While exoplanets these days are a common discovery, when the first ones were discovered in 1992 they challenged our theories because they were found orbiting a pulsar, the leftover star of a supernova, and not a star like our own Sun. Could they have survived the stellar destruction? Did they form after the explosion? Now, after 25 years, astronomers may finally have some clues.
The new research, published in Monthly Notices of the Royal Astronomical Society, has identified a pulsar, Geminga, that is accumulating material as it moves through the Milky Way. According to the researchers’ calculations, there might be just enough material to form some Earth-size planets around this object, potentially ending the mystery.
“We started looking for the raw materials soon after the pulsar planets were announced," co-author Dr Jane Greaves, of the University of Cardiff, said in a statement. "We had one target, the Geminga pulsar located 800 light-years away in the constellation of Gemini. Astronomers thought they’d found a planet there in 1997, but later discounted it because of glitches in the timing. So it was much later when I went through our sparse data and tried to make an image.”
To see what was going on, the researchers had to use telescopes able to detect objects much colder than stars. They used the James Clerk Maxwell Telescope and conducted several observations with different instruments to make sure that the detections were genuine and not a trick of the light.
The signal observed appears to be genuine and researchers have estimated that the “interstellar grit” captured by the star is equivalent to a few times the mass of the Earth.
“This seems to be like a bow-wave – Geminga is moving incredibly fast through our Galaxy, much faster than the speed of sound in interstellar gas. We think material gets caught up in the bow-wave, and then some solid particles drift in towards the pulsar,” Greaves added.
Greaves, along with co-author Wayne Holland of the UK Astronomy Technology Centre in Edinburgh, is looking into a follow-up study with the Atacama Large Millimeter Array (ALMA), to confirm that the blob of material seen truly belongs to the pulsar. If ALMA confirms the detection, the researchers would like to look at other young pulsars that might be beginning to form planets.
The discovery of the planets around the pulsar PSR B1257+12 back in 1992 suggested that planets might form after a star dies, and this research is an interesting development about a new planetary birth after an original star system is gone.
The research is being presented by Dr Greaves at the National Astronomy Meeting, at the University of Hull, UK, this week.