
The study, titled "
A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at Thirty Parsecs
", recently appeared online. The study was led by Joseph E. Rodriguez of the
Harvard-Smithsonian Center for Astrophysics
and included members from The University of Texas at Austin, Columbia University, the
Massachusetts Institute of Technology
, and the
NASA Exoplanet Science Institute
.
[caption id="attachment_135789" align="aligncenter" width="580"]
Artistic design of the super-Earth GJ 625 b and its star, GJ625 (Gliese 625). Credit: Gabriel Pérez/SMM (IAC)
[/caption]
As with all Kepler discoveries, these planets were discovered using the Transit Method (aka. Transit Photometry), where stars are monitored for periodic dips of brightness. These dips are the result of exoplanets passing in front of the star (i.e. transiting) relative to the observer. While this method is ideal for placing constraints on the size and orbital periods of a planet, it can also allow for exoplanet characterization.
Basically, scientists are able to learn things about their atmospheres by measuring the spectra produced by the star's light as it passes through the planet's atmosphere. Combined with radial velocity measurements of the star, scientists can also place constraints on the planet's mass and radius and can determine things about the planet's interior structure.
For the sake of their study, the team analyzed data obtained by the
K2
mission, which showed the presence of three Super-Earths around the star GJ 9827 (GJ 9827 b, c, and d). Since they initially submitted their research paper back in
September of 2017
, the presence of these planets has been confirmed by another team of astronomers. As Dr. Rodriguez told Universe Today via email:
[caption id="attachment_137883" align="aligncenter" width="580"]
The super-Earth exoplanet 55 Cancri e, depicted with its star in this artist's concept, likely has an atmosphere thicker than Earth's but with ingredients that could be similar to those of Earth's atmosphere. Credit: NASA/JPL
[/caption]
These three exoplanets are especially interesting because the larger of the two have radii that place them in the range between being rocky or gaseous. Few such exoplanets have been discovered so far, which makes these three a prime target for research. As Dr. Rodriguez explained:
Another interesting thing about these super-Earths is how their short orbital periods - which are 1.2, 3.6 and 6.2 days, respectively - would result in fairly hot temperatures. In short, the team estimates that the three super-Earths experience surface temperatures of 1172 K (899 °C; 1650 °F), 811 K (538 °C; 1000 °F), and 680 K (407 °C; 764 °F), respectively.
By comparison,
Venus
- the hottest planet in the Solar System - experiences surface temperatures of 735 K (462 °C; 863 °F). So while temperatures on Venus are hot enough to melt lead, conditions on GJ 9827 b are almost hot enough to melt bronze.
[caption id="attachment_137180" align="aligncenter" width="580"]
The light curve obtained during Campaign 12 of the K2 mission of the GJ 9827 system. Credit: Rodriguez et al., 2018.[/caption]
However, the most significant thing about this discovery is the opportunities it could provide for exoplanet characterization. At just 100 light-years from Earth, it will be relatively easy for the next-generation telescopes (such as the
James Webb Space Telescope
) to conduct studies of their atmospheres and provide a more detailed picture of this system of planets.
In addition, these three strange planets are all in the same system, which makes conducting observation campaigns that much easier. As Rodriguez concluded:
Further Reading: CfA
,
arXiv
