Astronomers detected the short-lived dimming of X-rays from a system where a massive star is in orbit around a neutron star or black hole (revealed in the artists illustration). This dimming is interpreted as being a world that passed in front of an X-ray source around the neutron star or black hole.
Using ESAs XMM-Newton and NASAs Chandra X-ray area telescopes, astronomers have actually made an essential action in the mission to find a planet beyond the Milky Way.
Spotting a planet in another galaxy is hard, and even though astronomers understand that they must exist, no planetary systems outside of the Milky Way have actually been verified so far. Due to the fact that the light from another galaxy is loaded into a tiny location on the sky, it is very hard for telescopes to differentiate one star from another, let alone a planet orbiting around them. And the usual techniques to discover exoplanets in our galaxy do not work also for worlds beyond it.
This image reveals the Whirlpool Galaxy (M51) as seen at X-ray wavelengths by ESAs XMM-Newton X-ray Observatory. Credit: ESA
This is different when studying X-rays, instead of noticeable light, in a galaxy. An X-ray telescope like ESAs XMM can more quickly distinguish in between items when observing a galaxy due to the fact that there are less things that shine intense in X-ray light. Those things are for that reason simpler to determine and study, and it may be possible to discover a world around them.
Recommendation: “A possible world candidate in an external galaxy discovered through X-ray transit” by Rosanne Di Stefano, Julia Berndtsson, Ryan Urquhart, Roberto Soria, Vinay L. Kashyap, Theron W. Carmichael and Nia Imara, 25 October 2021, Nature Astronomy.DOI: 10.1038/ s41550-021-01495-wPDF.
” X-ray binaries may be ideal locations to look for planets, because, although they are a million times brighter than our Sun, the X-rays come from a really small area. The source that we studied is smaller sized than Jupiter, so a transiting world might completely block the light from the X-ray binary,” discusses Rosanne Di Stefano from the Center for Astrophysics, Harvard & & Smithsonian in the United States, and first author of a brand-new study released in Nature Astronomy today.
A composite picture of M51 with X-rays from Chandra and optical light from NASAs Hubble Space Telescope consists of a box that marks the location of the possible world prospect. Credit: X-ray: NASA/CXC/SAO/ R. DiStefano, et al.; Optical: NASA/ESA/STScI/ Grendler.
Rosanne and associates browsed in Chandra and XMM-Newton data of 3 galaxies for such X-ray transits, dips in the light that might be explained by worlds. And they discovered an extremely unique signal in the Whirlpool Galaxy (M51) that they decided to study in more information. The dip happened in X-ray binary M51-ULS-1 and completely obstructed the signal for a couple of hours, prior to it came back again.
Now the video game of thoroughly crossing off possible explanations started, before the scientists could even think about the option of an extragalactic planet. “We first needed to make sure that the signal was not brought on by anything else,” states Rosanne, whose group argues against a variety of possibilities in their new publication. “We did this by an in-depth analysis of the X-ray dip in the Chandra information, evaluating other dips and signals in the XMM data, and also modeling dips triggered by other possible occasions, consisting of a world.”.
Infographic: A planet in another galaxy. Credit: ESA.
Could the X-ray dip be brought on by small stars like a brown or red dwarf? No, they argue, the system is too young for that, and the transiting things too big.
Could it be a cloud of gas and dust? Not likely, the team says, because the dip suggests a transiting object with a well-defined surface area, which would not be the very same for a passing cloud. Even if the world had an environment, it would still have a more well-defined surface area than a cloud.
Could the dip be described by variations in brightness of the source itself? The paper authors are positive that this is not the case, since although the light from the source entirely vanished for a few hours before it came back, the temperature level and light colors stayed the same.
The group also compared the dip to another obstruction of the light caused by the donor star death in front of the compact star. This was partially observed by XMM-Newton and caused a much longer black-out, which was various from the dip caused by a possible world.
” We did computer system simulations to see whether the dip has the qualities of a world transiting, and we find that it fits completely. We are pretty confident that this is nothing else and that we have actually found our first world candidate outside of the Milky Way,” adds Rosanne.
The group likewise hypothesizes about the characteristics of the world based on their observations: it would be the size of Saturn, orbiting the binary star system from 10s of times the Earth-Sun range. It would make one full orbit approximately every 70 years, and be bombarded with extreme quantities of radiation, making it uninhabitable by life as we understand it on Earth.
This long orbit of the world candidate is also a limitation for the research study, due to the fact that the event cant be duplicated any time quickly. Thats why the team stays cautious to say that they found a possible planet prospect, for which the more comprehensive neighborhood may find other explanations, although they have not been discovered after mindful research study by the team. “We can just say with self-confidence that it doesnt fit any of our other explanations,” Rosanne clarifies.
This would likewise be the very first time that a world is found orbiting an X-ray binary. The presence of those worlds is constant with the fact that worlds are found around pulsars (quickly rotating neutron stars), and some of these pulsars have been part of an X-ray binary in the past.
” The very first verified world beyond our Solar System was found around a pulsar, a things typically observed in X-rays. I am thrilled that X-rays now likewise play important step in the search for planets beyond the border of our galaxy,” states Norbert Schartel, XMM-Newton Project Scientist for ESA.
” Now that we have this new technique for finding possible world prospects in other galaxies, our hope is that by looking at all the available X-ray information in the archives, we find lots of more of those. In the future we might even have the ability to verify their presence,” states Rosanne.
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The infalling material is sped up by the intense gravitational field of the neutron star or black hole and heated to millions of degrees, producing a lot of intense X-rays. Astronomers expect that theoretically, worlds passing in front of (transiting) such a source would block these X-rays, causing a dip in the observed X-ray light curve.
Since there are less items that shine brilliant in X-ray light, an X-ray telescope like ESAs XMM can more quickly distinguish in between objects when observing a galaxy. Astronomers anticipate that in theory, worlds passing in front of (transiting) such a source would block these X-rays, causing a dip in the observed X-ray light curve.
Rosanne and coworkers searched in Chandra and XMM-Newton data of three galaxies for such X-ray transits, dips in the light that might be discussed by planets. “We did this by a thorough analysis of the X-ray dip in the Chandra information, examining other dips and signals in the XMM information, and also modeling dips triggered by other possible events, including a world.”.
The presence of those planets is consistent with the fact that worlds are found around pulsars (quickly rotating neutron stars), and some of these pulsars have actually been part of an X-ray binary in the past.