Home

Astronomy & Space

Astronomy

November 7, 2018

November 7, 2018 by Paul M. Sutter, Universe Today

Artist’s concept of the Wide-field Infrared Survey Explorer as it orbits the Earth. Credit: NASA/JPL
Our universe is capable of some truly frightening scenarios, and in this case we have an apparent tragedy: two stars, lifelong companions, decide to move away from the Milky Way galaxy together. But after millions of years of adventure into intergalactic space, one star murders and consumes the other. It now continues its journey through the universe alone, much brighter than before, surrounded by a shell of leftover remnants.

At least, we think. All we have to go on right now is a crime scene.
Let’s investigate.
The Case of the Too-Young Star
The star’s name is unassuming enough, if a bit obscure: CPD 64°2731. And at first glance it’s not particularly strange, with a mass somewhere around forty times that of the sun. But its circumstances are downright bizarre. It’s moving incredibly fast, topping out at a blazing 160 kilometers per second. It’s well outside the Milky Way galaxy, positioned about 25,000 lightyears away from us and about 2,000 lightyears above the galactic disk. And it’s spinning insanely rapidly, upwards of 300 kilometers per second (compared to the relatively sedate speed of 2 kilometers per second for the sun).
It gets worse. Recent observations by a team using the Wide-field Infrared Survey Explorer paint the portrait of a thin, horseshoe-shaped shell of gas and dust surrounding this radical star, with the shell itself lit by the intense radiation blasting from the stellar surface.
And here’s the strangest part. Assuming the star was born somewhere within the disk of the Milky Way (a pretty safe bet), it would’ve taken about six million years to reach its current position outside the galaxy. But a star with that size, mass, and temperature should only be about three million years old.

The bow shock of Zeta Ophiuchi, another runaway star observed by Spitzer. Credit: NASA/JPL-Caltech
Something doesn’t add up.
Kicked out of Town
Something chased CPD 64°2731 out of the galaxy, and it was probably its closest friends and neighbors. Stars tend to be born in clumps and clusters, from a few dozen to a few hundred popping out of the same molecular cloud. In most cases, those stars will just gently drift further apart as an open cluster, becoming more independent as they age.
But chance encounters can spin things around from that serene expansion. When three or more stars of comparable mass get close to each other, their gravitational interactions become incredibly unstable. In some cases, they just slightly alter their trajectory but otherwise remain unaffected. In others, they capture each other and form long-term orbits. But every once in awhile the energies add up in exactly the wrong way, sending one or more stars completely flying away at ludicrous speeds.

This is how so-called “runaway stars” get their boosts, and once they get going there’s nothing holding them back. In many cases, they set themselves up on an escape trajectory from the galaxy altogether, as in the case of our enigmatic friend, CPD 64°2731.
And in situations where stars are born close enough together to become runaways, many of those stars happen to be binary systems.
Ah, a clue.

This artist’s impression shows VFTS 352 — the hottest and most massive double star system to date where the two components are in contact and sharing material. The two stars in this extreme system lie about 160 000 light-years from Earth in the Large Magellanic Cloud. This intriguing system could be heading for a dramatic end, either with the formation of a single giant star or as a future binary black hole. Credit: ESO/L. Calçada
The Companion-Killer
Sometimes stars eat their companions. If one of the pair gets too close, the more massive one will suck down gas from its neighboring atmosphere like a stellar vampire. And as you might imagine, once this scenario starts to play out it usually doesn’t end well – stars don’t take very kindly to destabilizing their atmospheres. Flares, eruptions, and temper-tantrums ensue.
In the worst case scenarios, the pair becomes so destabilized that their orbits shrink and shrink, eventually merging the stars together in a horrific – and fatal – embrace. Needless to say, this process releases a tremendous amount of energy, capable of blowing multiple suns-worth of material out into the surrounding space as a gigantic nebula.
The newly-combined star (if it survives at all), completely changes character. It will now be spinning rapidly from the absorption of all that juicy angular momentum from its once-orbiting companion. It also now has a fresh supply of raw fuel, thanks to its unlucky host, and a big boost in mass, increasing its fusion rate and radiation output. And that pumped-up radiation output lights up the surrounding nebula like a neon sign.
The end result of such a fantastic collision? A single giant star, spinning fast, reset and reborn in youth, surrounded by the remnants of the violent encounter with its twin.
And in this case, as best surmised in a recent paper, a treacherous star high-tailing it out of its home galaxy, free but forever a fugitive.

Explore further:
Fastest stars in the Milky Way are ‘runaways’ from another galaxy

More information:
V. V. Gvaramadze et al. CPD-64 2731: a massive spun-up and rejuvenated high-velocity runaway star. arXiv:1810.12916 [astro-ph.SR]. arxiv.org/abs/1810.12916

Related Stories

Fastest stars in the Milky Way are ‘runaways’ from another galaxy

July 4, 2017

A group of astronomers have shown that the fastest-moving stars in our galaxy – which are travelling so fast that they can escape the Milky Way – are in fact runaways from a much smaller galaxy in orbit around our own.

Image: Hubble’s compact blue dwarf galaxy UGC 11411

June 22, 2015

This NASA/ESA Hubble Space Telescope image shows a galaxy known as UGC 11411. It is a galaxy type known as an irregular blue compact dwarf (BCD) galaxy.

How do stars go rogue?

August 25, 2015

Rogue stars are moving so quickly they’re leaving the Milky Way, and never coming back. How in the universe could this happen?

Image: Hubble checks out a home for old stars

December 21, 2015

This image, taken with the Wide Field Planetary Camera 2 on board the NASA/ESA Hubble Space Telescope, shows the globular cluster Terzan 1. Lying around 20,000 light-years from us in the constellation of Scorpius (The Scorpion), …

Image: Hubble gazes at stars of the Large Magellanic Cloud

June 24, 2016

This colorful and star-studded view of the Milky Way galaxy was captured when the NASA/ESA Hubble Space Telescope pointed its cameras towards the constellation of Sagittarius (The Archer). Blue stars can be seen scattered …

What are neutron stars?

October 16, 2017

Thrilled physicists and astronomers announced Monday the first-ever observation of the merger of two neutron stars, one of the most spectacularly violent phenomena in the Universe.

Recommended for you

Aluminium oxide found in an ultra-hot Jupiter

November 7, 2018

An international team led by the astrophysicist Carolina von Essen, has used the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC) to study the chemical composition of a planet whose equilibrium temperature is around …

Scientists push back against Harvard ‘alien spacecraft’ theory

November 7, 2018

A scientific paper led by two researchers at Harvard University made a splash this week by claiming that a cigar-shaped rock zooming through our solar system may have been sent by aliens.

Cosmic collisions: SOFIA unravels the mysterious formation of star clusters

November 7, 2018

The sun, like all stars, was born in a giant cold cloud of molecular gas and dust. It may have had dozens or even hundreds of stellar siblings – a star cluster – but these early companions are now scattered throughout …

NASA’s Parker spacecraft makes first close approach to sun

November 6, 2018

A NASA spacecraft has made its first close approach to the sun, just 2 1/2 months after liftoff.

Ultra-hot gas around remnants of sun-like stars

November 6, 2018

Solving a decades-old mystery, an international team of astronomers have discovered an extremely hot magnetosphere around a white dwarf, a remnant of a star like our Sun. The work was led by Dr. Nicole Reindl, Research Fellow …

Astronomers discover new luminous high-redshift quasar

November 6, 2018

An international team of astronomers has detected a new luminous quasar at a redshift of 7.02. The newly found quasi-stellar object (QSO), designated DELS J003836.10–152723.6, is the most luminous quasar known at a redshift …

0 comments

Original Article can be found by clicking here