Astronomers discover a hypothetical ‘strange star’

Noteworthy is the compact object XMMU J173203.3-344518, with about three-quarters of our sun’s mass packed into a sphere that could fit comfortably inside Manhattan. Even surprising. Maybe it’s weird. But is this strange? A new study by astrophysicists from the University of São Paulo and ABC Federal University in Brazil confirms that this incredibly dense block of stars may indeed be strange, but perhaps not in the way you think.

Last year, researchers at the Institute of Astronomy and Astrophysics at the University of Tübingen in Germany recalculated the distance between us and the tiny corpse of a dead star swirling within the supernova remnant HESS J1731-347. At just 8,150 light-years away, the revised distance was less than the previous estimate of about 10,000 light-years. The new distance required recalculating the properties of the compact object, including its size and mass.

This is where things get a little hectic.

When stars of a given mass run out of fuel enough for their gravity to obliterate daylight, they collapse in a cosmic shock of heat and electromagnetism that blows up some of their outer layers. All that is left is an object so dense that its atoms are pressed against the cheek. Deep within its nucleus, electrons become trapped in their nuclei, causing the protons to lose their charge and turn into neutrons. Congratulations, this is a newborn neutron star.

If there’s enough mass, all that extra gravity overcomes the critical nuclear forces, turning matter into something incredible and creating a black hole instead. However, very little mass and atoms remain friendly neighbors within the so-called white dwarf. The lower mass limit for a neutron star is believed to be more than one solar mass. The lightest ever discovered has just 1.17 solar masses.

With 77 percent of the Sun’s mass, XMMU J173203.3-344518 is not just a record; just confusing. Neutron stars shouldn’t be this small. This means that there may be no neutron stars at all. The researchers left their conclusions to other researchers, assuming it was an object called a strange star, mainly composed of particles known as strange quarks.

Picking up where the last study left off, this new study returned to the extremely small compact object in HESS J1731-347 and took another look at its mass, radius and surface temperature. Comparing their results with strange matter equations and speculative models they created in supernovas, the team agreed that this strange little object still had all the characteristics of a hypothetical strange star.

Quarks are fundamental particles that group into groups of three to form baryons. The two most famous examples of these groups are nuclear particles, protons and neutrons.