Directly viewing a planet outside the Solar System is very rare. Almost all those we have found have been through detecting the planet's effects on its star, rather than actually seeing its light. Nevertheless, the planet 2M0437b has been photographed for three years, and it's probably the youngest planet we have ever found, brown dwarfs aside. Its discovery could pave the way for even more exciting findings.
Planets, school science classes inform us, don't shine with their own light. This makes them exceptionally hard to see when orbiting other stars – not only are they intrinsically very faint, but what light they do reflect is lost in the dazzle of their parental star.
The exception, however, is very young planets, which are still so hot they may glow red, and be even brighter in the infrared part of the spectrum. A paper in Monthly Notices of the Royal Astronomical Society (preprint on ArXiv.org) reports 2M0437b is among the lightest, and probably youngest examples we know.
In addition to still having most of its heat of formation, 2M0437b currently sits around 100 AU (15 billion kilometers (9.32 billion miles) or 100 times the Earth-Sun distance) from its parental star 2MO437.
At such a distance 2M0437b gets almost no light from 2M0437. In a few million years that will make its detection even harder – even people on another planet in the same star system might have trouble noticing something so faint. For the moment, however, it keeps the planet's glow well clear of the light of the star so they can be distinguished. It also helps that 2M0437 is 15-18 percent of the Sun's mass, and therefore hundreds of times fainter, while 2M0437b is thought to have 3-5 times Jupiter's mass. If they were closer together physically, or further apart in masses, the images would be impossible.
2M0437b was first observed using the Subaru Telescope on Maunakea in 2018. However, given the distance between star and planet, the finders wanted to make sure they really were associated, rather than being light years apart but in the same direction from our perspective.
Confirmation 2M0437b is indeed moving across the sky with its parental star, as both circle the galaxy together, is one of the key features of the paper, along with some context about the two. Both lie in the Taurus Cloud, a stellar nursery 430 light-years away where new stars, and their planets, are being formed.
"Two of the world's largest telescopes, adaptive optics technology and Maunakea's clear skies were all needed to make this discovery," co-author Dr Michael Liu of the University of Hawaii said in a statement.
The authors noted the estimated age of 2M0437 at 2.5 million years old is similar to the Hawaiian islands from which it was discovered, and the planet's 1,100-1,200 ºC (2,012-2,192 ºF) temperature matches that of the lava released by Kīlauea Volcano.
Nevertheless, future knowledge about 2M0437b is likely to come not from Hawaii, but space. There will be a near-endless demand on the JWST's time when it launches later this year (hopefully), but observing newly formed planets, which shine brightest in the near-infrared, is a task to which it is ideally suited. The JWST; “could identify gases in its atmosphere and reveal whether the planet has a moon-forming disk," lead author Professor Eric Gaidos of the University of Hawaii said. Such observations may explain how such a small, young star could have such a large planet, in violation of existing models.