NASA’s planet hunter uncovers Earthsize world in habitable zone
The Transiting Exoplanet Survey Satellite (TESS) has discovered a roughly Earth-size planet in the habitable zone of its host star, the zone of orbital distances where liquid water could be stable on a world’s surface. The newfound exoplanet, known as TOI 700 d, lies just 101.5 light years from Earth, making it a good candidate for follow-up observations by other instruments, scientists added.
TESS found three different planets circling the star TOI 700 – TOI meaning ‘Tess Object of Interest’ – a red dwarf about 40 per cent as massive, 40 per cent as wide and 50 per cent as hot as Earth’s Sun. The innermost world, TOI 700 b, is roughly Earthsized and completes one orbit every ten Earth days. The centre planet, TOI 700 c, is 2.6-times bigger than our planet, meaning it’s likely a gassy ‘subNeptune’, and zips around TOI 700 every 16 days.
TOI 700 d, the outermost known planet in the system, is the really intriguing one. It’s just 20 per cent larger than Earth and completes one orbit every 37 days. The alien world receives 86 per cent of the stellar energy Earth gets from the Sun, putting TOI 700 d in the habitable zone.
All three planets may be tidally locked to TOI
700, always showing it the same face, just as Earth’s Moon only ever shows us its near side. But tidal locking doesn’t necessarily preclude the possibility of life, astronomers say. And there’s more good news regarding TOI 700: “In 11 months of data, we saw no flares from the star, which improves the chances TOI 700 d is habitable and makes it easier to model its atmospheric and surface conditions,” said discovery team leader Emily Gilbert, a graduate student at the University of Chicago.
Scientists hope to pin down TOI 700 d’s mass by measuring how much its gravity tugs the host star. Without knowing the mass, it’s unclear how dense TOI 700 d is – and thus if it’s a rocky world like Earth. In-depth observations of light that has streamed through TOI 700 d’s atmosphere on its way to Earth could tell us a great deal about conditions on the alien world’s surface, which remain a total mystery at the moment.
“Someday, when we have real spectra from
TOI 700 d, we can backtrack, match them to the closest simulated spectrum and then match that to a model,” said Gabrielle Engelmann-Suissa, a Universities Space Research Association visiting research assistant at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It’s exciting because no matter what we find out about the planet, it’s going to look completely different from what we have here on Earth.”
Researchers released simulations of the Large Magellanic Cloud (LMC) – a satellite galaxy of the Milky Way – and found that cosmic rays from a starburst event are starting to rip it apart.
One of the many by-products of starburst violence is the production of cosmic rays, tiny charged particles accelerated to nearly the speed of light. Cosmic rays constantly zip through the cosmos, leaping over billions of light years to wreak havoc wherever they land.
Now much hotter, gas doesn’t seem so interested in staying in the LMC – or, in other words, the gravity of the LMC isn’t strong enough to hold onto its own gas after these rounds of concentrated star formation and supernovae, and so the hot gas tries to leave.
Researchers looked at the simulated behaviour of something called the Magellanic Stream, a trail of hot, thin gas that wraps almost all around the Milky Way, a flow of material ejected from the satellite galaxy hundreds of millions of years ago.
They found a surprise: even though the cosmic rays heated up the gas in the LMC: the gas stayed inside.
The reason for this apparent contradiction is the LMC’s orientation as it falls towards the Milky Way. For the past billion years or so, it’s been heading for us directly, no holds barred and face-on. Because of this orientation, as the LMC swims through the loose halo of gas surrounding the Milky Way, pressure from the gas can keep a lid on things.