2019-06-01_All_About_Space

“Pulsars emit a tremendous amount of

high-energyradiation,yetwithinthis

environment we have a disc” Deepto Chakrabarty

These stars are tremendously dense; if you were

to somehow get a teaspoon of the stuff it would

weigh a billion tons. Because these stars are so

dense they are very hot and release a lot of radiation

in gamma rays, X-rays, ultraviolet rays and so on.

This is not healthy for a planet. If the Earth was

constantly bombarded by these levels of radiation

there is no way life would survive in any form.

A study released by Dr Alessandro Patruno from

Leiden University, The Netherlands, and Dr Mihkel

Kama of the University of Cambridge, UK, stated

that planets could be habitable around pulsars.

In order to make this claim these astronomers

deduced the theoretical ‘habitable zone’ around

a pulsar – the distance a planet would have to be

from the pulsar in order for water to exist as a

liquid. These results highlighted the specific criteria

a planet must meet in order to survive here: a

maximum distance from the pulsar than the Earth

is to the Sun, the planet must be a super-Earth – a

mass between one- and ten-times our Earth – and

the atmosphere must be as thick as the conditions

on the deepest ocean f loors. If the atmosphere was

relatively thin then the pulsar winds would strip it

away within a thousand years – which is no time for

life to evolve.

The origins of these planets are unknown, but

there are two likely options. The first is that the

planet was formed before the

supernova from primordial

debris around the same

time as the birth of the star,

and was far away enough to

survive the supernova. The

other side of the coin suggests

that these planets formed from

debris surrounding the pulsar, much

like a second-generation planet.

In 2006 a team of researchers used NASA’s

Spitzer Space Telescope to uncover new evidence

that suggests second-generation planets were

formed around a pulsar called 4U 0142+61, 13,000

light years away. "We're amazed that the planet-

formation process seems to be so universal," says

Deepto Chakrabarty of the Massachusetts Institute

of Technology, principal investigator of the research.

"Pulsars emit a tremendous amount of high-energy

radiation, yet within this harsh environment we

have a disc that looks a lot like those around young

stars where planets are [being born].”

Now what if a planet was to escape before a

pulsar could pepper it with harmful radiation?

This is hypothetically possible, as a planet around

a red supergiant could be expelled in the following

supernova and cast away as a ‘rogue planet’. In

fact, Veras even claims that “there could be up

to one giant rogue planet for

every star”.

“This possibility has not

been considered in depth in

the astronomical literature,

probably because supernovae

occurrarely–aboutonceper

century in our galaxy,” says Veras.

This is unfortunate as this would be

quite the revelation in terms of planets

existing in unlikely situations. To think that there

could potentially be thousands or even millions

and billions of planets hidden in the cold, dark

emptiness of space that are undetectable without a

star’s light is a intriguing thought.

Once ejected these rogue planets don’t have

many options except to wonder through space

alone. They bring a whole different meaning to the

term ‘phantom’ as they ghost through the universe

until they find a new home. “Simulations have

shown that planetary systems can capture rogue

planets, although the process is rare and depends

on several factors,” says Veras. This could mean

that planets around dead stars could be imposters

sent from another system, but then again there

are so many unknown factors to take into account

in this scenario, with such little data it would be

outlandish to make any definitive claims.

When looking at dead stars the mind can’t help

but relate back home, bringing thoughts of what

will happen to our own Sun at the end of its life.

When the Sun runs low on hydrogen to burn

its outer layers will swell. “The Sun will engulf

Mercury and Venus. Mars, Jupiter, Saturn, Uranus

and Neptune will all survive, and the fate of the

From above,

clockwise:

‘Rejuvenated

planets’ would

theoretically

emit a

youthful

glow of

infrared light

Eventually the

Sun will form

a planetary

nebula –

hopefully

this will look

beautiful

Ve ra s st ate s

that rogue

planets could

be captured

by other

planetary

systems

NASA’s

Spitzer Space

Telescope

has played an

important role

in analysing

exoplanets

over the years

Phantom worlds