May 7, 2019

We wouldn't know it if we found another Earth

Illustration: Rebecca Zisser/Axios

Technology designed to hunt for alien planets has progressed in the 27 years since we found the first planet outside of our solar system. However, researchers still can't tell with confidence whether any newfound worlds can sustain life — and might not be able to for years.

The big picture: Scientists have detected almost 4,000 planets circling stars light-years away from our own solar system.

  • These exoplanets — worlds outside of our solar system — are typically found when they pass in front of their star, allowing spacecraft like NASA's TESS to detect minuscule dips in light that happen during those transits.
  • Other telescopes have detected exoplanets by measuring the small wobbles of a star created by a planet's gravity.
  • Most exoplanets we've identified are more massive than Earth, and many aren't orbiting stars like our sun.
  • That leaves about 20 planets so far that are thought to be small enough and the right distance from their stars to be potentially habitable.

Between the lines: Using current methods, scientists can track a planet's orbit and even get a decent measurement of its mass, but beyond that, it's hard to know exactly what's happening on a small planet like our own.

  • It's not enough to know if an exoplanet is in its host star's habitable zone — the orbit where liquid water could, in theory, be sustained on the surface.
  • Scientists still need information about a planet's composition, atmosphere and geology to make an educated guess at habitability.
  • Even an exoplanet's core would have bearing on its habitability in that a liquid iron core like Earth's could help produce magnetic fields that would shield a planet's surface from incoming radiation.

Some of the most convincing evidence that a planet is Earth-like may come if scientists can detect atmospheric water vapor.

  • However, today's most powerful telescopes aren't sensitive enough to parse out the composition of a relatively small exoplanet's atmosphere.
  • "I absolutely believe there's life somewhere else. I just can't point to the planet yet and tell you which one it is," says NASA exoplanet scientist Steve Howell.

What's next? Scientists need new tools in order to know if they've found a world truly like our own.

  • NASA's James Webb Space Telescope (JWST), expected to launch in 2021, might be able to investigate the atmospheres of small planets, though it's likely best suited for dissecting the atmospheres of larger, gaseous planets.

It will probably take until the generation of telescopes after JWST to enable scientists to find a truly habitable exoplanet.

  • The Large UV/Optical/IR Surveyor is a NASA concept for a space-based observatory that could directly image a small planet's atmosphere for the first time.

While the public and other researchers might be impatient to find another Earth, exoplanet scientists are in it for the long haul.

  • "Everyone wants to meet the little, green humanoids," MIT exoplanet scientist Sara Seager told Axios. "We're not doing that, but we'll find enough to believe and then to keep the search going. It's going to be, like, a 100-year thing, and we're only 20, 25 years into it."

Go deeper

Italy reports lowest number of new coronavirus cases since February

Italy’s aerobatic team Frecce Tricolori fly over Milan in Duomo Square on May 25. Photo: Francesco Prandoni/Getty Images

The Italian government reported 300 new cases of coronavirus on Monday, the lowest daily increase since Feb. 29.

Why it matters: Italy, the first country in Europe to implement a nationwide lockdown after emerging as a hotspot in March, appears to have finally weathered its coronavirus outbreak. Italy has reported nearly 33,000 total deaths, the third-highest total behind the U.S. and U.K.

Coronavirus dashboard

Illustration: Aïda Amer/Axios

  1. Global: Total confirmed cases as of 2 p.m. ET: 5,453,784 — Total deaths: 345,886 — Total recoveries — 2,191,310Map.
  2. U.S.: Total confirmed cases as of 2 p.m. ET: 1,651,254 — Total deaths: 97,850 — Total recoveries: 366,736 — Total tested: 14,163,915Map.
  3. World: Top Boris Johnson aide defends himself after allegations he broke U.K. lockdown — WHO suspends trial of hydroxychloroquine over safety concerns.
  4. 2020: Trump threatens to move Republican convention from North Carolina — Joe Biden makes first public appearance in two months.
  5. Public health: Officials are urging Americans to wear masks over Memorial Day.
  6. Economy: White House economic adviser Kevin Hassett says it's possible the unemployment rate could still be in double digits by November's election — Charities refocus their efforts to fill gaps left by government.
  7. What should I do? Hydroxychloroquine questions answeredTraveling, asthma, dishes, disinfectants and being contagiousMasks, lending books and self-isolatingExercise, laundry, what counts as soap — Pets, moving and personal healthAnswers about the virus from Axios expertsWhat to know about social distancingHow to minimize your risk.
  8. Other resources: CDC on how to avoid the virus, what to do if you get it, the right mask to wear.

Subscribe to Mike Allen's Axios AM to follow our coronavirus coverage each morning from your inbox.

Updated 1 hour ago - Politics & Policy

Joe Biden makes first public appearance in over two months

Photo: Oliver Douliery/AFP via Getty Images

Former Vice President Joe Biden made his first in-person appearance in over two months on Monday to honor Memorial Day by laying a wreath at a Delaware veterans park, AP reports.

Why it matters: Biden, the Democratic Party's presumptive nominee, has taken the unprecedented step of campaigning from his home during the coronavirus pandemic, ever since canceling a rally in Cleveland on March 10.