2019-06-01_All_About_Space

Earth is unclear,” explains Veras. “The asteroid belt

will likely be destroyed by rotational spin-up due to

theSun'sincreasedluminosityonitsgiantbranch

stellar evolutionary phase.”

Afterwards the outer layer will be expelled as a

beautiful planetary nebula What’s left is a white

nal mass.

me the host

ytherehas

,butthere

efoundin

astronomers

ystem and

radiation.

have a

can also be

white dwarfs

ttering

oviding

owever,

dwarf PG

estrong

net formed

dgives

low that

rwehave

dwarfs with

consensus

comes

ding the

ose cases

ould show

signatures in its spectra from accreting material

from the circumstellar disc,” Dr Siyi Xu, an assistant

astronomer at the Gemini Observatory, Hawaii, and

amemberofthisresearchteam,tellsAll About

Space.“PG0010+280istheonlyoutlierwitha

strong infrared excess but no pollution. That is

why we speculated in our 2015 paper that another

possibility is that the infrared excess comes from a

rejuvenated planet – a planet that accreted a lot of

material during the red giant stage of the star and it

is hot and young again.

“Since 2015 there have been a few more

discoveriesofwhitedwarfswithinfraredexcesses,

but they are mostly polluted. There have not been

new discoveries of PG 0010+280-like objects.”

Similartopulsarplanets,thereisthepossibilitythat

a second generation of phantom worlds could form

from the death of their host star.

There are also the stars that don’t quite make it.

There are stars that don’t envelop enough material

during formation to reach the heights of the Sun,

and these are called red dwarf stars. These stars are

roughlybetween7.5and50percentthemassof

ourSunandonlyburntotemperaturesofaround

3,500 degrees Celsius (6,380 degrees Fahrenheit),

which is only roughly 60 per cent of the Sun’s

effective temperature.

Thesecoolerstarsaremuchmoreabundant

in Earth’s vicinity, with scientists predicting 20

out of 30 stars nearest to Earth are red dwarfs.

As it happens, the nearest star to Earth, Proxima

Centauri,locatedjustfourlightyearsaway,isa

M-type red dwarf star with its own Earth-like planet

Timeline

The hunt for

potentially

habitable planets

“ A type of dead star which did experience a

supernova is called a pulsar, and a total of four

planets are known to orbit pulsars” Dr Dimitri Veras

PSR B1257+12 c and

d (Poltergeist

and Phobetor)

Discovered

January 1992

Type of host star

Pulsar

Distance from Earth

2,300 light years

These were the first two

exoplanets ever discovered.

Gliese 876 b

Discovered

June 1998

Type of host star

M-type red dwarf

Distance from Earth

15 light years

This was the first exoplanet

discovered around a red

dwarf star.

Iota Draconis b

Discovered

January 2002

Type of host star

K-type giant star

Distance from Earth

Iota Draconis b was the

first planet discovered

around a giant star,

providing evidence for

how

extre

Prox

Disc

Augu

Ty p e

M-ty

Dista

This

exop

Syste

TRA

f, g

Disc

Febr

Ty p e

M-ty

Dista

Astro

they

pote

exop

dwa

Above:

The evolution

of a star

depends upon

the amount of

mass accreted

beautiful planetary nebula.What s left is

dwarfstar that is 54 per cent ofits origin

Thisdenseleftovercorecouldalsobecom

star of aplanetarysystem. Unfortunately

been no definitive system confirmed yet

has been extremely compellingevidence

attemptingto form one.

For instance, in June 2015agroupofa

used Spitzer to observe a white dwarf sy

found there to be excessive infraredr

Itisknownthatwhitedwarfsh

circumstellar disc – whichc

referred to as ‘polluted’w

–that couldwellbe sca

the stars' light and pro

this infrared boost. Ho

in the case ofwhited

0010+280, there is th

possibility that a plan

from the pollution and

out thefresh infraredg

newplanets emit. “So far

detected about 4 0 whited

infraredexcesses,andthe

is that the infrared excess

from dust discs surround

whitedwarfs.Inalltho

the white dwarf wo

g

planets survive

emeconditions.

ximaCentaurib

overed

ust 2016

eofhost star

ype red dwarf

ancefromEarth

istheclosest

planet to our Solar

emeverdiscovered.

APPIST-1b,c,d, e,

andh

overed

ruary 2017

eofhost star

ype red dwarf

ancefromEarth

onomersannounced

yhadfound seven

entiallyhabitable

planets orbiting a red

rfstar.

duringits

formation

Below:

Xustates

thatthere

isachance

ahabitable

planet could

exist around

awhite

dwarf

Phantom worlds