Precise Measurements of Nearest Earth-Sized Exoplanet

Breakthrough measurements of exoplanet Proxima B were made with radial velocity measurements of unprecedented precision using ESPRESSO, the Swiss-manufactured spectrograph – the most accurate currently in operation – which is installed on the Very Large Telescope in Chile. Proxima b was first detected four years ago by means of an older spectrograph, HARPS – also developed by the Geneva-based team – which measured a low disturbance in the star’s speed, suggesting the presence of a companion.

Above – This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. © ESO/M. Kornmesser

The ESPRESSO spectrograph has performed radial velocity measurements on the star Proxima Centauri, which is only 4.2 light-years from the Sun, with an accuracy of 30 centimetres a second (cm/s) or about three times more precise than that obtained with HARPS, the same type of instrument but from the previous generation.

ESPRESSO has made it possible to measure the mass of the planet with a precision of over one-tenth of the mass of Earth.

Proxima b is about 20 times closer to its star than the Earth is to the Sun, it receives comparable energy, so that its surface temperature could mean that water (if there is any) is in liquid form in places and might, therefore, harbor life.

Having said that, although Proxima b is an ideal candidate for biomarker research, there is still a long way to go before we can suggest that life has been able to develop on its surface. In fact, the Proxima star is an active red dwarf that bombards its planet with X rays, receiving about 400 times more than the Earth.

Researchers confirmed the presence of the Earth-sized exoplanet Proxima b using independent measurements obtained with the new ESPRESSO spectrograph, and refined the planetary parameters taking advantage of its improved precision.

The ESPRESSO data on its own shows Proxima b at a period of 11.218 ± 0.029 days, with a minimum mass of 1.29 ± 0.13 M⊕. In the combined dataset we measure a period of 11.18427 ± 0.00070 days with a minimum mass of 1.173 ± 0.086 M⊕. We get a clear measurement of the stellar rotation period (87 ± 12 d) and its induced RV signal, but no evidence of stellar activity as a potential cause for the 11.2 days signal. We find some evidence for the presence of a second short-period signal, at 5.15 days with a semi-amplitude of only 40 cm·s
−1. If caused by a planetary companion, it would correspond to a minimum mass of 0.29 ± 0.08 M⊕

The extended spectral range of ESPRESSO with respect to HARPS, combined with the collecting power of the VLT, allows us to split the spectrum into different wavelength bins to create independent RV series, while maintaining a good photon noise level in each bin. We find that we can measure the decline of a low-amplitude activity signal towards redder wavelengths, as would be expected for spot-induced variations. The planetary signal on the other hand shows a constant velocity amplitude across the full wavelength range, as is also expected for Keplerian signals. We define a chromatic RV, based on the difference between the red and blue velocities, which seems to efficiently track the activity variations of Proxima. Using the time series of the FWHM of the CCF and its gradient, we are able to model the stellar activity in a similar way to the F/F’ method (Aigrain et al. 2012), obtaining good results when detrending the data from activity to recover the planetary signal.

SOURCES- Arxiv, Université de Genève.
Written By Brian Wang,

17 thoughts on “Precise Measurements of Nearest Earth-Sized Exoplanet”

  1. Any planet in the habitable zone would be a tidally locked planet so the rear would not have any x-ray exposure and the twilight area would have greatly reduced x-ray exposure.

  2. How much radiation would the earth experience if it did not have a magnetic field? 
    If there is a companion ( it would correspond to a minimum mass of 0.29 ± 0.08 M⊕ so a relatively large moon ) could that be an indicator of a molten core, and a magnetic field? Just asking ?

  3. The Fermi paradox is a pardox precicely because it’s easy to colonize the galaxy on cosmological timescales. (Technically, it’s not even about colonization, but the colonization argument makes it even more of a paradox.)

    Even if I’m wrong about this particular mode of waiting for closest approach (which I may be, since the neighboring stars also orbit the galaxy, at a similar speed), consider:

    The Milky Way is 100-200 kly across. At just 0.1c, it would only take 1-2 million years to cross. Add 50K stops in each direction (one every 2-4 ly), to build enough infrastructure at each star to send the next set of ships. Say 1000 years per stop – that should be plenty. Then it’s still only 50 million years. Much less than my estimate above.

    And keep in mind that you’re not restrained to a single ship and a single direction per star. A 1000 year pit stop is enough to send ships to each and every neighbor, in all directions.

  4. It’s not about worrying. I find it fun thinking about cosmological timeframes and scales, and what the distant future may look like.

    PS: If age reversal tech plays out, I intend to still be alive by then. I’m still young enough that age reversal could happen soon enough for me.

  5. There are two paths: The first is to evolve into gods and stop caring about the rest of the universe. The other is suicide. Both means that a technological civilization like ours have a very brief existence compare to the life of the universe. It means two of them being in existence close enough to communicate at the same time is nil.

  6. Probability that the initial intelligent beings will be stupid enough to eat of the forbidden fruit of the tree of knowledge and be kicked out of paradise: 1E-42 (I mean, how stupid would they have to be? They only had one job…)
    Probability that they won’t invent sugary carbonated beverages and hence doom their civilization: 0.01%

  7. > I think Sol and Proxima won’t be neighbors for very long anyway, due to their motions through the galaxy.

    This brings to mind an interesting slow interstellar expansion model. As a civilization’s star moves through the galaxy, wait until closest approach to each new stellar neighbor, and hop to that neighbor when it’s easiest. Then repeat the same from there. As each star moves through the galaxy, it will approach multiple neighbors, which in turn will approach other neighbors.

    The Sun completes an orbit in ~200M years. Closest approaches are ~10-100K years apart, I think. So ~10K approaches per orbit. Probably mostly the same stars every orbit, but those stars will, in turn, encounter other stars.

    If on average, about half of the approaches take the colonists a few lightyears inward (and the other half a few ly outward), it would take ~20K hops or roughly two orbits to span the galactic radius. IOW, about 400 million years to colonize the galaxy. Maybe closer to 1 billion years, if I’m overestimating the number of encounters per orbit. (May also be less – the number of stars suggests there should be a lot more approaches per orbit.)

  8. At 1/8 Sol mass, it’s expected to be stable for trillions of years. Also, red dwarves aren’t a late stage. They’re just small stars that are born that way. You may be confusing with white dwarves.

    edit: OTOH, even though the star should be stable for trillions of years, the planetary orbit probably won’t be. But far future tech may allow us to stabilize it. The bigger issue are cosmic events like the upcoming collision with Andromeda in a few billion years, which may drastically change the stellar orbits, or even throw Sol or Proxima out of the galaxy. For that matter, I think Sol and Proxima won’t be neighbors for very long anyway, due to their motions through the galaxy.

    One final thought: Alpha Centaury A and B are Sun-like. In a few billion years, they’ll become red giants, and then white dwarves. Those transitions of shedding their outer layers to become white dwarves would likely cause some significant disturbance at Proxima.

  9. Remarkable that we may have a viable planet for colonization in “our back-yard”. A plus is that the star is already in the red-dwarf state, which means that it will be stable for several billion years.

  10. Planets are the leftovers of star formation, so yeah, nearly 100%. And now we know liquid water exists in a huge swath of planetary conditions, as long as it is cold enough to be liquid and not exposed to space, thus a 500% seems fair.
    I think the problem is at the right side of Drake’s equation. In particular, the likelihood of abiogenesis on any given planet.

  11. Really makes you think, doesn’t it? I recall learning about the Drake equation for the first time and being endlessly fascinated. I still am, and I’m doubly so, considering the advancements in taking measurements of exoplanets.

  12. I remember the days when Carl Sagan would be writing out the Drake equation on TV, and then just guessing number like
    % of stars that have planets? Maybe 1%
    % of stars with planets that might have liquid water? Maybe 1%

    These days we can start to measure the first few terms, and the numbers are a lot more like 100% and 500% (well in our Solar system we’ve got fair evidence for liquid water on Earth (pretty sure about that one) Mars (underground), and several of the larger moons, maybe even Pluto.

  13. I recommend that we create a secret astronaut core of tardigrades. These we can send to Proxima at relativistic speeds. It’s time to start playing the long game. Tardigrade and algae

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